CA1117255A - Method for the preparation of implants, and implants - Google Patents
Method for the preparation of implants, and implantsInfo
- Publication number
- CA1117255A CA1117255A CA000319327A CA319327A CA1117255A CA 1117255 A CA1117255 A CA 1117255A CA 000319327 A CA000319327 A CA 000319327A CA 319327 A CA319327 A CA 319327A CA 1117255 A CA1117255 A CA 1117255A
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Abstract
The disclosure describes a method for the preparation of implants from ceramic substances, especially with a porous surface stimulating the ingrowth of bone tissues, by introducing a model of the implant into a high-temperature embedding substance which has been mixed to a paste and leaving it in this until the embedding substance hardens and a negative mold of the implant is produced. After removal of the model the mold is lined via an opening reaching into its interior with a layer of a ceramic substance which should form the outer layer of the implant. The cavity of the mold is subsequently filled completely with dentine or core substances, the opening is then sealed with a high-temp-erature embedding substance, mixed to a paste, the embedding substance is allowed to dry and the whole thing is then heated to the sintering temperature of the ceramic substances used and the ceramic substances fired at this temperature for the usual time. The disclosure also describes an implant of ceramic substances and having a porous outer layer. The porous outer layer consists of a ceramic substance according to the DE-OS 2711 219 with an addition of substances stimulating bone formation and/or bone growth in a quantity of 5 - 70 wt. % relative to the dry content of the ceramic substances, especially tri-calcium phosphate and tertiary calcium phosphate.
Description
The invention re~ates to a method for the preparation of implants~ especially dental implants~ from ceramic substances having in par-ticular a porous surface ~hich stimulates lngrowth of bone tissue.
The present invention ha~ as its object suggestion of a Method for the preparation of implants which is particularly slmple and is easible with conventional equipment available in den-tal laboratories, using conventional techniques and not involving additional expense pertaining to apparatusO This problem ls solved according -to the invention ln that by introducing a model of the implan-t i~to a pa~te-like, high-tempera-ture embedding substc~lce and leaving it in this until the embedding sub~tance harden~ a nega-tive mold of the implant ls produced~ and that after removal of the model -the mold is lined via an opening reaching into its interior ~ith a layer of a cer~c subs-tance which should form the outer layer of the implan-t, that the cavity of the mold is subsequently filled completely with dentine or core substances, that the opening is then sealed with a paste-like, high-temperature embedding substance9 that said embedding substance is allowed to dry and that the whole thing is then heated to the sintering temperature of the ceramic substances used and the ceramic substances fired at this tempera-ture for the usual time, Theequipment available in dental laboratories for the preparation of centrifugal castings suffices for carrying out the method according to the invention;
the embeddlng substance is preferably introduced in-to a muffle or cuvette which is free of scale.
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It is advantageous if the muffle i3 fllled at fir~t to about two thirds with the embedding substance prevlously stirred to a paste 7 the model subsequently pushed into the embedding substance from above and after hardening of same pulled out again ~ and if after filling the negative mold with ceramlc subs-tance the rest of the muffle ia filled up wlth embedding subst~nce~
It has proved f~vourable to prepare the negative mold using a wax model of the implant which is burned out after the embedding substance has hardened. ..
A varicl~t of the method accordlng to the inv~ntion i~ characteriæed in that a shell mold corresponding to the shape of the implant i~ llned vi~ an opening reaching into the interior of said ~hell mold with a layer o~ a ceramic substance which should form the outer layer of the implant 9 that the shell mold ls ~ubsequently filled completely with dentine or core substances, that the opening is then sealed with a paste-like~ high-temperature embedding substance 7 that said embedding substance is allowed to harden and that the whole thing is then heated to the sintering temperature of the ceramic ~ubstances used and the ceramic substances fired at this temperature for the usual time. ~he shell mold cons~sts of a noble metal alloy (pre~erably platinum or a platinum alloy) which i~ not affected by change o~ temperature and which is not destroyed a~ the ~iring temperatures of approx~ 1000 -to 1500~
The negative mold~ or shell mold7 is preferably ~illed by applying the ceramic substance 9 mixed to a paste . . .
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with cocoa-butter or ano-ther conYe~tional pasting agent9 in layersO ~he outermost layer applied to the wall of -the mold, or shell mold~ which on flring provides the desired porosity a is applied to a th1ckness o~ o 9 1 to 5 mm, preferably about o,3 to about 1 mm. It can be fired prior to filling up the rest of the space in the mold wi-th a dentine or core substance~ The imp~nt obtained by the method according to -the inventlon is expedientl~J treated after its removal from the embedding subs-tance with a sandblast blower7 at leas-t in the region to be implan-ted 7 in order to guaran~tee complete opening of the vacuoles; in so doing the area which is no-t to be implanted can, i:E necessary~ be covered~
in particular wi-th a wa~ or a plastic foil. In order to reinforce the interior structure o~ the implant a metal or ceramic insert can be introduced, before covering the opening leading to the interior of the mold with embedding substance which has been mixed to a paste~ into the in-terior of said mold~ this being already covered~ at lea~t at the edge 9 or already par-tly or comple-tely fllled with ceramic substance.
~luminium oxide tubes or pins which protrude above the mold a~d later serve for fixation of the crown or other superstruc-ture are especially suitable for this.
The ceramiC gubsta~ces used for the ou-ter la~er of the implant are characterized by a mixture of a ceramic base substance and fine inor~anic fibers, whose melting temperature is higher than the sintering temperature of -the ceramic base substance. When preparing ceramic substances according to -the invention care ls taken that -the ceramlc base substance, in the molten form that it talces on during sintering, does not dissolve the fikers as suchO
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~y fine fibers in this specification9 fibers or filaments and wires having a diame-ter less than about o~6 mm are understood.
Th~ fibers accoxcling to the inven-tion can be present in the cerclmic base substance matri.x in the form of whiskers~
filameIltg 9 staple fibers~ chopped fibers, threads, chopped strands as well as further processed products such as slubbings~ rovings, net-ting~ matting9 fibrous webs~
bonded fibrous materi.als, felts and woven materials.
Usually~ that is 9 if no extreme reinforcement effect .is required, it suffices to have the fibers in short pieces~
of lengths approximately o,1 ~ 60 mm9 preferably abou-t o,5 - 30 mm, in -the cexamic base substc~nce.
.For the productlon of porous ceramic bodies 7 fibers in pieces of abou-t o,5 - about 3 mm are particularly suitableO An adqua-tely uniform distribution of the fibers in the base subs-tances is generally sufficient to ensure that the cerc~mics manufactured ~rom -the substances have the desired rigidityD This applies especially for the production of porous ceramic bodies having surfaces not prone to rejection by the tissues and ~hich enable adherence and ingrowth of bone tissue~ These porous bodies contain a large number of ve~icular cavities merging par-tly into one another like a spongeA The pores vary in diameter from the ~mallest pore of diameter less than l~m to pores with a diameter of over 500~wm, whereby in one piece of ceramic pores of differan-t sizes are evident. Pores of diameter from about 10 to about 400 ~m are preferred. The average value of the pore diameter should be approximately 100 ~ 200 whilst the quantity of pores havlng a diameter larger than 300 ~ m should not account for more than 10yo~
pre~erably 5%. In the porous boclies the pores take up a volume of about 1o~,h to about 90/0 with respect to the total volume. Propo-rtions of pores from about 20 Vol,%
to about ~o VolOS' are especially sui-ted for use as adhering layer fox -the lngrot!rth o~ tissue~
convcntional orr~anLc fibers pxo~e ~suitable for the production of the sub3tances according to the invention since their melting points are lower than the temperatures necessary for the sintering together of the ceramic base substances~ the terlperatures for the ceramic base substances used lying in a region from abou-t 650-1 900C .
~he composition of -the ceramic base substances u~ed within the ~ramework o~ the invention at hand will be subsequently dealt w:ith in more detail.
In the following a series of ~ibers are indicated~
though not claiming entirety9 which are suitable for the manu~acture of ceramic substclnces as accord~ng to the invention. l`hey are as ~ollows:
Pure quartz fiberS from 99.9~6 silicon dioxlde~ which on account of their high thermal and chemical stability present no pxoblem~c~ when used lor implant~0 Carbon fibers9 which in the purest form are referred to as graphite fibers c~d are relatively economical to manufacture. When using cc~rbon fibers it must be remembered tha-t al&ough they present no physiological problems, the material exhibits a high heat conduction capactiy and a high electricity con~uction capacity.
~he prccessing of carbon fibers should be carried out in a vacuum in order to prevent oxidation, -;
Metal filame~ts~ manufactured by heat-draw~ng with or without sheathing and by pressing out of the melt ~: . . .
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-through narrow nozzle opening3 and su'b~equent solidif.ication3 '' or by the so~called ~a.ylor Proce~s2 Me-tal filaments wlth a diameter equal to or larger than 100 ~n can~ according -to DIN 60001 ~ be referred to clS wires~ ~hen metal :Eilaments or w:Lre~ make up the fiber con-tent Ln the ceramic substances according to the invention and these sub~tances are used for implan-ts 9 care should be ta~en -to use a cerc~mic ba~e substance whlch9 when molten~
wets the met~.l filaments well~ so tha-t after solidification of the ceramic ~ubstance these are~ if po~sible 9 not bare. O-the~ise they could be a-ttacked by the body fluid~ 9 which dissolve the metalcl and could lead to so-called "metallosls" iOe~ poisening b~y metal ions, ~he danger of such a metallosi~ is not great even if the me-tal filaments are not completely covered by -the ceramic bass ~ubstance7 si~ce the fibers account for only a small percentage of t,he total materl.al and are furthermore embedded for the most, part ln the ma-trix o~ -the cerc~mlc base substance. Since however there are o-ther fibers ~^rhere the danger of metallosis can from -the start be excluded, ceramic substance~ containing metal filaments as fiber content are generally not used for the outer layer of prosthetic elements but rather as reinforced core substance~9 these being covered by the overlying layers, Example~ of metal flbers wouLd be ~teel fiber~, fibers of Ren~ 41 (a nickel ba,sed alloy), niobium fibers~ molybdenum flbers and -tungsten fibersO
Filaments with a tungsten core7 th~t i~9 reinforcing elemen-ts which are manufactured by making -the actual reinforcing ma-terial. on a tung~ten'core of~ for exD9 about 12~um~ lo these belong in particular boron threads ~ (diameter approximately 9o-15c~lm3 whi'ch ca~
be addi-t.ionally coated with ~i:Licon carbide to a , ~ :
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thickness of about 4 ~Um9 or ~^rhose surface is treated with a nitration ~oron carbicle filaments with a tung~ten core~ silicon carbîcle filamen~ts (diameter apprOXimcltely lo ~m) with a tllng~-ten coxe and ti.-ta~it~ diboride filament~ w.ith a t~gsten core also belong to -this group~ A dl~advantage of the las-t~me~tio~led threads lies ln that -they ~re relatively thicko Synthetic ceramic fiber9: iOe~ synthetic ~ibers o~
borides7 carbides, nil;rides~ oxides, silicides and/or silicates.
To these belong in particular boron carbide fibers, boron nitride fibers and zirconium silicate fibers, which are very fine, as well as the coarser zirconium dioxide fiber~ and in particular the somewhat thicker aluminit~ oxide fibers; also the so-called Mullit fibers which comprise for the most part aluminitum oxide. The ceramic fibers~ as opposed to the metal fibers 9 have the advantage that when u~ing the ceramic substances according to the invention for the preparation of prosthetic elements, there is no danger of metallosis or electrolytic disturbances.
~asalt and kaolin .~ibers are also suitable (I~aolin fibers are preferably of thickness from about 1,um to about 6~um).
Details concerning the manufactt~re ~ld -the properties of the above-described fibers can be taken from a brochure on "~a~erver~tarl~te Hochlei~tung~-Verbund-werkstoffe" by Rainer ~aprogge, Rol~ Schar~achter, Peter Hahnel~ Han~Joachim Milller and Peter Steinmann, o~ ~he In3titut zur Erfor~chung tech~olo~i~cher Ent ~icklungslinien I~Eo - .. . .
., ' ` '; -, ` , A further group of fibers which is particularly suitablefor the manufacture of the cerc~mic subs-tances according to -the invention are the ~o called whiskers. ~l~iskers are discontlnuolls fibex-like ~ingle crystals with excep-tionally high tensile ~trength and modulus o~
elas-ticity~ ~hich however are a-t present relatively expensive3 But since only small quanti-ties of the whiskers ~re required for ~he ceramic substances according to the invention their use is also economically feasible. ~nliskers suitable for the cerc~mic substances according to the invention include in par-ticular berylliu~l oxide whis~er, boron carbide whisker9 graphite whisker, magnesium oxide whlslcer, alumlnium nitride whiske~r7 silicon nitr:Lde whisker as well as in particular aluminium oxide tha-t i~'9 sapphire trhiskex and silicon carbide whisker. Silicon carbide hiskers occur in t~o modiflcations 9 the so~called ~-sil:icon carbide whisker and -the so~called~silicon carb~de whisker. The.~-silicon carbide whiskers are hexago~ally~centered9 in diameter about 10~um to about too~um9 and in length about -I to about 60 mm. The ~-silicon carbide whiskers are cu~ic 9 having diameters of about o 9 5jum -to about 3 ~m~ and lengths of about 1 to about 30 mm Precisely these ~ sllicon carbide whiskers are excellently suited for embedding in dental ceramic base substances. ~esides the above-me~tioned ~hiskers 7 me-tallic whiskers such ~s~ for e~amplep chrome ~rhiskers9 iron whiskers9 cobalt whiskers and nickel whiskers 9 conditionally also copper- and silver whiskers, can also be used in ways according -to -the inveIltion. The s~me applie~ also ~or the so-called Schladi-t~ whiskers, these being poly-crystalline me-tallic threadsO The above-mentioned metallic ~rhlskers are all likewise subject to the disadvantage already mentioned in connection wlth , . . . .
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~ 9 metal filaments~ namely -th~t whe~ not completely covered by the matrix of the ceramic base substance -they can~
on coming in-to contact with body liquids, be the source o~ possible metallosis and e:Lec-trolytic di~tu~bances, i~ -the cerG~m.ic substances procluced :~rom them and -the corxesponding base substances are used for implants.
Details co~cerning the above-mentioned whiskers~
expecially as to thelr manu~acture and their proper-ties 9 can be taken ~rom the previously-mentioned brochure on "~aserverstarkte Hochleistungs~Verbundwerkstof~e".
With respect -to the silicon carbi.de whiskers attention is dra~n also to an article by A.~ipp in the journal "Feinwerktechnik" 74~ year -1970, iSSlle number 4~
pages 150~15~c D~tails concerning polycrystalline me-tallic whiskers or metallic threads can be taken ~rom articles by Hermann J~ Schladitz, published in "Fachberichte fur Oberflachentechnik" 8.yeax 197c, issue number 7989 pages 145-150 and "Zeitschrift fur Metalllcunde" ~and 59/l9689 issue number 19 pages 18 ~ 22.
Generally one always uses one type o~ fiber in one ceramic base substance. In principle~ however, also mixtures of dif`ferent ~ibers can be used in one ceramic base ~ubstance, As base substances~ which are mixed with the above-mentioned fibers together with the ceramic ~ubstances accoxding to the invention, conven-tional ceramic substance~ intended-as bone substi-tute~ particularly glass-ceramic materials9 -the ~amiliar de~tal-ceramic substances and hard ceramic~ as well as aluminium o~ide ceramic substances and aluminium phosphate can be usedO
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As ba3e subs-tances one can use in particular so-called core ~ubstances i.e. porcel~in sub~tances which are used in a con~en-t:ional wc~ for -the inner makeup of arti~icial -teeth ~ld ~o~called dentine sub~s-tc~nces i~e. porcelains which ~hould replace the den-tine in the natural -toothO
One can ho~Jever also use the so-called en~mel substances~
these serving as en~mel layer for artificial teeth and porcelain crownsO So far as the base substc~nces -this applies for core - and den-ti~ substances are normal dental-ceramic substances9 -they con-tain mixtures of quarz9 ~aolin9 and feldsparO ~ypical e~amples of such ba~e qub~tances contain 70-9o parts by weight ~eldspar9 especially orthoclase-(potassium)~f`eldspar, about o95 to 15 parts by weight - pre~erably 1 to 10 parts by ~eight - kaol~n9 and about 095 to 25 pax-ts by weight ~ pre~erably about 1 -to 18 parts by wt. -quarz7 as ~rell as about o to 2 parts by w-to -preferably O to 1~3 parts by wt~ ~ pig~en-ts and opaques.
Instead of` the quarz 9 various allotropic sillcon compounds such as 7 for example 9 cristobalite) can be used~ this serving in par-ticular to regulate the thèrmal coef~cient of expan~ion. An increase in -the proportioll of silicon increases the power of resistance. Other ba~e substances con-taln in place of the felaspar nepheline s~enite7 a mineral made up of approximately 50% sodium feldsparg (albite) 25%
potassium feld~par (microlite3~ and 25,~ nepheliteO
In the case of` the dentine substances the sllicon content can be raised to about 20 parts by wt. In the base su~s-tances the silicon content can be wholl~
or partly replaced by aluminium oxide. If the aluminium oxide content is raised~ for example to 60 ~nd 70 par-ts by wt.9 then base substance~ are obtained which can be classi~ied with the familiar hard porcelains and can al30 be referred ~o a~
aluminlum o~ide ceramic ~ub~tances.
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q`he base substances can ~urther contain various fluxes, such as7 ~or example9 li-thi-~ and potassium silicate~
which effect a:lter~tion~ in the firing terQperature or the thermal coef:l'icien-t of expansion. The addltion of a f1U~Y enables c~dap-ta-t~on of the base substances -to the the~mal coef~icient of expan~ion of me-tals or hard ceramics~ ~o that these base sub3tc~ces can be ~ired onto profile parts~ cores, inserts or super-structures of these material3. One differen-tiate~
accordingly between metal-ceramic and hard-cera~ic ~ubstances~ As examples of all~inium oxide ceramic substances~ i.e. of ceramic ~ubstances which can be fired on-to Al20~ cores9 the Vltadurr and vitadurJ S_ ceramic subs-tances can be mentioned9 which are a~ailable as core sub~-tances~ den-tine substances ~nd as en~mel substances~ and which are manufactured by the Vita Zahnf'abrik Sackingen in Wes-t GermanyO
Relevan-t detalls c.~ be taken from the brochure "Die Vitadur~ec~mik" Nr~11/73 - 500 of the Vita Zahnfabrik9 Sackingen- Germany~
~xamples of metal ceramic substances are described in the D~ S 1 441 346; to which reference is here made. As further examples of me-tal-ceramic substances "~ i~
the Biodent-dentlne a~d the Blodent core ~ubstances o~ the firm De Trey Gesellscha~t D 6200 Wiesbaden as well as the Vita-~VP~ substances of the Vita Zahnfabrik; S~ckingen, Germany and the Vi~odent-PE- ;
ceramie substances of the firm Ivoclar AG ~-9494 Schaan/~æ htensteln can be mentioned~
An example o~ a metal~ceramic base substance sinterlng a-t a f~ring temperature o~ 9ooC has the following composltion~
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~__ _=_ Percent Component Percent SlO265~518 ~i20 1~236 A12 ~14, o7E3 ~aO 1, 778 ~.
K20 97552 MgO 1,202 ~a20 6~6~6 _~ ~ .____ ___ f~ .
Examples of glass ceramic base substances are the pyre~
glass from -the GCC Company in Japan and Vycor glass ~rom -the Dentists Supply Company in the USA.
r~he DT AS 2 326 loo describes a glass ceramic base substance with apatite cry~tal phase, which can likewise be used for the manu~ac-ture of substances according -to the invention.
rrhe DT-OS 2 238 263 describes a further ex~mple for ceramic ba~e substances~
The above-mentioned ceramlc subs-tances are for the most part not porcelains accordlng to the classical description - i.e. not mixtures of quarz9 feldspar and Eaolin, but porcelain produc-ts attaining to a differen-t concept which7 wi-th respect to their composition, molding and flring do not resemble normal porcelain in any way. With regard to this terminology attention i~ dra~m in particular to an article by Dr. Walter Pralow9 Sackingen, in the journal "Das Dental ~abor"
issue number 2/1969, pages 66 e-t seq~ The adoption of the expression "Ceramic substances" for these substances too arises from the fact that theqe substances are prepared according to ceramic methods 7 although as ~ar as their composition is concerned, -they resemble more the glassesO
, Substances are preferably used ~/hosc firing -temperatures lle in -thc region O L' 900 -to l 400C 9 preferabl~y 900-1 200(l o The melting temperatures of the threads mus-t be higher than the sinterillg temperature of the base substances used in con~unctlon with them7 -this tempera-ture difference amounting to some thousand degrees Celsius~ for example to abou-t ~1ooC. ~`he temperature differences are preferably 400~ or more, ~he fibers used are preferably of lengths fro~ abou-t o,l to 60 mm9 whereby lengths from about o,5 mm to about 30 mm are par-ticularly preferred. Fibers of lengths from o,5 mm ~o about 3 mm are particularly suitable for the productlon of porous bodics, preferably for the dental field.
The thickness of the fîbers emplo~,ed reaches as a maxtmum -to about 600 ~m9 whereby fibers of -thickness from about o75 ~ to about 100 ~ are preferred. For the prepara-tion of dental ceramic substances whlch are applied as the outer layer on implants 9 ~rhiskers of thickness from about o,5 ~ to about 20J~m have proved suitable9 thicknesses to about 10 ~Im being especially favourable, The best results to date were obtained with ~ -silicon carbide whiskers, these having a thickness of abou-t o,~ to 3 ~m.
Very good results were obtained with basalt threads of thickness about 6 ~ and length~ about 1 - ~ mm, and carbon fibers with a -thickness of about 10 ~lm and lengths from about o,5 mm to about 195 mm.
For -the formation of a layer permeated by vacuoles 9 on the other hand, this enabling an easier ingrowth of bone subs-tance 9 relatively small additions of fibers to the ceramic base substances sufficeO
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Experimen-ts have shown that a fiber Vol.% o~ o,oo5 to 0702 relative to -the cerc~mic ba~e substance in ~mprocessed powder condition can be adequate.
For the forma~ic)n of -the layer permea-ted by vacuoles, use o~ fibers wi-th up -to 5 ~t.~ preferably approx.
0 9 oo2 to about o,o5 wt~g - relative to the weight of the ceramic base subs-tance in ~ot-yet-processed po~der form - gi~Jes excellent resultsl In a special modification -the cer~mic substances contain an admix-ture of approx. 1 ~ 20 wt.%, preferably about 2 -to about 5 wt.~', relative to the total substance, o:~ very finely divided metallic silver.
These silver-con-taining cerclmic sub~qtances are used preferably in the case of enossal implants at -those points where the implants extrude from the body tissues9i.e. a~ those points where -there is an increased risk o~ infection. With arti~icial teeth this is the region where the dental root extrudes from the aaw bone into -the mouth cavity~ Here for example, the sil~er-containing ceramic subs-t~nce is applied as an approx. 2 mm wide ring to the artificial dental root9 so tha-t the subs-tance9 on accoun-t of -the anti-bacterial e~fect of the silver, serves as a barrier agains-t lntroduction of bacteria in the ja~ regionO
, Introduc-tion of the very finely-divided me-tallic silver into the ceramic substance can be effected as follows: To any one of the above-described ceramic base substances - preferably a de~n-tine substance B such as, ~or example~ a Vitadu~r~ entine substance -a silver salt havillg anions easily decomposed by heat or an easily reducible silver salt is added ~-: .
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~ 15 -in quantities from abou-t 1 to about 50 wt.~o~ preferably about 5 to about 30 w-t.~' relative to the cerc~lic base sub~tance9 ancL i'J lmiformly mlxed with the cer.~mic base sub~tance~ the salts pre~erably being in solu-tion.
Silver salts fro~ organic acids are especially suitable 9 as for example silver oxalate~ silver acetate 7 and silver tartrate. Also silver nitricum~ i~e. silver nitrate~ is suitable hereO ~hesilver salts mixed with the base substances are subsequently decomposed.
This is possible by warming above -the relevant de composition temperature. With this procedure however ~reat care must be -taken since ~ as for example with silver nitrate ~ poi~onous ~umes can result which must be very care~ully led of:~ In order -to avoid endangering the personnel with fumes of this sort the decomposition is accordingly carried out preferably by a chemical reduction. The mixture of silver salts and base subs-tances i~ hereby mixed wi-th a reducing agent.9 as they are used for example in photography~
belng referred to as "Developer"~ Exc~mples of such reducing agents or developers are a~droquinonej hydro quinone~ pyrocateching ortho- and meta- amino phenols, such as metol (para - n - methamino - phenol);
glyci~ (4 hydro~y-phenyl-amino acetic acid);
phenidon (1 ~ phenyl - pyracolidon 3) hydra~ine;
hydrophosphorous acid H3P02; di-thionate (Na2S204) as well as in particular formalin~ aldehydes such as formaldehyde9 acetaldehyde9 propionaldehyde and also ascorbic acid and glucose. By stirring the mixture of the relevc~nt ceramic sllb~tance and th~ relevant silver salt to a paste with the solution of such a developer7 metallic silver is made to precipita~te out from the silver saltO ~he product is subsequently washed several times wi-th distilled waterO
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~hen using formalin~ acetalhyde9 propionaldehyde, ascorbic acid a~ld glucose as reducing agent the repeated washlng can be omitted dne to their good compatlbility under different condition~. ~he product is -then dried and ~round in a mortar9 af-ter which it can as ceramic base substance be further processed - as described beiore - and with fibers mixed into it or not.
In the following an exc~mple is cited for the introduction of very finely-divided me-tallic silver into a base subs-tance:
1 g of 3llver nitrate ~nd 10 ml of dist:illed water are in-troduced illtO a 100 Dll flask~ Through shaking the silvex nitrate i~ dissolved. Then 10 g of a Vitadur dentine base substance are added~ as well as 20 ml o~ a normal commerclal hydroquinone developer~
~he mixture is ~h~en carefully~ The Plask i3 sub-sequently filled with distilled water and the product allowed to settleO ~he liquid is then decanted9 and the residue washed by repeated filling with9 shaking and decanting of distilled waterO ~he solid matter a-t the bottom of the flask is then dried~
~he dried product is ground in a mortar. It can then be further processed7as previously described.
~he ceramic substances according to the invention can~ according -to the requirements in each case~
be mixed afresh ~rom the fibers and a co~sponding base substance by the technician responsible~ In this case it is ad~antageous i:f -the fibers can be supplied in packages quantities~
In many cases however i-t is preferable iP the cer~mic substances are provided already mlxed~ and need only be opened and fired. With a number of fibers which don't exhibit any large sur~ace energies and don't ha~e a tendency to form bundles~ it is sufficient }
~'7~ 3 ~ 17 --to mix -the fibers o~ the corresponding lengths c~nd thicknesses with -the relevant quantity of powdered ceramic base substance. In the case o~ other ~ibers however, this is not always possible9 since these, on accoun-t of large sur~ace energies9 are held together in balls or bundles, this making a uniform B mixing wi-th -the ceramic base substances dif~icult.
This is the case particlllarly wi-th7 for example9 basalt fibers and whiskers, wheE~y especially with ~ silicon carbide whiskers separation problems occur. In these cases the fibers are brought into contact with a liquid or solicl medium becoming volatile below the sintering -temperature of the ceram~ base substances9 this medium e~hibiting a surface energy which enables or effects separation of the fibers. ~or this such media are preferably used whlch soliclify a-t room -temperature and which are liquid at aomewha-t higher temperaturesD '~he separation of the fibers occurs -through the fibers being mixed with -the liquid or llquefied medium.
Examples of such media suited for the separation of fibers are synthetic materials, syn-thetic resins, waxes and glycerine 9 or cocoa bu-t-ter, whi~ have proved success~ul particularly ~or the separation of~-silicon carbide whiskers, basal-t ~ibers and carbon fibers.
'~he ceramic baSe substances can be stirred i~to the liquefied medium either after ~ 9 or just immediately before the processing of the ceramic substancesp for which purpose the medium bringing about the separa-tion is warmed again above its solidification point. ~lhen cocoa butter is ~l~ed for separation o~ the fibers c~d kneading o~ the Cel'amiC subs-tances9 it is added i~ quan-tities o~
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~ 18 -is added in quanti-ties of about 10 - 100 wt.%~ pre~erably about 40 ~ 80 wt.r~o relative to -the ceramic substances of fibers and b~se substances as according to -the inven-tion.
It is particu1arly useul to clecant the ceramic substances after their prepara-tion into small containers~ for example in mixing capsules, and to let them solidify in these.
For the proce~sing of the ceramic substances~ the same are then warmed up in -their containers so tha-t they can be applied directly from these and processed.
~Ihen the ceramic subs-tances are prepared by means of a single mixture of -the base subs-tances wi-th fibers having I10 -tendency form bundles, they are fur-ther processed as follows:
The ceramic substances are mi~ed to a pas-te with a modelling liquid which can be the sc~me one as employed for mixing the ceramics used as base subs-tances. r~he quan-tity of the modelling- or respectively mixing liquid amounts to about 5 - 10 wt.% to the quantity of the ceramic substanceO Possible excesses of the mixing liquid are drawn off, for example by means of blotting paper Dis-tilled water is particularly suitable as a mixing liquid.
Subsequently the dough-like ceramic substances are indtroduced into a mold, or compression mold, whose shape corre~ponds to that desired for the end product af-ter the ~lring3 for example a dental implant or a bone implant. ~hrough shaking or such methods the ceramic substances are adequately consolldated ? preventing the appearance of undesired large cavities during the firing and ensuring tha-t -the model is in each case perfectly shaped. The ceramic substances can also be fired onto a substrate. In this case they are applied in the desired layer thickness.
If the ceramic ~ubstances according to the inven-tion con-tain fibers wi-th a tendency to form bundles and are mixed with the corresponding base subs-tances by means of the previously described volatile medium exhibiting a high surface energy, or if non-bu-ndle-forming fibers are mixed with these media7 preferably with cocoa butter which is preferred since this cocoa butter~ on heating~ doesntt boil bu~ just sublimes ~, , . . ~
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directly3 then before introducing the mass into -the mold or applying on-to a substrate it must be heated above -the melting point of the medil~
~Jhen flring so~prep~red ceramic substances according to the invention a mllffle furnace or ~no-ther corresponding furnace or a hot press con-taining -the ceramic substances according to the invention is heated firs-tly to a temperature lower than tlle sill-tering -temperature of -the base substances used in the ceramic substc~nccs but ~Jhich however is high enough to cause the meclium bringing abou-t a separation of the fibers, orthe mixing fluid9 to e~apora-te or sublinle.
This temperature is prefer2bly selected to lie be-tween abou-t 400C and about 600C, usually abou-t 500C. This temper-ature is maintained lon~ enough to confirm that the mixing liquid or the medium bringing about a separation of the fibers has completely evapora-ted or sublimed. This can be determined for the individual media by sirnple experimen-ts, whereby one carries out the procedure over varying time intervals, letting the substances subsequen-tly become cold and then de-termining the proportion of -the medium by analysis. This pre-firing -takes as a rule about half an hourO ~fter this the temperature in the furnace is raised to the firing temperature of the base substances used in the ceramic subs-tances in each case. These telnperatures are in the case of normal commercial ceramic substances9 which are as a rule used for the base substances)in each case indicated. ln the case of other base substances they are determined by simple experimental series, ~Jhereby the firing temperature for dif~erent samples is raised step-wise by a few degrees Cel~ius When -the desired temperature in the interior of thc cer~nic subst~nces according -to the invention has been reached, this temperature is maintained for the normal firing time for flring of -the corresponding base substances - i.eO for time in-tervals ranging be-twcen
The present invention ha~ as its object suggestion of a Method for the preparation of implants which is particularly slmple and is easible with conventional equipment available in den-tal laboratories, using conventional techniques and not involving additional expense pertaining to apparatusO This problem ls solved according -to the invention ln that by introducing a model of the implan-t i~to a pa~te-like, high-tempera-ture embedding substc~lce and leaving it in this until the embedding sub~tance harden~ a nega-tive mold of the implant ls produced~ and that after removal of the model -the mold is lined via an opening reaching into its interior ~ith a layer of a cer~c subs-tance which should form the outer layer of the implan-t, that the cavity of the mold is subsequently filled completely with dentine or core substances, that the opening is then sealed with a paste-like, high-temperature embedding substance9 that said embedding substance is allowed to dry and that the whole thing is then heated to the sintering temperature of the ceramic substances used and the ceramic substances fired at this tempera-ture for the usual time, Theequipment available in dental laboratories for the preparation of centrifugal castings suffices for carrying out the method according to the invention;
the embeddlng substance is preferably introduced in-to a muffle or cuvette which is free of scale.
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It is advantageous if the muffle i3 fllled at fir~t to about two thirds with the embedding substance prevlously stirred to a paste 7 the model subsequently pushed into the embedding substance from above and after hardening of same pulled out again ~ and if after filling the negative mold with ceramlc subs-tance the rest of the muffle ia filled up wlth embedding subst~nce~
It has proved f~vourable to prepare the negative mold using a wax model of the implant which is burned out after the embedding substance has hardened. ..
A varicl~t of the method accordlng to the inv~ntion i~ characteriæed in that a shell mold corresponding to the shape of the implant i~ llned vi~ an opening reaching into the interior of said ~hell mold with a layer o~ a ceramic substance which should form the outer layer of the implant 9 that the shell mold ls ~ubsequently filled completely with dentine or core substances, that the opening is then sealed with a paste-like~ high-temperature embedding substance 7 that said embedding substance is allowed to harden and that the whole thing is then heated to the sintering temperature of the ceramic ~ubstances used and the ceramic substances fired at this temperature for the usual time. ~he shell mold cons~sts of a noble metal alloy (pre~erably platinum or a platinum alloy) which i~ not affected by change o~ temperature and which is not destroyed a~ the ~iring temperatures of approx~ 1000 -to 1500~
The negative mold~ or shell mold7 is preferably ~illed by applying the ceramic substance 9 mixed to a paste . . .
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,f~ ,t,~j~2,.
with cocoa-butter or ano-ther conYe~tional pasting agent9 in layersO ~he outermost layer applied to the wall of -the mold, or shell mold~ which on flring provides the desired porosity a is applied to a th1ckness o~ o 9 1 to 5 mm, preferably about o,3 to about 1 mm. It can be fired prior to filling up the rest of the space in the mold wi-th a dentine or core substance~ The imp~nt obtained by the method according to -the inventlon is expedientl~J treated after its removal from the embedding subs-tance with a sandblast blower7 at leas-t in the region to be implan-ted 7 in order to guaran~tee complete opening of the vacuoles; in so doing the area which is no-t to be implanted can, i:E necessary~ be covered~
in particular wi-th a wa~ or a plastic foil. In order to reinforce the interior structure o~ the implant a metal or ceramic insert can be introduced, before covering the opening leading to the interior of the mold with embedding substance which has been mixed to a paste~ into the in-terior of said mold~ this being already covered~ at lea~t at the edge 9 or already par-tly or comple-tely fllled with ceramic substance.
~luminium oxide tubes or pins which protrude above the mold a~d later serve for fixation of the crown or other superstruc-ture are especially suitable for this.
The ceramiC gubsta~ces used for the ou-ter la~er of the implant are characterized by a mixture of a ceramic base substance and fine inor~anic fibers, whose melting temperature is higher than the sintering temperature of -the ceramic base substance. When preparing ceramic substances according to -the invention care ls taken that -the ceramlc base substance, in the molten form that it talces on during sintering, does not dissolve the fikers as suchO
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~y fine fibers in this specification9 fibers or filaments and wires having a diame-ter less than about o~6 mm are understood.
Th~ fibers accoxcling to the inven-tion can be present in the cerclmic base substance matri.x in the form of whiskers~
filameIltg 9 staple fibers~ chopped fibers, threads, chopped strands as well as further processed products such as slubbings~ rovings, net-ting~ matting9 fibrous webs~
bonded fibrous materi.als, felts and woven materials.
Usually~ that is 9 if no extreme reinforcement effect .is required, it suffices to have the fibers in short pieces~
of lengths approximately o,1 ~ 60 mm9 preferably abou-t o,5 - 30 mm, in -the cexamic base substc~nce.
.For the productlon of porous ceramic bodies 7 fibers in pieces of abou-t o,5 - about 3 mm are particularly suitableO An adqua-tely uniform distribution of the fibers in the base subs-tances is generally sufficient to ensure that the cerc~mics manufactured ~rom -the substances have the desired rigidityD This applies especially for the production of porous ceramic bodies having surfaces not prone to rejection by the tissues and ~hich enable adherence and ingrowth of bone tissue~ These porous bodies contain a large number of ve~icular cavities merging par-tly into one another like a spongeA The pores vary in diameter from the ~mallest pore of diameter less than l~m to pores with a diameter of over 500~wm, whereby in one piece of ceramic pores of differan-t sizes are evident. Pores of diameter from about 10 to about 400 ~m are preferred. The average value of the pore diameter should be approximately 100 ~ 200 whilst the quantity of pores havlng a diameter larger than 300 ~ m should not account for more than 10yo~
pre~erably 5%. In the porous boclies the pores take up a volume of about 1o~,h to about 90/0 with respect to the total volume. Propo-rtions of pores from about 20 Vol,%
to about ~o VolOS' are especially sui-ted for use as adhering layer fox -the lngrot!rth o~ tissue~
convcntional orr~anLc fibers pxo~e ~suitable for the production of the sub3tances according to the invention since their melting points are lower than the temperatures necessary for the sintering together of the ceramic base substances~ the terlperatures for the ceramic base substances used lying in a region from abou-t 650-1 900C .
~he composition of -the ceramic base substances u~ed within the ~ramework o~ the invention at hand will be subsequently dealt w:ith in more detail.
In the following a series of ~ibers are indicated~
though not claiming entirety9 which are suitable for the manu~acture of ceramic substclnces as accord~ng to the invention. l`hey are as ~ollows:
Pure quartz fiberS from 99.9~6 silicon dioxlde~ which on account of their high thermal and chemical stability present no pxoblem~c~ when used lor implant~0 Carbon fibers9 which in the purest form are referred to as graphite fibers c~d are relatively economical to manufacture. When using cc~rbon fibers it must be remembered tha-t al&ough they present no physiological problems, the material exhibits a high heat conduction capactiy and a high electricity con~uction capacity.
~he prccessing of carbon fibers should be carried out in a vacuum in order to prevent oxidation, -;
Metal filame~ts~ manufactured by heat-draw~ng with or without sheathing and by pressing out of the melt ~: . . .
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-through narrow nozzle opening3 and su'b~equent solidif.ication3 '' or by the so~called ~a.ylor Proce~s2 Me-tal filaments wlth a diameter equal to or larger than 100 ~n can~ according -to DIN 60001 ~ be referred to clS wires~ ~hen metal :Eilaments or w:Lre~ make up the fiber con-tent Ln the ceramic substances according to the invention and these sub~tances are used for implan-ts 9 care should be ta~en -to use a cerc~mic ba~e substance whlch9 when molten~
wets the met~.l filaments well~ so tha-t after solidification of the ceramic ~ubstance these are~ if po~sible 9 not bare. O-the~ise they could be a-ttacked by the body fluid~ 9 which dissolve the metalcl and could lead to so-called "metallosls" iOe~ poisening b~y metal ions, ~he danger of such a metallosi~ is not great even if the me-tal filaments are not completely covered by -the ceramic bass ~ubstance7 si~ce the fibers account for only a small percentage of t,he total materl.al and are furthermore embedded for the most, part ln the ma-trix o~ -the cerc~mlc base substance. Since however there are o-ther fibers ~^rhere the danger of metallosis can from -the start be excluded, ceramic substance~ containing metal filaments as fiber content are generally not used for the outer layer of prosthetic elements but rather as reinforced core substance~9 these being covered by the overlying layers, Example~ of metal flbers wouLd be ~teel fiber~, fibers of Ren~ 41 (a nickel ba,sed alloy), niobium fibers~ molybdenum flbers and -tungsten fibersO
Filaments with a tungsten core7 th~t i~9 reinforcing elemen-ts which are manufactured by making -the actual reinforcing ma-terial. on a tung~ten'core of~ for exD9 about 12~um~ lo these belong in particular boron threads ~ (diameter approximately 9o-15c~lm3 whi'ch ca~
be addi-t.ionally coated with ~i:Licon carbide to a , ~ :
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thickness of about 4 ~Um9 or ~^rhose surface is treated with a nitration ~oron carbicle filaments with a tung~ten core~ silicon carbîcle filamen~ts (diameter apprOXimcltely lo ~m) with a tllng~-ten coxe and ti.-ta~it~ diboride filament~ w.ith a t~gsten core also belong to -this group~ A dl~advantage of the las-t~me~tio~led threads lies ln that -they ~re relatively thicko Synthetic ceramic fiber9: iOe~ synthetic ~ibers o~
borides7 carbides, nil;rides~ oxides, silicides and/or silicates.
To these belong in particular boron carbide fibers, boron nitride fibers and zirconium silicate fibers, which are very fine, as well as the coarser zirconium dioxide fiber~ and in particular the somewhat thicker aluminit~ oxide fibers; also the so-called Mullit fibers which comprise for the most part aluminitum oxide. The ceramic fibers~ as opposed to the metal fibers 9 have the advantage that when u~ing the ceramic substances according to the invention for the preparation of prosthetic elements, there is no danger of metallosis or electrolytic disturbances.
~asalt and kaolin .~ibers are also suitable (I~aolin fibers are preferably of thickness from about 1,um to about 6~um).
Details concerning the manufactt~re ~ld -the properties of the above-described fibers can be taken from a brochure on "~a~erver~tarl~te Hochlei~tung~-Verbund-werkstoffe" by Rainer ~aprogge, Rol~ Schar~achter, Peter Hahnel~ Han~Joachim Milller and Peter Steinmann, o~ ~he In3titut zur Erfor~chung tech~olo~i~cher Ent ~icklungslinien I~Eo - .. . .
., ' ` '; -, ` , A further group of fibers which is particularly suitablefor the manufacture of the cerc~mic subs-tances according to -the invention are the ~o called whiskers. ~l~iskers are discontlnuolls fibex-like ~ingle crystals with excep-tionally high tensile ~trength and modulus o~
elas-ticity~ ~hich however are a-t present relatively expensive3 But since only small quanti-ties of the whiskers ~re required for ~he ceramic substances according to the invention their use is also economically feasible. ~nliskers suitable for the cerc~mic substances according to the invention include in par-ticular berylliu~l oxide whis~er, boron carbide whisker9 graphite whisker, magnesium oxide whlslcer, alumlnium nitride whiske~r7 silicon nitr:Lde whisker as well as in particular aluminium oxide tha-t i~'9 sapphire trhiskex and silicon carbide whisker. Silicon carbide hiskers occur in t~o modiflcations 9 the so~called ~-sil:icon carbide whisker and -the so~called~silicon carb~de whisker. The.~-silicon carbide whiskers are hexago~ally~centered9 in diameter about 10~um to about too~um9 and in length about -I to about 60 mm. The ~-silicon carbide whiskers are cu~ic 9 having diameters of about o 9 5jum -to about 3 ~m~ and lengths of about 1 to about 30 mm Precisely these ~ sllicon carbide whiskers are excellently suited for embedding in dental ceramic base substances. ~esides the above-me~tioned ~hiskers 7 me-tallic whiskers such ~s~ for e~amplep chrome ~rhiskers9 iron whiskers9 cobalt whiskers and nickel whiskers 9 conditionally also copper- and silver whiskers, can also be used in ways according -to -the inveIltion. The s~me applie~ also ~or the so-called Schladi-t~ whiskers, these being poly-crystalline me-tallic threadsO The above-mentioned metallic ~rhlskers are all likewise subject to the disadvantage already mentioned in connection wlth , . . . .
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~ 9 metal filaments~ namely -th~t whe~ not completely covered by the matrix of the ceramic base substance -they can~
on coming in-to contact with body liquids, be the source o~ possible metallosis and e:Lec-trolytic di~tu~bances, i~ -the cerG~m.ic substances procluced :~rom them and -the corxesponding base substances are used for implants.
Details co~cerning the above-mentioned whiskers~
expecially as to thelr manu~acture and their proper-ties 9 can be taken ~rom the previously-mentioned brochure on "~aserverstarkte Hochleistungs~Verbundwerkstof~e".
With respect -to the silicon carbi.de whiskers attention is dra~n also to an article by A.~ipp in the journal "Feinwerktechnik" 74~ year -1970, iSSlle number 4~
pages 150~15~c D~tails concerning polycrystalline me-tallic whiskers or metallic threads can be taken ~rom articles by Hermann J~ Schladitz, published in "Fachberichte fur Oberflachentechnik" 8.yeax 197c, issue number 7989 pages 145-150 and "Zeitschrift fur Metalllcunde" ~and 59/l9689 issue number 19 pages 18 ~ 22.
Generally one always uses one type o~ fiber in one ceramic base substance. In principle~ however, also mixtures of dif`ferent ~ibers can be used in one ceramic base ~ubstance, As base substances~ which are mixed with the above-mentioned fibers together with the ceramic ~ubstances accoxding to the invention, conven-tional ceramic substance~ intended-as bone substi-tute~ particularly glass-ceramic materials9 -the ~amiliar de~tal-ceramic substances and hard ceramic~ as well as aluminium o~ide ceramic substances and aluminium phosphate can be usedO
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As ba3e subs-tances one can use in particular so-called core ~ubstances i.e. porcel~in sub~tances which are used in a con~en-t:ional wc~ for -the inner makeup of arti~icial -teeth ~ld ~o~called dentine sub~s-tc~nces i~e. porcelains which ~hould replace the den-tine in the natural -toothO
One can ho~Jever also use the so-called en~mel substances~
these serving as en~mel layer for artificial teeth and porcelain crownsO So far as the base substc~nces -this applies for core - and den-ti~ substances are normal dental-ceramic substances9 -they con-tain mixtures of quarz9 ~aolin9 and feldsparO ~ypical e~amples of such ba~e qub~tances contain 70-9o parts by weight ~eldspar9 especially orthoclase-(potassium)~f`eldspar, about o95 to 15 parts by weight - pre~erably 1 to 10 parts by ~eight - kaol~n9 and about 095 to 25 pax-ts by weight ~ pre~erably about 1 -to 18 parts by wt. -quarz7 as ~rell as about o to 2 parts by w-to -preferably O to 1~3 parts by wt~ ~ pig~en-ts and opaques.
Instead of` the quarz 9 various allotropic sillcon compounds such as 7 for example 9 cristobalite) can be used~ this serving in par-ticular to regulate the thèrmal coef~cient of expan~ion. An increase in -the proportioll of silicon increases the power of resistance. Other ba~e substances con-taln in place of the felaspar nepheline s~enite7 a mineral made up of approximately 50% sodium feldsparg (albite) 25%
potassium feld~par (microlite3~ and 25,~ nepheliteO
In the case of` the dentine substances the sllicon content can be raised to about 20 parts by wt. In the base su~s-tances the silicon content can be wholl~
or partly replaced by aluminium oxide. If the aluminium oxide content is raised~ for example to 60 ~nd 70 par-ts by wt.9 then base substance~ are obtained which can be classi~ied with the familiar hard porcelains and can al30 be referred ~o a~
aluminlum o~ide ceramic ~ub~tances.
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q`he base substances can ~urther contain various fluxes, such as7 ~or example9 li-thi-~ and potassium silicate~
which effect a:lter~tion~ in the firing terQperature or the thermal coef:l'icien-t of expansion. The addltion of a f1U~Y enables c~dap-ta-t~on of the base substances -to the the~mal coef~icient of expan~ion of me-tals or hard ceramics~ ~o that these base sub3tc~ces can be ~ired onto profile parts~ cores, inserts or super-structures of these material3. One differen-tiate~
accordingly between metal-ceramic and hard-cera~ic ~ubstances~ As examples of all~inium oxide ceramic substances~ i.e. of ceramic ~ubstances which can be fired on-to Al20~ cores9 the Vltadurr and vitadurJ S_ ceramic subs-tances can be mentioned9 which are a~ailable as core sub~-tances~ den-tine substances ~nd as en~mel substances~ and which are manufactured by the Vita Zahnf'abrik Sackingen in Wes-t GermanyO
Relevan-t detalls c.~ be taken from the brochure "Die Vitadur~ec~mik" Nr~11/73 - 500 of the Vita Zahnfabrik9 Sackingen- Germany~
~xamples of metal ceramic substances are described in the D~ S 1 441 346; to which reference is here made. As further examples of me-tal-ceramic substances "~ i~
the Biodent-dentlne a~d the Blodent core ~ubstances o~ the firm De Trey Gesellscha~t D 6200 Wiesbaden as well as the Vita-~VP~ substances of the Vita Zahnfabrik; S~ckingen, Germany and the Vi~odent-PE- ;
ceramie substances of the firm Ivoclar AG ~-9494 Schaan/~æ htensteln can be mentioned~
An example o~ a metal~ceramic base substance sinterlng a-t a f~ring temperature o~ 9ooC has the following composltion~
.:
~__ _=_ Percent Component Percent SlO265~518 ~i20 1~236 A12 ~14, o7E3 ~aO 1, 778 ~.
K20 97552 MgO 1,202 ~a20 6~6~6 _~ ~ .____ ___ f~ .
Examples of glass ceramic base substances are the pyre~
glass from -the GCC Company in Japan and Vycor glass ~rom -the Dentists Supply Company in the USA.
r~he DT AS 2 326 loo describes a glass ceramic base substance with apatite cry~tal phase, which can likewise be used for the manu~ac-ture of substances according -to the invention.
rrhe DT-OS 2 238 263 describes a further ex~mple for ceramic ba~e substances~
The above-mentioned ceramlc subs-tances are for the most part not porcelains accordlng to the classical description - i.e. not mixtures of quarz9 feldspar and Eaolin, but porcelain produc-ts attaining to a differen-t concept which7 wi-th respect to their composition, molding and flring do not resemble normal porcelain in any way. With regard to this terminology attention i~ dra~m in particular to an article by Dr. Walter Pralow9 Sackingen, in the journal "Das Dental ~abor"
issue number 2/1969, pages 66 e-t seq~ The adoption of the expression "Ceramic substances" for these substances too arises from the fact that theqe substances are prepared according to ceramic methods 7 although as ~ar as their composition is concerned, -they resemble more the glassesO
, Substances are preferably used ~/hosc firing -temperatures lle in -thc region O L' 900 -to l 400C 9 preferabl~y 900-1 200(l o The melting temperatures of the threads mus-t be higher than the sinterillg temperature of the base substances used in con~unctlon with them7 -this tempera-ture difference amounting to some thousand degrees Celsius~ for example to abou-t ~1ooC. ~`he temperature differences are preferably 400~ or more, ~he fibers used are preferably of lengths fro~ abou-t o,l to 60 mm9 whereby lengths from about o,5 mm to about 30 mm are par-ticularly preferred. Fibers of lengths from o,5 mm ~o about 3 mm are particularly suitable for the productlon of porous bodics, preferably for the dental field.
The thickness of the fîbers emplo~,ed reaches as a maxtmum -to about 600 ~m9 whereby fibers of -thickness from about o75 ~ to about 100 ~ are preferred. For the prepara-tion of dental ceramic substances whlch are applied as the outer layer on implants 9 ~rhiskers of thickness from about o,5 ~ to about 20J~m have proved suitable9 thicknesses to about 10 ~Im being especially favourable, The best results to date were obtained with ~ -silicon carbide whiskers, these having a thickness of abou-t o,~ to 3 ~m.
Very good results were obtained with basalt threads of thickness about 6 ~ and length~ about 1 - ~ mm, and carbon fibers with a -thickness of about 10 ~lm and lengths from about o,5 mm to about 195 mm.
For -the formation of a layer permeated by vacuoles 9 on the other hand, this enabling an easier ingrowth of bone subs-tance 9 relatively small additions of fibers to the ceramic base substances sufficeO
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Experimen-ts have shown that a fiber Vol.% o~ o,oo5 to 0702 relative to -the cerc~mic ba~e substance in ~mprocessed powder condition can be adequate.
For the forma~ic)n of -the layer permea-ted by vacuoles, use o~ fibers wi-th up -to 5 ~t.~ preferably approx.
0 9 oo2 to about o,o5 wt~g - relative to the weight of the ceramic base subs-tance in ~ot-yet-processed po~der form - gi~Jes excellent resultsl In a special modification -the cer~mic substances contain an admix-ture of approx. 1 ~ 20 wt.%, preferably about 2 -to about 5 wt.~', relative to the total substance, o:~ very finely divided metallic silver.
These silver-con-taining cerclmic sub~qtances are used preferably in the case of enossal implants at -those points where the implants extrude from the body tissues9i.e. a~ those points where -there is an increased risk o~ infection. With arti~icial teeth this is the region where the dental root extrudes from the aaw bone into -the mouth cavity~ Here for example, the sil~er-containing ceramic subs-t~nce is applied as an approx. 2 mm wide ring to the artificial dental root9 so tha-t the subs-tance9 on accoun-t of -the anti-bacterial e~fect of the silver, serves as a barrier agains-t lntroduction of bacteria in the ja~ regionO
, Introduc-tion of the very finely-divided me-tallic silver into the ceramic substance can be effected as follows: To any one of the above-described ceramic base substances - preferably a de~n-tine substance B such as, ~or example~ a Vitadu~r~ entine substance -a silver salt havillg anions easily decomposed by heat or an easily reducible silver salt is added ~-: .
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~ 15 -in quantities from abou-t 1 to about 50 wt.~o~ preferably about 5 to about 30 w-t.~' relative to the cerc~lic base sub~tance9 ancL i'J lmiformly mlxed with the cer.~mic base sub~tance~ the salts pre~erably being in solu-tion.
Silver salts fro~ organic acids are especially suitable 9 as for example silver oxalate~ silver acetate 7 and silver tartrate. Also silver nitricum~ i~e. silver nitrate~ is suitable hereO ~hesilver salts mixed with the base substances are subsequently decomposed.
This is possible by warming above -the relevant de composition temperature. With this procedure however ~reat care must be -taken since ~ as for example with silver nitrate ~ poi~onous ~umes can result which must be very care~ully led of:~ In order -to avoid endangering the personnel with fumes of this sort the decomposition is accordingly carried out preferably by a chemical reduction. The mixture of silver salts and base subs-tances i~ hereby mixed wi-th a reducing agent.9 as they are used for example in photography~
belng referred to as "Developer"~ Exc~mples of such reducing agents or developers are a~droquinonej hydro quinone~ pyrocateching ortho- and meta- amino phenols, such as metol (para - n - methamino - phenol);
glyci~ (4 hydro~y-phenyl-amino acetic acid);
phenidon (1 ~ phenyl - pyracolidon 3) hydra~ine;
hydrophosphorous acid H3P02; di-thionate (Na2S204) as well as in particular formalin~ aldehydes such as formaldehyde9 acetaldehyde9 propionaldehyde and also ascorbic acid and glucose. By stirring the mixture of the relevc~nt ceramic sllb~tance and th~ relevant silver salt to a paste with the solution of such a developer7 metallic silver is made to precipita~te out from the silver saltO ~he product is subsequently washed several times wi-th distilled waterO
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~hen using formalin~ acetalhyde9 propionaldehyde, ascorbic acid a~ld glucose as reducing agent the repeated washlng can be omitted dne to their good compatlbility under different condition~. ~he product is -then dried and ~round in a mortar9 af-ter which it can as ceramic base substance be further processed - as described beiore - and with fibers mixed into it or not.
In the following an exc~mple is cited for the introduction of very finely-divided me-tallic silver into a base subs-tance:
1 g of 3llver nitrate ~nd 10 ml of dist:illed water are in-troduced illtO a 100 Dll flask~ Through shaking the silvex nitrate i~ dissolved. Then 10 g of a Vitadur dentine base substance are added~ as well as 20 ml o~ a normal commerclal hydroquinone developer~
~he mixture is ~h~en carefully~ The Plask i3 sub-sequently filled with distilled water and the product allowed to settleO ~he liquid is then decanted9 and the residue washed by repeated filling with9 shaking and decanting of distilled waterO ~he solid matter a-t the bottom of the flask is then dried~
~he dried product is ground in a mortar. It can then be further processed7as previously described.
~he ceramic substances according to the invention can~ according -to the requirements in each case~
be mixed afresh ~rom the fibers and a co~sponding base substance by the technician responsible~ In this case it is ad~antageous i:f -the fibers can be supplied in packages quantities~
In many cases however i-t is preferable iP the cer~mic substances are provided already mlxed~ and need only be opened and fired. With a number of fibers which don't exhibit any large sur~ace energies and don't ha~e a tendency to form bundles~ it is sufficient }
~'7~ 3 ~ 17 --to mix -the fibers o~ the corresponding lengths c~nd thicknesses with -the relevant quantity of powdered ceramic base substance. In the case o~ other ~ibers however, this is not always possible9 since these, on accoun-t of large sur~ace energies9 are held together in balls or bundles, this making a uniform B mixing wi-th -the ceramic base substances dif~icult.
This is the case particlllarly wi-th7 for example9 basalt fibers and whiskers, wheE~y especially with ~ silicon carbide whiskers separation problems occur. In these cases the fibers are brought into contact with a liquid or solicl medium becoming volatile below the sintering -temperature of the ceram~ base substances9 this medium e~hibiting a surface energy which enables or effects separation of the fibers. ~or this such media are preferably used whlch soliclify a-t room -temperature and which are liquid at aomewha-t higher temperaturesD '~he separation of the fibers occurs -through the fibers being mixed with -the liquid or llquefied medium.
Examples of such media suited for the separation of fibers are synthetic materials, syn-thetic resins, waxes and glycerine 9 or cocoa bu-t-ter, whi~ have proved success~ul particularly ~or the separation of~-silicon carbide whiskers, basal-t ~ibers and carbon fibers.
'~he ceramic baSe substances can be stirred i~to the liquefied medium either after ~ 9 or just immediately before the processing of the ceramic substancesp for which purpose the medium bringing about the separa-tion is warmed again above its solidification point. ~lhen cocoa butter is ~l~ed for separation o~ the fibers c~d kneading o~ the Cel'amiC subs-tances9 it is added i~ quan-tities o~
. :
. - , :
~ 18 -is added in quanti-ties of about 10 - 100 wt.%~ pre~erably about 40 ~ 80 wt.r~o relative to -the ceramic substances of fibers and b~se substances as according to -the inven-tion.
It is particu1arly useul to clecant the ceramic substances after their prepara-tion into small containers~ for example in mixing capsules, and to let them solidify in these.
For the proce~sing of the ceramic substances~ the same are then warmed up in -their containers so tha-t they can be applied directly from these and processed.
~Ihen the ceramic subs-tances are prepared by means of a single mixture of -the base subs-tances wi-th fibers having I10 -tendency form bundles, they are fur-ther processed as follows:
The ceramic substances are mi~ed to a pas-te with a modelling liquid which can be the sc~me one as employed for mixing the ceramics used as base subs-tances. r~he quan-tity of the modelling- or respectively mixing liquid amounts to about 5 - 10 wt.% to the quantity of the ceramic substanceO Possible excesses of the mixing liquid are drawn off, for example by means of blotting paper Dis-tilled water is particularly suitable as a mixing liquid.
Subsequently the dough-like ceramic substances are indtroduced into a mold, or compression mold, whose shape corre~ponds to that desired for the end product af-ter the ~lring3 for example a dental implant or a bone implant. ~hrough shaking or such methods the ceramic substances are adequately consolldated ? preventing the appearance of undesired large cavities during the firing and ensuring tha-t -the model is in each case perfectly shaped. The ceramic substances can also be fired onto a substrate. In this case they are applied in the desired layer thickness.
If the ceramic ~ubstances according to the inven-tion con-tain fibers wi-th a tendency to form bundles and are mixed with the corresponding base subs-tances by means of the previously described volatile medium exhibiting a high surface energy, or if non-bu-ndle-forming fibers are mixed with these media7 preferably with cocoa butter which is preferred since this cocoa butter~ on heating~ doesntt boil bu~ just sublimes ~, , . . ~
... ..
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_ - 19 ~
directly3 then before introducing the mass into -the mold or applying on-to a substrate it must be heated above -the melting point of the medil~
~Jhen flring so~prep~red ceramic substances according to the invention a mllffle furnace or ~no-ther corresponding furnace or a hot press con-taining -the ceramic substances according to the invention is heated firs-tly to a temperature lower than tlle sill-tering -temperature of -the base substances used in the ceramic substc~nccs but ~Jhich however is high enough to cause the meclium bringing abou-t a separation of the fibers, orthe mixing fluid9 to e~apora-te or sublinle.
This temperature is prefer2bly selected to lie be-tween abou-t 400C and about 600C, usually abou-t 500C. This temper-ature is maintained lon~ enough to confirm that the mixing liquid or the medium bringing about a separation of the fibers has completely evapora-ted or sublimed. This can be determined for the individual media by sirnple experimen-ts, whereby one carries out the procedure over varying time intervals, letting the substances subsequen-tly become cold and then de-termining the proportion of -the medium by analysis. This pre-firing -takes as a rule about half an hourO ~fter this the temperature in the furnace is raised to the firing temperature of the base substances used in the ceramic subs-tances in each case. These telnperatures are in the case of normal commercial ceramic substances9 which are as a rule used for the base substances)in each case indicated. ln the case of other base substances they are determined by simple experimental series, ~Jhereby the firing temperature for dif~erent samples is raised step-wise by a few degrees Cel~ius When -the desired temperature in the interior of thc cer~nic subst~nces according -to the invention has been reached, this temperature is maintained for the normal firing time for flring of -the corresponding base substances - i.eO for time in-tervals ranging be-twcen
2 and about ~0 minutesp preferably about 6 to about l0 minutes Af-ter a further ~uar-ter of an hour -the furnace is opened and the fired subs-tance in the mold is removed 9 if necessary after a fur-ther cooling period in the furnace.
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'72~
~ 20 -Particular advantages are evident from the use of ceramic subs-tances according to the in~ention when these are ~ired as an outer layer onto the implant~
f'ormin~ re~pectlvely a peri.osteum ~ or dental periosteum substitute~ The ceram:ic base substance can here be either a core substance 9 a dentine substance or an enamel substance ? its speci~ic composition being dependant on whether the implant is to be made as metal-ceramic or as hard-ceramic.
~he implants exhibi-t in -this case 9 ~rom the outside -to the inside~ the following layering possibilities:
a) dentine subs-tance wi-th ~ibers ~ired on a core substance without fiber30 b) denti.ne substance with fibers fired on a den-tine substance without ~ibers, which in turn in given cases is ~ired on a core substanceO
c) core substance wi-th .~ibers) fired on a core substance without fibers.
d) enamel substance with fibers, fired on a dentine substance and/or a core substance without fibers.
when the ceramic substances according -to the invention form the outermost layer o~ a bone or dental root implant as bone periosteum-or den-tal root periosteum substitute, it is applied expedientley in thicknesses o~ about O,1 mm to about 5 mm~ preferably in thicknesses o~
about 0,1 mm to abou-t 1 mmO For dental implants the optimal thickness is about Oj~ mm to 0 7 5 mm. The desired vacuoles in this layer, which allow for -the ingrowth of tissue 9 are formed during firing o~ the ceramic subs-tances according to the invention~ provided this doesn't occur under high pressure ~ i~e~ in a vacuum (about 5 - 50 mm Hg~
preferably 10 20 mm Hg~) under atmospheric pres~ure and with small excess pressures~
:, :
~, , ~
- . ' . .
- 21 ~
B ~mplcs for po3~ibilit}~ ef ~r~7ing out the _~pro ing ~rc ~lcccri~ed ill r ~z 11 ~
With higher propor-tion~ of fibers pressures higher than 1 kp/cm2 are necessary in order -to ~void the pores of the fired product becoming too large and the product brittle. If the fibers are metallic ~i~ rs) the flrillg is carried out in a vacuum or in ~ presence of a protective gas in order -to prevent oxidation~ ~s protective gases the noble gases are particularly suitable i~e. Helium, Argon9 Krypton and Xenon, Argon being here the most preferred. If the firing accurs in sealed containers however, this precauting can, possibly be dispensea with. '~he size and number of the vacuoles, -tha-t is the porosity of -the periosteum ~ubs-titu-te layer produced from the ceramic substance according to the invention; can be regulated through the respectlve addition of fibers to the ceramic base substance.
The most suitable mix-tures ~lithin -the given values can be determined for the individual fibers by simple experiments~ ~1hen the vacuoles measure abou-t 10 ~m in diameter to about 300 ~m in diameter and/or in depth, a good ingrowth into the implant in the bone tissue is to be expected, i.e. the new-forming oone tissue grows into the vacuoles and creates a firm contact between bone a~d implant. One can observe this from X-Rays taken at time - intervals of several weeksO The previously-given value~ a~e to be understood as average values, Besides the vacuoles of the given size a large number of small and very small vacuole~ can be in evidence.
~lso the existence of single somewhat larger vacuoles doesn't matter.
.
- , . . .
:
, ~ .
It is particularly u~eful if the previously described cerc~mic substances intended ~or the ou-ter layer of the implant contain additional subs-tances stimulating bone formatlon and/or bone grow-th7 especially -tri-calcium pho3pha-te and tertiary calcium phospha-te.
Substances fur-ther sui-table ~or stimulating bone formation and/or bone growth are in particular sodiumr lithium? carbon9 magnesium9 boron, fluorine, silicon~
phosphorus9 calcium, potassi~m and/or -yttrium ions9 and/or ions of the rare earths, these subs-tances being added in body soluble form. Sodium~ calcillm, boron and phosphorus ions are par-ticularly favourable.
The suitability of these previously-lcnown ions for stimulating -the grow-th of bone ti~sue on-to vl-trified aluminium oxide ceramic is known from -the D~-~S
23 24 867.
In order to stimulate ingrowth into the implan-t i-t is preferable to in-troduce powdered apatite crystals -e.g. ground in a mortar - 9 which are kno~m to strongly accelera-te bone regeneration? into the ceramic substc~nces in-tended for the outer layer o~ the implant. Besides natural bone apa-tite~ apatites being l~omorphic to hydroxylapatite seem e~pecially suitable 9 in particular very small calcium phosphate hydroxylapati-te crystalsO
~he addi-tion involves about 5 to 70 wto % ~ preferably about 10 - 30 wt. Q/O rela-tive to the dry con-tent of -the ceramic substances~ Further substances ~timula-ting bone growth are described in the D~-OS 26 06 540. When ground to a powder they can serve as the additlve me~tioned.
~n addi-tion of denatured bone meal is al~o possible~
~he addition expediently involves about 2,5 wt. % -to about 70 wt~ %~ preferably about 5 wt. % to about 20 wt.
% relative to the dry content of the ceramic substance.
In the following, an ex~mple for the manufacture of denatured bone meal is given :
.. . .
: . , Calves' vertebrae are dried at 100C for 8 hours~ ~he dried bones are coarsely ground and subsequently freed from ~at by lea~ing in ether for 24 hours. ~fter drying o~ the ether the bo~e meal is left 2~ hour~
in 20S~ hydrogrcn peroxide ancl then boiled ~or 10 minutes in same~ The hydrogen peroxide is -then poured off and the material subsequen-tly dried. The powder obtained in -this wa~ from macerated bones is ground very finely in a mortar (this procedure is based on work by R. and ~ Ba~eister - see J. Bone Surg.
39 ~ 153 (t957) )-The Outermost layer of the implants thus preferablycontain an addi-tion of substances stimulat.ing bone ~ormation and/or bone growth, which is added to the ceramic subst~nces be~ore these are mixed to a paste.
Particularly useful here is apatite in powder foxm9 especially calcium phosphate hydroxyl apatite in quan-tities of about 5 to 70 wt. 5~, preferably about 10 to 30 wt. S~ relati~e to the dry conten-t of the ceramlc substancesO In -the following an example is given for the preparation of implants following the method according to the invention.
Fig. 1 showss ln the in-terior o~ a cuvette and ln longltO section, a den-tal root substitute to be implan-ted A
Figo 2 to 11 show schematically the individual steps of an embodiment o~ the preparatory procedureO
The procedures shown in Figso 2 to 11 are primarily intended for the preparation of implants ~Jhich reproduce the extracted teeth or the extrac-ted roots true to shape. These implants should1 in the roo-t region~ be provlded ~rith a porous coating layer having a large number of vacuoles enabling tissue ingrowth and thus rigid suppor-t of the implantO
, . ~
, ~ :
;
- 2~ -The implan-ts are made up o differen-t layers, surrounding one ano-ther9 in a manner similar to the dental prosthetic eLemen-ts prepared by conven-tional porcelain~press techni~1ues or metal ceramic techniques~
~ig. I show~ 7 in the in-terior of a cuvette 9 which in connection with its method of preparation will be dealt with more closely la-ter~ a tooth root substitute 1 in longitudinal sec-tion. ~he tooth root substi-tute 1 consists in -the roo-t region 2 9 seen Erom the in-terior to the e~terior, o~ a core substance 3~ in which a reinforcement element 4 is when necsssary embedded. ~he core subs-tc~lc~ 3 is surro~mded l~yerwlse on the outsicle by a dentine subs-tance 5, which ln turn is surxouncled by a layer 6 of special porous cer~mic substance, ~he layer 6 consists likewise of a dentine subs-tance or core substance which is mixed with thin inorganic fibers whose melting point is considerably higher than the temperature at which the materials making up -the artlflcial tooth 1 are sinteredO The layer 6~ measuring pre~erably abou-t 0 9 3 mm - O,5 mm in thickness is, as -already frequently describedy permea-ted by a large nu~ber of vacuoles 9 these allowing ingrowth of bone ~tissue when -the root region ~ is implan-ted in an ~artlficial or natural -too-th alveolus oE -the ~aw.
~ayers 3 and 5 can9 as a variation from the previous example9 also consist of a dentine, a core substance or aluminium phosphate~
In the example illustrated it is assumed that the dentine substance in layer 5 and 6 is the same. ~or this reason the dividing line represented in the figure between these layers is, in a section through a real artificial too-th or a dental root substitute~ only apparan-t in that within the dividlng line there are no fibers9 meaning that at the dividing line the porosity, or the depth of the vacuole-permeated outer layer9 essentially ends.
~ ~"
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s~
The den-tal root subs-ti-tute 1 can be made from metal-ceramic substances or from hard-porcelain B subs-tances 7 or from ~itadur~ or Vitadur-S-substances, whereby corresponding core substances~ corresponding dentine substances also in layer 6 ~ are usedO
In the case of metal-cer~mic substances the reinforce- ;
men-t element 4 consists of metal~
As metals in questions here one can use, among other special alloys used in metal ceramics, gold alloys with a high platinum content, which for the purpose o~
increased hardness contain iron and o-ther elements and melt at tcmperatures of about 1tO0 - 1200C~ ~lso palladium alloys, hardened ~ith ru-thenium, wlth small amoun-ts of gold or silver, which melt between abou-t 1450C and l600C~ as well as the so-called Feram alloys of cobalt-chrome from the Niranium Corpora-tion Long Island, and D.J. metal wlth nickel as base material of the Durallium Products Co. ahicago. ~he D~-OS 25 14 672 describes further suitable alloys. Fur-ther examples of such alloys are kno~m under the marks Deguden ~and ~egucas~, these being gold-ceramic and being manufactured by the firm Degussa ~ Dental- und Goldhalbzeug D 6000 Frank~urt.
Further gold-ceramics are known under the marks Herado~ (~irm Heraeus9 V.4, Va44) (Firm Métaux Précieux3 Degudent Swiss (Firm Cendres & Metaux) (Armator II) (Firm Uslne Genevoise Degrossissage dlor) Williams Gold, Ceramco Gold and Stern Gold. ~rom among the precious metal refined alloys are mentioned in partieular Wiro~ S and Wiro ~ which have a composition on the basis of nickel-chrome and are manufac-tured by -the firm Bremer Gold-~hlagerei Wilhm. Herbst 2800 Bremen 41 In the case of hard-ceramic substances the rei~forcement element 4 is a prefabrieated hard ceramic elemen-t~
preferably a small hard-ceramic bar, tube or sheet~
preferably of aluminium oxide.
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In -the following the me-thod of preparation of the dental root substi-tute will be dealt wi-th in more de-tail. Fig, 2 shows how a cuvette half 10 is le~e~
filled with a high-temp embedding subs-tance 12 which has been mixea to a paste. ~he embedding substance should if possible have a small thermal coefficient of expansionO ~xamples of embeddin~ substances are ~ecial substances such as Deguvest from the firm Deg~ssa~ B Dental- und Goldhalbzeug D 6000 Frankfurt 1 J
Wiroves~ from the firm Bego, Bremer Goldschlagerei, Wilh. Herbst 2800 ~remen 419 Emil-Sommer-Str~ 7, Neo-Brilla-t~rom the firm Dentalchemie C.C~ Schrepfer, Marburg /~ahn, Germany, ~urove~ ~or ~uroves~ B, a quarz embedding substance ~rom the firm Bego, Bremer Goldschlagerei, Wilh. Herbst and Hudrovest from the firm Frankonia in West-Germany.
In the embedding substance 12 of the lower cuvette halfy before it hardens, a wax model 13, true -to the origlnal is embedded wi-th the labial or lingual -side do-m as sho~m in Figo 3.
'-, .;:: :
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The wax model 13 is left in the embedding substance 12 un-til this is hardO I-t is -then pulled out again, as shown in ~lg~ ~ so -that a negative mold 14 is formed which is true to shapc ~en the embedding sub~tance is completely dry the ceramic substance, mixed to a paste9 of layer 6 is first applied via the uppex opening 15 of -the mold~
using a brush, spa-tula or ~omething similar. l~hen this in turn is dry9 the adjacent layer 5 is applied~
This stage is sho~n in Fig~ 5. Subsequen-tly~ the cavity remaining in the interior of layers 5 and 6 i5 filled with core substance ~; thi~ is also done preferably in layers. ~he end result is shown in ~ig. 6.
To reinforce the dental root substitute 1 a reinforce-men-t element ~ i9 introduced into the core substance 3.
Fig~ 7 shows this process9 Figo 8 the end result.
Subsequently an upper cuvette half 11 is positioned on top of the lower cuvette half; the upper half is connected to the lower one e.g. by means of pins which slide into holes9 not shown in more detail~ in the lower cuvette. ~he cuvet-te halves are connected such that the high pressure at sintering does not cause the two cuvette halves to be pushed against one anotherO
Positioning of the upper cuvette on the lower one is sho~m in Fig. 9~ The space above the hardened embedding substance 12 and the mold 14 filled with ceramlc substances is subsequen-tly filled completely with further embedding substance 16, ~ixed to a paste~
as is shown in ~ig. 100 lnhen the embedding sub3tance 16 i9 dry the cuvette formed from -the halves 10 and 11 is put into a furnace, i9 sintered there by mean~ o~ heat radiating from a heat source in the direction of arrow S, and is fired as previously described~ The finished dental root substitute 1 is freed after cooling by mechanically destroying the embedding subs-tance. ~fter removal of ridges and projectlng material, the sub~titute , ~ 28 is treated with a sandblast blower~ preferably with very fine corundum9 so -that the pores in -the outer ~yer are opened~
In~te~d of -the two-part cuvette shown in ~igso 2 to 11 it is naturally also possible to use a single cuvette, which is initially only partly ~illed9 preferably to about two thirds 9 with the embedding substance in which~ using a model, a negative mold is made. According to a variant of the preceding method which is especlally suitable for -the preparation of prefabricated implants of the same ~hape, a platinum mold is used. The cavity o~ the platinum mold corresponds to the outer contour o~ the implan-t. The shell mold is used instead of the nega-tive mold prepared according to Fig. 2 to ~ig. 4; the procedural step~ carried out in Fig. 5 to 11 correspond to those previously described.
'~he above-described procedure can be varied in -that a heap o~ special ceramic rnaterial such as is used ~or the ou-ter layer 6 is applied on -the mold filled wl-th cerarnic substances be~ore the embedding substance 16 is applied. ~his heap can also consis-t of ceramic substances melting be-tween 850 and 1000C, which con-tain an admixture of carbon granules, preferabl~
5 to 20 wt.%, On sintering~ -this heaping effects consolidation of the material in the mold 14 due to a large increase in volume.
r the preparation o~ dental ro~t subs-titutes or artificial teeth pertaining to the original, a negative also true to the original is requiredg from ~hich the dental root substitute or arti~icial tooth can be completed~ The negative must be composed of an embedding substance which if po~sible has only a s~all thermal ability to expand. ~his shouldn't be greater than 1%, ~he negative is made according to the invention as follows :
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-- 29 ~
Before extracting the too-th or -the den-tal root a complete impression o~` the jaw is made. This is followed by extraction of the -too-th or -the dental root. After correc-tion o~ the gwn edges, protruding gt~ being trimmed and flaps being clearecl away 9 and where necessary after deepening the tooth recess by means of a bone cutter (mill), or a so-called "Rosenbohrer" or drill, and stopping the blood flow using a vessel-constric-ting substance, an ela~tic gum impression material is pressed into the tooth recess. By now applying the complete aaw impression which likewise in the region of the e~-tracted too-th is filled wi-th impression materi~l, a "tooth or root positive" can in this way be obtained. After making plaster o~ Paris models the -tooth positive which reproduces the root recess .~nd -the original crown true to shape can be built up to completion in the crown region according to the optima-l gnathologic shapeO
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'72~
~ 20 -Particular advantages are evident from the use of ceramic subs-tances according to the in~ention when these are ~ired as an outer layer onto the implant~
f'ormin~ re~pectlvely a peri.osteum ~ or dental periosteum substitute~ The ceram:ic base substance can here be either a core substance 9 a dentine substance or an enamel substance ? its speci~ic composition being dependant on whether the implant is to be made as metal-ceramic or as hard-ceramic.
~he implants exhibi-t in -this case 9 ~rom the outside -to the inside~ the following layering possibilities:
a) dentine subs-tance wi-th ~ibers ~ired on a core substance without fiber30 b) denti.ne substance with fibers fired on a den-tine substance without ~ibers, which in turn in given cases is ~ired on a core substanceO
c) core substance wi-th .~ibers) fired on a core substance without fibers.
d) enamel substance with fibers, fired on a dentine substance and/or a core substance without fibers.
when the ceramic substances according -to the invention form the outermost layer o~ a bone or dental root implant as bone periosteum-or den-tal root periosteum substitute, it is applied expedientley in thicknesses o~ about O,1 mm to about 5 mm~ preferably in thicknesses o~
about 0,1 mm to abou-t 1 mmO For dental implants the optimal thickness is about Oj~ mm to 0 7 5 mm. The desired vacuoles in this layer, which allow for -the ingrowth of tissue 9 are formed during firing o~ the ceramic subs-tances according to the invention~ provided this doesn't occur under high pressure ~ i~e~ in a vacuum (about 5 - 50 mm Hg~
preferably 10 20 mm Hg~) under atmospheric pres~ure and with small excess pressures~
:, :
~, , ~
- . ' . .
- 21 ~
B ~mplcs for po3~ibilit}~ ef ~r~7ing out the _~pro ing ~rc ~lcccri~ed ill r ~z 11 ~
With higher propor-tion~ of fibers pressures higher than 1 kp/cm2 are necessary in order -to ~void the pores of the fired product becoming too large and the product brittle. If the fibers are metallic ~i~ rs) the flrillg is carried out in a vacuum or in ~ presence of a protective gas in order -to prevent oxidation~ ~s protective gases the noble gases are particularly suitable i~e. Helium, Argon9 Krypton and Xenon, Argon being here the most preferred. If the firing accurs in sealed containers however, this precauting can, possibly be dispensea with. '~he size and number of the vacuoles, -tha-t is the porosity of -the periosteum ~ubs-titu-te layer produced from the ceramic substance according to the invention; can be regulated through the respectlve addition of fibers to the ceramic base substance.
The most suitable mix-tures ~lithin -the given values can be determined for the individual fibers by simple experiments~ ~1hen the vacuoles measure abou-t 10 ~m in diameter to about 300 ~m in diameter and/or in depth, a good ingrowth into the implant in the bone tissue is to be expected, i.e. the new-forming oone tissue grows into the vacuoles and creates a firm contact between bone a~d implant. One can observe this from X-Rays taken at time - intervals of several weeksO The previously-given value~ a~e to be understood as average values, Besides the vacuoles of the given size a large number of small and very small vacuole~ can be in evidence.
~lso the existence of single somewhat larger vacuoles doesn't matter.
.
- , . . .
:
, ~ .
It is particularly u~eful if the previously described cerc~mic substances intended ~or the ou-ter layer of the implant contain additional subs-tances stimulating bone formatlon and/or bone grow-th7 especially -tri-calcium pho3pha-te and tertiary calcium phospha-te.
Substances fur-ther sui-table ~or stimulating bone formation and/or bone growth are in particular sodiumr lithium? carbon9 magnesium9 boron, fluorine, silicon~
phosphorus9 calcium, potassi~m and/or -yttrium ions9 and/or ions of the rare earths, these subs-tances being added in body soluble form. Sodium~ calcillm, boron and phosphorus ions are par-ticularly favourable.
The suitability of these previously-lcnown ions for stimulating -the grow-th of bone ti~sue on-to vl-trified aluminium oxide ceramic is known from -the D~-~S
23 24 867.
In order to stimulate ingrowth into the implan-t i-t is preferable to in-troduce powdered apatite crystals -e.g. ground in a mortar - 9 which are kno~m to strongly accelera-te bone regeneration? into the ceramic substc~nces in-tended for the outer layer o~ the implant. Besides natural bone apa-tite~ apatites being l~omorphic to hydroxylapatite seem e~pecially suitable 9 in particular very small calcium phosphate hydroxylapati-te crystalsO
~he addi-tion involves about 5 to 70 wto % ~ preferably about 10 - 30 wt. Q/O rela-tive to the dry con-tent of -the ceramic substances~ Further substances ~timula-ting bone growth are described in the D~-OS 26 06 540. When ground to a powder they can serve as the additlve me~tioned.
~n addi-tion of denatured bone meal is al~o possible~
~he addition expediently involves about 2,5 wt. % -to about 70 wt~ %~ preferably about 5 wt. % to about 20 wt.
% relative to the dry content of the ceramic substance.
In the following, an ex~mple for the manufacture of denatured bone meal is given :
.. . .
: . , Calves' vertebrae are dried at 100C for 8 hours~ ~he dried bones are coarsely ground and subsequently freed from ~at by lea~ing in ether for 24 hours. ~fter drying o~ the ether the bo~e meal is left 2~ hour~
in 20S~ hydrogrcn peroxide ancl then boiled ~or 10 minutes in same~ The hydrogen peroxide is -then poured off and the material subsequen-tly dried. The powder obtained in -this wa~ from macerated bones is ground very finely in a mortar (this procedure is based on work by R. and ~ Ba~eister - see J. Bone Surg.
39 ~ 153 (t957) )-The Outermost layer of the implants thus preferablycontain an addi-tion of substances stimulat.ing bone ~ormation and/or bone growth, which is added to the ceramic subst~nces be~ore these are mixed to a paste.
Particularly useful here is apatite in powder foxm9 especially calcium phosphate hydroxyl apatite in quan-tities of about 5 to 70 wt. 5~, preferably about 10 to 30 wt. S~ relati~e to the dry conten-t of the ceramlc substancesO In -the following an example is given for the preparation of implants following the method according to the invention.
Fig. 1 showss ln the in-terior o~ a cuvette and ln longltO section, a den-tal root substitute to be implan-ted A
Figo 2 to 11 show schematically the individual steps of an embodiment o~ the preparatory procedureO
The procedures shown in Figso 2 to 11 are primarily intended for the preparation of implants ~Jhich reproduce the extracted teeth or the extrac-ted roots true to shape. These implants should1 in the roo-t region~ be provlded ~rith a porous coating layer having a large number of vacuoles enabling tissue ingrowth and thus rigid suppor-t of the implantO
, . ~
, ~ :
;
- 2~ -The implan-ts are made up o differen-t layers, surrounding one ano-ther9 in a manner similar to the dental prosthetic eLemen-ts prepared by conven-tional porcelain~press techni~1ues or metal ceramic techniques~
~ig. I show~ 7 in the in-terior of a cuvette 9 which in connection with its method of preparation will be dealt with more closely la-ter~ a tooth root substitute 1 in longitudinal sec-tion. ~he tooth root substi-tute 1 consists in -the roo-t region 2 9 seen Erom the in-terior to the e~terior, o~ a core substance 3~ in which a reinforcement element 4 is when necsssary embedded. ~he core subs-tc~lc~ 3 is surro~mded l~yerwlse on the outsicle by a dentine subs-tance 5, which ln turn is surxouncled by a layer 6 of special porous cer~mic substance, ~he layer 6 consists likewise of a dentine subs-tance or core substance which is mixed with thin inorganic fibers whose melting point is considerably higher than the temperature at which the materials making up -the artlflcial tooth 1 are sinteredO The layer 6~ measuring pre~erably abou-t 0 9 3 mm - O,5 mm in thickness is, as -already frequently describedy permea-ted by a large nu~ber of vacuoles 9 these allowing ingrowth of bone ~tissue when -the root region ~ is implan-ted in an ~artlficial or natural -too-th alveolus oE -the ~aw.
~ayers 3 and 5 can9 as a variation from the previous example9 also consist of a dentine, a core substance or aluminium phosphate~
In the example illustrated it is assumed that the dentine substance in layer 5 and 6 is the same. ~or this reason the dividing line represented in the figure between these layers is, in a section through a real artificial too-th or a dental root substitute~ only apparan-t in that within the dividlng line there are no fibers9 meaning that at the dividing line the porosity, or the depth of the vacuole-permeated outer layer9 essentially ends.
~ ~"
, . .
s~
The den-tal root subs-ti-tute 1 can be made from metal-ceramic substances or from hard-porcelain B subs-tances 7 or from ~itadur~ or Vitadur-S-substances, whereby corresponding core substances~ corresponding dentine substances also in layer 6 ~ are usedO
In the case of metal-cer~mic substances the reinforce- ;
men-t element 4 consists of metal~
As metals in questions here one can use, among other special alloys used in metal ceramics, gold alloys with a high platinum content, which for the purpose o~
increased hardness contain iron and o-ther elements and melt at tcmperatures of about 1tO0 - 1200C~ ~lso palladium alloys, hardened ~ith ru-thenium, wlth small amoun-ts of gold or silver, which melt between abou-t 1450C and l600C~ as well as the so-called Feram alloys of cobalt-chrome from the Niranium Corpora-tion Long Island, and D.J. metal wlth nickel as base material of the Durallium Products Co. ahicago. ~he D~-OS 25 14 672 describes further suitable alloys. Fur-ther examples of such alloys are kno~m under the marks Deguden ~and ~egucas~, these being gold-ceramic and being manufactured by the firm Degussa ~ Dental- und Goldhalbzeug D 6000 Frank~urt.
Further gold-ceramics are known under the marks Herado~ (~irm Heraeus9 V.4, Va44) (Firm Métaux Précieux3 Degudent Swiss (Firm Cendres & Metaux) (Armator II) (Firm Uslne Genevoise Degrossissage dlor) Williams Gold, Ceramco Gold and Stern Gold. ~rom among the precious metal refined alloys are mentioned in partieular Wiro~ S and Wiro ~ which have a composition on the basis of nickel-chrome and are manufac-tured by -the firm Bremer Gold-~hlagerei Wilhm. Herbst 2800 Bremen 41 In the case of hard-ceramic substances the rei~forcement element 4 is a prefabrieated hard ceramic elemen-t~
preferably a small hard-ceramic bar, tube or sheet~
preferably of aluminium oxide.
:- :
, ' : ~
In -the following the me-thod of preparation of the dental root substi-tute will be dealt wi-th in more de-tail. Fig, 2 shows how a cuvette half 10 is le~e~
filled with a high-temp embedding subs-tance 12 which has been mixea to a paste. ~he embedding substance should if possible have a small thermal coefficient of expansionO ~xamples of embeddin~ substances are ~ecial substances such as Deguvest from the firm Deg~ssa~ B Dental- und Goldhalbzeug D 6000 Frankfurt 1 J
Wiroves~ from the firm Bego, Bremer Goldschlagerei, Wilh. Herbst 2800 ~remen 419 Emil-Sommer-Str~ 7, Neo-Brilla-t~rom the firm Dentalchemie C.C~ Schrepfer, Marburg /~ahn, Germany, ~urove~ ~or ~uroves~ B, a quarz embedding substance ~rom the firm Bego, Bremer Goldschlagerei, Wilh. Herbst and Hudrovest from the firm Frankonia in West-Germany.
In the embedding substance 12 of the lower cuvette halfy before it hardens, a wax model 13, true -to the origlnal is embedded wi-th the labial or lingual -side do-m as sho~m in Figo 3.
'-, .;:: :
, .
: . . .: .
The wax model 13 is left in the embedding substance 12 un-til this is hardO I-t is -then pulled out again, as shown in ~lg~ ~ so -that a negative mold 14 is formed which is true to shapc ~en the embedding sub~tance is completely dry the ceramic substance, mixed to a paste9 of layer 6 is first applied via the uppex opening 15 of -the mold~
using a brush, spa-tula or ~omething similar. l~hen this in turn is dry9 the adjacent layer 5 is applied~
This stage is sho~n in Fig~ 5. Subsequen-tly~ the cavity remaining in the interior of layers 5 and 6 i5 filled with core substance ~; thi~ is also done preferably in layers. ~he end result is shown in ~ig. 6.
To reinforce the dental root substitute 1 a reinforce-men-t element ~ i9 introduced into the core substance 3.
Fig~ 7 shows this process9 Figo 8 the end result.
Subsequently an upper cuvette half 11 is positioned on top of the lower cuvette half; the upper half is connected to the lower one e.g. by means of pins which slide into holes9 not shown in more detail~ in the lower cuvette. ~he cuvet-te halves are connected such that the high pressure at sintering does not cause the two cuvette halves to be pushed against one anotherO
Positioning of the upper cuvette on the lower one is sho~m in Fig. 9~ The space above the hardened embedding substance 12 and the mold 14 filled with ceramlc substances is subsequen-tly filled completely with further embedding substance 16, ~ixed to a paste~
as is shown in ~ig. 100 lnhen the embedding sub3tance 16 i9 dry the cuvette formed from -the halves 10 and 11 is put into a furnace, i9 sintered there by mean~ o~ heat radiating from a heat source in the direction of arrow S, and is fired as previously described~ The finished dental root substitute 1 is freed after cooling by mechanically destroying the embedding subs-tance. ~fter removal of ridges and projectlng material, the sub~titute , ~ 28 is treated with a sandblast blower~ preferably with very fine corundum9 so -that the pores in -the outer ~yer are opened~
In~te~d of -the two-part cuvette shown in ~igso 2 to 11 it is naturally also possible to use a single cuvette, which is initially only partly ~illed9 preferably to about two thirds 9 with the embedding substance in which~ using a model, a negative mold is made. According to a variant of the preceding method which is especlally suitable for -the preparation of prefabricated implants of the same ~hape, a platinum mold is used. The cavity o~ the platinum mold corresponds to the outer contour o~ the implan-t. The shell mold is used instead of the nega-tive mold prepared according to Fig. 2 to ~ig. 4; the procedural step~ carried out in Fig. 5 to 11 correspond to those previously described.
'~he above-described procedure can be varied in -that a heap o~ special ceramic rnaterial such as is used ~or the ou-ter layer 6 is applied on -the mold filled wl-th cerarnic substances be~ore the embedding substance 16 is applied. ~his heap can also consis-t of ceramic substances melting be-tween 850 and 1000C, which con-tain an admixture of carbon granules, preferabl~
5 to 20 wt.%, On sintering~ -this heaping effects consolidation of the material in the mold 14 due to a large increase in volume.
r the preparation o~ dental ro~t subs-titutes or artificial teeth pertaining to the original, a negative also true to the original is requiredg from ~hich the dental root substitute or arti~icial tooth can be completed~ The negative must be composed of an embedding substance which if po~sible has only a s~all thermal ability to expand. ~his shouldn't be greater than 1%, ~he negative is made according to the invention as follows :
. .
. - . .. , .. . ~ ,.. ... .. ... . .. . .
-- 29 ~
Before extracting the too-th or -the den-tal root a complete impression o~` the jaw is made. This is followed by extraction of the -too-th or -the dental root. After correc-tion o~ the gwn edges, protruding gt~ being trimmed and flaps being clearecl away 9 and where necessary after deepening the tooth recess by means of a bone cutter (mill), or a so-called "Rosenbohrer" or drill, and stopping the blood flow using a vessel-constric-ting substance, an ela~tic gum impression material is pressed into the tooth recess. By now applying the complete aaw impression which likewise in the region of the e~-tracted too-th is filled wi-th impression materi~l, a "tooth or root positive" can in this way be obtained. After making plaster o~ Paris models the -tooth positive which reproduces the root recess .~nd -the original crown true to shape can be built up to completion in the crown region according to the optima-l gnathologic shapeO
Claims (19)
1. Method for the preparation of implants from ceramic substances, especially with a porous surface stimulating the in-growth of bone tissues, comprising: introducing a model of the implant into a high-temperature embedding substance which has been mixed to a paste and leaving it in this until the embedding substance hardens thus producing a negative mold of the implant, said mold being formed with a cavity, removing the model from the mold and lining the mold via an opening reaching into its in-terior with a layer of a ceramic substance which should form the outer layer of the implant, subsequently completely filling the cavity of the mold with dentine or core substances, sealing the opening with a high-temperature embedding substance, which is mixed to a paste, drying the embedding substance and heating the product to the sintering temperature of the ceramic substances used and firing the ceramic substances at this temperature.
2. Method for the preparation of implants according to claim 1, wherein the embedding substance is embedded in a muffle or cuvette which is free of scale.
3. Method for the preparation of implants according to claim 2, wherein the muffle is filled at first to about two thirds with the embedding substance previously stirred to a paste, the model subsequently pushed into the embedding substance from above, and that after filling the negative mold with the ceramic sub-stances the rest of the muffle is filled up with embedding sub-stance.
4. Method for the preparation of implants according to claims 1, 2 or 3, wherein the negative mold is prepared using a wax model of the implant which is burned out after the embedding substance has hardened.
5. Method for the preparation of implants according to claim 1 wherein said mold is formed of a noble metal alloy which is not destroyed at the firing temperature of approxi-mately 1000 to 1500°C.
6. Method according to claim 3, wherein said mold is formed of platinum alloy.
7. Method for the preparation of implants according to claim 1, wherein the outer layer is formed of a ceramic substance having thin inorganic fibers mixed therein, said fibers having a melting point higher than said sintering temperature, said ceramic substance containing a plurality of vacuoles formed there-in for allowing ingrowth of bone tissue.
8. Method for the preparation of implants according to claim 7, wherein the outer layer of the implant is applied to a thickness of about 0.1 to 5 mm, and is prefired, prior to fill-ing up the mold with a dentine or core substance.
9. Method for the preparation of implants according to claim 8, wherein a metal or hard ceramic insert is introduced into the interior of said mold, the insert being an aluminium oxide tube or pin which protrudes above the mold, after which the opening leading to the interior of the mold or shell mold is covered with embedding substance which has been mixed to a paste.
10. Method for the preparation of implants according to claim 7, wherein substances stimulating bone formation and/or bone growth, are added to the ceramic substances forming the outer layer of the implant.
11. Method for the preparation of implants according to claim 10, wherein said substances stimulating bone formation and/or bone growth comprise tri -calcium phosphate and tertiary calcium phosphate.
12. Method for the preparation of implants according to claim 10, wherein the substances stimulating bone growth contain apatite crystals in powder form, in quantities of about 5 to 70 wt. %, relative to the dry content of the corresponding ceramic substances.
13. Method for the preparation of implants according to claim 12, wherein said apatite consists of calcium phosphate hydroxyl apatite.
14. Implant of ceramic substances having a porous outer layer, said outer layer consisting of a ceramic substance having thin inorganic fibers mixed therein, said ceramic substance con-taining a plurality of vacuoles formed therein for allowing ingrowth of bone tissue, said outer layer also comprising sub-stances stimulating bone formation and/or bone growth in a quan-tity of 5 - 70 wt. % relative to the dry content of the ceramic substances.
15. Method for the preparation of implants according to claim 12, wherein said quantities of apatite vary between about 10 and 30 wt. %.
16. Implant according to claim 14, wherein the substances stimulating bone growth contain apatite crystals in powder form, in quantities of about 5 to 70 wt. %, relative to the dry con-tent of the ceramic substances.
17. Implant according to claim 16, wherein said substances stimulating bone formation and/or bone growth are selected from the group consisting of tri-calcium phosphate and tertiary calcium phosphate.
18. Implant according to claim 16, wherein the apatite comprises calcium phosphate hydroxyl apatite.
19. Implant according to claims 16 or 18, wherein said substances stimulating bone growth are used in quantities of about 10 to about 30 wt. %.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000319327A CA1117255A (en) | 1979-01-09 | 1979-01-09 | Method for the preparation of implants, and implants |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000319327A CA1117255A (en) | 1979-01-09 | 1979-01-09 | Method for the preparation of implants, and implants |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1117255A true CA1117255A (en) | 1982-02-02 |
Family
ID=4113275
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000319327A Expired CA1117255A (en) | 1979-01-09 | 1979-01-09 | Method for the preparation of implants, and implants |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1117255A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11872105B1 (en) | 2022-12-01 | 2024-01-16 | Robert Parker | Dental implant device for regeneration of dental pulp and dentin |
| US11931224B1 (en) | 2022-12-19 | 2024-03-19 | Robert Parker | Tooth pod |
-
1979
- 1979-01-09 CA CA000319327A patent/CA1117255A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11872105B1 (en) | 2022-12-01 | 2024-01-16 | Robert Parker | Dental implant device for regeneration of dental pulp and dentin |
| US11931224B1 (en) | 2022-12-19 | 2024-03-19 | Robert Parker | Tooth pod |
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