WO2014202484A1 - Prothèses dentaires - Google Patents

Prothèses dentaires Download PDF

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Publication number
WO2014202484A1
WO2014202484A1 PCT/EP2014/062425 EP2014062425W WO2014202484A1 WO 2014202484 A1 WO2014202484 A1 WO 2014202484A1 EP 2014062425 W EP2014062425 W EP 2014062425W WO 2014202484 A1 WO2014202484 A1 WO 2014202484A1
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WO
WIPO (PCT)
Prior art keywords
prosthesis
dental
thermal treatment
meth
polymers
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Application number
PCT/EP2014/062425
Other languages
English (en)
Inventor
Matteo BIGNAMINI
Andrea PIANTONI
Ugo Romagnani
Sergio Lorenzi
Davide Galletti
Original Assignee
Medlife S.R.L.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Medlife S.R.L. filed Critical Medlife S.R.L.
Publication of WO2014202484A1 publication Critical patent/WO2014202484A1/fr

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C13/00—Dental prostheses; Making same
    • A61C13/0001—In-situ dentures; Trial or temporary dentures

Definitions

  • the present invention relates to dental prostheses and the process for the preparation thereof.
  • the invention relates to dental prostheses obtained starting from a predefinite prosthesis suitable for the preparation of any type of dental prosthe ⁇ sis.
  • a wax prosthesis is prepared with inserted the teeth having prescribed shape and colours.
  • the wax prosthesis is melted, for example in a muffle, while in ⁇ jecting the prosthesis polymer, obtaining the raw prosthesis.
  • the dental practitioner refines, finishes and polishes the dental prosthesis that is then tested in the articula ⁇ tor, in order to regulate bite.
  • the so obtained dental prosthesis is modified as requested by the dentist, for in ⁇ stance by using small bench cutters, to better adapt the dental prosthesis to the patient mouth.
  • the modifica ⁇ tions are more substantial, generally it is preferred to repeat the process and prepare a new prosthesis.
  • the conventional technique requires rather long times. Furthermore each prosthesis must be prepared case by case by the dental practitioner.
  • the denture support can then be assembled in a complete denture by crosslinking a liner of an unpolymerized resin on the inner surface of the support, inserting then teeth on its external surface.
  • a method to produce and adapt a modular prosthesis to the patient mouth comprising the following steps:
  • Heating at the temperature of 57 °C can be obtained by immersion in a warm water bath.
  • the polymerization of the liner can be obtained by hardening through polymerization with various methods, comprising light, heat or chemical reagents.
  • the bond between the liner and the crosslinked support of the prosthesis is such as to stabilize the sup ⁇ port so that it is not deformed when the patient takes food or warm drinks.
  • the teeth can be fixed to the support before or after the pros ⁇ thesis support has been fitted into the patient mouth.
  • USP 5,775,900 describes a transparent stent for diag ⁇ nostic or surgical applications, thermally deformable, that can be inserted on a fully or partially edentulous gum and the surrounding tissues, and a method to produce and fit the stents in the gums.
  • the patent relates furthermore to a kit comprising a stent couple having the above defined characteristics, of which one being the impression of the other, and a temporary prosthesis, thermally deformable like the stent, and a method for its production.
  • the stent and the prosthesis are prepared from a dough mixture having the same composition as that described in USP 5, 304, 063.
  • the stent and the prosthesis When the mixture is heated at temperatures higher than 120°F (49°C) the stent and the prosthesis become malleable and can be shaped in the patient mouth or on a correspond ⁇ ing model, to adapt them to the surfaces of the tissues. More specifically the patent relates to the field of prost- hodontic implants wherein teeth are re-inserted to their place through a fixed or removable implant. For preparing these implants a surgical and/or radiographic stent made of a transparent acrylic resin is used, that in the moulded form keeps a high accuracy degree.
  • the dental practitioner can prepare a surgical and/or ra ⁇ diographic stent and a fully aligned and functioning in ⁇ terim or temporary prosthesis, to take impressions to both dentulous and edentulous patients in order to prepare per- manent prostheses.
  • the purpose of this patent is to elimi ⁇ nate the various steps in the clinic and in the laboratory in the process of preparation of surgical/radiographic stents for implants and temporary prostheses. This is achieved by preparing various stents, wherein the base sizes are respectively small, medium or large, with various tooth arrangements on the base.
  • the stent resin can be dipped in water at 120°-160° F (49°-71°C) to make it de- formable.
  • the base remains stable.
  • the tooth position and aesthetics can be checked and cor ⁇ rected if necessary.
  • the transparent acrylic resin base can be coloured to make it similar to the gum tissue.
  • the ad interim or temporary prostheses, as the stents, can be duipped in water at 49-71°C to make them shaped.
  • the den ⁇ ture can then be molded to fit the correct anatomic con ⁇ figuration of the patient's mouth.
  • teeth are made of acrylic material and mounted on the base.
  • the kit described in the patent is used for diagnostic purposes, see in the block diagram of Fig. 4A of the patent, step 8 that refers to Fig. 4B.
  • temporary prostheses can be prepared for diagnostic use in order to correctly position the teeth of the upper jaw in correspondence with those of the lower jaw and check whether they properly close, that is to control their height.
  • a further diagnostic use is that as surgical guides to establish where to insert the implants in order to insert a new tooth when the natural tooth has been removed.
  • a further diagnostic use is that for radiologic purposes wherein a marker is contained in the base of the stent to position the implants.
  • US patent application 2004/0248065 relates to embodi ⁇ ments comprising either a lower denture or an upper denture without a palate, or a set of dentures containing both the lower and upper denture.
  • the denture comprises a layer of a reline material.
  • These embodiments are adapted to the mouth of the patient by dipping the denture in warm water to sof ⁇ ten the reline material.
  • the temperature of warm water is higher than room temperature (18°-21°C, corre ⁇ sponding to 66-71°F) but lower than 100°C (212°F); or the water temperature can range from 45°C (112°F) to 80°C
  • the dipping time of the material in water, in order to soften the reline material ranges from 2 to 10 minutes. Generally the water temperature can range from 38°C (100°F) to 95°C
  • the thickness of the reline material is in the range from about 1 to about 5 mm, preferably from 1.5 to 3 mm.
  • the prosthesis is adapted inside the mouth and a force is applied on the den ⁇ ture for some minutes. In this time interval the reline ma ⁇ terial conforms to the mouth and to the gum of the patient, thus avoiding both an appointment for taking impressions of the gum and surrounding tissues and returning to the dentist for prosthesis adjustments.
  • This patent application relates to reline materials or products well known on the market, such as for example those sold under the trademark Hydrocast®. These reline materials are inserted in the in ⁇ ner part of the prosthesis to form an adhesive pad to fix the prosthesis. This patent application describes therefore a reline material to let adhere a prosthesis to the gum in order to fix the prosthesis.
  • dental pros theses obtainable starting from a model prosthesis, obtain ⁇ able by polymer moulding starting from a plaster cast of a dental arch, and subjecting the model prosthesis to thermal treatment at temperatures in the range 105°C-250°C under at ⁇ mospheric pressure, the model prosthesis satisfying the following test:
  • a strip having 6X6X80 mm sizes of the polymeric material that forms the model prosthesis takes the external form of a metal cylinder having a diameter of 30 mm and a concavity with a curvature radius of 12 mm and a curvature centre in the Cartesian coordinate system (15 mm, 15 mm), and a convexity with a curvature radius of 8 mm and a curvature cen ⁇ tre in the Cartesian coordinate system (8 mm, 8 mm) ( Figures la and lb), the strip, after being subjected to the above thermal treatment, is adhered to the cylinder and it matches thereof external surface without showing any frac ⁇ ture or crack ( Figures 2a and 2b) by applying a force up to 1 kg weight,
  • the prosthesis obtainable after thermal treatment, shaped or modelled on the dental plaster cast and cooled at room temperature, maintains the shape of the plaster cast;
  • the prosthesis after the thermal treatment, modelling and cooling being subjectable to further cycles of thermal treatment, modelling and cooling for at least 20 times for obtaining further prostheses.
  • the strip of the polymeric material constituting the model prosthesis can be obtained by moulding in a suitable mold sizes.
  • the strip After the test, as said, the strip must not show any fracture and/or cracks. In other words, the strip after having adhered to the external surface of the cylinder must maintain the same features of the initial strip that is fracture-free and/or crack-free.
  • the model pros ⁇ thesis is suitable for use as a dental prosthesis according to the present invention after being subjected to the ther ⁇ mal treatment, modelling and cooling as mentioned above.
  • the force to apply the strip on the cylinder depends on the temperature and on the duration of the ther ⁇ mal treatment. Generally a force ranging between 0.01 and 1 Kg weight is enough to carry out the test.
  • the force gener ⁇ ally can be applied also by using hands.
  • the duration of the thermal treatment depends on the temperature. The higher the temperature the lower the time of treatment.
  • the thermal treatment is carried out for a time comprised between 0.5 and 10 minutes preferably 1 and 5 minutes, more preferably 2 and 4 minutes.
  • the temperature is comprised between 110° and 180°C, more preferably 120° and 170°C for a time pref ⁇ erably from 1 to 5 minutes, more preferably from 2 to 4 minutes .
  • the thermal treatment at the indicated temperatures can preferably be carried out in oven.
  • the thermal treat ⁇ ment can be carried out also in water, but in this case the treatment is carried out under pressure to reach the tem ⁇ peratures comprised in the above mentioned ranges.
  • modelling by modelling (shaping) the model prosthesis on the plaster cast it is meant that the model prosthesis after the thermal treatment carried out for the time and at the temperature requested, is adapted onto the cast by applying a force preferably not higher than 1 kg weight. The force is preferably applied by hands.
  • modelling is car ⁇ ried out as soon as the thermal treatment of the model prosthesis is ended.
  • modeling is started within one minute, preferably within 30 seconds after the with ⁇ drawal of the prosthesis from the oven.
  • modelling is carried out for a time not longer than 5 minutes, pref ⁇ erably 2-5 minutes.
  • model prosthesis it is meant any prosthe ⁇ sis obtainable by moulding a polymer that meets the above mentioned test by starting from a gum plaster cast.
  • prostheses can be preferably obtained with the following process:
  • the cast of the gum is taken by means of a metal impression tray containing a moldable material, preferably of sili ⁇ cone, known also a female;
  • the plaster cast in the laboratory from the female the plaster cast is ob ⁇ tained. Generally the plaster is poured in the cast. This forms the plaster cast;
  • wax is mounted and shaped to conform the gum, then teeth are fixed, obtaining the wax prosthesis;
  • the polymer prosthesis is obtained by dipping the wax prosthesis in a liquid silicone rubber, that is then hardened; after hardening wax is removed and in its place the polymer in the liquid state is poured in the hardened silicone. In this way, after polymer harden ⁇ ing, the model prosthesis is obtained.
  • the model prosthesis can also be obtained by any other process well known in the art.
  • the silicone mould is obtained, the polymeric resin in the liquid state is cast and it is let harden. In this way a copy of the prosthesis is obtained.
  • the prosthesis once subjected to thermal treatment, modelled according to the cast shape and cooled, maintains the cast shape. It has been surprisingly and un ⁇ expectedly found that the prosthesis thus obtained shows neither retractions (shrinkages) or dilatations. This is totally unexpected and surprising as the prosthesis is formed of both thinner and thicker sections. It is besides unexpected and surprising that also the teeth inserted in the model prosthesis do not show alterations and do not de ⁇ tach from the prosthesis polymer during thermal treatment and moulding of the prosthesis on the cast.
  • the prostheses of the invention can be sub ⁇ jected even to 20 or more cycles, even up to 50, each com ⁇ prising thermal treatment, modelling on a cast and subse ⁇ quent cooling after each treatment, to yield further pros- theses having different shapes by using different casts, the latter deriving from different impressions.
  • the prostheses obtained according to the in ⁇ vention can be adapted to different casts. This is an ad ⁇ vantage as the dental arches of an individual change in the time. Furthermore each individual has a different cast.
  • the prosthesis after thermal treatment, modelling and cooling being subjectable to further cycles of thermal treatment, modelling and following cooling for at least 20 times, for obtaining additional different prostheses by us ⁇ ing casts different from that of the model prosthesis.
  • model prosthesis By polymer moulding starting from a plaster cast a model prosthesis can be obtained in a number of specimen even very high, i.e. 100 or more.
  • the invention resides in using the model prosthesis to obtain the prosthesis according to the present claims after having subjected the model pros ⁇ thesis to further cycles of thermal treatment, modelling and following cooling, to adapt the prosthesis to casts different from that of the model prosthesis.
  • the plaster cast is obtainable from an im ⁇ pression that reproduces the shape of a gum as described above, or it can be prepared ex novo in a laboratory by starting from a preexisting cast and making a silicone mould as described above.
  • the model prosthesis could also be obtained by repro ⁇ ducing an existing dental prosthesis by preparing a silicone mould as described above.
  • Fig. la is a perspective view of the metal cylinder used in the test, the cylinder having a diameter of 30 mm and having on its lateral surface a concavity with a curvature ra ⁇ dius of 12 mm and a curvature centre in the Cartesian coor ⁇ dinate system (15 mm, 15 mm), and a convexity with a curva ⁇ ture radius of 8 mm and a curvature centre in the Cartesian coordinate system (8 mm, 8 mm), respectively.
  • Fig. lb is a sectional view perpendicular to the longitudi ⁇ nal axis of the cylinder used in the test of Fig. la.
  • Fig. 2a is a perspective view of the cylinder of Fig. la with attached the polymer strip of the prosthesis of the invention matching the surface of the cylinder including both the convexity and the concavity by applying a light pressure by hands of about 0.4 kg. A visual inspection of the strip shows that its surface does not show any fracture or crack.
  • Fig. 2b is a sectional view perpendicular to the longitudi ⁇ nal axis of the cylinder according to Fig. la with the strip of the polymer of the prosthesis of Fig. 2a.
  • Fig. 3 is a comparative figure showing a model prosthesis as applied to a plaster cast of a dental arch. From the Figure it can be seen that the model prosthesis does not reproduce the cast shape. In this comparative Figure the model prosthesis has not been subjected to heat treatment.
  • Fig. 4 shows the prosthesis of the invention applied to the plaster cast. It can be seen that in this case after thermal treatment of the model prosthesis, modelling on the cast and cooling at room temperature, there is a perfect matching between the plaster cast and the obtained prosthe ⁇ sis.
  • the model prosthesis is substantially formed of one or more polymers.
  • one or more thermoplas ⁇ tic polymers are used provided that they meet the above test.
  • said one or more polymers, preferably thermoplastic can be partially crosslinked with the pro ⁇ viso that a strip from said polymers is such to meet the above test.
  • crosslinking agents those described further on can be used .
  • Additives such as fillers, crosslinking agents, rein ⁇ forcing agents, plasticizers, lubricants, stabilizers, pig ⁇ ments, antiadhesives , antistatic agents, anti UV, antioxi ⁇ dants, polymerization inhibitors, etc., can be added to said polymers.
  • the polymers of the present invention can be selected preferably from the classes of thermoplastic polymers.
  • the ⁇ se classes are exemplified hereinafter.
  • the thermoplastic polymers belong to the class of synthetic resins and derive from the combination of more molecules of one or more chem ⁇ ical compounds.
  • the polymers can be obtained by addition polymerization or by polycondensation .
  • addition polymerization a reaction is meant wherein a number more or less high of molecules of one or more monomers, equal to or dif ⁇ ferent from each other, bind together to form a polymer.
  • a necessary condition for the addition reaction to take place is that the monomer contains only one unsaturation of ethylene type.
  • polycondensation a reaction is meant wherein more molecules of one or more monomers having two functional re ⁇ active groups, bind together to form a macromolecule with elimination of other compounds, for example water.
  • the copolymers are polymers wherein the monomers are different from each other and in the polymer chain the mon- omeric units are distributed, more or less at random, or in a given order.
  • the following types of copolymers can be formed: copolymers with random sequence when the two monomeric units are distributed at random, i.e. without a regular distribution; block copolymers when there are blocks of ra ⁇ ther long sequences of one monomer following those of the other monomer.
  • Copolymers showing an alternate monomer succession are known wherein in the chain the two monomeric units follow one another alternatively.
  • This class of poly ⁇ mers is formed by polycondensation reactions, but it can be obtained also by polymerization reactions, at least with long alternating sequences.
  • Grafted polymers are poly ⁇ mers formed of a long chain of a polymer on which polymeric chains formed of another monomer are grafted.
  • the polymer is stepwise formed. Starting from two bifunctional monomers it can be admitted that at first a simple condensation reaction among them takes place with formation of a dimer that, having two functional groups arranged respectively at the head and tail of the molecule, can react with another monomer mole ⁇ cule forming a trimer. This reacts with another molecule forming a tetramer, and so on, with continuous increase of the molecular weight. If high molecular weight products are desired, it is necessary that polycondensation should proceed efficiently and unrelated substances or impurities that could give rise to secondary reactions, able to inter ⁇ rupt chain elongation, should be not present.
  • Polycondensation is carried out by mixing the monomers with an optional catalyst in reactors well known for this kind of polymerization. Polymerization is carried out under controlled conditions of temperature and sometimes also of pressure .
  • the reaction can be carried out in an aqueous medium, in a solvent or in mass, i.e. by maintaining the compounds in the molten state.
  • the reaction is stopped, generally by cooling .
  • Polymerizations are chain reactions and generally de ⁇ velop as it follows: one molecule of the monomer M is acti ⁇ vated by a catalyst (activation phase) ; the activated mole- cule, that becomes very reactive, combines with another monomer molecule forming a dimer that maintains the activa ⁇ tion and is therefore able to react with another monomer molecule forming a trimer, and so on (propagation phase) . The process continues until an event takes place that de ⁇ activates the molecule (termination phase) .
  • the active centre triggering the start of the reaction can be an ion (cation or anion) or a radical.
  • ion cation or anion
  • radicalic polymerizations ionic (cationic and anionic) polymerizations are known.
  • Radical polymerization takes place when the active centre is formed of a radical, i.e. a group with a free va ⁇ lence, containing one electron valence or an unpaired elec ⁇ tron.
  • a radical i.e. a group with a free va ⁇ lence, containing one electron valence or an unpaired elec ⁇ tron.
  • the start or activation step takes place in the presence of a substance (catalyst) able to generate a radical.
  • Organic peroxides and hydroperoxides show this property.
  • heat ⁇ ed they decompose originating a radical.
  • the radical be ⁇ ing an unsaturated species, quickly reacts with a monomer molecule, forming a radical with an higher molecular weight.
  • the reaction proceeds with the shifting of the un ⁇ paired electron from the radical active centre to the ex ⁇ ternal carbon atom.
  • the so formed radical reacts with another monomer molecule forming a longer radical, and so on.
  • the reaction proceeds with a quick chain increase.
  • the elongation of the polymeric chain does not proceed at the infinite as several events can occur, as said, in ⁇ terrupting the radical sequence.
  • Radicalic polymerizations can be carried out also at low temperature, by operating with initiators decomposing under the effect of energy sources different from heat.
  • initiators decomposing under the effect of energy sources different from heat.
  • azodiisobutyronitrile can be used as a photoinitia- tor as it decomposes into radicals also at low tempera ⁇ tures by irradiation with ultraviolet light;
  • redox initia ⁇ tors can be used, i.e. redox systems, causing the decompo ⁇ sition of the peroxide by means of a reducing agent.
  • a re ⁇ dox system used in emulsion polymerizations is for example formed of hydrogen peroxide and F e ++ ions.
  • Another example of redox iniziator is formed of persulphate ion in the presence of a reducing agent as thiosulphate or bisulphite.
  • the active centre is formed of a positive electric charge, i.e. a cationic group. Also in this case the reaction proceeds according to the above mentioned three steps.
  • cationic polymerizations take place in the presence of initiators (catalysts) having the property of releasing easily a cation.
  • initiators are the so called Lewis acids as BF 3 , SnCl 4; A1C1 3 , AlBr 3 , TiCl 4 and some strong acids as H 2 S0 4 and HF.
  • the Lewis acids require the presence of a co- catalyst such as water, alcohol, acetic acid.
  • the formed ion reacts with another monomer molecule giving a dimer cation and so on.
  • the reaction quickly proceeds by adding further monomer molecules obtaining one polymer ion.
  • the termination phase occurs because various events take place that stop polymerization, in particular the fol- lowing ones: the transfer of one proton from the polymer to a monomer molecule, starting the formation of a new polymeric chain, or the transfer of a proton from the polymer to the anion of the catalyst.
  • the cationic process allows to carry out very quick polymerizations even at very low temperatures, obtaining in a few seconds a mo ⁇ lecular weight of some millions.
  • different monomers can be polymerized in the presence of substances generating an an ⁇ ion initiator, such as for example sodium amide NaNH 2 , potassiumamide KNH 2 or alkyl metals.
  • an ⁇ ion initiator such as for example sodium amide NaNH 2 , potassiumamide KNH 2 or alkyl metals.
  • the reaction starts with the formation of a negative ion from the catalyst, the anion then reacts with a first monomer molecule and the propagation phase then starts.
  • the polymerization is carried out in an homogenous or heterogeneous phase: in an homogeneous phase according to the mass and solution polymerization, in an heterogeneous phase according to emulsion and suspension polymerization.
  • gaseous monomers and liquid monomers for example methyl methacrylate, styrene are po ⁇ lymerized without addition of solvents and by operating in the presence of the catalyst under suitable conditions of temperature and pressure.
  • the monomer is dissolved in a solvent and the catalyst is added to this solution.
  • the polymer can be separated by evaporating the solvent together with the unreacted monomer, or by precipi ⁇ tating the polymer by adding a suitable coagulating agent.
  • the monomers insoluble in water such as for example vinyl monomers, styrene, etc.
  • emulsifying agents such as for example vinyl monomers, styrene, etc.
  • the monomer is mixed with wa ⁇ ter and the emulsifying agent is added so that a monomer aqueous emulsion is formed.
  • initiators peroxides or re ⁇ dox initiators are used.
  • latex a polymer emulsion, called latex, is obtained, from which the polymer can be recovered by coagulation by adding an electrolyte.
  • the reaction proceeds under sub ⁇ stantially isothermal conditions, as sufficient amounts of water are present to disperse the reaction heat; further ⁇ more high polymerization speeds, high and reproducible mo ⁇ lecular weights, are obtained.
  • the polymerization in suspension or in beads takes place when the emulsifying agent is in a reduced amount or it is absent. In these cases an aqueous suspen ⁇ sion is obtained.
  • the monomer collects in beads having a larger diameter than in the case of the emulsion oily particles.
  • the bead sizes can also be of the order of some millimeters, and are kept in suspension by mechanical stir ⁇ ring.
  • small amounts of stabilizers as for example gelatine, starch, bentonite, are added.
  • the polymerization process has a statistical nature since not all the monomer molecules polymerize with the same speed and the formed polymeric chains have not the same length. For this reason the obtained resins are never formed of only one chemical compound but of a mixture of polymeric chains having a different polymerization degree. As many physical and chemical properties depend on the po ⁇ lymerization degree, it is sometimes necessary to carry out a separation or fractionation to separate the obtained product into fractions each having molecular weights com ⁇ prised in a limited range, or to isolate the fraction hav ⁇ ing the desired molecular weight. In polymer fractionation the principle is usually applicable that generally the sol ⁇ ubility in a given solvent decreases with increasing mo- lecular weight.
  • the method consists in a fractional pre ⁇ cipitation from a diluted solution of the polymer, by using as precipitating agent a non-solvent agent. In this way the less soluble fractions, those having a higher molecular weight, are preferably precipitated.
  • Another method for polymer fractionation consists in mixing the product obtained from polymerization with a solvent favouring the solubilization of the low molecular weight fractions. This method is called fractionatal ex ⁇ traction .
  • Plastic materials are produced under the form of pow ⁇ ders or granules, tablets, beads, pellets, etc.
  • plastic articles for the preparation of the various plastic articles (moulding) they are mixed with some auxiliary ingredients, then moulded by using different equipments in relation to the type and the article to be prepared.
  • the auxiliary ingredients are substances added and mixed with the resins before moulding, and sometimes they are already incorporated in the moulding powders.
  • the aux ⁇ iliary ingredients comprise the above indicated additives herein described in more detail.
  • the fillers or charges are used to improve the me ⁇ chanical and electric properties. They are used in amounts up to 50% by weight of the formulation. Fillers are both organic and inorganic compounds. Among the former, wood flour, cotton, jute or cellulose fibers (meth) acrylic poly ⁇ mers; among inorganic fillers diatomaceous earth, mica, graphite, glass, can be mentioned.
  • the organic fillers im ⁇ prove some mechanical properties, in particular resilience, while they slightly worsen tensile and flexural strength and are uninfluential on heat resistance and electric prop ⁇ erties.
  • the reinforcing agents are materials having a fibrous structure, such as cotton, but above all glass fibers, felt, short fibers, fabrics, etc. With the reinforcing agents the so called reinforced plastic materials and plas ⁇ tic laminates are prepared, wherein these additives act as a support for the resin and remarkably increase the me ⁇ chanical properties thereof.
  • Plasticizers are used in thermoplastic polymers for reducing rigidity and increase flexibility thereof.
  • the plasticizers most commonly used are for example phosphates of higher alcohols, such as trioctylphosphate and tricre- sylphosphate, or glycerine esters such as the corresponding diacetate and triacetate, esters of polyethylenglycols , oleates, stearates, ricinoleates .
  • Mixtures of plasticizers are generally used.
  • Lubricants are used in order to improve the sliding characteristics of thermoplastic polymers and thus to make it easier thereof processing.
  • metal soaps for example calcium, zinc, magnesium stearates and oleates, or amyl and butyl stearates, are used.
  • the amounts of these additives are generally lower than 1% by weight.
  • Stabilizers are additives which prevent or limit resin degradation due to agents as light, heat, oxygen.
  • metal soaps wherein the organic acid is usually selected from the following: stearic, lauric, ricinoleic, benzylic acid and phenol.
  • the cation is generally a metal selected from the following: barium, cadmium, calcium lead, tin, zinc.
  • organic phosphites are added. Also stabilizers different from soaps and totally organic can be used, in particular substances containing epoxy groups .
  • Plastic materials can be coloured with pigments or with organic dyestuffs dissolved or dispersed in the plas ⁇ tic mass during processing.
  • the dyestuff must have specific properties, such as easy dispersibility in the resin, ther- mal stability, light stability, toxicity free.
  • antiadhesives which are directly applied by brushing or by spraying onto the mould surface to make it easier the detachment of the moulded article.
  • antiadhesives are silicone oils and cellulose resins, that are applied in films or in thin layers by painting.
  • Hardening agents are catalysts added when the polym ⁇ erization must take place or be completed at the applica ⁇ tion site.
  • Crosslinking agents are generally crosslinking comono- mers added during polymerization. These comonomers, con ⁇ taining at least two double bonds, are added in amounts comprised between 0 and 2%, preferably between 0 and 1% by weight with respect to the total monomer amount.
  • crosslinking comonomers are ethylenglycol di (meth) a- crylate, di-, tri-, tetraethylenglycol di (meth) acrylate, 1,3- 1 , 4-butylenglycol di (meth) acrylate, 1 , 6-hexandiol di (meth) acrylate, 1 , 9-nonandiol di (meth) -acrylate, divinyl- benzene, trivinylbenzene, allyl (meth) acrylate, diallyl ma- leate, diallyl fumarate, triallyl cyanurate, pentaerythrol triacrylate; trimethylolpropane tri (meth) -acrylate, etc.
  • (meth) acrylic acid, glycidol (meth) -acrylate, (meth) acrylamide can be used as crosslinking agents .
  • thermoplastic powders The processing of moulding thermoplastic powders is carried out by loading them onto the mould and then heating so that the powders melt and become fluid, until filling all the mould cavities. Before discharging from the mould the resin is cooled and solidified.
  • the resin In injection moulding the resin is loaded by a hopper; the resin is compressed by a piston and thus get heated. The resin is softened and loaded onto a mould and takes thereof shape while cooling.
  • plastic materials obtained by polycondensation the following ones can for example be mentioned.
  • Polyester resins derive from the polycondensation of acids with alcohols.
  • polyester resins There are several kinds of polyester resins.
  • saturated polyesters in general, that are ob ⁇ tained by condensation of bicarboxylic saturated acids with a saturated bivalent alcohol.
  • the acid can be selected for ex ⁇ ample from the following: saturated acids, for example phthalic acid and isophthalic acid; the alcohol can be se ⁇ lected from ethylene glycol, propylene glycol or butylene glycol .
  • Glycols having a longer chain such as dipropylene glycol and triethylene glycol can also be used.
  • Epoxy resins are prepared by polyaddition of an epoxide, in general epichlorohydrin, with a phenol. The epoxy groups react again with phenol and epichlorohydrin and then the reaction proceeds up to the formation of polymers having a lin ⁇ ear structure and high molecular weights. By varying the op ⁇ erating conditions the molecular weight can be adjusted, ob ⁇ taining products having a low polymerization degree (liquid resins) or a high polymerization degree (solid resins) . Epoxy resins are therefore linear and thermoplastic; thereof chains however contain a great number of very reactive groups, hy- droxyl groups -OH and epoxy groups.
  • the chains can therefore react with each other or with other bifunctional compounds to form high molecular weight tridimensional insoluble complexes that do not melt and show a high hardness.
  • hardening agents can be of two types: catalytic hardeners that catalyze only the reaction between two epoxy groups, and reactive hardeners which instead take an active part in the process.
  • Catalytic hardeners are for example tertiary amines and boron trifluoride. These substances are able to cause an ionic po ⁇ lymerization among epoxy groups.
  • Reactive hardeners are in particular primary and secondary amines, organic acids, i.e. substances able to react with both hydroxyl groups and epoxy groups .
  • polyurethane resins are for example polyurethane resins.
  • Polyurethane resins are prepared from alkyl diisocy- anates by reaction with glycols, to obtain thermoplastic lin ⁇ ear polyurethanes .
  • An example of a glycol that can be used is butylene glycol.
  • the most used isocyanates are for example phenylene diisocyanate and hexamethylene diisocyanate .
  • Plas ⁇ tic materials obtained by polymerization reaction preferably comprise acrylic resins, obtained from the polymerization of vinyl monomers .
  • acrylic resins polyacrylic resins, acrylic (co) polymers, polymers obtained by using as monomers the de ⁇ rivatives of the acrylic and methacrylic acids, such as for example alkyl (meth) acrylates, acrylic nitriles, etc., sepa ⁇ rately or in admixture with each other, are meant.
  • the polymerization of acrylic esters is carried out in mass, in suspension or in aqueous emulsion.
  • organic peroxides or potassium or ammonium persulphate and hydrogen peroxide are used as catalysts.
  • the polymerization in mass is carried out by heating the monomer in the presence, for example, of benzoyl peroxide.
  • the mass is then poured in moulds wherein polymerization is completed. After cooling, the manufactured article is dis ⁇ charged.
  • polymerization is carried out in aqueous suspension in the presence of perox ⁇ ides, for example benzoyl peroxide; the formed beads are separated by centrifugation or filtration, then mixed with additives and milled.
  • perox ⁇ ides for example benzoyl peroxide
  • Emulsion polymerization can be used to obtain acrylic resins as moulding powders.
  • the manufactured articles based on polymethacrylic res ⁇ ins have a high transparence, a remarkable mechanical and chemical resistance, and can be coloured with colorants.
  • acrylic (co) polymers derive from poly ⁇ merizable monomers and can be obtained, as said, by polymer ⁇ izing polymerizable suspensions of said monomers.
  • Fluid suspensions can be prepared by mixing
  • filler can be an organic or mineral compound.
  • Organic fillers are for example polymers, preferably (meth) acrylic polymers.
  • fluid suspension comprising an inorganic filler
  • inorganic filler is the following:
  • an hydrolysis catalyst of the silanizing agent selected from ammonium salts of organic acids.
  • Polymerizable monomers are selected from alkyl or hydroxyal- kyl esters of acrylic or methacrylic acid wherein the alkyl group contains from 1 to 8 carbon atoms, preferably from 1 to 6 carbon atoms, or amides, and mixtures thereof.
  • esters are methyl (meth) acrylate (MMA) , ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) - acrylate, tert-butyl (meth) acrylate, sec-butyl (meth) - acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (me ⁇ th) acrylate, (meth) acrylamide .
  • MMA methyl (meth) acrylate
  • ethyl (meth) acrylate propyl (meth) acrylate
  • butyl (meth) - acrylate tert-butyl (meth) acrylate
  • sec-butyl (meth) - acrylate sec-butyl (meth) - acrylate
  • hydroxyethyl (meth) acrylate hydroxypropyl (me ⁇ th) acrylate
  • another monomer can optionally be added, having only one double bond polymerizable by radicalic route, in an amount in general not higher than 80%, preferably not higher than 50% by weight, such as for example, styrene, alpha- methylstyrene, (meth) acrylonitrile, N-alkyl or N- arylmaleimides , having respectively an alkyl from 1 to 10 carbon atoms and an aryl from 6 to 12 carbon atoms.
  • the preferred acrylic (co) polymers are those contain ⁇ ing methylmethacrylate for at least 70% by weight and me- thylmethacrylate copolymers with esters of the acrylic acid, preferably ethyl or methyl acrylate.
  • Methylmethacrylate is particularly preferred. It can be used alone to yield polymethylmethacrylate or in admix ⁇ ture with other vinyl monomers.
  • vinyl monomers styrene, alpha-methyl styrene, etc., can be mentioned.
  • mineral fillers can be used, as inorganic substances having hydrophilic sur ⁇ faces characterized by the presence of polar groups, pref ⁇ erably of hydroxyl type, capable to react with a silaniz- ing agent present on the filler.
  • inorganic fillers amorphous and crystalline silica (quartz, cristobalite, etc.), glass, alumina, trihydrate aluminum, calcium carbon ⁇ ate, mineral silicates, alumino silicates (mica, talc, wol- lastonite, etc.) mineral oxides as Fe 2 0 3 , Ti0 2 , etc. can be mentioned.
  • the filler particles have a granular or spheroidal shape.
  • the average diameter of the particles is generally comprised between 0.1 and 50 ym and the surface area between 0.5 and 10 m 2 /g.
  • the amount of mineral filler to be used in the compositions de ⁇ pends on the desired characteristics of the final manufac ⁇ tured articles and on the fluidity property of the suspen ⁇ sion.
  • the amount of fillers ranges from 30 to 80% on the total suspension. The remaining part is formed of polymerizable monomers.
  • the silanizing agent is an organic derivative of sili ⁇ con containing hydrolysable groups.
  • the silanes that can be used are for example the fol ⁇ lowing: methyltriethoxysilane, methyltrimethoxysilane, vin ⁇ yltriethoxysilane, ⁇ -methacryloxypropyltrimethoxysilane, ⁇ -methacryloxypropyltris ⁇ 2-methoxyethoxy) silane, ⁇ -glycid- oxy propyl-trimethoxysilane, ⁇ -mercaptopropyl triethoxysi- lane, ⁇ -aminopropyltriethoxysilane, ⁇ - ⁇ ⁇ aminoethyl) ⁇ -amino propyltrimethoxysilane, etc.
  • the silane hydrolysis catalyst is selected from ammo ⁇ nium salts of organic acids having general formula
  • R 4 is a hydrogen atom or an alkyl, cycloalkyl, alky- laryl, optionally unsaturated, radical C1-C20, R5, 7, Re, equal to or different from each other, can be hydrogen or alkyl or cycloalkyl C 1 -C 20 radicals.
  • catalysts are isopropylammonium acetate, isopropylammonium methacry- late, ammonium oleate, ammonium stearate, ammonium methacrylate, n-propylammonium methacrylate, dimethyl- ammonium butyrate, isopropylammonium oleate, isopropylammo ⁇ nium benzoate, ethylammonium acrylate, etc.
  • the silane compound is used at concentrations from 0.01% to 2% by weight with respect to the filler and the catalyst between 0.01% and 1% by weight with respect to the whole composition weight.
  • surfactants soluble in the monomer and having suitable affinity with the mineral filler can also be added.
  • surfactants containing ethoxy or propoxy groups such as ethoxylated alkylphenols , sulpho- nates, alkyl sulphates, phosphates and alkylammonium phos- phonates, wherein the alkyl group has up to 20 carbon at ⁇ oms, phosphoric esters, etc., are used.
  • Examples of surfac ⁇ tants are ethoxylated nonylphenol containing from 1 to 15 ethylenoxide molecules, ethoxylated octylphenol containing from 1 to 15 ethylenoxide molecules, ammonium dodecylben- zensulphonate, sodium 2-ethylhexylsulfosuccinate, ammonium and laurylalcoholethoxylated, with 1-3 ethylenoxide mole ⁇ cules sulphate, C 4 -Ci 2 alcohol phosphates, acid phosphates of stearamidopropyldimethyl ⁇ -hydroxy ethyl-ammonium, etc.
  • the surfactant amount is in the range 0-0.5% by weight with respect to the whole composition weight, preferably 0.05- 0.2%.
  • additives can be added, in particular pigments and/or inorganic and/or organic dyestuffs, in amounts between 0 and 5% by weight on the total; agents to ease detachment from the moulds, anti ⁇ static agents, plasticizers, anti UV agents, antioxidants, polymerization inhibitors, etc. in amounts between 0 and 2% by weight on the total. See for example those mentioned a- bove .
  • the viscosity of the suspension can be increased and brought to the optimum level for injection moulding or for mass polymerization by addition of viscosity modifiers, such as for example methacrylic or vinyl homo and/or co ⁇ polymers.
  • viscosity modifiers such as for example methacrylic or vinyl homo and/or co ⁇ polymers.
  • Generally compounds having a high molecular weight are used; for example polymers or copolymers with average molecular weight (Mw) comprised between 20,000 and 1,000,000, and preferably between 50,000 and 500,000.
  • viscosity modifier polymers are polymethylmethacrylate, methylmethacrylate-methylacrylate copolymers, methylmethacrylate-styrol copolymers, methyl- methacrylate-butylacrylate copolymers, polyethylmeth- acrylate, methylmethacrylate-methacryloxypropyltrimethoxy silane, etc.
  • the viscosity modifiers are added in an amount by weight not higher than 20% with respect to the monomer, preferably 0.5-10%.
  • the transformation into manufactured articles of the polymerizable suspensions can be carried out by moulding by applying a pressure comprised between 1 and 4 atm and at temperatures from 70° to 100°C for closed moulds, upon pre ⁇ vious addition of a catalyst, preferably peroxidic, in amounts generally in the range from 0.1 to 2% by weight.
  • a catalyst preferably peroxidic
  • examples of these catalysts are benzoylperoxide or t- butylcyclohexylperoxycarbonate .
  • agents to favour the detachment from the moulds such as for example stearic acids, glycerine monostearate, etc., can be added.
  • acrylic (co) polymers having good me ⁇ chanical properties can be used as polymers for preparing the prostheses of the pre ⁇ sent invention. These polymers are pre- pared by using compositions based on acrylic (co) polymers having shock-resistant properties, such as for example de ⁇ scribed in EP 270,865, USP 3,985,703. These flexible mate ⁇ rials, in particular those described in the EP patent, are obtained by mixing acrylic (co) polymers with a shock- resistant additive in an amount equal to 20% by weight or even higher. Examples of compounds used as shock-resistant additives are for example core-shell emulsions having a resin core, an intermediate layer of acrylic rubber and an external layer of (meth) acrylic resin.
  • the core can be formed for example of a crosslinked acrylic polymer and the intermediate layer is formed of a crosslinked elastomeric copolymer having a Tg lower than 25°C, preferably lower than -10°C; the external layer is formed of (meth) acrylic resin grafted to the rubber.
  • a typical composition of shock-resistant acrylic (co) polymers comprises:
  • thermoplastic resin formed of acrylic (co) polymers
  • a polymer having a multilayer structure comprising:
  • thermoplastic acrylic resin as defined
  • a first layer surrounding the central core constituted by a crosslinked elastomer butyl acrylate/styrene 85/15.
  • shock-resistant additives of acrylic (co) polymers elastomers having a very low Tg can be used. In this way in the compounding phase it is possible to use amounts of ad ⁇ ditive lower than the above indicated 20%.
  • Acrylic copolymers as described above having abrasion resistance comparable with that of acrylic (co) polymers can also be used. They can be used for example in the following compositions :
  • thermoplastic resin based on acrylic homopolymers or co ⁇ polymers as defined above wherein at least 20% by weight, preferably at least 50% by weight is formed of (meth) acrylic monomers.
  • the elastomeric component being dispersed in the acrylic resin as spherical particles and/or elongated particles having diameter, measured by electronic microscopy (TEM transmission electronic microscopy) , comprised between about 10 nm and about 2, 000 nm, the particles of the elas ⁇ tomeric component optionally including acrylic resin parti ⁇ cles .
  • TEM transmission electronic microscopy TEM transmission electronic microscopy
  • the preferred acrylic (co) polymers of the thermoplas ⁇ tic resin are those containing methylmethacrylate for at least 70% by weight, as PMMA and methylethacrylate copoly ⁇ mers with (meth) acrylic acids or esters thereof, preferably ethyl, methyl, butyl acrylate or (meth) acrylic acid.
  • the elastomers are obtainable for example by polymer ⁇ izing one or more (co) monomers selected from the following groups :
  • acrylic acid esters wherein the alkyl group has from 1 to 16 carbon atoms, preferably from 2 to 12 carbon atoms, such as ethyl acrylate, propyl acrylate, isopropyl acry ⁇ late, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, etc . ,
  • alkoxy-alkyl acrylates wherein the total number of the carbon atoms between the alkyl group and the alkoxy group is in the range 2-16, preferably 3-15; such as for example 2-methoxyethyl acrylate,
  • vinyl monomers for example styrene and derivatives thereof, such as for example methyl- and ethyl-styrene, wherein the alkyl group is in ortho or para position; -me- thylstyrenes ; mono-, di-, tri-, tetra-, penta- halogenostyrenes , wherein the halogen is selected from CI, F; said monomers being in amounts not higher than 40% by weight, preferably not higher than 30% by weight on the to ⁇ tal amount of the monomers of the elastomeric component.
  • the preferred elastomer is the copolymer of butyl or 2-ethylhexyl or octyl acrylate containing styrene in amounts comprised between 5 and 30% by weight, preferably between 10 and 20%.
  • compositions under the form of beads can be pre ⁇ pared by a suspension polymerization process comprising the following steps:
  • step 2) polymerization in the same polymerization suspension containing the elastomer beads obtained in step 1), of (co) monomers of the acrylic polymer, said (co) monomers be ⁇ ing selected from those indicated above.
  • a preferred process for suspension polymerization, preferably aqueous suspension polymerization, of the above monomers is carried out in the presence of a radical ini ⁇ tiator soluble in the monomers and of a suspending agent to stabilize the suspension.
  • a radical ini ⁇ tiator soluble in the monomers and of a suspending agent to stabilize the suspension.
  • inorganic and organic suspending agents can be mentioned.
  • poly ⁇ meric organic compounds such as polyvinylalcohol , acrylic copolymers containing a (meth) acrylic acid, carboxymethyl- cellulose etc., can be mentioned.
  • the beads obtained with the above described suspension polymerization process, after washing with water and drying, are compounded (see above) , preferably by extrusion, in order to obtain granules.
  • suspending agents the following are men ⁇ tioned :
  • Rl H or CH 3 ;
  • R2 and R3, equal to or different, are H or Ci-C 8 alkyls optionally branched when possi ⁇ ble;
  • M is an alkaline or alkaline-earth metal or ammonium and
  • A is NH, oxygen or NCH 3 ,
  • the amount of the suspending agent is in the range 0.1 - 1.5%, preferably 0.2 - 1% by weight, referred to the total weight of the aqueous phase.
  • ratios by weight between the aqueous phase and the monomers generally comprised between 1.5:1 and 20:1, preferably from 2:1 to 10:1 are used, in the presence of a radical polymerization initiator soluble in the monomer.
  • the presence of a chain transfer agent is not requested.
  • the reaction temperatures are those at which the initiator decomposition occurs, and are generally comprised between 50°C and 120°C.
  • aqueous phase/monomers ratios by weight generally comprised between 1:1 and 10:1, preferably between 1.4:1 and 6:1, are used in the presence of a chain transfer agent and a radi ⁇ cal polymerization initiator, both selected from those soluble in the monomer.
  • the reaction temperatures are those at which the initiator decomposes and are generally in the range 50°C-120°C.
  • radical initiators peroxides such as for example dibenzoylperoxide, t-butylperoxydiethyl acetate or unstable azocompounds , such as for example azodiisobutyronitrile, can be mentioned.
  • alkylthiols with a linear or when possible branched alkyl group C 3 -C 2 o, preferably C4-C 12 such as for example n-butanthiol , n-octanthiol , n- dodecanthiol , ter-dodecanthiol , cyclohexanthiol , pinan- thiol, can be used.
  • suspending agents of formula (I) or their copolymers with acrylic monomers are described in pa ⁇ tent application EP 457,356 herein incorporated by refer ⁇ ence.
  • the suspending agents of formula (I) can be, for example, sodium 2- (meth) acrylamido-2- methylpropansulphonate, sodium 2-acrylamidopropan- sulphonate, sodium 2-acrylamido-2-ethansulphonate .
  • the acrylic monomers that can be copolymerizable can be for example (meth) acrylamide, alkaline or alkaline-earth salts of the (meth) acrylic acid, (meth) acrylic acid esters with a C 1 -C4 aliphatic alcohol, acrylonitrile .
  • crosslinking comonomers containing at least two double bonds can be added in polymerization.
  • crosslinking comonomers are ethylenglycol di- (meth) acrylate, di-, tri-, tetraethylenglycol di (me ⁇ th) acrylate, 1,3- 1 , 4-butylenglycol di (meth) acrylate, 1,6- hexandiol di (meth) acrylate, 1 , 9-nonandiol di (meth) acrylate, pentaerythrol triacrylate, trimethylolpropane tri (meth) - acrylate etc.
  • Crosslinking agents containing a functional polar group can also be used in a percentage from 0 to 2% by weight on the total weight of the monomers; examples of these monomers are (meth) acrylic acid, glycidyl (meth) acrylate, (meth) acrylamide .
  • crosslinking can also be carried out without addition of a crosslinking mon ⁇ omer when acrylic esters are used as comonomers, wherein the alkyl has a number of carbon atoms higher than or equal to 4, preferably C 4 -Ci 0 , for example butyl acrylate, 2- ethylhexyl acrylate, n-octyl acrylate.
  • the polymers used for preparing the prostheses of the present invention meet the requirements established by the sanitary regulations for their clinical use, in the first place absence of toxicity.
  • the prostheses of the present invention preferably comprise, or are formed of, acrylic (co) polymers, prefera ⁇ bly the acrylic polymer used to prepare the model prosthe ⁇ ses on the market, i.e. the prostheses that have not been treated according to the process of the present invention.
  • a preferred process for preparing the prostheses of the present invention is carried out by mixing an acryl ⁇ ic (co) polymer in powder form, for example polymethylmethacrylate (PMMA) alone or in admixture with other acrylic polymers, with a liquid acrylic monomer, for exam ⁇ ple methylmethacrylate (MMA) .
  • PMMA polymethylmethacrylate
  • MMA liquid acrylic monomer
  • the powder contains, besides the polymer, a plasti- cizer different from phthalate, initiators such as for ex ⁇ ample peroxides, and pigments.
  • the liquid in addition to MMA, contains a crosslink- ing agent, for example ethylenglycol dimethacrylate and a catalyst, for example a peroxide, see also above for these components .
  • a crosslink- ing agent for example ethylenglycol dimethacrylate
  • a catalyst for example a peroxide
  • a product available on the market has the following composition (% by weight)
  • Powder polymethylmethacrylate 95.5, plasticizer (different from phthalate) 3.8, initiators 0.6, pigments 0.1.
  • Liquid phase methylmethacrylate 95.9, crosslinking agent 4.0, catalyst 0.1.
  • Mixing is carried out for a time not longer than 30 seconds, preferably lower than 10 seconds.
  • the process is carried out at temperatures in the range from 70°C to 40°C or lower and, if desired, also down to room temperature.
  • pressure is ap ⁇ plied, generally not higher than 5 atm and not lower than 2 atm, preferably between 4 and 2 atm.
  • the weight ratios pow ⁇ der/liquid are generally from 1 (powder) : 1 (liquid), up to 4:1, preferably 1:1 to 2:1.
  • the polymerization time depends on the temperature and pressure used. Generally it is lower than one hour, pref ⁇ erably not longer than 30 minutes. For example, by operat ⁇ ing at 4 atm at 40°C, the polymerization time is about 15 minutes .
  • a further object of the present invention is a process for preparing dental prostheses comprising the following steps :
  • the obtained prosthesis can be subjected to further processes comprising steps a) -d) , by using different plas ⁇ ter casts of dental arches, for at least 20 times, in order to obtain other prostheses of different shapes.
  • room temperature it is meant a temperature in the range 15° - 25°C.
  • the heating time is generally comprised be ⁇ tween 0.5 and 10 minutes, preferably 1 - 5 minutes, more preferably 2 - 4 minutes.
  • step a) preferably temperature is in the range 110°-180°C, more preferably 120°-170°C; the heating time preferably ranges from 1 to 5 minutes, more preferably from 2 to 4 minutes.
  • step b) the prosthesis is transferred on the plas ⁇ ter cast of a dental arch immediately after the end of the heating step a) , preferably in a time not higher than 1 mi ⁇ nute, more preferably in a time not higher than 30 seconds.
  • step c) the force applied is preferably comprised between 0.1 and 1 Kg weight.
  • step d) the prosthesis is preferably allowed to cool in air down to room temperature.
  • a further object of the present invention is the use of the dental prostheses of the invention obtainable from the model prosthesis according to the above described proc ⁇ ess, to obtain other prostheses by subjecting the prosthe ⁇ ses of the invention to steps a) -d) of the above described process (i.e. a treatment cycle), but using in step c) each time a different plaster cast.
  • a strip 6X6X80 mm of the polymeric material forming the model prosthesis takes the external form of a metal cylin ⁇ der having a diameter of 30 mm and a concavity with a curvature radius of 12 mm and a curvature centre in the Carte ⁇ sian coordinate system (15 mm, 15 mm), and a convexity with a curvature radius of 8 mm and a curvature centre in the Cartesian coordinate system (8 mm, 8 mm) (Figs, la and lb) .
  • the strip after being subjected to the thermal treatment at temperatures in the range 105°C-250°C under atmospheric pressure, by applying a force up to 1 kg weight is let ad ⁇ here to the cylinder and it reproduces the external surface thereof without showing any fracture or cracks.
  • a composition for prosthetic bases is used, formed of two components: a powder, essentially constituted by an acrylic polymer and a liquid, substantially constituted by an acrylic monomer.
  • the composition is commercialized with the trade- mark Sintodent®.
  • the two components of the composition are mixed in a ratio by weight solid component/liquid component of about 1.4. It is noticed that after mixing the mixture swells and a mal ⁇ leable mass like a paste is obtained. Mixing is carried out with a spatule for 5 seconds. The mould reproducing the form of a strip 6X6X80 mm is filled with the malleable mass by the aid of a spatule. The mould is heated for 15 minutes at 40°C under a pressure of 4 atmospheres. It is let cool at room temperature and the strip is removed from the mould .
  • the obtained specimen is subjected to thermal treatment at 140°C for 4 minutes under atmospheric pressure in an oven and is then submitted to the above described test.
  • the strip is applied to the cylinder lateral surface by the aid of a light pressure by hands of about 0.4 kg weight (4 Newton) . It is observed that it perfectly matches the sur ⁇ face of the cylinder.
  • the test results are shown in Figs. 2a and 2b.
  • the test is therefore passed and the polymer is suitable for preparing a dental prosthesis.
  • the mixture is let cool at room temperature and the pros ⁇ thesis is removed from the muffle.
  • FIG. 3 shows the prosthesis laid on the plaster cast before the thermal treatment.
  • the prosthesis becomes malleable on the differ ⁇ ent plaster cast. After cooling in the air, it is found that the hollow part of the prosthesis reproduces exactly the shape of the plaster cast.
  • Fig. 4 shows the prosthesis of the invention moulded on the plaster cast.
  • Example 1.2 Use of the prosthesis obtained in Example 1.2 (shown in Fig. 4) subjected to an additional thermal treatment and moulding on a plaster cast different from that of Fig. 4.
  • the prosthesis obtained in example 1.2 has subjected to a further thermal treatment at 140 °C for 4 minutes under at ⁇ mospheric pressure and moulded on a plaster cast obtained from a different dental arch, then cooled at room tempera ⁇ ture .
  • Example 1.3 has been repeated by using each time a differ ⁇ ent plaster cast deriving from a different impression for a total of 20 times. The obtained results are in line with those obtained in example 1.3: the prosthesis exactly fits the cast in all the tests carried out and does not show any retraction or dilatations with respect to the plaster cast.
  • example 1.2 is re- peated for preparing a prosthesis according to the present invention but using a thermal treatment at 180°C and for a time of three minutes under atmospheric pressure.
  • Example 2 has been repeated but using another plaster cast different from that of example 1.2.
  • Example 1 has been repeated but subjecting the strip to thermal treatment in oven at the temperature of 90 °C under atmospheric pressure.
  • the time of treatment at 90 °C was of 9 minutes.
  • the strip is submitted to the above test and a force of about 1 kg weight is applied using the hands for moulding the strip on the cylinder.
  • the strip maintains its initial shape, it does not bend and therefore it cannot be conformed to the surface of the cylinder. Therefore the test is not passed.
  • This example shows that the polymer being used, subjected to the indicated thermal treatment, does not allow to ob ⁇ tain the prosthesis of the invention.
  • Example 3 has been repeated but by applying a force of 10 kg weight for moulding the strip on the cylinder.
  • the strip maintains its initial shape, it does not bend and therefore cannot be adapted to the surface of the cylinder. Furthermore it is noted that dur ⁇ ing modelling in the strip cracks start to form. In order to avoid breaking of the sample, the test is interrupted. This example shows that the polymer being used, subjected to the indicated thermal treatment, even by increasing of about 10 times the force applied to the strip with respect to example 3 comparative, does not allow to obtain the prosthesis of the invention.

Abstract

La présente invention concerne des prothèses dentaires pouvant être obtenues à partir d'une prothèse modèle, elle-même obtenue par moulage de polymère au moyen d'un moulage dentaire en plâtre, et après exposition de la prothèse modèle à un traitement thermique à des températures comprises entre 105 °C et 250 °C sous pression atmosphérique, ladite prothèse modèle respectant le test suivant : une bande du polymère de la prothèse modèle de 6 X 6 X 80 mm prend la forme extérieure d'un cylindre métallique de 30 mm de diamètre, présentant une concavité au rayon de courbure de 12 mm et au centre de courbure dans un système de coordonnées cartésien de 15 mm et 15 mm, une convexité au rayon de courbure de 8 mm et au centre de courbure dans un système de coordonnées cartésien de 8 mm et 8 mm ; la bande, après avoir été soumise au traitement thermique, et déposée de manière à adhérer au cylindre en appliquant une force pouvant aller jusqu'à 1 kg et ainsi reproduire la structure externe dudit cylindre sans fissures ni fêlures.
PCT/EP2014/062425 2013-06-18 2014-06-13 Prothèses dentaires WO2014202484A1 (fr)

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TWI656008B (zh) * 2018-05-16 2019-04-11 邱玟鑫 全口義齒及牙托之多色層加工成形方法及其料塊
CN112368759A (zh) * 2018-06-07 2021-02-12 株式会社德山齿科 演示用器具

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GB2016994A (en) * 1978-03-15 1979-10-03 Sankin Ind Co Manufacture of denture base
WO1995035071A1 (fr) * 1994-06-22 1995-12-28 Minnesota Mining And Manufacturing Company Compostion de renforcement pour couronne dentaire et procedes de preparation de restaurations provisoires
WO1998004208A1 (fr) * 1996-07-25 1998-02-05 Miradent International Ltd. Procede de production et de mise au point d'un moulage chirurgical et/ou radiographique transparent pour un patient necessitant un implant, partiellement ou totalement edente, et appareil pour fabriquer ledit moulage
WO2003015720A1 (fr) * 2001-08-15 2003-02-27 3M Innovative Properties Company Structures autoportantes durcissables et procedes
US20050042576A1 (en) * 2003-08-19 2005-02-24 Oxman Joel D. Dental article forms and methods
WO2008033758A2 (fr) * 2006-09-13 2008-03-20 3M Innovative Properties Company Couronne solide malléable préformée

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Publication number Priority date Publication date Assignee Title
GB2016994A (en) * 1978-03-15 1979-10-03 Sankin Ind Co Manufacture of denture base
WO1995035071A1 (fr) * 1994-06-22 1995-12-28 Minnesota Mining And Manufacturing Company Compostion de renforcement pour couronne dentaire et procedes de preparation de restaurations provisoires
WO1998004208A1 (fr) * 1996-07-25 1998-02-05 Miradent International Ltd. Procede de production et de mise au point d'un moulage chirurgical et/ou radiographique transparent pour un patient necessitant un implant, partiellement ou totalement edente, et appareil pour fabriquer ledit moulage
WO2003015720A1 (fr) * 2001-08-15 2003-02-27 3M Innovative Properties Company Structures autoportantes durcissables et procedes
US20050042576A1 (en) * 2003-08-19 2005-02-24 Oxman Joel D. Dental article forms and methods
WO2008033758A2 (fr) * 2006-09-13 2008-03-20 3M Innovative Properties Company Couronne solide malléable préformée

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
TWI656008B (zh) * 2018-05-16 2019-04-11 邱玟鑫 全口義齒及牙托之多色層加工成形方法及其料塊
CN112368759A (zh) * 2018-06-07 2021-02-12 株式会社德山齿科 演示用器具
CN112368759B (zh) * 2018-06-07 2022-06-14 株式会社德山齿科 演示用器具
US11779447B2 (en) 2018-06-07 2023-10-10 Tokuyama Dental Corporation Demonstration instrument

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