US1665357A - Artificial molar tooth and method of making same - Google Patents

Description

April 10, 1928. 1,665,357

7 A. GYSI ARTIFICIAL MOLAR TOOTH AND METHOD OF MAKING SAME Filed Feb. 2 1926 4 Sheets- -Sheet 1 [/7 van/0n A/fred G s/I April 10, 1928. 1,665,357

A. GYSI ARTIFICIAL MOLAR TOOTH AND METHOD OF MAKING SAME I Filed Feb. 26. 1926 4 Sheets-Sheet 2 In yen/0r. /l/fred G /s/I dfforn e y April 10, 1928.

A. GYSI ARTIFICIAL MQLAR TOOTH AND METHOD OF MAKING SAME 4 Sheets-Sheet 3 Filed Feb. 1926 FIG. 7

v I? veh for.

FIG.8

April 10,1928. 1,665,357

A. GYSI ARTIFICIAL MOLAR TOOTH AND METHOD OF MAKING SAME Filed Feb. 26. 1926 4 Sheets-Sheet 4 Patented Apr. 10, 1928.

- UNITED STATES 1,665,357 PATENT OFFICE.

ALFRED GYSL OF ZURICH, SWITZERLAND.

ARTIFICIAL MOLAR 'roo'rn AND METHOD or maxmesm,

Application filed February 28, 1926, Serial 110, 90,726, and in Germany March 14, 1925.

The human mandible, in addition to up and down movements during mastication, makes the following grinding movements: (1) retrusive; (2) side bites from left to right and from right to left; and (3) incising or protrusive bite. Besides these three main movements, the mandible can alsomake all movements which are intermediary or between these mainmovements and are known as intermedlary movements. As

all the back teeth, namely the bicuspids and. -molars, are provided with cusps on their masticating surfaces, these cusps are positioned on the natural teeth in such a way that they 'do not hinder the above named masticating movements. These above named masticating movements do not take place in a horizontal plane, that, is, not in a plane parallel to the occlusal plane K, K, (Fig. 7), but really take place in a plane G, G, which has an inclination to the occlusal .plane K, K, offrom 5 to 50 to the said occlusal plane. By reason of this, the cusps on all the back teeth have to be limited by facets or defined surfaceswhich have the inclination of the arrows H, H, in Fig. 7, and which are more or less parallel to the plane G, G, which has the same inclination as the so-ealled condyle path movement of the mandible.

In an ideal natural denture all of the teeth of the lower jaw should be in 'contactwith the corresponding teeth of the upper jaw during the masticating movements. In civilizcd countries, however, where the people R subsist mainly upon soft. cooked foods, the

above named ideal conditions can rarely be found because the teeth which are fixed by their roots in the mandible and in the maxilla can and do stand more or less deviation from the ideal condition without impairing the masticating function and without loosening the teeth.

When, however, artificial teeth on plates must take the place of the lost natural teeth, it is essential that these artificial teeth shall be so shaped and placedthat substantially all of the teeth of the lower denture will contact with the corresponding teeth of the upper denture during themasticating movements. It might be assumed that the simplest way to make artificial posterior teeth (bieuspids and molars) would be to copy natural teeth as has been done for many years, and then to depend upon the up and down movement for mastication, but expeing artificial teeth. The natural teeth being firmly fixed in the bone, they are capable of exerting much greater force than an artifical denture which is much less firmly fixed in position, Artificial teeth being mounted on plates which rest on the mucous membrane, are capable of transmitting much less masticating force than the natural teeth, and hence should be so constructed that their cutting and grinding capacities are increased with less power than is available with natural teeth.

The object of the present invention is to provide forms of teeth with masticating sur faces that function like the parts of a cutting and grinding machine, in orderto secure greater masticating efficiency than is possi-' ble with natural teeth and thereby make up for the loss of power due to the way the artificial teeth have to be fixed to andmanipulated' in the mouth.

A further object is to provide a construction which will cause the upper and lower sets of teeth to so cooperate that, when masticating, the contact of the upper teeth upon the occlusal surfaces of the teeth of the lower denture will cause it to be held at all times in position upon the arch ridge of the lower jaw.

The present invention relates to artificial posterior teeth'which differ from natural teeth and are constructed in such a way that the above named three main masticatory movements are secured in a technically perfeet manner; and, in addition, my artificial teeth contain improvements in operative structure over natural teeth and all artificial teeth which have heretofore been produced prior to my invention, whereby greater efiiciency in the cutting and grinding or machine power of the teeth, considered as a chewing or masticating machine, is secured.

The form of each posterior tooth in a set of natural teeth differs greatly from the forms of the adjacent teeth because each tooth depends for its masticatory efficiency namely, the eight uppers,,consisting of two,

sisting. also of two right and two left" planes or facet surfaces, one of which planes upon its relation to the adjacent and opposing teeth. Therefore, in order toproperly designposterior teeth, it would be improper to design each tooth independently, but, 'on the other hand, all the posterior teeth,

right and two left bicuspids, two right and two left molars, and the eight lowers, conbicuspids, two right and two left molars, must "be designed as if they were two contiguous units, the upper set of eight teeth constituting one of the operatlve units and the lower set of eight teeth constituting the other operative unit. These two units of eight teeth each must be designed to secure a harmonious relationshi and to function together as a cutting an grinding machine. After these Punitsare made they are each divided into two parts consisting of a left half and a right half, each half containing two bicuspids and" two molars. Then these four half parts are each subdivided into four parts consisting of two separate bicuspids and two separate molars. In this way a set of sixteen single posterior teeth are secured and which may be properly incorporated into upper and lower dentures which will cooperate and function perfectly.

In the present invention, each posterior tooth is developed from a primordial form,

the masticating surface of which has at least one obtuse corner which is formedby three unctions with the com lementary planes of the opposing teeth of t e opposite jaw during the retrusive movement ofthe lower jaw,

. another of which planes functions during the protrusive movement, and the third of which "planes functions during the lateral moveing ruptions forming cutting edges and the .dif-= fering shapes of the planes securing greater tool or machine-like efiiciency in cutting and masticatin food. Theplanes of each of the u per and ower molar teeth and of the lower biscupids form a positive obtuse corner and a negitive or depressed obtuse corner, the 'posltive and negative corners in each tooth being out of alinement, but in which further, the positive corner of either an upper or lower tooth is in alinement with the negative which coact with or are comp ementary thus insure movements of the mandible. It is here thereto in 'occlusal and masticating relation.

Broadly considered, my invention comprises'the-artificial posterior teeth embodying the features of improvement above referred to and the method of making same, all of which are more fully described hereinafter and defined in the claims.

Referring to the accompanying drawings: Fig. 1 is a geometrical diagram illustrating a construction made up of associated parts each having a masticating surface embodying the'primordial form constituting an upper denture unit containing right and left bicuspids and molars designed to function with the lower jaw unit containing complementary right-and left lower bicuspids and v molars; Fig. 2 is a plan and Fig. 3 a Section online 3-3 of Fig. 2, showing a primordial obtuse positive-corner of a'form for. use in my improved artificial teeth; Figs. 4 and '5 (section on line 5- 5) are similar views in respect to the primordial obtuse negative corners employed in my improved artificial teeth; Fig. 6 shows a portionof Fig. 1 with the outl1ne of the posteriorteeth marked thereon; Fig. -7 i'sa diagram showing the v manner of adapting an articulator vto' the-- shapingof' the primordial tooth; 'form mas-j ticating surfaces illustratedin'Fig. 1 ';'Fig. 8 3 i shows a side view of one of the cutting knives employed in the articulator; Fig. 9 is a front view of the same; Fig. 10 is a gen-* eral view showing the relative position of the cutting knives when looking -upward upon them when positioned on the articulatory Fig. 11 is a primordial form of a lower tooth row unit; Fig. 12 is a perspective viewof a primordial form unit of upper teeth; Fig. 13 is a similar view of a corresponding lower or complementary unit; Fig. 14' is a finished right hand view of a lower unit; Figs. 15 and 15" eating the ocelusal relation of the upper and lower posterior teeth at the right side of the mouth and embodying my improvements;

are lingual elevations indi- Fig. 16 is a perspective view illustrating a row of the upper posteriors corresponding to the left side of the mouth embodying m improvements; Fig. 17 shows the fourteeth illustrated in Fig. 16', somewhat separated and Fig. 18 is a further general view of the second upper molar having thereon the addi tional' grooves, fissures, beauty marks, etc. such as inthe commerical teeth. A primordial form of an obtuse positive corner is illustrated in Figs. 2 and 3 and is geometrically constructed with the three bite guiding planes or facet surfaces of an upper tooth and ada ted to guide complementary planes of'the denture for the lower jaw and the three principal masticating pointed out that Fig. 2 represents a face I corner onthe respective lower or 11 per teeth w Of h P n f h thr e guiding 1 as they are shown in Fig. 1, the illustration 1n Fig. 2 showing one of the obtuse positive corners which appear in plurality in the illustration of the left side of the upper unit but corresponding to the right side of the denture when in the mouth. 'In the pa rticus lar illustration of Figs. 1, 6 and 10, the cut- Itings provide for two bicuspids and three molars for each side of the jaw, whereas in artificial dentures it is customary to employ only two molars on each side, asshown in Figs. 7, 11,12 and 13. Y

A primordial form of an obtuse negative or depressed corner geometrically constructed is shown in Figs. 4' and 5, the latter being a section'of the former on line 55, and said negative corner consists of the three bite guiding planes or facet surfaces of a lower tooth and is complementary to what is shown in Fig. 2. These negative corners constitute the depressions inthe occlusul surfaces of the teeth for cooperation with the cusps of the opposite or coact-i ng teeth and consequently the teeth of the upper and lower'sets may each have their occlusal surfaces provided with both positive and negative -corners.

A primordial form of a lower tooth unit from whichfour posterior teeth may be shaped is shown in Fig. 11, andv it is here pointed out that this lower unit is obtained by taking a plaster impression from the upper unit which was made by the action'of the cutting knives arranged in the lower jaw of the articulator, as hereinafter more fully described. In fact, in this invention only the set of molars and bicuspids for one of the jaws are modeled b use of the cutting knives, as indicated in l mordial tooth form for the other jaw is made by molding or casting the same from the cut form so that the teeth of one jaw are complementary to the teeth of the other jaw, and this is true irrespective of whether the cutprimordial form is'made for the upper or for the lower set of teeth.

The right side of Fig. 12 shows the mechanical primordial construction following the essentials of the geometrical design of Fig. 1, whereas the left side of the figure shows a similar construction from which all .of the superfluous material has been removed, leaving the Bicuspid and molar teeth which contained the bite guiding planes or facet surfaces in their natural outline upon the occlusal'surfaces.

Fig 13 is a corresponding lower .1 or complementary unit with the occlusal surfaces inversely formed to those shown in Fig. 12, just as would occur by casting or molding it from the structure of Fig. 12 as a pattern' On the right hand side, the material has been cut away to show clearly the shape of the two molars and two bicuspids, whereas on the left hand side of the primordial form, the general position and shapes of as 15 in the instance described.

ig. 7, and the priside bite angle of theteeth, by reason of which rotation centers, the axis for the normal side bite movement to the left and to the right, can be geometrically determined. The centers R hear such a relation to the position of the condyles g, 1, that the upper articulator frame is permitted to move in the directions according to the curved lines 4, 4, in Fig. 1. The connecting lines between the points C, R, in Fig. 1, form generallyan angle alpha.with the connecting line between the two condyles. may vary between 5 and 30 and is shown In Fig. 7,

the angle beta is shown as set at 33,but

' where an adjustable articulator isemployed, this angle may be varied, that is to say, it

may be. reater or smaller. These angles, alpha? and'beta, are not varied for each individual case, but are predetermined, preferably as aforesaid. as a basis for producing primordial form units to correspond to required teeth forms for general use to be produced having my improved mast1catmg or occlusal-surfaces suitable for proper ac? tion with maxilla and mandible of sizes and' shapes and condyle and. tcmporo mandibular articulations corresponding to a natural skull. The points C, C, J,,in Fig. 1, are the three main points of the equilateral triangle of the mandible, J being the point where the two (upperand lower) central incisors meet, otherwise indicated at 2 in Fig. 7. The points M, M, F, are the centers by which the natural are 3, 3 and 3, of the tooth rows can be constructed and by using the two points L, L, successively as centers for the compass,

the equallyspaced arcs 6, 6, corresponding [to the grooves of the upper bicus pids. and

molar teeth' may be drawn, and by next placing thecompass at the point F, the arc 3 of the curve of. the anterior, teeth may be drawn. .Also, by placing the compass successively at the center points R, R, concentric arcs 4' are drawn from each of said centers, starting approximately from the centers M, M, and twenty of these arcs are respectively grouped into ten are sections Z of increasing widths and spaces, determined in the manner hereinafter described. The radial distances Z of the 'arcs 4 are dctcrmincd as follows: Referring to Fig. 7, and keeping in mind the radial lines with the arrow marks leading to' the point P at the front of the This angle III movable frame of the articulator which gives the vertical angles of the cutting edges of the-knives 16 and also keeping in mind the lines H parallel to the condyle socket line G also formed by the part on the upper or movable frame of guide portion 12 at the front. of the base or stationary part of the; articulator over which the pin 14 travels; we will find that the said parallel lines H intersect the radial lines leading from the point P at what would be the-apex of one of the positive corners of cusps of the upper teeth, as very clearly shown in Fig. 7. If now 'we draw radial lines from the point Kto these ntersecting points of the parallel and radial lines above mentioned, we will obtain dis tances between these radiahlines from the point K measured along an arc B, B, also struck from the center K and passing through the highest points 17 of the cute ting knives 16,-which distances will repre? sent the radial distances Z in the diagram Fig; 1. As stated, the point K corresponds, to the average arc of a natural row of teeth with a radius of about 15 to 20 centimeters, (page 12, line 20). It is to be understood that the distances and angles between the operative parts of the articulator are al ready determinedin the commercial articulators by giving tothem average distances and angles based upon investigation of natural skulls. After drawing the tooth are or arch 3 from right center M and the arcs 4 from the left center R, the equi-spaced arcs 6 from the right center Linay be drawn between the left hand arcs 4 in pairs (Z) ,and close to the tooth are 3, ,giving intersecting points 5. These are portions 6 give the position of the knives 16 in Fig. 7. Then the arcs 4 from the right center R are drawn through the intersecting points 5. In practice, when the knives 16 have been positioned in thearticulator and the articulators parts given the relative movements, such as occur in mastication, the points 17 thereof cut or scrape the grooves in the plaster corresponding to the negative corners 8 lyingin arcs 6 and indirectly form the positive corner 7 by the'cooperation' of the two adjacent knives. While the short are. per- I tions 6 between the arcs 4' in pairs may be 1ncentric arcs equally spaced apartgsai dividually considered as straight lines,-they would be tangential to the arcs 6. The center L for these arcs 6 may be ositioned as follows: Thiscenter L will lie in a horizontal line (from L to L) across'the rear. ends of the second or posterior. molars. .(whereat thecutting knives 16 on the right and left sides of the denture are parallel) and where a tangent from. the uppermost are 4 crosses it,-..-the tangent beginning adjacent to the tooth row are 3; and the arcs 6 described about said center L are substantial]; conthe 'articulator and the ing predetermined for the width to be pro: I k

= vided for in V sidered. Having once. positioned the knives,

the tooth buccal-lingually con-. I A

they, by reason of the possible movements 8 of't e same formationlim ted by three planes or facet surfaces 9, 10, and, 11, as

'70 cutting or carving of the plaster to the de- 1 of. the drawings. In

{and negative or depressed corners graphically illustrated in Figs. 2.to-5. The

design matically in the plaster when the knives '16 are set as described hereinafter in connection wih. Figs. 1, 7, 8, 9, and 10, and the upper movable frame ofthe articulator carrycorners 7 (cusps) (Figs-2 and'3). .are formed as 'well as the negative or depressed corners 8 correspondingto the depressions in the teeth. The various arcs 4, 4, and 6, 6, are

-definitely positioned on thediagram as explained, and as these are all: definitely-deterof'rthe relief is produced auto-- the plaster is moved over the knives in the various directions permitted by the ar-v ticulator; and in Fig; '1, this relief -is indicated by the shading whereby the positive.

mined by the inoyable points'of the: artic u-' lator and the angle, shape and positionsjof the cutters 16, the final design in the relief produced' bythe cutters is "caused, to have a form in which the variousfacets 9, 10 and 11 lie in planesat apart (Figs. 2 and 3 4 negative corners. The shading on Fig. 1 and on others of the figuresis merely to indicate the different portions in the actual whether they form' positive corners or relief in plaster and whose defining lines are formed by theeorresponding' arcs 4. and

' 6, as explained.

The general sizes of the teeth to be formed are roug ly laid out, asin Fig. 7, the'cutting points 17 of theknives are definitely positioned in the arc B, B, which is also a predetermined are for the occlusal surface. These cutting points where they lie in the no I predetermined by the dentist and when are B, B, are' then connected by the oblique radial lines with arrow heads from the com mon center P, this will give the radial angles which definitely :give the angle of the anterior facets 11. of the teeth and thereafter I lines H parallel tot he line G, G, (through the condyle) and extending through the points 17 of the teeth gives the obliquityof these:parallel lines and form the. angle of the posterior facets 9 of the teeth. 7

It is to be understood that the arcs the right handcenter R are not continued from the right hand side across the center of the'diagram into the left hand side, but that 4 froni" hand arcs 4 and 6 and, t erefore, these left that in Fig.7, the tooth hand arcs crossing the points 5 described from the right hand center R will be formed from all the crossing points 5 without regard to the position of the arcs 4 at the right hand side. In regard to the choosing of the points 5 as to which shall form parts of the positive or negative corners it will be noted facets have high and low "points alternately and, therefore, the points 17 would represent the points 5 on the upper arcs 4 of each pair while the intermediate depressed points would correspond to the points 5 which would be formed by the crossing of the are 6 with the lower arcs 4 of each of the pairs. The direction of the arcs 6 indicates the positioning of the knives 16 as shown in F i and thepoints 17 of these knives won (1 be located at one of the .intersecting points 5 and which would, in its operation upon the plaster, cut one of the depressed corners.

The distance apart of the arcs 6 is uniform, and this distance is selected in respect to the width of the teeth in a lingualbuccal direction and to provide the necessary I number of facets to form a tooth structure of normal width. It will be understood that for a small jaw the widths will be less than for a large jaw. The distance apart of the concentric arcs 6 is predetermined to suit the widths of the tooth structures to be made. c y

The oblique arcs from the right hand center R do not bear any relation to the right hand arcs 4, except that they are made from the same center. They are positioned to pass through the points 5 at the left hand side without any regard to the arcs 4 at the right hand side of Fig. 1, and consequently the are not arranged with that uniformity which is peculiar to the paired arcs 4 at each side of the diagram Fig. 1 in connection with the letters Z.

The three planes or facet surfaces of each corner 7 and 8 are the guiding surfaces of the teeth during the masticating movement. In the preferred form of obtuse corners adapted to my invention of artificial teeth, the corners are best made in a manner similar to one of the corners of a rhombic-dodecahedron'or a pentagon-dodecahedron, in which the angles between .the ridges or junctions of the planes or facet surfaces 9, 10 and 11, are 110- taken in the plane of said surfaces, as indicated in Fig. 2, such corners, constituting essentials to the masticating surfaces of the teeth, are best suited for the natural movements of the jaw in biting and masticating. The facet surfaces 9 (Figs. 1 and 12, for example) are the guiding surfaces of the'teeth during the protruslve or incising bite. The facet surfaces 10 are the guiding surfaces dur- "teeth, a mirror picture or inverse view of the upper *relief A is taken by a cast therefrom.

A relief A taken as a primordial form with its positive and negative obtuse corners and their three guiding planes or facet surfaces 9, 10 and 11, maybe made according to the geometrical construction shown in Fig. 1, in any plastic material such as wax, plaster, etc., by a sculptoring process to serve as the model for an upper set of teeth as indicated in Fig. 6, and outlined at 25, the unit teeth in this figure having the primordial masticating surfaces which are preserved intact, although by hand carving the corners can be slightly rounded, additional curves, fissures, beauty marks, etc., added, to constitute a tooth model (Fig. 14), following which, in shape and design, the corresponding porcelain teeth may be made.

The unit containing an upper set of teeth as outline 25 being themodel for a single tooth.

In Fig. 1, the primordial form is shown-for I an up er set of posterior teeth, but in Fig. 6' one alf or oneunit is shown by way of illustration when outlining the teeth at 25. Fig. 6 illustrates how the upper right posterior teeth can be isolated 1n their natural outline from the geometrically constructed unit shown in Fig. 1, by a rocess of cutting away of the surplusmaterial (not shaded). In Fig. 6 the tooth outlines denoted by 10, 10 and 10 and the next upper outline there to denoted by 25, represent. the four posterior teeth, as shown by themselves in Fi s. 16 and 17. The principle involved in this 1nvention will apply in producing the required angles and facet shapes for the whole pos sible sixteen teeth of the upper jaw, but as a commercial proposition, t is customary to make four posterior teeth, namely, two bicuspids and two molars for each side of the denture by this method and form the other six frontal teeth more for artistic appearance since they have no depressions assorocess would indicate the required shapes or the whole sixteen teeth in the upper jaw,

and Fig. 7 shows the making of five teeth on each side. y

The making of a relief according to the design of Fig.1 can be easily done by a simple mechanical procedure with the ald of an I articulator. For this purpose, I use any I good; articulator, such as the articulator described in my ;German Patent No.'293,074,

i articulator Fig.

7 thereof. 1 secure upon the lower frame of I that the points 17 of the the articulator a double row of cutting knives in the shape of sharks teeth 16, Fig. 7 and Fig. 10, which knives correspond to the negative corners 8 (Fig. 1) in such a way knives 16 shown in Fig. 10 coincide with the recesses or negative corners 8. In Fi lOis shown a general-view of the relative ositions of these cuttingkniveswhen' looking upward upon them, and the points'at the end of the heavy black marks 17' re resent the points of the cutting knives w ich are arranged in a schematic re roduction of Fig. 1. In shape the knives i 8 and Fig.- 9) have parallel sides 18 and t e cutting edges thereof are oppositely beveled and the front end is per pendicular. .The cutting edges 19, in plan, are arranged in the directions of the arcs 6 described from the centers L, L, Fig. 1.

. The points 17 of the knives are also preferably arranged in a concave arc B, de-. scribed from center K (Fig. 7 which corresponds to the average arc of a natural row of teeth with a radius of about 15 or 20 centimeters. The cutting edges 19- are directed Y towards the common center P which is about one centimeter in front of thepoint of the nose 21, said center being also determined on the articulator' (Fig. 7) by the point'P. This new .form of cutting knife makes it possible to mechanically produce a model of the upper tooth row. If in the upper partof the articulatora-block of plaster 22,Fig. 12, is fixed, and if it is moved upon thecutting knives by making side bite movement to the right side and to the left side, protrusive movements forward and back ward and all intermediary movements (in an anatomically correct articulator), the plas- Lter block will become out into the form of reliefi-shown by'Fg. 1 with its positive and" negative corners-A',and as can be seen 12 and as also on the right side of .Fi

hand side where shown in Fig. 12 at thev ie the unnecessary portions of the plaster on both sides of the row of teeth have been cut away, whereby insteadof three series of corners (7 and 8), asshownin Fig. 1, only two series of corners remain in Fig. 12. But, in Fig. 12 can still be seen the positive corners 7 and the negativecorners 8, each of which is formed. by the three planes 9, 10

and 11. If we draw on the relief of the lower tooth row Fig. 13, the prolongations ofthe ridges as at 23- in Fig. 11 of the corresponding planes, then this relief can be compared with a double row of rods or piles of rectangular cross section projecting vary- 1,ces,s57

ing distances from the corresponding to one side of the block having'the appearance of being inclined downward and inward in the same general direction. In Fig. 1, the corresponding double row of rectangular planes or facets 11- of opposite tooth rowsare inclined" toward a (ommon median line above the figure. These side of the figure region these planes 24 are interrupted alter nately, one plane extending across the tooth and the next plane being interrupted as, at 24*. It is also important that,the planes 11') on the right side of Fig. 12 and which. guide the side bite movement are differently shaped and not continuous with each other. This non-continuity is shown in Fig. 6 at 10', 10 10 and 10, and in Fig. 12 at 10 and 10; By this non-continuity, ridges are formed that act? as cutting edges and which increase the tool or machine-like action of the masticating surfaces so that the effective masticating power may approximate the masticating power of in the bone.

In Fig. 12, right side of the figure representing. the upper tooth row (inverted) and in Fig. 13

at the left side is shown the relief of the corresponding lower tooth row, the same therefrom. The portion of the plaster material not required for theformation ofthe teeth, that is,-the material outside of the 12 and in thev right side of Fig. 13.' These constitutethe primordial forms of the teeth. his .now necessary to carve the outlines,

natural teeth that are rigid loo the relief illustrated on the base, all of the rods shown a series of 'being a cast counter or impression taken deepen the grooves and round off the corners.

so that the teeth will present a more natural appearance, with the result shown in Fig.- 14, 1n which is shown a series of depressions i 26 made in the mastic'ating surfaces for the purpose of facilitating the crushing of food and which may also be used for identifying the respective teeth. In the first bicuspid bicuspid two depressions may appear. In

one depression only appears. In the second the first molar one depression only appears, while in the second molar two depressions appear. the planes or' facet surfaces, but they reduce the area of the-planes or facet surfaces and These depressions do not destroy f increase the cutting power of the teeth. I For the purpose of securing'greater'm-astieating efiiciency, the lingual cusp 28 of the second upper bicuspid tooth is formed so that when it is articulated with the corresponding lower bicuspid and first molar tooth it also engages the masticating surface at 8 of the second lower bicuspid instead of only projecting between the second lower bicuspid and the first molar, as occurs on the buccal sidev wherein the buccal cusp 27 of the upper second bicuspid tooth does project in o the inter-dental space between the second lower bicuspid and the first lower molar '(Fig. In my improved. teeth,

the lingual cusp of the first upper bicuspid 0nd lower bicuspids, as heretofore.

is also formed so that it similarly engages the masticatory surfaces of the first lower bicuspid instead of projecting into the-interdental space between thefirst and second lower bicuspids, whereas the buccal cusp of the upper first bicuspid does project into the inter-dental space between the first and sec- This construction ofthe bicuspids providing increased masticating capacity is shown in Figs. 15 and 15, in which it will be observed that the lingual cusps of the upper bicuspids Y and Z are respectively received in depressed corners 8 in the upper surfaces of the lower bicuspids -Y and Z, and it will further be noted that the oblique planes or facets of the upperbicuspid Y cooperates with the complementary planes on the lower bicuspid Y and first lower molar X, whereas the upper first bicuspid Z has its planes .or facets complementary to and cooperating only with planes or facets onboth the lower bicuspids Y and Z. To insure this co action at 8 between the occlusal surfaces of the upper and lower bicuspids, it is necessary that the lingual sides of the lower bicuspids are provided with the corners or depressions 8 to the rear of these lingual cusps and for the upper bicuspids Y and Z to be given, as it were, a horizontal twist 7 so that the lingual cusps are advanced relatively to the buccal cusps wherebythe former engage the masticating surfaces of the depressions in the lower bicuspids. In this manner, the bicuspids coact to insure improved masticatory action.

In respect to the lower bicuspid teeth X and Y having three cusps as indicated at 8 in Figs. 13 and 15", it is. pointed out that'as above explained these bicuspidsj ave the depressed corners 8 and [from the explanations as to the same being formed by the three planes 9, 10 and 11 at an angle to each other and the .further fact that the general occlusal surface is more or less circular, it will necessarily result that the said planes project to form three cusps about the depressed corner 8, and the shapes and extent of the cusps varying in shape according to the outside configuration of the final tooth form and the position of the depressed corner awayfrom the'center of the occlusal surface. In the present case, these depressions are considerably away from the center and hence they ditfer'in-size.

After the tooth models have been prebiscuitedduplicates of the models in porce lain material and whichare subsequently vitrified.r These artificial teeth may be produced as an .integral structure comprising a unit of four teeth or separate units for the two molars and for the two bicuspids, or, on the other hand, each tooth may be molded separately as indicated in F ig.-17, in which the two molars (V and X and two bicuspids Y and Z-of the upper set are indicated in their relativepositions but separated interdentally to' illustrate their independence. Furthermore, the illustration of the individualteeth in Fig. 1-7 and the correlation of these teeth when properly positioned, as indicated in Figs. 15 and 16,.will' make the fundamental featuresembodying the corners and planes of the upper set more clearly understood; and reference to Fig. 18, which shows the finished porcelain tooth corresponding to therear -molar X, will give a better understanding of the commercial tooth when the 1 curves, fissures, beauty marks, etc, have been applied to it, withoutdestroying the cooperating planes or facets, and compares with the rear lower molar'of Fig. 14- which would cooperate with it when in occlusal relation, as indi cated in Fig. 15.: As the lower posterior teeth have their occlusal surfaces formed complementary to the occlusal surfaces of the upper teeth, it willnot be necessary to illustrate them more in detail than is found in Figs. 11, 13,14 and '15, but they, as in the case ,of the upperteeth, maybe formed in blocks of two or four or as individual teeth,'as desired. f

I have described my improved method and the article of manufacture produced thereby in connection with apparatus which I deem to be best suited to the requirements of'the invention and on account .of economy is preferred-in commercial practice-but I do not restrict onconfine myself" to the minor or secondarydetails either as to the method of procedureor the means employed .in putting; it into eifect,as variations, therein maybe resorted to as matters for the skilled artisan" and without a departure from the spirit of the invention.

Having now described my invention, whatI claim and desire to secure by Letters Patent is:

1. Themethod for the mechanical pror 1 ing the primordial duction of primordial forms of the back teeth to constitute a portion of an artificial denture, which consists insecuring to one member of an articulator two rows of cutting knives arranged in a curve corresponding to a natural back tooth row at one side of the jaw and in more or less parallel relation and having cutting edges which slope backward and downward with a gradual lessening obliquity from front to rear, applying plaster to the other member of the -a1'ticulator,and thereafter causing a relative movement between the knives and the laster corresponding to the left and to the right side bite movements and to the forward or protrusive movement and backward or retrusive movement and to all possible movements of the articulator corresponding .to intermediary masticatory d1- rections so that angular depression and elevations each formed of three planes inclined to each other are cut in and upon the plaster block and which then serve as the primordial form of thematicatory surfaces of the back tooth row.

2. The method according -to claim 1, wherein further, from the plaster block havmasticatory surface cut thereinpa second block of plaster. or its equivalent is produced by casting or molding it from the primordial form and having inverse elevations and depressions, one of said plaster blocks shaped to represent the masticatory surfaces of the back teeth corresponding to v the tooth row'of one of the jaws and the other of said plaster blocks shaped wherein further,

faces of the .back

represent the masticatory surfaces of the back teeth corresponding to those of the other jaw.

3. The method according to claim 1,

from the plaster block having the primordial form of the tooth row cut therein, a second block of plaster or its equivalent'is cast or molded therefromnnd having inverse elevations'and depressions, one of said plaster blocks shaped to represent the masticatory surfaces of the back teeth corresponding to those-of one of the jaws, and the other of said plaster blocks shaped .to' represent the mastlcatory surteeth corresponding to those of the other jaw, and further characterized, by finally cuttingaway the sur plus plaster material and dividing the tooth row block transversely into sections corresponding to the several back-teeth eaclraccording to its required occlusal or masticas tory surface structure.

4. Back teeth for part of an artifical denture, wherein each tooth is provided with at least one obtuse corner on its masticatlng surface shaped according to form which is characterized so that each of these corners is formed by three incline form of the tooth .row-

corners and facet of substantially the same inclination as @the transverse plane I facet lying in a plane corresponding to the are advanced wherebya primord al planes 9, 10 and 11,, respectively arranged at angles to each other, one of which planes 9 is inclined in a forward and backward direction and extends in widthgbuccal-lingually and serves as a sliding and guiding surface for the teeth in the opposite jaw during the protrusive or iricisingbite movement, another of which planes 10 is inclined in a buccal-lingual direction so as to serve. as a guiding surface during the side bite movement of the jaw, and the thirdof which planes 11 is inclined in a forward and backward" direction so'as to serve as a guiding surface during the retrusive movement.

' 5. A row of upper hack teeth as part of an artitical denture having their mastication surface provided with facets lying in a plurality of planes having different inclinations and three of which planes of different inclinations form obtuse corners of. cusps and likewise three of the planes of different inclination form depressions of the same general shape, each of the teeth having one' of their facets arranged in a plane corresponding to one-of the inclinations and extending inwidth transversely across the teeth in a buccal-lingua'l direction, and further, said teeth each having twoother facets separated by the transverse facet and lying in the oblique planes corresponding to one of the other inclinations and obliquely presented to the buccal side of the teeth, and in which also, the molar teeth are each provided with an upward corner or cusp at the junction of their anterior and buccal formed by a shorttransverse first mentioned and a third and remaining plane inclination.

6. The invention according to clann 5,

-wherein further, a corresponding set of lower back teeth constituting a cooperating part of a lower artitical denture is provided having facets, and deperssions complem'em tary to'the depressions and facets of the upper set of back teeth, and in which further, the lower bicuspids are provided with on the depressions V buccal and lingual cusps, and

to the main lingual side infadditionthe upper hicuspids are each provided with two ma n cusps 111' whlch. the lingual cusps pressions in the corresponding lower bicuspids while the buccal cusps of said upper the inter-dental space bebicuspids occupy teeth with which they enbuccal cusps, and lowerhicuspids are prod vided for a lower denture having-on their that the lin-' 'gual cusps are advanced relatively to the they. engage the de- 1 lingual sides two cusps and a depression between them, and whereby said lingual cusps of the upper bicuspids occupy a. position to be received in depressions in the adjacent lower bicuspids instead of wholly occupying the interdental space between the corresponding lower teeth.

8. An artificial molar tooth having facets on its masticating area formed of a plurality of surfaces arranged in inclined planes abutting in sets of three planes when arranged at an angle to each other, two of which facets extend in a buccal-lingual direction of the tooth, one entirely across the tooth and the other partway only, and the surfaces of the other facets forming parts of inclined planes arranged in a direction from the posterior to the anterior parts of the tooth, said planes forming at least six facets arranged inpairs at an angle to each other and said latter planes interrupted in a posterior-anterior direction by'the buccallingual planes. 1

9. An artificial molar tooth having facets on its masticating surface formed of a plurality of smaller surfaces arranged in planes at an angle to each other, two of which facets extend in a buccal-lingual direction, one entirely across the tooth and the other partway only of the tooth, and the remaining facets extending in a direction from the posterior to the anterior parts of the tooth and arranged in pairs at an angle to each other and in planes which are interrupted by the buccal-lingual plane of the first mentioned facets.

10. An upper bicuspid for an artificial denture, in which there is a longitudinal main groove and a buccal cusp and a lingual cusp on opposite sides of the main groove, and wherein further, the lingual cusp is advanced beyond the position of the buccal cusp whereby the alineinent between the two cusps is greatly oblique to the ahnement of the main longitudinal groove and as though the lingual cusp of the tooth was given a horizontal twist.

11. A lower bicuspid for an artificial denture, in which the buccal side is provided with a single cusp and the lingual side is providedwith an anterior large cusp and a posterior small cusp with a depression. between them and the buccal cusp for receiving the lingual cusp of an upper bicuspid.

12. The invention according to claim 11, wherein further, the depression is formed by three oblique facets lying in corresponding oblique planes making equal angles with each other and located near the posterior side of the occlusal surface of the tooth.

13. A row of upper back teeth, including molars and bicuspids as part of an artificial denture, having their mastication surface provided with facets lying in a plurality of planes having inclinations in or parallel to three main planes and in which three of said facets of different inclinations when associated together in one relation form positive corners or cusps and likewise in association in another relation form negative corners or depressions of the same general shape, each of the teeth having one of its facets arranged in a plane corresponding to one of the main plane inclinations and extending in width transversely across the tooth in a lingual-buccal direction, and further, said teeth also having facets obliquely presented to the buccal side of the tooth and having an inclination corresponding to another of the main plane inclinations,

and in which also the molar teeth have their facets respectively separated into parts in a mesio-distal direction by the transverse facet portions and facets and respectively lying in oblique planes whichare each coincident with one of the two other main plane inclinations and also each molar provided with a corner or cusp atthe junction of their anterior and buccal walls formed by short transverse facets and the former having substantially the same inclination as the' transverse plane and facet first mentioned.

14. An artificial molar tooth having facets on its mastication area, said facets constituting a plurality of inclined surfaces respectively arranged in abutting relation in sets of three planes, said planes arranged at an angle to each other to form positive cor ners or cusps and negative depressed corners two of which facets of one inclination extending in a buccal-lingual direction of the tooth, one entirely across the tooth and the other part way only, and the surfaces of the other facets forming parts of the inclined planes arranged disconnectedly in a direction from the posterior to the anterior portions of the tooth by the buccal-lingual facets and forming at least six facets arranged in pairs at an angle to each other.

In testimony of which invention, 1 hercunto set my hand.

ALFRED G Y S1.

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