US2416983A - Artificial teeth - Google Patents

Description

March 4, 1947. g glcksoN 2,416,983

ARTIFICIAL TEETH Filed July 1, 1943 2 Sheets-Sheet l INVENTOR: Fl

" 3 R055 0- DICKSON,

r V ATTOR 5?,

March 4, 1947. DICKSON 2,416,983

ARTIFICIAL TEETH Filed Jul 1, 1943 2 Sheets-Sheet 2 INVENTQR: R055 0. DICKSON,

ATTORNEY Patented Mar. 4, 1947 UNITED STATES PATENT OFFICE 3 Claims.

The invention relates to improvements in artificial teeth generally and more particularly to the more or less specialized art of making dentures involving the posterior teeth (bi-cuspids and molars) which perform the grinding functions of the human masticating mechanism.

An object of the invention is to provide forms and arrangements of artificial teeth, particularly the posterior teeth, that avoid the errors and faults in the practice of artificial dentition, by effecting a more perfect equalizationand balance in forces and pressures between the occlusal sur-- faces of opposed teeth, during mastication, incising and grinding.

Another object of the invention resides in the provision of artificial posterior teeth, wherein the ocelusal surfaces, cusps, ridges, and grooves or fissures, are so formed and related that they are non-locking and otherwise entirely free from interference of any kind whatsoever, in all phases of mandible movement during mastication, and effect perfect contact, the inferior with the superior, whenever brought together in full occlusion. a

Still another object of the invention has to do with the construction of artificial posterior teeth, either individually, or enblock for use in all cases where all the posterior teeth have been lost, mounted by means of plates, bridges or otherwise, in a form that they may be readily, and with comparative ease, set up in strict conformity with the curve of spee, as determined by a co-ordinate template, or with no curve atall, with no loss in balance or efficiency and with perfection in occlusal surface contact and non-interference between those surfaces, during the masticating process.

Yet another object of the invention is resident in the provision of forms of artificial posterior molar teeth, wherein the cusps are made more or less high as the cusps of newly erupted teeth, with the cusp forms running transversely and with a wide groove between the mesial buccal cusps and the distal buccal cusps and with grooves likewise on the lingual side, these grooves being sufficient to accommodate the cusps of the opposing teeth and functioning without any interfering or interlocking effect in their movements into and out of intervening grooves of opposing teeth, so that relative lateral movement of the dentures during mastication is prevented, thus performing a smooth, gliding, stroke without vibration, and thereby obtaining a more perfect cutting, grinding and crushing, of fibrous foods; the cusps of the teeth, at one side of an inferior denture, having such movement with respect to the grooves of the complemental teeth of a superior denture, while the cusps of the teeth, at the opposite side of the inferior denture, balance with a rocking motion on certain planes of the cusps of opposed teeth of the superior denture.

Still another object of the invention is to construct the inferior posterior molar teeth with central ridges and cusps which extend from the distal central cusp of the inferior second molars through and including the central distal third of the first inferior bi-cuspids, the remaining twothirds being a fissure, so that food is cut and ground against the ridges and cusps on the working side of the dentures, while a balance is obtained on the non-working side.

A further object of the invention lies in the provision of artificial posterior teeth, wherein the occlusal surfaces of each is made with a cusp and ridge formation that precludes of any positive contact or interlocking engagement between the cusps of one tooth with those of an opposing tooth; the cusps and ridges having surfaces defining inclined planes which permits them to always slide one up or against the other and into and out of intervening grooves and fissures, so that all of the masticating forces and pressures are brought into balance between opposite sets of the teeth and lateral displacement of the dentures is prevented.

Another object of the invention has to do with the teeth as hereinbefore characterized and in the mode of occlusal, order of occlusion or occlusion relation of which, the buccal cusps of the superior molar teeth articulate buccally to the central longitudinal elevation, ridge or cusps of the inferior molar teeth and in grooves between the buccal cusps and introdental spaces of these lower teeth with no overlapping or projecting of the buccal superior cusps over the crest of the inferior molar cusps and on the lingual side of the lingual cusps of the superior teeth articulate lingually to the central longitudinal elevation, ridge or cusps of the inferior molar teeth and,

. like the buccal side, the lingual cusps articulate in grooves between the lingual cusps and the interdental spaces of the inferior molar teeth; hence the superior lingual cusps do not set in corners, depressions, pits or a main longitudinal groove but, as before stated, in grooves between cusps, the cusps of the inferior molar teeth likewise articulate in grooves between cusps of the superior molar teeth, thus obtaining a non-locking effect of the cusps in the movements of the mandible, preventing dislodging of the dentures.

With the foregoing and other objects and advantages of equal importance in view, the invention resides in the certain new and useful combinations, constructions, and arrangements of the functional elements (masticating) of artificial posterior teeth, as will be hereinafter more fully described, set forth in the appended claims, and illustrated in the accompanying drawings, wherein:

Figure 1 is a perspective view of an articulator in which is mounted a block of artificial stone A in co-ordination with a template B and showing how the molar teeth are carved in contact with the template, with .r-:c indicating the occlusal plane, yy the circle of the template by which the curve of spec is obtained, and z-z the circle of the template by which the incline to the mesi'al line is had in conformity with the curve of spec, or the occlusal curve;

Figure2 is a diagrammatical view, showing the relation of the lines rx, yy, and z-e, with respect to a human. skull;

Figure 3 is another diagrammatical view, showing an enlargedtracing over the alveolar ridge of the left mandible, in the region of the second molar, bythe use of five tracers, two buccally to the alveolarridge 1"r andthree lingually to the central mandibular ridge, which tracers give the base and form for the carving of the fissures and cusps, i. e., the occlusal surfaces of the teeth, in relation to which the. left and right sets of posterior teeth of the inferior set are generated;

Figure 4 is a sectional view through superior and inferior dentures, showing the lateral movement of the mandible in the process of mastication, the right hand side being assumed to be the non-working side and demonstrating how the palatal cusps of the superior molar teeth passes upthe central ridge between cusps of the opposed inferior molar teeth, thus equalizing the forces over the dentures which, otherwise, would be more or less concentrated on the working side.

Figure 5 isan enlarged cross-section of a superior; and'an inferior tooth. in occluded state, the dottedline indicating the outline of a normal superior molar and showing how the cusps of the instant teeth are moved more to the median line; thus permitting more force to be brought on the molars;

Figure 6.- is aview similar to that of Figure 5 and illustrates how food is crushed or cut as the buccal cusp, of the superior molar, comes into contact with the central ridge of the inferior molar, following which, the food is caught by the tongue and thrownu-pand over the inferior molar teeth for further. mastication;

Figure 7 is a lingual aspect of the molar teeth in relation to the central incisors, in the process of incising or biting, i. e., protrusive position of the mandible, incision; being obtained without loss: of valance and the mandible returning to its normal position of rest, as shown by the dotted lines;

Figure a is the buccal aspect of the molar teeth in centric occlusion, and Figure. 9 that of the lingual surfaces;

Figure 10 is a view similar to that of Figure 9, but showing the teeth in protrusion position, with. all of the cusps in contact;

Figure 11 is a posterior view of the superior and inferior first molars: in occlusion;

Figures 12 and 13 are buccal aspects of left blocks of the superior and'inferior molars, respectively, showing the occlusal portions of the surfaces thereof;

Figure 14 is an exploded view of the superior and inferior, as shown enblock in Figures 12 and 13, the several teeth being individually enlarged to better illustrate the occlusal surfaces, 1. e., ciisps, fissures, grooves, etc.;

Figure 15 is an enlarged view, somewhat in perspective, showing the occlusal surfaces of the superior second molar; and,

Figure 16 is a view similar to that of Figure 15, but showing the occlusal surfaces of the inferior second molar.

Referring to the drawings in detail, it is first to be noted that the instant invention is concerned only with the construction and mountings: of artificial posterior teeth (bi-cuspids and molars) and, in proceeding with a detailed description of superior and inferior sets at one side of the dentures, it is to be understood that such description will apply equally to like sets at the opposite sides. of the dentures; the first and. second bi-cuspids and the first. and second molars of a superior set having. the general designations 2Q, 23, 2.5, and 21, and those of an inferior set, 22, 24, and 28, respectively.

The principles involved in the present invention. are as illustrated in the several views of the drawings; Figures 5., 6, 8, 9, and 11, showing the occlusal relation of superior and inferior sets of the posterior teeth; Figures '7 and 10, the protrusive or incising; Figures 4 and 6, the side or lateral; and Figures 3, 4, 5.. 6, 7, and 10, positional movement of the mandible and/or of the teeth. In the generation of the teeth, tracings are made upon the face of a block of new stone and the plan of the. several teeth is then outlined thereupon with reference to the tracings of Figure 3, wherein #4 represents the alveolar ridge of the left mandible, after which, the material about the tooth outlines is carved away, leaving the approximate teeth forms which may be thereafter separated, if desired, and retouched or carved to the required finished configurations.

Considering first the general form and construction of a denture, in accordance with the invention and as best shown in Figures 4 through 6, the crown 33 of each posterior tooth is made to the general configuration of its corresponding natural tooth but with the neck portion 3| substantially eliminated to provide a broad base 32 for seating, on a base-plate 30, which has the tooth supporting portion 39. shaped in the usual manner to snugly engage over and seat upon the gingivae and to provide a flattened surface for the teeth bases; In linear extent, the opposite portions of the teeth supporting surface, upon which the right and lefts sets of bi-cuspids. and molars are to'be emplaced, are also made to conform to the curve of spec (yy of Figures 1- and 2) as determined from the use of a co-ordinate template B; usual to the practice, and any suitable method. and. means will be employed to anchor the teeth in place thereon. Likewise, and as shown in Figures '1, 9 and 10, the base surfaces 32 of the sets of posterior teeth. are shaped, in continuity along the combined. length. of their juxtaposed assembly, at the varying curvature that defines the aforesaid curve of speew (y-y of Figures 1 and 2), which curvature is a natural one and necessary to a proper performance of the masticating function of the mandible and to prevent interference from the occlusal surfaces of the teeth. By thus having the supporting surfaces-of the base-plate and of. the teeth conforming one tothe-other in. the manner indicated, and the occlusal surfaces of the teeth made in accordance with the invention as will be hereinafter explained, the masticating forces and pressures will be equalized over these'surfaces by being directed axially of the teeth at all times and thereby' prevent any dislodgement of the dentures from positions of proper emplacement.

Since each posterior tooth, in a set of natural teeth, is differentiated from another and therefore is dependent upon its relation to adjacent and opposing teeth for its masticating efficiency, in order to design artificial posterior teeth of greater or more perfect mechanical efficiency, it is necessary that all of the teeth of a set, right and left, superior and inferior, bear a definite relation to each other, and embody certain refinements in structure. To such end, the crowns 33 of the present teeth are made appreciably higher at their buccal sides than at their lingual sides, consequently, the inferior molar cusps will appear higher at their buccal sides than at their lingual sides, owing to the medium incline zz (Figures 1 and 2) when set to the curve of spee y-y; accordingly, the palatal cusps of the superior molars appear lower. lso, the occlusal surfaces of all of the several posterior teeth are madewith cusps more or less normal, as is usual with natural teeth at the time of their eruption, and, consequently, with equal fissures and excursion canals. These cusps, however, are made to substantially round and conical form, so that their surfaces present opposed inclined planes in all lateral directions of movement of the mandible and in a manner that no point of positive rest or support is permitted to the cusps of opposing teeth. Each inferior molar, with its cusp points of contact with the template B, facilitates the setting up of these teeth mechanically correct; the first and second bi-cuspids having a two point contact with the template, while the first and second molars a three point contact,

it being noted that the distal lingual cusp of each of the molars are not as high as the other three cusps thereof. 1

In carrying out the objects and purposes of the invention, and as will be seen, for instance, by reference to Figures 8 and 9, the teeth of one set, right and left, are so formed and positioned as to be longer than those of an opposing set, the lower second molar 28 being made to a slightly greater length, mesial to distal, than that of the other molars, of which the first molars 25 (upper) and 26 (lower) are made to substantially equal length, while the second molar 21 (upper) is of substantially less length than that of the first molars. Thus, an inferior set of four posterior teeth, when in assembly, will have a combined over-all length substantially greater than that of the opposing superior set, the difference, as shown, being approximately equal to one-half the width of the first bi-cuspid 22 (lower). With reference to Figures 5, 6, and 11, it is to be noted that the width of the superior molar teeth and that of the inferiors is approximately the same.

As is best shown in Figures 14, 15, and 16, the occlusal surfaces of the posterior teeth of the left superior and inferior sets thereof, are as follows: The first superior bi-cuspid 2i, as usual, has two cusps A (buccal) and A (palatal), separated by a fissure or groove A the anterior surface of the buccal cusp being roundingin form, while'the posterior surface has a plane A which articulates on an anterior plane b*, of the inferior second bi-cuspid 24, and the fissure or groove over central ridges a and b respectively of the first and second inferior bi-cuspids 22 and has two cusps B (buccal) and B (palatal), separated by a fissure or groove 13 which are more rounding than those of the bi-cuspid 2|; the fissure or groove articulating over the distal. central ridge b of the inferior second bi-cuspid 24, and the anterior surfaces 0 of the inferior first molar 26. The buccal cusp B articulates between the buccal cusps b and 0 respectively of the inferior second, bi-cuspid 24 and the first molar 26, and the lingual cusp B between the lingual cusps b and o The superior first molar 25 is provided with four cusps C C (buccal) and C C (palatal), separated by crossed fissures and grooves C C C C", and C the pairs of cusps C C and C C by the fissures or grooves C C and C and the pairs C C and C C by the fissures or grooves C", 0 and C", the fissures or grooves C" and C constituting an excursion canal or spillway 29 (Figure 5) between the individual cusps of each pair. The anterior buccal cusp C is sharp at its crest, and has for its posterior surface a plane C and its anterior surface made more rounding, it articulating between the cusps c and c of the inferior first molar 26, while the palatal cusp C a more rounded form, articulates between the cusps c and c of the inferior first molar 2,6. The distal buccal cusp C has an anterior plane C and a distal or posterior plane C and articulates between the cusps c of the inferior first molar and d of the inferior second molar 28. The distal palatal cusp C is not as defined as the anterior palatal cusp C and articulates between the cusps c of the inferior first molar 26, and the cusp d of the inferior second molar 28. On the central anterior portion of the superior first molar 25, is a plane 0 separated from the cusps C and C by two fissures, grooves, or excursion canals C and C", which unite in the center, forming a Y with the fissure C and articulates over the fissure c of the inferior first molar 26. The distal buccal cusp C and the palatal cusp C articulates in the introdental space between the first and second inferior molars 26 and 28 and on the distal plane 0 lying on the central line :fl-m between the fissures 0 and c. This distal plane C in the movements of the mandible, is passed by the fissure, groove, or spillway d d of the inferior second molar 28. The second superior molar 2'! (Figure 15) likewise is provided with four cusps D D (buccal) and D D (palatal) which are separated by crossed fissures or grooves D D", D D and D while the cusp pairsD D and D D by the fissures or grooves D D and D with the fissures or grooves D D constituting excursion canals or spillways between the individual cusps of each pair. The cusps and planes of this molar are similar to those described in connection with the superior first molar 25, with the exception of a plane D which is not divided by a fissure; also the buccal cusp D and the palatal cusp D are closer to ether than those of the first molar and they articulate over a posterior central cusp D, of the inferior second molar 28 (Figure 16).

The first inferior bi-cuspid 22 has two cusps c (buccal) and a (lingual), separated by a fissure or groove 11 which extends about two thirds of the width of the occlusal surface where it divides, forming a Y, separating a small central cusp or ridge a having two planes a (buccal) and a (lingual). The buccal cusp a has on its anterior surfacea lane al and on itsdistal sur;

amasseface a small plane (not numbered), while the lingual cusp a is rounded; the height of both cusps being the same from buccal to lingual, ex-- cept for the fissure or spillway a separatin them. The second bi-cuspid 24- likewise has two cusps b (buccal) and b (lingual), separated by a fissure or groove 12 and a central ridge b which run mesial to distal of the occlusal. surface, the fissure being lingually of the ridge. The buccal cusp b has an excursion plane b on its anterior surface and plane (not numbered) on its distal surface, the crest of this cusp converges with the central ridge b on the central line af while the lingual cusp b is more or less rounded, somewhat like the corresponding cusp of the first b-i-cuspid 22, and both are of substantially the same height. The: central ridge or cusp b has two planes, oneat each side of this crest, the buccal b and'the lingual b", on the mesial, plane b buccally, and lingually, the fissure or spill'way b The occlusal surfaces of the inferior first and second molars 26 and 2 8 are substantially the same; hence a general description of the occlusal surface of the first molar 25 will be followed by a specific description of that surface of the second molar 28 and will therefore apply to both molars. The first inferior molar 26 has four cusps, two buccal c c and two lingual c a, separated by fissures or grooves, the pairs 0 c and c c, by the fissures c and 0 and the pairs 0 c and c 0 by the fissures or grooves 0 c and 0 the same constituting excursion canals or spillways between the individual cusps. The second inferior molar 28 (Figures 14 and 16) is formed with major cusps d d (buccal) and d d (lingual), and a minor cusp 01 The anterior buccal cusp d and the like lingual cusp cl are of the same height and are centrally divided by a fissure or spillway d. The mesial surface of the cusp d is rounded and has a short fissure al leading tothe central line xF-afl, and on its distal surface, a plane d which is divided by a fissure or excursion canal d from an excursion plane (1 of a central occlusal ridge 01 The distal buccal cusp d has a large excursion plane d mesially and extends to the crest of the central ridge and is divided from the excursion plane (2 by an excursion canal or spillway (1. This cusp has a distal plane d which is more inclined and smaller than the plane (1 and is divided from a plane a, of the distal centralridge r1 by a fissure or excursion canal d. The ridge (1 has another plane 01 separated from the buccal and lingual cusps d d by fissures ri and (Z forming a V. The distal lingual cusp d is not as high as the other three cusps, and is divided from the central ridge d by the connected fissures (1 and c1 constituting an excursion canal. This cusp has two planes, alarge anterior excursion plane (1 and a smaller posterior plane 11 The lingual mesial cusp (F, as before stated, is of substantially the same height as the buccal cusp d and is larger than the distai lingual cusp d its crest having a little incline only at its center, Where it is divided from the buccal cusp d by the fissure or spillway d". The mesial surfaces are rounding and have a spillway d ,'which is an extension of the spillway d The distal surface has a plane (1 which is divided from a plane (1 by an excursion canal a3 branching off from the spillway dflthe latter separating the cusps d and (1 The fissures or grooves c1 and d branches out from the fissure or groove d, to either side of the distal central cusp (Z separating it from. the major cusps d and d; it being here noted that this minor cusp is dis-- posed. in the plane of the central ridge (1. the latter being. defined by the tracing line r-r on Figure 3 of the drawings. The central ridge 11 as best shown in Figure 16; begins a little buccally of the central line :v -m (Figure 14) and the crest of the distal buccal cusp d and terminates at the crest of the mesial lingual cusp d where it is divided from this latter cusp by the excursion canal (1 The ridge is somewhat lower at about half of its length, or at the point where the canals 01 and d unite at its crest. The occlusal surfaces oi the superior first and second molars 25 and 2? are also substantially the same and, generally, the second molar 21 has four cusps D D (buccal) and D D (lingual), separated by fissures, grooves, or spillways, D D", D D 13, D and D the pairs D D and D D, by the spillways D D D D and D and the pairs D D and D D by the spillways D D", and D Other details as to the cusps, fissures and planes, are as described in connection with the inferior second molar 28, Figure 16.

With the occlusal surfaces of the superior and inferior, right and left, sets of the posterior teeth so formed, it will be seen, by reference to Figures 8, 9, and 14, that the buccal cusp a of the first inferior bi-cuspid 22, articulates between the buccal cusp A of the first superior bi-cuspid 2|, and the opposed crown of the adjacent canine tooth (not shown); while the buccal cusp 12 of the inferior second bi-cuspid 24, articulates between the buccal cusps A B of the superior bi-cuspids 2| and 23. Similarly, the anterior buccal cusp c of the inferior first molar 26, articulates between the buccal cusp B of the superior second bi-cuspid 23, and the anterior buccal cusp C of the superior first molar 25; while the posterior buccal cusp c of the inferior first molar articulates between the anterior and posterior buccal cusps C and C of the superior first molar 25. Likewise, the anterior buccal cusp d of the inferior second molar 28, articulates between the posterior buccal cusp C of the superior first molar 255 and the anterior buccal cusp D of the superior second molar 21, and the distal buccal and the distal palatal cusps D and D of the superior second molar 27, function over the distal central cusp d, of the inferior second molar 28.

By reference to Figures 14, 15 and 16, it will readily be seen that the fissures or grooves separating the cusps of the several teeth merge one into the other, and those designated A B of the superior bi-cuspids 2! and 23, and a b of the inferior bi-cuspids 22 and 24, form substantially continuous channels between the buccal and lingual cusps and extending along the lines x-x (Figure 14). The formation of these fissures or grooves, however, are not regular but are made more or less irregular by certain intercostal angled planes for the purpose of increasing the mechanical efficiency in bite balance and grind. This irregularity ma be emphasized in the formations in the inferior teeth'over those in the superior teeth and to an extent to provide the first and second inferior bi-cuspids, as well as the first and second inferior first and second molars, with certain central cusps or ridges that function within the fissures or grooves of opposed superior teeth. The fissure or groove formations are additionally to be observed in Figures 3 and 12 but, with particular reference to Figure 16, showing the occlusal surface of the inferior second molar 28, it is to be noted thatthe mesialbuc- .9 cal, distal buccal, and the mesial lingual, cusps d 11 and (P, are of the same height and make contact with the template B (Figure '1), either if curved or straight, in the procedure of setting them up. The cusps d and (Z are less in height and size. The anterior buccal cusp d is formed with a rounded mesial surface that is in continuation with the surface of the crown, while its distal side is formed by the excursion plane d, and its crest extends buccally-lingually at the same height to the central line re -m where it ends and is divided from the mesial lingual cusp (F, by the spillway d. The mesial lingual cusp d is also a rounded one and is provided on its mesial side with the excursion canal d which is an extension'of the spillway d its crest running lingually to the central fissure or spillway d", with a slight incline. The oppositely inclined planes (1 and 11 respectively of the mesial and distal lingual cusps d d constitute the lingual part of the fissure or groove (1 which serves as an excursion canal or spillway for food in the lateral movements of the mandible, which food is caught by the tongue and thrown back onto the inferior molars for further cutting and grinding. The bases of these planes (1 and c2 merge into the excursion planes at and d respectively, on

which the mesial palatal cusp D of the superior second molar 21 functions in the anterior, posterior, and lateral, movements of the mandible; the planes d and d also form the lingual surface of the central ridge (1 The side of the distal lingual cusp d opposite its inner plane surface 01 is constituted in an excursion plane d and a canal 11 upon which and within which the distal palatal cusp D of the superior second molar 21, functions. The distal central cusp (Z is formed by oppositely inclined excursion planes cl and d over which the'distal buccal and distal palatal cusps D and D of the superior second molar 21, functions; the bases of these planes merge into an excursion plane that extends about the base of the distal lingual cusp d and merges into the inclined plane 01 of the latter, and. also, into the aforesaid excursion plane (1 The planes c1 and d, of the cusps (Z and 11*, respectively, are also oppositely inclined and form between them the posterior, lingual, branch d of the fissure or groove d The opposite sides of the posterior buccal cusp d are constituted in inclined planes c1 and d, the plane d being the larger and extending to the centralridge'ol and to the anterior buccal planed, of the central ridge, from which it is divided by the excursion canal (1 As before stated, the central ridge (Z extends from the inner crest of the posterior buccal cusp d to the approximate center of the anterior lingual cusp'd i The buccal planes of the central ridge (Z consist of the plane .11 an- -terior buccal cusps d and d respectively, constitute the buccal part of the fissure or groove d which serves as the excursion canal or spillway 29 (Figure for food, during masticating movements of the mandible. The excursion plane (1 inclines upwardly and lingually from between the excursion planes d and d and forms, with the oppositely inclined planes (1 and d, a central cusp, a part of the central ridge d at their points of mergence. This cusp or ridge d lies substantially in the plane of the central ridge line r -a: (Figure 14), as does also the mesial fissure d and the distal central cusp 11 The normal height and substantially sharp cusp formations of the several posterior teeth, in accordance with the invention, materially changes the usual grinding action, which, in some instances, amounts to but little more than a mashingaction, especially in many of the hitherto known forms of artificial posterior teeth, into a highly 'efficie'nt" mechanism for both cutting and grinding food, without any interferenceor interlocking efifects whatsoeveroccurring between opposed'occlus'al surfaces to disturb normaldenture plate or tooth position. This cutting and grinding effect, obtaining from the proposed modified cusp formations, is augmentedby the added structural features resident in the aforesaid central cusp and ridge formations, the latter, by reason of the angular arrangement of the several excursion planes; enu'rnerated in connection with the description of the inferior second molar 23, having knife-like food cutting action .4, 5 and 6.

the several teeth of each set, is so formed as to fit over the crests of the jaws, so that all masticating pressures are uniformly distributed over the same. Also, it is to be noted that the major cusp formations slide freely in and out of the crossed fissures and grooves, in all lateral directions of mandible movement, without resistance,

and that, even when the aforesaid intercostal cusp and ridge formations are present, thus clearly distinguishing these teeth forms from those of the prior art, wherein the cusps of certain teethdo not articulate within depressions in opposed teeth. The? buccal cusps of the instantinferior'teeth appear slightly'higher than the lingual cusps, when'set to the curve of spee. This is to be clearly Seen by reference to Figures- In lateral movements of the mandible, the anterior teeth have a larger radius of movement than that of the last or second molars and, in providing each of the inferior of the latter with the distal central cusp d33, a

rocking orpivotal support is obtained between the same and the superior second molars on the non-working sides of the dentures, during mastication. The distal central cusp (133 also serves as a guide in the setting up of the companion teeth of each set.

Inv order to prevent injury to the gum tissues through biting or cutting, the teeth of the superior set are provided with bulges or plumpers 34, which are formed on their buccal faces and auction to hold the tissues spaced from the latter suificiently to avoid engagement with the buccal cusps of the teeth. It is also to be noted that, as is to be seen in Figures 5 and 11, that the buccal cusps and the palatal cusps are substan- Many closer to 'themedianline,.thusbringing the center of forcemesially to thealveolar ridge; the.

.dotted line 35 (Figure .5) being representative of the natural tooth form. Similar bulges or plumpers may be provided on the outer faces of the gingivae en a ing ;'p.0rtions of the plates 30, for like purposes, but without-quite the emcientresultsxto be desired, byreason of the necessarily increased distance between their location with respect to theocclusal surfaces of the teeth.

From the foregoing, it will be evident that these im roved posterior teeth have proper slopes which permit of free lateral and bi-.la.teral,move

:ments of the :mandible and without interference,

such as has condemned .cusped :teeth heretofore known, and that the height of the cusps may be varied to meet :varied oral .:oavity formations while maintaining the salient principles and structural features enumerated .herein.

Having this fully described :my improved posterior teeth, the structural features thereof and the method of evolving the same,::it is to be understood that the improvements .reside in the teeth taken individually, or in collective :combination, :and that I do not :restrict myself to the exact details of construction and procedure, as has .been more :or less specifically stated herein, throughout :an approachable range, 'without de parting :from the spirit of the .invention or its scope as claimed.

What I claim is:

'1. In combination, :an inferior 'molar and a superior molar, said inferiormOlar having a pair each of buccally and lingually disposed cusps separated mesial-distally by relatively shallow fissures disposed substantially in longitudinal alignment and by a .relativelyflarger transversely extending groove, a central ridge dividing said groove and formed toiprovide oppositely inclined planes, said ridge extending substantially longitudinal, the walls of'said groove at opposite sides of said central ridge being formed by oppositely inclined planes .at the inner sides of said buccal and lingual cusps, the inclined planes 'of'said buccal cusps being inwardly divergent and those of said lingual cusps substantially parallel, a distal central cusp formed .to provide oppositely inclined planes, the crest of which forms a substantially longitudinal ridge extending in substantial alignment with said fissures and substantially continuous with the 'firstrnamed ridge, the outer side. of the adjacent distal buccalcusp having :the form of an inclined plane. extending diagonally inward and terminating :at the inner end of the last named 'ridge, the outer side .of the adjacent lingual cusp formingan inclined plane extending substantially parallel to the last of said ridges, :and said "superior molar having pairs of buccally and lingually arrangedcusps separated by longitudinal and transverse grooves, said longitudinal groove normally seating over said ridges of theinferior molar, with the :mesial :buccal and lingual cusps engaged in said large grooveat the opposite sides of said central cusp of the latter and the distal buccal and .lingual cusps in spaces formed between the outer sides of the corresponding-cusps and the adjacent sides of the'distal central cusp of the inferior molar.

2. In a replacement for combined .lost superior and inferior molars and bicuspids, artificial su perior and inferiormolars as defined .in claim .1, in combination with artificial superior and inferior bicuspids,.saidinferior bicuspids each ihavinga buccal and a lingual cusp separated by a longitudinal fissure extending inwardlyfrom the mesial side .to .a meeting point with a central ridge :for-mation extending inwardly from the distal side and in substantial alignment therewith, said fissure continuing and diverging .lingually and terminating at the .distal side, .said central ridge formation being in substantial alignment with a ridge formation extending longitudinally of the inner side of .said =buccal cusp, and said superior bicuspids each having a bucca-l and a lingual cusp separated by a longitudinal fissure or groove whicharticulates over the ridge formations of the inferior bicuspids, the central ridge formation of both the inferior molars and bicuspids being in substantial alignment. 3. In a replacement for combined lost superior and inferior molars and bicuspids, artificial superior and inferior molars as defined in claim 1,

I wherein the mesial buccal, distal buccal and the mesial lingual cusps are of the sameheight and so arranged as to make contact with a template employed in the procedure .of setting up the teeth, and the distal central cusp of the last inferior molar provides .a balancing support between the last superior and inferior molars on the non-working sides of the dentures during mastication.

ROSS .O-. wDICKSON.

REFERENCE S CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number .Name Date 1,281,352 Gysi Oct. 15, 1918 990.518 Gysi Apr. 25, 1911 2,050,837 Gysi Aug. 11, 1936 1,879,419 vMyerson Sept. 27, 1932 2,072,127 Pilkington et a1. Mar. .2, 1937 2,308,553 Steele et al. Jan. 19, 1943 FOREIGN PATENTS Number Country Date 16,556 British July 18, 1911

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