US2591678A

US2591678A - Denture locating mechanism

Info

Publication number: US2591678A
Application number: US725045A
Authority: US
Inventors: Donald V Cleman
Original assignee: Individual
Current assignee: Individual
Priority date: 1947-01-29
Filing date: 1947-01-29
Publication date: 1952-04-08
Anticipated expiration: 1969-04-08

Description

5 Sheets-Sheet 1 Filed Jan. 29. 194'? III! ' April 8, 1952 D. v. CLEMAN 2,591,678

DENTURE LOCATING MECHANISM Filed Jan. 29, 1947- 5 Sheets-Sheet 2 3nventor 00/1 40 1 amw/z/ 32 3 Q an ooooo n:

Filed Jan. 29. 194? DENTURE LOCATING MECHANISM '5 Sheets-Sham 3 A IIII'IIIIIIII I Snnentor (Ittornegs' Patented Apr. 8, 1952 UNI T-E D S TATES FAT-E'NT OFFICE zDENTU-R-E LOCATING- MECHANISM Donald V. "Cleman, Bremerton, Wash.

Application January 29, 194-Z,*Serial No. 725,045

(iCl."32-2) 1'5.Claims. .1 This invention relates to an improvement .in dentures, and more specifically to locating devices constituting 1 guide and bearing mechanism, which :-may be incorporated in.dentures -.for the purpose of increasing the efiiciencyof .operation .of such dentures :and reducing .the .possibility of one or both dentures being displacedor injured by improper articulation during biting or chewing.

Dentures are maintained inplace inthe mouth of the wearer by suction. The security with which dentures areretained on the gums, therefore, depends .upon the degree of vacuum which can be maintained within the gum-receiving re- .cesses ofthe dentures, and this in turn is deter- .mined by the accuracy with which the dentures .fit. Because, .after a persons teeth are pulled,

the gums undergo a progressive shrinking action over a substantial period of time, it is difficult to maintain a good fit between the denturesand the gums, even .though the dentures may be re- .placedi-or refitted at frequent intervals.

I wear is :often very discouraging.

It-is an object of this invention .to improve the efficiency of denture operation, particularly-during the initial adjustment period of their use, and to reduce the discomfort and annoyance caused by inadvertent displacement'of the den- .tures during eating. To accomplish this object guide and bearing mechanism is provided 'for the dentures'to insure .that the upper and lower teeth will articulate properly as the jaws are closed, and to afiord a bearing action which will resist displacement of the dentures from the gums when stress is placed on themduringbiting or chewing.

Another object of the invention is to incorporate locating mechanism in dentures which will effect cooperation between the upper and the lowerteeth, atleast one set'being carried by a denture, without requiring a bulky attachment for either set of teeth, and which will not require interconnection of the upper an'd'lowerdentures, but will leave each separate as a complete'unit, as are conventional dentures.

An additional ob'jee'tis to incorporate bearing and guide mechanism in the denturesas an -integral .part of them, although such'devices may, likethe teeth, be preformed and embedded'in the v"denture plate material, or the material of the plates themselves may 'be formed to constitute the bearing and guide devices.

'While in referring to my improvement the word mechanism has been used in abroad sense, an advantage of my invention is that-it .need incorporate no moving parts exceptfin "the .sense that relative movement between the upper and lower teeth occurs duringbitingor chewing action.

Additional .and more specific advantages of .myQinvention .w'ill'bepointed out in the,,,specific description of its various representative Ijforms shownin the accompanying drawings.

, Figure 1 is a side elevation view of upper and lower dentures .in jaw-closed relationshipshowing one .form of my guide and bearing mechanism; .Figure 2.is a transverse-section lthrough the upper .and lower dentures, "taken along ,line

.2-2 of Figure 1, showing the Jdentures in jjawclosed .position, and Figure 3 is a similar view showing the denturesinpositions displaced relatively transversely andpar'tially opened, apposition characteristically assumed during chewing. Figure 4 is a fragmentary sectional view on line 1-4 of Figure -2, showing 'thedenturesiinTjaw- .closed position, and Figure 5 is a similar view withthe teeth. in partially open position in which the lower ,jaw .is protruded forwardly. 'Figurefi is afragmentary top perspective view of the le'ft rearward portion of the lower denture of "Fig "'8. Figure 10 is an end elevation .view' of such a .cavity element, Figure :11 "is 'a-bottom plan view of that element, andFigure "12 is a central "longitudinal section through "such element.

Figure'lB is a side -elevation view" of 'fa*proj'ec- "tion .element of the type shown incorporated in 'd'enturesinfFigures .1 to 5 and-'7. "Figurel 'isa side elevation view of such projection element -taken at '90 degrees to' the "view of Figure -1"-3, "and Figure 15'' isa 'bottomgplanwiewof the'same pro- 13' ecting element.

.lFigure '16 'is an inner side -'elevation view of a cavity element, similar to that shown in Figure 9, but made of different material. Figure 17 is an end elevation view of such element, and Figure 18 is a bottom plan view of the same element.

Figure 19 is a side elevation view of a projecting element similar to that shown in Figure 13. Figure 20 is a side elevation view of the same element taken at 90 degrees to the view of Figure 19, and Figure 21 is a bottom plan view of the element.

Figure 22 is a side elevation view of upper and lower dentures in jaw-closed relationship incorporating guide and bearing devices of a type different from that shown in Figures 1 to 8, inclusive. Figure 23 is a side elevation view similar to that of Figure 22, but fragmentary in character and showing the dentures in positions relatively displaced to correspond to disposition of the, jaws in somewhat open position, with the lower jaw protruding. Figure 24 is a transverse sectional view through the dentures taken at the location of line 24-24 in Figure 22, but corresponding to the illustration of Figure 3 in showing the dentures displaced relatively sidewise and in slightly open position. Figure 25 is a top perspective view of a lower denture of the type shown in Figures 22 and 24. Figure 26 is a fragmentary sectional view through the rearward portion of an upper denture, taken along line 26-46 of Figure 24.

Figure 27 is a side elevation view of upper and lower dentures in jaw-closed relationship, illustrating still a different type of bearing and guide mechanism, in accordance with my invention. Figure 28 is a.transverse sectional view taken substantially at the location of line 2828 of Figure 2'7, but showing the dentures displaced relatively laterally and slightly opened. Figure 29 is a longitudinal sectional view through similar dentures taken substantially along line 29-29 of Figure 28, but showing the dentures in jaw-open position, in which the lower jaw is protruded forward. Figure 30 is a top perspective view of the lower denture of the type shown in Figures 27, 28, and 29.

This application is a continuation in part of my application Serial No. 688,209, filed August 3, 1946, now abandoned, the form of my invention disclosed in that application being shown in Figures 27 to 30, inclusive, of this application.

In operation all modifications of my locating mechanism afford bearing engagement preferably between both rear portions of the dentures in various open positions within limits when the lower jaw is protruded, as in manipulation of the Y jaws for biting with the incisor teeth, or when moved sidewise as in masticating. The two principal functions of the mechanism which should be kept in mind in studying the following description are, first, that a bearing action is afforded when the jaws are opened partially and the lower jaw is thrust forward or moved sidewise, and second, as the jaws are being closed the upper and lower elements of the guide mechanism will contact prior to closing of the upper and lower teeth if they are not in proper articulation, and during continued closing movement of the jaws engagement of such coacting elements will wedge the denture or dentures in a direction either sidewise, or forwardly and rearwardly, or both, as may be required to bring the teeth into proper articulation at the time they close. Such action will be accomplished automatically, and perhaps without the wearer even being conscious of it, but it is preferred that the action of the locating mechanism be sufliciently positive that the wearer cannot, even by conscious effort, close his jaws to engage the upper and lower teeth in other than proper articulating relationship, except to contact the upper and lower incisors.

In the preferred form of locating device or projection and recess mechanism shown in Figures 1 to 6, inclusive, the upper denture I and the lower denture 2 are of generally conventional construction, except that each denture may have only one molar at each side, designated [0 in the upper denture and 2!] in the lower denture. The particular number and arrangement of the teeth in the dentures will vary with different cases. In some instances no molars may be used,

whereas in other cases room for two molars at each side of the upper and lower dentures may be afforded. Generally, however, the location of the cooperating locating elements will be sufficiently far rearward to permit the inclusion of a molar at each side of each denture-although seldom will such mechanism be located sufficiently far rearward to afford room for two molars at top and bottom on each side of the dentures.

In the preferred form of my invention the hearing and guide elements consist of a projection element 3 in one denture, shown as mounted like a tooth embedded in the plate material, which coacts with a cavity element 30 incorporated integrally in the other, also shown as embedded in the plate material in the same manner as a tooth. These elements usually are substituted for the second molars, as discussed above, and are purely guide elements, having no masticating surfaces. In the particular embodiment of the invention shown in Figs. 1 to 6 the projection element is mounted in the upper denture immediately behind the molar l0, and the cavity element is mounted in the lower denture immediately behind the molar 20. As will be seen best in Fig. 5, the projecting element is inclined forwardly and downwardly, and when the upper and lower dentures are in registry laterally, the rearward portion of the projection tip contacts the bottom of the valley in the cavity element, which also is inclined forwardly and downwardly. It is important that the zone of contact between the cooperating locating elements be inclined forwardly and downwardly so that, when the jaws are opened, the lower jaw may be protruded forwardly to locate the lower incisors ahead of and below the upper incisors in biting relationship, and the tip of the projection element will be in engagement with or close to the cavity element.

If the incisor tooth line is somewhat ahead of the gum ridges received in the denture cavities, the pressure on the object being bitten will produce a leverage action with the front gums acting as fulcrums. Such action will tilt the rearward portions of conventional dentures away from the gums, frequently striking the rear teeth together to produce an annoying clicking sound. If the projections 3 and cavity elements 30 are in engagement with movement will be prevented,

tendency is for the lower jaw in its .condylar .movementto move distally for articulation of its teeth with those of the upper jaw, for articulation of the upper and lower teeth. Corresponding relative movement of the dentures is insured by the wedgin nature of the guiding action between the projection and

cavity elements

3 and 30 eifected by their engagement. Such Wedging creates a rearwardly acting force on the lower denture and a forwardly acting force on the upper denture as the jaws are closed, thus assistingJthe .action of the gums engaged in the denture cavities, to shift the upper and lower sets of teeth into registry'so that all the teeth articujlate properly on closing contact, despite continuance of thepressure on the incisor teeth re- .quired to accomplish the biting action.

In order to preserve bearing contact between the projection element 3 and the cavity or recess element 30 during a very substantial degree of opening movement of the mouth without requiring excessive protrusion of the lower jaw, it is desirable that the forward and downward slope of the zoneof contact between these two elements be quite steep with respect to the general planes defined by the tips of the upper and lower teeth. Thus where the cavity element 30 is incorporated inthe lower denture, as shown in Figs. 1 to 6, inelusive, it is'desirabl for the rearward portions 2| of the lower plate which carry the cavity elements to be turned upward, as shown best in Figs. 4 and 5, forming a rearwardly and upwardly inclined track for the projecting element 3. In addition -the rearward central portion of each cavity element may be made thicker than its forward central portion so that the bottom or main track portion of the valley slopes forwardly and downwardly more steeply than does the upturned end of the lower denture from which it projects. The steepness and length of the track formed by the cavity element surface will determine the ex- 'mesiodistal direction determines whether or not the upper and lower teeth will articulate accurately'when both they and the locating elements main contact, as shown best in Fig. 4.

In'that figure and in Figure 5 the mesiodistally central-portion of the surface of the recess eletance beyond the masticating surfaces of the teeth, to preserve contact between the two projection elements 3 and ridges of the cavity elements 3!) when the upper and lower teeth are separated and moved laterally in chewing, as represented by the relative positions of the dentures shown in Fig. 3. It willbe evident that if the chewing pressure is exerted on the right side ment is shown as projecting altitudinally a substantial distance beyond the masticating surfaces of the teeth.

Thesame type of bearing and guiding action .is accomplished by my locating elements during relative sidewise movement of the dentures. In

masticating food, the jaws are moved principally whenthe wearer chews on one side of his mouth.

Transverse stability of the dentures is accom- "plished by my locating mechanism when the lower jaw is moved laterally or buccolingually "relative'to the upper jaw by making the cavity or recess-elements 30 transversely concave, as shown in Figs. 2 and 3.

The-ridges alon the opposite sides of the cavity members should be suihciently high, that is,

should project altitudinally a substantial disof the dentures, for example, the projection 3 and cavity 36 on the left side will be in engagement, or substantially so, to prevent or to limit to a negligible amount any tilting of the dentures laterally.

Actually, in chewing, the lower jaw is not shifted directly sidewise ordinarily, but is swung in some measure about an upright axis. The front of the lower jaw tends to swing toward the side to which the lower jaw is displaced, so that in its lateral movement the cavity or recess of the element 38 shown at the right of Fig. 3 would move not only to the left, but forward, so that the right rearward corner of its cavity would engage the tip of projection element 3. Conversely, the recess of element 30 at the left of Fig. 3 would move rearward as well as to the left, so that the tip of the projection would be engaged by the forward right corner of the cavity element.

Since, to preserve proper lateral balance, it is desirable for the lingual ridge of the left cavity element 33 and the buccal ridge of the right cavity element to contact their respective projections 3 simultaneously during chewing, it is desirable to increase the height of the forward portion of the inner ridge of each cavity element at 3 l, as shown in Fig. 6, and also to increasethe depth of the depression in the cavity element at the opposite, outer corner, as indicated at 32 in Fig. 6, because of the general forward and downward slope of the cavity, as shown best in Fig. 5. This formation of the cavity enables the lower jaw to swing through a reasonable angle as it is moved buccolingually, when the upper and lower teeth are separated slightly, while maintaining substantially equal contact of, or clearance between, the locating elements at opposite sides of the mouth.

As the teeth of the upper and lower dentures are moved toward each other while chewing, the engagement of projections 3 with the concave recesses of cavity elements 39 will produce a wedging force urging the lower and upper teeth toward registry as the jaws are closed, so that when the teeth actually come together they will articulateproperly, as shown in Fig. 2 It will be evident, therefore, that the cooperatin locating elements constitute universal guiding mechanism for wedging the upper and lower teeth into proper articulating relationship both mesiodistally and buccolingually, as may be necessary to bring the teeth into accurate articulation when they reach closed position.

In the embodiment of my invention shown in Figures 1 to 6, inclusive, which has been described above, the projections 3 are incorporated in the upper denture, whereas the cooperating cavity elements 38 are carried by the lower denture. Alternatively the projection elements may be carried by the lower denture, as shown in Fig. 7, and the cooperating cavity elements by the upper denture, as shown in Fig. 8. Despite this reversal it is necessary that the zone of contact between the projection and cavity elements be inclined forwardly and downwardly, because of the mobility of the lower jaw which effects the relative movementbetween the upper and lower teeth. To provide the desired type of locating, bearing, and guiding operations, therefore, it is necessary in this form for the projections 3' ol Fig. 7, extending altitudinally a substantial distance beyond the masticating surfaces of the teeth in the lower denture, to be inclined rearwardly, particularly since they are mounted on the upturned ends 2| or the plate material. The cavity elements instead of projecting at the rear altitudinally beyond the masticating surfaces of the teeth in their denture as in the form of Figs. 1 to 6, are depressed at the rear behind their forward portions, and altitudinally behind the masticating surfaces of the teeth in its denture.

To equalize the occlusion of both projection elements 3' on the lower denture with the cavity elements 30 on the upper denture as the lower jaw is moved laterally and swung, in the manner previously described, the depression of the cavity element may be more pronounced at its inner forward portion than would otherwise be the case, as shown at 32' in Fig. 8, whereas the rearward portion of the outer ridge of the cavity element is raised at 31 more than would otherwise be necessary. The projections 3', carried by opposite sides of the lower denture, contact substantially equally with the cavity elements 30' carried by the upper denture, just as in the form of my invention previously described, and as the upper and lower teeth approach each other the Wcdging force produced by the occlusion of these lodating elements as the jaws are moved together, acting both buccolingually and mesiodistally,

force the upper and lower teeth into registry, s0

that upon occlusion they articulate accurately.

The plate material of which dentures are made at present is usually an acrylic resin. Into this plate material are embedded preformed teeth, either of porcelain or of acrylic resin. In the same way the projection elements 3 and 3' and the cavity elements 39 and 313' may be preformed to substantially final shape out of either porcelain or acrylic resin. If these elements are of porcelain, as illustrated in Figs. 9 to 15, inclusive, the base portions are curved concavely to conform generally to the gum curvature of the wearer, but in addition a cavity 33, preferably undercut, is provided in the central portion of the base, and holes extending through the base from its cavity to its exterior. When these elements are embedded in the acrylic resin plate material it flows into these cavities and holes, to lock the locator elements to the plate.

On the contrary, if the projection and cavity elements are made of acrylic resin, as shown in Figs. 16 to 21, inclusive, it is not necessary to provide any cavities or apertures for receiving acrylic resin plate material, because the material of these elements will be fused with the plate material when they are embedded in it while the plate material is hot.

. Just as corresponding teeth in various individuals are of somewhat different shapes, both the projection elements 3 and the cavity elements 3E1 will be preformed only to approximately the desired shape. For each individual case they may be modified by grinding, or they may be supplied in a reasonable assortment of sizes and shapes, just as are teeth to be inserted in dentures. Moreover, in order to insure that the projection and cavity elements coact to guide the upper and lower teeth into proper articulation, they may be ground to final shape by rubbing them together with grinding compound between them, either with the upper and lower dentures installed in an articulator, or actually placed in the mouth of the wearer. By this technique the generally conical projections 3 and the cavity elements 38 can be reducedto exactly the proper shape for each individual case.

In the discussion thus far it has been assumed that both the upper and the lower teeth will be mounted in dentures. In some cases, however, my invention may be applied to a lower or an upper denture used in conjunction with the other set of natural teeth of the wearer. Thus, for example, the second molar of a set of natural upper teeth could be crowned with a projection element like 3 of Figs. 1 to 5, inclusive, or a cavity element like 38' of Fig. 8, such elements could be incorporated in the wearers mouth as a bridge, or an attachment to the first molar replacing the second molar, or attached to the second molar and replacing the third molar or wisdom tooth. In either case the lower denture would be provided with cavity elements 30 or projection elements 3' located correspondingly and shaped to coact with the attachments to the natural upper teeth. Exactly the same occlusion between the .projection and cavity elements would occur to control the movement .of the lower denture and maintain it in proper place during biting and masticating operations as has been described in connection with the upper and lower denture locating element installation shown in Figs. 1 to 5.

Conversely, if only an upper denture were required, the second lower molars could be crowned with a cavity clement like 38 of Figs. 1 to 5 or with a projection element such as 3 shown in Fig. 7, or such elements could be secured as an attachment to the first molar to replace the second molar, or as an attachment to the second molar to replace-the third molar or wisdom tooth. The upper denture would then have projection elements like 3 or cavity elements like 30 shown in Fig. 8, located in corresponding positions and shaped to coact with the lower cavities or projections to maintain the upper denture firmly in place in the mouth during biting and chewing, and to articulate its teeth with the wearers natural lower teeth when the jaws are closed.

Instead of utilizin projection elements of generally conical shape, such as 3 and 3', the tips of these elements may be considerably more rounded as are the projections 35 shown in Figures 27, 28, and 29, although they are both of substantially circular cross section. To coact properly with them the recesses of the cavity elements 38 will not be as deep as are the recesses of the cavity elements 36 in Figs. 1 to 6. To guide the projections properly during masticating movement of the lower jaw, however, the recesses of the cavity elements should be deeper in their rearward outer portions, as indicated at 31 in Fig. 39, and the forward portions 38 or the inner ridges forming the recess sides should be raised, as also shown in that figure. In both instances the recesses of the cavity members are generally elliptical in shape.

Instead of preforming the projection and cavity elements as illustrated in Figs. 9 to 21, they may be molded to the proper shape con jointly with formation of the plate material to its desired conformation. The projection and cavity elements shown in Figs. 27 to 30 inclusive are fashioned in this manner. It will be evident, however, that the shapes of the locating elements thus formed may be like those shown in Figs. 1 to 7, inclusive, in which the projections are much 9. more pointed and. the'cavity recesses are. con,- siderably deeper to. accommodate. them. Thus the pointed type of projection protrudes altitudinally considerably beyond. the masticating surfacesof the teeth in their denture, as shown best. in.Figs...3i and whereas the more rounded tips of the projections when incorporated in the upper denture, as shown best in Fig. 29, are shown. as notprojecting appreciably beyond the masti'cating. surfaces. of the teeth in their. denture, in such case the cooperating cavity surface 31, shown in Figures 29. and 30, being the elements. which project altitudinally a substantial distancebeyond the. masticating, surfaces of the teeth in their jaw or denture. The general type of bear-ing and wedging operation effected by both forms of projection and cavity elements upon occlusion is the same, however, and such rounded tips may be formed to project beyond the masticating surface of the adjacent teeth if desired.

It is not necessary that the projection elements be of generally conical conformation, as

areelements

3 and 3 shown in Figs. 1 to 5 and '7, noreven of generally circular cross section, asare both such conical projections. and the more rounded projections 35 of Figs. 27 to 29'. An alternative shape of projection is the plate or blade type 4, shown in Figs. 22 to 25. This type of projection cooperates with a cavity or recess element 40, shown in Figs. 24 and 26.

The projection and recess elements of Figs. 22 to 26 occlude to perform, the same type of beering and guiding operation as do the projection and

socket elements

3 and 30, respectively, shown in Figs. 1 to 6, inclusive, and described in detail in connection with the locating devices of those figures. It will be noted particularly that the zone of occlusion between the projection and cavity elements defined by the edge 4| of the plate 4 slopes forwardly and downwardly, just as in the other modifications of my invention. This edge contacts the concave ridge 42 of the corresponding cavity or recess element. As shown best in Fig. 24, the plate edges riding on the cavity element ridges constitute bearing surfaces which coact at opposite sides of the mouth to balance the dentures when the lower jaw is shifted buccolingually during mastication.

As seen in Fig. 26, the rear portions of the cavity members 46 on the upper denture are depressed upwardly to afford space for receiving the tips of plates 4 when the dentures are in articulation, as shown in Fig. 22. The projection plate elements 4 are illustrated as preformed elements embedded in the upturned ends 2| of the lower denture, but they may be formed out of plate material. In this particular form of my invention the denture 2i need not be turned upwardly as long as they afford sufficient thickness for secure embedment of the plates 4 in them.

Because the lower denture swings, as well as shifting sidewi-se, when moving buccolingually during mastication of food, as has been discussed previously, it is desirable that the concave ridges 42 of each cavity element be inclined forwardly and inwardly, as shown in the sectional view of Fig. 26, instead of extending exactly crosswise of the denture. As the lower denture is moved to the left, as shown in Fig. 24, it will also be swung somewhat to the left, and the left end of the ridge 42 on the left cavity element 40 will ride farther back on the inclined edge of the left plate 4 than would be the case if the ridges ill ' plane.

42 of the two cavity elements 40 lay in the same Conversely; the left-end of the'ridge 42 on the right cavity element 40; :beingfo-rward of its right end, will ride on the contacted edge of the right plate 4 farther forward than would otherwise be the case. As a result, the ridges 42 of the right and left cavity elements 40 contact substantially corresponding elements of the plate edges 4|, as shown in Fig. 24, to maintain the upper and lower teeth substantially parallel in laterally displaced positions of the lower jaw.

It will be appreciated from the foregoing discussion that all of the embodiments of my invention illustratedinclude azone of occlusion between cooperating upper and lower locating elements located in the rear portion of the mouth, which zone isinclined forwardly and downwardly, and which elements'can occlude over a substantial range of" opening. movement of the upper and lower teeth, affected either by mesiodistal movement of thelower jaw,-as in-biting, or by buccolingual movement of the lower jaw which incorporates some degree of'swinging movement. as utilized in masticating food.

I claim as my invention:

1. In a, set of upper and lower teeth including at least one denture, guiding mechanism comprising cooperatingsets of track elements and track-engaging elements incorporated in the distal portion of theset of teeth, said track elementsdefining a path of substantial mesiodistal extent and inclined forwardly and downwardly, for engagement with said track-engaging elements during upward and, retracting mandibular movement from a position of the lower teeth out of contact with the upper teeth to exert a force urging the upper and lower teeth toward registering relationship during their closing movement.

2. The guiding mechanism defined in claim 1, in which the track elements are recessed and the bottom of the recess is inclined substantially linearly forwardly and downwardly.

3. In a set of upper and lower teeth including at least one denture, guiding mechanism comprising cooperating sets of track elements inclined forwardly and downwardly and trackengaging elements incorporated in the distal portions at opposite sides of the set of teeth, said track elements defining paths of mesiodistal extent at least as great as the major portion of the mesiodistal extent of a molar of such set of teeth, for engagement by said track-engaging elements during upward and retracting mandibular movement from a position of the lower teeth out of contact with the upper teeth to exert a force urging the upper and lower teeth toward registering relationship during their closing movement.

4. The guiding mechanism defined in claim 3, in which the track elements occupy the location of a second molar on each side of the set of teeth.

5. The guiding mechanism defined in claim 3, in which the track elements are recessed and the track-engaging elements are projections.

6. The guiding mechanism defined in claim 3, in which both track elements and both track-engaging elements are inset into the dentures in lieu of second molars. I

'7. The guiding mechanism defined in claim 3 in which the track elements occupy the locations of the lower teeth second molars.

8. The guiding mechanism defined in claim 7, in which the track elements are recessed and the track-engaging elements are projections and are placed at locations corresponding to the upper teeth second molars.

9. The guiding mechanism defined in claim 7, in which the track elements are ribs extending mesiodistally and the track-engaging elements are ridges having concave crests extending buccolingually.

10. In a set of upper and lower teeth including at least one denture, guiding mechanism comprising cooperating sets of track elements and track-engaging elements incorporated in the distal portion of the set of teeth, each of said track elements being recessed and defining a cavity of generally hemiellipsoidal shape, having its minor axis extending buccolingually and its major axis extending mesiodistally, the bottom of such cavity being engageable with said track-engaging elements during upward and retracting mandibular movement from a position of the lower teeth out of contact with the upper teeth to exert a force urging the upper and lower teeth toward registering relationship during their closing movement.

11. The guiding mechanism defined in claim 10, in which the track elements are inserts secured in a denture and are approximately the size of a molar, and the cavity occupies the major portion of the outer surface of the insert.

12. The guiding mechanism defined in claim 10, in which the track-engaging elements are substantially conical projections.

13. A locating element adapted to be incorporated in dentures, comprising a plate of a length approximatelyequal to the mesiodistal extent of a molar and tapered lengthwise in height.

14. A denture insert of substantially cone shape and having a base inclined at a substantial angle to the cones axis, adapted to be incorporated in a denture.

15. A locating element adapted to be incorporated in a denture, comprising an insert approximately the size of a molar and having a rimmed cavity of generally elliptical shape, shallower at one end than at the other, which cavity occupies a major portion of the inserts occlusion surface, and having a base inclined relative to the minor axis of said elliptical cavity.

DONALD V. CLEMAN.

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

UNITED STATES PATENTS Number Name Date 1,665,357 Gysi Apr. 10, 1928 1,681,436 Sears Aug. 21, 1928 1,963,207 Luthy June 19, 1934 2,075,556 Swenson Mar. 30, 1937 2,095,432 Brenner Oct. 12, 1937 2,417,965 Beresin Mar. 25, 1947 OTHER REFERENCES Page 782 of publication, The Dental Cosmos, for 1920. (Copy in Class 32-2, Div. 55.)