US1173045A - Dental articulator. - Google Patents

Description

D. M. SHAW.

I DENTAL ARTICULATOR. APPLICATION FILED APR. 15. 1914.

1,178,045. Patented Feb. 22,1916.

@NITED %TATE% PATENT QFFEQE,

DAVID MACKINTOSH SHAW, O1? ELTHAM, ENGLAND, ASSIGNOR TO DENTAL MANUFAC- TURING COMPANY LIMITED, OF LONDON, ENGLAND.

DENTAL EART IGULATOR.

Specification of Letters Patent.

Patented Feb. 22, 1916.

Application filediAprill5, 1914. Serial No. 831,977.

tham, in the county of Kent, England, have invented new and useful Improvements in and Relating to Dental Articulators, of which the following is a specification.

This-invention relates to improvements in dental articulators designed more particularly so that that portion of the instrument representing the human condyle is con structed to copy and carry out exactly those characteristic translation movement-s of the natural condyle in a vertical plane which. are known always to take place when the lower jaw is opened or :shut upon the upper jaw. The exact reproduction of this particular movement is of practical importance because at least some degree of opening or shutting (vertical) movement takes place in all and every normal chewing movement, whether lateral, protrusive, or combinations of these movements. It is known that during this opening or shutting movement of the lower jaw upon the upper jaw there is always simultaneously a combined movement of translation and rotation in the lower jaw and condyles in such a way that when the movement of rotation about the condyles takes place with uniform velocity, the simultaneous movement of translation of the condyles themselves takes place with a variable velocity which is slow or small in the beginning, quicker in the middle, and slower again at the end of the condyle path. It therefore follows that while this combined movement of the natural lower jaw may be at any instant resolved into a move ment purely of rotation about a single point or axis, the position of this axis (called in kinematics the instantaneous center) changes from instant to instant relatively to any point fixed on the lower or the upper jaw, so that it cannot be represented by any fixed point.

In the older type of articulating frame or articulator with a purely pivotal and non sliding joint, the artificial teeth required for either (upper or lower) jaw could be adjusted and arranged against the teeth of the opposing jaw only in that static or stationary relationship of the shut teeth which dentists term occlusion, and so the correctness of their arrangement :for efficiency in natural chewing movements could not possibly be tested with such simple hinge frames or articulators. To remedy this anatomical 'articulators were devised, the dlstinguishing feature of all of which is, that the joint which controls the movement ofone jaw relative to the other imitates the :natural jaw joint in so far as to allow, in

addition to the rotation or simple-hinge movement, a sliding movement of translation also. The :aim of inventors has been toprovide .a joint mechanism by which the general character of the separate or comb ned movements of rotation and transla tion observed in the natural living jaw is imitated as closely as possible; and also so that any particular variation of the natural joint movement observed in an individual patient can be copied and reproduced in the articulator, with the prime object of insuring that artificial teeth arranged so as to oppose one another and act in a certain preclse and efficient manner during movements on thearticulator will be related and act in exactly the same manner during chewing movements in the mouth of that particular patient.

According to my invention I provide a dental ,articulator with a condyle part so constructed that during the movement of the arm carrying the lower jaw .part with uniform angular velocity, about the condyle, the condyle part moves in an ogee or S-shaped path with a velocity which varies in the natural manner from point to point of. the movement, the motion being governed by means of a cam surface, and guideways for the condyle, so that the combined rotation and translation movements of the lower arm is not a movement of rotation about any fixed point as in other articulators, but takes place only about an instantaneous center, as in the natural jaw. It .is thereby further effected that during the vertical openingv and shutting movements the translation path of the condyle part is not the arc of a circle as insome articulators hitherto constructed, but is in a double curved, non-circular or ogee or S- shaped path as in the natural human condyle. And, just as in the natural j aw, although the translation or sliding movement may take place by itself and without other movement whenever desired, it is impossible .for :any opemng or shutting (vertlcal) movement to take place without a simultaneous movement of translation. Means are provided whereby the condyle path can be varied and adapted to agree with the ascertained path ofany patient. I may also provide a mounting platform supported in such a position on the articulating apparatus that its surface represents the horizontal level and average relative position of the occlusal plane to the joint mechanism.

My invention is illustrated by way of example in the accompanying drawings, in which- Figure 1 shows a perspective view of my apparatus with a set of anatomical teeth set up in position. Fig. 2 shows a detail view of the cam construction for producing the correct natural motion of the condyle path in opening and shutting movements. Fig. 3 shows adetail view of a cam construction representing the longitudinal jaws in position of extreme opening. Fig. 4 shows a section on the line ab of F ig. 2, looking in the direction of the arrow. Fig. 5 shows a detail underside plan View of the upper arm of the articulator and the spring adapted to retain the cam surfaces on the lower arm against the engaging pins on the upper arm. Fig. 6 shows a perspective View of the articulating apparatus with the mounting platform in position, and Fig. 7

shows a detail view of an ogee or S-cam condyle member and its pivot.

Referring now to the drawingsI pro vide on the upper arm of the articulator condyles in the form of ogee or S-cam shaped members 11, that means a cam surface composed of a concave and a convex curve. The said ogee or S-cam shaped members 11 are mounted upon pivots provided with locking pins 4 so that the posltion of said cam members can be adjusted and held rigidly in the position in which they are set to suit the condyle path of any patient. The said members 11 are respectively adapted to engage between the guiding pins 12 projecting from the disk 13 mounted on the lower arm of the articulator on pivots 14. In order that the disks 13 may be retained in position in a convenient manner, a set screw 15 is arranged to screw into each of their pivots 14, as shown in Fig. 4. The pins 7 on the upper arm engage respectively with the curved cam surfaces 2 on the lower arm. The condyle movement is effected by the said pair of pins 7, which pins are held in sliding contact with the said corresponding curved cam surface 2. The pins 17 act as limiting stops in the extreme position of the articulator.

The cam surfaces 2 on the lower arm of the articulator are normally retained in engagement with the pins 7 on the upper arm of the articulator by means of the leaf spring 8 on said upper arm (shown in detail in Fig. 5) doubled over upon itself, so that its free end 9 engages against the central portion of the cross bar 10 on the lower arm of the articulator arranged inside and between the condyle joints. The front portion of the upper jaw member has an arm 16 directed vertically downward, the extremity of which rests, when the jaw members are in the closed position, upon the cam-shaped base 17 In combination with the articulating apparatus I may provide a mounting platform 6 as shown in Fig. 6 supported in such a position on the articulating apparatus that its surface represents the horizontal level and average relative position of the occlusal plane. -The said platform is employed only for those cases wherein it is not proposed to ascertain by individual measurements the exact position of the plaster jaws and occlusal plane relative to the joint.

In use the upper bite-plate with attached plaster model is placed flat upon it, the median line coinciding with the line scored upon the platform and the incisal point coming just to its front edge. No measurements are required. The said bite-plate 'may be held in position with a little wax or clay while the upper arm is being securely plastered down upon the cast.

The claims in the present application are specific to the construction of the articulator shown and described herein and the generic claims are found in my copending application Serial No. 18,661 filed September2,1915.

WVhat I claim is 1. In a dental articulator, the combina tion of an upper jaw member, a lower jaw member, ogee-cam condyle members-0n said upper jaw member, pairs of guiding pins on said lower jaw member respectively adapted to receive said condyle members, controlling pins on said upper jaw member and cam surfaces on said lower jaw member adapted to be engaged by said controlling pins and giving said condyle members a variable velocity in their guideways during the movement of the pin members.

2. In a dental articulator, the combination of an upper jaw member, a lower jaw member, pivots in said upper jaw member, condyle members mounted on said pivots and each provided with double curved cam surface, locking pins adapted to hold the pivots of said condyle members at the angle in which they are set, pairs of guiding pins on said aw members respectively adapted to receive said condyle members, controlling pins on said upper jaw member and cam surfaces on said lower jaw member engaged by 'said controlling pins and giving said condyle members a variable velocity in their guides during the movement of the jaws.

3. In a dental articulator, the combination of an upper jaw member, a lower jaw member, condyles connecting said jaw members adapted to be moved in ogee-shaped paths during the opening or shutting movements of said jaw members, controlling pins on said upper jaw members, cam members on said lower jaw member engaged by said controlling pins and giving said condyles a variable velocity in their ogee-shaped paths, and a mounting platform supported on said lower jaw member in such a position that its surface represents the horizontal level and average relative position of the occlusal plane.

4. In a dental articulator, the combination of an upper jaw member, a lower jaw member, pivots in said upper jaw member, ogee-cam condyle members mounted on said pivots, locking pins adapted to hold the pivots of said condyle members at the angle Copies of this patent may be obtained for five cents each, by addressing the in which they are set, pairs of guiding pins on said lower jaw member respectively adapted to receive said condyle members, controlling pins on said upper jaw member, cam surfaces on said lower jaw member adapted to be engaged by said controlling pins and giving said condyle pins a variable velocity in their guides during the movement of the jaws, and a mounting platform supported on said lower jaw'member in such a position that its surface represents the horizontal level and average relative position of the occlusal plane.

In testimony whereof I have signed my name to the specification in the presence of two subscribing witnesses.

DAVID MACKINTOSH SHAW. Witnesses LEONARD E. HAYNES, CHARLES F OYER.

Commissioner of Patents,

Washington. D. C.

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