US2659145A - Preformed dental inlay - Google Patents

Description

Nov. 17, 1953 M. B. GlLLMAN PREFORMED DENTAL INLAY Filed Feb. 8, 1952 INVENTOR. N BARNETT GILL MAN ATTORNEYS.

Patented Nov. 17, 1953 snails PREFORMED DEN'l'AL INLAY Max Barnett Gillman, New Hyde Park, N. Y., assignor of one-half to Harry Gillman, Flushing, N. Y.

Application February 8, 1952, Serial No. 270,573

4 Claims. 1

My invention relates to dental inlays and in particular to a stamped-out ready-made inlay of adjustable length, and to a new and improved method of preparing a cavity for receiving this inlay.

The conventional method of preparing inlays has been practiced for many years without change. According to this conventional methed, the dentist utilizes a solid inlay which is a cast form of gold made to conform exactly in size and shape to a cavity prepared along predetermined lines. After the cavity has been prepared, the dentist fills it with a wax to make an accurate impression, withdraws the wax and invests it in a heat-withstanding refractory, allows this to set for approximately two hows, then boils out the wax and pours molten gold into the mold left in the refractory. The result, if successful, is an exact gold replica of the wax impression which should fit snugly into the cavity. The cast gold form is then polished and cemented within the cavity to complete the inlay.

Since the wax impression is soft, it frequently breaks or becomes misshapen, so that it becomes necessary for the dentist to take another impression. In addition, the casting process itself often produces miscasts, and/or porosity since the inlay must make a perfect it in the cavity, it then becomes necessary for the dentist to repeat the entire process. casting is made, the steps of the impression-taking, investing, boiling out, casting, polishing, and fitting, are time-consuming and expensive, invariabl requiring several sittings by the patient.

The aforementioned difiiculty in the preparation of inlays is multiplied manyfold when a permanent bridge is made, supported at both ends by inlays. Aside from the problem of preparing and fitting two inlays simultaneously, the dentist is confront with the even greater difiiculty of alining the cavities in the abutting natural teeth so that the inlays of the completed bridge will fit properly. This procedure of paralleling will be discussed presently in greater Even when a perfect istics. top wall H and side Wall l2, a metal pin or post It is an object of the invention to provide an inlay of the character described which is constructed to fit within a cavity without touching the edges thereof, so that the dentist is not required to prepare an inlay to fit snugly within the cavity.

Another object of the invention is to provide an inlay of the character described which is of such a form as to permit the preparation of the cavity along sound structural lines, to prevent the loss of the inlay from the cavity.

Still another object of the invention is the provision of an inlay of the character described which is ideally suited for use in conjunction with fixed or permanent bridges.

Other objects and advantages of the invention will be apparent in the course of the following specification when taken in connection with the accompanying drawing, in which:

Fig. l. is a front elevational view of an inlay constructed in accordance with the invention;

Fig. 2 is a central vertical section taken therethrough;

Fig. 3 is a rear elevation of the inlay of Figs. 3. and 2;

Fig. 4. is a side elevation showing a modified form of inlay;

Fig. 5 is a side elevational view of a tooth shown partially in section to reveal a prepared cavity in which the inlay of Figs. 1-3 is set;

Fig. 6 is a rear elevational view of the tooth and inlay of Fig. 5;

Fig. 7 is a top plan View of the tooth and inlay of Pig. 5; s

Fig. 8 is an elevational view of a pair of natural teeth shown partially in section; the teeth having a fixed bridge set therebetween by means of a pair of inlays; and

Fig. 9 is an elevation. of a tooth shown partially in section to reveal a modified form of inlay set within a central occlusal cavity.

Referring in detail to Figs. 1-3, the inlay shown therein has an angular body portion Eli comprising a top wall I I and a side wall l2 integral therewith and substantially perpendicular thereto. The body portion it may be made of gold or any other material having suitable dental character- Within the angular recess between the 13 is mounted, the pin I3 being bent intermediate its ends to provide an upper log it and a lower leg I5 arranged at an angle to each other; The end of the upper leg 14 is bonded to the bottom surface of the top wall I I, while the pin I3 is also bonded to the inner surface of the .side Wall I2 at the juncture between the upper and lower legs [4 and I5. A recess IT is thus formed between the inclined upper leg 14 and the inner surfaces of the top and side walls I I and I2.

In the bonded position of the pin [3, its lower leg l5 depends well below the bottom of the body portion l6 and is substantially axially coincident with the longitudinal axis of the inlay. The pin i3 may be made of any suitable rigid metal, and may be made of the same metal as the inlay. The pin !3 may be integral with the body portion Iii, if desired.

The outer surface of the top wall H of body portion It is beveled to provide an occlusal ridge I 6 which conforms to the plane of the natural anatomical occlusal carving of the tooth in which the inlay is to be set.

The drawings are substantially to scale, and reference is made thereto for further disclosure.

The inlays may be mass produced in a factory by stamping them from a metal plate, a process which is appreciably more economical than individual casting. The inlays may be supplied to the dentist in a variety of sizes, but since the inlays are not intended to fit snugly within the cavity, as will be presently explained, and since the maximum size of the cavity is limited by the size of the human tooth, this variety will not be great. The stock may also include several varieties of inlays in which the shape of the occlusal ridge l6 varies to conform to the anatomical structure of different type teeth. Again, this variety will be small, since the anatomical occlusal carving of different teeth do not difier widely, especially at the marginal areas of the teeth in which the inlays are placed. In practice the fiatter the ridges and inclined planes, the more comfortable for the patient.

In the use of the inlay of Figs. 1-3, the dentist must first drill out the decayed area to form a prepared cavity. Figs. 5-? show a prepared cavity of the type for which the inlay of Figs. 1-3 is intended. This cavity C extends continuously from the occlusal or top surface of the tooth T to one of the vertical surfaces thereof, for example to the rear or distal surface.

Once the cavity has been prepared, the dentist selects from his stock a ready-made inlay to suit the particular size and shape of cavity and tooth and fits it tentatively within the cavity to determine its length. The length of the inlay must be such that with the free bottom end of the pin l3 resting upon the base of gingival seat G of the cavity C, the top surface of top wall H is flush with the top surface of the tooth T, and the marginal ridge !6 is in alinement with the natural occlusal ridges and inclined planes of the tooth T. To adjust the length of the pin it, the free bottom end of the lower leg 15 is cut off, filed, or otherwise trimmed until lower leg I is of the proper length.

As shown in Fig. 5, the outer surface of the side wall 12 is shaped and positioned to be alined with and act as a continuation of the distal surface of the tooth when the inlay is properly set in place within the cavity interproximately. The bottom and side edges of the side wall l2 are spaced from the walls of the cavity in this position. With the length of the inlay properly adjusted, the dentist then places a matrix around the tooth T, prepares a rather thin mixture of methyl methacrylate monomer and polymer in the usual manner, fills the cavity 0 with the resin mixture R and places the adjusted inlay into the cavity with the end of pin 13 resting upon the gingival seat G and the outer face of side wall I! in flush alinement with the distal surface of the tooth T. The inlay rests against the matrix for distal support while the resin R is still soft. A sheet of cellophane is then placed over the tooth and the patient is then instructed to clench his teeth for correct occlusal relationship. After a period of five or six minutes, the resin has hardened, and the matrix is removed, the excess resin trimmed, and the patient dismissed. This entire process may be performed in one sitting and within a very short time after the cavity has been prepared.

It will be noted that the only contact between the inlay and the cavity C is at the bottom of pin l3; the top wall II and side wall i2 of body portion It being spaced along their entire edge surfaces from the adjacent sides of the cavity C. The amount of spacing is not critical and may be as much as one millimeter at any point. Hence, within practical limits, the size and shape of the cavity may vary without affecting the efiiciency of the inlay.

The spaces between the inlay and the cavity walls are filled with the hardened acrylic resin R. As shown in Fig. the greater portion of the cavity interior is filled with this resin R. While this resinous mixture is impervious to mouth fluids, it cannot take occlusal stress and strain occasioned by biting, hence the preformed inlay is designed to replace the missing marginal ridge and inclined planes lost through decay or cavity preparation, upon which ridges substantially the entire biting stress is distributed. The patients biting stress is thus taken by the marginal ridge it of the inlay and is distributed through the body portion 58 and the pin i3 directly to the tooth body at the gingival seal G of cavity C. When the patient chews, only the marginal ridges of the inlay come into direct contact with the opposing tooth, thereby giving maximum biting function and relieving the resin cementing media of all direct biting function.

Since the inlay is spaced from the sides of the cavity and a greater portion of the cavity i filled with resin, an improved technique of cavity preparation may be employed. It is well-known that most conventionally-prepared inlays fail in the gingival seat. Upon X-ray examination, a discernible space or leaky area is often discovered. This is the result of the common use of a cementing medium, namely oxyphosphate of zinc, which is not impervious to mouth fluids and is consequently washed out. Since the conventional inlay is custom-made to fit the cavity snugly and exactly, the cavity is lined with a thin layer of this cement which is all that holds the inlay in place.

Since in the inlay of the present invention, the inlay itself, and not the cementing media, takes all of the stress, an impervious media such as the methacrylates, or polyesters may be eifectively employed. These resins, being impervious to mouth fluids, prevent oozing, infiltration, and leakage between the inlay and cavity walls, especially in the hitherto vulnerable area of the gingival seat of the cavity.

In addition, the construction of the inlay enables the cavity to be prepared in the cross-sectional shape of a truncated triangle, or, in other words, wider at the base than at the top, without the necessity of bevelled margins so essential in the construction of conventional types of gold inlay preparations. This cavity shape is clearly shown in Figs. 6 and 9, and is advantageous in supplying an undercut which, when filled with the hardened resin R, prevents the inlay and resin from being dislodged or pulled out of the cavity.

It ma be also noted that the hardened resin R fills the space I! between the pin leg l4 and the inlay body portion ID. The inlay is thus firml anchored to the resinous cementing medium, a result hitherto unobtainable in conventional inlay preparations.

Fig. 4 shows a similar inlay of modified construction. This inlay has a body portion comprising a top wall 2| and side wall 22 similar .to those of the inlay of Figs. 1-3. Insteadof the fixed rigid pin i3, however, this inlay has a screw 23 threaded in a laterally-extending .lug Zlwhich is integral with the inner surface of side wall 22. The screw 23 has a fiat head which faces downwardly. The screw 23 may be adjustedto vary the length of the inlay more conveniently, the screw head 25 resting upon the gingivalseat of the cavity when the inlay is .set'in position. The resin hardening between the top wall 2 and the lug 2d, and between the lug 24and the screw head 25 anchors the inlay firmly in position.

Fig. 9 shows another modified inlay especially constructed for use with a central occlusal cavity Cc which is open only at its top, and not atits sides. This inlay has a body portion consisting only of a top wall 36, but with no side wall. A pin 3! depends perpendicularly from the bottom surface of the body portion 39. The length of this pin 3| may be adjusted in the manner previously described. The pin has one or-more projections or protuberances 32 intermediate its ends, around which the resin R hardens to anchor the inlay in the cavity Ca.

Aside from its economy, structural strength, and ease in fitting, the inlay of the invention is especially advantageous in the preparation of a fixed inlay bridge, saving considerable time and effort by eliminating paralleling on the part of both dentist and laboratory technician, and providing a more effective bridge. V t p In the preparation of a fixed bridge to fit in the gap between two natural teeth (called abutments), if inlays are used it becomes necessary for the dentist to prepare a cavity in the facing surfaces of the abutmentsa An inlay i then cast for each cavity, and these inlays are secured to an artificial tooth or teethjso that the tooth or teeth of the bridge fill the gap when the inlays are cemented in the cavities. Special care must be taken to aline the prepared cavities or paralleling the inlays in the abutment so that the completed bridge will fit properly in place, this alining procedure being commonly called paralleling the abutments. The procedure is a difiicult one, the alinement being performed solely by eye, with the result that human error frequently causes the cavities and/or inlays to be out of alinement.

After the abutment teeth have been prepared, the dentist takes impressions of the cavities, casts the inlays, fits them into the respective cavities, takes an impression of the gap with the inlays in position, and sends this to the laboratory techniclan, who prepares a bridge in which the inlays exactly fitting the cavities are secured to the sides of the denture teeth.

When the dentist receives the completed con ventional bridge, he must then fit the bridge inlays within the prepared cavities. The bridge must be constructed to make a very tight fit in the gap, since any movement would tend to crack the inlay cement and thereby loosen the bridge even further. The bridge inlays must therefore be forced within the prepared cavities of the abutments under a rather extreme pressure. If the cavities or inlays are not exactly alined, or either of the inlays is miscast, this forcing pressure must be accentuated, causing the patient to experience undue pain. Still more serious, in forcing the bridge in position, one or both of the abutting teeth is caused to move slightly in its socket. This movement tends to tear the tissue which lines the socket and may result in the formation of pyorrhea pockets.

The aforementioned diificulties are entirely eliminated by the use of the pro-formed inlay of the present invention. Fig. 8 discloses a bridge 41} comprising a single artificial tooth ii carrying an inlay it, of the type shown in Figs. 1-3, on each of its opposed sides. The inlays It! are bonded to the tooth ii in the usual manner. The

bridge is set between two natural teeth, such as 1 a molar M and a premolar or bicuspid B, the reference letter U indicating the gum oi the mouth. Each of the inlays iii is secured by resin R within cavities A and V prepared in the manner previously described.

The dentist prepares the cavities A and 'v without regard to exact alinement unlilce the preparation of a conventional inlay bridge, since errors in alinement will not cause any inconvenience. After sending the impression of the patients mouth portion to the laboratory technician, the dentist receives a bridge of the type of bridge fill which carries the ore-formed inlays H3. These inlays It are fitted into the respective cavities A and V in the manner previously described without regard to paralleling and are cemented by the resin Pt. Since the inlays it do not fit snugly within the cavities, the bridge 63 does not have to be forced into the and the fitting is neither painful nor harmful. The truncated shape or the cavities A and V is snfficient to provide a solid support for the inlays iii, preventing movement of the bridge.

While preferred embodiments of the invention have been shown and des "ibed herein, it is obvious that numerous omissions, changes, and additions may be made in the invention without departing from the spirit and scope thereof.

I claim:

1. For use in conjunction with a filler of resinous cement to fill a prepared tooth cavity having a top opening in the occlusal sur ace of the tooth and a contiguous opening in the side surface of the teeth, a preformed metal dental inlay comprising a body portion which has a top wall and a side wall angularly arranged in relation to each other with an open recess therebetween, said top wall having a top occlusal surface which is transverse to the longitudinal axis of said inlay, and a support member secured to said body member and depending centrally therefrom and extending an appreciable distance below the bottom end of said side wall in substantial axial alinernent with said inlay, said support member being also connected to said side wall and having a transverse cross-sectional area which is appreciably less than the transverse area of said top wall to provide a relatively large recess between the lower portion of said inlay and the walls of said cavity for reception of said resinous cement when said inlay is fitted within said cavity, said support member being adjustable to a length in which said inlay may be fitted within said cavity in an inserted position in which the bottom of said support member rests upon the bottom wall of said cavity, the top occlusal sur face of the inlay top wall partially covers the top opening of said cavity and is alined with the occlusal surface of the tooth, and the outer surface of the inlay side wall partially covers the side opening of the cavity and is alined with the side surface of said tooth, the top and side walls of said inlay being sized to be spaced around their entire peripheries from the respective top and side cavity openings in the inserted position of said inlay.

2. For use in conjunction with a filler of resinous cement to fill a prepared tooth cavity having a top opening in the occlusal surface of the tooth and a contiguous opening in a side surface of said tooth, a preformed metal dental inlay comprising a body portion having a top wall and a side wall, said side wall depending from one end of said top wall, and a support post which has an upper portion and a lower portion which is integral with said upper portion, said upper portion being inclined to both of said walls and being connected at its respective end portions to the respective walls, said lower portion extending in a direction which is substantially normal to said top wall and extending substantially below said side wall, whereby said inlay is adapted to be placed in said cavity with the bottom of said post resting on the bottom of said cavity and with said side wall substantially iiush with said side surface and spaced from the edges of said opening in said side surface and with said top wall substantially flush with said occlusal surface and spaced from the edges of said opening in said occlusal surface.

3. For use in conjunction with a filler of resinous cement to fill a prepared tooth cavity having a top opening in the occlusal surface of the tooth and a contiguous opening in the side surface of the tooth, a pre-formed metal dental inlay comprising a body portion which has a top wall and a side wall substantially perpendicular to each other, said top wall having a top occlusal surface shaped to simulate the natural marginal occlusal ridges of the tooth area in which said cavity is located and to act as a continuation of the occlusal ridge structure of the remainder of the tooth, said top occlusal surface being transverse to the longitudinal axis of said inlay, and a support post having a lower portion coincident with the longitudinal axis of the inlay and an integral upper portion inclined to said longitudi- 8V nal axis, said upper support post portion being secured at its respective ends to the inner surfaces of said body portion top wall and side wall adjacent the free ends thereof, said upper support post position and the inner surface of said body member defining a transverse opening for receiving said resinous cement filler whereby to anchor said inlay in said filler, the lower portion of said support post depending an appreciable distance below the bottom edge of said side wall and being adjustable to a length in which said. inlay may be fitted within said cavity in an inserted position in which the bottom of said lower support post portion rests on the seat of said cavity and the top surface of said cavity member is fiush with the occlusal surface of said tooth.

4. A dental bridge comprising at least one artificial tooth rigidly mounted between a pair of metal dental inlays, each said inlay comprising a body portion having a top wall, a side wall depending from one end of said top wall and substantially normal thereto, and a support post which has an upper portion and a lower portion which is integral with said upper portion, said upper portion being inclined to both of said walls and being connected at its respective end portions to the respective walls, said lower portion extending in a direction which is substantially normal to said top wall and extending substantially below said side wall, the side wall of each inlay being secured at its outer surface to said artificial tooth.

M. BARNETT GILLMAN.

to the Tooth: Cured at Mouth Temperature, Dental Digest, p. 14, January 1943.

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