US2129922A - Interchangeable facing - Google Patents

Description

Sept. 13, 1938. J. P. FRANCHETTI INTERCHANGEABLE FACING Filed April 22, 19 36 I N VEN TOR. 4W WW A TTORNEY Patented Sept. 13, 1938 UNITED STATES PATENT oFFicE 2 Claims.

This invention relates to interchangeable facings and backings for prosthetic dentistry.

A few years ago there was introduced to the dental profession of a plain type interchangeable porcelain facing for bridge pontics. This facing was a radical departure from the old pin type facings which were at that time almost universally used in this country. The interchangeable feature was a step forward and in time this type of facing was extensively accepted by the profession. It developed into two types, one known as the plain type interchangeable facing and the other as the root tip type interchangeable facing. It soon became evident to the profession that this type of facing was not universally adaptable I and that in certain locations of the mouth and under certain working conditions, which will later be referred to, the high percentage of breakage of the facings limited their use almost entirely to the maxillary arch. Even then the percentage of breakage was much higher than with the old pin type facing. Its redeeming feature was the ease with which it could be replaced and because of this feature its popularity continued to grow and for the same reason this type of facing is undoubtedly used many times in cases known to be unfavorable to its indication.

An interchangeable facing of the character here referred to consists of a porcelain veneer having a dovetailed groove formed in its inner face and a metal backing plate having a lug to enter the groove of the veneer; the backing plate being soldered or otherwise secured to the casting of the pontic and the veneer to the-backing plate by means of the lug which enters the groove of the veneer and by cement placed therein. As time went on certain problems and defects developed and among the more important may be mentioned:

Problems in the use of root tip interchangeable facings:

5O (1) Separation of lug from backing;

(2) Separation of backing from casting or pontic; (3) Limited adaptability; (4) Not truly interchangeable; and

55 (5) Ridge creates interference in replacing.

The object of the present invention is generally to improve and simplify the construction and operation of interchangeable facings of the character described, and more specifically stated, to provide an interchangeable facing so constructed as to practically overcome most of the defects above referred to and above all to provide an interchangeable type of facing which may be gold-tipped without in any way sacrificing the interchangeable feature.

The interchangeable facings employed and disclosed in this application are shown by way of illustration in the accompanying drawing, in which Fig. l is a perspective view of a portion of the upper jaw showing a pontic applied and in position;

Fig. 2 is a similar View showing the veneer sections of the interchangeable facings removed;

Fig. 3 is a central, vertical section of the veneer section of an interchangeable facing showing what will hereinafter be referred to as a plain interchangeable facing;

Fig. 4 is a central, vertical section of the backing plate to which the veneer is to be attached;

Fig. 5 is a front view of the backing plate shown in Fig. 4;

Fig. 6 is an enlarged cross section of a pontic showing the backing plate and veneer attached thereto;

Fig. '7 is a central, vertical section of a root tip type of veneer;

Fig. 8 is an enlarged cross section of a pontic showing the root tip type veneer and the backing plate attached to the pontic;

Fig. 9 is a perspective view of the root tip type I shown in Fig. 7;

Fig. 10 is .a perspective view of the backing plate used in conjunction with a root tip type veneer;

Fig. 11 is a perspective view of the veneer employed in conjunction with a common interchangeable facing;

Fig. 12 is a perspective view showing the labial side of the backing plate used in conjunction with the veneer shown in Fig. 11;

Fig. 13 is a perspective view showing the lingual side of the backing plate used in conjunction with the veneer shown in Fig. 11;

Fig. 14 is an end view of the backing plate shown in Figs. 12 and 13.

Referring to the drawing in detail, and particularly Figs. 3, 4, 6, 11, 12 and 13, which illustrate the plain type interchangeable facing, A indicates the porcelain or veneer portion of the facing and B the metal backing plate. Projecting from the lingual surface of the veneer is a lug 2 which is disposed on an angle of substantially 150, this being an important feature as will hereinafter appear. The lug is dove-tailed shaped in cross section and is provided with an anchor member 3 which extends into the porcelain a sufficient distance so that when the veneer is baked a rigid anchorage and attachment will be insured.

The lingual face of the occlusal edge of the veneer is beveled, as indicated at 4, and the angle is the same as that of the lug 2, to-wit, 150.

The backing plate is flat but terminates inv a beveled seat 5 having the same angle as the bevel 4 so as to form a support therefor. The rear or lingual surface of the backing plate is provided with a lug 6 which is internally grooved, as shown at I, and shaped to receive the lug 2. A slot 8 forms a continuation of the groove 1 to receive the shank 2 of the lug 2. Lug 6 and the groove formed therein is disposed on the same angle as the lug 2, thereby permitting ready separation or assembling of the veneer and backing plate as conditions may demand.

The backing plate will in actual practice he soldered or cast to C forming a bridge, plate, or whatever type of pontic it may happen to be, but a better attachment will be obtained when comparison is made with common or standard plates as the lug C will in itself be dove-tailed and shaped as shown in Fig. 14, and as such will form a mechanical retention between the backing plate B and the casting.

The root tip type of interchangeable facing is best shown in Figs. 7 to 10, inclusive. It'is almost identical to the plain type but differs at the root end as that end of the porcelain or veneer is enlarged and rounded as shown at It). The lingual surface is cut or beveled, as at H, to engage the seat I2 formed on the backing plate. The angle of the beveled face and the seat 12 being the same as that of lug 2. The seat [2 is formed by an angular extension at the upper end of the backing plate. This extension reinforces and strengthens the veneer as a whole and, furthermore, adds to the anchorage formed between the backing plate and the pontic.

While the angle of lug 2 and the other angular faces described have been specified as substantially 150", it may be varied considerably one way or the other; also it will be noted that the occlusal edge of the veneer and the backing plate is shown as substantially straight for the front teeth, but it will be understood that it will be shaped to follow the contour or slope of the cuspids, bicuspids and molars, as the case may be.

The outstanding feature of the interchangeable facing here disclosed is a facing (plain or root tip) which is gold-tipped without sacrificing the interchangeable feature. This is accomplished by using an attachment which permits a facio lingual angle of approach of veneer to backing and by beveling the biting edge of the veneer to the lingual at the same degree of angle (or greater) as the angle of attaching coupling is to the veneer. With this arrangement the portion of the casting extended over the biting edge (the gold-tip) is no longer an interference to the assembly or disassembly of the veneer and backing. Having evolved an interchangeable facing, it was decided to make the distance between the position of the lug in the veneer and the position of the linguoincisal or occlusal angle of the beveled edge constant, thereby allowing all like (same tooth) facings to be interchangeable with all likebackings as this will greatly decrease the number of facings a dentist must keep on hand to have a fair selection of facings.

By investing the anchor portion of the coupling in the veneer and forming the groove in the backing plate, I accomplish several things. First, I do away with any grooves in the veneer and thereby reduce tendency to fracture; cement shadows are eliminated and bulkiness of facings in the plain type, and a limited use of the root tip type. Also, by investing the lug in the veneer I overcome the problem of the lug separating from cast backings. The grooved coupling in the backing plate gives the backing plate a mechanical retention to the casting which overcomes the problem of the backing separating from the casting.

In the root tip type facing I leave a butt end on the root tip permitting the same facing or veneer to be used as a cone end type or as a saddle end type.

In this type of facing I eliminate any grinding of the biting edge by the dentist as the veneer is to be manufactured with a good beveled edge of constant angle and distance from the lug. This permits complete uniformity in replacing facings to previously cast pontics.

The elimination of the grooves in the root tip veneer permits almost unlimited grinding in this area which, in turn, increases the indication of this type facing to one hundred percent, the indication of the plain type interchangeable facing. This is an important feature of this type of facing.

Another advantage which I accomplish for the root tip type facing is the fact that the plain type backing can be used for this facing with the same advantages as the more expensive backing. If the pontic is to be soldered to the backing, the using of the plain backing with the root tip facing necessitates furnishing a small piece of coping gold over the uncovered portion of the root tip before waxing backing in position. If the pontic is to be cast, as is usually the case, no added precaution need be taken.

Summarizing the advantages of the plain type facing, they are:

(1) Protection to incisal (or occlusal) edge by gold-tipping.

Eliminate separation of lug and backing.

Mechanical retention of backing to casting.

No line of fracture in facing.

Like tooth facings interchangeable with all like backings.

No cement shadow through facing.

Thinner facing (and stronger).

Advantages of root-tip type facing:

The short-bite facing and backing Because the attachment of the interchangeable facing projects on the lingual of the backing, it is advisable to manufacture two kinds of facings and backings for the six anterior maxillary teeth; 1. e., the regular facing and backing having the same position of the lug to the biting edge as all other teeth, in addition to this a shortbite facing and backing is advisable for the teeth mentioned to be used in cases of extremely deep overbite of these teeth with a very narrow over- J'et. In such cases the projecting backing might cause an interference in establishing proper tooth position. The short-bite facing and backing would have the position of the lug on the facing and the corresponding female coupling on the backing in a slightly more gingival position allowing a greater depth of overbite to be cleared without interference by this porjection. The degree of angle of lug and bevel alike would remain the same as in the regular facings. Such facings and backings would be designated as short-bite facings and backings by a conspicuous marking such as the imprint of the capital letter S on facing and backing.

Having thus described my invention, what I claim and desire to secure by Letters Patent is:

1. An interchangeable artificial tooth of the root extension type comprising a veneer having an intermediate lingual face and having upper and lower beveled surfaces formed on the lingual side thereof at opposite ends of said lingual face and disposed in parallel relation to each other, said upper surface forming the occlusally disposed portion of the root extension, a lug invested in and projecting from said intermediate lingual face and spaced occlusally from the upper beveled surface and spaced gingivally from said lower beveled face, and a backing plate having complementary upper and lower seats formed thereon and oppositely disposed in parallel relation to receive thereagainst the upper and lower beveled surfaces of the veneer, and also having a groove and recess formed therein between said seats complementary to said lug and adapted to receive the lug of the veneer, said beveled surfaces and seats together with the lug and the lug receiving groove being disposed on an occluso-gingival angle from the occlusal end to the lingual side with relation to the longitudinal axis of the veneer, whereby said facing may be mounted on said backing without interference at an occluso-gingival angle and said root portion may be readily ground and adapted. 2. In an artificial tooth structure of the root extension type, a veneer or facing member having an intermediate lingual face and a root tip presenting an occlusally disposed beveled surface above said lingual face and also having at its biting edge a lower surface beveled away from said lingual face between the lingual and facial sides, the said beveled surfaces being inclined substantially in parallelism on an occluso-gingival angle from the occlusal end to the lingual side, and a lug invested in and projecting from the intermediate lingual face between said beveled surfaces and spaced from said occlusally disposed surface and spaced gingivally from said lower beveled surface, said lug having an engaging rib extending on an incline coinciding with the incline of the two beveled surfaces.

JAMES P. FRANCHE'I'II.

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