US3808687A - Method of making dental restorations and pontic member therefor - Google Patents

Abstract

A pontic has a rigid core and a detachable flexible plastic cap of 1 to 2.5 mm wall thickness having the external contour of a tooth. The core extends laterally slightly above the gum line to either side and has an exposed, flat, vertical face which may be secured to a matching face of an adjacent pontic or to a similar face of an insert attached to a wax or plastic coping or a wax or plastic crown which is, in turn, attached to the abutment die. In use, the abutments in a die are waxed in crowns, or copings, as per ordinary practice except for the above-mentioned inserts fixed to the abutment coping or crowns. Carding wax is applied to the tissue area of the model, and the pontics with caps in place are stuck to the wax, forming an indentation, matrix or index. Articulation is checked. The faces of the lateral extensions of the pontic cores are cemented to the adjacent abutment inserts or crown or copings extensions. Caps are then removed. The cores and abutment inserts are then invested as per the lost wax technique and metal cast into the mould cavity of the investment, also as per lost wax technique. The metal is porcelainized as in ordinary practice.

Description

United States Patent 1 Millet METHOD OF MAKING DENTAL RESTORATIONS AND PONTIC MEMBER THEREFOR [76] Inventor: William G. Millet, 2031 Lone Oak Ave., Napa, Calif. 94558 [22] Filed: Mar. 2, 1972 [21] Appl. No.: 231,138

Primary Examiner -Robert Peshock Attorney, Agent, or Firm-Julian Caplan ABSTRACT A pontic has a rigid core and a detachable flexible [45] May 7, 1974' plastic cap of 1 to 2.5 mm wall thickness having the external contour of a tooth. The core extends laterally slightly above the gum line to either side and has an exposed, flat, vertical face which may be secured to a matching face of an adjacent pontic or to a similar face of an insert attached to a wax or plastic coping or a wax or plastic crown which is,'in turn, attached to the abutment die. In use, the abutments in a die are waxed in crowns, or copings, as per ordinary practice except for the above-mentioned inserts fixed to the abutment coping or crowns. Carding wax is applied to the tissue area of the model, and the pontics with caps in place are stuck to the wax, forming an indentation,

matrix or index. Articulation is checked. The faces of the lateral extensions of the pontic cores are cemented to the adjacent abutment inserts or crown or copings extensions. Caps are then removed. The cores and abutment inserts are then invested as per the lost wax technique and metal cast into the mould cavity of the investment, also as per lost wax technique. The metal is porcelainized as in ordinary practice.

6 Claims, 17 Drawing Figures PATENTEDIAY 11914 SHEET 1 [IF 2 1 Fig.

PATENTED MAY 7 I874 SHEET 2 BF 2 Fi 15 Fig. 15

1 METHOD OF MAKING DENTAL RESTORATIONS AND PONTIC MEMBER THEREFOR This invention relates to a method of making dental restorations and also to a pontic member used in practicing the method. It is a principal object of the present invention to provide pontic members formed of a hard core of the shape which the metal part of the restoration occupies; and further, provided with a cap of a softer and more flexible plastic which acts as a guide when positioning the pontic and which represents the porcelain which is subsequently applied to the metal. The flexible cap is removable from the hard core.

In accordance with conventional practice, a considerable amount of time is required in applying wax to a pontic so that the waxed pontic has a reduced shape as compared with the completed tooth in the restoration. The present invention eliminates the need of waxing the reduced pontic and this greatly reduces the time required in making the model for the metal casting.

Another advantage of the invention is the fact that waxing of the reduced pontics is a technique which requires skill. Since the operation is eliminated in accordance with the present invention, the required skill of the technician is greatly reduced, and since the time is also reduced, the cost of, preparing the model for investment is correspondingly reduced.

Still another advantage of the invention is the fact that the removable plastic caps are of uniform thickness and represent by that thickness'the recommended correct thickness 'of the porcelain which is subsequently applied to the metal frame. Many of the failures in producing adequate restorations are attributable to the fact that the technician-applying the porcelain does not understand, the intention of the technician preparing the model for investment and the thickness of the porcelain is not applied properly. The present invention eliminates the likelihood of such confusion.

Other objects of the present invention will become more apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.

In the drawings:

FIG. 1 is a top, or occlusal, plan of a molar pontic in accordance with the present invention.

FIG. 2 is a vertical sectional view taken substantially along the line 2-2 of FIG. 1. I

FIG. 3 is a side elevational view of anincisor pontic in accordance with the present invention.

FIG. 4 is a front elevational view of the pontic of FIG. 3 viewed from the lingual side. I

FIG. 5 is a schematic elevational view from the lingual side of a die for a bridge restoration showing preliminary steps in the formation of the practice of the method of the present invention.

FIG. 6 is a view similar to FIG. 5 showing the addition of four pontics in accordance with the present invention to the abutments of FIG. 5.

FIG. 7 is a fragmentary view of the structure of FIG. 6 showing cementing of the pontics to an abutment and also to each other.

FIG. 8 shows the removal of the caps from the pontics and the attachment of sprue formers to the structure of FIG. 7.

2 FIG. 9 shows an investment made from the model of FIG. 8.

FIG. 10 shows the metal casting made'from the investment of FIG. 9 while still in the investment.

5 FIG. 11 is a rear elevational view showing a restoration formed in accordance with the present invention viewed from the lingual side.

FIG. 12 is an enlarged sectional view through one of the teeth of FIG. 11 take substantially along the line 12-12 of FIG. 11.

FIG. 13 is a view similar to FIG. 2 of a modification.

FIG. 14 is an elevational view from the lingual side showing a modification of the structure of FIG. 2.

FIG. 15 is a sectional view taken substantially along line 15'l5 of FIG. 14.

FIG. 16 is a view similar to FIG. 3 of a modification.

FIG. 17 is a view similar to FIG. 4 of the modification of FIG. 16.

Pontics in accordance with the present invention are shown in FIGS. 1-4 inclusive. The pontic 21 of FIGS. 1 and 2 is for a molar and the pontic 21a of FIGS. 3 and 4 for an incisor, but the present invention is adaptable to the various positions in the dental art. In the center of the pontic 21 or 21a is a core 22 formed of a plastic material such as an acrylic, lucite, plexiglass or some other hard material. Generally speaking, the size of core 22 is such that there is a wall thickness of 1 to 2.5 mm between the core and the outline of the tooth which the core represents. The exceptions to this wall thickness are the for'mation'of a lingual extension 23 extending immediately above the gum line and into proximal lateral extensions 24 on either side. The extensions 23, 24 represent in'practical effect the exposure of metal in the completed restoration, and the difference between the exterior of the core 22 and the ultimate wall thickness of the tooth represents the porcelain which is applied to the metal portion of the restoration after casting. Each lateral extension 24 is formed with an exposed,'vertical, flat face 26 for the purpose of attachment of thepontic to adjacent pontics or abutments as hereinafter explained. Where the core 22 joins the extensions 23, 24 there are chamfers 27 to provide a smooth transition between the metal and the porcelain which is later applied.

Fitting tightly on core 22 but removable therefrom is cap 31 which is preferably formed of a flexible plastic such as polyethylene and has four desirable characteristics. One is that it is readily removable from the core when necessary in the performance of the method; second, it does not readily adhere to cement. The third characteristic is that cap 31 acts as a guide with which to correctly position the cores on the dental arch. The fourth characteristic is that the wall thickness of cap 31 correctly represents the thickness of porcelain which is eventually applied to the metal casting. The crown 32 of the pontic 21 of FIGS. 1 and 2 has the exterior configuration of a molar (but see FIG. 13), whereas the crown 32a of pontic 21a of FIGS. 3 and 4 has the straight edge of an incisor. For other teeth, the crown 32 has a corresponding proper external shape. The labial surface33 of the cap extends down to the bottom of the pontic, whereas the lingual surface 34a extends down only to the upper edge of lingual extension 23 of core 22. The wall thickness of the cap 32, as has previously been mentioned, is quite thin being about I to 2.5

mm. The pontic 21 or 210 is manufactured in various shapes depending upon the location of the tooth. In addition to these fundamental shapes, the pontics are provided in different widths and in different lengths to accommodate the natural tooth size of the patient. The mesial, distal and bottom, or tissue bearing, surfaces can be relieved or ground away to slightly alter the shape of the pontic, as is standard procedure when assembling artificial teeth. In forming the restoration, the technician selects the appropriate width and length of pontics which conform to the shape of the natural teeth of the patient.

In the practice of the invention, the dentist prepares abutment teeth in the mouth of the patient by reduction in accordance with conventional practice. An impression of at least one jaw is made using standard impression materials. Usually both the upper and lower jaw impressions are obtained. The correct bite is established by the use of a wax sheet. Thus from the standpoint of the dentist, practice of the present invention requires no alteration of conventional practices, and the dentist himself need acquire no new techniques.

At the laboratory, the first step is to cast stone (plaster) models from the impressions provided by the dentist, and these models are articulated in a standard articulator. The particular area where the restoration is to be constructed is then sliced from one of the models to form a model or cast 36 in accordance with standard techniques.

A model or cast 36 usually has two abutment dies 37 (see FIG. which correspond to the reduced abutment teeth left in the mouth by the dentist and these abutment dies are detachable from the model. The technician then applies wax. The crown or coping 38 corresponds to the shape of the abutment tooth which has been reduced by the dentist at the time that the impression was made of the patients mouth. The crown or coping 38 will ultimately in the metal portion of the restoration comprise a socket or coping which fits over the abutment tooth in the mouth of the patient. The technician applies to the identulous side of the crown or coping 38 at the gum line an insert of the same type of plastic as is used for the core 22, and this insert 39 has an exposed, vertical flat face 41 corresponding in shape to the flat face 26 and located so that when a pontic 21 is inserted next to the abutment die 37 the faces 41 and 26 will abut and can be cemented to gether. The general shape of insert 39 is optional but can best be a circular cross-section piece which is temporarily held relative to crown or coping 38 by wax or cemented to the coping if the coping is made of plastic. The technician then adds inlay wax 42 to the crown 38, building up the thickness of wax 42 sufficiently so that the metal frame which will ultimately be represented by the wax is thick and strong enough to make a good support for the porcelain which is ultimately applied to the exterior of the metal. The configuration of the wax 42 after it is fully applied is smaller than the ultimate porcelainized crown which will fit onto the abutment tooth. In other words, the exterior of the wax 42 is only sufficient to represent the exterior of the metal portion of the abutment of the restoration. The abutment die 37 is similar to any other restoration abutment die except for the use of the insert 39 having the flat face 41. In FIG. 5 there are abutments on either side, the one on the left showing-in dotted lines the ultimate shape of the wax and the one on the right showing the wax applied.

The technician then applies carding wax 47 to the tissue area 46 of the model 36, the wax being about 1 to 2 mm thick. If the metal of the restoration is to be tissue bearing, then excess wax is trimmed away and the wax 47 lifted off the model with the core. If the metal of the restoration is to be porcelainized at the tissue area, the

wax 47 is left behind on the model. The technician then selects pontics 21 constructed in accordance with this invention of the proper general shape and size as has heretofore been explained. These pontics are then stuck in place on the carding wax47, the left-hand pontic 21 being close to the abutment die 37 with the surface 26 of the pontic and the surface 41 of the abutment in close proximity. The other pontics are similarly placed, the right-hand pontic 21 having the same relationship to the right-hand abutment die 37 as on the left-hand side. The pontics 21 stick to the wax 47 sufficiently to enable the technician to check the articulation of the die by inserting in the original model and then inserting the models of the two jaws in an articulator and making sure that the bite is proper. Any adjustments that are necessary are performed as the type of wax 47 remains pliable and also serves as a matrix or index.

After the articulation is as desired, the technician starts with the left-hand pontic 21 (or the right-hand pontic if desired), removingit from the wax 47, placing a drop of cement such as lucite and acetone cement on surface 26 and replacing the pontic 21 so that the cement 49 causes the adjoining surfaces 41 and 26 to permanently stick together. After the cement 49 has hardened, the next pontic 21 is removed from the wax 47, cement applied to its left surface 26 and the pontic is then replaced on the wax so that the surfaces 26 of the two pontics are cemented together. This operation is repeated until the right-hand pontic 21 is cemented to the insert 39 of the right-hand abutment die 37.

After all of the ponticshave been cemented in place, the cap 31 of each pontic 21 isremoved. Removal of the caps is facilitated by reason of their flexibility and the fact that they are of a materialwhich does not readily adhere to the cement 49. The completion of this operation is shown in FIG. 8 where the dotted lines represent the outlines of the original caps. Sprueforming material 51 is then waxed on to the cores 22 as well as to the wax 42 of each abutment 37.

An investment is then made from the model and this is shown in FIG. 9 wherein there is a cavity 53 formed in the investment material 52 which represents the core 22 of the pontic. There are sprues 54 for the proper casting and venting of the ultimate metal casting which correspond to the sprues 51 and are all in accordance with conventional practice. With respect to the abutment, there is a hollow 40 which represents the core or abutment die 38 and a cavity 58 which is filled with wax or plastic and represents a crown or coping which was molded over the abutment die. The section 40 remains in the investment to provide the cavity 58 which is later to be filled with metal.

A metal casting of gold or other suitable material is made from the investment mold of FIG. 9, and this is shown in FIG. 10. The metal of the sprues 57 is cut away and discarded. There is thus formed a metal frame 51 having exposed connecting portion 62 joining one tooth to the other, and this is preferably on the lingual side of the restoration. There is a plurality of metal teeth 63 each slightly reduced as compared with the eventual tooth of the restoration.

In accordance with conventional practice, porcelain 66 is applied to the metal frame 61 concealing the metal teeth 63 in all areas except the exposed connecting portion 62. The abutment crowns or copings 37b are hollow, the hollows corresponding in shape to'the abutment teeth which have been left by the dentist in the mouth of the patient. in applying the porcelain 66, the porcelain technician uses approximately the same thickness as the wall thickness of the cap 31 of the pontics 21.

FIG. 13 is a modification of the structure of FIG. 2 and many of the elements are substantially the same as in FlG. 2. Those elements appearing in the lower jaw are indicated by the same reference numerals as in FIG. 2 followed by the subscript b and those in the upperjaw are designated by the same reference numerals followed by subscript c. The pontic 21b has a core 22b similar to that of FIG. 2. However, the cap 31b is formed with a top 71 having a plurality of lateral locating grooves 72. This form of top 71 is less expensive to mold than that shown in FIGS. 1 and 2; and furthermore, the same mold may be used for uppers and lowers; and generally speaking, the same mold may be used for a plurality of different bicuspids and molars. The upper die, which matches the lower die, may be made from the impression of the actual teeth of the patient. However, in FlG. 13 the pontic 21c is provided to indicate that there is a restoration of the upper and the lower jaws. Core 220 is similar to core 22b and the top face 71c is similar to face 71 and the grooves 72c are similar to grooves 72. The grooves 72, 720 are fit together in an articulation machine to provide the proper bite for the patients mouth. This may be varied by interfitting different grooves 72 with different grooves 72c. In other words, the pontic 21c may be moved to the left or right as viewed in FIG. 13 to accomplish the proper articulation. The same left or right movement may be accomplished where the pontic 710 is replaced by a die that actually conforms to the natural tooth of the patient.

In other respects the pontics 71b and c resemble those of preceding modifications and the same reference numerals followed by subscripts b and c are used to designate corresponding parts.

lt is sometimes desirable to completely cover with porcellain the metal frame of abutment copings and adentulous pontics. This construction is also possible using the present invention.

Directing attention to FIGS. 14 and 15, extension 23 is eliminated from the core of pontic 21d. The lateral extensions 24 with their opposed flat faces 26d are used (as in FIGS. 1 and 2). Directing attention to FIGS. 16 and 17, only the interproximallateral extensions 24e having flat faces 26c are used and the lingual extension 23a of FIGS. 3 and 4 is eliminated. in other respects, the structures of FIGS. 14-15 and FlGS. 16-17 resemble those of FIGS. 1-2 and 3-4 and the same'reference numerals followed by subscripts d and e respectively are used to designate corresponding parts.

What is claimed is:

1. A pontic for dental restorations comprising a substantially rigid core shaped substantially the same as the metal portion of the restoration to be formed and having on either side an inter-proximal lateral extension terminating in a face shaped for joining to a cooperating face of an adjacent pontic and a flexible plastic cap fitting over said core and formed of a material such that said cap can be detached from said core, said cap having an external configuration substantially the same as the porcelainized portion of the restoration to be formed, said cap having lower edges fitting against the top of said lateral extensions.

2. A pontic according to claim 1 in which said core is formed with a lingual extension at the tissue line merging with the lateral extensions at either side of said core. 1

3. A method of forming a pattern for the investment mold of a dental restoration comprising forming a model from a portion of the impression made of a patients jaw wherein there is at least one abutment reduction die, affixing to said die a laterally extending insert having an insert face, applying inlay wax to said abutment die to simulate the.exterior configuration of the metal of the crown to be applied to the abutment reduction of the patients tooth, applying at least one pontic of the type defined in claim 1 to said model with one of the faces of said pontic abutting said insert face,

checking the articulation of the assembly of model, wax I and pontic, and removing the cap from said pontic.

4. A method according to claim 3 which further comprises applying second wax to said model at the situs of said pontic prior to the step of applying the pontic and in which said step of applying said pontic initially comprises temporarily sticking said pontic to said second wax and which further comprises the step of cementing said one face of said pontic to said insert face after said step of checking the articulation of the assembly.

5. A method according to claim 3 which further comprises applying sprue forming material to said assembly.

6. A method according to claim 5 which further comprises applying investment material around said assembly and hardening said investment material to form an investment mold.

Claims (6)

1. A pontic for dental restorations comprising a substantially rigid core shaped substantially the same as the metal portion of the restoration to be formed and having on either side an interproximal lateral extension terminating in a face shaped for joining to a cooperating face of an adjacent pontic and a flexible plastic cap fitting over said core and formed of a material such that said cap can be detached from said core, said cap having an external configuration substantially the same as the porcelainized portion of the restoration to be formed, said cap having lower edges fitting against the top of said lateral extensions.

2. A pontic according to claim 1 in which said core is formed with a lingual extension at the tissue line merging with the lateral extensions at either side of said core.

3. A method of forming a pattern for the investment mold of a dental restoration comprising forming a model from a portion of the impression made of a patient''s jaw wherein there is at least one abutment reduction die, affixing to said die a laterally extending insert having an insert face, applying inlay wax to said abutment die to simulate the exterior configuration of the metal of the crown to be applied to the abutment reduction of the patient''s tooth, applying at least one pontic of thE type defined in claim 1 to said model with one of the faces of said pontic abutting said insert face, checking the articulation of the assembly of model, wax and pontic, and removing the cap from said pontic.

4. A method according to claim 3 which further comprises applying second wax to said model at the situs of said pontic prior to the step of applying the pontic and in which said step of applying said pontic initially comprises temporarily sticking said pontic to said second wax and which further comprises the step of cementing said one face of said pontic to said insert face after said step of checking the articulation of the assembly.

5. A method according to claim 3 which further comprises applying sprue forming material to said assembly.

6. A method according to claim 5 which further comprises applying investment material around said assembly and hardening said investment material to form an investment mold.

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