GB2151141A

GB2151141A - Dental devices for attachment to teeth

Info

Publication number: GB2151141A
Application number: GB08333331A
Authority: GB
Inventors: Nicolas Matthew Jedynakiewicz
Original assignee: University of Liverpool
Current assignee: University of Liverpool
Priority date: 1983-12-14
Filing date: 1983-12-14
Publication date: 1985-07-17
Also published as: GB8333331D0; JPS60198148A; DE3445530A1

Abstract

A dental device incorporating means for attaching the device to at least one tooth, said device comprising a body member having a passageway (10) for bonding material therein, the passageway having an inlet and at least one outlet for the bonding material, the or each outlet being adapted to abut against a respective tooth (13, 14), whereby the device may be bonded to the tooth. Also disclosed is a dental device incorporating means for attaching the device to at least one tooth, which comprises a hollow pontic having an inlet and at least one outlet for bonding material, said hollow pontic being placed in a gap between teeth with the or each outlet abutting against a respective tooth, bonding material 14 being introduced into the hollow pontic through the inlet to completely fill the hollow interior of the pontic and, by means of the or each outlet, contact the adjacent tooth or teeth, the material constituting the hollow pontic being removed after the bonding material has set, to leave said set bonding material in the form of a solid moulded pontic bonded to one or both of adjacent teeth. <IMAGE>

Description

SPECIFICATION Dental Devices for Attachment to Teeth This invention relates to dental devices for attachment to teeth and is particularly concerned with dental devices for prosthetic or orthodontic purposes.

The present method for forming a pontic for a temporary or permanent fixed-bridge prosthesis is to prepare a denture tooth by grinding the gingival surface to a suitable form and then introducing a retentive feature into the lingual surface. The retentive feature may consist of a centrally placed horizontal groove with an undercut and a midline dovetail.

The pontic so-formed is held against two abutment teeth, the enamel surfaces of which have been etched and bonding composite applied to the groove using a flat plastic instrument. The composite at the ends of the groove bonds to the abutment teeth. The excess material is then removed after polymerisation using a rotary instrument. This is a somewhat laborious and uncontrolled process which has the following disadvantages: a) The composite bonding material is difficult to apply.

b) The composite bonding material is smeared horizontally across the etched enamel surfaces of the abutment teeth with the possibility of damaging the fine prismatic structure of the enamel.

c) It is very difficult to establish pressure of the composite against the etched enamel surface. A degree of pressure enhances bonding.

d) A large amount of composite is needed. This material is extremely expensive. Wastage with this technique is relatively high.

e) The application of the material with a spatula is quite likely to incorporate a significant number of air blows and reduce the overall efficiency of the bonding and the strength of the composite.

f) Excess composite is difficult to remove and is usually plentiful.

-An object of the invention is to facilitate the attachment of dental devices to teeth.

According to the present invention, there is provided a dental device incorporating means for attaching the device to at least one tooth, said device comprising a body member having a passageway for bonding material therein, the passageway having an inlet and at least one outlet for the bonding material, the or each outlet being adapted to abut against a respective tooth, whereby the device may be bonded to the tooth.

Atypical application of the device is the attachment in part or in whole of a fixed bridge prosthesis. Other applications including attachment of devices for orthodontic purposes are envisaged.

In one embodiment of the invention, the passageway is integrally formed within a pontic for the replacement of missing teeth. The passageway is an internal passageway and is such that once bonding material enters the passageway through the inlet, it can only leave the passageway at the outlet(s). Thus, the passageway is not a groove in the pontic as in the known contruction described above and the invention thus avoids the disadvantages resulting from the use of a groove.

To facilitate the supply of bonding material to the passageway, the inlet may be provided with an injection tube for bonding material. This tube may be removed after it has served its purpose. To facilitate the bonding of the pontic to a tooth or teeth by bonding material from the passageway, the or each outlet may be provided with an abutment member for abutting against a respective tooth. The abutment member may be shaped to provide adequate contact between the pontic and the tooth.

The pontic may be modified to allow alteration of its colour or shade. Thus the pontic may be provided with a hollow interior portion which is not in communication with the passageway but which is provided with a separate inlet, if desired with attached temporary injection tube, for the supply of colouring material (which may be composite) to the hollow interior. The hollow interior portion may be provided with air vents to facilitate filling it with the colouring material. Alternatively, if the bonding material also serves as the colouring material, a completely hollow pontic with inlet and outlet(s) but no separate passageway may serve as both passageway for bonding material and means for holding colouring material.

The pontic may be formed from any suitable material, for example ceramics or plastics, such as polycarbonates, or a metal, such as gold, or metal alloys. If desired or appropriate, the pontic may be provided with a surface coating or layer, such as porcelain in the case of a gold pontic. On economic grounds, plastics may be preferred as the material for the pontic.

Where a gap in the teeth corresponds to more than one missing tooth, a dental prosthesis for the gap may comprise a corresponding assembly of more than one pontic as an integral unit for fitting and securing in the gap, the assembly including, in at least one terminally positioned pontic, a passageway with an inlet and at least one outlet for bonding material. Where appropriate, the assembly may also include a terminal crown or cap for securing the assembly to a tooth at one end of the gap and the terminally positioned pontic may be bonded to a tooth at the other end of the gap. Where the assembly includes a crown, there may be only one pontic in the assembly, but more than one may be present if desired or appropriate.

In all the various embodiments described above, the passageway of the dental device is used to guide an adhesive substance (the bonding material) onto an area of prepared tooth surface. The passageway restricts the adhesive substance from flowing into unwanted areas. When the adhesive bond has been achieved, the device becomes fixed to the tooth and is thereby retained in place.

The adhesive bond may be one of several types: a) micromechanical adhesion type.

The enamel surface of the tooth is etched with a dilute acid leaving pits up to 120 pm deep.

Polymeric resins may enter these pits and, when set, form a strong mechanical bond. Materials suitable for use in forming the micromechanical adhesion include silane-based cyanoacrylated-based, urethane-based and polyacid-based materials.

However, the preferred material for forming the micromechanical adhesion is bis-phenol A glycidyl dimethacrylate.

b) specific adhesion type.

An adhesive substance is employed with exhibits chemical adhesion to enamel or dentine. This includes silane-based, cyanoacrylate-based, urethane-based and polyacid-based materials.

c) a combination of a) and b).

All of the above adhesive systems are currently in use in dental practice and are commercially available. The bonding material will normally be a composite material.

In a modification of the dental device of the invention, there is provided a completely hollow ponticwhich acts as a mould and has an inlet and outlet(s) but no separate passageway such that, in use, the pontic, e.g. formed from cellulose acetate, is placed in the gap between the teeth with the or each outlet abutting against a respective tooth, the bonding material is introduced into the hollow pontic through the inlet to completely fill the hollow interior of the pontic and, by means of the outlet(s), contact the adjacent tooth or teeth, the bonding material is allowed to set, and the pontic used as the mould is then removed leaving the set bonding material in the form of a solid moulded pontic bonded to one or both of the adjacent teeth. The pontic used as the mould may, for example be removed by splitting it, e.g. with a scalpei.This procedure may also be used to form a dental prosthesis comprising an assembly of more than one pontic. This modification is in contrast to the above-described embodiments wherein the hollow pontic is retained in place after the bonding material has been introduced into the hollow pontic and allowed to set.

The invention includes a former for forming the passageway with inlet and outlet(s) in the pontic or other dental device by fabricating the pontic or other device around the former. The former may include means for forming the injection tube and the abutment members at the outlets. The means for forming the abutment members may be adjustable.

The former may be solid or hollow. If solid, it needs to be removed from the fabricated pontic to provide the passageway. Suitable materials for a solid former are carbon and steel. A hollow former may provide the passageway and can therefore be left in the fabricated pontic.

The invention further includes a method of forming a dental device which comprises fabricating the device around the former described above and if necessary thereafter removing the former.

This invention is applicable in the following clinical situations: a) where immediate replacement of an anterior tooth is required when the tooth has been accidentally knocked out or has required extraction.

b) when the teeth which are adjacent to the missing tooth are in excellent condition and the patient is reticient to have these teeth cut for a conventional bridge.

c) when a fixed temporary replacement is required for a lost anterior tooth prior to the eventual provision of a conventional fixed-bridge prosthesis.

d) when financial limitations preclude the possibility of any custom-made porcelain or castmetal prosthesis.

The system allows the clinician to bond a replacement for a missing tooth directly to the proximal surfaces of the two teeth adjoining the gap (the abutment teeth). The bond used may be a micro-mechanical bond between a resin of a composite restorative material and fine channels which are etched into the enamel surface of each tooth with a suitable acid.

In the accompanying drawings, Fig. 1 illustrates a known dental device and Figs. 2 to 9 iliustrate the invention by way of example. More particularly: Fig. 1 is a perspective view of a conventional acrylic denture tooth prepared for incorporation into a direct-bonded fixed bridge prosthesis; Fig. 2 is a perspective view of a pontic in accordance with the invention for a direct-bonded fixedbridge prosthesis; Fig. 3 is a perspective view of a modified form of the pontic shown in Fig. 2 which allows the colour or shade of the pontic to be modified; Fig. 4 is an elevation in section of the pontic shown in Fig. 3; Fig. 5 is a perspective view of another modified form of the pontic shown in Fig. 2 illustrating the application of the invention to a pontic of composite structure;; Fig. 6 is a perspective view of the pontic shown in Fig. 5 after removal of the injection tube, Fig. 7 is a perspective view of a dental prosthesis which includes in combination a crown and a pontic in accordance with the invention; Fig. 8 is a perspective view of a former for forming the passageway and associated features in a pontic in accordance with the invention; and Fig. 9 is a sectional view illustrating a method of forming a pontic in accordance with the invention.

The conventional denture tooth shown in Fig. 1 has been cut with a bar to provide in its lingual surface a centrally placed horizontal groove 10 with an undercut 11 and a midline dovetail 12. When the denture tooth is fitted in a gap between existing teeth 13,14, bonding material is pressed into the groove 10 with a spatula until it emerges at the ends of the groove to bond the denture tooth to the teeth 13,14. Damage to the surface of the teeth 13,14 may result from the operation of filling the groove and excess bonding material needs to be removed from the surfaces of all three teeth when bonding is complete.

By contrast, in the pontic in accordance with the invention as shown in Fig. 2, there is an internal passageway 20 terminating at the edges of the pontic which are to be secured to adjacent teeth in outlets including abutment members or extensions 21. The pontic carries an injection tube 22 communicating via an inlet in the lingual face of the pontic with the middle of the passageway for supplying bonding material to the outlets via the passageway, which diverges between its middle and the outlets. The extensions 21 are adjusted during the trial fitting of the pontic so that they fit quite tightly against the adjacent teeth. This helps to develop the pressure required to ensure an adequate bond between the bonding material and the surfaces of the adjacent teeth, which may have been previously etched to facilitate bonding.The tight fit also minimises the production of excess bonding material because the bonding material supplied through the injection tube can only emerge from the passageway at the extensions.

The pontic of Fig. 2 is a preformed tooth designed specifically for use as a pontic for direct enamelbonded fixed bridge prostheses. The pontic is fabricated from a suitable material, preferably a polycarbonate, which would give a reasonable degree of colour and surface stability in the oral environment. A polycarbonate would also lend itself to injection moulding techniques which are suitable for mass production of the pontic. Alternatively the pontic may be made from acrylic plastics or composite materials.

In Figs. 3 and 4, the pontic shown has a hollow interior 30 through which passes a separate walled passageway 31, with outlet extensions 32. The pontic is provided with two injection tubes 33 and 34. Tube 33, for the supply of colouring or shading material to the pontic, communicates with the interior 30, which is provided with air vents 35 to allow air to escape when filling the interior with colouring material via tube 33. Tube 34 communicates with the middle of the passageway, whereby bonding material may be supplied to the outlet extensions 32 via the tube 34 and passageway 31. Only one injection tube is needed if a composite bonding and colouring material is used.The pontic then becomes similar to that of Fig. 2 except that the injection tube and outlet extensions communicate directly with the completely hollow interior of the pontic and the composite bonding and colouring material is supplied via the single injection tube to both the pontic interior and the outlet extensions.

In Figs. and 6, the pontic shown has a cast metal, e.g. gold, core 50 and a porcelain surface layer 51.

The core is chamfered at 52 to facilitate bonding the procelain to the metal, which consequently remains exposed on the lingual surface at 53. The pontic is otherwise similar to that shown in Fig. 2, having an injection tube 54 (Fig. 5) and an outlet extension 55 linked by a passageway (not shown) for bonding material. In Fig. 6, the pontic is shown with the injection tube and accompanying sprue of bonding material severed off and seal polished to leave an inlet 56 to the passageway filled with bonding material in the fitted pontic.

Fig. 7 shows a fixed-bridge prosthesis assembly consisting of pontics 70,71 and a full veneer crown 72. The terminal pontic 70 corresponds to that shown in Fig. and has an injection tube 73 communicating via an interior passageway with an outlet extension 74. Both pontics are of porcelain bonded to metal, e.g. gold, and the crown 75 is of metal, e.g. gold, or porcelain bonded to a metal, e.g.

gold, the metal securing the two pontics and the crown together. When the assembly is fitted, the crown forms a major retainer and the terminal pontic a minor retainer through bonding at the outlet extension 74.

The former shown in Fig. 8 consists of a passageway-forming portion 80, which as shown is of triangular section for anti-rotational purposes, an injection-tube-forming portion 81 and two abutment-member-forming (outlet-extensionforming) portions 82, which are slidably adjustable on the portion 80. The portions 82 are undercut at 83 to create retention in investment material during use of the former. The former is made of a material which does not fuse during casting of the pontic around the former, e.g. carbon or steel.

The use of the former is illustrated in Fig. 9. A wax mould 90 of the pontic is formed around the former 8082. Then a casting of investment material is formed around the wax mould. The wax is then melted out and the pontic cast in the resulting mould 92 from, for example, gold. The investment material and former are then removed to produce the metal casting. If the former is of graphite, it can be chipped out. If the former is of steel, then during casting of the pontic an oxide layer will form on the steel which will aid in the later removal of the steel former by removing first the portions 82 (which are slidably mounted), then the portion 81 and finally the portion 80. The metal casting may then have a procelain layer applied to give the finished pontic.

Some advantages of a pontic made in accordance with the invention ars as follows: a) The invention allows pressure injection of the composite bonding material directly to the area of bonding on the abutment teeth.

b) Composite bonding material is forced against etched enamel from a direct perpendicular to the etched surface, maximising penetration of the composite material into the tooth and minimising damage to the finely-etched enamel prisms.

c) Excess bonding composite material only forms when the composite material has already covered the bonding area and filled the pontic. In the older technique, the composite excess formed first and then the bonding area was covered and the pontic filled.

d) Because the pontic is sealed quite tightly at the bonding areas from the outset (because of the outlet extensions), the amount of excess is reduced to a minimum and is easily dealt with, for example using a fine high-speed tungsten-carbide finishing bur.

e) Minimising excess bonding material formation means minimising material needed which means minimising expense.

f) The use of a polycarbonate for the pontic would give a reasonably stable surface and colour and has good aesthetics. It is also easily fabricated.

Claims

1. A dental device incorporating means for attaching the device to at least one tooth, said device comprising a body member having a passageway for bonding material therein, the passageway having an inlet and at least one outlet for the bonding material, the or each outlet being adapted to abut against a respective tooth, whereby the device may be bonded to the tooth.

2. A device as claimed in claim 1 in which the passageway is integrally formed within a pontic for the replacement of missing teeth, the passageway being an internal passageway and being such that once bonding material enters the passageway through the inlet, it can only leave the passageway at the or each outlet.

3. A device as claimed in claim 1 or 2 in which the inlet is provided with a removable injection tube for bonding material.

4. A device as claimed in any of claims 1 to 3 in which the or each outlet is provided with an abutment member for abutting against a respective tooth.

5. A device as claimed in claim 4 in which the abutment member is shaped to provide adequate contact between a pontic and a tooth.

6. A device as claimed in any of claims 2 to 5 in which the pontic is provided with a hollow interior portion which is not in communication with the passageway but which is provided with a separate inlet for the supply of colouring or shading material to the hollow interior.

7. A device as claimed in claim 6 in which the separate inlet is provided with a removable injection tube.

8. A device as claimed in claim 6 or7 in which the colouring or shading material is composite material.

9. A device as claimed in any of claims 2 to 5 in which the pontic is provided with a hollow interior portion, the bonding material also serves as a colouring or shading material the pontic having said inlet and the or each outlet, the hollow interior serving as both passageway for bonding material and means for holding colouring material.

10. A device as claimed in any of claims 6 to 9 in which the hollow interior portion is provided with at least one air vent to allow airto escape when filling said interior portion with said colouring or shading material.

11. A device as claimed in any of claims 2 to 10 in which the pontic is provided with a surface coating or layer.

12. A device as claimed in claim 11 in which the pontic comprises a cast metal core and a surface coating or layer, the core being chamfered in a portion thereof to facilitate bonding the surface coating or layer to the metal.

13. A device as claimed in claim 12 in which the cast metal core is of gold and the surface coating or layer is of porcelain.

14. A device as claimed in any of claims 2 to 13 for use in a gap corresponding to more than one tooth which comprises an assembly of more than one pontic as an integral unit for fitting and securing in the gap, said assembly including, in at least one terminally positioned pontic, a passageway with an in let and at least one outlet for bonding material, the or each outlet being adapted to abut against a respective tooth, whereby said terminally positioned pontic may be bonded to the tooth.

15. A device as claimed in claim 14 in which said assembly includes a terminal crown or cap for securing the assembly to a tooth at one end of the gap and the terminally positioned pontic for bonding to said respective tooth at the other end of the gap.

16. A device as claimed in claim 15 in which the terminal crown or cap and the pontic or pontics comprise metal, said metal securing the crown or cap and the pontic or pontics together.

17. A dental device incorporating means for attaching the device to at least one tooth, which comprises a hollow pontic having an inlet and at least one outlet for bonding material, said hollow pontic being placed in a gap between teeth with the or each outlet abutting against a respective tooth, bonding material being introduced into the hollow pontic through the inlet to completely fill the hollow interior of the pontic and, by means of the or each outlet, contact the adjacent tooth or teeth, the material constituting the hollow pontic being removed after the bonding material has set, to leave said set bonding material in the form of a solid moulded pontic bonded to one or both of adjacent teeth.

18. A device as claimed in claim 17 in which an assembly of more than one solid moulded pontic is formed.

19. A device as claimed in any of claims 1 to 18 in which the bonding material is selected from materials which produce micromechanical adhesion to an etched enamel surface of a tooth and materials which produce chemical adhesion to enamel or dentine.

20. A device as claimed in claim 19 in which the bonding material is a composite material.

21. A device as claimed in any of claims 2 to 10, 14,15 and 17 to 20 in which the ponticisformed from a material selected from ceramics, plastics, metals and metal alloys.

22. A device as claimed in claim 21 in which the pontic is formed from a polycarbonate.

23. A dental device substantially as hereinbefore described with particular reference to and as illustrated in any of Figures 2 to 7 of the accompanying drawings.

24. Aformerforforming a passageway in a dental device as claimed in any of claims 1 to 23 which comprises an elongated solid or hollow member having two extremities, means at each extremity constituting abutments and means intermediate said extremities for forming an injection tube to said elongated member when hollow and to the space produced by removal of said elongated member when solid or hollow.

24. A former substantially as hereinbefore described with particular reference to and as illustrated in Figure 8 ofthe accompanying drawings.

25. A method of forming a dental device as claimed in any of claims 1 to 23 which comprises forming a wax mould around a former which is to provide a passageway having an inlet and at least one outlet, forming a casting of investment material around the wax mould, melting out the wax, casting a pontic in the resulting mould and then removing the investment material and former.

26. A method of forming a dental device substantially as hereinbefore described with particular reference to and as illustrated in Figure 9 of the accompanying drawings.