DENTAL FRAMEWORKS AND RELATED APPARATUS AND METHODS

Abstract

A method for forming an integrated or repaired dental framework is disclosed. Portions of dental framework formed of a polymeric material are provided with a male member on a joint surface of one portion and a female member on a joint surfaces of second portion, with the male and female members arranged to mate together to hold the portions together at the joint surfaces and then welded together by ultrasonic welding. Integrated dental frameworks formed by the method using sequential moulding of portions of a patient's mouth are also disclosed. Apparatus and methods for forming a dental prosthetic item such as a portion of such a framework, or a repair piece, by injecting a flowable thermoplastic composition into a mould under pressure, are also disclosed.

Claims

1. A method of joining first and second portions of a dental framework to form an integrated dental framework, wherein the first and second portions of dental framework are each independently formed of a composition comprising a polymeric material, wherein the polymeric material comprises a repeat unit of formula (I): ##STR00007## wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2; the method comprising: providing a male member on a first joint surface of the first portion and a female member on a second joint surface of the second portion, wherein the male and female members are arranged to mate together to hold the first and second portions together with the first and second joint surfaces mutually inter-engaged in the integrated dental framework; bringing the first and second joint surfaces into inter-engagement with the male and female members mated together; and welding the first and second joint surfaces together by ultrasonic welding.

2. A method according to claim 1 wherein the welding the first and second joint surfaces together by ultrasonic welding comprises welding the male and female members together by ultrasonic welding.

3. A method according to claim 1 wherein the polymeric material in the composition of the first portion is the same polymeric material as the polymeric material in the composition of the second portion.

4. A method according to claim 1 wherein the polymeric material in the composition of the first portion is a different polymeric material to the polymeric material in the composition of the second portion.

5. A method according to claim 1 wherein t1=1, v1=0 and w1=0 for the polymeric material in the composition of the first and/or second portions.

6. A method according to claim 1 wherein the first and second joint surfaces are arranged to hinder rotation of the second portion about the male member of the first portion when the first and second joint surfaces are inter-engaged.

7. (canceled)

8. A method according to claim 1 wherein the first portion is a replacement portion for repair of a broken dental framework and the second portion is a remnant portion of said broken dental framework.

9. A method according to claim 8 wherein the female member is formed by forming a hole in the remnant portion prior to bringing the first and second joint surfaces into inter-engagement with the male and female members mated together.

10. A method according to claim 8 wherein the second joint surface comprises a fracture surface of the remnant portion and the first joint surface is shaped to engage with the fracture surface when the first and second joint faces are inter-engaged.

11. (canceled)

12. (canceled)

13. A method according to claim 1 wherein the integrated dental framework comprises at least one further portion of dental framework which is independently formed of a composition comprising a polymeric material, wherein the polymeric material comprises a repeat unit of formula (I): ##STR00008## wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2; the method comprising: providing at least one further joint surface on each further portion which is arranged to inter-engage with a respective further complementary joint surface on the first, second or another portion of the integrated dental framework, providing a further male member on one of the further joint surface and the respective further complementary joint surface and a further female member on the other of the further joint surface and the further complementary joint surface, wherein the further male and female members are each arranged to mate together to hold each further joint surface and the respective further complementary joint surface together, mutually inter-engaged in the integrated dental framework; bringing each further joint surface and respective further complementary joint surface into inter-engagement with their male and female members mated together; and welding the further joint surface and its respective further complementary joint surface together by ultrasonic welding.

14. A method according to claim 13 wherein the polymeric material in the composition of each further portion is the same polymeric material as the polymeric material in the composition of the first and second portions.

15. (canceled)

16. (canceled)

17. A method according to claim 1 wherein the ultrasonic welding is carried out using a sonotrode under manual or computer control.

18. A method according to claim 17 wherein the sonotrode has a terminal welding surface which is circular or substantially equilaterally polygonal in shape.

19. A method according to claim 17 wherein the sonotrode comprises a terminal welding surface having a maximum width of 6 mm or less.

20. An integrated dental framework obtained or obtainable by the method of claim 1.

21. An integrated dental framework comprising at least two interconnected portions of dental framework, wherein each portion of dental framework is independently formed of a composition comprising a polymeric material, wherein the polymeric material comprises a repeat unit of formula (I): ##STR00009## wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2; and wherein each portion is connected to at least one other portion at a joint; wherein each joint comprises a male member on a first joint surface of one portion and a female member on a second joint surface of an adjacent portion; wherein the respective male and female members at the joint are arranged to mate together to hold the first and second portions together with the first and second joint surfaces mutually inter-engaged at the joint; and wherein the first and second joint surfaces are at least partly fused together at the joint.

22. A method for forming a dental prosthetic item, the method comprising: providing a mould having a mould cavity for injection moulding having the shape of the dental prosthetic item; providing a thermoplastic composition in a flowable state in a cavity of a pre-moulding chamber; injecting the flowable thermoplastic composition from the cavity of the pre-moulding chamber into the mould under pressure; cooling the mould to solidify the thermoplastic composition; and removing the dental prosthetic item from the mould cavity; wherein the thermoplastic composition comprises a polymeric material; and wherein the polymeric material comprises a repeat unit of formula (I): ##STR00010## wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2;

23-36. (canceled)

37. A dental prosthetic item obtained or obtainable by the method of claim 22.

38-42. (canceled)

43. Use of a method according to claim 22, wherein the method or apparatus is used to prepare a dental prosthetic item for a patient in a dental laboratory or surgery immediately following a consultation with the patient, whereby the dental prosthetic item is made available to the patient within 24 hours of the consultation.

44. (canceled)

Description

[0100] For a better understanding of the invention, and to show how exemplary embodiments of the same may be carried into effect, reference will be made, by way of example only, to the accompanying diagrammatic Figures, in which:

[0101] FIG. 1 schematically depicts first and second portions which are welded together according to a first embodiment of the invention to form an integrated dental framework;

[0102] FIG. 2A schematically depicts a dental framework with a fracture surface 8;

[0103] FIG. 2B schematically depicts first remnant and second repair portions which are welded together according to a first embodiment of the invention to form a repaired dental framework;

[0104] FIG. 3, schematically depicts an embodiment of an apparatus according to the sixth aspect of the invention, for carrying out an exemplary embodiment of a method according to the fourth aspect of the invention.

[0105] For each of the embodiments set out below, the composition of the dental frameworks and/or portions of dental framework consists of: PEEK-OPTIMA (Trade Mark) LT1-polyetheretherketone (PEEK) of melt viscosity (MV) 0.45 kNsm.sup.2, simply referred to hereinafter a PEEK. Alternatively other variants of PEEK-OPTIMA (Trade Mark) LT2 or LT3 of melt viscosity (MV) in the range between 0.45 and 0.15 could also have been used.

[0106] Turning to FIG. 1, a first portion 1 of dental framework is shown, formed including first joint surfaces 3, 3 each having two male members 5, 5 formed unitarily with the first portion 1. A second portion 2 of dental framework has second joint surfaces 4, 4 (not directly visible in the Figure) each including two female members 6, 6 formed therein. Prosthetic teeth 7 are shown already included in the portions 1, 2 of dental framework but these may be incorporated before or after the welding together of the two portions 1, 2 to from an integrated dental framework.

[0107] In accordance with the method of the first aspect of the invention, the first portion 1 is pushed into the second portion 2 in order to mate the male members 5 with the female members 6, and the male members 5 with the female members 6, so that the first joint surface 3 s also brought into contact with second joint surface 4 and first joint surface 3 is brought into contact with second joint surface 4. The joint surfaces are then welded together ultrasonically by contacting the adjoining surfaces of the portions with the terminal welding surface of a hand-held sonotrode having ultrasonic power supplied thereto (70 KHz at 100 W). In particular, the edges of the female members 6, 6 are welded to the male members 5, 5 where these protrude through the female members. The protruding male members, following ultrasonic welding, may be covered by a crown in order to mask their appearance or to provide a further tooth prosthesis.

[0108] Turning to FIG. 2A, this shows a dental framework 8 which has fractured during wear, generating a fracture surface 9 and breaking the dental framework into a remnant portion 2 and a broken portion 10 which may be discarded. In FIG. 2B, the fracture surface 9 of the remnant portion 2 has been milled to form a second contact surface 4 having a suitable shape for forming a repair joint. Female members 6 have been formed in the second joint surface by drilling holes therein.

[0109] A repair portion 1 has been formed using the original mould details from the broken dental framework, but with a first joint surface 3 formed by computer-aided machining in order to include unitarily formed male members 5, and with the first joint surface 3 and the male members 5 shaped to respectively mate with the female members 6 and complement the second joint surface 4.

[0110] The repair is achieved to form a repaired dental framework by pushing together the opposing joint surfaces 3, 4 so that the male members 5 mate with the female members 6 and contacting the adjoining surfaces of the portions with the terminal welding surface of a hand-held sonotrode having ultrasonic power supplied thereto. For this example, the sonotrode has a square, flat terminal welding surface having 4 mm square sides. In particular, the edges of the female members 6 are welded to the male members 5 where these protrude through the female members (through the back surface of the remnant portion 2, not shown in the Figure).

[0111] Turning to FIG. 3, in this Figure, for the sake of clarity, the components are shown as being of a transparent material so that the details of operation are easily visible. However, it will be understood that such transparency is not a requirement for the invention.

[0112] FIG. 3 shows an apparatus 21 having a support structure 22, supporting a mechanical press 23 and a mould 24. The mould 24 is removably attached to a pre-injection chamber 25 by retainers (screwed plates) 26 and there is a fluid connection 27 connecting a cavity 28 in the pre-injection chamber 25 to the mould cavity 29 in the mould 24.

[0113] In this embodiment, there is a thermal shield 30 surrounding the mould and pre-injection chamber. It will be understood that this shield 30 acts to reduce the cooling rate of the thermoplastic composition following moulding for this exemplary embodiment.

[0114] The mechanical press 23 has a cylindrical tubular wall 31 in which a piston 32 is constrained to travel, driven by a screw 33 turned by handle 34. A spring 35 is located between the piston 32 and a circular plate 36 which is also constrained to travel within the tubular wall 31. A plunger 38 in the form of a rod adapted to be snugly slidable into the pre-injection cavity 28 is rigidly attached to the plate 36. The plate 36 is shown held fixed in the tubular wall 31 by a brake 37 in a locked configuration. The piston 32 is shown compressing the spring 35 against the plate 36 to provide a driving force acting on the plunger 38 through the plate 36 when the brake 37 is released. A pointer 39 arranged to move with the piston 32 indicates the driving force on the scale 40 on the support structure 22.

[0115] In use, the plate 36 is locked in place by the brake 37 and the spring 35 compressed by the piston 32, against the plate 16 by turning the handle 34 so that the screw 33 drives the piston 32 (which is connected to the screw 33 by a tapped hole (not shown) down towards the plate 36. When a desired driving force is reached, as indicated by the pointer 39 on scale 40, granules of PEEK, which have been pre-melted in an oven, are poured into the pre-injection cavity 28 which is then aligned under the piston 38. The brake 37 is released so that the plunger 38 is driven into the pre-injection cavity, forcing the PEEK in its molten, flowable state into the mould cavity 29. The pressure from the mechanical press remains in place as the mould cools (with cooling slowed by the thermal barrier 30 to provide crystallinity in the PEEK of the resulting moulded item). When the PEEK has solidified, the pressure is released by turning back the handle 34 and the moulded dental prosthetic item removed from the mould cavity 29. A timer 41 is provided in the support structure 22 and may be used to estimate when the moulded item has solidified. The mould cavity in this embodiment is composed of a plurality of inter-engageable parts (at least two partsnot shownheld together by retainersnot shown) to facilitate removal of the moulded item from the mould cavity.

[0116] Although a few exemplary embodiments have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims. For example, a different frequency or power of ultrasonics, other than as set out in the embodiments described, may be used for ultrasonic welding. As a further example, the pre-injection chamber 25 in FIG. 3 may include a heater to heat it to a temperature at which the PEEK granules are molten/flowable, in which case the granules may be pre-heated in an oven to a temperature a few degrees (say 20 C.) below their melting temperature, at which they are still solid, so that they can be easily poured into the cavity 28 without them adhering to the container used to transfer them from the oven. The final melting stage may be carried out in the pre-injection chamber 25.

[0117] In summary, a method for forming an integrated or repaired dental framework is disclosed. Portions of dental framework formed of a composition comprising a polymeric material:

##STR00005##

wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2;
are provided with a male member on a joint surface of one portion and a female member on a joint surfaces of second portion, with the male and female members arranged to mate together to hold the portions together at the joint surfaces and then welded together by ultrasonic welding. Integrated dental frameworks formed by the method are also disclosed.

[0118] Large dental frameworks may thus be formed from the easily machinable, biocompatible polymeric material by moulding portions of a patient's mouth sequentially and forming an integrated framework from the moulds. Similarly, broken dental frameworks may be easily and conveniently repaired.

[0119] The invention provides methods for forming a dental prosthetic item, such as a repair portion, involving injecting a flowable thermoplastic composition from into a mould under pressure and cooling the mould to solidify the thermoplastic composition. The thermoplastic composition comprises a polymeric material with a repeat unit of formula (I):

##STR00006##

[0120] wherein t1 and w1 independently represent 0 or 1 and v1 represents 0, 1 or 2.

[0121] Apparatus for putting the methods into effect and dental prosthetic items made using the method are disclosed, as is the use of the methods and apparatus for rapid preparation of prostheses following a consultation.

[0122] The invention allows for easy and rapid formation of durable and non-toxic dental prosthetic items in a dental laboratory or surgery without the need for complex apparatus or handling of toxic monomers.

[0123] Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

[0124] All of the features disclosed in this specification (including any accompanying claims and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

[0125] Each feature disclosed in this specification (including any accompanying claims and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.