AU2012202448A1 - Dental apparatus and method - Google Patents

Abstract

Dental apparatus is provided that includes first and second base layers with releasably engageable connection surfaces. A first one of the layers is configured to support a row of model teeth and the first layer, including the row of model teeth, can be 5 divided into multiple sections. The row of model teeth can be reconstructed by connecting the divided sections to the second base layer. The base layers have releasably engageable connection elements that are integrally formed with, or permanently fixed to, the connection surfaces. An articulation mechanism comprising at least two flexible members connected between first and second bases is also 10 disclosed. 20b 19b 19b 20b o 18 Fig. la Fig. lb 20a 19a 34 33 34 19a 20a 10Fig..

Description

1 AUSTRALIA Patents Act 1990 ESTHETIC DENTAL LABORATORIES PTY LTD COMPLETE SPECIFICATION STANDARD PATENT Invention Title: Dental apparatus and method The following statement is a full description of this invention including the best method of performing it known to us:- 1A Dental apparatus and method Cross-Reference to Related Applications 5 The present application claims priority from Australian Provisional Patent Application No 2011901584 filed 29 April 2011, the contents of which are incorporated herein by reference. Field 10 This invention relates to dental apparatuses and methods, and particularly, although not necessarily exclusively, methods and apparatuses for preparing a dental prosthesis. Background 15 A dental prosthesis can include an artificial tooth structure which is designed to replace all or part of one or more teeth that have been partially or wholly lost, e.g., through decay or other damage. It is important that a dental prosthesis conforms not only to the shape of the teeth or parts of teeth that it is designed to replace, but to the shape of neighbouring 20 teeth, the 'bite' of the patient's mouth and the colouring of the patient's teeth. To this end, to prepare a dental prosthesis, it is known to obtain a precise model of a patient's teeth, e.g. a bottom and/or top row of teeth, the model being obtained by taking a mold of the teeth using an impression material, and then cast the model using dental plaster. The model is then used to determine an appropriate configuration for the 25 dental prosthesis. Subsequently, a green body, such as a block of zirconia material, is milled in accordance with the determined configuration to arrive at the dental prosthesis, which is then coloured as appropriate and sintered. The upper and lower rows of model teeth are normally mounted on respective upper and lower bases, each base usually formed of a single block of poured and set 30 dental plaster. The rows of model teeth are mounted to the bases using pin fasteners drilled into pin holes. When it is desired to prepare a dental prosthesis for application to, or replacement of, a single tooth or selection of teeth, the corresponding model 2 tooth or teeth, and surrounding model gum area, may be divided from the remainder of the row of model teeth and removed therefrom. This divided section may be worked upon to prepare an appropriate support for a dental prosthesis, and a dummy prosthesis may be applied to this support and tested. Each divided section of the row 5 of model teeth can be mounted back on the base by pinning the divided section to the base using the pin fasteners and drill holes as described above. This pinning process can be time consuming and awkward. When upper and lower rows of teeth are modelled, the 'bite' of the patient's teeth, e.g. prior to, or subsequent to, the application of a dummy dental prosthesis, 10 may be tested. To carry out the testing, an articulator is commonly used. An articulator is essentially an artificial jaw mechanism, comprising two arms hinged to one another on which the upper and lower bases are mounted. Mounting is commonly achieved by a crude casting of dental plaster over at least part of the arms. The articulators can be relatively cumbersome, expensive and lacking in versatility. 15 Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application. 20 Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. 25 Summary According to a first aspect, there is provided dental apparatus comprising: a first base layer having two opposing sides, one of the sides of the first base layer providing a support for a row of model teeth, and the other of the sides providing a first connection surface; 30 a second base layer having two opposing sides, one of the sides of the second base layer providing a second connection surface that is configured to be releasably connected to the first connection surface, 3 wherein the releasable connection between the first and second connection surfaces is by a plurality of interlocking connection elements integrally formed with, or permanently fixed to, the first and second based layers. According to a second aspect, there is provided dental apparatus comprising: 5 a first base layer having two opposing sides, one of the sides of the first base layer providing a support for a row of model teeth, and the other of the sides of the first base layer providing a first connection surface; a second base layer having two opposing sides, one of the sides of the second base layer providing a second connection surface, 10 wherein the first base layer comprises one or more first connection elements integrally formed with, or permanently fixed to, the first connection surface; wherein the second base layer comprises one or more second connection elements integrally formed with, or permanently fixed to, the second connection surface, 15 wherein the second connection elements are releasably engageable with the first connection elements, and wherein the first connection surface is configured to be releasably connected to the second connection surface upon releasable engagement between the first and second connection elements. 20 The connection elements may be a combination of protrusions and recesses, the recesses being sized to receive the protrusions to effect interlocking and engagement between the connection elements. Protrusions may be provided exclusively on one of the releasably connectable surfaces and recesses may be provided exclusively on the other of the releasably connectable surfaces. 25 Alternatively, a combination of protrusions and recesses may be provided on each of the releasably connectable surfaces. The connection elements may provide a connection mechanism similar to, or identical to, and/or based on the technical principles of, a connection mechanism between LegoTm blocks. Walls of the protrusions and/or recesses may be resiliently flexible and may provide for an 30 interference fit. Other types of connection elements are conceivable, however, such as releasable adhesive elements, hook and loop fasteners, or otherwise. The first and second connection elements may be evenly distributed over a region of each of the first and second connection surfaces, respectively. The first connection elements may be distributed over at least at a region of the first connection 4 surface located directly beneath, and extending substantially the length of, the row of model teeth when the model teeth are supported (e.g., mounted) on the first base layer. The connection elements may have a size, and a distribution density, such that there is at least one set of mutually interlocking/engaging connection elements (e.g., at 5 least one protrusion and at least one corresponding recess) per tooth of the row of model teeth. The arrangement may be such that there is substantially at least one set of mutually interlocking/engaging connection elements beneath each model tooth when the model teeth are supported on the first base layer. The row of model teeth may be permanently fixed to the first base layer, e.g., 10 by gluing. When the row of model teeth is supported on the first base layer, one or more teeth, along with a portion of the base layer directly supporting the one or more teeth, may be divided (e.g., cut) from the remainder of the row of model teeth and the remainder of the first base layer and removed. Thus, when the row of model teeth is supported on the first base layer, the combination of the row of model teeth and the 15 first base layer may be a single, dividable element with a plurality of first connection elements on one side for releasably connecting to the second connection elements of the second base layer. The removed section of model teeth may correspond to damaged teeth, for example, for which the preparation of a dummy or final prosthesis, e.g. one or more crowns, is desired. By removing the section, an appropriate shape 20 and configuration for the prosthesis can be more easily determined. Once the prosthesis has been prepared, the removed section may be repositioned, along with the prosthesis, with the remainder of the row of model teeth on the first base layer, and connected to the second base layer by virtue of the first and second connection elements. 25 The distribution and number of first connection elements at the first connection surface may ensure that any section of the first base layer that is divided, and which supports one or more model teeth, will have one or more first connection elements that are releasably connectable to one or more corresponding second connection elements of the second base layer. Thus, there can be no need to reposition, or add, 30 any connection elements after a section is divided. In one embodiment, the connection elements may have different shapes and/or configurations at different parts of the connection surfaces. The arrangement may be such that a divided section of the row of model teeth and first base layer may be releasably connected via engagement between the first connection elements and the 5 second connection elements only at a particular portion of the second base layer. This may ensure that, when divided sections are releasably connected to the second base layer, the row of model teeth will be re-assembled in appropriate order automatically, preventing any mix-up or misalignment of divided sections, for example. 5 The first and/or second base layers may be formed of a polymeric material, e.g. plastics material. The base layers can be pre-formed (e.g. factory formed). This may mean that the only part of the apparatus that may need to be poured or moulded by the user (e.g. the dentist or clinician) in preparation of the prosthesis is the row of model teeth. The base layers may be formed of a material that is relatively rigid, but which 10 is relatively easy to cut. By employing connection elements that are permanently fixed or integrally formed with the first and second base layers and that are configured and distributed with respect to the base layers in the manner described above, there may be no need for a dentist or clinician to reposition any connection elements relative to the base 15 layers in the process of preparing the prosthesis. For example, there may be no need for a dentist or clinician to pin any elements, which might otherwise require the drilling of pin holes and the setting of pins in the pin holes. Generally, a connection element may be "permanently fixed" to one of the base layers, e.g. by gluing or by other fastening means, such that it would not be releasable from the base layer, or at 20 least would not be intended for release from the base layer, during normal preparation of the dental prosthesis. Generally, a connection element may be "integrally formed" with one of the base layers by being formed with at least a portion of the base layer in one-piece. The apparatus discussed herein may provide a more convenient, and less time-consuming, means for mounting and repositioning model teeth on a base. 25 According to a third aspect, there is provided a method of preparing a dental prosthesis comprising: obtaining a row of model teeth; mounting the row of model teeth to one side of a first base layer, the opposite side of the first base layer providing a first connection surface; 30 dividing a section of the row of model teeth and first base layer; preparing a dental prosthesis using the divided section; connecting the first connection surface of the first base layer of the divided section to a second connection surface of a second base layer, wherein the connection between the first and second connection surfaces is by a plurality of interlocking 6 connection elements integrally formed with, or permanently fixed to, the first and second based layers. According to a fourth aspect, there is provided a method of preparing a dental prosthesis comprising: 5 obtaining a row of model teeth; mounting the row of model teeth to one side of a first base layer, the opposite side of the first base layer providing a first connection surface; dividing the first base layer into two or more sections, each section having a respective portion of the row of model teeth mounted on one side and a respective 10 portion of the first connection surface on the opposite side; preparing a dental prosthesis using at least one of the divided sections; substantially reforming the model row of teeth by releasably connecting the portion of the first connection surface of each of the divided sections to a second connection surface of a second base layer 15 wherein the releasable connection between the first and second connection surfaces is by a plurality of first and second connection elements integrally formed with, or permanently fixed to, the first and second connection surfaces. The method of the third or fourth aspect may be carried out using dental apparatus according to the first or second aspect. 20 According to a fifth aspect, there is provided a dental apparatus comprising: a first base for supporting a first row of model teeth; a second base for supporting a second row of model teeth; and at least two flexible members connectable between the first and second bases such as to provide articulation between the first and second bases. 25 The apparatus of the fifth aspect may be used to analyse the alignment or 'bite' between the first and second rows of model teeth, for example. The flexible members may be configured to allow relative rotation between the first and second bases. The relative rotation may be provided as a result of the flexible properties of the flexible members. Relative rotation may be about at least 30 two perpendicular axes. For example, the flexible members may be configured to allow the first and second bases to relatively rotate about a first axis such as to at least partially imitate the opening and closing of a human jaw when the rows of model teeth are mounted to the first and second bases. Additionally, the flexible member may be configured to allow the first and second bases to relatively rotate about a 7 second axis, perpendicular to the first axis, such as to allow relative medial/lateral movement of the first and second bases. This relative lateral movement may cause a sideways displacement of the rows of teeth when the rows of teeth are mounted to the first and second bases. 5 Additionally or alternatively, the flexible members may be configured to allow linear movement between the first and second bases. Accordingly, the first and second rows of model teeth may be moved towards or away from each other in a linear fashion, when the rows of teeth are mounted to the first and second bases, with the flexible members acting as guides. To achieve the linear motion, at least one of 10 the first and second bases may be slidably connected to the flexible members. The flexible members may be connected to a region toward the rear of the first and second bases, e.g. at a position level with, or to the rear of, model molars, when rows of model teeth are mounted to the bases. In some embodiments, there may be no other elements connecting the first and second bases together. Thus, as few as two 15 flexible members may connect the first and second bases together and provide for the articulation between the bases as discussed above. In some embodiments, however, three of more flexible members may be employed, to provide a more secure articulation between the first and second bases. Each flexible member may be a flexible rod or other type of elongate flexible 20 element, for example. The flexible members may extend substantially parallel to each other between the first and second bases. The flexible members may be separated from each other, e.g. by between 0.25 cm and 2.5 cm, or between 0.5 cm and 1.5 cm or by about 1 cm, etc. The flexible members may have a cross-sectional diameter, perpendicular to their longitudinal axes, of about 2 mm to 5 mm, or about 3 mm, or 25 otherwise. The flexible members may comprise polymeric material, e.g. plastic material, for example. The flexible members may comprise thermoplastics material, such as nylon, for example. When thermoplastic material is used, for example, one or more of the flexible members may be heated such as to reconfigure their natural shape, configuration 30 and/or orientation, relative to each other and/or relative to one or both of the bases. Thus, heating of the flexible members may be employed to reconfigure the 'bite' between the first and second rows of model teeth when mounted to the respective bases.

8 By using flexible members as set forth above, which in one embodiment may be two or more substantially parallel elongate thermoplastic rods, a relatively convenient and versatile articulation between the first and second bases may be achieved at relatively low cost. The articulation arrangement may be cheaper, less 5 bulky and/or more versatile, than other dental articulators. Apparatus according to the fifth aspect may be combined with apparatus according to the first or second aspect. To this extent, the first and/or second base may comprise first and second releasably connectable base layers as set forth above. According to a sixth aspect, there is provided a method of adjusting an 10 articulation between first and second rows of model teeth, wherein the first row of model teeth is supported on a first base, and the second row of model teeth is supported on a second base, and at least two flexible members are connected between the first and second bases such as to provide articulation between the first and second bases, the method comprising: 15 heating the flexible members to reconfigure the natural shape, configuration and/or orientation of the flexible members. The method of the sixth aspect may be carried out using dental apparatus according to the fifth aspect. 20 Brief description of the drawings By way of example only, an embodiment is now described with reference to the accompanying drawings, in which: Figs. la and lb show top and bottom views, respectively, of a first base layer, of a first base, for use in a dental apparatus according to an embodiment of the present 25 disclosure, the first base layer having a row of model teeth mounted thereon; Fig. 2 shows a top view of a second base layer, of the first base, for use in the dental apparatus according to the embodiment of Fig. 1; Fig. 3 shows a side cross-sectional view of the first and second base layers of Figs. 1 a, lb and 2 oriented for releasable connection to each other to form the first 30 base; Fig. 4 shows a side view of a divided section of the first base layer of Fig. 1, having a model tooth mounted thereon, and a dental prosthesis for mounting on the model tooth; 9 Fig. 5 shows a top view of the first base layer of Fig. 1 connected to the second base layer of Fig 2, the first base layer having a divided section; Fig. 6 shows a top view of a second base for use in a dental apparatus according to an embodiment of the present disclosure; 5 Fig. 7 shows a front view of the first base of Figs. la to 3 articulatingly connected to the second base of Fig. 6; Fig. 8 shows a side view of the first base of Figs. la to 3 articulatingly connected to the second base of Fig. 6, the first and second bases each having a row of model teeth mounted thereon; 10 Fig. 9 shows a bottom view of a first base layer of a first base for use in dental apparatus according to another embodiment of the present disclosure; Fig. 10 shows a top view of a second base layer, of the first base, for use in the dental apparatus according to the embodiment of Fig. 9; and Fig. 11 shows a bottom view of a base layer according to another embodiment 15 of the present disclosure for supporting a partial row of model teeth. Detailed Description According to an embodiment, dental apparatus is provided having a first base 10 including a first base layer 11 and second base layer 12. Fig. la and lb show top 20 and bottom views, respectively, of the first base layer 11, the first base layer 11 having a row of model teeth 13 mounted on a first surface 14 thereof. With reference to Fig. Ib, on the opposite side of the first base layer 11 from the model teeth 13, the first base layer 11 has a connection surface 15 for connecting the first base layer 11 to the second base layer 12 to form the first base 10. The connection surface 15 of the 25 first base layer includes a plurality of recesses or orifices 18 that act as a first set of connection elements. Fig. 2 shows a top view of the second base layer 12. With reference also to Fig. 3, the second base layer 12 comprises a connection surface 16 that includes a plurality of projections 17, acting as a second set of connection elements. The 30 projections 17 of the second base layer are configured to fit snugly in the corresponding recesses 18 of the first base layer 11, such as to releasably connect the first and second base layers 11, 12 together to form the first base 10. In view of this, when seen in plan view, the shape and distribution of the projections 17 and the recesses 18 are substantially identical.

10 Referring to Fig. 2, the projections 17 of the second base layer 12 are arranged in inner and outer arcuate rows 19a, 20a, generally conforming to the arc of a standard row of model teeth. In this embodiment, in each row, projections 17 are provided by a plurality of spaced apart tubes 171 projecting from the connection surface 16 5 substantially perpendicular to the plane of the connection surface 16. In the outer arcuate row 20a, additional projections are also provided, in the form of panels or walls 172 connected between adjacent tubes 171 of the outer row 20a. Referring to Fig. I b, the recesses 18 of the first base layer I include inner and outer arcuate rows 19b, 20b of substantially cylindrical bores 181, arranged to receive the corresponding 10 tubes 171 of the second base layer 12, and slots 182 connected between adjacent bores 181 of the outer arcuate row 20b, arranged to receive the corresponding panels or walls 172 of the second base layer 12. The tubes 171 are generally hollow and compressible. Accordingly, when the tubes 171 are inserted into the bores 181, the walls of the bores 181 can cause the 15 tubes 171 to compress, producing a stronger frictional fit between the tubes 171 and bores 181, and thus a stronger connection between the first and second base layers 11, 12. Fig. 3 shows the first and second base layers 11, 12 oriented for releasable connection to each other to form the first base 10. In use, a row of model teeth 13 is prepared and mounted to the first surface 14 20 of the first base layer 11, as shown in Fig. Ia, e.g., by gluing. The mounting can cause substantially permanent fixing of the model teeth 13 to the first base layer 11. Subsequently, with reference to Figs. 4 and 5, a tooth 131 (or teeth) of the row of model teeth 13 can be divided, along with the portion of the first base layer 11 directly underneath the tooth 131, from the remainder of the model teeth and the first 25 base layer 11. The divided section 111 can then be worked on in isolation. A dental prosthesis 132, e.g. a crown, can be prepared for the model tooth 131, and the fitting of the prosthesis 132 on that tooth 131 can be tested. The divided section 11 is then releasably connected, along with the remaining sections 112, 113 of the first base layer 11 that support the rest of the model teeth 13, 30 to the second base layer 12, through engagement between the projections 17 and recesses 18. This can be performed to reform the row of model teeth 13, as shown in Fig. 5, allowing the configuration of the dental prosthesis 132 to be analysed in combination with the entire row of model teeth 13.

I1 The arrangement of the connection elements including the projections 17 and recesses 18 is such that the different, divided sections 111, 112, 113, of the model teeth 13 and first base layer 11, can be connected only at specific positions of the second base layer 12. In this embodiment, there is in fact only one respective position 5 at which each divided section 111, 112, 113 can be connected to the second base layer 12, which ensures that the row of model teeth 13 will be reformed automatically in an appropriate order and alignment, when the sections 111, 112, 113 are connected to the second base layer 12. On the whole, this is achieved in this embodiment by providing the tubes 171 and cylindrical bores 181 with different diameters at different positions 10 of the first and second base layers 11, 12, and providing the walls 172, and corresponding slots 182, at the outer arcuate rows 20a, 20b only. As can be seen, with reference to Figs. lb and 2, the diameters of the tubes 171 and bores 181 of the outer rows 20a, 20b increase incrementally from one end to the other, and the diameters of the tubes 171 and bores 181 of the inner rows 19a, 19b also increase incrementally 15 from one end to the other, although in an opposite direction to the outer rows 20a, 20b in this embodiment. To ensure that the connection elements 171, 181 provide means to releasably connect together the respective portions of the first and second base layers 11, 12 within any divided section I11 (which can have a breadth as narrow as a single model 20 tooth), there are provided connection elements 171, 181 on each base layer, at least in the outer arcuate rows 20a, 20b, which are substantially the same or greater in number to the number of teeth 13, and which are generally evenly spaced apart across the length of the row of model teeth 13. Although, in this embodiment, a divided section 111 may not always have single complete connection element 171, 181 connecting the 25 respective portions of the first and second base layers together (each surface may comprise e.g. half of one connection element, and half of an adjacent connection element, etc.), a robust connection between the layers of the divided section may nonetheless be achieved. Furthermore, connection may be enhanced by the engagement between the wall 171 and the slot 182, which can each substantially 30 traverse any divided section 111. Dental apparatus according to another embodiment is now discussed with reference to Figs. 6 to 8. In this apparatus, an articulation mechanism is provided to control articulated movement between first and second bases 10, 30, which bases support rows of model teeth 132, 133. The apparatus can be used to test the 12 alignment and 'bite' between the rows of model teeth 132, 133. In this embodiment the first base 10 is configured in accordance with the base 10 described above with respect to Figs. I to 5. Thus, the first base 10 includes first and second releasably connectable layers 11, 12, the first layer 11 having a first row of model teeth 132 5 mounted thereon. The second base 30 is provided by a single plate element 31, upon which a second row of model teeth 133 is mounted. However, in alternative embodiments, the second base could also be configured in a similar or identical manner to the base 10, if, for example, a dental prosthesis is to be tested in relation to both the first and second rows of model teeth. Conversely, the first base could be 10 configured in a similar or identical manner to the single plate element 31 of the second base 30, if a very simple alignment test between rows of model teeth is to be performed, without preparation of any dental prosthesis, for example. To provide articulated movement between the first and second bases 10, 30, the apparatus comprises a plurality of flexible, elongate, connection members. In this 15 embodiment, the connection members are two substantially cylindrical nylon rods 32. The rods 32 extend substantially parallel to each other and are spaced apart by approximately 1 cm in this embodiment. The rods are connected to the first and second bases 10, 30 at a substantially central region between the rear (e.g. between the rear molars) of the first and second rows of model teeth 132, 133. 20 In this embodiment, the rods 32 are fixed to the second layer 12 of the first base 10 via a screw mechanism. In more detail, with reference to Fig. 2, the second layer 12 includes two bores 33, opening at the connection surface 16 of the second layer 12, in which the ends of the rods 32 can be received, and two screw holes 34, extending between the bores 33 and a rear surface of the second layer 12, for 25 receiving screws to fix the ends of the rods 32 in the bores 33. The rods 32 are slidably connected to the second base 30. To achieve the slidable connection, the plate element 31 includes two holes 35 extending through its thickness, through which the rods 32 are slidably received. The slidable connection facilitates linear movement between the first and second bases 10, 30, as indicated by 30 arrow 41. Accordingly, the first and second rows of model teeth 132, 133 can be moved towards or away from each other in a linear fashion, with the rods 32 acting as guides. The rods 32 are configured to allow relative rotation between the first and second bases 10, 30. The relative rotation is provided as a result of the flexible 13 properties of the rods 32. The rods 32 are configured to allow the first and second bases to relatively rotate about a first axis, such as to at least partially imitate the opening and closing of a human jaw when the rows of model teeth 132, 133 are mounted to the first and second bases 10, 30, as indicated by arrow 42. Additionally, 5 the flexible member are configured to allow the first and second bases to relatively rotate about a second axis, perpendicular to the first axis, such as to allow relative medial/lateral movement of the first and second bases, as indicated by arrow 43. This relative lateral movement may cause a sideways displacement of the rows of teeth 132, 133. 10 The rods 32 are formed of thermoplastic (Nylon in this embodiment), meaning that they can be heated, e.g. using a heat gun, to reconfigure their natural shape, configuration and/or orientation, relative to each other and/or relative to one or both of the bases 10, 30. Thus, heating of the rods 32 may be employed to reconfigure the 'bite' between the first and second rows of model teeth 132, 133 when mounted to the 15 respective bases 10, 30. Although only two rods 32 are provided in this embodiment, additional rods, e.g. a third rod, may be provided to increase the stability of the articulation. To connect a third rod, for example, the plate element 30 may include an additional hole 36. Where three rods are used, the rods may be arranged substantially at the three 20 side edges of an imaginary triangular prism, for example. Figs. 9 and 10 show a bottom view of a first base layer 41, and a top view of a second base layer 42, respectively, for dental apparatus according to a further embodiment. The apparatus is similar to the apparatus described above with respect to e.g., Figs. I to 3. However, the first and second base layers 41, 42 have an 25 arrangement of connection elements, to connect the first and second base layers 41, 42 together to form a first base, which differs from the arrangement described with respect to Figs. I to 3. In place of using bores to form recesses in a relatively thick portion of one of the two base layers, an additional set of tubes is provided in this embodiment, the 30 walls of which have inner surfaces defining recesses or orifices. In particular, a plurality of substantially cylindrical tubes 48 project from the engagement surface 45 of the first base layer 41, and the walls of the tubes 48 having inner surfaces that define recesses for receiving corresponding substantially cylindrical tubes 47 projecting from the engagement surface 46 of the second base layer 42. The 14 distribution and sizing of the tubes/recesses is similar to that of the corresponding connection elements 171, 181 of Figs. I to 3. However, by employing tubes to form recesses, rather than bores, the average thickness across the first base layer 41 can be reduced. This may not only reduce manufacturing costs, but also make it easier to 5 cut/divide sections of the first base layer 41, and may reduce heat generation during the cutting process, which could be potentially damaging to the apparatus. Further, the walls of the tubes 48 can have greater flexibility than surfaces of bores, and therefore an improved interference fit between the connection elements can be achieved. Related to this, to achieve an improved interference fit, the natural 10 circumferences of the inner surfaces that define the recesses of the tubes 48 may be slightly smaller than the natural circumferences of the outer surfaces of the tubes 47 that are received in the recesses. The apparatus of this embodiment also differs from apparatus described respect to Figs. I to 3 in that the connection elements used to connect the first and 15 second base layers include engageable peripheral walls 43, 44. In particular, a first peripheral wall 43 is provided on the first base layer 41, which projects from the engagement surface 45 of the first base layer 41. The first wall 43 is continuous and surrounds all of the projecting tubes 48. The first wall 43 has a plurality of teeth 431 on its outer surface. The first wall 43 generally follows a path that is consistently 20 between about 1 mm to 2 mm inside of the edges 432 of the engagement surface 45 of the first base layer 41. A second engageable wall 44 is provided on the second base layer 42, which projects from the engagement surface 46 of the second base layer 42. The second wall 44 is also continuous and surrounds all of the projecting tubes 47. The second wall 44 has a plurality of teeth 441 on its inner surface. The second wall 25 44 generally follows the edges 442 of the engagement surface 46 of the second base layer 42. The teeth 431, 441 of the first and second walls 43, 44 are configured to slot together when the connection elements of the first and second base layers 41, 42, including the tubes 47, 48 and the walls 43, 44, are brought together for engagement. The engageable first and second walls 43, 44 may provide increased stability to the 30 releasable engagement between the first and second base layers 41, 42. Although apparatus depicted in various Figures discussed above includes entire rows of model teeth, the apparatus may be modified for use instead with partial rows of model teeth. For example, as represented in Fig. 11, one or more base layers 50 having a reduced size may be provided, e.g. for supporting a lateral or front section of 15 a row of model teeth only. Generally, the same or similar principles and techniques described herein may be employed in relation to entire rows of model teeth and also partial rows of model teeth. It will be appreciated by persons skilled in the art that numerous variations 5 and/or modifications may be made to the invention as shown in the specific embodiments without departing from the scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (35)

1. Dental apparatus comprising: a first base layer having two opposing sides, one of the sides of the first base layer providing a support for a row of model teeth, and the other of the sides of the 5 first base layer providing a first connection surface; a second base layer having two opposing sides, one of the sides of the second base layer providing a second connection surface, wherein the first base layer comprises one or more first connection elements integrally formed with, or permanently fixed to, the first connection surface; 10 wherein the second base layer comprises one or more second connection elements integrally formed with, or permanently fixed to, the second connection surface, wherein the second connection elements are releasably engageable with the first connection elements, and 15 wherein the first connection surface is configured to be releasably connected to the second connection surface upon releasable engagement between the first and second connection elements.

2. The apparatus of claim 1, wherein the first and second connection elements 20 comprise protrusions and recesses, wherein the protrusions are at least partially locatable within the recesses to releasably engage the first and second connection surfaces.

3. The apparatus of claim 2, wherein: 25 the first connection elements comprise one or more protrusions and the second connection elements comprise one or more recesses, or the second connection elements comprise one protrusions and the first connection elements comprise one or more recesses, or the first connection elements comprise one or more protrusions and one or 30 more recesses and the second connection elements comprise one or more protrusions and one or more recesses.

4. The apparatus of claim 2 or 3, wherein the protrusions and/or recesses comprise resiliently flexible walls configured to flex upon the releasable engagement. 17

5. The apparatus of any one of claims 2 to 4, wherein at least one of the protrusions is provided by a substantially cylindrical element projecting from the first or second connection surface. 5

6. The apparatus of any one of claims 2 to 5, wherein at least one of the recesses is provided by a substantially cylindrical element projecting from the first or second connection surface. 10

7. The apparatus of any one of claims 2 to 6, wherein at least one of the recesses is provided by a bore in the first or second connection surface.

8. The apparatus of any one of the preceding claims wherein the first connection elements are distributed over at least at a region of the first connection surface located 15 beneath, and extending substantially the length of, an area of the first base layer configured to support the row of model teeth.

9. The apparatus of any one of the preceding claims, wherein the total number of first connection elements and the total number of second connection elements are 20 substantially equal to or greater than the total number of model teeth to be supported on the first base layer.

10. The apparatus of any one of the preceding claims, wherein the first connection elements comprises at least one first wall and the second connection elements 25 comprise at least one second wall, the first and second walls being releasably engageable with each other.

11. The apparatus of claim 10, wherein each of the first and second walls has a toothed surface. 30

12. The apparatus of any one of the preceding claims wherein the row of model teeth is mounted to the first base layer by gluing. 18

13. The apparatus of any one of the preceding claims wherein the first base layer is dividable into two or more sections, each section configured to support on one side a portion of the row of model teeth and having at least a part of one or more of the first connection elements on the opposite side. 5

14. The apparatus of claim 13, wherein the divided sections of the first base layer are each releasably engageable to the second base layer to reform the first base layer and the row of model teeth. 10

15. The apparatus of claim 13 or 14, wherein the first base layer is dividable by cutting.

16. The apparatus of claim 15 wherein, prior to cutting, the first base layer is a one-piece element formed of plastics material. 15

17. The apparatus of any one of the preceding claims, wherein each of the first connection elements is releasably engageable with a respective one only of the second connection elements. 20

18. The apparatus of any one of the preceding claims, wherein the first and/or second connection elements are distributed in one or more arcuate rows on the first and/or second connection surfaces, respectively.

19. The apparatus of any one of the preceding claims, wherein a plurality of the 25 first connection elements have different relative sizes and a plurality of the second connection elements have different relative sizes.

20. The apparatus of claim 18 wherein in each row, the connection elements increase or decrease in size from one end of the row to another end of the row. 30

21. A method of preparing a dental prosthesis comprising: obtaining a row of model teeth; mounting the row of model teeth to one side of a first base layer, the opposite side of the first base layer providing a first connection surface; 19 dividing the first base layer into two or more sections each section having respective portion of the row of model teeth mounted on one side and a respective portion of the first connection surface on the opposite side; preparing a dental prosthesis using at least one of the divided sections; 5 substantially reforming the model row of teeth by releasably connecting the portion of the first connection surface of each of the divided sections to a second connection surface of a second base layer wherein the releasable connection between the first and second connection surfaces is by a plurality of first and second connection elements integrally formed 10 with, or permanently fixed to, the first and second connection surfaces, respectively.

22. The method of claim 21, wherein the first and second base layers are the first and second base layers of the apparatus according to any one of claims 1 to 21. 15

23. The apparatus of any one of claims I to 20 wherein the first and second base layers are releasably connectable to form a first base, the apparatus further comprising: a second base having a side for supporting a row of model teeth; an articulation mechanism connecting the first base to the second base. 20

24. The apparatus of claim 23 wherein the articulation mechanism comprises at least two flexible members each connected between the first and second bases.

25. Dental apparatus comprising: 25 a first base for supporting a first row of model teeth; a second base for supporting a second row of model teeth; and at least two flexible members connectable between the first and second bases such as to provide articulation between the first and second bases. 30

26. The apparatus of claim 25 wherein the connection members are each elongate and the directions of elongation of the connection members are substantially parallel.

27. The apparatus of claim 24 or 25 wherein the connection members are rods. 20

28. The apparatus of claim 25, 26 or 27, wherein the connection members allow relative rotation between the first and second bases.

29. The apparatus of claim 28, wherein the connection members are slidably 5 connected to'one or more of the first and second bases.

30. The apparatus of any one of claims 25 to 29, wherein the connection members are separated by less than 5 cm. 10

31. The apparatus of claim 30, wherein the connection members are separated by between 0.5 and 1.5 cm.

32. The apparatus of any one of claims 25 to 31, wherein the connection members comprise polymeric material. 15

33. The apparatus of claim 32, wherein the connection members comprise nylon.

34. The apparatus of any one of claims 25 to 33 wherein the connection members are heatable to reconfigure their natural shape, configuration and/or orientation. 20

35. A method of adjusting an articulation between first and second rows of model teeth, wherein the first row of model teeth is supported on a first base, and the second row of model teeth is supported on a second base, and at least two flexible members are connected between the first and second bases such as to provide articulation 25 between the first and second bases, the method comprising: heating the flexible members to reconfigure the natural shape, configuration and/or orientation of the flexible members.