WO2016142407A1

WO2016142407A1 - Process for producing a denture

Info

Publication number: WO2016142407A1
Application number: PCT/EP2016/054985
Authority: WO
Inventors: Brian SCHOTTLANDER
Original assignee: Davis Schottlander and Davis Ltd
Current assignee: Davis Schottlander and Davis Ltd
Priority date: 2015-03-09
Filing date: 2016-03-09
Publication date: 2016-09-15
Anticipated expiration: 2017-09-09
Also published as: GB201503953D0; GB2536231A

Abstract

A process for producing a denture comprises the steps of (i) producing a modified denture flask utilising one or more digital techniques, the flask comprising a hollow section having a shape and size corresponding to both the denture base and the teeth of the denture, (ii) placing teeth within the hollow section of the flask, and (iii) forming the denture.

Description

PROCESS FOR PRODUCING A DENTURE

FIELD OF THE INVENTION

The present invention relates to a new process for producing a denture utilising digital techniques to produce a modified type of denture flask, which is characterised in that it includes a hollow section having a shape and size corresponding to both the denture base and the individual teeth of the denture. Subsequently, individual teeth may be placed within the hollow section of the flask, and finally traditional techniques may be used to form the denture.

BACKGROUND OF THE INVENTION

Dentures are prosthetic devices constructed to replace missing teeth. They are supported by the surrounding soft and hard tissues of the oral cavity. Complete dentures replace all of the teeth in the upper and/or the lower jaw, whereas partial dentures only replace some of the teeth in the jaw concerned. For example, partial dentures may replace one or more front teeth and/or one or more of the posterior teeth. Conventional dentures are removable as and when required.

In natural human dentition, the tooth distribution in each quadrant of the mouth consists of three front teeth, and four or five posterior teeth including two pre-molars and two or three molars. When constructing a complete denture, either three or more typically four posterior teeth are used in each quadrant. When constructing a partial denture, the number of teeth used depends on factors such as the number of remaining natural teeth and the space available. The third molar tooth is not always present in the natural human dentition, and is not usually included in dentures.

Dentures should be retentive, comfortable and provide support for the cheeks and lips. They should allow effective mastication, acceptable aesthetics, clear phonetics, and contribute to the wearer's confidence and self-esteem.

The construction of complete dentures involves a number of clinical and laboratory stages. In traditional denture construction, impressions of one or both jaws are first taken by the clinician. These are commonly referred to as primary impressions.

Into these impressions, technicians at a dental laboratory pour a material, such as plaster, to form a model representing the shape and contours of the soft and hard tissue area of the jaws concerned as well as any remaining natural teeth. Once solidified, this forms a model of the upper and/or lower jaws of the individual patient. The dental technician makes on the model a bite rim out of wax with a wax rim/block on it, positioned to replicate the position of the missing teeth. This is made of solid wax to approximately the correct dimensions but without any anatomical modelling and is sent to the clinician to make various adjustments so as to give information to the technician about facial height, lip support etc, and to mark various anatomical landmarks. This is then returned to the dental laboratory, where the dental technician mounts the model and bite rim on an articulator (an articulator is a hinged metal piece of equipment used to represent the movements of the jaws in the dental laboratory) together with a model of the teeth in the opposing arch.

The dental technician then models in wax the plate that will form the denture itself and teeth are added to it in the functionally and aesthetically correct positions. This wax model with teeth is referred to as a denture try-in. The clinician checks the try-in in the patient's mouth against either the denture or the try-in of the opposing arch or the existing teeth in the opposing arch, with regard to the appearance, phonetics, and function. Adjustments are made by the clinician where necessary. Once the try-in has been returned to the dental laboratory, the dental technician then finishes any modelling work on the try- in that may be needed in order to get a true representation of the finished denture. The technician then takes the wax denture with teeth attached and invests it into plaster contained in a metal flask, taking care to put a separator film between the two halves of the flask in order that it may be opened when set. Once set, the dental technician opens the two halves of the flask and, using boiling water, removes the wax from the flask leaving the teeth embedded into one half. The teeth remain in the flask where they are held in position by the plaster and there is hollow space corresponding to where the wax has been removed. An acrylate dough is then packed into the hollow space in the flask, and it is closed tight in a conventional manner and heated to cure the acrylate dough forming the denture base material. Once cured, the plaster is broken away and the denture is cleaned and polished before sending back to the clinician to fit into the patient's mouth.

In recent years, modern technology has been utilised so that one or more of the stages of the traditional denture production process is implemented digitally, in order to reduce the overall processing time.

For example, once an impression of a patient's jaw is taken, it can be scanned into a computer in the dental laboratory. In some cases, the impression may be scanned directly at the chairside and the data transmitted electronically to the dental laboratory. Alternatively, a model may be produced from this impression and may be scanned into a computer either in the laboratory or directly at the chairside. The components of the denture are then positioned digitally, by inputting additional information including measurements of the anatomical features and dimensions of the patient's mouth into the computer, and using specialist software to design the denture. Such a process avoids the laborious steps of physically setting up the teeth and also enables different occlusal schemes to the tried out using the software.

The denture plate is then milled out of wax, leaving space for precisely fitting teeth to be inserted into the wax to form the try-in. As an alternative, both the denture plate and teeth can be milled out of wax. This is then sent to the clinician for checking in the patient's mouth, following which the try- in can be invested into plaster contained in a metal flask, as in the traditional manner described above.

In an alternative shorter process, the step of producing and fitting a try-in is completely omitted, and the denture is produced directly from the digital design by milling the denture plate from prepolymerised plastic, leaving space for the individual teeth to be fixed in with an adhesive, such as an acrylic adhesive material. Alternatively, both the individual teeth themselves as well as the denture base are produced by milling, and the teeth and base are fixed together using adhesives.

Methods have also been developed to take digital impressions of a patient's jaw, so that physical models are not even required. Once these digital impressions have been taken and additional information including measurements of the anatomical features and dimensions of the patient's mouth have been inputted into the computer, the try-in or complete denture may be designed and produced with the aid of computer design software as outlined in the steps above.

For example, US 2013/0326878 describes a method of production of a dental prosthesis involving digital design of the denture base, teeth shape, and occlusion, and production of the complete denture using various automated methods, such as inkjet printing. In this method, the denture base and teeth are produced separately using the automated method, e.g. by using two inkjet printing machines, one with red material (for the gingiva) and one with white material (for the teeth), and then fixed together using an adhesive. Similarly, US 2013/0326878 describes a method of production of a dental prosthesis involving CAD/CAM and rapid manufacturing techniques. The denture base and the teeth are formed from two different coloured materials and using different techniques, which may include three- dimensional printing, and the teeth and base are then bonded together. The separate three-dimensional printing of both a denture base and artificial teeth, which are then assembled to form a denture by adhesion of the teeth to the base is also described in WO 2014/098956, which relates to photo-curable resin compositions that may be used in three-dimensional printing for manufacturing artificial teeth and denture bases.

Other recent developments in methods for producing dentures involve the use of CAD/CAM techniques in certain stages of the process. For example, US 2013/0101962 describes a method of making a denture involving forming two or more cavities within a block of denture base material and filling these with different coloured fluid synthetic tooth materials which are then solidified, and removing part of the denture base material to form the denture base. The shape of the denture may be defined by a digital three-dimensional model. Similarly, US 2014/0234802 describes a method of molding artificial teeth in a denture base material. The denture base disc formed may then be used in a CAD-CAM milling technique. In both these techniques, the artificial teeth are formed together with the denture base.

All of the above methods have one or more disadvantages. For any of the above methods which involve the separate production of the denture base and teeth and adhesive bonding together of the components, the individual teeth need to be fixed into pre-milled spaces in the milled acrylic denture plate. This positioning of the teeth is susceptible to twisting and/or rotation within the spaces, so that the exact position of the individual teeth in the final denture may not be correct, leading to problems in terms of occlusion.

In addition, for any of the above methods which involve the production of the individual teeth by inkjet (three-dimensional) printing or other digital processes, there is a loss in aesthetics, as well as in strength and wear, since the materials used to produce the individual teeth are generally inferior to those that are employed in current manufacturing methods.

For the processes in which a wax try-in is produced following the digital denture design, this try-in still needs to be invested into plaster in the flask as in the traditional denture manufacturing method, so that there is very little reduction in the overall number of processing steps and time taken to produce the complete denture, as compared to purely traditional methods.

Therefore, there remains a need for an improved process for producing a denture which is less time-consuming and more economical than the traditional process, but provides high quality dentures having good aesthetics, high strength, resistance to wear, and in which the positioning of individual teeth can be accurately established. The present invention seeks to design an improved process for producing a denture utilising digital techniques to produce a modified type of denture flask, which is characterised in that it includes a hollow section having a shape and size corresponding to both the denture base and the individual teeth of the denture. Subsequently, individual teeth may be placed within the hollow section of the flask, and finally traditional techniques may be used to form the denture.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a process for producing a denture utilising digital techniques to produce a modified type of denture flask, which is characterised in that it includes a hollow section having a shape and size corresponding to both the denture base and the teeth of the denture. Subsequently, teeth may be placed within the hollow section of the flask, and finally traditional techniques may be used to form the denture.

Preferably, the teeth are individual teeth or the teeth are joined together, optionally wherein they are loosely joined together.

This process provides a number of advantages relative to both the existing traditional techniques for denture production, as well as the recent techniques incorporating digital technologies.

Firstly, the shape of the hollow section in the denture flask allows for the precise positions of the individual teeth relative to the base to be fixed, and avoids the problem of the individual teeth twisting relative to the base as may occur with processes which involve the separate production of the denture base and teeth and adhesive bonding together of the components. Secondly, the process allows for the digital design of the denture that avoids the laborious steps of physically setting up the teeth and also enables different occlusal schemes to the tried out using the software. Thirdly, the process allows for the use of high quality factory- manufactured individual teeth, which generally have better aesthetics, higher strength, and greater wear-resistance than those produced by inkjet (three- dimensional) printing or other digital processes. Fourthly, the process may, if required, eliminate the need for a try-in to be produced, thus reducing the number of processing steps and overall manufacturing time compared with traditional processes.

An additional benefit of the present process is that the exact volume of the part of the hollow section corresponding to the denture base is known, allowing calculation of the exact weight of material required to fill the denture flask and produce the denture base. Therefore the precise amount of material required to produce the denture base can be mixed, thus avoiding wastage and reducing costs.

Another additional benefit of the present process is that the try-in may be produced from either plastic or wax. The teeth on this try-in may then be adjusted in the mouth and the adjusted try-in may be rescanned before producing the denture flask, thus providing a more accurately fitting denture or dentures.

Yet another additional benefit of the present process is that, since the try- in may be produced from either plastic or from wax, the teeth on this try-in may then be trimmed in the mouth and the adjusted try-in may be rescanned before producing the denture flask. Software may combine the original and new scans so that the denture teeth are their pre-trimmed sizes thus enabling the original teeth to be fitted into the digitally produced flask. After manufacture of the denture, the trimming of the same teeth that had been carried out on the try-in can be carried out by milling the denture teeth using the data from the rescanned try-in, thus providing a more accurately fitting denture or dentures.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows one half of the flask with the hollow section of the denture flask with the teeth in position.

Figure 2 shows the second half of the flask that provides the shape of the denture that fits to the patient's gum. Figure 3 shows the half of the flask as depicted in Figure 1 with one potential position where hard stops might be applied if required (outer dashed and dotted line) and one potential position for the sealing means formed from a soft or flexible material (inner dashed line).

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a process for producing a denture utilising digital techniques to produce a modified type of denture flask, which is characterised in that it includes a hollow section having a shape and size corresponding to both the denture base and the individual teeth of the denture. Subsequently, individual teeth may be placed into those positions in the hollow section of the flask corresponding to their sizes and shapes, and finally both traditional and digital techniques may be used to form the denture. The following definitions shall apply throughout the specification and the appended claims.

Within the context of the present specification, the term "comprises" is taken to mean "includes" or "contains", i.e. other integers or features may be present, whereas the term "consists of" is taken to mean "consists exclusively of".

Within the present specification, the term "about" means plus or minus 20%; more preferably plus or minus 10%; even more preferably plus or minus 5%; most preferably plus or minus 2%.

Within the present specification, the term "denture" means a prosthetic device constructed to replace missing teeth; a denture consists of a denture base that is supported by the soft and hard tissues of the oral cavity, and artificial denture teeth that restore aesthetics and function for a patient.

In the process of the present invention, digital techniques are used to produce the modified type of denture flask. In one embodiment, the digital techniques used to produce the modified type of denture flask comprise an initial step of using denture design software to digitally design the denture. Typically, the denture design software will be used to firstly digitally position individual teeth relative to the digital model of the jaw after which the denture base is itself digitally designed to fit the digital model of the jaw and the denture teeth themselves to provide for an appropriate occlusion and aesthetics.

The data used by the denture design software may be obtained using any appropriate method. In one embodiment, the data of the patient's jaws is obtained by taking impressions. In another embodiment, the data of the patient's jaws is obtained by scanning. In yet another embodiment, a three dimensional facial image is obtained by photographic and/or scanning means. For example, three- dimensional laser or optical scanning either of the patient's jaws directly or models thereof may be used to obtain the necessary data of the patient's jaws. According to the process of the invention, the digital techniques used to produce the modified type of denture flask may comprise any known method for fabricating the flask. Preferably, the modified denture flask is fabricated using one or more methods selected from cutting technology, milling technology, stereolithography, selective laser melting, selective laser sintering, fused deposition modelling, and three-dimensional printing.

In a preferred embodiment, the digital techniques used to produce the modified denture flask comprise three-dimensional printing of the flask. Whereas other processes for the production of dentures using digital techniques may use three-dimensional printing methods to directly produce a denture base and/or individual teeth, the present inventor has developed a novel process in which a modified denture flask is produced using a digital technique, such as three-dimensional printing. A number of different materials may be used in the step of three-dimensional printing of the modified denture flask. Preferably, the material used to produce the modified denture flask by three-dimensional printing should be a material that does not stick to or adversely react with the material that is to be used to form the denture base. However, even if the material used to produce the modified denture flask and the material that is to be used to form the denture base are not compatible, i.e. the two materials stick to or react together, it is possible to use the flask to produce the denture base in the chosen material if a separator is used. In the traditional process for forming a denture base, it is necessary to use a separator between the plaster and the usual acrylic denture base material.

Preferably, the material used to produce the modified denture flask by three- dimensional printing is a plastics material. Such materials tend to be relatively low cost and tend to produce the optimum results in three-dimensional printing. For example, the material may be a thermoplastic plastics material or a thermosetting plastics material. In another embodiment, a combination of materials may be used to produce the modified denture flask. Preferably, this combination of materials comprises a plastics material together with one or more additional materials, such as a filler.

In one preferred embodiment, the material used to produce the modified denture flask by three-dimensional printing is a thermoplastic material, such as nylon. Nylon is particularly preferred because it is compatible with the use of an acrylate or methacrylate denture base material, which are the most commonly used materials for fabricating the denture base, without the use of a separator. In another preferred embodiment, the material used to produce the modified denture flask by three-dimensional printing is a thermosetting plastics material, such as an epoxy resin, a polyurethane, melamine, a polyester, an acrylate, or a methacrylate. In a particularly preferred embodiment, the material is an acrylate or a methacrylate. In the context of this specification, an acrylate monomer may be any suitable derivative of acrylic acid and a methacrylate monomer may be any suitable derivative of methacrylic acid, with ester derivatives of acrylic acid or methacrylic acid, such as a methyl acrylate, ethyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate being particularly suitable. Acrylates or methacrylates are particularly preferred because they are compatible with the use of nylon as the denture base material, without the use of a separator. In some cases, nylon or another suitable thermoplastic material is used for fabricating the denture base, usually by injecting the nylon or other thermoplastic material into the denture flask.

In a further preferred embodiment, two or more materials may be used to produce the modified denture flask by three-dimensional printing. In this embodiment, a first material may be used to produce a thin inner layer of the modified denture flask. This inner layer is the layer that would be in direct contact with the material being used to form the denture base in the subsequent steps of the process of the invention. Accordingly, the first material should preferably be a material that does not stick to or adversely react with the material that is to be used to form the denture base. Therefore, the first material is preferably either nylon or another suitable thermoplastic material, or an acrylate or a methacrylate. In this embodiment, one or more additional materials may be used to produce the remainder of the modified denture flask. For example, the additional materials may comprise one or more backing materials with or without a filler. These additional materials should ideally be low-cost materials and be rigid so as to support and strengthen the first material. Since these additional materials would not come into contact with the material that is to be used to form the denture base, the issue of compatibility does not arise, and therefore there is no restriction on the type of material used, since if this material does not chemically adhere to the inner material then the assembly can be designed so that there is a physical lock between them. It is not essential that this/these additional materials should be produced by three- dimensional printing.

The modified denture flask preferably comprises two portions. The two portions are preferably of approximately equal sizes. Typically, the two portions of the flask will be referred to as the upper portion and the lower portion. The actual external shape and design of the modified denture flask may be varied according to preference, but should ensure precise positioning together of the two portions of the flask. In addition, the modified denture flask preferably includes means to prevent under closure or over closure of the two portions of the flask. In one preferred embodiment of the invention, the two portions of the modified denture flask comprise one or more positive stops which prevent under closure or over closure of the two portions of the flask. The positive stops are preferably formed from a rigid material. In another preferred embodiment of the invention, the modified denture flask further comprises sealing means on one or both portions of the flask. The sealing means is preferably formed from a material that is sufficiently soft or flexible to distort under pressure to form a seal between the two halves of the flask without affecting the positive stops mentioned above. Preferably, the sealing means is provided around the edge of one or both portions of the flask. The provision of the sealing means will allow the two portions of the flask to compress slightly when they are closed together to the positive stops, providing a seal around the flask. This sealing means may be produced by three dimensional printing or else may have been preformed from a material such as a silicone and affixed to the edge of one or both portions of the flask as above.

As noted above, the modified denture flask includes a hollow section having a shape and size corresponding to both the denture base and the individual teeth of the denture. Whereas a traditional denture flask from which the wax that has modelled the denture base has been removed by a means such as boiling water already contains the individual teeth embedded in the plaster and simply has a hollow section corresponding to the denture base the modified denture flask has a hollow section which has individual indentations for accommodating the individual teeth of the denture rather than already containing the denture teeth.

In the process of the present invention, following production of the modified denture flask, the process preferably further comprises a step of placing individual teeth within the hollow section of the flask. Preferably, the individual teeth are slotted into the individual indentations of the hollow section. Since the individual teeth can easily be added to the spaces for them in the modified denture flask and aligned in their correct positions, the problem of twisting/rotation of the teeth relative to the denture base is avoided. It is also possible to use high quality factory-manufactured teeth, in order to avoid the problems of low strength and wear, and poor aesthetics resulting from direct three-dimensional printing or milling of teeth.

The process of the present invention preferably further comprises a step of using traditional techniques to form the denture using the modified denture flask. One preferred technique used to form the denture comprises packing an acrylate or a methacrylate material into the modified denture flask, pressing the halves of the modified denture flask together under pressure, and subsequently curing the acrylate or methacrylate material to polymerise. In this embodiment of the invention, the acrylate or methacrylate material is prepared by mixing the acrylate or methacylate monomer with suitable polymers and/or other reactants directly prior to the packing step. Mixing of the acrylic acid or methacrylic acid monomer with suitable polymers and/or other reactants can be by hand or using a mechanical mixer. The acrylate or methacrylate material may comprise one or more additives, for example, a filler.

Alternatively, a pourable or injectable acrylate or methacrylate material may be used to form the denture base. Accordingly, another technique used to form the denture comprises pouring or injecting an acrylate or methacrylate material into the modified denture flask, and allowing it to self cure or cure by means of heat, light or another suitable method of curing. For instance, if the flask is manufactured from a clear or translucent material, the acrylate or methacrylate material may be cured by means of light. A further technique utilising a pourable acrylic material comprises injecting an acrylate or methacrylate material into the modified denture flask through one or more holes in the flask, and allowing it to polymerise. The pourable acrylate or methacrylate material may comprise one or more additives, for example, a filler. As noted above, nylon or another suitable thermoplastic material may alternatively be used to form the denture base. Therefore, in another embodiment of the invention, the technique used to form the denture comprises injecting nylon or another suitable thermoplastic material into the modified denture flask through one or more holes in the flask, and allowing it to set by cooling. The nylon or other thermoplastic material may comprise one or more additives, for example, a filler.

According to a preferred embodiment of the invention, in which denture design software is used to design the modified denture flask, the amount of material required to produce the denture base is also calculated utilising the denture design software. This has the advantage that the exact amount of material required to create the denture base using the modified denture flask can be determined and mixed up, thus avoiding wastage and reducing costs. In a further embodiment of a process for producing a denture, the denture is milled from a puck, which is preferably of plastics material. Generally the puck is a disc of typically pink plastics and it is generally about 100mm in diameter and about 25mm deep. Instead of milling the puck to form a top side of a denture (on which teeth are attached) and milling the base of the puck to form a fitting surface, according to the invention, a teeth facing surface of a denture is produced in a first stage and a fitting surface, which faces away from the teeth, is produced in a separate stage of the process.

Preferably, software is used to produce a flask which is as previously described for the top side of the denture but the base of the denture is left in the shape of a disc so that it can be fitted into a milling machine. Accordingly, instead of producing a finished denture in a single step in a modified denture flask as previously described, the denture is initially formed on only its teeth facing surface and instead of producing a final fitting surface at this stage, the denture has a base in the form of a disc which fits into a milling machine. This provides the advantage that a clinician may, at the denture try in stage (with the try in material in wax or plastic), grind down the teeth and especially the cusps so that they fit together better for an individual patient. The revised try in is then scanned and used as the basis for the top side of the denture with the base of the denture in the form of a disc which fits into a milling machine.

The denture, with only the teeth facing surface finished, is fitted into the milling machine. The sides of the puck are held by the milling machine and the denture teeth are milled down to correspond to the scan of the revised try in.

The base of the denture is then milled from the puck to provide a fitting surface which corresponds with a scanned fitting surface.

The finished denture is cut away from the sides of the puck.

Embodiments have been described herein in a concise way. It should be appreciated that features of these embodiments may be variously separated or combined within the invention.

Claims

1. A process for producing a denture comprising a denture base and teeth, wherein the process comprises the steps of (i) producing a modified denture flask utilising one or more digital techniques, the flask comprising a hollow section having a shape and size corresponding to both the denture base and the teeth of the denture, (ii) placing teeth within the hollow section of the flask, and (iii) forming the denture.

2. The process of claim 1, wherein the teeth are individual teeth or the teeth are joined together, optionally wherein they are loosely joined together.

3. The process of claim 1 or 2, wherein the step of producing the modified denture flask includes an initial step of using denture design software to digitally design the denture.

4. The process of claim 3, wherein the denture design software is used to firstly digitally position individual teeth relative to the digital model of the jaw after which the denture base is itself digitally designed to fit the digital model of the jaw and the denture teeth themselves to provide for an appropriate occlusion and aesthetics.

5. The process of claim 3 or claim 4, wherein the denture design software utilises data obtained by a method selected from taking impressions, or scanning, optionally wherein the scanning is three-dimensional laser scanning or optical scanning.

6. The process of any of claims 1 to 5, wherein the step of producing the modified type of denture flask comprises fabricating the flask using one or more methods selected from cutting technology, milling technology, stereolithography, selective laser melting, selective laser sintering, fused deposition modelling, and three-dimensional printing.

7. The process of any of claims 1 to 6, wherein the step of producing the modified denture flask comprises three-dimensional printing of the flask.

8. The process of any of claims 1 to 7, wherein the three-dimensional printing of the modified denture flask utilises one or more materials selected from a plastics material, a thermoplastic material such as nylon, or an ester of acrylic acid or methacrylic acid, such as an acrylate or a methacrylate.

9. The process of any of claims 1 to 8, wherein the modified denture flask produced in step (i) of the process comprises an upper portion and a lower portion.

10. The process of claim 9, wherein the modified denture flask produced in step (i) of the process includes means to prevent under closure or over closure of the upper portion and lower portion of the flask.

11. The process of claim 9 or claim 10, wherein the upper portion and/or the lower portion of the modified denture flask produced in step (i) of the process comprise one or more positive stops which prevent under closure or over closure of the portions of the flask, optionally wherein the positive stops are formed from a rigid material.

12. The process of any of claims 9 to 11, wherein the modified denture flask produced in step (i) of the process further comprises sealing means on the upper portion and/or the lower portion of the flask.

13. The process of claim 12, wherein the sealing means is formed from a material that is sufficiently soft or flexible to distort under pressure to form a seal between the upper portion and lower portion of the flask, optionally wherein the sealing means is provided around the edge of the upper portion and/or the lower portion of the flask.

14. The process of any of claims 1 to 13, wherein the step of forming the denture comprises packing an acrylate or methacrylate material as a dough or pourable phase into the modified denture flask, pressing the upper portion and lower portion of the modified denture flask together under pressure, and subsequently curing the material.

15. The process of claim 14, wherein the acrylate or methacrylate material is prepared by mixing the acrylate or methacrylate monomer with other reactants directly prior to the packing step.

16. The process of any of claims 1 to 13, wherein the step of forming the denture comprises pouring an acrylate or methacrylate material into the modified denture flask, and allowing it to self cure or cure by means of heat, light or another suitable method of curing.

17. The process of any of claims 1 to 13, wherein the step of forming the denture comprises injecting an acrylate or methacrylate material into the modified denture flask through one or more holes in the flask, and allowing it to polymerise.

18. The process of any of claims 1 to 13, wherein the step of forming the denture comprises injecting nylon or another suitable thermoplastic material into the modified denture flask through one or more holes in the flask, and allowing it to set by cooling.