WO2020065305A1

WO2020065305A1 - Method for producing a denture

Info

Publication number: WO2020065305A1
Application number: PCT/GB2019/052699
Authority: WO
Inventors: Brian SCHOTTLANDER
Original assignee: Davis, Schottlander & Davis Ltd
Priority date: 2018-09-25
Filing date: 2019-09-25
Publication date: 2020-04-02
Also published as: GB201815621D0; GB201821098D0

Abstract

A method for producing a denture comprises the steps of aligning one or more teeth with a denture plate, wherein the denture plate has a first surface for receiving one or more teeth and a second surface facing away from the first surface, the denture plate defining at least one channel therethrough between the first and second surfaces, applying adhesive through the channel(s) from the second surface, thereby bonding the teeth to the denture plate.

Description

METHOD FOR PRODUCING A DENTURE

FIELD OF THE INVENTION

The present invention relates to a new method for producing a denture using digital and milling techniques. Novel techniques for positioning and fixing teeth into a denture plate, modifying the teeth for an individual patient and of fixing the teeth into the denture plate are described together with novel techniques for manufacturing the denture plate in order to achieve the above either by milling the denture plate from a plastic puck or 3D printing it in order to achieve the above.

BACKGROUND OF THE INVENTION

Dentures are prosthetic devices constructed to replace missing teeth. 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. Generally, they are supported by the surrounding soft and hard tissues of the oral cavity. Complete dentures can also be implant supported, whereby the denture attaches to one or more dental implants fitted into the alveolar bone of the mandible or maxilla (lower or upper jaw). 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 may make custom made special trays with which the clinician takes secondary impressions for greater accuracy and if so the dental technician will pour second models. Alternatively the models in either case may be made by digital means including 3D printing.

The dental technician then constructs on the models of the upper and lower jaw a bite rim/block out of wax, positioned to replicate the position of the missing teeth and including the extant teeth . These are made of solid wax with the extant teeth in the plaster to approximate or record approximately the correct dimensions but without any anatomical modelling. They are then sent to the clinician to make various adjustments so as to give information to the technician about facial height, anterior tooth position, lip support, occlusal plane etc., and to mark various anatomical landmarks. These are then returned to the dental laboratory, where the dental technician mounts the models and bite rims 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 if these are still extant.

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 plate 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, modem technology has been utilised so that one or more of the stages of the traditional denture production method is implemented digitally, in order to reduce the overall method time.

For example, once an impression of a patient's mouth or patient's jaw is taken, it can be scanned and recorded in a digital form for example on a device such as 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 and recorded in a digital form for example on a device such as 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 a device such as a computer, and using specialist software to design the denture electronically. Such a method avoids the laborious steps of physically setting up the teeth and also enables different occlusal schemes to the tried out virtually using the software.

The denture plate is then milled out of wax or other material, 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 together out of wax or other material. This is then sent to a 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 method, the step of producing and fitting a try-in is completely omitted. In either case the denture is produced directly from the digital design by milling the finished denture plate from prepolymerised plastic or 3D printing, 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 plate are produced by milling or 3D printing, and the teeth and base are fixed together using adhesive. As an alternative, both the denture plate and teeth can be milled together out of tooth coloured acrylic or 3D printed using tooth coloured material and the denture plate itself can be stained or painted pink.

In addition to the traditional methods of taking impressions of the contours of the mouth using impression material, methods have also been developed to take digital impressions of a patient's jaw, so that physical models are not even required. Together with these methods for taking impressions of the mouth additional information including recording the occlusal plane, the lip line, the position of the front teeth, other measurements of the anatomical features and dimensions of the patient's mouth must be input into the computer.

However the procedures to carry this out can be very laborious. For instance, Dentca Inc. in US8998615 claims a method of obtaining a gum impression of a patient's mouth and measuring jaw relations, a dental impression tray assembly including a lower tray and an upper tray to fabricate a denture, is used. The lower tray includes a first piece and a pair of second pieces and the upper tray includes a third piece and fourth piece. The method includes inserting the lower tray loaded with an impression material into the mouth to take an impression; taking out the lower tray from the mouth and cutting the impression material along a borderline between the first piece and the pair of second pieces; separating the first piece from the pair of second pieces; attaching an intra-oral tracer to the first piece and inserting the first piece, to which the intra-oral tracer is attached, and the third piece into the mouth to measure the jaw relations.

The try-in or finished 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 plate, teeth shape, and occlusion, and production of the complete denture using various automated methods, such as inkjet printing. In this method, the denture plate 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 plate 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 plate 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 plates.

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

All the above methods have one or more disadvantages. For any of the above methods which involve the separate production of the denture plate and teeth and adhesive bonding together of the components, the individual teeth need to be fixed into pre-milled or 3D printed spaces in the milled acrylic or 3D printed 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 or appearance. In addition, the teeth are fixed into the spaces prepared for them by coating the teeth with an adhesive and/or introducing the adhesive into the prepared spaces. By using this method either there is too little adhesive in which case there will be spaces left round the junction of the teeth and the denture plate in which food can gather and lead to potential growth of bacteria a potential source of infection and halitosisor else too much adhesive is expelled when the teeth are inserted leading to a lengthy method of removing this excess from teeth and denture plate.

In addition, if any basal reduction of the teeth is needed to correct the tooth length for the individual patient or if at the try-in stage, any adjustments are made to the occlusal or incisal surfaces of the teeth such as cusp removal then in current manufacturing methods these adjustments have to be made to the teeth, that must have been mounted into some form of jig to hold them as a separate method before incorporating them into the denture plate which is a costly and time consuming additional step.

In addition, for any of the above methods which involve the production of the individual teeth by inkjet (three-dimensional) printing or other digital methods, 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 methods in which a wax try-in is produced following the digital denture design, this try-in may still need 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 method steps and time taken to produce the complete denture, as compared to purely traditional methods.

Therefore, there remains a need for an improved method for producing a denture which is less time-consuming and more economical than the traditional method, 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 provide an improved method for producing a denture using digital techniques.

SUMMARY OF THE INVENTION

In first aspect, the invention provides a method for producing a denture, which comprises the steps of aligning one or more teeth with a denture plate, wherein the denture plate has a first surface for receiving one or more teeth and a second surface facing away from the first surface, the denture plate defining at least one channel therethrough between the first and second surfaces, and applying adhesive through the channel(s) from the second surface, thereby bonding the teeth to the denture plate.

Preferably, the at least one channel has a diameter of about 0.2mm to about 4.0mm. More preferably, the at least one channel has a diameter of about 2.0mm to about 3.0mm. Even more preferably, the at least one channel has a diameter of about 3.0mm, Preferably, the at least one channel is aligned with a basal side of one or more teeth.

Preferably, the number of channels corresponds at least to the number of teeth. In this regard, preferably there are the same number of teeth as the number of channels. Alternatively, preferably two or more channels are provided corresponding to at least one of the teeth. Advantageously, it has been found that this results in a strong bond between the teeth and the denture plate being provided by the adhesive.

Preferably, at least one preformed space for receiving a tooth is formed in the first surface of the denture plate. More preferably, a plurality of preformed spaces for receiving teeth is formed in the first surface of the denture plate. Preferably, each preformed space is for receiving one tooth. In this regard, each preformed space preferably forms a socket for receiving a tooth. In addition, preferably, each channel adjoins the base of a preformed space.

Preferably, a trough is formed in the second surface of the denture plate. Preferably, the at least one channel through the denture plate adjoins in the trough. In this regard, preferably, the trough has a U shape. Preferably, the channel adjoins the trough at the base of the trough. Preferably, the trough has a depth of about 0.25mm to about 30mm from the second surface of the denture plate. More preferably, the trough has a depth of about 0.25mm to about 20mm from the second surface of the denture plate.

Preferably, the length of a channel between the base of the trough and a preformed space is about 2mm to about 15mm. More preferably, the length of a channel between the base of the trough and a preformed space is about 5mm to about 10mm.

In one embodiment, the denture plate is milled from a puck. In this regard, preferably, the trough is formed by milling the second surface.

Preferably, the second surface is formed by milling the puck so that the plate has a thickness about 1mm to about 15mm, more preferably about 1mm to about 10mm, most preferably about 2mm to about 10mm, thicker than the thickness of the finished denture plate and preferably a step of milling the puck further to form the second surface is carried out subsequently. In this regard, the second surface of the denture plate is preferably formed by milling in more than one stage. In a first stage of milling, the puck is milled to a depth about 1mm to about 15mm, more preferably about 1mm to about 10mm, most preferably about 2mm to about 10mm less than the total depth required to be milled from the puck to form the second surface of the denture plate. Preferably, a second stage of milling is carried out subsequently in order to form the denture plate.

Alternatively, in a second embodiment, the denture plate is 3d printed. In this regard, the trough is 3d printed into the denture plate.

Preferably the adhesive is dental acrylic. More preferably, the adhesive is fluid dental acrylic. Preferably, the adhesive is a pourable or repair acrylic so that a strong and durable chemical bond between denture plate, teeth and adhesive is obtained. In addition, advantageously, compared to known methods of manufacture of dentures, the bond formed between the denture plate and the teeth will fill a higher proportion of the space between the teeth and the denture plate and forms a durable and long lasting bond.

Preferably, the teeth are aligned by inserting them into a template and then aligning the teeth in the template with the denture plate.

Preferably, the template is formed by vacuum or pressure forming. Alternatively, the template is formed by three dimensional (3D) printing. In one embodiment the 3D printing is carried out by a 3D printer which receives computer readable instructions stored on computer readable media. This provides the advantage that individual teeth can be fixed into the preformed spaces, without the risk of individual teeth twisting or rotating.

In one embodiment, after a denture has been designed digitally, a try-in is produced according to the design and the template is formed over the try-in. In an alternative embodiment, a 3d printed model of the denture is produced according to the design and the template is formed over the 3d printed model of the denture.

Preferably, the method comprises the steps of allowing the adhesive to cure, before the template is removed and preferably thereafter removing any excess adhesive from around the teeth. Preferably, the second stage of milling to form the second surface of the denture plate is carried out after allowing the adhesive to cure. Preferably, it is carried out after the adhesive has cured. Preferably, in this second stage of milling, a depth of about 1mm to about 15mm, more preferably about 1mm to about 10mm, most preferably about 2mm to about 10mm is removed from the puck in order to form the second surface of the denture plate. In this regard, preferably, the method comprises the step of milling the second surface to fit the mouth of a patient. Preferably, this step includes trimming the basal excess of teeth that are too long to fit the spaces available for an individual patient and so would protrude through the fitting surface at the same time as milling the fit side of the denture.

Preferably, the method includes a try-in step. Preferably, the try-in is of wax, acrylate or other suitable material that remains stable at mouth temperature. Preferably, the try-in step includes milling the try-in without a basal excess of teeth, As an alternative, in the event that the try-in is 3D printed it is printed without the above mentioned basal excesses of teeth.

Preferably, the denture is a full denture, partial denture or implant stabilised denture.

In one embodiment the denture is a full denture and the denture plate is manufactured of an acrylic. More preferably, the denture plate is manufactured of polymethyi methacrylate (PMMA).

In another embodiment, the denture is a partial denture and the denture plate is manufactured of a material selected from an acrylic, aryl ketone polymer, polyether ether ketone, polyetherketoneketone or similar.

In a further embodiment, the denture is an implant stabilised denture and the denture plate is milled to provide a surface for fixing a dental implant abutment.

In a second aspect, the invention provides a system comprising software for 3d printing or for milling a dental puck to form a denture plate having a first surface for receiving one or more teeth and a second surface facing away from the first surface, the software including computer readable instructions for production of a trough in the second surface or the denture plate and optionally at least one channel between the first and second surfaces of the denture plate Preferably, the system includes a mill, or 3d printer, or a mill and a 3d printer, for production of the trough and the at least one channel.

Preferably, the trough has a depth of about 0.25 to about 30mm from the second surface of the denture plate. More preferably, the trough has a depth of about 0.25 to about 20mm from the second surface of the denture plate.

Preferably, the at least one channel has a diameter of about 0.2mm to about 4.0mm. More preferably, the at least one channel has a diameter of about 0.2mm to about 3.0mm.

Preferably, the system comprises software for carrying out a method as described herein. Preferably, the software includes computer readable instructions for production of a denture plate or a denture as described herein.

Advantageously, the invention provides a method of applying digital techniques in an economical manner to the production of a denture.

BRIEF DESCRIPTION OF THE FIGURES

The invention will now be described with reference to the accompanying drawings, wherein:

Figure 1 shows a puck typically made of Polymethyl Methacrylate (PMMA). Other acrylates or suitable plastic materials safe for use in the mouth may also be used.

Figure 2 shows a side of the puck of Figure 1, which will become the first (polished) surface of a denture plate having been milled ready for insertion of the teeth.

Figure 3 shows a trough on the reverse side (second side) of the puck of Figure 2 being the fitting side of a denture plate which also has channels drilled through it.

Figure 4 shows a fitting side of a denture plate. The denture plate has been milled from a puck and support struts remain between the denture plate and a remaining a radially outer annular ring of the puck. Figure 5 shows the spaces for teeth and channels drilled through the denture plate viewed from the side which will become the first (polished) surface.

Figure 6 shows teeth in a template.

Figure 7 shows teeth still in the template but inserted in the spaces in the denture plate. Figure 8 shows minimal excess adhesive escaped through sides of the teeth.

Figure 9 shows a denture held by support struts to be removed later.

Figures 10 and 11 show finished dentures.

Figure 12 shows the results of tests on the amount of adhesive flowing from the second surface of the denture plate through channels having diameters of 2mm, 2.5mm, 3mm and 4mm when no trough is provided in the second surface.

Figure 13 shows the results of tests on the amount of adhesive flowing from the second surface of the denture plate through channels having diameters of 2mm, 2.5mm and 3mm when a trough is provided in the second surface of the denture plate. The channels have a length of 15mm from the base of the trough to the base of each socket.

Figure 14 shows the results of tests on the amount of adhesive flowing from the second surface of the denture plate through channels having diameters of 2mm, 2.5mm and 3mm when a trough is provided in the second surface of the denture plate. The channels have a length of 10mm from the base of the trough to the base of each socket.

Figure 15 shows the results of tests on the amount of adhesive flowing from the second surface of the denture plate through a channel having a diameter of 3mm. The channel had a length of 10mm from the base of the trough to the base of the socket. In this case, only one channel was provided and no channel was provided to the sockets on either side to determine the effect of not providing a channel for each socket.

Figure 16 shows the results of tests when a channel is provided for each socket and adhesive is applied through each channel (i.e. to show that a channel is needed connecting the second surface of the denture plate to each tooth). As above the channels had a length of 10mm from the base of the trough to the base of the socket and channels were of 3mm diameter.

DETAILED DESCRIPTION OF THE INVENTION

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 plate 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.

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.

In the method of the present invention, digital techniques are used to produce a denture (10). In one embodiment, the digital techniques used comprise a step of using denture design software to digitally design the denture virtually. Typically, the denture design software will be used to firstly digitally position individual teeth relative to a digital model of the jaw after which the denture plate 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. With reference to Figures 1 to 11 of the accompanying drawings, in the method after the design stages a trial denture is preferably produced made of wax, resin or other suitable material and, as shown in Figure 6, a template (8) is manufactured over it using a thin sheet of formable material such as ethylene vinyl acetate which is vacuum, or pressure formed.

As an alternative, the above template (8) may be manufactured using an impression materia! although this is a less preferred method.

Once the template (8) has been manufactured, the trial denture is preferably sent to the clinician to try in the mouth and any adjustments that are required to the occlusal or incisal surfaces of the teeth (7) such as cusp removal are carried out in which case this surface of the denture is re-scanned and combined with the original images in the design software.

In an alternative shorter method, the trial denture is not sent to the clinician and this step is omitted.

If the clinician wishes to move the position of any of the teeth (7), this can be carried out by their doing so at this stage. In such a case, either the model can be rescanned and the changes imported into the design software so that the new positions can be compared with the previous ones and alterations made automatically, or the change can be made in the software by visually comparing the altered try-in with the original design virtually.

As shown in Figures 1 and 9, the denture plate (2) is milled out of a plastic puck (1). The puck (1) is typically made of PM A.

As shown in Figure 2, in this invention only the first surface (3) of the denture (10) which is the polished surface that will contain the teeth (7) is first fully milled and the reverse surface (4) shown in Figure 3, which is the fitting surface, is only milled to form a trough (5) or similar between about 0.25mm and about 30mm from the fit surface (4) of the denture.

As shown in Figure 3, channels (6) of diameter about 0.2mm to about 3.0mm are formed in the trough (5) e.g. by milling in a milling machine or by a dental technician drilling by hand. The channels (6) preferably lead through to the base of the teeth (7) when the teeth (7) are in position. In an alternative embodiment, the trough (5) is not formed and only the channels (6) are formed, e.g. by drilling.

As shown in Figure 4, a fitting side (4) of a denture plate (2) is milled from a puck and support struts (9) remain between the denture plate (2) and a radially outer annular ring (13) of the puck (1). The support struts (9) are removed later by milling to separate the denture plate (2) from the radially outer annular ring (13) of the puck (1).

In one embodiment, the second surface (4) is formed by milling the puck (1) so that it has a thickness about 2mm to about 10mm, thicker than the thickness of the finished denture plate (2) and preferably a step of milling the puck (1) further to form the second surface (4) is carried out subsequently. In this regard, the second surface (4) of the denture plate (2) is formed by milling in more than one stage. In a first stage of milling, the puck (1) is milled about 2mm to about 10mm less than the total depth required to be milled from the puck (1) to form the second surface (4) of the denture plate (2). A second stage of milling is carried out subsequently in order to form the denture plate (2).

In an alternative method the denture plate (2) is 3D printed using an acrylic ester or other suitable 3D printable material supplied for this application. In this method channels (6) having a diameter of about 0.2mm to about 3.0mm are 3D printed on the fitting surface (4) of the denture (10) leading through to all or some of the bases of the teeth (7) and these may be joined to a trough (5) formed by 3D printing or other means.

As shown in Figures 5 and 6, the teeth (7) are inserted into the previously manufactured template (8) so that they may be positioned as a block into the pre-milled or printed spaces (11) in the denture plate (2) thus avoiding the previous problem of individual teeth (7) twisting or rotating within the spaces (11).

As shown in Figures 7 and 8, when the teeth (7) have been securely positioned, adhesive which is preferably a fluid acrylic such as a dental pourable acrylic or repair acrylic or any such suitable fluid acrylic mixture is preferably poured into the trough (5) or channels (6) and runs through them to the bases of the teeth (7). The adhesive is then cured to form a solid mass that is chemically bonded to both teeth (7) and denture plate (2). The method has the advantage that especially if a pourable or repair acrylic is used this can be cured in a conventional laboratory pressure pot for instance at a temperature of about 40°C for about 10 minutes at about 3 bars pressure to form a homogeneous mass. Alternatively, an alternative adhesive material may be used in the place of the acrylics described above.

As shown in Figure 8, the adhesive runs up the sides of the teeth (7) to form a substantially perfect bond and seal between the teeth (7) and the denture plate (2) and, once full curing has taken place the template (8) is removed and any excess adhesive (12) can easily be removed from around the teeth (7) since the closely fitting template (8) will have acted as back pressure against excessive outflow of adhesive.

In an embodiment, when a plastic puck (1) has been used as the starting material to manufacture the denture plate (2), it is reinserted into the mill after the teeth (7) have been bonded in position, and the fitting surface (second surface) (4) of the denture is then milled. In this regard, the second stage of milling to form the second surface (4) of the denture plate (2) is carried out after the adhesive has cured. In this second stage of milling, a depth of about 2mm to about 10mm is removed in order to form the second surface (4) of the denture plate (2).

A further advantage of this method is that if the bases of the teeth (7) themselves are too long to fit the spaces available for the individual patient and so would need trimming to stop them protruding through the fitting surface then the milling above would remove any basal excess at the same time as milling the fit side (4) of the denture. In addition, if at the try-in stage any adjustments to the occlusal or incisal surfaces of the teeth (7) such as cusp removal have been carried out by the clinician then this surface of the denture (10) can be the milled once more to copy the adjustment made by the clinician.

Alternatively, if 3D printing has been employed to manufacture the denture plate (2), the channels (6), trough (5) and any basal excess of teeth (7) that protrude through the fitting surface (4) of the denture plate are removed at the same time as the support structures known in the art of 3D printing using a dental bur or disc or other suitable instrument.

As shown in Figures 10 and 11, a finished denture (10) comprises teeth (7) bonded to a denture plate (2). COMPARATIVE TEST DATA

Comparative testing was carried out to determine the effectiveness of features of the invention.

In this regard, experimentai tests were carried out to determine;

(a) the affect of a trough in the second surface of a puck on the flow of adhesive around adjoining teeth;

(b) the affect of including a number of channels corrsponding to the number of teeth; and

(c) whether a template to hold teeth in position whilst adhesive is setting should be 3d printed,

In order to carry out the required tests, various denture plates were produced. Teeth were inserted into preformed spaces providing sockets in the first surface of the denture plates and adhesive was applied to the second surface. The amount of adhesive flowing around the teeth was photographed and measured.

It was found that it was extraordinarily difficult to take photographs of teeth where the adhesive had been applied to them in the sockets. This is because once the adhesive had set, it was not possible to remove the teeth from the sockets. Even when a separator was used and teeth were taken out of the sockets whilst the adhesive was still unset it was very difficult to see where the adhesive had been applied to the tooth. In light of this, it was concluded that the best way to show the affect of features of the invention was to remove teeth from their sockets with the adhesive still unset and then photograph the bases of the teeth showing the level of adhesive just on the bases. This is of course not the same as determining how much adhesive penetration is achieved up the side of a tooth, but it was determined that the teste used would be adequate to show the effectiveness of features of the invention, because if the adhesive does not travel in sufficient quantity through the channel and on to the base of a tooth then it would not be possible in any event for adhesive to flow up the sides of the teeth.

The data obtained is shown in Figures 12 to 16, Figure 12 shows the amount of adhesive that flowed from the second surface of a denture plate through channels having diameters of 2mm, 2.5mm, 3mm and 4mm when no trough was provided in the second surface.

At all channel diameters except 4mm the adhesive did not flow as far as the bases of the teeth themselves. At 4mm there was just a hint that some adhesive had flowed through. The amount of adhesive contact was determined to be about 3%.

Figure 13 shows the amount of adhesive that flowed from the second surface of the denture plate through channels having diameters of 2mm, 2.5mm and 3mm when a trough was provided in the second surface of the denture plate. The channels had a length of 15mm from the base of the trough to the base of each socket.

There was some adhesive contact at 2mm and 2.5mm which was determined to be about 20% and almost complete contact at 3mm that was determined to be about 85%.

Figure 14 shows the amount of adhesive that flowed from the second surface of the denture plate through channels having diameters of 2mm, 2.5mm and 3mm when a trough was provided in the second surface of the denture plate. The channels had a length of 10mm from the base of the trough to the base of each socket.

There was some adhesive contact at 2mm and 2.5mm which was determined to be about 60% and 75% respectively and almost complete contact at 3mm that was determined to be about 90%.

Figure 15 shows the amount of adhesive that flowed from the second surface of the denture plate through a channel having a diameter of 3mm. The channel had a length of 10mm from the base of the trough to the base of the socket. In this case, only one channel was provided to determine the effect of not providing a channel for each socket.

As can be seen, plenty of adhesive flowed through the channel to the tooth in the socket in which the channel was located. However, no adhesive was present on the teeth in the sockets on either side.

This shows that it is important to include a channel for each socket. Figure 16 shows the results of tests when a channel was provided for each socket and adhesive was applied through each channel (i.e. to show that there should be an equivalent number of channels and teeth and channels are needed connecting the second surface of the denture plate to each tooth). As above the channels had a length of 10mm from the base of the trough to the base of the socket and channels were of 3mm diameter.

As can be seen, there was good coverage on all teeth concerned and this was determined to be about 95% coverage.

ADVANTAGES OF THE INVENTION

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

The invention provides constructional, functional and also very importantly health benefits. In this regard, the risk of a cavity between the teeth and the denture plate is reduced and this assists with good denture hygiene. Denture hygiene is key to a healthy mouth and difficult to clean areas pose a real risk and as many patients are old with eyesight and dexterity problems, the absence of any cavity is a major benefit.

Secondly, the method 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 virtually using software.

Thirdly, the method 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 methods.

Fourthly, the method may, if required, eliminate the need for a try-in to be produced, thus reducing the number of method steps and overall manufacturing time compared with traditional methods. Fifthly, in the method of milling a plastic puck, the method allows for any adjustments that are required to the occlusal or incisal surfaces of the teeth such as cusp removal to be incorporated into the final denture that is produced thus providing a more accurately fitting denture or dentures without having to mill the teeth in a separate operation before fixing them in the denture. In addition, the method of the invention enables the precise positions of the individual teeth relative to the base to be fixed by the template, and avoids the problem of the individual teeth twisting or rotating relative to the base as may occur with methods which involve the production of the denture plate and separate adhesive bonding of individual teeth to the denture plate.

Sixthly, in the method of milling a plastic puck, where the denture teeth are too long for the denture that is required and would therefore need to be trimmed basai!y to avoid them protruding through the fitting surface of the denture the method enables the backs of the teeth to be trimmed as part of the method for milling the fitting surface of the denture thereby avoiding a costly separate method as in other systems.

Although the present invention has been described with respect to a presently preferred embodiment, the present invention should not be limited to the embodiment, and it will be appreciated by those skilled in the art that various modifications may be made without departing from the spirit and scope of the present invention.

Claims

1, A method for producing a denture comprising a denture plate and teeth, wherein the method comprises the steps of aligning one or more teeth with a denture plate, wherein the denture plate has a first surface for receiving one or more teeth and a second surface facing away from the first surface, the denture plate defining at least one channel therethrough between the first and second surfaces, and applying adhesive through the channel(s) from the second surface, thereby bonding the teeth to the denture plate. , The method of claim 1, wherein the at least one channel has a diameter of about 0.2mm to about 4.0mm. , The method of claim 1 or 2, wherein the at least one channel is aligned with a basal side of one or more teeth. , The method of any one of the preceding claims, wherein the number of channels corresponds at least to the number of teeth. , The method of any one of the preceding claims, wherein a trough is formed in the second surface. , The method according to claim 5, wherein the denture plate is milled from a puck and the trough is formed by milling. , The method according to any one of the preceding claims, wherein the second surface is formed by milling a puck in more than one stage and in a first stage the puck is milled to a depth about lmm to about 15mm less than the total depth required to be milled from the puck to form the second surface of the denture plate and a second stage of milling is carried out subsequently in order to form the denture plate. _> The method according to claim 5, wherein the denture plate is 3d printed and the trough is 3d printed into the denture plate. , The method according to any one of claims 5 to 8, wherein the at least one channel through the denture plate adjoins the trough.

10. The method according to any one of claims 5 to 9 , wherein the trough has a depth of about 0.25 to about 30mm from the second surface of the denture plate.

11. The method according to any one of the preceding claims, wherein the adhesive is dental acrylic.

12. The method according to claim 11, wherein the adhesive is fluid dental acrylic.

13. The method according to any one of the preceding claims, wherein the teeth are aligned by inserting them into a template and then aligning the teeth in the template with the denture plate.

14. The method according to claim 13, wherein the template is formed by vacuum or pressure forming, or by 3D printing.

15. The method according to any one of the preceding claims, wherein the method comprises the steps of allowing the adhesive to cure, before removing the template and removing any excess adhesive from around the teeth.

16. The method according to any one of the preceding claims, wherein the method comprises the step of milling the second surface to fit the mouth of a patient.

17. The method according to claim 16 wherein a second stage of milling is carried out to form the second surface of the denture plate.

18. The method according to claim 17 wherein second stage of iliing is carried out after the adhesive has cured.

19. The method according to any one of claims 16 to 18, wherein a depth of about 1mm to about 15mm removed in a second stage of milling in order to form the second surface of the denture plate.

20. The method according to any one of claims 16 to 19, wherein the step of milling includes trimming the basal excess of teeth that are too long to fit the spaces available for an individual patient and so would protrude through the fitting surface at the same time as milling the fit side of the denture.

21. The method according to any one of the preceding claims, wherein the method comprises a try-in step.

22. The method of claim 21 wherein the try-in step comprises the step of testing a try-in of wax, acrylate or other suitable material that remains stable at mouth temperature in the mouth of a patient.

23. The method of claim 21 or 22 wherein the try-in step includes milling the try-in without a basal excess of teeth or, in the event that the try-in is 3D printed, it is printed without a basal excess of teeth.

24. The method of any one of the preceding claims wherein the denture is a full denture, a partial denture, or an implant stabilised denture.

25. The method of claim 24, wherein the denture is a full denture and the denture plate is manufactured of an acrylic.

26. The method of claim 24, wherein the denture is a partial denture and the denture plate is manufactured of a material selected from an acrylic, aryl ketone polymer, polyether ether ketone or polyetherketoneketone.

27 The method of claim 24, wherein the denture is an implant stabilised denture and the denture plate is milled to provide a surface for fixing a dental implant abutment.

28 A system comprising software for 3d printing or for milling a dental puck to form a denture plate having a first surface for receiving one or more teeth and a second surface facing away from the first surface, the software including computer readable instructions for production of a trough in the second surface or the denture plate or for milling to a depth about 1mm to about 15mm less than the total depth required to be milled from the puck to form the second surface of the denture plate and optionally at least one channel between the first and second surfaces of the denture plate.

29. The system according to claim 28, wherein the system includes a mill, or 3D printer, or a mill and a 3D printer, for production of the denture plate having a trough or for milling to a depth about lmm to about 15mm less than the total depth required to be milled from the puck to form the second surface of the denture plate and optionally the at least one channel.

30. The system according to claim 28 or 29, wherein the trough has a depth of about 0.25 to about 30mm from the second surface of the denture plate.

31. The system according to any one of claims 28 to 30, wherein the at feast one channel has a diameter of about 0.2mm to about 3.0mm.