GB2506167A

GB2506167A - Multi-coloured positive tooth models

Info

Publication number: GB2506167A
Application number: GB1216987.6A
Authority: GB
Inventors: Yong-Min Jo
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-09-24
Filing date: 2012-09-24
Publication date: 2014-03-26
Also published as: GB201216987D0

Abstract

A method for manufacturing multi-coloured positive tooth models that are suitable for manufacturing orthodontic appliances by means of pressure moulding or vacuum moulding a sheet of transparent thermoplastic material comprisies a three-dimensional, bi-coloured powder bed inkjet head printing process. For models which remain in place within the mould whilst the appliance is excised from the moulded sheet, printing teeth and gums different colours provide a visible orientation cut line representing the boundary of the appliance and along which the appliance has to be excised from the mould.

Description

Multi-colored denture models The present invention relates to the field of denture models. More particularly, the present invention is directed to denture models for manufacturing orthodontic appliances.

Orthodontic appliances are used for repositioning teeth, for straightening teeth, or for keeping them in their position within the jaw. An orthodontic appliance comprises a polymeric shell having cavities shaped to receive and optionally reposition teeth from one arrangement to a successive arrangement. The polymeric shell will preferably, but not necessarily, fit over all teeth that are present in the upper or lower jaw. For repositioning or straightening teeth, a series of orthodontic appliances may be used to incrementally reposition individual teeth. Successive appliances are worn in a particular sequence, and a given appliance is replaced by a successive appliance when the teeth either approach or have reached the target end position for that stage of treatment.

With respect to the present invention, the terms "orthodontic appliance" and "dental appliance" are used synonymously, and comprise polymeric shells having cavities shaped to receive teeth. Orthodontic appliances for keeping teeth in a given position are commonly referred to as "retainer", whereas orthodontic appliances resiliently repositioning teeth are commonly referred to as "aligner". Usually, no wires or other means will be provided for holding the appliance in place over the teeth.

Usually, an orthodontic appliance is formed from a preferably transparent sheet of a suitable thermoplastic polymer film. The term "thermoplastic" refers to thermosoftening plastics, i. e. polymers that become pliable or moldable above a specific temperature, and return to a solid state upon cooling. Examples of suitable thermoplastic polymerfilms for forming orthodontic appliances are available under the trade names BIOCRYL® "C", 1.5, 2, or 3 mm thick sheets of PMMA, BIOCRYL® "M", or DURAN®+, 0.5, 0.625, 0.75, 1.0, 1.5, or 2.0 mm thick sheets, from SCHEU-DENTAL GmbH, 58642 lserlohn, Germany.

In manufacturing an orthodontic appliance, a positive model of the teeth or a portion of the jaw including the teeth is prepared. Said model is called "positive tooth model" or "denture model". Then the orthodontic appliance is formed from a sheet of the suitable thermoplastic polymer film by using a conventional pressure molding machine or vacuum molding machine. The molding machine forms an orthodontic appliance directly from the positive tooth model and the desired thermoplastic material. After molding, the solidified thermoplastic sheet, i.e. the thermoplastic mold, is removed from the molding machine in conjunction with the positive tooth model. The orthodontic appliance has to be excised from the thermoplastic mold along a line which represents the rim or boundary of the orthodontic appliance. The boundary of the orthodontic appliance determines how far the orthodontic appliance covers the teeth and the gum when it is applied to the patient.

Typically, the positive tooth model is removed from the thermoplastic mold including the orthodontic appliance before the orthodontic appliance is excised from the thermoplastic mold. However, in advanced processes for manufacturing orthodontic appliances, the positive tooth model remains in place, i.e. firmly connected with the thermoplastic mold covering said positive tooth model, while the orthodontic appliance is excised from the thermoplastic mold along a line representing the boundary of the orthodontic appliance.

Thus far, unicolored positive tooth models are used for manufacturing the orthodontic appliances. However, having a transparent thermoplastic mold covering a unicolored positive tooth model makes it is difficult to determine the line along which the orthodontic appliance has to be excised from the thermoplastic mold. Hence, in methods for manufacturing orthodontic appliances, wherein the positive tooth model remains connected to the thermoplastic mold while the orthodontic appliance is excised, it would be advantageous to have a visible orientation providing an aid in excising the orthodontic appliance from the thermoplastic mold.

Therefore, there is a need for multicolored positive tooth models for use in the manufacturing of orthodontic appliances.

Dentures are prosthetic devices comprising artificial teeth within a pink plastic carrier. Hence, dentures can be considered as representing a kind of bicolored positive tooth model, although not intended for manufacturing orthodontic appliances. Typically, dentures are prepared in that the dentist takes an impression of a patient's mouth using a soft, dough like material that is placed within a stock tray, i.e. a carrier made of metal or plastic, and shaped to fit the mouth. The impressions are placed into the mouth one at a time and are allowed to set to a stiff rubbery consistency. The impressions are a negative model of the patient's mouth, and are sent to a dental laboratory. The impressions serve as mold for the positive tooth model in that material made from Plaster of Paris is poured into the impressions.

For constructing dentures, a special dental modeling wax and artificial teeth are used. The wax is softened and each tooth is placed onto the wax, until all the teeth have been placed to their correct position. The wax is then shaped to blend with the existing tissues to try and mimic the natural tissue. When it is assured that the dentures correctly fit into the patient's jaws, the wax portion of the denture is replaced with pink plastic in that a plaster mould of the wax denture is created, the mould is immersed in boiling water to remove the wax, whereby the artificial teeth are held in place in the plaster mould. The space that is left behind from the wax that was removed is filled with pink plastic having dough like consistency. The plastic is cured and thereby hardens. Any excess material is then removed from the denture, and the denture is polished. The resulting denture is a bi-colored prosthetic device.

As can be seen, dentures comprising white teeth and a pink gum are known in orthodontics, but they are laborious and time-consuming to be manufactured. In addition, the plastic mimicking the patient's tissue is not rigid enough to withstand the pressure or vacuum that would be applied in a molding machine if such a denture would be used for manufacturing an orthodontic appliance.

It was therefore an object of the present invention to provide multi-colored positive tooth models which may be used in pressure molding or vacuum molding machines for manufacturing orthodontic appliances. It was another object of the invention to provide a process for manufacturing multi-colored positive tooth models which may be used in pressure molding or vacuum molding machines for manufacturing orthodontic appliances, and which is less laborious and time-consuming than the typical processes for manufacturing dentures.

The object is solved by a method for manufacturing a multi-colored positive tooth model by means of a method comprising three-dimensional printing (3D printing), and by a multi-colored positive tooth model obtained by a method comprising three-dimensional printing.

In a first aspect, the invention provides a method for manufacturing a multi-colored positive tooth model for manufacturing orthodontic appliances.

In a second aspect, the invention provides multi-colored positive tooth models that are obtained by the method according to the first aspect of the invention.

In a third aspect, the invention provides the use of the multicolored positive tooth models according to the second aspect or for manufacturing orthodontic appliances.

In a further aspect, the invention provides a method for manufacturing orthodontic appliances, wherein a multi-colored positive tooth model according to the second aspect or manufactured pursuant to a method according to the first aspect is used in pressure molding or vacuum molding.

The present invention will be described with respect to particular embodiments, but the invention is not limited thereto, but only to the claims.

Where an indefinite or definite article is used when referring to a singular noun, e.g. "a", "an", "the", this includes a plural of that noun unless something else is specifically stated. Furthermore, the terms first, second, third and the like in the description and in the claims are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order.

It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein. Moreover, the terms top, bottom, over, under, beyond and the like in the description and in the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein. It is to be noticed that the term "comprising", used in the present description and claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B. According to the first aspect, the invention provides a method for manufacturing a multi-colored positive tooth model.

The method for manufacturing the multi-colored positive tooth model comprises an inkjet head 3D printing process for preparing a progenitor positive tooth model.

In an embodiment, the method comprises a powder bed inkjet head 3D printing process for preparing a progenitor positive tooth model. In the powder bed inkjet head 3D printing process, an inkjet-like printing head moves across a bed of powder, selectively depositing a liquid binding material, i.e. binder, in the shape of the section or slice of the positive tooth model. A fresh layer of powder is spread across the top of the model, and the process of selectively depositing binder is repeated. When the tooth model is complete, unbound powder is removed.

In an embodiment of the 3D printing process, software virtually cuts a virtual positive tooth model into digital cross sections, creating a two dimensional image for each layer. Each layer has a thickness of about 0.1 mm. A bed of powder is accurately and evenly spread across a build platform by using a feed piston and a platform which can be lowered incrementally for each layer. A roller mechanism spreads the powder fed from the feed piston onto the build platform such that an even, smooth and full layer of densely packed powder per layer results. Once the layer of powder is spread, the inkjet print head(s) print the cross sectional area of the cross section to be printed onto the layer of powder, binding the powder together. This process is repeated for all layers of the positive tooth model to be manufactured. Application of the binder to a given layer binds said layer to the previous layer too.

The powder for 3D printing is based on plaster and contains numerous additives that maximize surface finish, feature resolution, and part strength. Suitable powders are disclosed in WO 1998/009798 Al, and are commercially available from 3DSYSTEMS, Rock Hill, SC, USA.

In an embodiment of the 3D printing process, the thickness of each powder layer is about 0.09 to about 0.1 mm (0.0035 to 0.0004 inches). In another and/or alternative the binder is applied to each powder layer at a resolution of about 600 dpi (dots per inch). The spatial resolution resulting from the layer thickness and the density of binder dots applied to each powder layer permits manufacturing a positive tooth model that is smooth and accurate enough to be used in molding orthodontic appliances such that neither the positive tooth model nor the orthodontic appliance molded by said positive tooth model in a pressure molding or vacuum molding process requires extensive finishing to render the orthodontic appliance tightly and comfortably fitting the patient's teeth.

In the method of the present invention, colored binders are used for 3D printing.

In an embodiment, binders of different color are applied to the powder bed by means of a single inkjet head. Usually, the printing head has channels for different colored binders, typically four different colored binders are used: cyan, magenta, yellow and black. In an alternative embodiment, a plurality of inkjet heads are used, wherein one inkjet head is used for each of the differently colored binders such that a first inkjet head is used for applying a first binder having a first color, a second inkjet head is used for applying a second binder having a second color, a third inkjet head is used for applying a third binder having a third color, and another inkjet head is used for applying a binder having a fourth color. In using colored binders for 3D printing, multicolored positive tooth models can be manufactured.

In an embodiment a bi-colored positive tooth model is manufactured, wherein the portion(s) of the positive tooth model representing the teeth are printed in another color than the portion(s) representing the gum. Preferably, the portion(s) representing the teeth is! are printed in white or whitish, and the portion(s) representing the gums is printed in pink, such that the positive tooth model looks like a full denture.

In an embodiment of the method according to the first aspect, the printed multi-colored progenitor positive tooth model is infiltrated with a curable resin. The progenitor tooth model as obtained from the 3D powder bed inkjet head printing process is friable and would crumble in the course of vacuum molding. To provide a rigid positive tooth model that withstands vacuum molding, the progenitor tooth model is infiltrated with curable resin, preferably with a photocurable resin, and subsequently curing of the resin is effected, preferably by irradiating the progenitor tooth model with UV light. An example of a curable resin is selected from the group consisting of polyacralytes and polymethacrylates.

In an alternative embodiment of the first aspect of the invention, an inkjet head 3D printing process is used for manufacturing the positive tooth models, wherein layers of at least one photopolymer, i.e. a photopolymerizable polymer, are applied to the preceding layer and immediately cured after being applied.

In the printing process according to the alternative embodiment of the first aspect of the invention, an inkjet head moves back and forth along an x-axis, and applies a thin layer of photopolymerizable polymer on the platform or on the previous layer. Each layer of photopolymerizable polymer is cured before the next layer of photopolymerizable polymer is applied by means of ink jet head printing. Preferably, the photopolymerizable polymer is cured by exposing the layer of photopolymerizable polymer to UV-light. In a preferred embodiment of the ink jet head 3D printer, the ink jet head comprises a UV-lamp. Subsequent curing of the printed positive tooth model is not required.

The ink jet head comprises a plurality of jet nozzles. The photopolymerizable polymer is applied through one of more of said nozzles. In addition, a non-photopolymerizable polymer can be applied through other nozzles of the same ink jet head. Said non-photopolymerizable polymer provides a gel like support where no photopolymerizable polymer material shall be deposited. Said non-photopolymerizable polymer can be removed from the printed positive tooth model after printing is complete.

The platform is incrementally lowered for each layer of photopolymerizable polymer and/or non-photopolymerizable polymer to be applied such that layers having a thickness of as little as 16 pm or even a thickness of as little as 8 pm are obtainable.

In using differently colored photopolymerizable polymers in the inkjet head 3D printing process according to the alternative embodiment of the first aspect of the invention, multi-colored positive tooth models can be produced.

In an embodiment the portion(s) of the positive tooth model representing the teeth is/are printed in another color than the portion(s) representing the gum.

According to the second aspect, the invention provides multi-colored positive tooth models which are obtainable by a method according to the first aspect, i.e. a 3D powder bed inkjet head printing process, wherein said multi-colored positive tooth models are suitable for manufacturing orthodontic appliances by means of pressure molding or vacuum molding of a sheet of thermoplastic material.

The positive tooth model resulting from the method according to the first aspect is multicolored and rigid such that it is suitable for being used in a process for manufacturing orthodontic appliances by means of vacuum molding or pressure molding.

In an embodiment, the positive tooth model comprises at least two different colors. In another and/or additional embodiment, the portion(s) of the positive tooth model representing the teeth have a different color than the portion(s) representing the gum. In a preferred embodiment, the portion(s) of the positive tooth model representing the teeth has/have a white color or is/are whitish, whereas and the portion(s) representing the gums are pink, such that the positive tooth model looks like a full denture.

The multi-colored positive tooth model is not only more appealing, but provides substantial technical advantages in that is much easier to distinguish between the portions representing the teeth and the portion representing the gum in a multi-colored positive tooth model wherein the portion representing the teeth and the portion representing the gum have different colors. Using such a -at least bi-colored -positive tooth model in manufacturing orthodontic appliances makes it easier to determine the boundary of the orthodontic appliance along which said orthodontic appliance has to be excised from the thermoplastic mold.

According to the third aspect, the invention provides the use of a multi-colored positive tooth model. Use of positive tooth model as described herein above, or manufactured according to the method described herein above for manufacturing orthodontic appliances is advantageous, because the multi-colored positive tooth model is easy and convenient to manufacture, and its multiple colors facilitates excision of orthodontic appliance from the thermoplastic mold, because a multicolored positive tooth model, wherein the portion(s) representing the teeth has/have a different color than the portion(s) representing the gum renders it much easier to identify the boundary of the orthodontic appliance within the thermoplastic mold if the positive tooth model is still attached to the thermoplastic mold.

According to a further aspect, the invention provides a method for manufacturing orthodontic appliances, wherein a multi-colored positive tooth model according to the second aspect or manufactured pursuant to a method according to the first aspect is used in pressure molding or vacuum molding.

In an embodiment of the method for manufacturing an orthodontic appliance, the multicolored positive tooth model remains connected to the thermoplastic mold, while the orthodontic appliance is excised from the thermoplastic mold.

Claims

CLAIMS1. A method for manufacturing a multi-colored positive tooth model suitable for manufacturing an orthodontic appliance, the method comprising the step of three-dimensional printing a multi-colored progenitor tooth model in an inkjet head printing process.
2. The method according to claim 1, wherein said ink jet head printing process is a powder bed inkjet head 3D printing process.
3. The method according to claim 2, wherein at least two different binders having different colors are used in the three-dimensional powder bed inkjet head printing process.
4. The method according to claim 2 or 3, wherein each powder layer has a thickness of about 0.09 to about 0.1 mm.
5. The method according to any one of claims 2 to 4, wherein the binder is applied to each powder layer at a resolution of about 600 dots per inch.
6. The method according to any one of claims 2 to 5, wherein at least two binders having different colors are used.
7. The method according to any one of claims 2 to 6, further comprising the steps of infiltrating the progenitor tooth model with a curable resin, and subsequently curing the progenitor tooth model.
8. The method according to claim 1, wherein layers two or more photopolymerizable polymers having different colors are applied to a preceding layer, and are cured before the next layer of photopolymerizable polymer is applied.
9. The method according to claim 8, wherein each layer of photopolymerizable polymer has a thickness of about 16 pm.
10.The method according to claim 8, wherein each layer of photopolymerizable polymer has a thickness of about 8 pm.
11.The method according to any one of claims 8 to 10, wherein the photopolymerizable polymer(s) is/are applied at a resolution of about 600 dots per inch.
12.The method according to any one of claims ito ii, wherein the portion(s) of the positive tooth model representing the teeth is/are printed in another color than the portion(s) representing the gum.is
13.A multi-colored positive tooth model suitable for manufacturing an orthodontic appliance, wherein said multicolored positive tooth model is obtainable by a method as defined in any one of claims ito 12.
14.The multi-colored positive tooth model according to claim 13, wherein the portion(s) of the positive tooth model representing the teeth have a different color than the portion(s) representing the gum.
15.The multi-colored positive tooth model according to claim l3or 14, wherein the portion(s) of the positive tooth model representing the teeth are whitish or white, and the portion(s) representing the gum is/are pink.
16. Use of a multi-colored positive tooth model according to any one of claims 13 to for manufacturing an orthodontic appliance.
17.A method for manufacturing an orthodontic appliance, wherein a multicolored positive tooth model is used for pressure molding or vacuum molding of a sheet of thermoplastic material.