GB2433444A

GB2433444A - Artificial teeth

Info

Publication number: GB2433444A
Application number: GB0526063A
Authority: GB
Inventors: Richard John Tyrrell; Brian Dennis Schottlander
Original assignee: Davis Schottlander and Davis Ltd
Current assignee: Davis Schottlander and Davis Ltd
Priority date: 2005-12-21
Filing date: 2005-12-21
Publication date: 2007-06-27
Also published as: WO2007071980A3; GB0526063D0; WO2007071980A2

Abstract

In a set of artificial teeth comprising a maxillary unit and a mandibular unit, each having at least two posterior teeth formed as a one-piece unit, the teeth of the maxillary unit are moulded such that the spacing between each corresponding cusp of immediately adjacent ones of the said maxillary posterior teeth is substantially uniform for each of the said maxillary posterior teeth, the teeth of the mandibular unit are moulded such that the spacing between each corresponding cusp of immediately adjacent ones of the said mandibular posterior teeth is substantially uniform for each of the said mandibular posterior teeth, and the cusp spacings of the maxillary posterior teeth are substantially the same as those of the mandibular posterior teeth. Alternatively, or in addition, the teeth of the maxillary unit are moulded such that the or each cusp has an articulating surface which is inclined at an angle which is substantially the same as the angle of inclination of the corresponding articulating surface of the corresponding cusp of the or each immediately adjacent one of the said maxillary posterior teeth, the teeth of the mandibular unit are moulded such that the or each cusp has an articulating surface which is inclined at an angle which is substantially the same as the angle of inclination of the corresponding articulating surface of the corresponding cusp of the or each immediately adjacent one of the said mandibular posterior teeth, and the cusp angles of the maxillary posterior teeth are substantially the same as those of the mandibular posterior teeth. Preferably, the fossa spacings of the maxillary and mandicular posterior teeth are substantially elongate.

Description

ARTIFICIAL TEETH

The present invention relates to a set of artificial teeth for use in a denture.

The most frequently occurring tooth distribution in the natural human dentition comprises, in each quadrant of the mouth, three front teeth (being a central, a smaller lateral and a canine or eye tooth) followed by the posterior teeth: two pre-molars and three molars. Three or four posterior teeth in each quadrant (normally four teeth) are usually used when constructing a denture. The third molar, which is most posterior, does not always occur in the natural dentition, but in any event is not normally reproduced in denture teeth because there is rarely sufficient height at the back of the mouth for it.

On either side of the mouth, perfectly aligned natural teeth fit naturally together so that the palatal cusps of those in the upper jaw (maxillary teeth) fit precisely into the fossae of the teeth of the lower jaw (mandibular teeth) and the buccal cusps of those in the lower jaw fit precisely into the fossae of the teeth in the upper jaw.

This is called inter-cuspation. The same applies for artificial teeth used to make dentures. They must inter-cuspate, so that there is a natural intercuspal position but in addition, as the lower jaw slides from side to side and forwards and then back again, the cusps on upper and lower denture teeth should remain in contact. The lower jaw is hinged at the tempero-mandibular joints. Since these joints are above the level of the teeth, the posterior denture teeth are set in an upwards curve from front to back when viewed laterally. The condyle movement induces a similar lateral curve of movement when viewed from the front. Artificial teeth must also be set up in a denture for balanced articulation: this means that the posterior teeth of both sides of the jaws remain in contact when the lower jaw is moved a short distance to the left or to the right or forwards. Thus, within that range, biting the back teeth of one side of the dentures together does not cause the other side of the dentures to be displaced even when they are not in the inter-cuspal position.

When individual artificial teeth have been set up in a denture a problem which frequently occurs is that, as movements of the lower jaw take place, the cusps of the lower teeth lock together with those of the upper, leading to displacement of the dentures. Many attempts have been made to reduce this locking together, including adjusting the design of the position of the cusps relative to each other, and changing the various cusp angles and shapes of contact surfaces. These attempts have met with limited success, in part because, when each tooth is set up separately in the wax by the dental technician making the denture, errors in the position and shape of that tooth, although very small in themselves, are compounded with each subsequent tooth set up in relation to its predecessor.

Thus, attempts to prevent locking together of the teeth have only been effective when all four posterior teeth in the quadrant concerned have been correctly set up relative to each other and in relationship to the teeth in the opposing quadrant.

In order to facilitate setting up of posterior teeth in a denture it has been previously proposed, for example in WO 2004/096077 Al, to provide a group of four posterior teeth formed as a one-piece unit. By supplying a dental technician with teeth in which the position and orientation of the teeth in the group have been fixed relative to one another, some of the above-mentioned problems can be overcome. However, as supplied by the manufacturer, the group of four teeth proposed in WO 2004/096077 Al are not suitable for use in all forms of occlusal contact, but are designed only for lingualised occlusion (where only the lingual cusp of each upper posterior tooth makes contact with the occlusal surfaces of the lowers) . Extensive grinding and cutting of the moulded teeth by a dental technician would be required to permit alternative forms of occiusal contact.

In the following description and claims the terms

"occiusal surface", occlusal zone'', "occluding surface", "articulating surface" and lingualised occlusion'' should be understood as follows: The occlusa]. surface of a tooth is that surface that has evolved or been designed to come into contact or near contact with the equivalent surface of an opposing tooth in the other jaw.

An occiusal zone of a tooth is a region (rather than a point) of the tooth's occiusal surface that is designed to come into contact with the occiusal surface of an opposing tooth in the other jaw.

The occluding surface is that part of the occlusal surface of a tooth that makes contact with an opposing tooth when the lower jaw is stationary.

The articulating surface is that part of the occlusal surface of a tooth that makes sliding contact with an opposing tooth when either the upper arm of an articulator or the lower jaw is moving.

Lingualised occlusion is an arrangement of posterior denture teeth in which the occluding and articulating contacts are limited to the lingual (palatal) cusps of the maxillary teeth contacting the central fossae of the mandibular teeth; the upper buccal cusps remain out of contact in all jaw positions.

According to an embodiment of the present invention, there is provided a set of artificial teeth comprising a maxillary unit and a mandibular unit, each of the maxillary and mandibular units comprising artificial teeth having at least two posterior teeth formed as a one- piece unit, each of the teeth having at least one working cusp, wherein the teeth of the maxillary unit are moulded such that the spacing between each corresponding working cusp of immediately adjacent ones of the said maxillary posterior teeth is substantially uniform for each of the said maxillary posterior teeth, the teeth of the mandibular unit are moulded such that the spacing between each corresponding working cusp of immediately adjacent ones of the said mandibular posterior teeth is substantially uniform for each of the said mandibular posterior teeth, and the working cusp spacings of the maxillary posterior teeth are substantially the same as those of the mandibular posterior teeth.

It should be noted that the wording "substantially" as used here in relation to the cusp spacings is intended to include at least an embodiment in which the cusp spacings of the mandibular teeth are very slightly greater than those of the maxillary teeth, because of the curvature of the occlusa]. surface from the front to the back of the mouth. In practice this difference is minute, i.e. around 0.2mm.

Alternatively, or more preferably in addition, the teeth of the maxillary unit are moulded such that the or each working cusp has an articulating surface which is inclined at an angle which is substantially the same as the angle of inclination of the corresponding articulating surface of the corresponding working cusp of the or each immediately adjacent one of the said maxillary posterior teeth, the teeth of the mandibular unit are moulded such that the or each working cusp has an articulating surface which is inclined at an angle which is substantially the same as the angle of inclination of the corresponding articulating surface of the corresponding working cusp of the or each immediately adjacent one of the said mandibular posterior teeth, and the working cusp angles of the maxillary posterior teeth are substantially the same as those of the mandibular posterior teeth.

These arrangements of the cusps allows artificial teeth embodying the present invention, without the need for significant cutting or grinding of the moulded teeth by a dental technician, to slide in contact laterally and antero-posteriorly such that there is no interference between the cusps of the upper and lower teeth.

Preferably, or alternatively, the maxillary and mandibular units can be set up in a denture in more than one position, bucco-lingually and/or antero-posteriorly, with respect to the opposing unit such that there are at least three occiusa]. zones in contact therebetween.

Desirably, the maxillary and mandibular units can be set up in a denture in more than one such position, bucco-lingually, irrespective of whether the units have been set up for normal occlusal contact or cross bite contact in their intercuspal relationships.

Similarly, the maxillary and mandibular units can desirably be set up in a denture in more than one such position, antero-posteriorly, irrespective of whether the units have been set up for normal occlusal contact, protrusive contact or retrusive contact in their intercuspal relationships.

Thus, the design of the occlusal morphology allows movement of a maxillary unit relative to the mandibular unit on an articulator set with a range of incisive and condylar guidance angles so that there are not less than three articulating surfaces in contact between the maxillary and mandibular units on each side of the arches over a range of maxillary movements, allowing the establishment of balanced articulation.

In one particular embodiment of the present invention, there may be three, four or five such integrally-formed posterior teeth. Desirably, the teeth are moulded to have a natural appearance.

Preferably, each of the teeth has a series of fossae and the teeth of the maxillary unit and the teeth of the mandibular unit are moulded such that the said fossae are substantially elongate. By elongating the fossae mesially/distally, to give greater tolerance, at least three cusps can move into one each of the fossae areas. The shape and arrangement of the features of teeth embodying the present invention are achieved solely, or virtually solely, through the mould used to manufacture the teeth, and not through any significant post-manufacture cutting or grinding of the teeth.

The teeth may be moulded such that the teeth in the unit are joined from just below the marginal ridge above the contact area to just above the cervical margin so that the spaces between the teeth give both the illusion of embrasure spaces and also maintain the buccal contour, so maintaining a natural aesthetic appearance. Thus, the interdental space between the teeth in the units is made more shallow than would normally occur with separate teeth, reducing the likelihood that organic matter is trapped during use, or that plaster is trapped following deflasking, and making it easier to wax-up the gum work in a natural manner in the manufacturing process and to hide bars and attachments within the normal tooth shape whilst still maintaining a realistic aesthetic appearance.

The shallow embrasures allow the inside of the teeth to be partially hollowed out underneath to make space for bars and attachments within the tooth shape so that less (or none) of the external moulded surfaces of the buccal or palatal contour of the teeth has to be ground away to accommodate them, so preserving an aesthetic appearance when tooth units need to be modified.

Desirably, the teeth are also moulded such that at their necks the buccal and palatal form is not substantially separated between the teeth, but nevertheless has a natural appearance. This allows bars or attachments to be fitted within the tooth shape such that they are either not visible, or are less visible, without the natural buccal form having to be ground away. In prior art teeth the separation between the teeth is greater and starts further down.

Further, the teeth may be moulded such that the embrasures and/or the fissures of the teeth are wider than 0.2mm to 0.3mm, i.e. the width of a normal toothbrush filament, and preferably wider than 0.5mm, i.e. the width of the filaments in a special denture cleaning brush. That, is by making the embrasures of the teeth wider than the width of a normal toothbrush filament or denture brush filament, it is easier for the user to clean the teeth.

If the angles of the equivalent slopes formed between the cusps and the marginal ridges of each tooth in a unit are approximately equal, then the teeth may be designed with natural cuspal heights such that the cusp angles can be in the range 5 to 40 , and preferably between 15 and 35 , whilst the cusps can pass freely over the marginal ridges with minimal vertical displacement of the dentures as they do so.

Preferably, a set of artificial teeth embodying the present invention comprises two pairs of maxillary and mandibular units, for arrangement in dentures in respective quadrants thereof, wherein the teeth of each of the maxillary and mandibular units are moulded such that, when the units have been have been set up in a denture, there are at least three occiusal zones in contact between the teeth of the maxillary units and the corresponding mandibular units, irrespective of whether the teeth are set up for normal occiusal contact, cross bite contact, protrusive contact or retrusive contact.

Thus, the maxillary and mandibular units for either side of the mouth are so designed so that when the occlusal surfaces of the opposing units are brought together into a range of occiusal relationships there will be at least three zones of tooth contact between the upper and lower units on each side of the mouth, thus imparting stability to the dentures so that, when the dentures move in the mouth, contact is maintained, whether the teeth are set up for normal occlusal contact, cross bite contact, protrusive contact or retrusive contact. Because there are zones of contact, rather than merely point contacts, stability can be achieved with only three contact zones.

Desirably, the teeth are moulded such that if the maxillary and mandibular units slide on each other mesio-distally there are still at least three occlusal zones in contact between the mandibular units and the corresponding maxillary units.

Further, the teeth are desirably moulded such that if the maxillary or mandibular units slide antero-posteriorly against each other there are still at least three occiusal zones in contact between the mandibular units and the corresponding maxillary units.

According to another aspect of the present invention, there is provided a device for use in setting up artificial teeth in a denture in a lingualised occiusal relationship, where the artificial teeth comprise a maxillary unit and a mandibular unit and each unit has at least two posterior teeth formed as a one-piece unit, wherein the device comprises a member of approximately uniform thickness shaped so as to fit over at least one buccal cusp of the said maxillary unit.

Reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 shows the buccal surfaces of upper and lower artificial teeth embodying the present invention and the curvature of the occlusal plane of the teeth; Figures 2A to 2F show the occlusal surfaces of upper and lower teeth embodying the invention in more detail; Figures 3, 4 and 5 show upper and lower artificial teeth embodying the present invention in different relationships, Figure 3 showing the buccal surfaces, Figure 4 showing the occlusal surfaces, and Figure 5 showing the occlusal overlay; Figures 6A and 6C show individual artificial teeth which do not embody the present invention and Figures GB and GD show a block of artificial teeth embodying the invention, Figures 6A and GB showing the buccal surfaces and Figs. 6C and 6D showing the underside of the teeth; and Figure 7 shows a spacer for use when setting up the teeth for lingualised occlusion.

Figure 1 shows four artificial posterior teeth, two pre-molars and two molars, formed as a one-piece unit using a moulding process. Figures 2A to 2F show the working cusps, non-working cusps and fossae areas of artificial teeth embodying the present invention.

According to an aspect of the present invention, the spacings between adjacent working cusps are substantially identical to one another. In this regard, for the purpose of the present patent application, the distal lingual (3) cusp of the lower 1st molar (6) and the distal lingual (2nd) cusp of the upper second molar (7) are mainly cosmetic and not classed as working cusps.

According to another aspect of the present invention, the angles of inclinations of one occlusal surface of the working cusps (i.e. cusp angles) are substantially identical to one another. The cusp angles can be in the range 5 to 40 , and preferably between 15 and 35 . The oppositely-inclined occiusal surfaces of the cusps of the maxillary and mandibular teeth are also inclined at angles which are substantially identical to one another.

Figures 2A to 2F show the working cusps, non-working cusps and fossae of artificial teeth embodying the present invention when the teeth are set up in the most common Class II relationship (Fig. 4A). As shown in Figures 2C to 2F, the spacing between adjacent upper working cusps is indicated as UC1, UC2, UC3, UC4,UC5 and UC6. According to a preferred embodiment, the spacings UC1 to UC6 are substantially evenly spaced to one another when viewed in the occlusal plane. Similarly, the spacings between adjacent lower working cusps is indicated as LC1, LC2, LC3, LC4, LC5 and LC6. According to a preferred embodiment, the spacings LC1 to LC6 are substantially evenly spaced to one another when viewed in the occiusal plane. In Figs. 2C to 2F also there are positions on fossae tJFl, tJF3, tJF5, UF6, UF8 and UF9 where the distance between them is substantially equivalent one to the other. The same is true of fossae UF2, UF4, UF6, UF7, and UF9, of fossae LF1, LF3, LF5, LF7 and LF9 and of fossae LF2, LF4, LF6 and LF8.

Figs. 3 and 4 show the same five relationships shown from the buccal and occiusal views: (A) is the most common Class II relationship; (B) is another, frequent but less common, Class II relationship; (C) shows the teeth in a stable relationship with the teeth edge to edge (i.e. the upper and lower cusps are in contact and so there is no cusp/fossa contact); (D) shows a Class III relationship; and (E) shows an open anterior bite. These drawings are just exemplarly, since many other relationships are possible but are not shown.

As also shown in Figure 4, the spacing of at least three of the working cusps matches the spacing of the fossae of the opposing teeth. Compared to prior art teeth, the fossae are elongated mesially/distally to allow this multiple positioning. Each working cusp can be positioned in a choice of four different intercuspal, cusp/fossa relationships and also cusp to cusp relationships, still maintaining three occluding areas as shown in Figure 4.

Those cusps or cusp/fossa which match up in each relationship are indicated.

A maxillary unit and a mandibular unit, both comprising artificial teeth embodying the invention, may contact one another in four occlusal relationships: normal occiusal contact, cross bite contact, protrusive contact or retrusive contact. In each arrangement there are at least three zones of contact between the upper and lower teeth.

The interdental spacing in artificial teeth embodying the present invention would be virtually undetectable, the teeth being formed so as to abut one another. The depth of the interdental spacings in teeth embodying the present invention is also very shallow so as to ensure matter is not trapped, the teeth in the unit being joined from just below the marginal ridge above the contact area to just above the cervical margin, to give the illusion of embrasure spaces whilst having a realistic natural appearance.

The embrasures of the teeth are also wider than 0.5mm for ease of cleaning by a denture cleaning brush.

As shown in Figures 6B and 6D, a set of artificial teeth embodying the present invention has more tooth structure in the interproximal and neck areas, i.e. H2 > H1 and W2 > W1, so making it easier to provide space in a recess on the underside of the teeth for bars and attachments within the tooth shape. Accordingly, less (or none) of the inside of the teeth has to be ground away when the teeth unit has to be modified, thereby allowing the aesthetic appearance of the teeth to be preserved.

As shown in Fig. 7, when teeth units embodying the present invention are to be set up for lingualised occlusion, an insert, of approximately uniform thickness, for example 1mm., may be used. The insert, which may be plastic or rubber, for example, is shaped to fit over the buccal cusps of the corresponding maxillary unit, so that, when one side of the device is fitted over the maxillary unit and the mandibular unit is articulated to the other side of the device, the angle of inclination of the two units relative to each other are correctly aligned for lingualised occlusion, so that this alignment can be achieved quickly and easily. Preferably, the fit is such that the spacer is retained on the unit without assistance.

Claims

Claims 1. A set of artificial teeth comprising a maxillary unit and a

mandibular unit, each of the maxillary and mandibular units comprising artificial teeth having at least two posterior teeth formed as a one-piece unit, each of the teeth having at least one working cusp, wherein the teeth of the maxillary unit are moulded such that the spacing between each corresponding working cusp of immediately adjacent ones of the said maxillary posterior teeth is substantially uniform for each of the said maxillary posterior teeth, the teeth of the mandibular unit are moulded such that the spacing between each corresponding working cusp of immediately adjacent ones of the said mandibular posterior teeth is substantially uniform for each of the said mandibular posterior teeth, and the working cusp spacings of the maxillary posterior teeth are substantially the same as those of the mandibular posterior teeth.

2. A set of artificial teeth as claimed in claim 1, wherein each of the said teeth has a series of fossae and the teeth of the maxillary unit and the teeth of the mandibular unit are moulded such that the said fossae are substantially elongate.

3. A set of artificial teeth as claimed in claim 1 or 2, wherein the teeth of the maxillary unit are moulded such that the or each working cusp has an articulating surface which is inclined at an angle which is substantially the same as the angle of inclination of the corresponding articulating surface of the corresponding working cusp of the or each immediately adjacent one of the said maxillary posterior teeth, the teeth of the mandibular unit are moulded such that the or each working cusp has an articulating surface which is inclined at an angle which is substantially the same as the angle of inclination of the corresponding articulating surface of the corresponding working cusp of the or each immediately adjacent one of the said mandibular posterior teeth, and the working cusp angles of the maxillary posterior teeth are substantially the same as those of the mandibular posterior teeth.

4. A set of artificial teeth comprising a maxillary unit and a mandibular unit, each of the maxillary and mandibular units comprising artificial teeth having at least two posterior teeth formed as a onepiece unit, wherein the teeth of the maxillary unit are moulded such that the or each working cusp has an articulating surface which is inclined at an angle which is substantially the same as the angle of inclination of the corresponding articulating surface of the corresponding working cusp of the or each immediately adjacent one of the said maxillary posterior teeth, the teeth of the mandibular unit are moulded such that the or each working cusp has an articulating surface which is inclined at an angle which is substantially the same as the angle of inclination of the corresponding articulating surface of the corresponding working cusp of the or each immediately adjacent one of the said mandibular posterior teeth, and the working cusp angles of the maxillary posterior teeth are substantially the same as those of the mandibular posterior teeth.

5. A set of artificial teeth as claimed in claim 4, wherein each of the said teeth has a series of fossae and the teeth of the maxillary unit and the teeth of the mandibular unit are moulded such that the said fossae are substantially elongate.

6. A set of artificial teeth as claimed in any preceding claim, wherein the maxillary and mandibular units can be set up in a denture in more than one position, bucco-lingually, with respect to the opposing unit such that there are at least three occlusal zones in contact therebetween, irrespective of whether the units have been set up for normal occlusal contact or cross bite contact.

7. A set of artificial teeth as claimed in any preceding claim, wherein the maxillary and mandibular units can be set up in a denture in more than one position, antero-posteriorly, with respect to the opposing unit such that there are at least three occiusal zones in contact therebetween, irrespective of whether the units have been set up for normal occiusal contact, protrusive contact or retrusive contact.

8. A set of artificial teeth comprising a maxillary unit and a mandibular unit, wherein the maxillary and mandibular units can be set up in a denture in more than one position, bucco-lingually and/or antero-posteriorly, with respect to the opposing unit such that there are at least three occiusal zones in contact therebetween.

9. A set of artificial teeth as claimed in claim 8, wherein the maxillary and mandibular units can be set up in a denture in more than one such position, bucco-lingually, irrespective of whether the units have been set up for normal occlusal contact or cross bite contact.

10. A set of artificial teeth as claimed in claim 8 or 9, wherein the maxillary and mandibular units can be set up in a denture in more than one such position, antero-posteriorly, irrespective of whether the units have been set up for normal occlusal contact, protrusive contact or retrusive contact.

11. A set of artificial teeth as claimed in any one of claims 8 to 10, wherein each of the maxillary and mandibular units comprises artificial teeth having at least two posterior teeth formed as a one- piece unit.

12. A set of artificial teeth as claimed in any preceding claim, wherein there are three, four or five such posterior teeth formed as a one-piece unit.

13. A set of artificial teeth as claimed in any preceding claim, wherein the teeth are moulded such that they have a natural appearance.

14. A set of artificial teeth as claimed in any preceding claim, wherein the teeth are moulded such that the teeth in each of the maxillary and mandibular units are joined from just below the marginal ridge above the proximal contact area to just above the proximal cervical margin.

15. A set of artificial teeth as claimed in any preceding claim, wherein the teeth are moulded such that at their necks the buccal and palatal form is not substantially separated between the teeth, but nevertheless has a natural appearance.

16. A set of artificial teeth as claimed in any preceding claim, wherein the embrasures and/or the fissures in the occiusal surfaces of the teeth and the embrasure spaces between them are wider than 0.2mm.

17. A set of artificial as claimed in claim 16, wherein the embrasures and/or the fissures in the occlusal surfaces of the teeth and the embrasure spaces between them are wider than 0.5mm.

18. A set of artificial teeth as claimed in any preceding claim, wherein the teeth are moulded such that the angles of the equivalent slopes formed between the cusps and marginal ridges of each tooth are approximately equal.

19. A set of artificial teeth as claimed in any preceding claim, comprising two pairs of maxillary and mandibular units, for arrangement in dentures in respective quadrants thereof, wherein the teeth of each of the maxillary and mandibular units are moulded such that, when the units have been have been set up in a denture, there are at least three occlusal zones in contact between the teeth of the maxillary units and the corresponding mandibular units on each side of the mouth, irrespective of whether the units have been set up for normal occlusal contact, cross bite contact, protrusive contact or retrusive contact.

20. A set of artificial teeth as claimed in claim 19, wherein the teeth are moulded such that if the maxillary or mandibular units slide lingually against each other there are still at least three occiusal zones in contact between the mandibular units and the corresponding maxillary units.

21. A set of artificial teeth as claimed in claim 19 or 20, wherein the teeth are moulded such that if the maxillary or mandibular units slide antero-posteriorly against each other there are still at least three occlusal zones in contact between the mandibular units and the corresponding maxillary units.

22. A device for use in setting up artificial teeth in a denture in a desired lingualised relationship, where the artificial teeth comprise a maxillary unit and a mandibular unit and each unit has at least two posterior teeth formed as a one-piece unit, wherein the device comprises a member of approximately uniform thickness shaped so as to f it at least one buccal cusp of the said maxillary unit.