COMPOSITE MATERIAL KIT FOR DENTAL FILLINGS AND METHOD FOR DETERMININING THE COLOUR OF A DENTAL FILLING

Abstract: A composite material kit for dental fillings, comprises a base composite material, the three-dimensional colour value of which, expressed as hue, chroma and blackness/whiteness, so corresponds to that of an average selection of natural teeth that the visual impression of tooth and filling will be the same, and at least three further composite materials, the three-dimensional colour values of which deviate in different directions from the colour value of the base composite material in such a way that adequate coverage is obtained of the colour value dispersion of natural teeth. When using the composite material kit, the colour is matched by selecting one of the four and preferably five composite materials, of which the base composite material is one and the other composite materials have colour values deviating from the colour value of the base composite material towards whiter, blacker and more coloured with higher blackness or, in the preferred case, more yellowish and more coloured with higher blackness, respectively. the colour can also be matched by selecting the thickness of an outer layer (5) of the filling, the composite material of the inner layer (4) being selected among any of the remaining composite materials, and the outer layer being formed of the base composite material which, in this case, has a lower opacity than the remaining composite materials, and/or a transparent composite material.

Description: COMPOSITE MATERIAL KIT FOR DENTAL FILLINGS AND METHOD FOR DETERMINING THE COLOUR OF A DENTAL FILLING The present invention relates to composite materials for dental fillings and methods for determining the colour of a dental filling in order to match the colour of the filling to that of the adjoining tooth substance. It is known to use for dental fillings, primarily front tooth fillings, different types of composite mate- rial usually consisting of an organic or inorganic filler and a plastics base which is polymerisable, for example by means of light. To make a filling of a composite material fully match the surrounding teeth in respect of colour, the dentist must make a difficult selection of a suitable colour and a subsequent uncertain practical matching of the colour of the composite material on the basis of the colour se¬ lected. The suitable colour has frequently been established by comparing the colour of the patient's teeth with a large range of colour samples. Once the colour sample which best matches with the colour of the patient's teeth has been selected, the composite material to be utilised has been applied. It has been found that matching the colour of the composite material is a problem which most dentists have in common. For a successful result, the dentist must have, inter alia, a sound knowledge of chromatics. It is the object of this invention to simplify match- ing of the colour of a dental filling with that of the adjoining tooth substance. This object is achieved by means of a composite ma¬ terial kit for dental fillings. According to the inven¬ tion, the kit is characterised by a base composite mate- rial, the three-dimensional colour value of which, ex¬ pressed as hue, chroma and blackness/whiteness, so cor¬ responds to that of an average selection of natural teeth that the visual impression of tooth and filling will be the same, and at least three further composite materials, the three-dimensional colour values of which deviate in different directions from the colour value of the base composite material in such a way that adequate coverage is obtained of the colour value dispersion of natural teeth. Proceeding from the known colour value dispersion of natural tooth material (see for example the series of ar¬ ticles published by Robert C. Sproull in J. Prosthet. Dent. Vol. 29, No. 4, April 1973, pp. 416-424; Vol. 29, No. 5, May 1973, pp.556-566; and Vol. 31, No. 2, Feb. 1974, pp. 146-154), it could be shown by experiments con¬ ducted in connection with the present invention that a division of the problem situations into a number of prin- cipal areas gave the solution according to the invention. To achieve adequate coverage, four principal areas should suitably be defined which are readily discernible to the dentist. Admittedly, it is possible to restrict the number of principal areas to three, or to increase the number of principal areas to five or more, but in the first instance the coverage of the colour value dispersion of the natural tooth material will not be as satisfactory, and more than five principal areas make the colour selection too diffi¬ cult for the dentist. A first one of the said principal areas has been defined as comprising whiter tooth material, and a second one as comprising blacker tooth material than the average tooth material. In the composite material kit according to the invention, two further composite materials have there- fore been incorporated, of which a first one is whiter and a second one is blacker than the base composite material. For the case with but three principal areas, it would be possible to include in the composite material kit according to the invention a third further composite ma- terial which is more coloured and blacker than the base composite material. In the preferred embodiment of the invention, howe¬ ver, there is used, besides the first-mentioned two prin¬ cipal areas, also a third principal area comprising more yellowish tooth materials than the average tooth material, and a fourth principal area comprising more coloured and blacker tooth material than the average tooth material. In the composite material kit according to the invention, a third further composite material which is more yellowish than the base composite material, and a fourth further composite material which is more coloured and blacker than the base composite material, have been incorporated. All of the said further composite materials included in the kit preferably have one and the same opacity, a suitable value of which is approximately 60%. In the most preferred embodiment of the composite ma¬ terial kit according to the invention, the base composi¬ tion material is included in two variants in respect of opacity, one variant having the same opacity as the fur¬ ther composite materials, and the second variant having a lower opacity, for example 40%. According to the invention, the last-mentioned va¬ riant of the base composite material can be utilised for varying the degree of deviation from the colour of the base composite material of the finished tooth filling, more particularly by providing the variant having the lower opacity in the form of a layer on top of a layer of some of the further composite materials. By varying the relative thicknesses of the two layers, the degree of de¬ viation from the colour of the base composite material to- wards the selected further composite material can be readily controlled. As has been mentioned above, a colour can be charac¬ terised as a three-dimensional colour value in which the three dimensions or parameters represent hue, chroma and blackness/whiteness. This characterisation is always pos¬ sible, although it is not the only one possible. A known system of this characterisation is the so-called natural colour system usually termed the NCS or NC system which indicates by a sequence of digits and letters first the degree of blackness by a two-digit percentage, then the degree of chroma by a two-digit percentage, and finally the hue by a first primary colour indication followed by a two-digit percentage for a subsequent second primary co¬ lour indication, for example 1020-Y30R where Y represents yellow and R represents red. In an especially preferred embodiment of the compo- site material kit according to the invention, the base composite material has approximately the colour value in the NC system which is designated 1525-Y30R, and the fur¬ ther composite materials have approximately the colour values which in the NC system are designated 1010-Y30R (whiter), 3020-Y30R (blacker), 1030-Y10R (more yellowish) and 3030-Y30R (more coloured and blacker). In a method for determining the colour of a dental filling of composite materials for matching the colour of the filling to that of the adjoining tooth substance, the above-mentioned object of the invention is achieved in that the colour is determined by selecting one of at least four and preferably five composite materials, of which a base composite material has a three-dimensional colour value, expressed as hue, chroma and blackness/whiteness, which so corresponds to that of an average selection of natural teeth that the visual impression of tooth and filling will be the same, and the other composite mate¬ rials have colour values deviating from the colour value of the base composite material towards whiter, blacker and more coloured with higher blackness or, in the preferred case, more yellowish and more coloured with higher black¬ ness, respectively. Furthermore, the colour can be matched by selecting the thickness of an outer layer of the filling, the com- posite material of the inner layer being selected among one of the other composite materials, and the outer layer being formed of the base composite material which, in this case, has a lower opacity than the remaining composite ma¬ terials, and/or a transparent composite material. A practical utilisation of the composite material kit and the method according to the invention will now be de- scribed below, reference being had to the accompanying drawing i which Fig. 1 is a partial cross-sectional view of a front tooth without filling, and Fig. 2 is a partial cross-sectional view having a filling according to the in¬ vention. Teeth generally have an outer layer of enamel 1 over the principal tooth material 2, called dentine. The enamel is more translucent than the dentine, and in the case of the front tooth the thickness of the enamel layer usually decreases in the cervical direction on the tooth, as shown in Fig. 1. In view hereof, a normal front tooth is relatively transparent incisally. Before a filling is built up, the cavity at issue is enlarged, or those parts of the tooth that are to be re¬ placed, are removed. Fig. 2 illustrates a situation in which a large part of a front tooth must be replaced in¬ cisally. A post 3 has been formed, and about this post the filling is to be built up. In a first step, the surface of the enamel is etched, whereupon a bonding material that can be bonded micro- mechanically to the etched enamel 1, is applied. If the post 3 is discoloured, it is possible, before application of the composite material according to the invention, to apply an essentially entirely opaque and covering primer to mask the discoloration, whereupon the composite material is applied either by a one-step procedure or by a two-step procedure. The one-step procedure is utilised in the event that the colour of the tooth and the surrounding teeth matches that of the base composite material or that of one of the said further composite materials. The two-step procedure which is illustrated in Fig. 2, is utilised in the event that the colour deviation between the tooth and the surrounding teeth from the base composite material is not as pronounced as the colour de- viations of the further composite materials. In this case, a layer 4 of the further composite material at issue is first applied, followed by a layer 5 of the base composite material in the variant having the lower opacity. The re¬ sult of this sequence of the layers is a correct build-up of the tooth in respect of colour, with a more opaque, more strongly coloured inner part and a more translucent outer part, such that the repaired tooth will have a natu¬ ral lustre. To further increase the lustre, it is pos¬ sible, both in the one-step and in the two-step procedure, to use a transparent material for forming a thin surface layer 6 on the tooth, and this transparent material may be highly translucent. The above-mentioned examples of colour values for the composite materials according to the invention have been determined at a given thickness (~1.5 mm) of the solidi¬ fied composite material and with a given background (a grey hue corresponding to the blackness 1500 of the NC system) . Summing up, it will be appreciated that the composite material kit according to the invention greatly facili¬ tates the dentist's work in that it provides, in a simple and convenient manner, a starting point for the colour of a filling, which the dentist just as simply and conve¬ niently can modify with regard to other objective and sub- jective factors affecting the visual impression of the repair, such as lighting, surface area, viewing angle, surrounding colours, and background. For a large proportion of patients, perhaps fifty percent or more, the base composite material is sufficient because its colour value has been selected to lie in a statistical centre of gravity of the colour value dispersion of natural teeth. It will, of course, be realised that the invention is not restricted to the embodiments described above, and that it can be modified in several respects within the scope of the appended claims. For example, two or more opaque and covering primers may be used, whereby the colour deviation relative to the colour value of the base composite material can be increased.

Claims: CLAIMS 1. Composite material kit for dental fillings, c h a r a c t e r i s e d by a base composite material, the three-dimensional colour value of which, expressed as hue, chroma and blackness/whiteness, so corresponds to that of an average selection of natural teeth that the visual impression of tooth and filling will be the same, and at least three further composite materials, the three- dimensional colour values of which deviate in different directions from the colour value of the base composite material in such a way that adequate coverage is obtained of the colour value dispersion of natural teeth. 2. Composite material kit as claimed in claim 1, c h a r a c t e r i s e d in that it contains the base composite material in two variants having the same colour value but different opacity, preferably about 40% and 60% opacity, of which variants the one having the lower opaci- ty is adapted to be applied in the form of a layer on top of any of said further composite materials. 3. Composite material kit as claimed in claim 2, c h a r a c t e r i s e d in that said further composite materials have essentially the same opacity as the more opaque variant of the base composite material. 4. Composite material kit as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that a first one of said further composite materials, expressed in the NC system, is whiter and a second one blacker than said base composite material. 5. Composite material kit as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that a third of said further composite materials, expressed in the NC system, is more coloured and blacker than the base compo- site material. 6. Composite material kit as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that a third one of said further composite materials, expressed in the NC system, is more yellowish, and a fourth one more co- loured and blacker than the base composite material. 7. Composite material kit as claimed in claim 6, c h a r a c t e r i s e d in that the base composite material has approximately the colour value which, in the NC system, is designated 1525-Y30R, and said further com- posite materials approximatey the colour values which, in the NC system, are designated 1010-Y30R (whiter), 3020- Y30R (blacker), 1030-Y10R (more yellowish) and 3030-Y30R (more coloured and blacker). 8. Composite material kit as claimed in any one of claims 1-7, c h a r a c t e r i s e d in that it also comprises at least one opaque material for covering dis- colourations underneath the composite material filling, and a translucent material for forming a surface layer. 9. Method for determining the colour of a dental filling of composite material for matching the colour of the filling to that of the adjoining tooth substance, c h a r a c t e r i s e d in that the colour is deter¬ mined by selecting one of at least four and preferably five composite materials, of which a base composite mate- rial has a three-dimensional colour value, expressed as hue, chroma and blackness/whiteness, which so corresponds to that of an average selection of natural teeth that the visual impression of tooth and filling will be the same, and the other composite materials have colour values de- viating from the colour value of the base composite ma¬ terial towards whiter, blacker and more coloured with higher blackness or, in the preferred case, more yellowish and more coloured with higher blackness, respectively. 10. Method as claimed in claim in claim 9, c h a - r a c t e r i s e d in that the colour is matched by se¬ lecting the thickness of an outer layer of the filling, the composite material of the inner layer being selected among one of the other composite materials, and the outer layer being formed of the base composite material which, in this case, has a lower opacity than the remaining com¬ posite materials, and/or a transparent composite material.

Inventors: LEMPERT JOHN, LEMPERT, JOHN
Applicants: NORDISKA DENTAL AB
Application year: 1989
Main classification: A61K6
IPC codes: A61C5, A61C13, A61K6