Нигора Зиядуллаева, Нигорахон Ходжимуродова
In the practice of modem dentistry, due to the increased aesthetic requirements, one of the factors that determine the success of prosthetics with all-ceramic, metal-ceramic, zirconium dioxide orthopedic structures is the correct and accurate determination of the color of the teeth and the reconstruction of its anatomical shape and function according to the age of the patient.
This allows achieving high aesthetic quality of orthopedic constructions and reducing the incidence of expensive re-prosthetics.
The teeth color is determined by the dentin, with translucent enamel, which is playing a lesser role through scattering at wavelengths in the blue range [3]. It was reported that: shade selection is a crucial clinical step during prosthetic treatment [4]. During the visual teeth color determination it is suggested that the first impression is frequently the best match, and shade matching trials should be limited to 5 seconds at a time to prevent eye fatigue, because the vision pigment is used up quickly in the mechanism of color perception. Many times in the dental literature has been given the recommendation to relax the eyes by observing a blue card between two shade matching trials (because blue and yellow arc complementary colors) [5].
An adequate analysis of the shade of the teeth, as well as the reproduction of their color in order to maximize the imitation of the natural appearance, is one of the most difficult tasks of practical dentistry in the rehabilitation of patients using different types of restorations.
Shade matching systems continue to evolve, but so far none of them can provide a sufficiently objective result.
Various protocols for the analysis of tooth color have been known on the market for many years, but most of them provide efficiency only for the chewing group of teeth, or only for the initial analysis of the aesthetics of the frontal region, based on the parameters of photographs and modifications of the algorithms for their visualization and processing. The Vita company also introduced the Vita EASYSHADE® spectrophotometer for tooth shade matching. Shade evaluation with the spectrophotometer used in that study showed a high degree of correlation with visual shade determination of the color of natural teeth . The oldest color system was created by Albert H. Munscll in 1905. Consists from three attributes—hue (H), value or lightness (V) and chroma (C), denoted as H/V/C. Value/Lightness is the quantity of light reflected by an object compared to a pure white diffuser (reflecting 100%), and a black absorber (absorbing all incident light with no reflection). If a material reflects most of the light falling on its surface, it appears bright, i.e. it has a high value. Towards the center of the color wheel, no hue dominates and becomes less and less saturated [ 1 ]. Hue is described with the words we normally think of as describing color: red, purple, blue, etc. It is also a term which describes a dimension of color we readily experience when we look at color.
The action of many factors complicates the process of objectifying the color analysis of teeth and its reproduction. These are the different illumination of the area of interest, which distorts the color perception effect of the final restorations, the use of aesthetic materials of different quality, and the individual difference in color perception among people participating in dental treatment.The factor of the latter is also influenced by what kind of shade matching system each of the participants in the rehabilitation process uses. In addition, it should be borne in mind that the complex morphology of the tooth, its shape, surface texture, as well as the corresponding shine - all these are parameters that cannot be ignored in the process of treating any tooth.
