Aplicación de técnicas ópticas para caracterización de estructuras dentales y materiales sintéticos biomiméticos con uso en odontología restauradora

Laburpena

The main objective of this Doctoral Thesis is to characterize the optical and colorimetric properties of new generation dental biomaterials (multilayer hybrid composite resins and one-shade composite resins) and to evaluate the appearance of dental structures under the new LED illuminants proposed by the CIE. To meet this objective, several studies were carried out based on the spectroradiometric measurement of the spectral reflectances of the dental materials for the evaluation of their optical properties: Scattering - S, Absorption - K and Transmittance - T, using the Kubelka-Munk theory. From the measured reflectances, the CIELAB color coordinates (L*, a*, b*, C* and hº) were calculated and used for the colorimetric characterization of the studied materials, as well as the TP and OP-RT parameters. The multilayer hybrid composite resin Vita Enamic MultiColor High Translucent (E-MC) was fully characterized optically and colorimetrically by evaluating each of its layers, for all available shades and for samples with thicknesses of 0.5, 1.0 and 1.5 mm. The layers of the E-MC material showed a gradient of optical and colorimetric properties from the cervical to the incisal layer depending on shade and thickness, registering clinically perceptible color differences between consecutive layers. For the colorimetric evaluation of the one-shaded materials the color matching potential (CAP) and samples with thicknesses of 0.5, 1.0 and 2.0 mm were used. For the first time, complementary to the analysis performed with CAP, adjustment potentials were implemented for lightness, chroma and hue, as well as for translucency, based on the CIEDE2000 color difference formula. Their values depended on the type of composite, Omnichroma being the one that recorded the highest chromatic adaptation potentials. Regarding the optical properties of these materials (Omnichroma, Venus Pearl One and Venus Diamond One), the spectral behavior of S, K and T values was similar for the one-shade composite resins, finding statistically significant differences between the values of the different materials and thicknesses evaluated. The opalescence and translucency parameters showed material-dependent values. Finally, the phenomenon of color inconstancy and the variations in whiteness of a set of 36 human natural dental structures measured in-vivo, under the nine LED illuminants proposed by the CIE, were studied in relation to the standard D65 and A illuminants, as well as the differences in color and whiteness of pairs of dental specimens under each of the illuminants mentioned above. The new LED illuminants generally produced color shifts and whiteness changes above their respective thresholds of 50:50% perceptibility and 50:50% acceptability. The color and whiteness differences produced between two teeth under either LED illuminant were very similar to those obtained under the standard D65 and A illuminants.