EXPERIMENTAL EVALUATION OF ZIRCONIA ROUGHNESS AFTER 5 DIFFERENT POLISHING METHODS

PURPOSE:The purpose of this experimental study was to:1.Evaluate the microroughness (Ra degree) and surface morphology by SEM of Y-TZP samples subjected to 5 different polishing methods;2.Evaluate the efficacy of each polishing technique on the basis of published Ra data;3.Identify a polishing technique, which allows obtaining Ra values and a morphologic surface able to prevent bacterial adhesion.METHODS:21 zirconia platelets (1 cm x 0.7 cm thickness 1 mm).Samples were subjected to 5 different polishing methods from 5 different operators. Each operator realized 4 samples. Microroughness measurements and statistical analysis of the data obtained and Morphological analysis by SEM took place at the “Centro Grandi Strumenti” of the University of Modena.RESULTS:Data indicate that all polishing techniques are operator-dependent and the final result can be affected by several variables. Such variables not only led to significant differences between operators but also among samples of the same group. Ra values were reported to be ≥0.3 μm.CONCLUSIONS:1.The polishing techniques not result sufficiently efficacious to reduce Ra surface values of zirconia; surfaces tested are characterized by Ra medium values >0.2µm; values over 0.2µm are not able to prevent bacterial adhesion to the same surface;2.Low Ra values not necessarily correspond with a smooth surface, as indicated by SEM analysis. This shows that a polish zirconia surface can present irregularities anyway;3.Zirconia surfaces analyzed show diversity both in the Ra values reported by microroughness measurements and in the morphologic surface evaluated by SEM, not only between samples polishing by different operators but also between samples of the same operator; therefore, it is important identify a standard polishing method which is able to lead the Ra surface values below 0.2µm and to do uniform the procedures of the different operators.