The effects of porcelain polishing systems on the color and surface texture of feldspathic porcelain

Abstract

Statement of problem. After the adjustment of glazed porcelain surfaces, the surfaces are roughened and must be reglazed or polished with different porcelain polishing systems to improve the esthetic appearance and strength of the porcelain restorations. Purpose. The purpose of this in vitro study was to compare the effect of different porcelain polishing methods on the color and surface texture of a feldspathic ceramic. Material and methods. Ninety porcelain (Vitadur Alpha) discs (10 X 2 mm) were fabricated in a silicone mold and divided into 9 groups (n=10). A medium-grit diamond rotary cutting instrument was used to remove the glaze layer, and then the surface was polished using I of the 4 following polishing systems or a combination thereof. polishing paste (Ultra II), polishing stick (Diamond Stick), polishing wheel (CeraMaster), or an adjustment kit (Porcelain Adjustment Kit). No surface treatments were applied to the control group. Color measurements were made using a colorimeter (Minolta CR-321 ChromaMeter) according to the CIE L*a*b* color system. Color differences (Delta E) between the control group and experimental groups were calculated. The acceptable level was chosen as 3.3 Delta E units. Then the surface roughness (Ra) (mu m) of the same specimens was evaluated using a profilometer. The data were statistically analyzed by 1-way analysis of variance and Tukey HSD tests (alpha=.05). To evaluate the effects of the polishing systems on the ceramic surfaces at a microscopic level, an additional 9 feldspathic ceramic specimens were prepared and polished to represent each of the 9 groups. These specimens were examined under a scanning electron microscope (SEM). Results. Polishing techniques significantly affected the color of the feldspathic ceramic (P<.001). The Delta E values ranged from 1.03 to 3.36. No significant differences were found within the adjustment kit groups or within the polishing wheel groups. All specimens polished with-the various techniques showed significantly different Ra values than the control specimens (P<.001), except for the groups polished using the adjustment kit. The highest Ra and Delta E values were obtained with the use of polishing paste and polishing stick alone (P<.001). The SEM observations demonstrated that the polishing techniques affected the smoothness of the porcelain surface. Conclusions. The evaluation of the polishing techniques showed that the use of an adjustment kit alone or preceding polishing paste or polishing stick application created surfaces as smooth as glazed specimens. The use of polishing paste alone did not improve the smoothness of the porcelain surface. The color differences of all groups were found to be at the acceptable level.