Effects of different surface treatments on stainability of ceramics.

STATEMENT OF PROBLEM: Final adjustments may result in a loss of ceramic glaze, a situation which must be corrected by reglazing or polishing to obtain clinically successful restorations; such restorations may be susceptible to staining.

PURPOSE: The purpose of this study was to determine the stainability of ceramics exposed to coffee after different surface treatments and to correlate the surface roughness with the color differences.

MATERIAL AND METHODS: Sixty-six ceramic (IPS e.maxCeram) disks (15 × 2 mm) were fabricated and glazed according to the manufacturer's instructions, then assigned to 6 groups. Group Glaze (Group G), the control, was not subjected to any procedure. All the others were abraded with a diamond rotary cutting instrument. Group Reglaze (Group R) was reglazed; others were polished with different polishing materials; Group Shofu (Group S) was polished with abrasive stone (Dura-Green Stones), coarse silicon polisher (Ceramaster Coarse), silicon polisher (CeraMaster), and polishing paste (Ultra II) with polishing disks (Super-Snap Buff Disks); Group Ultradent (Group U) was polished with 1.0 and 0.5-μm polishing pastes (Ultradent Diamond) with a goat hair brush (Jiffy) and Group Bredent (Group B) was polished with an abrasive stone (Diagen turbo grinder), a round polishing brush (Abraso-fix), and polishing paste (Diamond) with felt wheels. Group Diamond rotary cutting instrument (Group D) was not treated after abrasion with a diamond rotary cutting instrument. Surface roughness was evaluated by profilometer (n=10), and 1 specimen from each group was evaluated by scanning electron microscopy (SEM). Color difference was measured by a spectrophotometer before and after 12 days of immersion in a coffee solution. Data were analyzed by 1-way ANOVA, the Tukey HSD test, and the Pearson rank correlation tests (α=.05).

RESULTS: The surface roughness (Ra) values were ordered from the highest to the lowest value, which were Group D, B, U, S, R, and G, respectively. Significant differences among groups (P<.01) were found, except for G and R. There were no significant differences between the color difference values of Groups G and R, both of which were significantly lower than the other groups (P<.01). Group D showed the highest ΔE values (>2), which is considered clinically unacceptable (P<.01). No significant differences were found among the S, U, and B groups. There was an 83% positively significant relationship between Ra and ΔE values (P<.01). Rough surfaces stained more after coffee immersion than did smooth surfaces.

CONCLUSIONS: Surface treatments affected surface roughness and color stability. Smooth surfaces showed better color stability after discoloration. Ceramic staining may be related to surface texture changes after different surface treatments.