An in vitro evaluation of zirconia surface roughness caused by different scaling methods

Statement of problem

Plaque control is essential for the prevention of inflammatory periodontal disease. Ultrasonic scaling and hand scaling have been shown to be effective for the removal of plaque. However, routine periodontal prophylactic procedures may alter the surface profile of restorative materials.

Purpose

The purpose of this study was to assess in vitro the changes in roughness of zirconia surfaces treated by various scaling procedures.

Material and methods

One hundred forty identical disks (10 mm in diameter, 2 mm thick) were made. The specimens were divided into 7 groups of 20 each; the surfaces of the specimens were exposed to different types of scaling methods simulating standard clinical conditions. In the control group (C), no scaling procedures were performed; in the other groups, a steel curette (SC), a plastic curette (PC), a titanium curette (TC), a piezoelectric ultrasonic scaler (PUS), an ultrasonic scaler (US), and a magnetostrictive ultrasonic scaler (MUS) were used. The surface texture was analyzed quantitatively and qualitatively with a profilometer and a scanning electron microscope (SEM). A 1-way ANOVA was performed to assess whether roughness profile (Ra) differed among groups, while pairwise comparisons between groups were evaluated by the Tukey HSD test (α=.05).

Results

The 1-way ANOVA revealed significant differences among groups (P<.001); the Tukey HSD test demonstrated that all methods achieved different results. Analysis of zirconia surfaces treated by different ultrasonic scaling systems demonstrated some deeper scratches, whereas zirconia instrumented with various types of periodontal curettes exhibited smaller scratches. Scaling with a steel curette produced the least alteration of zirconia surfaces.

Conclusions

All instrument types evaluated altered the smoothness of zirconia surfaces. Follow-up in vivo studies are indicated to assess potential clinical problems associated with increased roughness at the margin of zirconia restorations following routine dental prophylaxis.