Effect of charcoal dentifrices on tooth whitening and enamel surface roughness

Purpose: To evaluate tooth color change and surface roughness after the use of charcoal dentifrices. Methods: Bovine teeth (n= 64) used for color measurements were stained in tea solution and embedded in acrylic resin. Specimens were randomized into four groups of 16 specimens each. Cavity Protection (Colgate-Palmolive) was the negative control. Whitening dentifrices used were Black is White (Curaden AG); and My Magic Mud (Carbon and Clay Company) containing activated charcoal and Optic White (Colgate-Palmolive) containing hydrogen peroxide. Instrumental color measurements were performed at baseline, 1 -week post-brushing, 30 -day post-brushing, and 1 -month follow-up. Another set of bovine teeth (n= 64) used for roughness measurements were embedded in acrylic resin and the surface ground flat. The experimental groups and brushing protocol were the same as for the color evaluation part. Surface roughness was measured with a contact type profilometer at baseline and after the last brushing session. Kruskal-Wallis procedure tested changes in color and surface roughness among the different groups. All post-hoc comparisons were conducted with Bonferroni corrections. Tests of hypotheses were two-sided with an alpha level at 0.05. Results: Overall color change was not significantly different among groups at 1 -week post-brushing and at 1 -month follow-up. However, the hydrogen peroxide group had a significantly higher reduction in chroma in the yellow-blue axis when compared to negative control group at 30-day post-brushing and 1 -month follow-up (P< 0.05). There was no significant difference in roughness among the groups at baseline (P= 0.2973) and post treatment (P= 0.8169).