Qualitative Characterization of the Abrasive Component of Charcoal-Containing Toothpastes and the Effect on Dentin Roughness

Abstract

This study investigated the effect of commercially available whitening toothpastes containing charcoal on dentin. Nine charcoal-containing toothpastes were compared with 3 whitening toothpastes (positive control) and distilled water (negative control). Periodontally hopeless molars were cleaned and washed and the occlusal table removed to expose dentin. The teeth were mounted in auto-polymerizing resin and exposed dentine surfaces polished with water-cooled decreasing grits of silica carbide paper up to 1500 grit. Baseline average roughness (Ra) measurements were taken. Specimens were then mounted in an automatic tooth-brushing machine and brushed for 5000 cycles. Repeat Ra measurements were taken. Specimens were brushed in 5000-cycle increments up to 25,000 cycles with Ra measurements being taken at each time point. Between abrasive challenges specimens were stored in distilled water. All toothpaste samples were sputter coated and examined under a scanning electron microscope to qualify the shape and size of the abrasive components of the formulations. Data were analyzed using a two-way analysis of variance with post hoc Bonferroni. The results demonstrated that the abrasive effect, in terms of increasing Ra, on dentin was noted as early as 5000 cycles for all the tested toothpastes (p<0.05). The effect of continued brushing showed an overall cumulative effect on dentine roughness up to 25000 cycles. When toothpastes were compared between groups at each time-point, dentin specimens brushed with Pursito were statistically similar to the control group. At 25,000 cycles all dentin samples were significantly rougher compared to Pursito and the control groups. It may be concluded that all the tested toothpastes have an abrasive effect on dentin surfaces.