Interaction between toothpaste abrasivity and toothbrush filament stiffness on the development of erosiveabrasive lesions in vitro

Abstract

Objectives To investigate the loss of enamel and dentin surface caused by the interaction between abrasives in toothpaste and toothbrush filament stiffness. Methods The study followed a 2 (high-level or low-level abrasive; silica) × 3 (filament stiffness; soft, medium or hard) × 2 (cycling time; 3 or 5 days) factorial design. Polished bovine enamel and dentin specimens (n = 8 each per group) were subjected to 5 days of erosion/abrasion cycling: erosion (5 minutes, four times daily, 0.3% citric acid, pH 3.75); abrasion (15 seconds, twice daily, 45 strokes each, 150 g load, automated brushing machine); and fluoride treatment [15 seconds with abrasion and 45 seconds without abrasion; 275 p.p.m. fluoride (F−) as sodium fluoride (NaF) in abrasive slurry]. Enamel and dentin specimens were exposed to artificial saliva between erosion and abrasion/F− treatment (1 hour) and at all other times (overnight). Non-contact profilometry was used to determine surface loss (SL) after 3 and 5 days of cycling. Data were analysed using three-way analysis of variance (ANOVA) (factors: abrasive/filament stiffness/time), with separate analyses conducted for enamel and dentin. Results For enamel, only ‘cycling time’ was found to affect SL, with 5 days of cycling resulting in a greater SL than 3 days of cycling. Overall, there was little SL for enamel (range: 0.76–1.85 μm). For dentin (SL range: 1.87–5.91 μm), significantly higher SL was found for 5 days of cycling versus 3 days of cycling, with particularly large differences for hard stiffness/high-level abrasive and medium stiffness/low-level abrasive. For high-level abrasive, after 5 days of cycling hard stiffness resulted in significantly higher SL than did medium stiffness, with no other significant differences according to stiffness. Overall, high-level abrasive resulted in significantly higher SL than did low-level abrasive, with strong effects for all combinations, except medium stiffness after 5 days. Conclusion The interplay between abrasivity and filament stiffness appears to be more relevant for dentin than for enamel.