Interaction between toothpaste abrasivity and toothbrush filament stiffness on the development of erosive-abrasive lesions

Abstract

Background: Toothpaste abrasivity is considered the major contributor in toothbrushing abrasive wear, while toothbrush stiffness can be considered a secondary factor that may modify the abrasivity of toothpaste. Objectives: To investigate the longitudinal enamel and dentin surface loss caused by the interaction between the abrasives in toothpaste and toothbrush filament stiffness. Study Hypothesis: The amount of enamel and dentin loss depends on the abrasivity of the toothpaste and the filament stiffness of toothbrush. Materials and Methods: The following experimental factors were considered: abrasive suspension, at two levels (L-low: Z113 and H-high: Z103); and toothbrushes at three levels determined by bristle stiffness (soft, medium, and hard) generating 6 testing groups (n = 8). Slabs of bovine enamel and dentin were cut, embedded in acrylic resin, and polished. UPVC tapes were placed on the surface of the specimens, leaving an area of 1 × 4 mm exposed in the center of the each enamel slab. Specimens (n = 8) were subjected to 5 d of erosion/abrasion cycling: erosion (5min, 4×/d, 0.3% citric acid, pH 3.75), abrasion (15 s, 2×/d, 45 strokes each, 150-g load, automated brushing machine), fluoride treatment (15 s with abrasion and 45 s without abrasion; 275 ppm F as NaF in abrasive slurry) with exposure to artificial saliva between erosion and abrasion (1h) and all other times (overnight). Surface loss (SL, in micrometers) was determined by optical profilometry, after the third and fifth days of cycling. Data were analyzed using three-way ANOVA (alpha = 0.05). For enamel, only cycling time was found to affect surface loss with 5 d > 3 d. Overall, there was little SL (mean range: 0.76 µm to 1.85 µm). For dentin (mean SL range: 1.87 µm to 5.91 µm), significantly higher SL was found for 5 d vs. 3 d, with particularly large differences for hard toothbrush high abrasive, and medium toothbrush/low abrasive. Hard toothbrush resulted in significantly higher SL than medium toothbrush for high abrasive after 5 d, with no other significant stiffness differences. High abrasive had significantly higher SL than low abrasive overall with strong effects for all combinations, except medium stiffness after 5 d. In conclusion, the interplay between abrasivity and filament stiffness appears to be more relevant for dentin than enamel.