Influence of Bristle Stiffness of Manual Toothbrushes on Eroded and Sound Human Dentin – An In Vitro Study

Abstract

AimThe aim of this study was to determine the influence of manual toothbrushes with different bristle stiffness on the abrasivity on eroded and sound human dentin.Materials and MethodsDentin specimens were made from impacted third molars and attributed to three groups: erosion-abrasion (EA), abrasion (A) and erosion (E). The specimens from EA and E were treated with 1% citric acid (pH 2.3) for 1 min rinsed, and neutralized with artificial saliva for 15 min. This cycle was repeated five times. Thereafter, specimens from EA and A were treated with three toothbrushes types with different bristle stiffness (soft, medium, and hard) in a custom-made toothbrushing machine. The brushing was performed at a load of 3 N with a toothpaste slurry for 630 s. This procedure was repeated five times, in group EA after each erosion cycle. EA and A groups passed through five cycles with a total of 6300 strokes. The abrasivity was analyzed by contact-free profilometry. Kruskal-Wallis and Mann-Whitney U tests were performed for statistical analysis.ResultsWith respect to bristle stiffness there was no statistically significant difference in dentin loss within the EA group. In group A, a statistically significantly higher dentin loss was found for the soft in comparison to the hard bristles. No statistically significant differences were measured between soft/medium and medium/hard toothbrushes. The amount of dentin loss from specimens in the EA group was significantly higher than in the A group.ConclusionsWithin the limitations of this study, the dentin loss in the Abrasion group was higher with soft bristles than with hard ones. This result might have an influence on the toothbrush recommendations for patients with non-carious cervical lesions.

Interaction between toothpaste abrasivity and toothbrush filament stiffness on the development of erosive/abrasive lesions in vitro

“…In two previous studies of similar design 15,16 , wear of eroded dentin increased with decreasing filament diameter. However, the present data suggests that filament stiffness is likely to be a secondary factor in wear of eroded dentin, behind abrasivity.…”

“…It is often postulated that hard toothbrushes cause more wear than soft ones which has led to recommendations 4 of soft toothbrushes for patients diagnosed with erosive tooth wear 18,19 . Mechanistic laboratory studies, however, revealed the opposite as soft toothbrushes were found to accelerate the wear process because of their greater ability to carry abrasive particles across the surface 13,15,16 . Nonetheless, these studies were somewhat limited in their approach as acid challenges were mimicking intrinsic erosion 13,15 or abrasion periods were too long 16 , therefore likely exaggerating effects.…”

“…Mechanistic laboratory studies, however, revealed the opposite as soft toothbrushes were found to accelerate the wear process because of their greater ability to carry abrasive particles across the surface 13,15,16 . Nonetheless, these studies were somewhat limited in their approach as acid challenges were mimicking intrinsic erosion 13,15 or abrasion periods were too long 16 , therefore likely exaggerating effects. The present study aimed to address these shortcomings and resolve the interaction between toothbrush filaments and abrasives used in toothpastes using a clinically relevant erosion/abrasion cycling model 11,14 .…”

“…There is a multitude of individual and often additive or synergistic, but rarely mitigating, factors that may potentially impact the severity of wear of the dental hard tissues. A significant body of literature exists regarding these factors, including: the type of abrasive and its concentration; slurry viscosity; brushing force, frequency and duration; type of toothbrush and its geometry and age; filament stiffness; and the condition of the substrate as modified by the severity, duration and timing of the acid challenge and remineralisation phase [8][9][10][11][12][13][14][15][16] . Based on these data it has been postulated that the abrasivity of the toothpaste is the most important parameter that affects the abrasion process of the dental hard tissues, with the toothbrush acting as the carrier, thereby merely modifying the effects of the toothpaste abrasives 1 .…”

“…Only when combined with cycling time, the interaction became significant. Previous studies 15,16 employed stronger acid challenges, higher brushing loads and longer brushing durations than tested presently, which taken together may explain as to why prior studies were able to demonstrate filament effects. It is likely that the brushing abrasion was too mild in the present study, therefore not allowing for potential differences between filaments to be observed.…”