Studies in vitro of abrasion by different manual toothbrush heads and a standard toothpaste

Background: Loss of dentine at the buccal cervical region of teeth has a mu ltifactorial aetiology. However, a considerable amount of circumstantial ev idence, supported by laboratory experiments, implicates toothbrushing with toothpaste as a consistent factor. Most interest has centred around the abr asivity of toothpastes, particularly since a toothbrush alone has negligibl e effects on dentine. The influence of filament stiffness on toothpaste abr asion was the subject of some studies, mostly at least 2 decades ago, and p roduced conflicting conclusions. Numerous changes to toothbrush design and construction have taken place in recent years. Aims: The aim of this study was to measure the abrasion of a standard subst rate, acrylic, by a standard toothpaste carried on modern brands of toothbr ushes classified by manufacturers as hard (3 brands), medium (3 brands) and soft (6 brands). Method: The substrate was brushed for 20,000 strokes with at least 6 heads from each brand. Measurements of substrate loss were made at 5000 stroke in crements by profilometry. Results: Substrate loss for all brushes showed a pattern of abrasion which was to a first approximation linear. Overall, hard brushes caused least abr asion and soft brushes the most, with differences between groups being sign ificant. Within-group differences between brands reached significance for s oft and medium brushes but not hard brushes. Conclusions: The results could be explained by increased retention of tooth paste by smaller diameter filaments and denser tufts on soft brushes and th e greater flexion of filaments increasing the area of contact with the surf ace. Calculations on the clinical outcome of these data in vitro indicate t hat toothbrushing with toothpaste alone would produce minimal damage to den tine even over many years. Differences between brushes therefore are probab ly of little clinical significance. Certainly, the data do not support the use of hard brushes, particularly in view of the potential detrimental effe cts to gingival tissues.