Development of a method in situ to study toothpaste abrasion of dentine. Comparison of 2 products.

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The abrasivity of toothpastes is usually determined using in vitro methods; as such, the clinical significance of the findings is uncertain. The aim of the present study was to develop and evaluate a method in situ to study abrasion of dentine by two toothpastes of different Relative Dentine Abrasivity (RDA). The study was a single blind, randomised, 2 way cross over design involving 10 healthy dentate volunteers. Subjects wore an maxillary removable acrylic appliance containing two flat human dentine specimens, taped to expose a window of tissue, from 9 am to 4 pm during the two 10 working day study periods. No food or drink was consumed when the appliance was in place. On five occasions each day, the appliances were removed and the dentine windows brushed ex vivo with the allocated paste for 60 s each. Dentine abrasion at days 5 and 10 was measured using a profilometer. Both toothpastes produced measurable abrasion in all subjects and the depth increased in most subjects between 5 and 10 days. There was significant subject and specimen variation both within and between toothpastes. There was significantly increased abrasion by the toothpaste with the higher RDA value and in mean terms the ratio of abrasion between the two pastes was similar to the ratio of the RDA values. The method in situ, already used to study dental hard tissue erosion, appears ideally suitable to study dental abrasion alone and the interaction between aetiological factors involved in tooth wear.