Measurement of Enamel and Dentine Wear by Toothpastes in Vitro

Objectives:To measure in vitro the enamel and dentine wear of a new silica whitening toothpaste and four commercial toothpastes. Methods: Polished human enamel-dentine specimens (4 x 4mm) were indented with four Knoop indents. The step across the enamel dentine junction was measured using a contact surface profilometer. The specimens were brushed with a flat trim toothbrush and a 1:1:1 slurry of toothpaste:1% scmc solution:water using a brushing machine for 10 and 20 minutes with a load of 375g. The toothpastes used were two silica whitening pastes (A and B), two standard silica pastes (C and D) and a new whitening silica toothpaste (E) (n=8). After each time point the geometry of the Knoop indents and the enamel-dentine step were remeasured. Enamel wear was determined from the change in Knoop indent depth and dentine wear was determined from the change in the enamel-dentine step, correcting for any change in enamel wear. Results: The mean enamel and dentine wear values for each dentifrice in microns are shown in the table below:

For enamel wear at both time points there were no significant differences between the products (ANOVA, p>0.05). For dentine, product E gave significantly lower wear compared to product B after 10 minutes and products A and B after 20 minutes (p <0.05 , Tukey-Kramer). Comparisons of E with C and D were not of statistical significance. Conclusion: The new silica whitening toothpaste gave a similar level of dentine wear as two standard silica formulations and was significantly lower than two commercial silica whitening products after 20 minutes brushing.