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:
|
Mean Enamel Wear (s.e) |
Mean Dentine Wear (s.e.) |
|||
|
Time (mins) |
10 |
20 |
10 |
20 |
|
A |
0.07 (0.02) |
0.15 (0.05) |
4.34 (0.93) |
8.69 (1.29) |
|
B |
0.07 (0.02) |
0.11 (0.04) |
5.76 (0.63) |
8.37 (1.02) |
|
C |
0.04 (0.03) |
0.09 (0.05) |
3.19 (0.19) |
4.39 (0.63) |
|
D |
0.02 (0.02) |
0.08 (0.02) |
2.70 (0.76) |
4.49 (0.82) |
|
E |
0.02 (0.01) |
0.03 (0.02) |
2.29 (0.86) |
3.77 (0.95) |
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.