Objectives: To simultaneously measure enamel/dentine wear in vitro by different concentrations of toothpaste observed during brushing. Methods: Polished human enamel/dentine blocks (4 x 4 mm) were indented with four Knoop indents. The step across the enamel-dentine junction was measured using a contact surface profilometer. The blocks were brushed with a slurry of toothpaste (either A or B) made up to different w/w concentrations in 1% scmc solution: water (1:1) and a flat-trim toothbrush using a brushing machine for 20 minutes (150 strokes/min) and a load of 375g (n=6). After each time point the geometry of the Knoop indents and the enamel-dentine step were re-measured. Thus, enamel wear was determined from the change in the 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 (s.d.) in microns at various toothpaste concentrations (w/w) are shown in the table below.
|
0 |
14.4% |
20% |
33.3% |
50% |
65% |
80% |
|
|
Enamel Wear: A |
0.06 (0.05) |
0.03 (0.02) |
0.07 (0.01) |
0.07 (0.03) |
0.05 (0.03) |
0.11 (0.09) |
0.08 (0.06) |
|
Enamel Wear: B |
0.06 (0.05) |
0.05 (0.09) |
0.03 (0.02) |
0.08 (0.07) |
0.08 (0.07) |
0.11 (0.11) |
0.11 (0.05) |
|
Dentine Wear: A |
0.28 (0.16) |
2.94 (1.08) |
5.26 (0.87) |
10.31 (1.87) |
14.04 (0.79) |
21.81 (1.38) |
24.95 (5.80) |
|
Dentine Wear: B |
0.18 (0.16) |
1.05 (1.06) |
2.75 (0.26) |
4.23 (1.88) |
6.89 (1.93) |
10.19 (2.87) |
12.73 (2.33) |
For enamel wear, no overall significant differences between products were observed. Regression analysis was used to model dentine wear and concentration. The data fitted a straight line (R2=0.927) and there was a significant difference between products (p<0.0001). Conclusions: This study has demonstrated that the amount of dentine wear in vitro is dependent on toothpaste concentration.