Toothbrushing abrasion resistance of remineralized erosive lesions

Fluoride has shown the ability to re-harden eroded dental surfaces. However, it is not known whether remineralized surfaces are more resistant to abrasion.

Objective: to test in vitro the resistance of erosive lesions remineralized in the presence of fluoride against toothbrushing abrasion.

Methods: erosive lesions were created in 24 specimens of human enamel and root dentin by immersion in grapefruit juice for 25min. They were randomly assigned to 3 testing groups (n=8): A. deionized water (negative control), B. 700 and C. 1250ppm F (NaF), and submitted to a cycling of 2min of fluoride treatment and 2h of remineralization in artificial saliva at 37°C. This cycle was repeated 2x/day for 3 days. Surface microhardness (SMH) was measured before and after demineralization and after remineralization. The remineralized specimens were submitted to abrasive challenges of 20, 50, 100 and 200 strokes in an automated toothbrushing machine (150g), using dentifrice slurry. Lesion depth (LD) changes were monitored with profilometry after the demineralization, remineralization and erosive-abrasive challenges. Data were analyzed by ANOVA, Tukey test and regression analysis (α=0.05).

Results: for enamel, after the remineralization, the SMH of A was higher than C with no differences between these groups and B; while the LD of A<B=C. After 20 and 50 brushing strokes, the LD of group C remained significantly lower than A, with B showing intermediate results. After 100 and 200 strokes, no significant differences were observed. Regression analysis showed significant increase of the LD for all groups throughout the brushing challenges. For dentin, no differences were observed among treatment groups.

Conclusions: eroded enamel remineralized in the presence of fluoride showed higher resistance against toothbrushing abrasion. This protection was dependent on the fluoride concentration as well as on the aggressiveness of the abrasive challenge. Fluoride did not affect the remineralization or toothbrushing abrasion resistance of dentin.