Erosive-abrasive tissue loss in dentine under simulated bulimic conditions.

The eroded organic dentine matrix is remarkably resistant to mechanical impacts. Additional brushing abrasion of eroded dentine has only limited influence on tissue loss. Digestive enzymes (e.g., pepsin, trypsin) that can reach the oral cavity during reflux or vomiting can partially degrade the matrix. This degradation may have an influence on both the stability of the matrix against mechanical forces and the susceptibility of eroded dentine to combined chemo-mechanical impacts. Both were investigated in the present study. Dentine samples of four groups were cyclically demineralised (6×2 min/day, 9 days) with an HCl-pepsin-solution (pH 1.6, 1.5mg/ml pepsin) and treated with a trypsin-solution (6×10 min/day, 2000 BAEE units/ml) directly afterwards. One group served as control; specimens of three groups were additionally brushed (2×15s/day) directly after the first and last trypsin treatment with forces of 200g, 300g, and 400g. Loss of demineralised and mineralised tissue was determined profilometrically. Additionally, an SEM analysis was performed. Loss of mineralised tissue (μm, mean±SD) was: 135.7±10.9 (control), 165.2±30.8 (200g), 168.0±16.3 (300g), and 174.9±17.1 (400g). Tissue loss was increased significantly (p≤0.001) by brushing independently of the force used (n.s. between brushed groups). SEM revealed that in all groups, the matrix was equally thinned through enzymatic activity, but it was still present as a continuous band. The results indicate that brushing of dentine after impact of acid and enzymes resulted in an increased tissue loss; however, the matrix persisted on the surface despite enzymatic treatment and brushing with forces of up to 400g.