In vitro evaluation of different remineralization periods in improving the resistance of previously eroded bovine dentine against tooth-brushing abrasion.

One dentine specimen was prepared from each of 90 bovine incisors. The samples were then evenly distributed among nine groups (A-I) and submitted to 10 alternating de- and re-mineralization cycles, including abrasion by tooth brushing. Each cycle started with a demineralization using the erosive soft drink Sprite Light for 1 min, followed by storing the samples in pooled human saliva for a total of 240 min. The specimens were removed from the saliva at different intervals (group A, 0 min; B, 15 min; C, 30 min; D, 45 min; E, 60 min; F, 90 min; G, 120 min) and brushed in an automatic brushing machine. Groups H (erosion, but no brushing) and I (no erosion, but brushing), which were also stored in saliva for 240 min, served as controls. After these cycles, loss of dentine was determined by profilometry, producing the following values (mean+/-S.D.), which were analysed statistically (P< or = 0.05): group A (5.03+/-1.49 microm), B (4.44+/-1.09 microm), C (4.91+/-0.95 microm), D (5.47+/-1.52 microm), E (5.29+/-1.45 microm), F (4.76+/-0.74 microm), G (5.16+/-0.71 microm), H (2.61+/-1.31), I (1.11+/-0.39). Groups A-G had no significant differences, but they showed a significantly greater loss of dentine than groups H and I. It is concluded that the abrasion resistance of eroded bovine dentine is still decreased after a remineralization period of 120 min.