The objective of the study was to evaluate the period of remineralization needed to re–establish the resistance of eroded enamel against brushing abrasion. Enamel specimens were prepared from 84 polished bovine incisors. The samples were evenly distributed among 7 groups (A–G) and submitted to ten alternating de– and remineralization cycles which included abrasion by toothbrushing. Demineralization was accomplished by immersing the specimens in the erosive soft drink Sprite Light^® for 1 min. Remineralization was performed by storing the samples in artificial saliva for either 0 min (A), 10 min (B), 60 min (C) or 240 min (D). After each remineralization, the specimens were brushed in an automatic brushing machine. Group E (erosion and 240 min remineralization, but no brushing) group F (erosion, but no remineralization and no brushing), and group G (brushing, but no erosion and no remineralization) served as controls. After performing the cycles, loss of enamel was determined by profilometry. The following values (mean ± SD) were obtained and statistically analyzed (p<0.05): group A (5.16±1.26 μm), B (2.47±0.68 μm), C (1.72±0.75 μm), D (1.11±0.42 μm), E (0.81±0.23 μm), F (1.04±0.31 μm), G (0.22±0.15 μm). Only the differences between groups D, E, and F were statistically not significant. Under the chosen in vitro conditions, it is concluded that abrasion resistance of eroded enamel continuously increases with remineralization time. However, even after a period of 1 h of remineralization, abrasion of previously eroded enamel is increased

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The aim of this pilot study was to measure force-related tooth mobility. Vertical and horizontal anterior tooth mobility in 31 healthy periodontal subjects was measured by a noncontact optical measurement technique. The subjects continuously increased the force on each tooth by biting on a load cell. An automated software program recorded tooth displacement at 9-N intervals. Vertical and horizontal displacements were subsequently measured. The vector of tooth mobility in the buccal direction was calculated using the Pythagorean theorem. The average displacements over all subjects for each tooth were determined. Global differences were assessed with the Wilcoxon test. There were no significant differences between contralateral teeth overall load stages. There were no significant differences in tooth mobility between the central and lateral incisors except for in the horizontal direction. However, there were significant differences between central incisor and canine and lateral incisor and canine teeth.