Methods: Bovine enamel slabs (4x4mm) were embedded in acrylic resin, ground flat and polished. Adhesive tapes were placed on the enamel surface, leaving an exposed area of 4x1mm. The specimens were randomly allocated into 4 experimental groups (n=8), according to the different remineralizing treatment protocols (artificial saliva flows and additives): A. fixed flow-rate: 0.5ml/min (for 60 min), modeling unstimulated salivary flow; B. variable flow-rate: 4ml/min (for 4min), 2ml/min (for 6min), 1.5ml/min (for 10min) and 1ml/min (for 40min), modeling stimulated salivary flow by gum chewing; C. variable flow-rate plus fluoride (1.5ppm) and D. variable flow-rate plus Na2HPO4 (470ppm) and KH2PO4 (125ppm). The specimens were submitted to erosion-remineralization cycles, consisting of 5min immersion in 0.3% citric acid (pH=2.6), followed by 1h of remineralization, according to the different protocols (A-D). This cycle was repeated 4x/day, for 5 days. Enamel surface loss was determined by optical profilometry, and expressed in μm. Data were analyzed with ANOVA and Tukey test, at 5% significance level.
Results: The means (SD) of enamel surface loss (μm) were: A: 8.14 (1.15)b; B: 8.49 (1.69)b; C: 4.92 (1.04)a; D: 4.23 (0.62)a, where different superscript letters denote statistically significant differences (p<0.05).
Conclusions: 1. Fluoride and phosphates were able to reduce enamel erosion lesion development; 2. The experimental model was unable to differentiate erosive lesion progression between the fixed and variable flow rates.