How to re-seal previously sealed dentin

To test different kinds of mechanical and chemical pre-treatments of previously sealed dentin before re-sealing.

75 bovine dentin samples were precycled for 3 days (per day: 6 x 1 minute erosion (HCl; pH 2.3), and kept in artificial saliva in dwell time and overnight. Group 1 samples (n = 15) remained untreated (control). Remaining samples were sealed with Seal&Protect (S&P). After thermo-mechanical loading (5,000 cycles, 50/5 degrees C, 11,000 brushing strokes) a first measurement was performed to evaluate permeability of the sealant. Permeability was tested by storing the samples in HCl (pH 2.3; 24 hours) and measuring the calcium release into the acid by atomic absorption spectroscopy. Based on these calcium release values, the previously sealed samples were allocated to four groups (2-5) according to a stratified randomization. Samples of Groups 2-5 were re-sealed with S&P after either being treated with ethanol (Group 3), silane-coupling-agent (Group 4) or sandblasting (Group 5). After re-sealing, all samples had a second measurement of permeability. After another thermo-mechanical loading, a third evaluation of permeability was conducted.

At all measurements, calcium release was significantly higher in the untreated control group than in the sealed Groups 2-5 with no significant differences among the sealed groups. Within Groups 2-5, calcium release at the first and third measurement was higher compared with that at the second measurement (P < 0.05).