LABORATORY PROCEDURES
SEPARATION
After one month, all premolars were extracted by one blinded calibrated dentist, avoiding any damage to the premolar crowns, and the teeth were stored in a 0.1% solution of deionized water with thymol crystals (pH 7.0).After root separation, each crown was mesiodistally cut under irrigation using a diamond disc and only buccal surfaces were prepared for laboratory analysis. Each half was included in epoxy resin except for a window (2 mm × 4 mm) on the buccal surface, which was the same as that exposed on the cariogenic locus. 