RESUMO
<p><b>OBJECTIVE</b>To evaluate the microleakage of fiber post and core systems after high-speed handpiece preparation at different time points.</p><p><b>METHODS</b>The crowns of forty-five extracted human premolar were removed and the roots were endodontically treated. The samples were devided into five groups. Root canal preparation was performed on each premolar followed by fiber post cementation and core build up. Tooth preparation was applied at 5 min in group 1, at 15 min in group 2 and at 30 min in group 3 after post cementation. Five teeth with only 5 mm apical sealing were served as a positive control group, and ten with fiber post and core build-up but no coronal preparation were taken as a negative control group. Microleakage was evaluated using a fluid filtration system. The bonding interface was observed by scanning electronic microscope (SEM).</p><p><b>RESULTS</b>The microleakage was significantly increased after coronal preparation with high-speed handpiece. The negative control group has less leakage [(1.50 × 10(-6) ± 0.37 × 10(-6)) µl×min(-1)×Pa(-1)] than the groups with coronal preparation (P < 0.05); Group 1 leaked significantly more [(6.02 × 10(-5) ± 1.02 × 10(-5)) µl×min(-1)×Pa(-1)] than group 2 [(1.50 × 10(-5) ± 0.26 × 10(-5)) µl·min(-1)×Pa(-1)] and group 3 [(1.50 × 10(-5) ± 0.39 × 10(-5)) µl×min(-1)×Pa(-1)] did (P < 0.05). Corresponding to microleakage, the micro gaps between the resin cement and dentine in group 1 were wider than those in the other groups. The coronal section was wider than the apical part.</p><p><b>CONCLUSIONS</b>High-speed handpiece had negative effects on microleakage of fiber post and core systems. Coronal preparation should be performed 15 min or more after post cementation.</p>