ABSTRACT
<p><b>OBJECTIVE</b>To analyze the push-out bond strength of fiber post and the durability of interface between dentin and composite resin during over drying and re-wetting of root canal.</p><p><b>METHODS</b>Thirty-six extracted human maxillary central incisors were randomly divided into three groups: Group A for the process of over drying, Group B for re-wetting, Group C for control. All teeth were sliced into several thin discs with thickness of 1.0 mm for micro push-out test and scanning electron microscope(SEM) observation.</p><p><b>RESULTS</b>Push-out shear strengths of fiber post immediately after bonding in group A, B and C were (5.97 ± 1.97), (7.67 ± 2.19) and (8.46 ± 2.35) MPa. Push-out strengths of fiber post two months after water storage were (2.08 ± 1.67), (2.99 ± 1.48) and (3.22 ± 1.43) MPa. There was significantly difference in push-out strength between Group A and Group B (P < 0.05). Significantly difference in push-out strength was also found between Group A and Group C. In the condition of immediate testing, there was also significantly difference between push-out strength of cervical slice and middle slice, and between cervical slice and apical slice (P < 0.05). The water storage time has significant effect on the push-out bond strength of fiber posts (P < 0.05).</p><p><b>CONCLUSIONS</b>Inappropriate condensation air blowing operation can cause extracted teeth root canal dentin over dry. Dehydration can destroy the formation of general structure of interface between composite resin and dentin. The over dry dentin can be turned back to wetting stage by water pouring, which can help fiber-reinforced composite post regain its normal retention strength and original adhesive durability.</p>