Aging and thermocycling effects on adhesion of fiber posts to human radicular dentin

ABSTRACT

Aim: This in vitro study evaluated the effect of different aging periods and thermocycling on theadhesion of fiber posts to human dentin at different depths. Methods: Twenty teeth were cleaned,decoronated, and endodontically treated. After one week, root filling was removed and a 10-mmpost space was prepared. Posts (RelyX™ Fiber size 2) were cemented with a self-adhesiveresin cement (RelyX™ Unicem) and light cured. Specimens (n=4, each) were stored in 100%humidity (0 day, 7 days, 1 month, 3 months) or thermo-cycled (at 7 days, 10,000 cycles, 5-55C°,30 s). Four 1-mm-thick sections were obtained from each tooth and a push-out test was performedand results compared. Results: There was a significant difference (ANOVA p<0.05) betweenthe means of push-out test results (MPa ± SE) at different storage periods 24 hours 15.2 ± 1.4;7 days 16.8 ± 1.5; 1 month 20.3 ± 1.8; and 3 months 12.5±2.0. Shear strength was significantlydifferent (Chi-square, p<0.05) at the different slice positions. Apical sections had an increase instrength at 7 days and 1 month, but without statistical significance. The coronal section increasedsignificantly between 0 and 7 days. All sections had reduced strengths between 1 and 3 months,but only the apical sections decreased significantly (ANOVA, p<0.05). There was no significantdifference in shear strength between thermally cycled and non-cycled samples (MPa/SE 16.7±5.9, MPa/SE 16.0 ± 9.3)(p>0.05). Conclusions: Long-term storage of test samples affected thebond strength of fiber posts to radicular dentin variably, and should be considered as part of invitrotesting.