Effect of cementation technique on pushout strength of fiber posts

Fiber posts have become increasingly popular for the restoration of endodontically treated teeth. The typical failure mode is at the cement/dentin interface. This may be due to the unique difficulties of performing bonding procedures within the root canal. Objective: To determine if cementation technique/material influences bond strength to root canal dentin. Methods: Forty extracted single-rooted teeth were endodontically treated, and a 13mm post space prepared. Fiber posts (UniCore, Ultradent) were cemented with four different techniques. Group 1: etch with 35% H3PO4 gel, rinse/dry with air/water syringe, adhesive primers, resin cement applied to canal with 18 mm canula (UltraEtch, PermaFlo DC, EndoEze: Ultradent), Group 2: as Group 1 except rinse/dry with a/w syringe fitted with 18 mm canula, Group 3: Self-etch primer, cement applied to post (ED Primers, Panavia F 2.0: Kuraray). Group 4: Canal cleaned with NaOCl, capsulated self-etch cement (RelyX Unicem: 3M ESPE) injected into canal with canula. After storage in water for 72 hours, the roots were cut perpendicular to the long axis into four 2mm thick sections. A push-out test was conducted by applying a load to the cement/post with a steel plunger mounted in the chuck of a universal testing machine at 0.5 mm/minute. The dimensions of the failed cement/post were measured and the bonded surface area calculated. Means were compared with two-way ANOVA and Scheffe with alpha = 0.05. Results: Mean (s.d.) bond strength (MPa): Group 2: 8.5 (1.42)a, Group 1: 6.8 (1.38)b, Group 3: 6.6 (1.85)b, Group 4: 4.8 (1.74)c. Letters with the same superscript are not significantly different. Significant effects were found for both cementation procedure and for location within root canal. In all cases the apical segment produced the lowest bond strength. Conclusions: Bonding within the root canal system is highly variable.