Retentive bond strengths of FRC posts bonded with 4 cements

Objectives: Fiber-reinforced composite (FRC) root posts are frequently used for esthetic restorations. In this study the retentive bond strengths of FRC posts without and with additional surface conditioning and titanium posts bonded with 4 different resin cements were compared. Methods: The roots of 120 extracted, anterior teeth were investigated. All root canals were prepared for tapered posts (Erlangen system, Brasseler, size II/ 12 mm length). FRC posts (DentinPost) were inserted as manufactured (M) or with additional surface conditioning (C) (CoJet-system, Espe). Sandblasted titanium posts (Erlangen system) were used for control. Groups of 10 posts each were bonded in the post spaces using 4 resin cements (RelyX, Espe/ Superbond, Sunmedical/ Panavia F, Kuraray/ Encor D/C, Centrix). A tensile force test (Instron 1026, Mass., USA) was performed after moist storage for 24 hours and thermocycling (5 - 55 °C, 5000 times). Statistical analysis was carried out (one-way ANOVA-test, Scheffé-correction). Results: The highest retentive bond strengths of FRC posts were obtained for RelyX (M: 405±68 N, C: 476±72 N) and for Superbond, Panavia F and Encor with conditioning respectively (422±163 N/ 450±64 N/ 386±93 N). Without conditioning of the FRC posts the retentive bonding strengths decreased not significantly for Superbond, Panavia F and Encor (165±110 N/ 243±99 N/ 163±100 N). The results of titanium posts were significantly higher for Superbond (566±106 N, p<0.01) compared to the FRC posts without conditioning. The values of titanium posts remained at the same level than the values of the M- or C-FRC posts for RelyX (425±180 N) and Panavia F (457±114 N) and were found to be not significantly lower for Encor (129±48 N). Conclusions: The conditioning of FRC posts using the CoJet-System can be recommended in order to increase the retentive bonding strengths of various resin cements and to achieve comparable results to sandblasted titanium posts.