Effect of cyclic loading on fracture strength and microleakage of a quartz fiber dowel with different adhesive, cement and resin core material combinations.

Background: This study evaluated the performance of different adhesive-cement-core combinations coupled with quartz fiber dowels after cyclic loading and fracture strength tests and assessed the microleakage using dye penetration method. Methods: Forty maxillary canines (n=10 per group) were restored with fiber dowels (Quartz fiber DT Light Post) and four adhesive-cement-core material combinations [(Group 1: All-Bond 2+C&B (root) / All-Bond 2+Biscore (core); Group 2: All-Bond 2+Bisfil 2B (root) / All-Bond 2+Bisfil 2B (core); Group 3: Scotchbond 1+RelyX ARC (root) / Scotchbond 1+Supreme (core); Group 4: RelyX Unicem (root) / Scotchbond 1+Filtek Supreme (core)]. The specimens were initially cyclic loaded (x2,000,000, 8 Hz, 3 to 100 N at 45° under 37±3°C water irrigation) and then immersed in 0.5% basic fuchsine at 37°C for 24 hours for dye penetration and interface failure detection. The failure surfaces were observed under the stereomicroscope (x100 magnification). Circumferential and centripetal dye penetration was scored at the buccal and lingual sites. Results: Only three specimens failed macroscopically during cyclic loading. No significant difference was found among the groups for the number of resisted cycles (p=0.9). Mean fracture strength between the groups were also not statistically significant (213±63 - 245±71 N) (p=0.740) (ANOVA). All four groups showed high values of dye penetration along the restoration interfaces being not significant from each other (p=0.224) (Kruskal-Wallis). The lingual sides of the teeth where the load applied, showed significantly higher incidence of detachment between the core and the dentin (100%, 90%, 100%, 90% for groups 1, 2, 3, 4, respectively) compared to the buccal side (30%, 30%, 60%, 40%) (p=0.032, Chi-square test). In 13 specimens (32.5%) crack lines at the coronal area were observed. Fracture strength was not significantly correlated with dye penetration (p=0.1803, r=-0.2162, Linear Regression and Correlation test). Conclusion: Different combinations of adhesive-cement-composite core materials for the fiber post tested performed similar under cyclic loading and fracture strength tests.