Fatigue Resistance of Repaired Composite Interfaces

Objectives: The repair of defective restorations has been a well-accepted treatment modality mainly due to its tissue saving, minimal invasive nature. This study evaluated the strength and fatigue resistance of the bonded interfaces between aged and new composite as a function of adhesive resin treatment.
Methods: Three hundred beam shaped composite specimens (2x2x12) were prepared (Filtek Supreme XTE, 3M, ESPE) for four point-bending configuration and aged in water (37 ^oC) for 60 days. The twin bonded interface (TBI) specimens between the aged and new composite resin ((Filtek Supreme XTE) were prepared using different adhesives (1) iBond Universal (IB), Heraus Kulzer, (2)Futurabond U (FU), Voco, (3)Scothbond Universal (SU), 3M-ESPE. Unrepaired aged samples as well as fresh composite samples served as controls. The specimens were subjected to either quasi-static (n=10/ group) or cyclic (n=50/group) four-point flexure testing using a stress ratio of 0.1 and frequency of 4Hz to failure in hydrated conditions. The specimens were loaded until 1.2 million cycles. Data were analyzed using one-way ANOVA for quasi-static and Wilcoxon Rank Sum test for fatigue data (α=0.05).
Results: Under quasi-static loading, flexural strength of the fresh (120 ±10MPa) and aged (114±16MPa) controls were significantly higher than other groups (p<0.05). Among the universal adhesive groups SU showed significantly higher flexural strength than IB and FU (p<0.05). Similarly the fatigue resistance of the fresh or unrepaired specimens were significantly higher than repaired ones and among repaired ones, SU showed significantly higher performance than the other groups (p<0.05).


Conclusions: The fatigue resistance of the repaired interfaces were adhesive dependent and showed lower fatigue resistance than the controls.