Fatigue testing of crowned incisors restored with FRC-posts

Objectives:

The aim of the study was to evaluate the influence of fatigue and cementation mode on the fracture behaviour of endodontically-treated bovine incisors restored with crowns and fiber reincorced composite (FRC) posts.

Methods:

Forty-eight endodontically-treated bovine incisors were restored with FRC-posts (DT Light Post, VDW), composite build-ups, and full-cast crowns. In 16 teeth, each of the posts were cemented conventionally with KetacCem (3M Espe) or adhesively with Panavia F (Kuraray) or RelyXUniCem (3M Espe). One-half of the specimens in each group were subjected to thermocycling (5–55°C, x10,000) and mechanical aging (50 N, x1,200,000). Fracture resistance was determined by loading the specimens until fracture at an angle of 45 ° to the long axis of the teeth. The mean fracture loads were analysed applying the non-parametric Kruskal-Wallis test.

All samples were assessed for failure modes by visual inspection in combination with ink staining. “Favorable failures” were defined as repairable failures as fractures of the root on or above the level of bone simulation. The results were reported as descriptive.

Results:

Specimens fractured at failure loads of 371 N (Panavia F, Fatigue Testing) to 494 N (KetacCem, Fatique Testing). Comparing the different modes of cementation similar values for fracture load could be found, before fatigue testing as well as afterwards. The roots restored with conventionally-cemented posts revealed no decrease in fracture resistance after fatigue loading; but the difference between fracture loads before and after artificial aging was not statistically significant for any group.

Most specimens fractured in a favorable way; only the groups with KetacCem and RelyX UniCem showed an even distribution of fracture modes after simulated aging.

Conclusions:

The loading test showed that neither cementation mode nor fatigue testing had an influence on the load bearing capability of crowned endodontically-treated incisors with FRC posts.