Effect of ferrule and post placement on fracture resistance of endodontically treated teeth after fatigue loading

ObjectivesTo evaluate the influence of the ferrule effect (1) and the fibre-post placement (2) on the fracture resistance of endodontically treated teeth subjected to cyclic fatigue loading.Methods40 extracted single-rooted upper pre-molars were sectioned at the CEJ (groups a and b) or 2 mm above the CEJ (groups c and d), and subsequently endodontically treated. After 24-h water storage at 37 °C, specimens were restored according to four build-up approaches (n = 10 per group): (a) NF–NP (no ferrule, no post), (b) NF–P (no ferrule, fibre-post), (c) F–NP (ferrule, no post) and (d) F–P (ferrule, fibre post). RelyX Posts (3M-ESPE) were used in groups NF–P and F–P, and were cemented with Panavia F 2.0 (Kuraray). A standardized composite core was built, after which specimens were restored with an all-ceramic crown (IPS Empress CAD, Ivoclar-Vivadent) Specimens were fatigued by exposure to 1,200,000 cycles using a chewing simulator (Willytech). All specimens that survived fatigue loading were fractured using a universal loading device (Micro-Tester, Instron). A two-way analysis of variance was used to determine the statistical significance of the factors ferrule and post on fracture resistance.ResultsOnly one NF–NP specimen failed under fatigue. The ferrule effect significantly enhanced the fracture resistance of the restored teeth, regardless the use of a post (p = 0.003). F–NP obtained the highest fracture resistance (758.52 ± 121.89 N), which was not significantly different from F–P (647.58 ± 132.95 N); NF–NP presented the lowest fracture resistance (361.52 ± 151.69 N). For all groups, only ‘repairable’ failures were recorded.ConclusionsAvoiding extra-removal of sound tooth structure, rather than placing a fibre post, can protect endodontically treated teeth against catastrophic failure. However, when any ferrule can be preserved, a fibre-post may improve the retention and fatigue resistance of the restoration.