Influence of fracture resistance of prosthesis with different thickness of ferrule restored with fiber post and resin core and crown

Abstract

Objective: To evaluate the influence of fracture resistance of endodontically treated teeth with different thickness of ferrule by mechanical fatigue test and static loading test, and so as to provide a reference for the clinical treatment planning. Methods: Fifty bovine incisors were divided into 5 groups by random number table method (n=10). Group A was the control group in which the incisors were prepared without a ferrule design (0 mm). The other four groups (B, C, D, E) were experimental groups, and the thickness of the dentin ferrule prepared for specimens in each group was 0.5, 1.0, 1.5, and 2.0 mm. The height of ferrules in all the specimens was 2 mm. Cyclic fatigue loading (2.33 Hz, 50 N) was applied on each specimen until either the specimen was dislodged/fractured or the 300 000 cycles were finished. After fatigue loading, the mode of failure was observed. Those intact specimen after fatigue loading were tested under a gradually increasing force using a universal testing machine (0.05 mm/min) until fracture occurred. The forces required to fracture and failure model was recorded. Results: The results of cyclic loading tests showed that: all specimens survived the 300 000 cycles of intermittent loading. The results of static loading tests showed that: the fracture force of A, B, C, D and E groups respectively were (226.4±67.7), (369.7±34.5), (400.7±48.2), (528.1±56.3), and (555.4±98.5) N (F=15.227, P=0.000). There was a significant difference in fracture resistance between group A and the other four groups, and between group B, C and group D, E (P<0.05). No statistical difference were found in fracture resistance among the other groups (P>0.05). There was strong correlation between the thickness of ferrule and the fracture force by Pearson correlation analysis (r=0.973, P=0.002). Conclusions: Within the limitations of this study, the following conclusions can be drawn: The different thickness of ferrule can influence the fracture resistance of the teeth, and when the height of the ferrule is 2.0 mm, the fracture force increased significantly with an increasing ferrule thickness.