Study of bond strength of one-piece glass fiber posts-and-cores with flared root canals in vitro

Abstract

To compare the effects of three kinds of fiber posts (CAD/CAM one-piece glass fiber posts-and-cores, prefabricated glass fiber post and light curing plastic fiber post) on the bond strength of flared root canals and the effect of thermal cycling on their bond strength. Extracted human single teeth (n=90) were endodontically treated and randomly divided into three groups (n = 30 each). The teeth were restored by three kinds of fiber post: CAD/CAM one-piece glass fiber posts-and-cores, prefabricated posts and light curing plastic fiber post. Following post cementation, the specimens were stored in distilled water at 37 °C for 7 days. Half bonded specimens of each group were submitted to thermal cycling (6 000 times, 5 to 55 °C) prior to micro-push-out bond strength test. Fabrication of micro-push-out bond strength test specimens was conducted by precision slicing machine. The micro-push-out bond strength was tested using a universal testing machine, and the failure modes were examined with a stereomicroscope. In CAD/CAM one-piece glass fiber posts-and-cores group, the bond strength of cervical, middle and apical was (9.58±2.67) MPa,(8.62±2.62) MPa,(8.21±2.48) MPa respectively before thermal cycling, and after thermal cycling the bond strength of cervical, middle and apical was (8.14±3.19) MPa,(6.43±2.47) MPa,(6.45±3.20) MPa respectively. In prefabricated posts group, the bonding strength of cervical, middle and apical was (3.89±2.04) MPa,(4.83±1.23) MPa,(4.67±1.86) MPa respectively before thermal cycling, and after thermal cycling the bond strength of cervical, middle and apical was (6.18±1.61) MPa,(5.15±1.94) MPa,(6.39±2.87) MPa respectively. In light curing plastic fiber post group, the bond strength of cervical, middle and apical before thermal cycling was (4.05±2.41) MPa,(1.75±1.70) MPa,(2.60±2.34) MPa respectively, and after thermal cycling the bond strength of cervical, middle and apical was (5.04±2.72) MPa,(1.96±1.70) MPa,(1.34±0.92) MPa respectively. Postal types and root canal regions were found to significantly affect the push-out bond strength. Compared with the other two groups, the one-piece glass fiber posts-and-cores had the highest bonding strength in the cervical, middle and apical. Temperature cycling has no significant effect on the micro push-out bond strength of three kinds of fiber posts. One-piece glass fiber posts-and-cores has better bonding strength and excellent bonding performance.