Fatigue susceptibility of an endodontic fibre post material.

AIM: To evaluate effects of ageing and fatigue on the elastic modulus and short-beam shear strength of a quartz fibre/epoxy resin post material. METHODOLOGY: Cylindrical specimens (25 × 2.2 mm) were made. Elastic moduli were dynamically measured before immersion in water; after immersion in water; periodically during storage in water for up to 7 years; periodically during thermal cycling in water for up to 10 000 cycles to produce thermo-mechanical fatigue; and periodically during boiling in water for up to 100 h. After ageing, the specimens underwent short-beam shear strength testing. RESULTS: Elastic modulus was significantly decreased by thermal cycling and by immersion in boiling water, but not by water storage. Short-beam shear strength was profoundly decreased by all three ageing processes. Short-beam shear strength was much more sensitive than elastic modulus to the ageing or fatigue processes applied in this study. CONCLUSIONS: A representative endodontic fibre post material was susceptible to a variety of ageing and fatigue processes. The effects of ageing and fatigue had a more pronounced impact on short-beam shear strength than on elastic modulus. The effects of boiling in water and thermal cycling in water were considerably larger than those of simple storage in water.

Modeling capacity of ENDOflash files in simulated root canals.

With the development of rotary nickel-titanium files and their applications in Endodontics, the concepts of root canal preparation have changed. The objective of this research is to evaluate the transportation of simulated root canals caused by stainless steel ENDOflash rotary files compared to nickel-titanium ProFile files (.04, .06 and Orifice Shapers). Twenty-four simulated root canals with a 30 degrees curvature were randomly divided into 2 groups and prepared with ENDOflash or ProFile files according to manufacturers' instructions. Comparison between the simulated root canals before and after instrumentation showed significant differences (p < 0.001) between the groups, with greater transportation observed with ENDOflash files. One case of deformation was observed with a ProFile instrument (#20/.04) and there were no fractures.