Effect of synthetic tissue fluid on microleakage of grey and white mineral trioxide aggregate as root-end filling materials

The success of endodontic surgery has been shown to depend partly on the apical seal. Grey mineral trioxide aggregate [GMTA] produces hydroxyapatite twice as often as white mineral trioxide aggregate [WMTA] when suspended in a phosphate buffered saline [PBS] solution. The aim of this in vitro study was to compare the microleakage phenomenon of gray and white mineral trioxide aggregates as root-end filling materials after immersion in synthetic tissue fluid [STF]. 55 single-rooted extracted maxillary anterior human teeth were divided into two experimental groups of 20 teeth each, plus 3 groups of 5 teeth each as two negative and one positive control groups. The root canals were cleaned, shaped, and laterally compacted with gutta-percha. The root ends were resected and 3 mm deep cavities were prepared. The root-end preparations were filled with GMTA or WMTA in the experimental groups. Leakage was determined using a dye penetration method. Data were analysed using analysis of variance [ANOVA] at the 0.05 level of significance. Results: The mean dye leakage was 0.40 +/- 0.1 mm for GMTA and 0.50 +/- 0.1 mm for WMTA groups, respectively. There was no significant difference between the two experimental groups [P = 0.14]. Despite the different properties and behaviours of GMTA and WMTA in STF, there were no significant differences in microleakage when using GMTA or WMTA

Cyclic fatigue resistance and fractographic analysis of RaCe and ProTaper rotary NiTi instruments

This study investigated the fatigue and fracture modes of RaCe and ProTaper rotary instruments. Fatigue resistance was evaluated by rotating the files 30° or 60° and with 2 or 5mm radius of curvature. RaCe taper 06 size 25 and ProTaper Fl files [n=40] were used. The number of rotations to failure was analyzed by two-way ANOVA and independent sample t-test. Fracture surfaces were examined under a scanning electron microscope. Both files exhibited significantly more resistance to fracture when angle severity was reduced and increase in curvature radius [P=0.000]. ProTaper demonstrated higher number of cycle of failure [P=0.0029] in one group [r=5mm, 60°]. SEM observation revealed fatigue mark/features in 17 specimens, shear characteristics in 37 samples, and tensile overload in 26 samples. Radius of curvature was the main factor in torsional and fatigue failures