Effect of gravity and capillarity on human saliva penetration in coronally unsealed obturated root canals

The purpose of this study was to evaluate the effect of gravity and capillarity on penetration of human salivary bacteria into the entire length of obturated root canals, and to demonstrate the dye penetration configuration. Fifty single-rooted premolars were decoronated, prepared to a standardized length of 15 mm, instrumented, and randomly divided into two groups [A and B] of 25 teeth each. Each group consisted of experimental [15 samples] and negative and positive controls [five samples each]. The experimental groups were obturated with gutta-percha and root canal sealer. The positive control groups were obturated with a single cone of gutta-percha and root canal sealer. The outer surfaces [except for the apical 2 mm] were covered with two layers of nail varnish. An apparatus containing Brain Heart Infusion broth was designed, in which the teeth were placed. The samples in Group A were placed upside down, while Group B was placed normally. The coronal portions of the samples were placed in contact with fresh saliva. The number of days required for bacteria to penetrate the entire length of canals was determined. The samples were then immersed in India ink to determine the dye penetration configuration. Data were analyzed using Student's Mest. The extent of dye penetration was significantly greater in Group B compared to Group A, and they were in a pattern rather than linear form. Gravity and capillarity insignificantly affected bacterial leakage. Although gravity and capillarity did not affect bacterial penetration when applied to the coronal access of endodon-tically treated teeth, it seems that they can promote penetration of India ink into the canal after the bacterial test on the same tooth

impact of pH on cytotoxic effects of three root canal irrigants

Cytotoxicity of root canal irrigants is important due to their close contact with host tissues. This study was to assess the possible impact of pH on cytotoxic effects of MTAD, 17% EDTA, and 2.6% NaOCl on the human gingival fibroblasts using MTT assay. Human gingival fibroblasts were exposed to the irrigants and their viability was assessed after 1, 6, and 12 h. The pH of the medium was measured in each interval. Light absorption values were measured for each culture medium using Elisa Reader device. NaOCl had significantly less cytotoxicity than EDTA and MTAD. Also irrigants cytotoxicity decreased in 12, 1, and 6 h, respectively. It seems that variation of the pH resulted in variation in the cytotoxicity of solutions; i.e., it follows the pattern of the pH variation

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

comparative study between Resilon and gutta-percha as a secondary root canal filling materials: An in vitro study

Adequate root canal seal following retreatment is essential for a successful outcome. Resilon/Epiphany [R/E] obturation system has been introduced as a substitute for conventional gutta-percha/sealer method. This in vitro study compared the amount of apical microleakage of R/E with gutta-percha/AH26 [GP/AH26] sealer as secondary root canal filling following retreatment in human teeth. Fifty human single-rooted lower premolar teeth were selected. After preparing them with ProTaper rotary NiTi instruments, all the canals were obturated using GP/AH26 sealer. After 10 days, all the samples were retreated using the same rotary NiTi instruments. The samples were divided randomly into two experimental groups A and B [n=20] and positive and negative control groups [n=5]. In group A, all canals were obturated using GP/AH26 sealer and in group B all canals were obturated using R/E. After one week incubation in 37°C with 100% humidity, the amount of apical microleakage was evaluated with fluid filtration model. All the apical microleakage data were analyzed with Mann-Whitney U test Results: The mean amounts of apical microleakage were 0.317 +/- 0.287 and 0.307 +/- 0.281 microL/8min [fluid pressure=30 cm H[2]O] in experimental group A and B respectively; the difference was not statistically significant [P>0.05]. R/E seems to be a good alternative for retreatment as a secondary root canal filling material. However, Resilon/Epiphany obturation system does not completely avert microleakage