This study evaluated the preparation of root-end cavities using an ultrasonically activated file, and the obturation of such cavities. In the first part, the root canals of 40 extracted teeth were prepared to size 40 and irrigated with NaOCl and EDTA. The root ends were resected and the teeth inoculated with Enterococcus faecalis, incubated for 10 days and divided into four groups: control; saline; irrigation; hand instrumentation performed via a retrograde approach up to size 50 using saline irrigant; ultrasonic instrumentation with prebent size 40 K-flex file inserted into a Piezon Master using saline irrigant. The teeth were fixed, sectioned longitudinally and viewed under scanning electron microscopy. Bacterial and smear layer scores were obtained at 1, 3, and 5 mm from the resected end. The bacterial scores for control and saline groups were similar; the scores for each instrumentation group were significantly lower than the control group (P<0.001). In addition, there were significantly fewer bacteria in the ultrasonic group compared with the hand instrument group (P<0.001). The smear layer scores for control and saline groups were similar, and significantly lower than in either instrumentation group (P<0.001). In the second part, root-end cavities were ultrasonically prepared in 20 extracted teeth. Ten cavities were filled with amalgam, and 10 with thermoplasticized gutta-percha and Grossman's sealer. After 24-h storage, the root ends were immersed in dye for 48 h. Cross-sectional slices of the obturated part of the root were evaluated using both light and confocal microscopy for dye leakage along the interface of filling material and dentine. There were no statistical differences between the leakage of amalgam and gutta-percha root-end fillings, nor between the two methods of microscopy.

Aims: the aim of this in vitro study was to evaluate the apical sealing ability where the canals are prepaid by two rotary NiTi systems. Materials and Methods: Thirty-six extracted human teeth with single root cut there crowns at the cemento-enamel junction CEG. The working length was determined for each tooth. The teeth were divided in to (3)groups ten of each. Group I the teeth were instrumented with ProTaper NiTi then the teeth obturated with matched-taper single cone. Group II of teeth were instrumented with RaCe NiTi rotary instrument and then obturated with matched-taper single cone. Group III were instrumented by hand instruments K-files and obturated by the lateral condensation techniques. Six teeth were divided as positive and negative control group three for each one. Tgadeseal was used as root canal sealer in this study. Adye penetration method was used to evaluate the apical seal using steromicroscope at 40X magnification. One-way analysis of variance and Duncan's test were used for statistical analysis. Results: The statistical analysis of the results demonstrated that there was no statistically significant difference in Microleakge between the two different rotary instrument each ProTaper and RaCe. While there was significant difference between the rotary instrument and the Hand instrument K-files. Conclusions: The use of the NiTi rotary instrument for root canal preparation showed the least apical microleakage, in compaired with hand instrument.

Aims: The aim of this in vitro study was to evaluate the coronal seal of root canals prepared by two NiTi systems. Materials and Methods: Thirty-six extracted human teeth with single root canal were decoronated at the cemento-enamel junction (CEJ). The working length was determined for each tooth. Thirty teeth were divided into three groups ten of each. Group I teeth were prepared by Pro-Taper NiTi rotary instruments, then obturated by matched-taper single cone. Group II teeth were prepared by RaCe NiTi rotary instruments and obturated also by matched-taper single cone. Group III teeth were prepared by hand K-files instrument then obturated by gutta percha lateral condensation technique. Remaining teeth were used as control group, three positive and three negative control. Tgadeseal was used as root canal sealer for all groups in this study. Dye penetration method was used to evaluate the coronal seal using a steromicroscope at 40X magnification. All teeth (experimental group and control groups) were longitudinally sectioned for examination of dye penetration. One-way analysis of variance and Duncan's tests was used for statistical analysis. There was significant differences between the groups (p< 0.05). Results: Statistical analysis of the results demonstrated that there was no statistical significant difference in coronal seal between the two systems. While, there was a significant difference between the two rotary Ni-Ti systems and the hand K-files instrument. Conclusion: The use of Ni-Ti rotary instrument for root canal preparation shows least coronal microleakage in comparision with hand K-files instrument.