Comparison of apical transportation in four Ni-Ti rotary instrumentation techniques.

A new radiographic technique was used to compare apical transportation in four Ni-Ti rotary instrumentation sequences. Mesiobuccal canals of 60 extracted mandibular molars were randomly divided into four groups. Groups 1 and 3 were instrumented by crown-down and groups 2 and 4 by step-back technique with 0.06 ProFiles series 29 to size 6. In groups 3 and 4 Greater Taper files were first used in a crown-down manner. The central axes of initial and final instruments were radiographically superimposed to measure loss of working length (WL) and transportation at 0, 0.5, 1, 3, and 5 mm from WL. ANOVA test showed no significant differences among groups regarding degree of transportation or loss of WL. Transportation was negatively correlated with radius of curvature at 0.5 and 5 mm from WL. The results indicate that the operational sequence of ProFiles or preinstrumentation with GT files has no effect on degree of transportation and loss of WL.

Analysis of continuous-wave obturation using a single-cone and hybrid technique.

This study analyzed the adaptation of gutta-percha to prepared root canal walls using two obturation techniques and determined the influence of the System-B plugger depth on filling adaptation. Fifty-six extracted human mandibular molars were instrumented using Profile NiTi rotary instruments, stratified based on curvature, then randomly distributed into two groups. Group 1 was obturated using the single-cone continuous-wave technique. Group 2 was obturated with a hybrid technique: lateral condensation followed by a continuous-wave down-pack. Based on System-B plugger penetration, teeth were divided into three subgroups: (a) < 3.5 mm, (b) 3.5 to 4.5 mm, and (c) > 4.5 mm. Roots were horizontally sectioned at 1 mm and 3 mm coronal to the apical foramen, stained, and photographed. Four evaluators scored the adaptation of gutta-percha to the prepared canal walls. In 100% (n = 56) of the samples, no statistically significant difference existed between the two obturation methods at 1-mm (x = 1.80, SD +/- 0.69) or 3-mm (x = 1.804, SD +/- 0.69) sections. Best results were obtained with a plugger depth 3.5 to 4.5 mm from the working length.