Noboru Imura

A Comparison of Shaping Ability Using ProFile, GT File, and Flex-R Endodontic Instruments in Simulated Canals

A total of 160 resin-simulated canal blocks with 20-degree or 30-degree curvature were prepared by ProFile rotary instruments, GT rotary files, and the balanced force technique with Flex-R files. Using an image analysis computer application, the pre- and postoperative images were stored and superimposed, and then the amount of material removed from the preoperative inner and outer curved walls was measured at five levels in the apical 5 mm of the canal. The time required for canal preparation, including irrigation, and the time taken to change instruments was recorded. At 1 mm from the apical end, the directions of canal transportation were most frequently toward the outer aspect of the curvature, with the only exception being the canals shaped by the balanced force technique in which more was removed from the inner aspect. The balanced force technique required more preparation time than the rotary instrumentation.

Endodontic retreatment of thermafil or lateral condensation obturations in post space prepared teeth

The purpose of this study was to quantify the amount of remaining gutta-percha/sealer after retreatment of post space prepared teeth obturated with a lateral condensation technique or with Thermafil with plastic and metallic carrier. The time required for retreatment was also recorded. Forty-five extracted mandibular premolars were prepared using a step-back flared technique and obturated. The post space was prepared and a 5-mm obturation was left in the canal. Retreatment of all groups was done using a solvent technique. The teeth were split longitudinally and photographed. The total area of the canal and the area of gutta-percha/sealer were traced on white paper. Both areas were quantified using a computerized image analysis system and the ratio of remaining obturation material to root canal periphery was derived and statistically analyzed. Statistical analysis (analysis of variance, p = 0.01) showed no differences among the techniques when the average percentage of remaining gutta-percha/sealer was compared. Results revealed that the Thermafil metallic retreatment group consumed significantly more time than the others (analysis of variance, Scheffe p = 0.01). The metallic carriers were not easily removed from the canals, six metal carriers could not be retrieved during the retreatment routine.

Comparison of endodontic retreatment of laterally condensed gutta-percha and thermafil with plastic carriers

The purpose of this study was to evaluate canal wall cleanliness in cases of retreatment using laterally condensed gutta-percha and Thermafil with plastic carriers. Forty extracted mandibular canines were prepared using a step-back flared technique and divided into two groups: group A, obturated with lateral condensation and group B, obturated with Thermafil. AH26 was the sealer used in both groups. Retreatment of all teeth was done using Gates Glidden burs and a solvent. The teeth were then split longitudinally, photographed, and projected onto a screen at x10 magnification. The total area of the canal and the area of gutta-percha/sealer were then traced on white paper. Both areas were accurately quantified using a computerized image analysis system and the ratio of remaining obturation material to root canal periphery was derived and statistically analyzed. Results showed that the average percentage of the remaining gutta-percha/sealer was 14.23 for the lateral condensation group and 15.70 for the Thermafil group with no statistically significant difference (Students t test, p = 0.01). The plastic carrier was easily removed from the canals.

A Comparison of Mesial Molar Root Canal Preparations Using Two Engine-Driven Instruments and the Balanced-Force Technique

The purpose of this study was to compare the effects of two engine-driven, nickel-titanium instrument systems with hand files in the final shape of slight and moderately curved canals. A total of 72 mesial roots of extracted human mandibular molars were divided into three groups: ProFile .04 taper, Pow-R rotary systems, and Flex-R hand-filing technique. The roots were mounted and cross-sectioned at two different horizontal levels using a modified Bramante technique. Pre- and postinstrumented cross-sectional roots were imaged, recorded, and computer analyzed. Results showed that, at the middle third, in almost all groups, there was a tendency of cutting more toward the mesial side with only one exception: Pow-R cut more to the distal side (danger zone) (p < 0.02). At the apical third, Flex-R (p < 0.03) and ProFile (0.001) transported to the mesial side (danger zone) when the curvature increased. When the three techniques were compared analyzing each side and considering the two groups of curvature, at the middle third in the moderately curved-canal group, Flex-R cut statistically more than Pow-R toward the lingual side. The other comparisons showed no statistically significant difference. When the techniques were compared in relation with the degree of curvature, in the apical third, ProFile .04 cut statistically more toward the mesial side in the moderately curved canal group than in the slightly curved canal group. The other comparisons showed no statistically significant difference. Canal preparation time was shorter with hand instrumentation (p < .05) in a few instances.