The purpose of this study was to investigate influence of each file step of ProTaper® system on canal transportation.

Twenty simulated canals were prepared with either engine-driven ProTaper® or manual ProTaper®. Group R-resin blocks were instrumented with rotary ProTaper® and group M-resin blocks were instrumented with manual ProTaper®. Pre-operative resin blocks and post-operative resin blocks after each file step preparation were scanned. Original canal image and the image after using each file step were superimposed for calculation of centering ratio. The image after using each file step and image after using previous file step were superimposed for calculation of the amount of deviation. Measurements were taken horizontally at five different levels (1, 2, 3, 4 and 5 mm) from the level of apical foramen.

In rotary ProTaper® instrumentation group, centering ratio and the amount of deviation of each step at all levels were not significantly different (p > 0.05). In manual ProTaper® instrumentation group, centering ratio and the amount of deviation of each step at all levels except of 1 mm were not significantly different (p > 0.05). At the level of 1 mm, F2 file step had significantly large centering ratio and the amount of deviation (p < 0.05).

Under the condition of this study, F2 file step of manual ProTaper® tended to transport the apical part of the canals than that of rotary ProTaper®.

The purpose of this study was to analyze the stress distribution aspect of unrestored and restored combined shape (wedge shape occlusally and saucer shape gingivally) class V cavity, which found frequently in clinical cases.

A maxillary second premolar restored with a combined shape class V composite restorations were modeled using the three dimensional finite element method. Static occlusal load of 170 N was applied on lingual incline of buccal cusp at the angle of 45° with the longitudinal axis of the tooth. And three dimensional finite element analysis was taken by ANSYS (Version 6.0, Swanson Analysis System Co., Houston, U.S.A) program which represent the stress distribution on unrestored and restored cavity wall and margin.

The conclusions were as follows.

Compared to the unrestored cavity, Von Mises stress at the cementoenamel junction and line angle of the cavity base were reduced and in restored cavity.

The purpose of this study was to compare the shaping ability of the two different Ni-Ti file systems and the two different engine systems in simulated canals.

A total of four groups of each 10 were tested. Each group was instrumented with HeroShaper®and Endo-Mate2® (Group HE), HeroShaper® and Tecnika® (Group HT), ProFile® and Endo-Mate2® (Group PE), and ProFile® and Tecnika® (Group PT).

Canal preparation time was recorded. The images of pre- and post-instrumented root canals were scanned and superimposed. The amounts of increased width and centering ratio were measured and calculated at apical 1, 3 and 5 mm levels.

These data were statistically analyzed with one-way ANOVA and Duncan's multiple range test

The results of this study were as follows;

1. Canal preparation time of HT group was the shortest (p < 0.05).

2. The amount of increased canal width in HE group was significantly larger than PT group at apical 1 mm level (p < 0.05). At apical 3 mm level, PT group was significantly smaller than other groups (p < 0.05). At apical 5 mm level, PE group was significantly larger than PT group (p < 0.05).

3. The amount of centering ratio in HE group was significantly larger than other groups (p < 0.05). At apical 5 mm level, HT group was significantly larger than PE group and PT group (p < 0.05).

Under the condition of this study, torque-controlled endodontic motor is safer than no torque controlled motor, especially when the active file is used.