[Comparative study of two novel nickel-titanium instruments for root canal preparation in curved canals on shaping ability and microcrack formation].

ABSTRACT

PURPOSE: To evaluate the shaping ability and microcrack formation of ProTaper Next (PTN) and XP-endo Shaper (XPS) systems in the mesial curved root canals of mandibular molars by using micro-CT scans. METHODS: Sixteen mandibular molars with two independent mesial root canals and curvature ranging from 25° to 35° were randomly divided into two groups. The preparation time was recorded. Pre-and-postoperative images were scanned by micro-CT. The following parameters were evaluated canal transportation, centering ratio, changes in canal volume, canal/root width ratio and microcrack formation. SPSS 22.0 software package was used to analyze the data. RESULTS: Significant difference (P＜0.05) was found for canal transportation at the section of 1, 3, 5, 7 mm from the apical foramen and centering ratio at the section of 1, 3, 7 mm from the apical foramen, where XPS files were superior. There was no significant difference for centering ratio at the section of 5 mm from the apical foramen(P＞0.05). XPS groups significantly consumed less time during the preparation(P＜0.05). There was no significant difference between the two groups for the increase amount of volume, and canal/root width ratio(P＞0.05). Both instruments did not induce new microcrack after preparation. CONCLUSIONS: PTN and XPS can both shape curved canals effectively and safely. XPS showed better centering ability and reduced preparation time during preparation.