A Cone-Beam Computed Tomographic Study on Mandibular First Molars in a Chinese Subpopulation

Xin Zhang,Xinyu Chen,Songhe Yan,Yue Ma,Fang Wan,Ting Han,Yating Lu,Yan Wang,Shijiang Xiong,Gwendolen Reilly

doi:10.1371/journal.pone.0134919

Abstract

The purpose of this study was to conduct a cone-beam computed tomographic (CBCT) investigation on the root and canal configuration of the mandibular first molars, especially the morphology of the disto-lingual (DL) root, in a Chinese subpopulation. A total of 910 CBCT images of the mandibular first molars were collected from 455 patients who underwent CBCT examinations as a preoperative assessment for implants or orthodontic treatment. The following information was analyzed and evaluated: tooth position, gender, root and root canal number per tooth, root canal type of the mesial root(s) and distal root(s), angle of the DL root canal curvature, distance between two distal canal orifices in the teeth with DL root, and angle of disto-buccal canal orifice–disto-lingual canal orifice–mesio-lingual canal orifice (DB-DL-ML). Most of the mandibular first molars (64.9%, n = 591) had two roots with three root canals, and most of the mesial root canals (87.7%, n = 798) were type VI. The prevalence of the DL root was 22.1% (n = 201). The right side had a higher prevalence of DL root than the left side (p<0.05). Additionally, the curvature of the DL root canal were greater in the bucco-lingual (BL) orientation (30.10°±14.02°) than in the mesio-distal (MD) orientation (14.03°± 8.56°) (p<0.05). Overall there was a high prevalence of DL root in the mandibular first molars, and most of the DL roots were curved in different degrees. This study provided detailed information about the root canal morphology of the mandibular first molars in a Chinese subpopulation.

Highlights

Comprehensive knowledge of root and canal morphology is fundamental for successful root canal treatment
One mandibular first molar had a C-shaped root morphology, which was excluded in the following evaluations
Three roots with four root canals were found in 21.8% (n = 198) and 109 mandibular first molars had two roots with four root canals, representing 12.0% of the sample

Summary

Introduction

Comprehensive knowledge of root and canal morphology is fundamental for successful root canal treatment. The complexity of the root canal system determines the difficulty of root canal treatment. The omission of root canals may leave microorganisms and infectious pulp tissue untouched, which could cause post-treatment disease [1]. The mandibular first molar is the most susceptible to caries and the most frequent to undergo root canal treatment. Studies about the root and canal morphology of mandibular first molars have never ceased [2,3,4,5,6,7,8,9]. A review about mandibular first molars with disto-lingual roots reported an average frequency of 14.4% of the DL root [10]. The Chinese population was thought to have a relatively higher prevalence of the DL root in the mandibular first molars than others [2, 4, 5, 10, 11]

Objectives

Methods

Results

Conclusion