A data set of proximity of mandibular third molar roots with Inferior Alveolar Canal.

OPG’s are inexpensive, low radiation and easily available in smaller dental
units and hospitals also however, a real three-dimensional picture and buccolingual relationship is unknown. Dearth of studies on third molar roots and inferior alveolar canal in Nepalese
population persuaded us to carry out this study to describe the
proximity of mandibular third molar roots to the inferior alveolar canal and nerve. A single centre cross-sectional study was designed with sample
size of 475 patients collected from July 2017 to July 2019, at
the department of Oral and maxillofacial surgery of College of
Medical Sciences and Teaching Hospital (COMS-TH), Bharatpur,
Nepal.
Ethical approval was obtained from institutional review
committee of COMS-TH. All the patients who reported the signs
and symptoms of third molar pain and difficulty were included.
Pregnant patients and those who didn’t provide consent were
excluded. Orthopantomogram (OPG) of patients were retrieved
from imaging software records. Baseline demographic data
was obtained from patient’s entry in OPG imaging software
program (Orthoralix Vixwin software) and signs of proximity
of mandibular third molar roots to inferior alveolar canal as described by Rood and Shebab were ascertained.
The seven
radiographic signs were observed on digitally magnified OPG’s
using Orthoralix Vixwin software (Gendex, USA) and presence
or absence of signs were entered. Presence of simultaneous
multiple signs were entered. Explicit prior criteria have been
used to designate each of the seven panoramic radiographic
signs as “positive” when present or “negative” when absent. All observations and demographic datas were entered
in Microsoft excel and descriptive analysis was performed with
SPSS Version 20. Frequency was used to describe presence
of radiographic signs and means were used to describe
demographic variables. Cross tabulation was done to analyse
the pattern of combination of signs. One or more radiographic signs were observed in 49.6% of mandibular third molars. Interruption of white line followed by narrowing of canal and darkening of roots was observed in
decreasing order of frequency and no statistically significant association between sex, age and side
of impacted third molar with presence of radiographic signs. Absence of any radiographic sign was observed in 245 cases
(51.6%). When only one sign was observed (n=71), the most
common sign was, interruption of white line of canal followed
by deflection of roots. The next most common pattern of combination was 3 signs (n=60) followed by two signs together
(n=55).

曲面体层摄影片（Orthopantomogram，简称OPG）具备成本低廉、辐射量低的优势，且在小型牙科诊疗设备与医院中易于获取，但该检查无法呈现真实的三维影像及颊舌向解剖关系。鉴于尼泊尔人群中关于第三磨牙牙根与下牙槽管的相关研究较为匮乏，本研究旨在探究下颌第三磨牙牙根与下牙槽管及神经的毗邻关系。

本研究为单中心横断面研究，于2017年7月至2019年7月期间，在尼泊尔巴拉特普尔市医学科学学院附属教学医院（College of Medical Sciences and Teaching Hospital, COMS-TH）口腔颌面外科招募了475名患者作为研究样本。

本研究已获得COMS-TH机构审查委员会的伦理批准。所有因第三磨牙疼痛及咀嚼困难就诊的患者均纳入研究，排除妊娠患者及未签署知情同意书的受试者。

研究人员从影像软件存档中调取患者的曲面体层摄影片（OPG）。基线人口学资料从OPG影像系统（Orthoralix Vixwin软件）的患者登记信息中提取，并依据Rood与Shebab提出的判定标准，评估下颌第三磨牙牙根与下牙槽管的毗邻征象。

研究团队使用美国Gendex公司的Orthoralix Vixwin软件，对数字化放大后的OPG影像进行阅片，记录7项放射学征象的存在与否，若同时存在多项征象亦一并录入。本研究采用既定的明确标准，将7项全景放射学征象分为“阳性”（存在对应征象）与“阴性”（无对应征象）两类。所有观察数据及人口学资料均录入Microsoft Excel表格，采用SPSS 20.0版本进行描述性统计分析：以频数分析描述放射学征象的出现情况，以均数描述人口学变量；采用交叉制表法分析征象的组合模式。

本研究中共49.6%的下颌第三磨牙观察到1项及以上放射学征象。按出现频率从高到低依次为：根管白线中断、根管狭窄及牙根暗化；性别、年龄与阻生第三磨牙的侧别与放射学征象的存在与否均无统计学显著关联。245例（51.6%）受试者未观察到任何放射学征象。当仅存在1项征象时（n=71），最常见的征象为根管白线中断，其次为牙根偏移；第二常见的征象组合为3项征象并存（n=60），其次为2项征象并存（n=55）。