| Objective In this retrospective study of CBCT imaging data,we measured and analyzed the following parameters:the distance from the mental foramen to the alveolar crest and the lower mandibular edge,the distance from the anterior loop of the mental nerve to the buccal and lingual bone walls,and the length and height of the anterior loop of the mental nerve.We explored their relationships with the patients’ sex,side,dentition status,position of the mental foramen,and mandibular deviation to provide reference for clinicians in diagnosis and treatment.Methods We selected CBCT data from 150 patients from the CBCT database of Ninth people’s Hospital affiliated to the Medical College of Shanghai Jiaotong University between December 2020 and December 2021.The observation plane was adjusted,and each side of the mandible was observed using Mimics software.The mental nerve was classified into three types based on its direction in the bone,and the detection rate of each type and the anterior loop of the mental nerve were counted and analyzed to determine whether there were differences in sex,side,dental status,or mental foramen position.We measured the distance from the mental foramen to the alveolar crest and the lower edge of the mandible,as well as the distance from the anterior loop of the mental nerve to the buccal and lingual bone walls,and analyzed whether there were differences in sex,side,or dental status.The length and height of the anterior loop of the mental nerve were analyzed using the t-test to determine whether there were differences in sex,side,dentition status,deviation jaw,or symmetrical jaw side groups.All data were analyzed with SPSS 25.0 statistical software.Results 1.Type Ⅲ mental nerve had the highest detection rate(71.3%).There were no significant differences in sex,side,or mental foramen position(P>0.05),but the detection rate of the anterior loop of the mental nerve was significantly lower in edentulous patients than in dental patients(P<0.05).The mental foramen were mostly located under the root tips of the mandibular second premolar.2.The mean distance from the mental foramen to the alveolar crest was 12.161±1.92 mm,and the mean distance from the mental foramen to the lower edge of the mandible was 14.49±1.54 mm.These measurements did not differ significantly between sexes or sides(P>0.05).However,there was a statistically significant difference in the distance from the mental foramen to the alveolar crest between patients with and without teeth(P<0.05).3.Among 214-side mandible where the anterior loop of the mental nerve was observed,the mean distance to the buccal bone wall was 2.83±0.69 mm and the mean distance to the lingual bone wall was 6.01±1,28 mm.These measurements were not significantly different by sex,side,or dentition status(P>0.05).4.The average length of the AL was 2.48±1.10 mm(ranging from 0.125-7.375 mm),and the average height was 3.96±1.45 mm(ranging from 0.750-7.875 mm).There was no significant difference in sex,side or symmetrical mandible groups(P>0.05).However,the length and height of the AL in edentulous patients were significantly less compared to those with teeth(P<0.05).Additionally,the length of the AL on the oblique side was smaller(P<0.05),while the height of the AL did not differ significantly between oblique mandible groups(P>0.05).Conclusion 1.The detection rate of the anterior loop(AL)is not affected by sex,side,or the location of the mental foramen.However,the detection rate,length,and height of the AL in edentulous patients are lower compared to those with teeth.Therefore,surgical conditions for edentulous patients can be relaxed appropriately.2.The distance from the mental foramen to the alveolar crest is smaller in edentulous patients,while the distance from the mental foramen to the lower edge of the mandible is not significantly different in dental status.Thus,the distance from the mental foramen to the lower edge of the mandible can be used to plan surgery.3.The anterior loop of the mental nerve is closer to the buccal side.During surgery,it is recommended to place the implant slightly on the lingual side to avoid damaging the AL.Care should be taken to avoid damaging the AL during orthognathic or implant surgery.4.In patients with mandibular deviation,the anterior loop of the mental nerve on the deviated side is shorter than that on the opposite side,while the height is similar on both sides.The length and height of the AL are not different in symmetrical mandibles.Therefore,it is recommended to use CBCT before mental surgery to understand the existence of the AL and measure related indicators to prevent injury to important nerves and blood vessels.Patients with mandibular deviation should be discussed separately. |
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