| Objective:The purpose of this study is to measure the three-dimensional structure of the mandibular canal in the mandibular posterior for adult men and women with the different vertical skeletal patterns by using cone-beam computed tomography (CBCT), in order to find the difference of the mandibular canal in the mandibular, which can provide reference for the clinical medicine, that would avoid to hurt the inferior alveolar nerve and the inferior alveolar vessels.Materials and Methods:From December2011to February2013,45female and45male patients with CBCT examination were chosen from the patients who have all the teeth in the mandible accepted the cone-beam computed tomography (CBCT) in Department of Orthodontic of school of Stomatology of Shandong University, aged from19to40years old,{get rid of the patients who have serious malocclusion, hemifacial atrophy, mandibular trauma, tumor, one or two branchial arch syndrome, surgical orthodontic surgery treatment; excluding the adult retained deciduous teeth; eliminate the effect of skeletal function and development of diseases, such as rheumatoid arthritis; exclusion of periodontal diseases, such as periodontitis resulted in resorption of alveolar bone height reduction, excluding mandible molar metal restorations.},which were divided into3groups according to the mandibular plane [2], the ratio of between the posterior face height and the anterior face height (the male patients:15in the high-angle group,19in the average-angle group,11in the low-angle group; the female patients:14in the high-angle group,20in the average-angle group,11in the low-angle group).The measurements included:(1) the distance between the upper edge mandibular canal and the alveolar crest of each molar tooth(MA);(2)the distance between the lateral border inferior alveolar canal and the buccal cortex of mandible (MB);(3) the distance between the interior border of inferior alveolar canal and lingual cortex of the mandible (ML). Each distance measure3times and the mean value were recorded. All the measure datas of the subject investigated are analysed by the means of SPSS16.0. The statistical methods used in this study are One-way AN OVA and multiple comparisons between groups (LSD), Paired T-test, Pearson correlation analysis, which used to compare the differences of the MA, MB and ML between different vertical skeletal pattern adults, and determine the correlation of these parameters with the vertical skeletal pattern.Results:l.In different gender(male and female), datas of the distance between the upper edge mandibular canal and the alveolar crest of each molar tooth(MA), the distance between the lateral border inferior alveolar canal and the buccal cortex of mandible (MB) and the distance between the interior border of inferior alveolar canal and lingual cortex of the mandible (ML) showed little difference, which was not significantly different.(P>0.05).2.Measurement results of left or right mandile was obtained separately, however, there was no statistical significance between the two sides(P>0.05). Datas of left mandible that related to mandibular canal are as follows (unit/mm).3.Among different vertical facial types, the distance between the upper edge mandibular canal and the alveolar crest of each molar tooth(MA):for the first premolar plane, male high-angle group,17.52; male average-angle group,18.01; male low-angle group,18.23; and female high-angle group,16.46; female average-angle group,16.53; female low-angle group,16.93. for the second premolar plane, male high-angle group,17.96; male average-angle group.18.43; male low-angle group,19.07; and female high-angle group,17.16:female average-angle group.17.53; female low-angle group,18.23. for the firs molar plane,male high-angle group,17.56; male average-angle group,18.35; male low-angle group,19.10; and female high-angle group,16.84; female average-angle group,17.71; female low-angle group,18.11.for the second molar plane,male high-angle group,16.23; male average-angle group,17.54; male low-angle group,18.32; and female high-angle group,15.93; female average-angle group,16.81; female low-angle group,17.21.From here we see that high-angle group was significantly shorter than low-angle group(P<0.05).The distance between the interior border of inferior alveolar canal and lingual cortex of the mandible (ML):for the first premolar plane, male high-angle group,4.22; male average-angle group,4.64; male low-angle group,5.04; and female high-angle group,4.17; female average-angle group,4.58; female low-angle group,5.01. for the second premolar plane, male high-angle group,4.82; male average-angle group,5.04; male low-angle group,5.21; and female high-angle group,4.66; female average-angle group,4.98; female low-angle group,5.14. for the firs molar plane,male high-angle group,2,12; male average-angle group,2.27; male low-angle group,2.44; and female high-angle group,2.08; female average-angle group,2.25; female low-angle group,2.38. for the second molar plane,male high-angle group,1.58; male average-angle group,1.72; male low-angle group,1.96; and female high-angle group,1.48; female average-angle group,1.67; female low-angle group,1.90. Those show no statistical significance between high-angle and low-angle group,either(P>0.05).While the distance between the lateral border inferior alveolar canal and the buccal cortex of mandible (MB)::for the first premolar plane, male high-angle group,1.13; male average-angle group,1.35; male low-angle group,1.74; and female high-angle group,1.12; female average-angle group,1.28; female low-angle group,1.64. for the second premolar plane, male high-angle group,4.82; male average-angle group,5.21; male low-angle group,5.64; and female high-angle group,4.62; female average-angle group,4.88; female low-angle group,5.24. for the firs molar plane,male high-angle group,6.48; male average-angle group,6.76; male low-angle group,7.28; and female high-angle group,6.26; female average-angle group.6.62; female low-angle group,7.18. for the second molar plane.male high-angle group,5.46; male average-angle group.5.96; male low-angle group,6.52; and female high-angle group,5.36; female average-angle group,6.01; female low-angle group.6.44.Those show high-angle group had no significant difference compared to low-angle group (P>0.05).Conclusion: 1. The distance between the upper edge mandibular canal and the alveolar crest of each molar tooth(MA) decreased from the mandibular pemolar to the posterior segment.whether the gender or vertical skeletal pattern.2.In molar segment, with the englargement of mandibular plane angle(FH-MP angle),that is,from the low-angle to high-angle, the distance between the upper edge mandibular canal and the alveolar crest of each molar tooth(MA) decreased,which reveals that there is a significantly negative relationship between FH-MP angle and MA.Thus it can be seen, high-angle patients facing higher risk in certain oral therapies, such as dental implant surgery and bone anchorage implant, while the mandibular canal of high-angle patient are more easily impaired. |
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