| Objective:In recent years, the techniques of dental implants and orthognathic surgery are extensively developing. It is extremely important for familiar with the feature of mandibular canal and its branches, which could improve the surgery’s chance of success and prevention of complications. Pyramidal tract CT(Cone-beam Computed Tomography, CBCT) for oral cavity special with high resolution and three dimensional imaging effect, can clearly show the anatomical feature of mandibular canal, mental canal and mental foramen. The aim of this project is to investigate the feature of nerve canal in mandibular canal and its branches by measuring three-dimensional structures and relations to surrounding tissues of mandibular canal using CT. This study may provide some guidances for mandibular teeth extraction, implantation surgery and evaluation.Methods:We randomly selected 100 cases with maxillary CBCT in Hebei Medical University of stomatological hospital during March 1, 2011-December 1, 2012, including 50 patients with men and women, respectively. Inclusive criteria: ①the range of age of patients was 25-45 years old, with a mean age of 32.6 years old, ②the completion of the dentition for ipsilateral molars in mandibular, ③no history of orthodontic and orthognathic treatment, ④as being in good health. The patients sat up straight, head of sagittal plane vertical to the ground, the orbital plane parallel to the ground, and fixed head; The image data was collected by CT, The three-dimensional structures and relations to surrounding tissues of mandibular canal were analyzed by surface and coronal imaging with Invivo5 software interface. The mandibular on each side was partitioned in turn: the first premolar area, the second premolar area, the first molar area, the second molar area. And the distances from superior border of mandibular canal to alveolar ridge crest, inferior border to inferior margin of mandible, outer border to mandible buccal side wall and inner border to hyomandibularbone side wall were measured in these four areas for coronal scanning. The angles of mandibular canal deviating lingual and then mental canal were also measured, respectively. The mental canal was measured by coronal and horizontal imaging, respectively. Meanwhile, the length and diameter of mental canal, the distance from beginning of it to alveolar ridge crest, and the angle between mental canal and inferior margin of mandible were measured. In addition, the feature of mental foramen was measured by 3D oblique imaging. Quantitative measurement results were expressed as mean±standard deviation from three times repeated tests and accurated to 0.02 mm.Results:The statistic analysis showed no significant difference in the measure- ment among gender or individual bilateral zone. Therefor the results were analyzed together.1 The distances from superior border of mandibular canal to alveolar ridge crest in the first premolar area, the second premolar area, the first molar area, and the second molar area were 17.54±2.44, 18.22±4.06, 16.64±2.04 and 14.48±2.35 mm, respectively; The distances from inferior border of mandibular canal in these four areas to inferior margin of mandible were 8.47±1.41, 8.65±1.28, 7.49±1.41 and 7.28±1.48 mm, respectively; The distances from outer border of mandibular canal in these four areas to mandible buccal side wall were 3.10±0.77, 3.61±1.17, 7.55±1.37 and 8.27 ±1.36 mm, respectively; The distances from inner border of mandibular canal in these four areas to hyomandibularbone side wall were 6.05±1.28, 6.98±1.47, 3.09±1.02 and 2.44±0.78 mm, respectively.2 The angle of mandibular canal in the first molar area deviating lingual and the angle between it and mental canal were 23.14°±8.28° and 101. 87°±12. 29°, respectively.3 The length and diameter of mental canal were 6.86±1.53 and 1.43±0.25 mm, respectively. The distance from beginning of mental canal to alveolar ridge crest was 18.10±2.85 mm. And the angle between mental canal and inferior margin of mandible was 41.42°±9.33°.4 There were 108(54%), 80(40%), 10(5%) and 2(1%) sides in the second premolar area, between the first and second premolar areas, between the second premolar area and the first molar area, and the first premolar area, respectively. The distances from superior border of mental canal to alveolar ridge crest and inferior border of it to inferior margin of mandible were 17.04±2.52 and 9.12±1.54 mm, respectively.Conclusions:1 Pyramidal tract CT can clearly show the anatomical feature of mandibular canal and relations to surrounding tissues.2 The mandibular canal starting from mandibular foramen was directed near lingual bone plate, deviated to inferior margin of mandible, and in the first molar area gradually deviated from lingual to buccal sides forming a certain angle with mental canal.3 The mental canal located below the second premolar area. And the existence of mental canal was 100%. |
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