| Inferior alveolar nerve, originated from the mandibular division of Trigeminal (V)nerve, enters the mandibular canal through the mandibular foramen. Mandibular canal isadjacent to the apical of mandibular premolars and molars, so there are often some risks ofinjurying the inferior alveolar nerve when involving clinical treatments of these teeth.Understanding the accurate anatomy of the mandibular canal is essential for dentalpractitioners to avoid potential injuries during surgical procedures around posterior molarsregion. Before the advent of Cone Beam Computed Tomography (CBCT), clinically weuse panoramic radiograph to study the anatomical of mandibular nerve canal. However,the accuracy of the study needs to be improved because of the defects like structureoverlay, amplification errors, image distortion and so on. The clinical application of CBCTovercomes these defects and makes the dental diagnosis and treatments more accurate andeasier. It is a mandibular canal evaluation techniques with good prospect.ObjectiveBy implementing the CBCT radiology techiques, the present study is designed todetermine the accurate position of the mandibular nerve canalin the mandible, includingthe thicknessof buccal and lingual surfaces of the mandible, the vertical distance frommandibular nerve canal to alveolar bone crest and inferior border of mandible and therelationship between apical root of posterior teeth and mandibular nerve canal. Thus wecan provide a reference to determinethe safe site and distance during oral surgicalprocedures, to evaluate the implanting site during implantation and to choose the implant.Methods210CBCT imaging data were from Stomatology Center, Shenzhen People’s Hospital/Second Clinical Medical College of Jinan University from December2010to December2013. By using the NNT Viewer image analysis software, we measured the distances fromthe mandibular nerve canal to the alveolar crest, the inferior border of mandible and theapical root of posterior teeth, the thickness of the mandibular lingual and buccal bone andthe location of mental foramen. Results1. The maximum distance from mandibular canal to the alveolar crest is in the secondpremolar region(26.40mm), and the minimum in the second molar region(8.70mm);The maximum distance from mandibular canal to the inferior border of mandible is inthe second molar region(12.30mm), and the minimum in the first molar region(4.20mm). The maximum/minimum/mean distance from mandibular canal to alveolarcrest of the second premolar region, first molar region and second molar region is26.40mm/14.00mm/18.11±1.63mm,26.10mm/12.50mm/17.40±1.75mm and22.70mm/8.70mm/15.34±1.99mm respectively.2. The superior wall of mandibular canal is closest to apical root of second molar, andfurthest to mesial root of first molar. The maximum/minimum/mean distance from themandibular canal to the apical root of teeth in the second premolar region, first molarregion and second molar region is11.10mm/1.70mm/5.90±1.18mm,9.80mm/2.50mm/(mesial root:5.95±1.15mm, distal root:5.63±1.14mm) and8.00mm/0.40mm/(mesial root:3.97±1.09mm, distal root:3.21±0.96mm) respectively.3. The largest thickness of mandibular buccal bone is in the second molar region, and theminimum in the second premolar region; The largest thickness of mandibular lingualbone is in the second premolar region, and the minimum in the second molar region;The maximum/minimum/mean thickness of mandibular buccal bone in the secondpremolar region, first molar region and second molar region is9.00mm/2.00mm/5.19±1.30mm,9.40mm/2.30mm/5.99±1.61mm and11.40mm/3.00mm/7.78±1.51mm respectively.4. The distance from mental foramen to alveolar crest is significantly furtherthan thatfrom mental foramen to inferior border of mandible; The distance from mentalforamen to long axis of the first premolars is significantly further than that frommental foramen to long axis of the second premolar.Conclusion1. From second molar to second premolar, the average distance from mandibular canal toalveolar crest is15.34±1.99mm,17.40±1.75mm,18.11±1.63mm respectively,increases gradually, and the distance to inferior border of mandible first decreases(reach minimum at the first molar) and then increases. When carrying out theimmediate implant treatment, it is recommended to choose the common length implants(10mm-16mm) in the second premolar and first molar region,and chooseshort implants (≤8mm) in second molar region.2. From the second molar to the second premolar, the distance from mandibular canal toapical root of posterior teeth first increases(reach maximum at the mesial root of thefirst molar,5.95±1.15mm) and then decreases. The risk of nerve injury exists in allof the three teeth positionsduring immediate implant treatment.3. From the second molar to the second premolar, the thickness of mandibular buccalbone decreases gradually, and the thickness of mandibular lingual bone increasesgradually. When choosing the fracture retention screws,2mm screws could not causenerve damage in three teeth regions,3mm screws could not cause nerve damage onlyin the second molar region, and4mm screw could cause nerve damage in all threeteeth regions.4. Mental foramen is close to the inferior border of mandible in the vertical direction, andclose to the second premolar in the horizontal direction. |
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