Measurement And Analysis Of Mandible Anatomy Morphology By Cone-beam CT

Objective:The aim of this study was to evaluate the bone anatomy morphology of mandible using cone-beam computed tomography (CBCT) and ensure the safety of dental implantation.Method:CBCT images of100patients, including57males and43females, were retrospective studied and measured. The anatomy morphology, course and the adjacency of mandibular incisive canal, mental canal, mandibular canal and submandibular fossa were observed on the three-dimensional reconstruction of the mandible. Implants of various dimensions were virtually placed into the mandibular1st and2nd molar region. Spatial relationships among submandibular fossa, mandibular canal and implant were also analyzed. All the date was analyzed by statistical package of SPSS17.0software.Results:1. On CBCT images, the identification rate of incisive canal was94%,54%of which were clear, the identification rate of mental canal was100%,94%of which were clear.2. The vertical position of incisive canal in mandible was in the lower1/3, while the labial-lingual position was in the middle1/3. The distances between incisive canal and the alveolar crest at different mesial-distal position (starting point, canine, middle incisor) were as follows:14.3±4.16mm,16.5±3.78mm,17.2±5.01mm, between incisive canal and the inferior border of the mandible were9.2±2.06mm,8.4±1.74mm,7.9±1.98mm, between incisive canal and the labial side were3.7±1.43mm,4.6±1.56mm,4.7±2.11mm, between incisive canal and the lingual side were6.1±1.88mm,5.7±1.17mm,5.9±2.14mm. When the tooth was missing, the distances between incisive canal and the alveolar crest were11.7±3.95mm,13.4±4.0mm,13.9±4.89mm, between incisive canal and the inferior border of the mandible were9.1±1.89mm,8.3±2.03mm,7.9±1.57mm, between incisive canal and the labial side were3.7±1.67mm,4.4±1.88mm,4.6±1.93mm, between incisive canal and the lingual side were5.2±2.03mm,5.0±1.96mm,4.8±2.47mm.3. Most mental foramen is located below the second premolar. The distances from mental foramen to incisive canal starting point, the alveolar crest, the superior border of mandibular canal were3.7±1.31mm,13.2±1.43mm,3.9±1.21mm in the left side and3.5±1.64mm,12.9±1.97mm,4.1±0.96mm in the right side respectively.4. The vertical position of mandibular canal in mandible was in the lower1/3, while the labial-lingual position was in the lingual1/3.5. The depth of Submandibular fossa in the1st molar region was1.0±0.61mm, and in the2nd molar region was1.5±0.61mm. When the lingual plate was perforated, the normal length of implant in the1st molar region was19.7±3.75mm(d=4mm) and18.6±3.73mm(d=5mm), and in the2nd molar region was16.2±3.46mm(d=4mm) and15.2±3.09mm(d=5mm). When the molar was missing, the length of implant in the1st molar region was17.1±3.77mm(d=4mm) and15.6±3.85mm(d=5mm), and in the2nd molar region was14.2±4.05mm(d=4mm) and13.2±4.27mm(d=5mm).Conclusions:This study analyzed the anatomy morphology of mandible by CBCT, the results showed that:1. The CBCT images can better show the structure, course and the adjacency of mandibular incisive canal, mental canal, mandibular canal and submandibular fossa.2. The vertical position of incisive canal in mandible was in the lower1/3, while the labial-lingual position was in the middle1/3.3. The vertical position of mandibular canal in the molar region was in the lower1/3, while the labial-lingual position was in the lingual1/3.4. Anatomy morphology of Submandibular fossa differs in individuals. The submandibular fossa is the primary limiting factor of implant length, followed by the mandibular canal when dental implants were placed in the molar region (particularly in the2nd molar region).