[Abstract] Objective: to determine the position of the mandibular canal in the second premolar and the first and the second molars by using CBCT in. Methods: 3 distance measuring 120 cases over 18 years old population of second premolar and the first molar, two apical position: the mandibular canal center (A) to the inferior margin of the point (B) of the distance; the mandibular canal center (A) and A points to the buccal side in the same horizontal line the point (C) of the distance; the mandibular canal center (A) and A points to the side of the tongue on the same horizontal line point distance (D). Each distance was measured in 3 groups, and the average value was measured. Results: the wall thickness of the lower edge of the mandible was the thickest in the anterior root of the second premolar. In the first molar and the two molar, mandibular bone wall, lingual bone wall, buccal bone thickening, and buccal bone thickness on the lingual wall; women and men the same rules and measurement results, the bone thickness slightly male bone wall is thin. Conclusion: the use of the 3 spatial distance to determine the normal mandibular molar and the first and two molars at the tip position in second before the orthognathic surgery of mandibular sagittal split ramus osteotomy, cyst curettage, and provide a theoretical basis for implantation etc..
Mandibular canal; molar; distance.
The position of the mandibular canal in mandibular relationship for some clinical operation, such as sagittal split ramus osteotomy, cyst curettage, has important significance for implantation, we the molar and the first and two molars at the tip position in second by CBCT before the mandibular, provide a basis for clinical operation [1].
Materials and methods:
1 survey population.
There were 60 cases of male and female in normal healthy adults with no maxillary dysplasia, no dentition defect or missing, no periodontal disease, a total of 120 cases.
2 measurement methods.
Show the staining of mandibular canal in mandibular CBCT, mandibular canal in the coronal plane to determine the center point (A) and the lower edge of the point (B), A and the buccal side in the same horizontal line point (C), and the A side of the tongue on the same horizontal line point (D) measurement of A-B, A-C, A-D between the three distance, each distance measurement of the 3 groups, the average values (Figure 1-4).
3 measurement tools.
Cone beam CT Germany slip production company, KaVo 3D eXami, 14 bit gray, 120 KV, 3-7 mA. output data is stored in a standard DICOM3. 0 CT image data.
4 statistical methods.
SPSS11. 5 software was used for descriptive statistical analysis and t test, the difference of P <0. 05 was statistically significant.
Result?
1 measurement results.
Table 60 results of coronal plane CBCT measurements of the mandibular canal to the related bone markers in males were shown in Table 1
Table 60 results of coronal plane CBCT measurements of the mandibular canal to the related bone markers in females were shown in Table 2
Through the t test statistical analysis can be found, the comparison between male and female 3 distance, the difference was statistically significant (P < 0.05). The possible reasons and human development, the male female mandibular mandible is wide, narrow. However, there was no significant difference between male and female A-B, A-C and A-D (P >0. 05)
Discussion
1 dimensional measurement of mandible.
In the past, [2] was used to measure the position of the mandibular canal in the second premolar and the first and the two molars, and most of them were made in the corresponding position of the mandible. The distance from the center of the mandibular canal (A) to the lowest point (B) of the inferior border of the mandible. The mandibular canal center (A) and A points to the buccal side in the same horizontal line point (C) of the distance; the mandibular canal center (A) and A points to the side of the tongue on the same horizontal line point (D) distance, this method is not only time consuming, but also because each point of view different, different measurement results, at the same time measured by vernier caliper, the measurement and measurement tools, measurement results will produce errors. Yang Bin [3] in the study of craniofacial measuring image in 3D CT confirmed the 3D CT images can reflect the three-dimensional craniofacial anatomy, provides a theoretical basis for the three-dimensional measurement to guide the operation. Can not provide accurate mandibular reconstruction of traditional complex structure, especially the details of the mandibular canal, in CBCT can be arbitrary angle in whole or partial reconstruction, display the mandible and surrounding anatomic relationship of [4] structure, using the measurement method is time-saving and labor-saving; due to the use of computer measurement [5], it will not affect the measurement results due to human factors this method of measurement, more scientific and practical.
Clinical significance of 2 dimensional measurement of mandible.
The measurement results can be found by men, bone wall thickness in the second premolar in the margin of the bone wall thickness, lower than the buccal and lingual bone wall thickness, the thickness of lingual bone on the buccal bone wall; in the first molar and the two molar, the bone wall were thickened by; female measurement results showed that the rules with the same male. It can be found from the mandibular first molar and the mandibular second premolar, mandibular canal from the posterior medial oblique anterolateral perforating cancellous bone openings in the mental foramen, the description and the same skin Xin [6], which for mandibular surgery to avoid injury to the inferior alveolar nerve help. Using the 3 space distance to determine the normal mandibular molar and the first and two molars at the tip position before second, for us in clinical practice such as: orthognathic surgery of mandibular sagittal split ramus osteotomy, cyst curettage, have certain reference significance for implantation etc..
[reference]
[1] Wang Xiaoju. Minimally invasive technique for mesial impacted mandibular wisdom teeth extraction effect analysis [J] Journal of medical forum, 2015,3 (9): 85-86.
[2] Li Ling, Zhang Rui, Yu Li Niu, CT tomographic images of mandible dentition three-dimensional geometry simulation based on [J], Shanghai Stomatology, 2000,15 (9): 235-236.
[3] Yang Bin, Huang Hongzhang, et al., et al.. Study on the method and principle of [J] craniofacial 3D CT system of image measurement and analysis, Journal of oral and maxillofacial surgery, 2000,10 (2): 99-102.
[4] Zhang Junqi, Wang Qing. Mandibular CBCT analysis [J]. Journal of oral and maxillofacial surgery, 2004,3 (2): 123-126.
[5] Tu Ling, Luo Yuancai, Jian xinchun. Study on the measurement of mandibular alveolar bone. [J]. Chinese Journal of Stomatology, 1994,10 (1): 7-9.
[6] Xin, chief editor. Oral anatomy and physiology [M]. fifth edition. Beijing. People's Medical Publishing House, 2005, 95