Geometrical Characteristics on Anterior Loop of Inferior Alveolar Nerve in Taiwanese
摘要
Background. Anterior loop is referred to as the mental nerve running towards the mental foramen in anterior, superior, and lateral course. For dental implant surgery in mesial mandible region, the location of the anterior loop should be accurately identified to avoid the possible nerve damage. However, the current planar radiograph technique has poor visibility in the anterior loop region. Objective. The objective of this study is to investigate the geometrical characteristics on anterior loop of inferior alveolar nerve in Taiwanese with using a CT scanner. The results of the study can provide a clinical information for implant surgery in anterior mandible. Methods. 100 Taiwanese adults including 50 males and 50 females with average age of 46.7±12.6 years were chosen to perform measurement of the anterior loop. The procedures are as follows: (1) Scan the mandible region using a computed tomographic scanner. The image resolution is 0.3 to 0.4 mm. (2) Perform multiplannar reconstruction to obtain the tomographic and axial section images. (3) Identify and measure the geometrical parameters of the anterior loop. (4) Perform statistical analysis on the collected data. Result. The two important angles characterizing how the anterior loop of the mental nerve runs toward the mental foramen at the labial side were analyzed from the measured data. The first angle, the inclined angle in the lingual-labial direction, was measured as 39.1±9.8 degree. The second angle, the loopback angle in the mesio-distal direction, was measured as 25.3±14.6 degree. The loopback extension length, characterizing the distance from the mental foramen to the branch point of the anterior loop, was measured as 4.4±1.8 mm. Statistical analysis shows that there are significant difference between males and females (p＜0.05) and no difference between right side and left side (p＞0.05). Conclusion. For safety reasons, dental implant should be placed at least 5 mm anterior to mental foramen. There exists sig