The Clinical Significance Of Investigating Sublingual Gland Fossa Morphous Of Adult Mandible By MSCT

Objective:In our research, we scan the sublingual gland fossa of adult mandibles by multilayer spiral computerized tomography (MSCT), survey and classify their undercut by morphous on MSCT images, measure and analyze the vertical dimension from the deepest point of the undercut to the crest of ridge, and at the same time we investigate the location distribution range of these sublingual gland fossa, then we set up normal value and threshold value of these measurement targets by side and by sex to explore the dependability and regularity of them, so we can offer a reference for tooth implantation operation at lower mandible posterior teeth area in clinical practice.Method and Materials:In our experiment, we selected 60 adult dry mandibles from anatomy department of Zhejiang University medical college,31 male and 29 female in total. Specimens with over 4 missing teeth or 2 continuous missing teeth were abandoned. To all the 60 specimens:①We survey the location distribution range of these sublingual gland fossa. ②We classified these undercuts by coronal scanning images of MSCT. GroupⅠ: sublingual gland fossa undercut is clear and evident bilaterally; GroupⅡ:sublingual gland fossa undercut is clear and evident only at left side; GroupⅢ:sublingual gland fossa undercut is clear and evident only at right side; GroupⅣ:sublingual gland fossa undercut is invisible bilaterally.③We measured the vertical dimension from the deepest point of the undercuts to the crest of ridges bilaterally,3 times each side to get the mean value. After that, we performed the test of normality for all measured data by statistics software SAS9.1, investigated the normal value and threshold value between right and left sides, also between sexes, then performed non-parametric test one by one.Results:①In all 60 specimens, GroupⅠ:38 cases (63.3%), ranging from first premolar to third molar; GroupⅡ:2 cases (3.3%); GroupⅢ:3 cases (5%); GroupⅣ:17 cases (28.3%), lingual lower mandible is curve or straight from first premolar to second molar.②The deepest points of all these undercuts localize below root tips of second premolar and first molar.③In all 60 specimens(120 sides), the data of the vertical dimension from the deepest point of the undercut to the crest of ridge show skewness distribution. P50 12.57mm and Q13.67mm at left side, P50 13.67mm and Q14.88mm at right side; P50 11.07mm and Q14.67mm at left side for male, P5013.43mm and Q14.30mm at right side for male; P50 12.87mm and Q2.43mm at left side for female, P50 13.87mm and Q3.0mm at right side for female. (For skewness distribution of all the data, central tendency (χ) and vicariance tendency (s) can not be applied to describe the data characteristic withχ±s, so percentile is adopted. P50 represents median, expressing central tendency (equal toχ).inter-quartile range Q (=P75-P25) represents vicariance tendency (equal to s)). There is no statistical significance of the data at each side regardless of sex, while there is statistical significance of the data between left and right side regardless of sex, with left data lower than right ones. Conclusion:We scan the sublingual gland fossa of adult mandibles by MSCT, survey and classify their undercut by morphous on MSCT images, measure and analyze the vertical dimension from the deepest point of the undercut to the crest of ridge, and we also investigate the location distribution range of these sublingual gland fossa. So the conclusion is as below:suitable implants such as taper implants should be selected when performing operation at mandible posterior teeth area with an evident lingual bone undercut, and it is better to use bigger diameter implants with a length less than 10mm, in addition, the axial direction of placement should also be adjusted to fully utilize the bone. Because of the anatomical variation of the sublingual gland fossa of adult mandibles, we propose that it should be safer to perform MSCT inspection and analyze the sublingual gland fossa morphous before placing implants in mandible posterior teeth area.