Application Of CBCT In Palatal Soft Tissue Thickness Measurement And Location Of Palatal Great Neurovascular Bundle

Objectives:1.To check the accuracy of imaging method of cone-beam computed tomography(CBCT)about the thickness of palatine mucosa by comparing with direct puncture.2.Using CBCT image data to analyze the major anatomical characteristics,location and trend of the greater palatal groove(GPG)and the greater palatal foramen(GPF),which will provide reference for safe and effective flap preparation and the distribution trend affirmation of the greater palatal neurovascular bundle in clinic.Methods:1.We included 30 periodontal healthy volunteers.Using guide plates to assist positioning,the vertical distance,which is from the midpoint of the palatal gingival margin to 3mm,7mm and 10mm was measured by CBCT imaging method and direct puncture method.This measurement range from the bilateral canine to the second molar(total of 300 dental positions and 900 sites).The consistency of the two measurement methods was analyzed by Bland-Altman image method and intraclass correlation coefficient(ICC)and the soft tissue thickness distribution also was analyzed.2.Collecting the CBCT data of 180 adults,analyzed the anatomical structure,location and distribution range of bilateral GPGs and GPFs,and explored the correlation with gender and morphology of the palatal vault morphology.Palatal vault morphology was classified according to the weight-to-width(H/W)ratio.H/W of high palatal vault morphology was over 0.04 and H/W of low palatal vault morphology was no more than 0.04.Results:1.There were satisfactory consensus between imaging method of CBCT and direct gingival penetration method.2.(1)Within canine to the second maxillary molar,palate mucosa gradually thickened from gingival margin to median palatine suture.The mean values of the palate mucosa thickness at 3mm,7mm and 10mm sites were 2.59±0.45mm,3.54±0.58mm and 4.32±0.87mm respectively.(2)Except the measurement sites in the corresponding area of the first molar,the palatal mucosa gradually thickened from canine to the maxillary molar.The mean values of the detection sites corresponding to each tooth at the specified sites were 2.92±0.61mm,3.27±0.69mm,3.60±0.85mm,3.48±1.02mm and 4.15±1.13mm respectively.At 7mm site,the first molar mucosa thickness significantly reduced(P<0.01).3.(1)Among the recruited CBCT imaging data of the 180 cases,there were concave(69.9%),concave with ridge(20.2%),biconcave(7.4%)and tubular(2.6%)imaging GPG morphology types in totally 360 cases of semi-maxillary.(2)The vertical distance value between the center point of the GPG and the midpoint tangent line of the corresponding molar enamelo-cemental junction(GPG-M)was higher in men(P<0.05)and high palatal vault morphology(P<0.05).4.(1)The rate of GPF distribution located at the center site of the third molar was 57.50%.(2)The mean value of vertical distance from GPF to midsagittal suture(GPF-MSS)was higher in men and low palatal vault morphology(P<0.05).And average distance from the central point of GPF to corresponding opposite molar enamelo-cemental junction(GPF-M)was significantly higher in men and high palatal vault morphology(P<0.05).Conclusions:1.CBCT imaging method and direct puncture method have good consistency in measuring the soft tissue thickness on the palatine side,which can be used to measure the soft tissue thickness on the palate side.2.The soft tissue of the hard palate is thicker and thicker from canine to the second molar,except for the first molar area.Following the increase of the gingival margin distance,the palatal mucosa thickens to median palatine suture.3.The average thickness of palatal mucosa from the first premolar to the second molar is over 3mm and 1 mm subepithelial connective tissue flaps is feasible in clinic.4.There are concave(69.9%)and concave with cristae(20.2%)two main GPG morphology types,and Morphology and gender of palatal vault are both related to GPG location.The shape of the palatal vault and gender of the patients were correlated with the position of GPF.5.Based on the average distance from GPG and GPF to the enamelo-cemental junction of corresponding molar is over 14mm,the flap can be obtained in this range in clinic.