The Dentofacial Morphometry of Skeletal Class II Malocclusion with Mandibular Retrusion

• Main Authors: Yu-Chun Lin, 林昱均
• Other Authors: Hong-Po Chang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/28598246545216211997

碩士 === 高雄醫學大學 === 牙醫學研究所 === 96 === Skeletal Class II malocclusion is a facial alteration that affects about 15% ~ 20% of the population. This type of discrepancy brings about modifications in the skeletal profile and the type of mandibular retrusion is the most popular skeletal pattern in Skeletal Class II facial pattern. As to the treatment, providing a good functional occlusion and a proper esthetics is a great challenge for the orthodontist. Most results from previous researches included age as an influential factor. The craniofacial pattern changes as one grow. Therefore, a different study on non-growing patients is advantageous in providing better diagnosis and treatment clinically. Because of that, the aim of this study was to investigate the morphological characteristics of the craniofacial pattern in adults with Skeletal Class II malocclusion with mandibular retrusion. Lateral cephalograms of 80 adults with Skeletal Class II malocclusion with mandibular retrusion (∠ANB > 5°, ∠FNB < 86°) compared with 80 adults with normal occlusion. Thirty five landmarks were identified and digitized. Cephalometric analysis utilizing 30 linear, 29 angular and 4 ratios measurements were under taken. Statistical comparison of the two groups was performed with Student’s t-test, 2 way-ANOVA (adjusted by occlusion and gender) and MANOVA (adjusted by gender). The results are as follows: Multiple variations of skeletodental features were found for Skeletal Class II malocclusion with mandibular retrusion. (1) Morphometry of cranial base: The samples with mandibular retrusion had longer anterior cranial length but the internal base angle and saddle angle are not different from the normal occlusion. (2) Skeletal horizontal relationship: The samples with mandibular retrusion had longer maxillary length but the maxilla is in normal position related to the cranial base. The mandible is more retrusive and the morphology is smaller than normal occlusion but the ramus width is wider than normal occlusion may because of the compensative growth. (3) Skeletal vertical relationship: The samples with mandibular retrusion had more tilting maxillary plane, mandibular plane, ramus plane and occlusal plane. The samples had longer total anterior facial height, longer upper and lower anterior facial height and shorter posterior facial height (shorter ramus height) than normal occlusion. Otherwise hyperdivergent facial pattern was noted and the mandible was rotated clockwisely. (4) Upper and lower incisor relationship: The samples of mandibular retrusion had extrusive but normal inclined upper incisors, more proclined and extrusive lower incisors, larger inter-incisal angle, larger overjet and deep overbite. (5) Upper and Lower 1st molar relationship: In mandibular retrusion male and female had more mesial tipping and more extrusive upper 1st molars. Besides, both male and female had more mesial tipping, more retrusive and more extrusive lower 1st molars. The dentofacial characters of Skeletal Class II malocclusion with mandibular retrusion in our samples, there were not only the different size between sex but also the whole appearances. Because of that we defined there was sexual dimorphism in our samples In this study, we had not yet analyzed the geometric morphometric analysis for cranial, maxilla and mandible individually. One believes that the cognitive of individual difference will be helpful in making future diagnosis and treatment in clinically. Key words: Skeletal Class II relation, Mandibular retrusion, Cephalometric analysis