Mandibular growth in untreated Class I malocclusion

Objective To investigate the characteristics of mandibular growth in untreated Class Ⅰ malocclusion subjects.Methods The sample consisted of 909 subjects with Class Ⅰ malocclusion who were divided into six groups according to their gender and CVM(cervical vertebral maturation).The length and height of mandible were measured from their cephalograms.The data were analyzed by SPSS18.0.Results SNB angle and SND angle increased in all groups,but no statistically significant difference was found.During the stage of CS1-CS2,Co-Go,Go-Gn,Co-Gn increased by 3.54 mm,3.86 mm and 6.46 mm in males,and in females Co-Go,Go-Gn,Co-Gn increased by 3.42 mm,2.94 mm and 5.94 mm,respectively,and all of them showed statistically significant difference.During the stage of CS3-CS4,Co-Go,Go-Gn,Co-Gn also showed statistically significant increment in males and females,the average value were 3.70 mm,4.27 mm and 6.22 mm in males,3.00 mm,1.73 mm and 3.69 mm in females.The average value of ANS-Me increased from CS1 to CS4,but after CS4 it grew slowly in females.Conclusions The length of mandible had greatest growth in CS1-CS2 and CS3-CS4 in both males and females.The mandibular body length increased significantly from CS1 to CS4.Anterior facial height increased in the earlier stage.Because the posterior facial height increased faster than anterior facial height,the average value of mandibular plane angle decreased.\r\n\r\nKey words: \r\nClass Ⅰ malocclusion; Mandibler; Growth