A study on dislocation of the centre of rotation in nasomaxillary complex growth and development

Abstract

ABSTRACT Purpose This study aimed to detect the centre of spiral similarity (CS), an improvement of the centre of rotation when the jaw shows standard growth, and to evaluate and examine the dislocation of CS depending on the skeletal type, sex and age. Materials and Methods This study included 107 patients aged 5–15 years (62 females and 45 males) examined at Osaka Dental University Hospital’s Department of Orthodontics for the primary complaint of malocclusion. For each patient, lateral cephalometric radiographs were taken before and after treatment. Skeletal types were classified into three groups (Class I, II and III) according to the McNamara analysis, and degrees of cervical vertebral maturation were classified into two groups (under 11 and 11 or over). We calculated CS using our previously reported method, derived the projective CS (pCS) to evaluate the dislocation of CS and compared pCS between skeletal groups. Results The CS of Class I was located approximately 17–21 mm anterior and 4–8 mm inferior to the sella. Significant differences in pCS were found between Classes I and III. Furthermore, the sign of pCS showed an opposite trend depending on sex. Conclusion The CS of ‘Class I and under 11’ is located near the spheno-ethmoidal synchondrosis, while that of ‘Class III and under 11’ was away from there in alternate directions for males and females. Our results provide insights into the trends that require different treatment strategies based on sex or other personal characteristics in orthodontics.