Abstract:

Objective This study aims to evaluate the nasolabial angle change and the correlation analysis of Angle’s Class Ⅱ division 1 malocclusion patients with vertical growth pattern after tooth extraction orthodontic treatment and provide experimental results to help in making orthodontic treatment plan and treatments. Methods A total of 38 Angle’s Class Ⅱ division 1 malocclusion patients with vertical growth pattern and tooth extraction orthodontic treatment were included in this study. Pre-and post-treatment cephalometric X-rays were performed, and 18 measurement items were measured. The change values of pre- and post-treatment, youngsters, and adults were compared to analyze the correlation of the nasolabial angle change. Results  The nasolabial angle between youngsters and adults was enlarged after treatment, but the nasolabial angle of the adult group changed more significantly. U1 to FH, U1 to NA, U1-NA, Spr-Ptm were reduced after treatment, and the adult group decreased more significantly. The upper lip sulcus and flange thickness, A’-Ptm, upper lip length, and nose prominence were enlarged after the adolescent treatment, but the adult had a certain degree of decrease. The difference had statistical significance. In the correlation of the nasolabial angle change analysis of the two groups, namely, U1 to FH , U1-NA and U1 to NA had significant negative correlation, significant positive correlation to the upper lip inclination angle, and more significant correlation in the adult group. Upper lip flange thickness and nasolabial angle were negatively correlated, and the upper lip sulcus thickness was positively correlated. However, no significant correlation was observed between these two in the adult group. Conclusion The nasolabial angle change of adolescents with vertical growth pattern in class Ⅱ division 1 malocclusion after extraction treatment is related to the upper anterior teeth hard tissue and upper lip soft tissue, whereas only adults and upper anterior teeth hard tissueare related.

Key words: vertical growth pattern, Angle’s Class Ⅱ division 1 malocclusion, orthodontic treatment, tooth extraction, nasolabial angle, correlation