ABSTRACT
After orthodontic treatment, there are several changes in soft tissue profile. Changes appear at lower anterior facial profile area, especially upper and lower lip. But there are many individual variations in the pattern of changes. So, this study was conducted to find out that the basic upper lip thickness could be one of the factors that could influence the treatment results. The samples were composed of 43 adult patients who had their 4 first premolars extracted. Groups were classified by their basic lip thickness. In group 1(thin upper lip group), there was negative relationship between mentolabial angle and lower lip change. In group 2(average lip thickness group), upper lip change was related to upper incisor change, lower incisor change, lower lip change and nasolabial angle change. And lower lip change was related to upper lip change, upper incisor change, lower incisor change. In group 3(thick upper lip group), there was no relation between both lip change and other variables.