In this research, relapse in the lower anterior segment was examined at the patients re-called at least 6 months after the end of the retention therapy. The models of 15 patients were used in the research. All the patients were treated with Edgewise technique. Mesiodistal and labiolingual widths of the incisors were measured and ratio of mesiodistal size to the labiolingual size was calculated the amount of incisor crowding and the correlation coefficient between this and the ratio of mesiodistal and labiolingual sizes were also calculated. As a result we found an insignificant negative correlation between toohtsize and crowding. We can say that lower incisor crowding is a multifactorial process and the use of the electromyograph can be helpfull in establishing some permanent posttreatment results.

Keywords: Relaps, Lower Anterior Crowding