relationship between hyperactivity of depressor septi nasi muscle and changes of alar base and flaring during smile

background hyperactivity of depressor septi nasi muscle leads to smiling deformity and nasal tip depression. lateral fascicles of this muscle help in widening the nostrils. the purpose of this study was to evaluate the relationship between the nasal length changes and the alar base and the alar flaring changes during smile. methods standard photographs are performed in the face and lateral views with forward gaze in the repose and maximum smile. nasal length, alar base, and alar flaring were measured on the prints of the photographs. to decrease possible errors in the size of the printed photographs, middle face height from glabella to ans was measured in the lateral view and the interpupil distance in the face view to standardize the measurements. results fifty cases were enrolled in this study. in 39 cases (78%), the nasal length was increased during smile. forty-six cases (92%) had an increase in alar base diameter during smile. alar flaring during smile increased in 48 cases (96%). nasal length and alar base changes during smiling were not significantly correlated. nasal length and alar flaring changes during smiling were not significantly related too. on the other hand, alar base and alar flaring changes during smile showed correlation. alar base and alar flaring changes during smile were not significantly different in hyperactive and non-hyperactive cases. conclusion nasal length change during smiling and hypertrophy of the medial fascicles of depressor septi nasi were not related to alar base or alar flaring change during smile.