1 Associate Professor, Department of Orthodontics, Dental School, Tehran University of Medical Sciences, Tehran, Iran

2 Postgraduate student of orthodontics, Tehran University of Medical Sciences, Tehran, Iran

3 Private practice



Background and aims: Nasolabial angle is an important landmark that affects patient’s profile and also appearance of smile. This study has done to assess the relationship between skeletal and dental parameters and nasolabial angle for formulating the individual value of the angle for each patient.
Subjects and methods: Sixty healthy girls who were referred to orthodontic department of Tehran University of Medical Science were included in the study. Eight skeletal, three dental and three nasal soft tissue parameters (14 parameters) were measured on lateral cephalograms.
Results: There were no significant relationships between nasolabial angle and parameters which were analyzed, but derivatives of this angle which named FNA (Posteroinferior angle between Frankfort horizontal plane and columella of the nose) and FLA (Posteroinferior angle between Frankfort horizontal plane and upper lip) showed significant relationship with the parameters. FNA had a positive correlation with U1-Pal, U1-FH, U1-SN, SNA and SNB angles, FLA had positive correlation with SNA, SNB, U1-SN, U1-FH, U1-Pal, and SGn-SN. By means of Multiple Regression analysis for FLA angle, SNB and U1-FH, and for FNA angle, U1-PAL had significant effects. 
Conclusion: Hard tissue parameters couldn’t affect nasolabial angle, but they had an influence on its derivatives.