An Evaluation of Nasolabial Angle and the Relative Inclinations of the Nose and Upper Lip

Esthetics is one of the major motivating factors for patientsseeking orthodontic treatment. Hard tissue and soft tissue drapeboth determine the facial esthetics. The structures in this regionare so variable that the nasolabial angle (NLA) has been drawndifferently by various investigators. Variations can lead toerroneous conclusions in orthodontic diagnosis. Aims and objectives: The study was done to evaluate a reliablemethod of constructing the nasolabial angle (NLA) and tocorrelate the soft tissue profile parameters with one another. Materials and Methods: Lateral cephalogram of 50 randomlyselected adult patients were taken. The tracings were madeand 10 copies of each tracing were randomly distributed to 10different orthodontists to draw the NLA. Results: Pearson’s correlation coefficient (r) showed both N/FH and L/FH angles to have significant p values when comparedwith NLA. The regression analysis showed that the nasolabialangle can be calculated for any given value of N/FH or L/FH bythe formula: NLA = 80.33° + 1.02° (N/FH) and NLA = 14.2° +1.04° (L/FH). The mean value of N/FH was 17.42° ± 8.40° andL/FH was 80.68° + 6.45° for this sample. Inter examiner reliabilitycalculated by repeated measures of ANOVA and Dahlerg’sformula showed high degree of reliability and reproducibility ofthe method. Clinical significance: NLA can be predicted for any given valueof N/FH and L/FH. NLA = 80.33° + 1.02° (N/FH) and NLA =14.2° + 1.04° (L/FH). If an individual has either N/FH or L/FH inthe normal range but not the NLA then one could calculate thecorrect NLA using this formula. Thereby the NLA can be broughtwithin the normal range by altering the other nasolabialparameters by correct treatment planning. Since the nasolabialangle plays a vital role in profile esthetics of a person, the clinicianshould place greater emphasis in evaluating this area and plantreatment mechanics to place this angle within the acceptednormal variation.