Esthetics is one of the major motivating factors for patients seeking orthodontic treatment. Hard tissue and soft tissue drape both determine the facial esthetics. The structures in this region are so variable that the nasolabial angle (NLA) has been drawn differently by various investigators. Variations can lead to erroneous conclusions in orthodontic diagnosis.
Aims and objectives: The study was done to evaluate a reliable method of constructing the nasolabial angle (NLA) and to correlate the soft tissue profile parameters with one another.
Materials and methods: Lateral cephalogram of 50 randomly selected adult patients were taken. The tracings were made and 10 copies of each tracing were randomly distributed to 10 different 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 compared with NLA. The regression analysis showed that the nasolabial angle can be calculated for any given value of N/FH or L/FH by the 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° and L/FH was 80.68° + 6.45° for this sample. Inter examiner reliability calculated by repeated measures of ANOVA and Dahlerg's formula showed high degree of reliability and reproducibility of the method.
Clinical significance: NLA can be predicted for any given value of 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 in the normal range but not the NLA then one could calculate the correct NLA using this formula. Thereby the NLA can be brought within the normal range by altering the other nasolabial parameters by correct treatment planning. Since the nasolabial angle plays a vital role in profile esthetics of a person, the clinician should place greater emphasis in evaluating this area and plan treatment mechanics to place this angle within the accepted normal variation.