Correlation of the Upper Nasolabial Angle With Skeletal Patterns and Nasal Morphology in Indian Adults: An...

The upper nasolabial angle (UNLA) is an important determinant in clinical diagnosis and treatment planning. Therefore, the primary objective of this study was to assess the correlation between various skeletal parameters and nasal morphology in an Indian cohort, particularly UNLA. The secondary objectives were to evaluate sex differences in nasal morphology, optimal cut-off values of the UNLA for skeletal malocclusions, and differences in nasal morphology in different skeletal malocclusions.

This retrospective study used 162 pre-treatment lateral cephalometric records of patients with skeletal Class I, Class II, and Class III relationships. Group 1 consisted of 68 skeletal Class I patients (ANB angle of 2-4⁰), Group 2 consisted of 68 skeletal Class II patients (ANB angle > 4⁰), and Group 3 consisted of 26 skeletal Class III patients (ANB angle of less than 2⁰). Each group was further subdivided according to the growth pattern into low (horizontal), average, and high (vertical) growers. The angle between the sella-nasion plane and mandibular plane (SN-GoGn angle) was used to further divide the groups according to their growth pattern into a horizontal growth pattern (SN-GoGn angle < 28⁰), an average growth pattern (SN-GoGn angle of 28-36⁰), and a vertical growth pattern (SN-GoGn angle > 36⁰). The study sample was also divided into males and females to assess gender differences. Spearman's correlation coefficient, multinomial logistic regression analysis, Mann-Whitney U test, and Kruskal-Wallis tests were used. Receiver operating characteristic curves were used to obtain the optimal cut-off values for UNLA.

The UNLA showed a positive correlation with the sagittal position of the maxilla and a negative correlation with the sagittal position of the mandible and palatal plane (PP) inclination angle. Statistically significant sex differences were observed in nasal length, nasal depth, and lower anterior facial height. The optimal cut-off values for the UNLA angle in the class II skeletal pattern were ≥ 20⁰, 16-20⁰ for skeletal class I, and ≤ 16⁰ for skeletal class III patients. None of the skeletal and nasal parameters were reliable predictors of the skeletal pattern type.

The present study showed that the UNLA increased in the skeletal class II pattern with the downward inclination of the PP. Patients with skeletal class III malocclusion had an upward-canted nasal tip.