Natural head position and lower incisor irregularity: Is there a relationship?

The aim of this study was to assess the relationship between dynamic measurements of natural head position (NHP) and lower incisor irregularity to identify potential gender differences.

A total of 103 plaster models and dynamic NHP measurements were taken from 51 male (mean age: 14.20 ± 2.51 years) and 52 female (mean age: 15.02 ± 2.67 years) subjects. The dynamic NHP data were gathered by using an inclinometer device and a portable data logger. Lower incisor irregularity was measured with Little's irregularity index. The Mann-Whitney U and Kruskal-Wallis rank tests were used at a significance level of p < 0.05. To evaluate the correlation between NHP and lower incisor irregularity, Spearman correlation coefficients (r) were calculated.

There were significant gender differences in the sagittal measurements of NHP (p = 0.031) and incisor irregularity (p = 0.023). A Kruskal-Wallis test revealed no significant difference in NHP measurements between subjects presenting different levels of irregularity. Females displayed no significant correlation between incisor irregularity and any NHP measurement. However, in the males high correlation coefficients between incisor irregularity and sagittal NHP measurements (r = 0.369; p = 0.008) were noted.

Significant correlations between lower incisor irregularity and sagittal NHP measurements in males were observed. Females had a more forwardly inclined NHP than males. Moreover, male subjects displayed greater incisor irregularity than female subjects.