Observational Study: Preliminary Evaluation of Nostril Narrowing in Relation to Unilateral Mastication

Background: Unilateral mastication (UM), defined as the habitual use of one side of the mouth for chewing, has been linked to various craniofacial asymmetries and systemic effects. This study aims to explore the relationship between UM and nasal airway asymmetry, investigating whether a habitual chewing side correlates with a narrowed nostril. These findings provide a preliminary understanding of how chewing practices might impact craniofacial anatomy and respiratory health. Methods: A pilot study involving 24 adults aged 18 and older was conducted. Inclusion criteria excluded individuals with prior orthodontic treatment or edentulism. The habitual chewing side was determined through self-report and direct observation of chewing gum activity. Nostril dimensions were assessed using ImageJ^® 1.54 software by blinded observers. Statistical analysis, including Fisher's exact test and Kruskal-Wallis test, was performed using R version 4.4.1 to examine associations between the chewing side and nasal asymmetry. Results: Half of the participants (50%) preferred the right side for chewing. A significant association was found between the chewing side and the smaller nostril (p < 0.001). Participants with a smaller right nostril consistently preferred chewing on the right side, with a large effect size (ϕ = 0.845). No significant differences in age were observed across nostril groups (p = 0.47). Conclusions: This study reveals a strong association between unilateral mastication and nasal airway asymmetry, highlighting the potential role of chewing habits in influencing craniofacial development. These findings emphasize the need for further longitudinal studies to explore the systemic and aesthetic implications of habitual chewing patterns.