The association of malocclusion severity and uncertainty stress with mouth-breathing behavior in adults: a cross-sectional study

This study aims to examine the associations between malocclusion severity, uncertainty stress, and mouth-breathing behavior in adults. In order to clarify how psychological stress may influence oral functional patterns and provide new insights for orthodontic assessment and intervention.

A total of 894 adult patients diagnosed with malocclusion from the Department of Orthodontics, Hospital of Stomatology, Zhejiang University School of Medicine, participated in this cross-sectional study. Malocclusion severity was evaluated through clinical assessment based on the index of orthodontic treatment need (IOTN), including both the Dental Health Component (DHC) and the Aesthetic Component (AC). Uncertainty stress was assessed via standardized questionnaire. Mouth-breathing behavior was identified using a structured self-report screening survey, with validity examined against clinical electronic medical records from orthodontic examinations conducted within one month of questionnaire administration. Multiple logistic regression models and structural equation modeling were used to explore the relationships between malocclusion severity, uncertainty stress, and mouth-breathing behavior.

After controlling for confounding factors, uncertainty stress remained significantly associated with mouth-breathing behavior (OR = 1.263, 95% CI: 1.069 to 1.492, p < 0.01), as did the IOTN-AC scoring (OR = 1.087, 95% CI: 1.006 to 1.174, p < 0.05), whereas the IOTN-DHC scoring showed no significant association (p > 0.05). Structural equation modeling showed that uncertainty stress correlated with mouth-breathing behavior (β = 0.19, 95% CI: 0.14 to 0.24, p < 0.001). IOTN-AC had a significant direct effect on mouth-breathing behavior (β = 0.13, 95% CI: 0.08 to 0.18, p < 0.001), as well as a significant indirect effect via uncertainty stress (β = 0.05, 95% CI: 0.02 to 0.08, p < 0.001).

Uncertainty stress and mouth-breathing behavior are closely associated among adults. When both IOTN-DHC and IOTN-AC were considered, only IOTN-AC remained significant, suggesting that aesthetic severity may be an associated factor influencing mouth-breathing behavior in adults.

These findings highlight the importance of integrating psychological stress evaluation into routine orthodontic care, with the aim of improving both functional outcomes and quality of life in adult patients.

Not applicable.