Associations Between Halitosis and Craniofacial Morphology, Salivary Biochemical Parameters, and Mouth Breathing in Adult Patients with Malocclusion: A Cross-Sectional Study

<b>Background/Objectives:</b> Halitosis is a common oral condition primarily caused by volatile sulfur compounds (VSCs) produced in the oral cavity. Although previous studies have suggested that craniofacial morphology, salivary biochemical characteristics, and functional breathing patterns may relate to malodor development, their combined influence in adults with malocclusion has not been fully clarified. This study aimed to investigate the relationships among craniofacial morphology, salivary biochemical parameters, and mouth breathing in adult patients with malocclusion. <b>Methods:</b> This retrospective cross-sectional study included 234 adults with malocclusion (75 males and 159 females; mean age 29.0 ± 9.5 years). Halitosis was quantified using gas chromatography, and participants were classified into halitosis-positive (total VSC ≥ 150 ppb, <i>n</i> = 79) and halitosis-negative groups (total VSC < 150 ppb, <i>n</i> = 155). Craniofacial morphology was evaluated using lateral cephalometric analysis, salivary biochemical factors were assessed using a multi-item saliva testing system and Saxon test, and mouth breathing was assessed based on standardized clinical indicators. Group comparisons, multiple linear regression, and logistic regression analyses were performed. <b>Results:</b> The halitosis-positive group demonstrated a larger ANB angle, increased overjet, smaller interincisal angle, and higher salivary ammonia levels compared with the halitosis-negative group (<i>p</i> < 0.05). Multiple linear regression identified the interincisal angle as the only independent predictor of total VSC concentration (β = -4.57 per degree reduction in interincisal angle, <i>p</i> = 0.019). Logistic regression revealed that mouth breathing significantly increased the likelihood of halitosis (OR = 4.68, 95% CI: 2.62-8.38). <b>Conclusions:</b> Craniofacial morphology, salivary biochemical environment, and breathing mode collectively influence halitosis in adults with malocclusion. Incorporating assessment of incisor inclination, salivary ammonia levels, and mouth breathing into orthodontic evaluation may support early identification and preventive management of patients at risk for oral malodor.