Introduction: Ambient air pollution exposure is significantly associated with increased posterior crossbite tendency.

Purpose: The objectives of this study were to assess whether there was an association between exposure to ambient air pollution and skeletal and dental measurements of vertical and transverse dimension among adolescents in a clinical cohort in Southern California, and to determine what methods may be best suited for use in future research.

Materials and Methods: 179 subjects' addresses were geocoded and ambient air pollution exposure was calculated based on the Environmental Protection Agency's (EPA) air quality and emissions databases. Vertical and transverse measurements made from subjects' initial lateral cephalometric radiographs and study models were recorded for comparison of dental and skeletal morphology. In addition, residential history and other factors were evaluated by questionnaire to account for potential confounding variables.

Statistical Analysis: Pearson's r correlation and multiple linear regression analysis were used to adjust for confounding variables within our model and determine if an association existed between the pollution metrics and dental outcome variables.

Results: At a statistically significant level, a small negative association exists between pollution metrics: O₃, PM _2.5 NAA, PM_2.5 N24HA and Molar Relation. Ethnicity, gender, indoor heating, and thumb-sucking were identified as significant confounding variables for inclusion in our model.

Conclusions: Increased exposure to ambient air pollution results in a decrease in Molar Relation (greater crossbite tendency). More research is needed to determine the strength of this relationship and develop a model for predicting a patient's risk of developing a respiratory-related malocclusion.