To examine the effects of stress, bruxism, malocclusion, and oral habits on the incidence of temporomandibular disorders (TMDs) using a classification tree method (CTM). We obtained data from a total of 1.338 patients: 669 who had TMDs and 669 who but haven't TMDs. We recorded interview data on stress and oral habits, and during oral examination, noted malocclusions, bruxism, and any sign of poor oral habits. All data were subjected to CTM analyses. The TMD rate was highest in stressed patients

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... (96.8%), and significantly lower in stress-free patients (25.3%) (P < 0.001). TMD was evident in all patients exhibiting both stress and bruxism (100.0%). In stressed patients lacking bruxism, the effects of malocclusion on TMD were significant (P < 0.001). CTM analyses showed that the most significant factor affecting TMD was stress, followed by bruxism and malocclusion. This is the first report to use CTM to define factors affecting TMD.