Malocclusion and its relationship to speech sound production: Redefining the effect of malocclusal traits on sound production.

INTRODUCTION: The purpose of this study was to identify variables of dental malocclusion with the greatest effect on sound production that can be easily identified during an orthodontic assessment. METHODS: One hundred fifteen patients (8.2-36 years of age) seeking orthodontic evaluation were assessed for speech sound production abnormalities. An orthodontic clinical examination assessed Angle classification, overjet, overbite, crowding, spacing, and crossbites. A standard speech sample was elicited from each subject. RESULTS: The results indicated that 71 (62%) of the subjects made a production error, particularly with the /s/ and /t/ sounds. However, auditory distortions occurred in 12 subjects (20%), and 56 (80%) subjects had visual distortions of the sound. An open bite (>2 mm) was the key malocclusal factor underlying speech sound errors. There was statistical significance between the Orthodontic Treatment Priority Index and the sound errors of /s / and /t/ (mean score of 9.54 vs 6.29 for subjects without sound errors). CONCLUSIONS: Predictive malocclusal traits are associated with speech sound production errors. The more severe or handicapping the malocclusion, the more likely that a speech sound error will occur. Open bites of 2 mm are associated with sound production errors. Visual inaccuracy of the sound occurs with more frequency than auditory inaccuracy and is the most common articulation error noted with occlusal irregularities.