Effects of orthognathic surgery on speech: a prospective study.

This investigation was undertaken to determine the effects of orthognathic surgery on speech. Forty adult females were studied preoperatively and either 6 or 12 months postoperatively. Three experienced speech and language pathologists performed narrow phonetic transcriptions of tape-recorded words and sentences produced by each of the forty patients. These judges also recorded their ratings of each patient's overall hypernasality, hyponasality, and articulation proficiency. In addition, objective assessments of velopharyngeal port area, nasal-oral acoustic coupling, and nasal resistance were obtained. The results suggest that nasal-oral acoustic coupling and nasal resistance are the only parameters significantly affected by orthognathic surgery.