Orthognathic Speech Pathology: Understanding How Dentofacial Disharmonies Effect Speech

Objectives: Patients with dentofacial disharmonies (DFD) seek orthodontic care and orthognathic surgery to address issues with esthetics, mastication and speech. Speech-sound disorders (SSDs) are seen in 80-90% of DFD subjects compared with 5% of the general population, impacting communication and quality of life, but the causal link is unknown.
Methods: To understand how jaw disharmonies influence speech, orthodontic records and audio recordings were collected from surgical candidates pre-operatively (n=103 Class III underbite, 39 open bite, 62 controls), and at 3- and 12- months post-operatively (n= 16 Class III, 10 open bite). A speech pathologist evaluated subjects and recordings were quantitatively analyzed by spectral moment analysis for frequency distortions.
Results: Significant differences between DFD patients before and after surgery were found for consonant sounds, with post-operative values approaching those of non-surgical controls. Significant trends correlating malocclusion severity with articulation distortion were found for phonemes /t/ and /k/ using linear regression (p< 0.05).
Conclusions: These data are the first to demonstrate that degree of sound distortion correlates with severity of malocclusion, suggesting causation. Furthermore, post-operative speech frequencies approach control values, indicating that corrective surgery may be important for treatment of speech distortions in DFD patients. Results are highly relevant for the clinical management of DFD subjects with speech pathologies.