ABSTRACT Scientific Approach: Patients with severe dentofacial disharmonies (DFD; jaw disharmonies) seek orthognathic surgery and orthodontic care to address issues with mastication, esthetics and speech. Preliminary data from thousands of DFD patients generated by our colleagues at UNC-CH indicate speech concerns surpass impaired chewing function as a motivator for surgery. Due to limited studies, we, as providers, are unable to give evidence- based recommendations as to whether our orthodontic and surgical interventions will address speech disorders associated with DFD. Despite limited data, patients undergo invasive jaw surgery in hopes of speech improvement. To address this gap in knowledge, we have gathered surgical records and pre-operative audio recordings of patients with DFD to quantitatively characterize their speech. In this proposal, we present preliminary data identifying anatomical thresholds for significant articulation errors. Based on these data, we hypothesize that speech distortions correlate with severity of anterior-posterior and vertical jaw disharmonies, and that corrective surgery yields long-term improvement in speech. We propose the following aims to address this hypothesis and explore the relationship between correction of jaw disharmonies and speech. Aim 1: To examine the relationship between underbite (Class III) and open bite jaw disharmonies, and speech distortion. Aim 2: To assess short- and long-term effects of corrective orthognathic surgery on speech distortion in patients with underbite and open bite. Training approach: Dr. Jacox is a dual-trained clinician-scientist, who completed dental school in parallel with graduate school at Harvard School of Dental Medicine (HSDM- DMD) and Graduate School of Arts and Sciences (GSAS- PhD). In addition, she is a certified diplomate of the American Board of Orthodontics. Her research program and focus of this application was inspired by a patient seeking treatment `to help her talk normally', whereby an evidence-based treatment option was not clear. The mentoring plan for this K08 award is designed to ensure Dr. Jacox will be a well-rounded and successful independent clinician-scientist following completion of the activities in this proposal. Dr. Jacox has assembled a strong mentoring team to guide her professional development and the establishment of her independent research program. Two co-mentors and four consultants from diverse yet appropriate scientific and professional backgrounds will assist in the completion of the training and scientific activities. Scientific interactions as well as didactic training in speech science and technologies of speech science will add to Dr. Jacox's strong foundation in clinical orthodontics and the biology of dentofacial disharmonies. These growth opportunities will allow for successful completion of the proposed experiments, while the professional development activities will complement the training activities and provide Dr. Jacox wit...