The purpose of the study was to determine the immediate and possible long-term effects of a mandibular osteotomy upon speech and tongue thrust (where present). To explore this, four subjects who exhibited a Class Ill malocclusion or skeletal underbite, in addition to a lisp, were evaluated before and after undergoing a sagittal osteotomy. The evaluation consisted of identical speech and tongue thrust assessments completed within two weeks of and nine weeks after the scheduled surgery. Both evaluations were completed by a panel of three speech-language pathologists. The speech evaluation required the subject to read ten /s/ and ten /z/ phoneme sentences taken from the McDonald Deep Test of Articulation. Each subject was judged as either exhibiting or not exhibiting a lisp on each sentence read. The tongue thrust evaluation utilized a quantitative tongue thrust baseline measurement in which the subject's tongue position was ranked during the swallowing of food, liquid, and saliva.
Bruce, F. A., & Hanson, M. L. (1987). Speech swallowing changes associated with sagittal osteotomy: A report of four subjects, International Journal of Orofacial Myology, 13 (2), 1-6.