The impact of mandibular advancement on articulation, resonance and voice characteristics in Flemish speaking adults: a pilot study.

Bilateral saggital split osteotomy (BSSO) of the mandible is a frequently performed mandibular orthognathic procedure, used to resolve mandibular disharmonies. Literature review showed contradictory findings regarding the effect of the orthognathic surgery on speech characteristics. The purpose of the present study was to determine a detailed analysis of the articulation, resonance and voice characteristics after BSSO with mandibular advancement for the treatment of Class II malocclusions using objective and subjective assessment techniques (perceptual evaluations, Dysphonia Severity Index, nasalance scores) in eight subjects. The findings of the present study indicate that before and after BSSO with mandibular advancement three types of articulation disorders may predominate in the Flemish language: the incorrect production of the trill sound /r/ and the /s/ sound and devoicing of the /z/. After orthognathic surgery most patients showed an identical articulation pattern (normal or disturbed pattern) as in the presurgical condition. In this study the BSSO with mandibular advancement had no significant impact on the nasality characteristics and the nasalance values probably due to the competent velopharyngeal valving in the presurgical condition. And, as expected the vocal quality revealed no significant difference. The maxillofacial surgeon and the speech language pathologist must be aware of the persistency of these preoperative articulation errors in the postsurgical condition.