Investigation of the factors influencing the outcome of prostheses on speech rehabilitation of mandibulectomy patients

Purpose: The aim of this study was to investigate the factors influencing the outcome of prostheses on speech rehabilitation of mandibulectomy patients.Methods: Eleven patients (6 males and 5 females) who underwent mandibulectomy without glossectomy because of a tumor participated in the study. A Speech Intelligibility (SI) test was applied without and with a prosthesis to evaluate their speech ability. The type of resection, whether soft tissue grafting was undertaken or not, the continuity of mandibular bone, and the number of remaining teeth related to the stability of the prosthesis were determined from the medical records. The some of acoustic features, Formant 1 and Formant 2 range, were investigated to evaluate objectively the limitation of tongue movement. Five questionnaires were sent out to evaluate subjectively the difference in sense of discomfort while speaking with and without the prosthesis. These eleven items were entered into stepwise multiple regression models to determine the predictors of the differences in SI score without and with a prosthesis.Results: Three variables, the ease of tongue movements, whether soft tissue grafting was undertaken or not, and whether the mandibular bone was continuous or not, contributed to the recovery of speech ability with prosthodontic treatment.Conclusion: The ease of tongue movement, no soft tissue grafting, and the continuity of mandibular bone contribute to the recovery of speech ability with prosthodontic treatment.