Influence of Mandibular Prognathism (class III) on Speech, and Effects of Postoperative Articulation Training

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We examined the postoperatively persisting articulation failure and the necessity/efficacy of articulation training in patients who had required surgical orthodontic treatment for adverse occlusion. Preoperatively the patients with adverse occlusion combined with open bite had tended to produce more interdental sounds than those with adverse occlusion only, regardless of their overjet values. From our findings that none of the patients with postoperatively persisting open bite improved his or her articulation to normal, and that conspicuous dysarthria became normal in some of the patients whose occlusion was improved by operation, we speculate that open bite influences the production of interdental sounds, although it is not decisively concluded since the patients with adverse occlusion combined with open bite were small in number in the present study. Articulation was improved in overall 40% of the patients by articulation training in the postoperative course. This finding suggests that interdental sounds persist even if surgical treatment has improved occlusion, and that the habituated inderdental sounds can be resolved by articulation training. Considering the fact that interdental sounds are produced by the tongue movements which may reverse the improved occlusion to its previous state, postoperative articulation training is significantly important, if interdental sounds themselves may not make conversation unclear.