Changes of some functional speech disorders after surgical correction of skeletal anterior open bite

Skeletal anterior open bite (AOB) or apertognathism is characterized by the absence of contact of the anterior teeth and affects articulation parameters, chewing, biting and voice quality. The treatment of AOB consists of orthognatic surgical procedures. The aim of this study was to evaluate the effects of treatment on voice quality, articulation and nasality in speech with respect to skeletal changes. The study was prospective; 15 patients with AOB were evaluated before and after surgery. Lateral cephalometric x-ray parameters (facial angle, interincisal distance, Wits appraisal) were measured to determine skeletal changes. Before surgery, nine patients still had articulation disorders despite speech therapy during childhood. The voice quality parameters were determined by acoustic analysis of the vowel sound /a/ (fundamental frequency-F0, jitter, shimmer). Spectral analysis of vowels /a/, /e/, /i/, /o/, /u/ was carried out by determining the mean frequency of the first (F1) and second (F2) formants. Nasality in speech was expressed as the ratio between the nasal and the oral sound energies during speech samples. After surgery, normalizations of facial skeletal parameters were observed in all patients, but no statistically significant changes in articulation and voice quality parameters occurred despite subjective observations of easier articulation. Any deterioration in velopharyngeal insufficiency was absent in all of the patients. In conclusion, the surgical treatment of skeletal AOB does not lead to deterioration in voice, resonance and articulation qualities. Despite surgical correction of the unfavourable skeletal situation of the speech apparatus, the pre-existing articulation disorder cannot improve without professional intervention.