[Effect of dental prosthesis on the voice]

It is well known that alterations to the oral cavity caused by dental prostheses may affect speech articulation, although influences on the voice are not assumed. In addition to the vocal fundamental frequency, vibrations of the vocal chords generate overtones. Through the shape of the larynx and the upper airway, resonances and antiresonances are formed, and in this way overtones are amplified to a variable extent. Nozzle changes caused by a dental prosthesis in the oral cavity may possibly influence overtones but influences on the vocal fundamental frequency seem unlikely. The influence of dental prostheses on the voice is demonstrated in a patient who owned two different dental prostheses. The fundamental frequency rose by up to five semitones during speech and his vocal range increased by up to four semitones when a thin denture was used instead of a normal denture. When the position of the mandible was checked by intraoral needle point placement, a more rostral position of the mandible was recorded with the thin denture than with the normal denture. Sagittal magnetic resonance tomography imaging also showed that the larynx was in a more cranial position. This change was presumed to be due to an upward movement of the larynx induced by the tongue, which itself was found to be in a more cranial position with the thin denture. In this situation, increased tension of the laryngeal muscles were believed to induce a rise in fundamental frequency, shifting the voice range toward higher frequencies. These findings show that dental prostheses can cause vocal changes in individual cases. The etiology of this occurrence is still not clear. Its consequences, however, should be known to the dentist, ENT surgeon and phoniatrist if patients notice changes in their voice after having altered or replaced their dentures.