The influence of dental prostheses on voice

It is well known that alterations to the oral cavity caused by dental prost heses may affect speech articulation,although influences on the voice are n ot assumed. In addition to the vocal fundamental frequency, vibrations of t he vocal chords generate overtones. Through the shape of the larynx and the upper airway, resonances and antiresonances are formed, and in this way ov ertones are amplified to a variable extent. Nozzle changes caused by a dent al prosthesis in the oral cavity may possibly influence overtones but influ ences on the vocal fundamental frequency seem unlikely. The influence of de ntal prostheses on the voice is demonstrated in a patient who owned two dif ferent dental prostheses. The fundamental frequency rose by up to five semi tones during speech and his vocal range increased by up to four semitones w hen 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 ros tral position of the mandible was recorded with the thin denture than with the normal denture. Sagittal magnetic resonance tomography imaging also sho wed that the larynx was in a more cranial position. This change was presume d to be due to an upward movement of the larynx induced by the tongue, whic h 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 vo cal changes in individual cases. The etiology of this occurrence is still n ot clear. Its consequences, however,should be known to the dentist, ENT sur geon and phoniatrist if patients notice changes in their voice after having altered or replaced their dentures.