Influence of the partial denture on the articulation of dental and postalveolar sounds.

Dental prosthesis is a foreign body in oral cavity and thus necessarily interferes with speech articulation. The purpose of this study was to examine influence of partial denture on speech quality and to show eventual differences in pronunciation of dental sounds c[ts], z [z], s [s] and postalveolar sounds c [t], z [3] and s [integral of]. We have examined differences in pronunciation between subjects with removable partial dentures, the same group without partial dentures and a control group. The study was performed on 30 subjects with removable partial dentures and 30 subjects with complete dental arch. All subjects were recorded while reading six Croatian words containing the examined sounds. Recordings were analyzed with Multispeech Program (Kay Elemetrics Inc.). Acoustic analysis--LPC (linear prediction coding) provided formant peaks (Hz) for each examined sound, its intensity (dB) and formant bandwidths (Hz). Results showed that subjects with partial dentures had 50% less distorted variables and that prostheses did not completely restore articulation of postalveolar sounds. Groups with and without prostheses had lower formant peaks intensities and wider formant bandwidths in comparison to the control group. Partial dentures have not significantly interfered with resonance frequency. At the same time, pronunciation of the examined sounds was significantly improved. However, precision of the articulation movements has deteriorated.