Active versus passive adaptation: an acoustic study of vowels produced with and without dentures.

A nterior teeth are used directly to articulate some speech sounds, such as the consonants /f/ and /v/, and indirectly to produce other speech sounds, such as the consonant /s/. Thus, it is not surprising to find that prostheses or devices placed near teeth, or replacing teeth, alter speech production. In general the literature dealing with speech changes following dental treatment focuses on alterations to consonant production.‘-’ Perceptual judgments of consonants produced with and without dentures reveal mild distortions of sounds such as /s/ and /sh/.4*8 More discrete, physical measures of consonant production reveal a decrease in the frequency spectrum of consonants when subjects are not wearing dentures and an increase in the frequency spectrum of consonants produced with dentures.‘-” Several interpretations are posed to account for the observations of mild distortions and frequency increases noted in consonant sounds produced with dentures. Some studies indicate that the frequency increases result from active alterations in the oral cavity because of a loss in tooth proprioception or changes in tongue position.’ On the other hand, many authors postulate that the distortions and frequency changes reflect the influence of passive features such as physical characteristics of dentures.” Close examination of previously reported frequency data suggests that the lowering of consonant frequencies during speech without dentures may be attributable to subtle lengthening