Abstract

1. Patrizia Bonaventura1, FabianaVarjao2, Varun Sharma3 1 Department of Psychological Sciences, 2 School of Dental Medicine, 3 Department of Mechanical Engineering Case Western Reserve University, Cleveland, OH Abstract The present study compared articulatory patterns in production of dental stop [t] with conventional dentures to productions without dentures. The goal was to identify characteristics of effective articulatory strategies emerging in the adaptation period after the application of a new denture, that assure restoration of normal speech function. An articulatory analysis has been performed of patterns of dental stops closure in onset of CVC monosyllabic words, by electromagnetic articulography. Position values of tongue blade movements have been identified in correspondence to acoustic events (burst, vowel onset and F2 transitions offset), and compared between pronunciations by a speaker with denture and a normally dentate one. Results showed that an effective compensatory articulatory strategy adopted by the speaker with denture during adaptation, involved higher than normal coupling of anterior and posterior portions of tongue blade. Goal & Conclusions & Discussion Analyses Vertical position values of T1 and T2 movements in syllable onset for [t], in 5repetitions of the word ‘tot’ by each speaker, were measured at three points corresponding to the acoustic events of burst (B), vowel onset (V) and end of F2 transitions offset (T). Speech Corpus and Recordings Monosyllabic [t V t] words and non-words, containing different vowels, were analyzed, and compared between subjects with and without conventional dentures. Research Questions Goal:to evaluate effectiveness of conventional dentures in terms of accuracy of speech production Research Question: What are the articulatory patterns that emerge with new dentures, that effectively restore speech function? Comparison of tongue blade trajectories within syllables Tongue blade movement patterns were characterized by the amount of covariance between anterior (T1) and posterior (T2) portions of the blade. The difference between the patterns in production with dentures and without dentures, is shown in Figg. 3 and 4, which display movement data from repetitions of 97 sentences containing CVC monosyllabic words with different consonants and vocalic nuclei. Only the words of [tVt] form were analyzed. However, the T1 and T2 movement patterns for [t] in syllable onsets, as produced with dentures, did not show clear velocity maxima and minima within the onset portion of the syllable (Fig. 2 vs 1). Therefore, in order to characterize the movements, vertical position was measured in correspondence with three acoustic events (Ma and Perrier, 2006 ): burst (B), vowel onset (V) and F2 transition offset (T). Covariance between T1 and T2 vertical position values was calculated at B, V and T (Fig. 5). Speech with dentures Previous studies Effects of dentures on speech were usually observed by acoustic analysis (Jindra et al. 2002; Vähätalo et al. 2005; Runte et al. 2001) or perceptual analysis (Sansone et al. 2006), focusing on the speech sounds most frequently mispronounced with dentures (/s, f, v, r, t/ or specific vowels). Fig. 2T1position curves for 5 repetitions of the word ‘tot’ by a normally dentate speaker Fig. 3 T1position curves for 5 repetitions of the word ‘tot’ by a speaker with denture Articulatory analysis The present study analyzed tongue blade gestures for production of the alveolar English [t] consonant, frequently mispronounced due to the presence of the new denture, by a Carstens 2D electromagnetic articulograph. Sensors used were T1, T2, T3, T4, from tongue tip to tongue back. . Fig. 3 Movement data for 97 sentences repetitions by one participant with no denture Fig. 4 Movement data for 97 sentences repetitions by one participant with denture Method Discussion Results showed higher covariance of movements of tongue anterior and posterior blade in the speaker with denture, with respect to the speaker with normal dentition. The [t] production by the speaker with denture did not appear perceptually abnormal; the different pattern of tongue blade movement described in the present study, therefore, probably represents an effective compensatory strategy that emerged within 2 months from application of the denture, and assured an effective speech production. Results Participants 1 patient with conventional denture, and 1 age-matched control with normal dentition, were selected. The patient was totally edentulous, that is, missing all of her natural teeth in the maxillary (upper) and mandibular (lower) arches, and had new conventional dentures constructed for the maxillary arches, and for the mandibles. The dentures had been applied within a period ranging from 3-4 weeks to 2 months; she had no muscular dysfunction previous to the application of the denture, or no complication that might affect speech, other than the denture. An age matching normally dentate individual was selected. Dialectal origin was not controlled. Acknowledgements This project has been realized by the support of the CWRU College of Arts and Sciences, and School of Dental Medicine, and by the kind collaboration of the Cleveland Hearing and Speech Center Fig. 5 Covariance of T1 x T2 vertical position values I’tot’ syllable onset, measured at Burst, Vowel Onset and F2 transitions offset, for patient with denture (red) and normally dentate speaker (blue)