パラタル・バーの発音への影響について

Abstract

Wearing a denture changes the intraoral environment and pronunciation disturbance is likely to occur. As one of cases, lack of consideration at the designing stage of dentures for making a dentures that gives less feeling of something foreign cannot be overlooked. Partial dentures are complex in structure and it is easily presumed that oral sensation could be impaired. An investigation therefore was made the effect of the palatal bar which is a component of a partial denture on pronunciation. Individual normal dentulous adults without abnormalcy in pronunciation function were selected as subjects. For each subjects, anteior, middle, and posterior palatal bars of 0.5 mm, 1.0 mm, and 1.5 mm in thickness each were made and pronunciation peculiarities when each bar was mounted were examined with use of sound spectrograms. The sounds examined were 'ka', 'sa', and 'ta' column sounds. The results were as follows : 1. For 'ka' column sounds, every palatal bar affected sustaining time of the consonant and intraoral mounting of the palatal bar had greater effect on pronunciation of 'ka' column sounds than the running position or thickness. 2. For 'sa' column sounds, with wearing of the anteiror palatal bars, longer and shorter sustaining time of the consonant, as against non-wearing, occured with about the same frequency, and effect of palatal bars varied by individual. Cases affected by middle and posterior palatal bar decreased greatly, and with regard to 'sa' column sounds, middle and posterior palatal bars did not affect sustaining time of the consonant as much as anterior palatal bars did. 3. For 'ta' column sounds, when the palatal bar ran toward the anterior portion of the palate, forming of a narrow became very easily and consequently sustaining time of the consonant was presumed to be shortened. With posterior palatal bars, although a narrow necessary for pronouncing 'ta' column sounds was not directly involved, abnormal contacts between the tongue and the palate made rates of sustaining time of the consonant greater. With regard to 'ta' column sounds, middle palatal bars had the least effect of all on sustaining time of the consonant. 4. Changes in the thickness of palatal bars did not affect sustaining time of the consonant of 'ka', 'sa', and 'ta' column sounds. Running position of the palatal bar and the bar itself rather than thickness greatly affected sustaining time of the consonant. 5. Changes in the intraoral environment of the magnitude of merely mounting a palatal bar had hardly any effect on the formant distribution. 6. Energy ratios of 'ka' and 'ta' column sounds were not much affected by mounting of a palatal bar. Rather than running position or thickness, presence or absence of the palatal bar was the greater factor of influence. 7. In energy ratios for 'sa' column sounds, many subjects were affected by use of anterior palatal bars, but the direction of influence varied with individuals and there were cases of both larger energy ratios and smaller ones. 8. The use of the palatal bar in the oral cavity was presumed to be a great factor for the 'ka' column sounds. 'sa' column sounds were the ones affected most by the palatal bar, and middle and posterior palatal bars where a narrow is not formed did not cause pronunciation impairment. For 'ta' column sounds, middle palatal bars affected least of all.