A study of the influence of arrangement of upper posterior artificial teeth on pronunciation: Japanese sounds articulated on the posterior palate.

To clarify the standard of bucco-lingual tooth arrangement in complete denture construction, the influence of the bucco-lingual position of upper posterior artificial teeth on pronunciation was investigated. Wearing 7 kinds of experimental artificial teeth with the upper posterior ones arranged in 7 different positions, patients pronounced 5 test sounds: "ka", "ki", "kw", "ke" and "ko". Resultant sounds were evaluated in terms of how the bucco-lingual position of posterior artificial teeth influenced pronunciation as determined with by aural pronunciation judgment test and frequency analysis using a 1/3 octave-band real-time analyzer. Pronunciation disorders caused by the arrangement of the upper posterior artificial teeth in complete dentures occur when the lingual surfaces of the upper molars is located more than 1/4 inward of the distance between the right and left denture border from the buccal denture border or less than 1/10 of that distance outward from the buccal denture border. Results of the aural pronunciation judgment test indicated that the influence of the arrangement of the upper posterior artificial teeth on pronunciation depends on the vowel following the consonant of the sound. When the vowel following the consonant is a back vowel, as in "ka", "kw" and "ko" the sound was barely influenced, but when the vowel is a front vowel. as in "ke" and "ki", the sound was markedly influenced. We established the frequency spectrum of the consonant of the normally pronounced 5 test sounds as the standard frequency spectral range and compared distorted and misheard sounds with it.(ABSTRACT TRUNCATED AT 250 WORDS)