الفهرس 
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Abstract
Speech is an essential human activity. Phonetics must be considered one of the cardinal factors contributing to the success of complete dentures. It was meaningful to find out whether different posterior teeth position would affect the phonetic mechanism of complete denture wearers.
Twenty completely edentulous male patients were selected. One denture was constructed for each patient with teeth arranged on the crest of the ridge and then the teeth were removed and replaced on the neutral zone according to the neutral zone record. The patients were instructed to pronounce (Eskendereyya – اسكندرية) to record the letter /s/, to pronounce (Hafla – حفلة) to record the letter /f/, to pronounce (ata – أتى) to record the letter /t/ and to pronounce (Mendada – منضده) to record the letter /d/.
The phonetic of the patient was recorded for both teeth positions (on the crest of the ridge and in the neutral zone) and analysed by Computerised Speech Lab into a spectrogram. On the spectrogram, the frequency, duration first peak energy and average energy was recorded for the letters /f/ and /s/ while stop gap, voice onset time, first peak energy and average energy were recorded for the letters /t/ and /d/.
The result of the study showed the following:
• There was no statistically significant difference between the two measurements of the mean and standard deviation values of fricative (f) frequency at the crest of the ridge.
• There was no statistically significant difference between the two measurements mean and standard deviation values of voice onset time (t) at the crest of the ridge.
• The measurement of the mean and standard deviation values of fricative (s) frequency at the crest of the ridge and at the neutral zone showed a statistically significant higher mean value than at the crest of the ridge.
• The measurement of the mean and standard deviation values of voice onset time (d) at the crest of the ridge showed a statistically significant higher mean value than at the neutral zone.