Changes in the oral cavity resulting from the loss of teeth and the ensuing reconstruction of a set of teeth by dentures (partial or complete) may cause changes in the speech and voice of the patient. The aim of the present investigation was to study the changes in speech and voice in patients suffering from teeth loss and the degree of speech improvement using dentures. Voice and speech parameters of a set of tested syllables were analysed in 10 patients at the 2nd Clinic of Stomatology. The analysis was carried out by means of an FFT, SoundForge 5.0 programme. Differently expressed acoustic changes in both consonants and vowels were ascertained in a percentage of the patients under examination. These concerned especially the sibilant ("s", "(see text)"), labiodental ("f", "v") and vibrating ("r", "(see text)") consonants. Changes in the FFT spectrum and air leakage in constrictive consonants were also found. In some patients the vowels, especially the closed ones ("i", "u"), may change their fundamental frequency and show noise admixture manifested as a blurred delimitation of the formants. A denture should, inter alia, render it possible for the patient to produce the same articulation to which he/she had been accustomed before the loss of teeth. For the construction of dentures the most important factors from a phonetic point of view appear to be the following: overbite, overjet, the height of the plate, the thickness of the palatal material, the incisor position, and the modelling of the ruga palatina on the hard palate. In case of wrong denture construction the acoustic changes may continue, resulting in the patient's stress load dependent upon sex, age, psychic condition and seriousness of the problem.

The blood serum copper level and the phonation start were investigated in sixteen male subjects with developmental stuttering (mean age = 25.8 years). A statistically significant decrease in blood serum copper level was revealed in the stutterers under study. The differences between their mode and mean values and that of the control group were 4.6 µmol/l and 3.1 µmol/l, respectively. The negative linear regression between the copper level in serum and the vibratio brevis phenomenon was registered in the stutterers under study. A decreased copper level can be involved in the biochemical abnormalities of male developmental stutterers and it can be included among the factors participating in pathophysiology of an uncertain phonation start.

The study offers measurements of the vocal breaks occurring from the modal to the falsetto register in an untrained barytone. The breaks were achieved by increasing the expired airflow. An analogy with a labial pipe served as a help. The voice phenomena were divided into three regions. In the region of low modal frequencies (A–e) a simultaneous sounding of both the modal and falsetto registers was investigated. This was registered perceptually as vocal roughness. Under special conditions a subharmonic tone was produced. In the medium frequency region (e–g¹) the vocal breaks occurred. The break intervals occupied the mean value of about a quint on the modal tone e. With increasing modal frequency, the break intervals decreased. In the high-tone region (g¹–e²) only the falsetto register could be produced.

We studied the effect occurring in close proximity before the phonation start and give an account of the microdramas taking place upon the glottis immediately before the phonation start in a group of individuals suffering from balbuties (60 children and adolescents from 9 to 14 years of age) and an equally large control group suffering from no such speech defect. In the group of children and adolescents with balbuties only less than 4% of the cases showed undisturbed regular phonation starts, whereas in the control group it was almost as much as 90%.

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