Palatal morphology and oral-nasal function in cleft palate patients.
A scientific essay in Medical Sciences
DOCTORAL THESIS defended in public on 15th of August 1997
The purpose of this investigation was to study the palatal morphology and oral-nasal function among cleft palate patients with different types of clefts. The sample consisted of 95 subjects with various types of clefts, all including cleft palate and 68 noncleft individuals.
The moir‚ technique was modified and applied to evaluate palatal morphology. Its reliability was tested and proved to be good. Craniofacial morphology was evaluated from lateral cephalometric films. For measuring rest breathing and velopharyngeal function during speech production, the pressure-flow technique was utilized.
Compared to noncleft individuals, the cleft palate subjects had a smaller palatal height, depth, and width, a more asymmetrical location of the upper first molars, a more deviant shape of the palate. Multiple regression showed that the different cleft types had a different effect on palatal dimensions and symmetry, especially those cleft types that involved the secondary palate had a decreased palatal height. The cleft type affected both the anteroposterior and transverse position of the highest point of the palatal vault.
During rest breathing cleft palate patients had a larger differential pressure and nasal resistance, and a smaller cross-sectional area and nasal flow rate than noncleft individuals. The individuals in which the cleft was located in the anterior part of the palate had a decreased nasal cross-sectional area and airflow rate but the nasal resistance was not affected. Midfacial morphology, especially vertical facial proportions were related to decrease in nasal cross-sectional area and increase in the nasal resistance while the effect of palatal morphology on rest breathing was small. Those cleft individuals, who had adequate upper airway size, were able to breathe normally.
During speech production nasal airflow rate and velopharyngeal orifice area were increased in cleft palate patients, but oral-nasal differential pressure was not different from the control group. In the cleft types in which the cleft was located in the posterior part of the palate, velar function was affected. Craniofacial and pharyngeal features, like the length of the palate, depth of the nasopharynx and those features reflecting vertical facial discrepancies were associated with velar function. Hypodontia and the configuration of the posterior palate had also some effect on the velar function, but this was minor and improved with age.
Different cleft types seem to have a different kind of effect on palatal morphology and oral-nasal functions and therefore the cleft type should be taken into account in the treatment planning of the cleft palate patients. The existence of a cleft as such without decreased upper airway size does not lead to nasal impairment. The morphology of the palate affects more velar function than rest breathing. The point that the differential pressure did not differ between cleft and noncleft subjects supports the pressure maintenance theory during speech production. Individuals with severe clefts compansate their velopharyngeal insufficiency by increased nasal airflow rate sustaining adequate pressure for speech.