Anterior open bite and oral port constriction.

Intraoral air pressure and rate of oral airflow were measured simultaneously during fricative sound production in ten subjects with anterior open bite and ten subjects with normal occlusion and speech. From these measurements the area of oral port constriction was calculated and the values compared within and between the two groups. Findings revealed that: (1) The area of oral port constriction was very consistent and reproducible in subjects with normal speech production and normal occlusion. (2) The area of oral port constriction was significantly larger in open-bite subjects compared with control subjects for all sounds. (3) Severe anterior open-bite subjects with a vertical defect over five millimeters were found to produce significantly larger oral port openings than those with only moderate open bite (3-5 mm) for most sounds. (4) A direct correlation between the degree of open bite and the area of oral port constriction was found. As the amount of open bite increased, the area of the oral port increased, especially in the severe open-bite group (5 mm and over).