The relationship of the glenoid fossa position and functional occlusal plane in skeletal class III malocclusion with anterior open bite

ABSTRACT

The correlation of the glenoid fossa position to the occlusal planes in twenty-three skeletal class III malocclusion cases with anterior open-bite were investigated. The sample was collected from the Orthodontic patients in Orthodontic Department, Tanta University. They were selected with the ANB angle less than zero angles. Another twenty-one subjects with normal occlusion were collected from the secondary school students used as control group. All the subjects enrolled in this investigation have an age above seventeen years old. The geometric center of the glenoid fossa was first identified by using a transparent template containing a series of circles whose diameter increased in one-millimeter increments with demarcated centers. The largest circle that nearly fit and tangent to the superior, anterior, and posterior surfaces of the glenoid fossa, was determined. The distance from sella turcica to this center and the perpendicular heights from this center to the lower and upper occlusal planes were measured. The heights that affect the cant of the occlusal plane were measured which are the upper and lower anterior and posterior dental heights. The relationship of the glenoid fossa position represented by S-GC-F1 and S-GC- F2 angles [F1 and F2 are the intersection of the perpendicular from GC on the lower and upper occlusal plane respectively] to the cant of the upper and lower occlusal planes which represented by the length of GC-F1 and GC-F2 were correlated by coefficient correlation test. The results of this study indicate increases of theses angle in both genders of class III with anterior open-bite than in normal subjects. While, the distance from the geometric center to the lower occlusal plane were decreased and increased to the upper occlusal plane in the malocclusion cases than normal. The results also indicate positive correlation between the glenoid fossa position represented by S-GC-F1 angle and the cant of the lower occlusal plane [represented by GC-F1 height] while, no correlation exist between its position represented by S-GCF2 angle and the cant of upper occlusal plane [represented by GC-F2 heigh]. It also indicates decreases in upper anterior and posterior dental height that may attributed most probably to the character of the skeletal, class III cases represented in maxillary deficiency or underdeveloped maxilla