[CT analysis of the postoperative cyst of the maxilla].

Preoperative CT images of 69 cases (75 sides) of postoperative cysts of the maxilla, seen from 1982 to 1986, were analyzed as to the bony partitions bordering between the cyst and the sinus walls. Three scanned planes, i. e., middle inferior meatus level, superior inferior meatus level, and middle meatus level (each level in 0.5cm distance) were included in the study, and both medial and posterior sinus walls were investigated. The bony partitions were classified into three groups, i. e., dehiscence, thinned-out (less than 1.0mm in thickness) and normal (more than 1.0mm) groups. The dehiscence (or destruction) was seen in 50% at the anterior two thirds of the medial wall, and in 20% at the middle one third of the posterior wall.