Transverse effects after surgically assisted rapid maxillary expansion in the midpalatal suture using computed tomography.

Surgically assisted rapid maxillary expansion is the treatment of choice for correcting maxillary transverse deficiency in adults. Traditionally, the appliance for expansion is tooth-borne and tissue-tooth-borne devices (Hyrax and Haas). Although a number clinical and radiographic studies have evaluated the surgically assisted rapid maxillary expansion, only limited information is available to study the transverse movement of the midpalatal suture with computed tomography. Forty adult patients of both sexes, ranging in age from 18 to 38 years, with bilateral transverse maxillary deficiency were operated on. Twenty patients had Hyrax expander, and 20 had Haas expander. Under general anesthesia, subtotal Le Fort I osteotomy was performed including pterygomaxillary dysjunction. The width of the midpalatal suture opening was measured at the anterior edge of the midpalatal suture and at the junction of the midpalatal suture and palatal bones, using computed tomography in axial acquisition, obtained in the preoperative period and immediately after the end of expansion. A digital caliper was used to measure Haas and Hyrax distance on the central jackscrew preoperatively and postoperatively. The proportion between the midpalatal suture expansion and the amount of expansion on the jackscrew was evaluated. The mean of midpalatal suture opening and screw opening for Haas group was 5.19 and 8.78 mm, and for the Hyrax group, 5.85 and 8.51 mm, respectively. Both groups showed parallel-shaped separation of the midpalatal opening with no significant difference in the anterior and posterior portion. Midpalatal/jackscrews opening proportion was greater in the Hyrax group (69,2%) than in the Haas group (60%).

Stability of the transverse dimension of the maxilla after surgically assisted rapid expansion.

The aim of this study was to evaluate the behavior of the transverse dimension of the maxilla after surgically assisted rapid expansion with and without using a transpalatal arch fixed retention. Sixty cast models of the maxilla and 60 posteroanterior radiographs from 30 adult subjects, 16 male subjects and 14 female subjects, were evaluated. The subjects were 18.1 to 53.2 years old (mean age, 27.3 years), had been submitted to surgically assisted rapid maxillary expansion, and were using the expansion appliance for four months. The subjects were randomly assigned into two groups of 15 subjects. One group, called the group with retention, received a transpalatal arch fixed retention and another group, which received no retention, was called the group without retention. The assessments were performed at two time points: at the removal of the expansion appliance (T1) and 6 months after the removal of the expansion appliance (T2). In the cast models, interpremolar distances (A-A1) and intermolar distances (B-B1) were measured and in the posteroanterior radiographs, maxillomandibular discrepancy was used. A reduction in the distances A-A1 (-0.76 mm) and B-B1 (-1.54 mm) was observed among the time points studied in the group without retention and this difference was statistically significant. In the group with retention, the difference between the time points T1 and T2 was not statistically significant. The assessment of the maxillomandibular difference showed an increase between the time points T1 and T2 in the group with retention (1.54 mm) and the group without retention (0.84 mm), which means a reduction in the maxillary width in the posteroanterior radiograph. In the comparison between the groups, the assessment of the cast models and the assessment of the posteroanterior radiograph showed no statistically significant difference in any of the variables studied.