CHANGES IN CONDYLAR POSITION AND OCCLUSION ASSOCIATED WITH MAXILLARY EXPANSION FOR CORRECTION OF FUNCTIONAL UNILATERAL POSTERIOR CROSSBITE

The purpose of this study was to confirm that correction of functional posterior crossbite through maxillary expansion is associated with a change in condylar position and occlusal relationships, and to determi ne whether maxillary expansion is associated with autonomous increase in mandibular arch width. Pretreatment and posttreatment study models of 61 patients ages 4.1 to 12.0 years (mean 8.5 years, SD 1.5) were av ailable after maxillary expansion with a Quad Helix or a Haas expander for correction of a functional posterior crossbite. Pretreatment and posttreatment tomograms were available for 22 of the patients. Tomogra phic evaluation revealed that the condyles moved posteriorly and super iorly on the noncrossbite side from before to after treatment (p < 0.0 5). No differences were observed on the crossbite side. Superior joint space was greatest on the noncrossbite side before treatment, whereas , conversely, it was greatest on the crossbite side after treatment (p < 0.05). Relative condylar position was more anterior on the noncross bite side before treatment (p < 0.05), but similar on both sides after treatment. Molar and canine relationships were more Class II on the c rossbite side before treatment (p < 0.01 and < 0.05, respectively) and similar on both sides after treatment. A significant reduction in mid line deviation was seen from before to after treatment (p < 0.001). A small, but significant autonomous increase in mandibular intermolar wi dth (p < 0.001) occurred concomitant with the maxillary expansion.