| Summary: | Introduction: Unilateral posterior crossbite with functional shift is a relatively common condition. Spontaneous correction occurs in ~17% of the cases and mixed dentition slow maxillary expansion demonstrated 84% stability in permanent dentition. The purpose of this study was to evaluate palatal symmetry, dimensions and molar angulation changes following slow maxillary expansion during the mixed dentition compared to untreated controls. Methodology: 30 subjects treated with a Haas-type slow maxillary expansion appliance for unilateral posterior crossbite with a functional shift were compared to 30 control subjects matched for dental age, gender and dental classification. Records were taken at T1= before expansion and at T2= after expansion. Palatal width, surface area, volume and molar angulations measured on digitized models. Palatal surface area and volume divided into anterior, middle and posterior parts then split into crossbite and non-crossbite sides by the midpalatal plane to measure symmetry. Student’s t-test assessed the differences between the groups. Results: Mean intercanine width increase from T1-T2 was 4.65mm, while the intermolar width increase was 4.76mm. The mean increase in the surface area from T1-T2 was 127.05 mm2, while for the controls it was 10.35mm2. The mean palatal volume increased by 927.55mm3 for the treated sample while for the controls it increased by 159.89 mm3. At T1, significant differences between the crossbite and noncrossbite sides were only present in the anterior halves of the controls in surface area and volume. At T2, difference was only present in the surface area of the treated sample in the middle halves. The first permanent molar showed an increase in the buccal and distal inclination after treatment while in controls it showed a decrease. The increase in the buccal inclination was greater on the treated crossbite side. Conclusions: Expansion across the canines and first permanent molars was almost similar. Palate was symmetric before expansion and became asymmetric after expansion in the middle halves. The first permanent molars tipped buccally and distally following expansion with significant tipping on the crossbite side buccally. Our method of molar angle measurement does not require radiation and allows measurement of each individual molar’s angulation. === Dentistry, Faculty of === Graduate
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