Mandibular Plane and Palatal Plane Angle Changes with Immediate Rapid Palatal Expansion

Objective: The primary purpose of this study was to determine any mandibular plane angle(MPA)and palatal plane angle(PPA)changes directly associated with active banded rapid maxillary expansion(RME)and not affected by subsequent orthodontic traetment. Methods:Cephalograms for 44 patients(12yrs+/-5)who had undergone 9-11mm RME were assessed.One pre-tx and one(1mo)post RME stablization ceph were traced and analyzed for each.The following measures were made, tabulated and MPA and PPA changes(pre-to post)were stastically analyzed once the inter-rater reliability was established:SN-MP(Sella Nasion-Mand Plane)and SN-PP(Sella Nasion-Palatal Plane).Other vertical changes studied were:NA-ME(Nasion-Menton),NA-IE(Nasion-Incisal Edge)in the anterior and DCT-SN(Max molar Distal Cusp Tip-Sella Nasion)in the posterior. Results:Inter-rater reliability for all measures was good(CR=0.7-o.9 range).There was a slight clinical increase in MPA of 1.08 degrees(+/-0.34)(P<0.0001).Face height(NA-ME)clinically increased very slightly but was stastically significant at 0.25(+/-0.18)(P<0.0001). No significant changes occurred in PPA, upper anterior face height(NA-IE),or upper posterior fce height(DCT-SN). Conclusion:In conclusion, RME therapy with banded teeth and 9-11mm expansion created a stastically significant increase in MPA and NA-ME facial height but neither increase is great enough to be of clinical importance.