Evaluation of long-term dental and skeletal effects of rapid maxillary expansion using modified haas expander anchored on deciduous teeth

Aim: The purpose of this study was to evaluate the short and long term changes of the dental arches and skeletal structures induced by rapid maxillary expansion (RME) anchored on deciduous teeth. Subjects and Method: The study consists of twenty-four patients treated with a modified Haas expander. The records of the patients were evaluated before the treatment (T0), at the removal of the expander (T1) and one year later after the removal of the expander (T2). Lateral cephalometric and panoramic radiographs were analysed with Dolphin Imaging Software. Dental models were scanned by using Dental Wings7 and analysed with Viewbox4 software programme. A total of 49 parameters including 33 cephalometric, 10 model and 6 panoramic measurements were evaluated. Statistical analysis was conducted using IBM SPSS 17.0 package programme. Results: Sagittal displacement of A and ANS points showed statistically significant increase (p<0,001). However change in the SNA angle was not significant. When T0, T1 and T2 time intervals were compared, there were statistically significant increases in the distance between ANS-HRD and PNS-HRD. In our study, no significant difference was observed in the SNB, SN-GoGn and GoMe-HRD angles. The B and Pog points presented statistically significant forward movements according to the VRP in T2 (p=0,039, p=0,005). Both points moved significantly downward in T1 and T2 when compared T0 (p<0,001, p<0,001). Although no significant change was found in the measurements related to maxillomandibular evaluation, the upper anterior and the lower anterior face hights increased. The analysed measurements presented no significant difference in the upper incisor angulation with respect to the anterior cranial base and palatal plane. There were significant increases in maxillary and mandibular intermolar widths. Slight relapse tendency was observed in intermolar width in T2, but T1 values were still statistically significant higher than pretreatment values. All palatal area measurements showed significant enlargement. Arch depth showed no statistically significant change. Palatal expansion produced measurable increase (p<0,001). The right and left A angles showed increase in T2. However, there was a significant decrease in the B and C angles. Conclusion: At the end of RME using modified Haas expander, there were significant changes in both dental and skeletal structures. The findings revealed forward movement of the maxilla, however the incisor angulation did not change. Transverse dimensions of dental arches and palatal area measurements showed significant increase. There was no direct influence of expansion on the lateral incisor and canine angulations.