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KMID : 0361920120420020073
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Korean Journal of Orthodontics
2012 Volume.42 No. 2 p.73 ~ p.79
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Maxillary expansion with the memory screw: a preliminary investigation
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Halicio?lu Koray
Kiki Ali
Yavuz ?brahim
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Abstract
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Objective: The purpose of this study was to investigate the effects of a newly developed rapid maxillary expansion screw-the memory screw-over 6 months.
Methods: Five subjects, aged between 11.7 and 13.75 years, were enrolled in this study. All subjects underwent placement of a maxillary expansion appliance containing superelastic nickel-titanium open-coil springs in its screw bed. The parents of the patients and/or the patients themselves were instructed to activate the expansion screw by 2 quarter-turns 3 times a day (morning, midday, and evening; 6 quarter-turns a day). Th e mean expansion period was 7.52 ± 1.04 days. Dentoskeletal eff ects of the procedure, including dentoalveolar inclination, were evaluated. Measurements of all the parameters were repeated after 6 months of retention in order to check for relapse.
Results: Sella-Nasion-A point (SNA) andSella-Nasion/Gonion-Menton angles increased, and Sella-Nasion-B point (SNB) angle decreased in all the subjects during the expansion phase. However, they appro ximated to the initial values at the end of 6 months. On the other hand, the increments in maxillary apical base (Mxr-Mxl) and intermolar widths was quite stable. As expected, some amount of dentoalveolar tipping was observed.
Conclusions: The newly developed memory expansion screw offers advantages of both rapid and slow expansion procedures. It widens the midpalatal suture and expands the maxilla with relatively lighter forces and within a short time. In addition, the resultant increments in the maxillary apical base and intermolar width remained quite stable even aft er 6 months of retention.
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KEYWORD
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Expansion, Appliances, Cephalometrics, Retention and stability
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