Korean J Orthod.  2012 Apr;42(2):73-79. 10.4041/kjod.2012.42.2.73.

Maxillary expansion with the memory screw: a preliminary investigation

• Halicioglu K
• Kiki A
• Yavuz I

• KMID: 2273258
• DOI: http://doi.org/10.4041/kjod.2012.42.2.73

Abstract

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). The mean expansion period was 7.52 +/- 1.04 days. Dentoskeletal effects 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) and Sella-Nasion/Gonion-Menton angles increased, and Sella-Nasion-B point (SNB) angle decreased in all the subjects during the expansion phase. However, they approximated 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 after 6 months of retention.

Keyword

Expansion; Appliances; Cephalometrics; Retention and stability

MeSH Terms

Aged
Hand
Humans
Maxilla
Memory
Palatal Expansion Technique
Parents
Retention (Psychology)
Sutures

Figure

• 

  Figure 1 Landmarks and angular measurements on lateral cephalometric radiograph. The sella-nasion-A point (SNA) (1) angle relates to the anteroposterior position of the maxillary apical base to a line passing through the anterior cranial base. The sella-nasion-B point (SNB) (2) angle relates to the anteroposterior position of the mandibular apical base to a line passing through the anterior cranial base. The mandibular plane-anterior cranial base plane (sella-nasion/gonion-menton [SN-GoMe]) (3) angle relates to the cant of the mandibular plane to a line passing through the anterior cranial base. The maxillary incisor to anterior cranial base plane (1-SN) (4) angle relates to the axial inclination of the most labial maxillary incisor to a line passing through the anterior cranial base.

• 

  Figure 2 Landmarks and linear measurement on posteroanterior radiograph. Maxillary-maxillary apical base width (Mxr-Mxl) was defined as the horizontal distance between the right and left intersections of the lateral contour of the maxillary alveolar process and the lower contour of the zygomatic process of the maxilla.

• 

  Figure 3 Formation of the angles used for inclination assessment. α1 (right molar tipping angle) and α2 (left molar tipping angle), inner angles between the transversal occlusal line connecting the mesio-palatal cusp tips of the right and left molars and the lines passing through the mesio-buccal and mesio-palatal cusp tips of the molars. α3 (palatal tipping angle), inner angle between the right and left alveolar lines connecting the upper and lower alveolar tipping points on each side.

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  Figure 4 Pretreatment photographs of a patient.

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  Figure 5 Photographs after the completion of maxillary expansion.

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  Figure 6 Occlusal radiograph showing sutural separation.

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  Figure 7 Post-treatment photographs.

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