Analysis of midpalatal miniscrew-assisted maxillary molar distalization patterns with simultaneous use of fixed appliances: A preliminary study

Abstract

Skeletal anchorage-assisted upper molar distalization has become one of the standard treatment modalities for the correction of Class II malocclusion. The purpose of this study was to analyze maxillary molar movement patterns according to appliance design, with the simultaneous use of buccal fixed orthodontic appliances. The authors devised two distinct types of midpalatal miniscrew-assisted maxillary molar distalizers, a lingual arch type and a pendulum type. Fourteen patients treated with one of the two types of distalizers were enrolled in the study, and the patterns of tooth movement associated with each type were compared. Pre- and post-treatment lateral cephalograms were analyzed. The lingual arch type was associated with relatively bodily upper molar distalization, while the pendulum type was associated with distal tipping with intrusion of the upper molar. Clinicians should be aware of the expected tooth movement associated with each appliance design. Further well designed studies with larger sample sizes are required.

Keywords: Class II; Distalizing; Orthodontic mini-implant.

Figure 1. Midpalatal miniscrew assisted maxillary molar distalizer. Right, lingual archtype appliance; Left, pendulum type appliance

Figure 2. Cephalometric measurements. A, The X-Y coordinate was constructed using a horizontal rotating sella-nasion line in a downward direction at 6° (X-axis) and a vertical line perpendicular to the horizontal line passing through the sella point (Y-axis). Using the X-Y coordinate, a 0–0 point was set at point A, and a new X'-Y' coordinate was constructed. B, 1: Y' line to maxillary first molar mesial cusp tip distance (mm). 2: X' line to maxillary first molar mesial cusp tip distance (mm). 3: X' line to maxillary first molar distal cusp tip distance (mm). 4: Angle (°) between X' line and a line starting from the mesial point of the maxillary first molar crown tangent to the root.