Assessment of Vertical Changes During Palatal Expansion Using Quad Helix or Bonded Rapid Palatal Expander

Hypothesis: There is no statistically significant mean difference in vertical dimension changes between the quad helix expander and the bonded rapid palatal expander during phase I treatment for growing skeletal class I and class II subjects. Objective: The objective of this study was to determine if there is a significantly different effect on vertical changes during palatal expansion in phase I treatment using a quad helix expander or a bonded rapid palatal expander in growing skeletal class I and class II subjects. Methods: This retrospective study looked at two treatment groups, a quad helix expander group and a bonded rapid palatal expander group, before treatment (T1) and after the completion of phase I treatment (T2) to assess changes in the vertical dimension after palatal expansion treatment. Each treatment group was also compared to an untreated predicted growth model. All subjects were growing patients with either a class I or class II skeletal pattern. Lateral cephalograms taken before treatment and after the completion of expansion and phase I treatment were traced using Dolphin Imaging, and these cephalometric tracings were used to analyze the changes in vertical dimension. Results: When the quad helix and bonded rapid palatal expander groups were compared to each other, no difference was found at T1, but significant differences at T2 were found for the variables convexity, lower facial height, total facial height, facial axis, and FMA. When the two treatment groups at T2 were compared to their respective untreated predicted growth models, a significant difference was found for the variable lower facial height for the quad helix group and for the variable U6-PP for the bonded expander group. Conclusions: The differences found at T2 between the two groups suggested that the quad helix expander had more control over skeletal vertical measurements than the bonded rapid palatal expander, based on this sample. When comparing treatment results to untreated predicted growth values, the quad helix expander appeared to maintain lower facial height better than the bonded rapid palatal expander, and the bonded rapid palatal expander appeared to maintain the maxillary first molar vertical height better than the quad helix expander. Overall, both the quad helix expander and the bonded rapid palatal expander showed minimal vertical changes during palatal expansion treatment.