Relapse of curve of Spee leveling with continuous archwire appliance in different vertical skeletal pattern: a retrospective study

To determine the relapse of the leveling of curve of Spee with edgewise preadjusted appliance in different skeletal vertical pattern. The parent sample of 309 subjects, drawn from the database of the Department of Orthodontics of the University of Rome Tor Vergata, was reduced to the final sample of 60 subjects (27 M and 33 F; mean age 19.2) by the application of the exclusion criteria. All subject showed a curve of SPEE ≥ 2 mm, a skeletal Class I or Class II patterns and they underwent preadjusted edgewise therapy. The subjects were grouped according to their facial types based on their pretreatment cephalometric values for y-axis, FMA, and SN^GoGn angle. The arch leveling was measured by the changes in the measurements of the distances of L1, L4, L6 and L7 to MP (Go-Gn). The deepest point of COS was measured on the digital dental casts. Anova test was used to determine the differences between the groups at T1-T2_T3. No statistically significant differences were shown between the groups for the skeletal features. IMPA was significantly increased at T2 in low-angle group. L1-MP showed statistically significant differences at T2 between low and high-angle group. Low-angle group showed statistically significant differences at T3 in COS and OVB value respect to high-angle groups. The levelling of COS was stable in high-angle group in the long-term, on the contrary increased values of COS and OVB was showed post-treatment by low-angle groups due to relapse of L1-MP and IMPA parameters.