Leveling the curve of Spee with continuous archwire appliances in different vertical skeletal patterns: A retrospective study

Introduction: The aim of this study was to determine the effects of the leveling of the curve of Spee in subjects treated with preadjusted appliances in different skeletal vertical patterns. Methods: The study sample consisted of 90 white patients (39 male, 51 female; age, 19 years 4 months +/- 1 year 9 months), with a curve of Spee of 2 mm or greater before treatment. They were categorized into 3 groups: low-angle group (30 subjects; 12 male, 18 female; age, 19 years 1 month +/- 1 year 4 months), normal-angle group (30 subjects; 14 male, 16 female; age, 19 years 6 months +/- 2 years 1 month), and high-angle group (30 subjects; 13 male, 17 female; age, 19 years 7 months +/- 1 year 5 months) by their vertical facial types. Cephalometric parameters were used to evaluate the different dental movements after treatment. The curve of Spee was measured on digital dental casts. Analysis of variance was used to determine any differences between the changes in the groups with time. Results: For the skeletal variables, no significant modifications were found in the 3 groups. For the dentoalveolar variables, the low-angle group showed significant buccal movements and intrusion of the mandibular incisors. The high-angle group had greater extrusion of the posterior teeth associated with uprighting of the first and second molars. Conclusions: In low-angle subjects, leveling of the curve of Spee occurs through buccal movement and intrusion of the mandibular incisors; in high-angle subjects, it occurs through extrusion and uprighting of the posterior teeth.