Evaluation of long-term stability of curve of Spee levelled with continuous archwires in two different retention protocol

Objectives: The objectives of the study were to assess the long-term stability of the curve of Spee leveled with continuous archwire in subjects with two different retention protocols. Materials and Methods: The study sample consisted of 20 patients (mean age 18 ± 2 years) presenting with curve of Spee depth of =/> 3 mm. For each subject, lateral cephalograms and dental casts were available before treatment (T1), at the end of orthodontic therapy (T2), and 1 year after the end of treatment (T3). All subjects were divided into two groups according to their retention protocol – fixed retainer group (Group-1) and Essix retainer group (Group-2). Cephalometric parameters were used to evaluate the dental movements after treatment. Curve of Spee depth was measured on standardized digital images of casts. Results: In multicomparison table, it shows that there was a statistically significant difference (P = 0.032) between Spee-T2 and Spee-T3 and there was no statistical difference (P = 0.159) between L1MP-T2 and L1MP-T3 in fixed retainer group. In Essix retainer group, no changes were observed from L1MP-T2 to L1MP-T3 and there was a non-significant difference found between Spee-T2 and Spee-T3. Conclusion: In Group-1 (fixed retainer), there is some amount of relapse or extrusion of lower incisor. In Group-2 (Essix retainer), there was not any change in the position of the lower incisor, which suggests that occlusal coverage of the Essix retainer does not allow any extrusion and retains the curve of Spee.