Retention of orthodontic aligners with different gingival margin designs on three-dimensionally printed models representing varying degrees of marginal tissue recession

Objective: To evaluate the influence of three gingival margin aligner designs positioned on models with varying severities of marginal tissue recession. Methods: Nine models were obtained for each marginal tissue ressection class (Classes I, II, III, and IV). Control models had no anatomical alterations. For each model, three aligners of each gingival margin designs were fabricated (scalloped, scalloped extended, and straight). The aligners were placed on the models, and a hook was positioned in the buccal region at the level of the mandibular first molars. Pull-off tests were performed using a universal testing machine at a crosshead speed of 10 mm/min, and the maximum dislodgement force (N) was recorded. Each aligner was removed 10 times, and the average value was obtained. Results: < 0.05). The Class III model (54.4 N) exhibited the second highest retention value, which was significantly different from the other models. There was no significant difference in retention among Class I (25.6 N), Class II (33.2 N), and control (26.8 N). Conclusions: Aligner retention increased with increasing severity of marginal tissue recession. Aligners with scalloped margins provided less retention than those with scalloped-extended and straight margins.