Debonding forces and failure modes of customized three-dimensional printed nano-ceramic hybrid resin fixed lingual retainers.

Background: Retention preserves the optimal esthetic and functional positions of teeth following the termination of active orthodontic treatment. Conventional stainless-steel multistrand fixed retainers have limitations and drawbacks, mainly related to retainer failure.

Objectives: Nano-ceramic hybrid resin (SprintRay OnX) was employed to fabricate new, customized three-dimensional (3D)-printed lingual retainers, and their debonding forces and failure modes were evaluated.

Materials and methods: Pairs of premolars were embedded in acrylic blocks. Fifty acrylic blocks were divided into five groups, including three different cross-sections of customized 3D-printed wires- round (1 mm), oval (1 × 1.5 mm), and semi-elliptical (1 × 1.5 mm)- and comparative stainless steel multistrand retainers (G and H and Respond). Retainers were bonded to the teeth using Transbond™ LR Light Cure Adhesive. The models were stored in distilled water for 24 hours, simulating the wet intraoral conditions. Debonding forces and failure modes were then evaluated. A vertical debonding force was applied to the interdental area of the bonded retainer. Post-retainer debonding failure mode was examined under a stereomicroscope (×10 magnification).

Results: Semi-elliptical 3D-printed retainers yielded the highest debonding forces, followed by oval 3D-printed retainers, twisted G and H retainers, round 3D-printed retainers, and Respond retainers. The debonding forces of oval and semi-elliptical 3D-printed retainers did not differ significantly. The 3D-printed retainer groups presented predominantly cohesive failure due to the strong adhesion between the 3D-printed resin and adhesive.

Conclusion: Oval and semi-elliptical 3D-printed retainers exhibited favorable debonding forces.