Influence of the preparation design on the retentive strength of resin-bonded attachments.

Objectives: The study investigated the influence of retention grooves and material thickness of the retainer wing on the retentive strength of resin-bonded attachments (RBAs).

Materials and methods: Sixty-four extracted human molars were used. Each tooth received a preparation limited to the enamel for the retainer wings of the RBAs. The specimens were divided into eight groups, each containing eight specimens. The groups varied based on the number of conical retention grooves (0, 1, 2, or 4) and the thickness of the CoCr retainer wings (0.4 mm and 0.8 mm). Before testing the retentive strength of the RBAs, the specimens underwent 37,500 thermal cycles followed by dynamic loading of 1,200,000 cycles on the RBAs' patrices using a chewing simulator. The debonding test was conducted using a universal testing machine at a crosshead speed of 2 mm/min.

Results: The mean retentive strength ranged from 326 ± 96 N to 440 ± 77 N. Only a small portion of specimens (10.9%) exhibited adhesive failure, while the remainder demonstrated cohesive failure within the tooth structure. Neither the number of retention grooves, the thickness of the retainer wings, nor the size of the bonding surface significantly affected retentive strength.

Conclusions: The findings suggest that reducing the number of retention grooves and the material thickness does not influence the retentive strength of RBAs.

Clinical relevance: The retention of RBAs appears promising, supporting the clinical application of this treatment modality.