Evaluation of shear bond strength of 3D-printed flexible denture materials and reline materials

This study aimed to compare the shear bond strengths (SBS) of two three-dimensionally (3D) printed flexible denture resins and a conventional injection-molded resin bonded with two hard chairside reline materials.

Three flexible denture materials (two 3D-printed resins, including Bright 3D Flexible Denture [Bright] and Tera Harz Flexible Denture [TFDH], and one conventional resin [Con]) were bonded with Ufi Gel Hard (U) and Tokuyama Rebase II (R). In total, 120 specimens were fabricated, relined, and subjected to SBS testing before and after thermocycling. Failure modes were classified as adhesive or mixed. SBS values were analyzed using two- and one-way analyses of variance, t-tests, and Mann-Whitney U tests (α = 0.05).

Groups bonded with U had significantly higher SBS than those bonded with R across all combinations of the 3D-printed flexible denture resins. TFDH bonded with U exhibited the highest SBS both before (4.78 ± 1.72 MPa) and after thermocycling (4.05 ± 0.96 MPa), whereas 80% of TFDH bonded with R specimens and all Bright bonded with R specimens failed after thermocycling. Con bonded with R exhibited the lowest SBS after thermocycling (0.75 ± 0.39 MPa). Failure mode analysis confirmed the predominance of adhesive failure in the groups bonded with R and mixed failures in the groups bonded with U.

With appropriate selection of reline materials, 3D-printed flexible denture resin showed significantly higher SBS than that of the conventional flexible denture resin. Appropriate material pairing is critical for achieving durable relining in clinical applications.