Evaluation of Microtensile Bond Strength of a 3D-Printed Hybrid Material Under Various Adhesive Strategies

Printed dental materials have emerged to overcome the limitations associated with the subtractive CAD/CAM technologies. The aim of the present study was to evaluate the optimal adhesive strategy for Permanent Crown Resin, a printed hybrid material.

Eighteen specimens of Permanent Crown Resin were divided into three groups of six blocks each, measuring 30 × 30 × 10 mm. A specific surface pretreatment was performed, involving two groups undergoing hydrofluoric acid etching (60 s) and sandblasting (20 s), whereas the third group remained devoid of any pretreatment. Comprehensive surface characterization was achieved using a scanning electron microscope (SEM) at magnifications of 500× and 1000×. Each of the main groups was further divided into three subgroups, each containing two blocks. The paired blocks within each subgroup were then cemented to each other using different cementation protocols: a dual-cure self-adhesive resin cement RelyX^TM Unicem 2, a dual-cure adhesive ExciTE® F DSC, followed by dual-cure resin cement Variolink® Esthetic DC, and a light-cure universal adhesive Scotchbond^TM Universal in combination with preheated composite Filtek^TM Supreme XTE. Subsequently, the specimens were sectioned, and 20 sound micro-bars were obtained from each specimen (n = 180). Each micro-bar was subjected to microtensile bond strength (μTBS) testing at a crosshead speed of 0.5 mm/min.

SEM analysis revealed a smooth surface in the control group, whereas the HF group showed numerous micropores. The sandblasting group showed the roughest surface. Statistical analysis was performed using two-way ANOVA, and a p-value of ≤ 0.05 was considered statistically significant. Regarding the μTBS test, sandblasting pretreatment combined with RelyX^TM Unicem 2 demonstrated higher bond strength than the other groups (60.23 MPa). The predominant mode of failure across all groups was adhesive.

Within the limitations of this study, sandblasting in conjunction with RelyX^TM Unicem 2 provided the highest bond strength for Permanent Crown Resin.