Bond Strength Between Different Soft-Liners to 3D-Printed Denture Base Resins

Objectives: This study aimed to evaluate how various soft-liners adhere to 3D-printed (additively manufactured) denture base resins and to investigate the influence of printing orientation on bond strength.
Methods: The tensile bond strength of two soft-liners; acrylic-based (GC Soft-Liner) and silicone-based (VOCO Ufigel SC) bonded to two 3D-printed denture base resins (Asiga DentaBASE and NextDent Denture 3D+) was tested by using a universal testing machine (Instron). A total of 288 specimens were evaluated, half of which were thermocycled to simulate 1 year in vivo. Debonded surfaces were examined using scanning electron microscopy (SEM), and collected data was statistically analysed using PRISM Ver 9.
Results: The mean tensile bond strength between the Ufigel soft-liners and the 3D-printed denture resins was significantly higher than that of the GC Soft-liners (p<0.0001). When DentaBASE was relined, the mean tensile strength of the 0° and 45° printed specimens was significantly higher (P=0.03) than that of the 90° orientation. For Denture 3D+ bonded to GC Soft-liner, the mean tensile strength of 45° and 90° orientations was significantly higher than 0° (P<0.0001). No statistically significant differences were found between the control and thermocycled groups. SEM images showed more regular porosities in silicone-based soft-liners than in the acrylic-based material, influencing the difference in adhesion.
Conclusions: The silicone-based soft-liner demonstrated a significantly higher tensile bond strength to the 3D-printed denture base resins than the acrylic-based soft-liner. Printing the denture bases at 45° provided the best tensile bond strength for the acrylic-based soft liners. Thermocycling did not affect the tensile bond strength of either soft-liners or 3D-printed denture base resins.