The impact of different surface treatments on repair bond strength of conventionally, subtractive-, and additive-manufactured denture bases

Objective: This study aimed to examine the shear bond strength (SBS) of repair material to conventionally, subtractive-, and additive-manufactured denture bases after different surface treatments.

Materials and methods: Disk-shaped test specimens (N = 300) were prepared from denture base materials produced by one conventional (Procryla), one subtractive (Yamahachi), and one additive (Curo Denture) method. The test specimens were randomly divided into five groups (n = 10) and exposed to a variety of surface treatments-Group A: no surface treatment; Group B: grinding with silicon carbide paper; Group C: sandblasting; Group D: erbium: yttrium-aluminum-garnet laser; and Group E: plasma. Repair was performed with autopolymerizing acrylic resin (Meliodent). Surface roughness analyses were performed with a profilometer. Scanning electron microscopy was used to examine one specimen from each subgroup. SBS was evaluated on a universal testing machine. Failure types were observed under a stereomicroscope.

Results: Surface roughness values were significantly higher in all test materials in Group D than in the other groups (p < 0.001). For conventional resin, the SBS values were higher in Group C than in Groups A, D, and E (p < 0.001). For CAD/CAM material, Groups B and C had significantly greater SBS increases compared with Group E (p < 0.001). For 3D material, Group D showed higher SBS than all groups except Group C (p < 0.001).

Conclusions: For SBS, sandblasting was most effective in the conventional group, whereas laser treatment was the most effective in the additive-manufactured group. For the subtractive group, surface treatments other than plasma exhibited similar SBS.

Clinical significance: In repairing fractured prostheses, any degree of roughening suitable for the material content may provide an SBS benefit.