The effect of surface treatments and aging on the soft liner-base plate bond produced by 3B printing

Aim: This in-vitro thesis study evaluated the effects of different surface treatments and thermal aging on the bond between a three-dimensional (3D) printed denture base and an experimental soft liner material, and compared the results with conventionally fabricated specimens. Materials and Methods: Eighty 3D-printed specimens were divided into four groups: the acid group was treated with 4% hydrofluoric acid (HF), the sandblasting group with Al₂O₃ particles, and the laser group with Er:YAG laser irradiation, while the control group received no treatment. Additionally, 20 conventional specimens were prepared using heat-polymerized acrylic resin and Molloplast-B. One extra specimen from each group was produced for SEM analysis, and half of the specimens underwent 5,000 thermal cycles. All samples were subjected to tensile testing to record maximum stress values, and failure types were examined under a stereomicroscope. Data were analyzed using ANOVA, t-test, and Bonferroni post-hoc test (p<0.05). Results: No significant difference was found among the non-aged groups; however, after thermal aging, the 3D control group exhibited higher bond strength than the sandblasting and laser groups, with similar values to the acid group. No significant difference was observed between conventional and 3D-printed groups, and aging negatively affected only the laser group. Conclusions: Adequate bonding between the 3D-printed denture base and experimental soft liner was achieved even without surface treatment. The 4% HF acid group showed comparable results, while mechanical surface treatments reduced bond strength. The comparable performance of 3D-printed and conventional groups suggests that digital manufacturing techniques may offer a clinically viable alternative. Keywords: 3D printing, soft liner material, surface treatments