Effect of surface treatments on the flexural properties of repaired conventional and alternative denture base materials.

OBJECTIVES: This study evaluated the effect of different surface treatments on the flexural properties of five base materials, one conventional and four alternative materials, repaired with auto-polymerized acrylic resin.

METHODS: Forty bar-shaped specimens of heat-polymerized polymethyl methacrylate (HCC), polymer blend between polymethyl methacrylate and polylactic acid (PBI), photopolymer resin (APB), polylactic acid (PLF) and polyethylene terephthalate glycol filament (PTF) were fabricated and randomly divided into four groups (n=10) as intact specimens (C) and three repaired specimens; no surface treatment (N), 180 seconds MMA application (M) and single application of DCM (D). The flexural properties were tested with a universal testing machine. Data were analyzed using two-way ANOVA with a heteroscedasticity-consistent (HC3) sensitivity analysis. Simple main effects of surface treatment within each material were tested using Welch's ANOVA and the Games-Howell post hoc test (p-values multiplied by 5 for the five materials, α = 0.05). Three square-shaped specimens of each material were fabricated and randomly divided into untreated (U), MMA-treated (M), and DCM-treated (D) surface conditions (n=1). The surface morphology was investigated as representative observations with a scanning electron microscope (SEM).

RESULTS: The intact specimens showed significantly higher flexural strength than repaired specimens in all materials. The M treatment significantly improved flexural strength of HCC, PLF and PTF. The D treatment significantly improved flexural strength of PBI, PLF and PTF, whereas neither M nor D treatment significantly improved flexural strength of APB. Both treatments exhibited qualitative differences in surface morphology: M treatment in HCC, PBI, PLF and PTF, and D treatment in all materials. Flexural modulus significantly decreased after repair in HCC, APB, and PLF. For PBI, flexural modulus significantly decreased only with M treatment, while PTF showed no significant differences among groups.

CONCLUSION: Within the limitations of this study, the effectiveness of chemical surface treatment for denture base repair was material-dependent. Both MMA and DCM improved flexural strength in specific materials without significant differences between them, and the clinical suitability of DCM cannot be established from this study.

CLINICAL SIGNIFICANCE: PBI and APB show potential as alternative denture base materials based on their intact flexural properties. When repair is needed, the choice of chemical conditioning agent should balance mechanical performance against occupational safety. DCM showed numerically higher flexural strength than MMA in some materials, but the differences were not statistically significant. Because DCM carries greater handling and toxicological concerns, its suitability for clinical repair cannot be established from this study and requires dedicated safety, toxicological, and regulatory validation. As specimens were evaluated only after short-term water storage, these findings should be confirmed under longer-term conditions before clinical adoption.