Recycled PMMA particles from milled discs in denture base materials for improved sustainability.

Objectives: Recycling polymethyl methacrylate (PMMA) in dentistry offers a sustainable solution to address the environmental challenges posed by material waste. This study evaluates the feasibility of incorporating recycled (PMMA) particles into heat-cured denture base materials, focusing on the effects of particle size and concentration on flexural strength, surface hardness, and surface roughness.

Material and methods: Recycled PMMA particles, sourced from milling residuals, were classified into fine (< 400 μm) and whole particles and incorporated into virgin PMMA at 10% and 20% weight/weight (w/w) concentrations to form five groups: Control (100% virgin PMMA), Fine 10% (90% virgin PMMA + 10% fine particles), Fine 20% (80% virgin PMMA + 20% fine particles), Whole 10% (90% virgin PMMA + 10% whole particles), and Whole 20% (80% virgin PMMA + 20% whole particles). Flexural strength (n = 10) was evaluated using a three-point bending test, surface hardness (n = 10) was assessed using the Vickers hardness test (VHN), and surface roughness (n = 10) was measured using an optical profilometer. Statistical analysis was performed using two-way ANOVA and Tukey's post hoc test, with p < 0.05 considered statistically significant.

Results: The results showed that fine particle groups (10% and 20%) maintained flexural strength comparable to the control, whereas whole particle groups exhibited significantly lower values (p < 0.05). Surface hardness improved in fine particle groups, with the highest value in the 20% fine particle group, whereas whole particles, particularly at 20%, resulted in the lowest hardness (p < 0.05). Surface roughness remained unaffected across all groups, with values staying within clinically acceptable limits (Ra < 0.2 μm).

Conclusions: These findings suggest that fine recycled PMMA particles can be effectively integrated into denture base materials to maintain or improve specific properties while contributing to sustainability.

Clinical relevance: This study underscores the potential of recycled PMMA as an environmentally friendly alternative, aligning with global sustainability goals in dental material development.