Propolis-infused heat-polymerized acrylic denture bases: Enhanced mechanical properties in vitro study

Polymethyl methacrylate (PMMA) is widely used as a denture base material despite its limitations, which include low transverse strength, impact resistance, surface hardness, and relatively high-water solubility and sorption. To enhance its mechanical and physical properties, PMMA has been modified by incorporating various metal powder fillers, such as aluminum and copper - despite their tendency to cause discoloration. These modifications aim to improve the overall quality and durability of dental prostheses.

To evaluate the influence of incorporating microform propolis powder (known for its antifungal and antimicrobial properties and its rich composition of functional groups) into acrylic denture base material, and to assess its effect on selected physical and mechanical properties of the material.

A total of 128 specimens were prepared to evaluate various mechanical properties. Four groups were tested: 1 control group containing acrylic resin without propolis, and 3 experimental groups with propolis powder added at concentrations of 1.0%, 2.0% and 3.0% by weight. Each group consisted of 8 specimens for each mechanical test. All specimens were cured using the conventional heat-curing method. The mechanical properties evaluated included transverse strength, impact strength, surface hardness, and surface roughness. The data were statistically analyzed using the IBM SPSS software.

The group with 1.0% propolis addition showed the highest mean values in all tested mechanical properties: transverse strength (90.50 N/mm²), impact strength (10.45 kJ/m²) and surface hardness (84.39). These values were significantly higher than those of the control group, with statistical analysis revealing highly significant differences between groups (p < 0.05) using ANOVA. Regarding surface roughness, the 1.0% propolis group also recorded the lowest mean value (1.03 μm), compared to the control group (2.14 μm), with all experimental groups showing significantly reduced roughness.

The incorporation of 1.0% microform propolis powder into PMMA denture base material significantly improved its mechanical and surface properties. These promising results suggest that further studies are warranted - either to explore additional properties or to test different propolis concentrations, potentially combined with coupling agents such as silane to enhance bonding and performance.