Effect of Surface Treatments and Repair Resins on the Flexural Strength of Heat-Polymerized Denture Base Resin: An In Vitro Study

Abstract

OBJECTIVE Our research compared the flexural strength of heat-polymerized denture base resin after applying different surface treatments and using various repair materials. METHODOLOGY A total of 96 rectangular specimens made of heat-polymerized acrylic resin were prepared using a customized metal mold following conventional processing methods. Each specimen measured 65 × 10 × 2.5 mm. The specimens were then sectioned into two halves, creating a 3 × 10 × 2.5 mm repair gap. Three groups were formed (n = 32 each) based on the type of repair material used and subdivided into four subgroups (n = 8 each) according to the surface treatment applied. These subgroups included a control group with no surface treatment, a group treated with 37% phosphoric acid, a group treated with 250 µm alumina particles, and a group treated with an Er: YAG laser. The designated repair material was used to repair the gap following surface treatment. The flexural strength of all specimens was then evaluated using a universal testing machine to evaluate the effects of these treatments and repair resins. The recorded flexural strength values were tabulated and analyzed using statistical methods. RESULTS The repair material (group factor) had a significant impact on flexural strength (p < 0.001), with a sum of squares of 166,506.176, a mean square of 83,253.088, and an F-ratio of 24,560.779, demonstrating that the type of resin used for repair influenced the strength of the repaired specimen. The surface treatment (subgroup factor) also had a significant effect (p < 0.001), with a sum of squares of 4,230.983, a mean square of 1,410.328, and an F-ratio of 416.066, confirming that surface treatments improved the flexural strength of the repaired denture base. The interaction between repair material and surface treatment was also significant (p < 0.001), with a sum of squares of 2,357.973, a mean square of 392.996, and an F-ratio of 115.939, suggesting that selecting the appropriate combination of repair material and surface treatment is essential for achieving optimal mechanical strength. CONCLUSION This study's findings indicate that acrylic resin denture repairs can be effectively performed using heat-polymerized, auto-polymerized, or light-polymerized acrylic resin. The results also demonstrated that applying surface treatments to the repair interface enhances repair strength, thereby improving the durability and performance of the repaired denture base.