Effect of Nanohydroxyapatite and Silver Nanoparticle Incorporation on the Flexural Strength of Resin Composites

This in vitro study investigated the impact of silver nanoparticles (AgNPs) and nanohydroxyapatite (nanoHAP) on the flexural strength of dental composite resin. Fifty composite samples were prepared in five groups (<i>n</i> = 10): (1) nonspatulated composite resin (negative control); (2) hand-spatulated composite resin (positive control); (3) composite resin and 2 wt% nanoHAP; (4) composite resin and 1 wt% AgNPs; and (5) composite resin, 2 wt% nanoHAP, and 1 wt% AgNPs. Flexural strength was measured using a universal testing machine. Scanning electron microscopy (SEM) was used to evaluate the dispersion of nanoparticles in the composite resin. The data were analyzed using the Kruskal-Wallis and Mann-Whitney tests (<i>p</i> < 0.05 was considered significant). The highest mean flexural strength was observed in the negative control, while the lowest flexural strength was seen in Group 4 (composite resin and AgNPs). The nanoHAP group demonstrated significantly higher flexural strength than the AgNP group (<i>p</i> = 0.043). However, no significant difference was observed between the nanoHAP-only group and the group containing both nanoHAP and AgNPs (<i>p</i> = 0.075). These findings suggest that nanoHAP-loaded composite resin possesses higher flexural strength than AgNP-incorporated composite resin. Additionally, comparisons with the positive control group indicated that the addition of nanoparticles did not necessarily result in significant improvement in flexural strength. These findings can pave the way for future studies on optimizing the composition of advanced dental materials with enhanced longevity and improved mechanical properties.