Effect of magnesium oxide nanoparticles on the flexural strength, surface roughness, and color of self-cure PMMA provisional crowns

Abstract This in vitro study evaluated the effects of magnesium oxide (MgO) nanoparticles on the flexural strength, surface roughness, and color characteristics of a self-cure polymethyl methacrylate (PMMA) provisional crown material. A commercially available PMMA resin was modified with 0.3, 0.5, or 1.0% w/w MgO nanoparticles, while unmodified resin served as the control. A total of 144 specimens were prepared and allocated equally among the four groups for the three outcome assessments. Surface roughness was measured using a contact profilometer, flexural strength was determined using a three-point bending test according to ISO 4049, and color coordinates were recorded using a spectrophotometer in the CIE L*a*b* system. Data were analyzed using the Kruskal–Wallis test followed by Dunn’s post-hoc test with Holm correction. Surface roughness differed significantly among the groups ( p = 0.008), with the 1.0% MgO group exhibiting significantly lower roughness than the control. Flexural strength also differed significantly ( p < 0.001); the 0.5 and 1.0% MgO groups showed significantly higher values than the 0.3% group, while none differed significantly from the control. L* and b* did not differ significantly among the groups, whereas a* showed a significant shift ( p < 0.001). Control-referenced ΔE*ab values derived from the group mean CIELAB coordinates remained below established perceptibility and acceptability thresholds. Within the limitations of this study, 1.0% MgO reduced surface roughness while maintaining flexural strength and overall color characteristics comparable to the control.