Effect of polyhedral silsesquioxane (POSS) on the flexural strength and color of interim materials

Polyhedral silsesquioxane (POSS) nanofillers can reinforce interim materials. However, the interaction between the POSS and the brand and its effect on color are unknown.

The purpose of this study was to determine the effect on the flexural strength, color, and color stability of 4 commercially available interim materials modified with 1 wt% POSS.

Four commercial interim resin materials were used in this study: Jet, Trim, Temphase, and Protemp. The flexural strength of the interim materials was measured with and without 1 wt% POSS with an Instron universal testing machine. The color of the interim material and the material with 1 wt% POSS were evaluated, followed by the evaluation of the color change after coffee staining. The data were analyzed with a 2-way analysis of variance (ANOVA) followed by the Tukey standardized range test (HSD) to determine statistical significance (α=.05).

POSS enhanced the flexural strength of Protemp and Trim but had no effect on Temphase and Jet. POSS had a significant affect on the color (L*, a*, b*), but only 2 pairwise differences (in L* Trim versus Trim POSS and in a* Temphase versus Temphase POSS) were detected. The effect of POSS on color change after coffee staining was minimal. POSS only had a significant effect on ΔL, and only 1 pairwise difference was detected (Temphase versus Temphase POSS). The collapsed means revealed significant differences in color change among brands after coffee staining.

The reinforcement effect of POSS on flexural strength depended on the brand, suggesting that the chemistry of the resin affects the ability of POSS to modify mechanical properties. POSS affected the initial color of the interim materials but had little effect on the color change after coffee staining.