Marginal integrity of restorations produced with a model composite based on polyhedral oligomeric silsesquioxane (POSS)
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Marginal integrity is one of the most crucial aspects involved in the clinical longevity of resin composite restorations. Objective: To analyze the marginal integrity of restorations produced with a model composite based on polyhedral oligomeric silsesquioxane (POSS). Material and Methods: A base composite (B) was produced with an organic matrix with UDMA/TEGDMA and 70 wt.% of barium borosilicate glass particles. To produce the model composite, 25 wt.% of UDMA were replaced by POSS (P25). The composites P90 and TPH3 (TP3) were used as positive and negative controls, respectively. Marginal integrity (% MI) was analyzed in bonded class I cavities. The volumetric polymerization shrinkage (% VS) and the polymerization shrinkage stress (Pss - MPa) were also evaluated. Results: The values for % MI were as follows: P90 (100%) = TP3 (98.3%) = B (96.9%) > P25 (93.2%), (p<0.05). The % VS ranged from 1.4% (P90) to 4.9% (P25), while Pss ranged from 2.3 MPa (P90) to 3.9 MPa (B). For both properties, the composite P25 presented the worst results (4.9% and 3.6 MPa). Linear regression analysis showed a strong positive correlation between % VS and Pss (r=0.97), whereas the correlation between Pss and % MI was found to be moderate (r=0.76). Conclusions: The addition of 25 wt.% of POSS in methacrylate organic matrix did not improve the marginal integrity of class I restorations. Filtek P90 showed lower polymerization shrinkage and shrinkage stress when compared to the experimental and commercial methacrylate composite.