Post-cure heat treatments influence on mechanical and optical properties of resin composites

Abstract

This study evaluated the effect of post-cure heat treatment (PCHT) on the Knoop microhardness (KHN), degree of conversion (DC), color changes, and contrast ratio (CR) of four resin composites (RCs): Z100 (3M ESPE), Z350 XT (3M ESPE), Estelite Omega (Tokuyama) and Empress Direct (Ivoclar Vivadent). Specimens (12 × 1 mm) were prepared for each material (n = 10 / group). After curing, samples were subjected to PCHT for 10 min at 100°C or 170°C. Control group was maintained at room temperature (24°C) for the same time. The DC was analyzed by FT-NIR immediately and 24 h after the PCHT (n = 3 / group). KHN was analyzed 24 h after PCHT (n = 10 / group). According to CIEDE2000 (∆E00), color measurements were obtained immediately after curing, five minutes after PCHT, and after seven days of storage in water, coffee, and red wine. Data were analyzed by One and Two-Way ANOVA (p < 0.05). Z100, Z350, and Estelite Omega showed increases in KHN with increased temperature (p < 0.05). PCHT at 100°C and 170°C led to a higher DC of all RCs (p < 0.05). Initially, the PCHT lead to increased ∆E00 values (p < 0.05), which was decreased after immersion in coffee and wine (p < 0.05). Considering the effect of PCHT and staining solutions, lower color changes were observed in the thermally treated specimens (p < 0.05). Taken collectively, the results suggest the PCHT as an economical and practical alternative to enhance direct RC's properties in direct-indirect and indirect restorations.

Influência do tratamento térmico a seco pós-cura nas propriedades mecânicas e ópticas de resinas acrílicas ativadas quimicamente e resinas bisacrílicas

“…Os corpos de prova (cps) foram confeccionados nas dimensões de 12 mm de diâmetro por 1 mm de altura em uma matriz de poliacetal (Baldo et al, 2021). As Os cps de resina bisacrílica foram fabricados de maneira semelhante, exceto que uma pequena quantidade inicial do conteúdo misturado foi descartada antes da aplicação direta da resina bisacrílica dentro de cada matriz de poliacetal com auxílio de pontas misturadoras, em um único incremento, mantendo a extremidade aplicadora sempre imersa no material e com a injeção lenta (5 s) e contínua da resina para minimizar a incorporação de bolhas de ar.…”