Effect of modeling liquids on Vickers microhardness, flexural strength and color stability of resin-based composites

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Abstract In this study, the effects of different modeling liquids (MLs) on the Vickers microhardness, flexural strength and color stability of different resin-based composites (RBCs) were investigated. Two RBCs (Essentia Universal, Enamel Plus Hri) and six MLs were used. A total of 140 disk-shaped samples were prepared for the Vickers microhardness (HV0.2) test. The same number and shape of samples were prepared for the color stability (CS) test and 196 rod-shaped samples were prepared for the three-point flexural strength (FS) test. HV0.2 and FS measurements were taken at 24-h and 12-months, while CS measurements were taken at 24-h, 3-months, 6-months and 12-months. The results showed an overall decrease in microhardness for both RBCs after 12-months, with GC Essentia showing a more significant decrease. Flexural strength showed no significant numerical changes. The most significant color changes occurred within the first 3-months when Enamel Plus Hri was combined with specific MLs, with the period from 0 to 3-months proving to be critical for color degradation. In conclusion, both RBCs exhibited reduced Vickers microhardness and significant color changes, especially during the first 3-months, but flexural strength remained stable. MLs have a significant impact on the physical and esthetic properties of RBC restorations, especially in the initial phase. Clinically, these findings highlight that practitioners should manage patient expectations regarding potential color instability during the initial three-month post-operative period and schedule follow-ups to monitor esthetic outcomes.