An Investigation into Aging and Elastic Modulus
Dental composites have gained popularity over amalgam alloys due to their biocompatibility, non-toxicity, and aesthetic appearance. However, the lifetime of dental composites is limited, and restoration failures can occur due to various factors such as occlusal loading and composite shrinkage. To overcome these challenges, it is important to optimize the dental restoration method, cavity shape, and layered restorations. In this article, we will discuss an investigation into the aging behavior and mechanical properties of three distinct dental filling composites by measuring their elastic modulus as a function of time following polymerization.
Experimental Procedure
The investigation involved conducting nanoindentation experiments using a Hysitron TriboIndenter nanomechanical test instrument on dental composites. Cylindrical holes were drilled into an epoxy resin and subsequently filled with the composite. The filled holes were cross-sectioned and polished, after which nanoindentation measurements were conducted over the cross-section at increasing distances from the irradiated surface. A diamond Berkovich probe was used to conduct load-controlled quasi-static nanoindentation tests on the samples.
To understand the impact of aging following polymerization on elastic modulus, nanoindentation tests were performed at four different intervals: 1 hour, 1 day, 1 week, and 1 month following UV light exposure. The specimens were stored in the dark and immersed in a physiological solution at 37°C to replicate real-world conditions.
Results
The results of both the depth profile and aging studies for all three samples of dental composites indicated a significant increase in modulus at the end of the first week. Sample 1 increased from 11.9±0.2 gigapascals to 14.2±0.9 gigapascals, Sample 2 increased from 13.1±0.8 gigapascals to 17.6±0.8 gigapascals, and Sample 3 increased from 5.8±0.2 gigapascals to 7.8±0.3 gigapascals.
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