Effect of Specimen Storage Solution on Properties of Polymer-Based Materials

Objectives: To compare calcium release, flexural strength, flexural modulus, and shear bond strength of commercial products across four specimen storage solutions.
Methods: Flexural strength and flexural modulus were tested with BISCO Duo-Link Universal (DLU) self-cured into 2 mm x 2 mm x 20 mm beams following ISO 4049, broken after 24 hours in solution. Shear bond strength to sandblasted stainless steel was tested with DLU and BISCO All-Bond Universal (ABU) following ABU’s self-etching technique, broken after 24 hours in solution. Cumulative calcium release was tested with BISCO TheraCal LC (TCLC) light-cured into disks of 20 mm diameter and 1 mm thickness, with release tested after 1, 2, 3, 7, 14, and 21 days in solution. Each test method was conducted with specimens that had been immersed at 37 °C in one of four storage solutions – deionized water (DI), simulated body fluid formulated following ISO 23317 (SBF), ThermoFisher phosphate-buffered saline (PBS), and Pickering Laboratories 1700-0305 artificial saliva (AS).
Results: For each test, differences between the four storage solutions were statistically analyzed (ANOVA, Tukey, p<0.05). Flexural strength, flexural modulus, and shear-bond strength to stainless steel showed no statistically significant differences between any storage solution groups. For calcium release, all four storage solution groups were statistically significantly different with progressively higher results for AS, PBS, DI, and SBF.
Conclusions: No differences were detected between the four storage solutions for flexural strength, flexural modulus, or shear-bond strength to stainless steel. However, there were significant differences in calcium release between all four storage solutions.