Abstract
Statement of problem. The current chemical solubility method in the International Standards Organization (ISO) 6872 (2015) specifies only the total surface area of specimens for testing (similar to 30 cm(2)) but does not describe the morphology or geometry. This could impact the reproducibility of the test outcomes.
Purpose. The purpose of this in vitro study was to investigate the factors influencing the reliability of the ISO 6872:2015 "Dentistry-Ceramic materials" test for chemical solubility.
Material and methods. Chemical solubility analysis of a range of materials and specimen geometries was performed in accordance with ISO 6872:2015. Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP), VITABLOCS Mark II, IPS e.max Press, and IPS e.max ZirPress materials were formed into a range of cubic and spherical geometries to comply with the 30-cm(2) minimum surface area requirement. The surface microstructure of the specimens was analyzed using a scanning electron microscope, inductively coupled plasma optical emission spectrometry (ICP-OES) was used to analyze the solutes, and surface hardness of the specimens was measured by using a Vickers hardness tester before and after testing. An optimized solubility test was devised, which eliminated specimen handling once the specimens had been ground and polished. This modified test was performed on VITABLOCS Mark II and Y-TZP.
Results. The results of the original chemical solubility method of ISO 6872:2015 showed significantly variable findings for each tested material, with a predictable relationship between geometry and chemical solubility. The hardness values decreased significantly after the solubility testing. The optimized method showed significantly improved reproducibility of the chemical solubility measurement compared with the original ISO 6872:2015 test.
Conclusions. The results of the current chemical solubility standard method can be manipulated while still complying with the ISO 6872:2015 standard.