Benchmarking the Chemical Solubility of Restorative Dental Ceramics

Objectives: The current ISO 6872:2008 specifies a standardized testing method to measure the chemical solubility of dental ceramics. Unfortunately, few published studies of chemical solubility have adhered to the ISO test. Therefore, the aim of this study was to assess the current ISO solubility test for benchmarking the chemical solubility of restorative dental ceramics and to investigate the impact of the flexibility in sample size afforded by the new standard.
Methods: The chemical solubility analysis was performed to the study samples according to the (EN ISO 6872:2008). Two types of dental ceramics were involved (Vitablocs Mark II and Vita In-Ceram Alumina). Three different size groups (cubes) were prepared of both materials in order to investigate the chemical solubility of the varied geometrical specimens. The surface microstructure of test specimens was analyzed by scanning electron microscope (SEM, CamScan) before and after the solubility test.
Results: It was found that increasing the individual surface area of the specimens across the range permitted by ISO 6872:2008 resulted in a decreasing chemical solubility rate (Table 1). ANOVA indicated a significant difference between groups 1 and 2, and 1 and 3. Particularly, the present outcomes possibly indicated as the overall sample edge length increases, the chemical solubility also increases. The SEM images indicated that the edges of the specimens were more vulnerable to chemical dissolution than other areas of a specimen.
Conclusions: Although the results of the current ISO chemical solubility test appear with low variability, these results can be manipulated by modifying the specimens’ dimensions or morphology. Maintaining a standard surface area, the chemical solubility decreases as the sample size increased for both ‘enamel’ and ‘core’ classes of dental ceramics. The test did not succeed to improve the reproducibility of solubility measurement. It is recommended that the test be amended to stipulate sample morphology and geometry.