Evaluations of metabolic activities as biocompatibility tools: A study of individual ions' effects on fibroblasts

Objectives: Nickel-based dental alloys have been in use since 1930. However, there are concerns regarding the release of metal ions from these alloys to surrounding tissues. Cell culture evaluations can be used to address these concerns and to develop a biocompatibility model by providing a more basic understanding of the metabolic response to individual ions released from dental alloys. This study evaluates the metabolic as well as the morphological response of cultured human gingival fibroblasts to salt solutions of ions which may be released from these alloys; beryllium (Be²⁺), chromium (Cr⁶⁺ and Cr³⁺), nickel (Ni²⁺), molybdenum (Mo⁶⁺). Methods: These evaluations include viability, lysosomal activity, oxygen consumption, membrane integrity, DNA synthesis, RNA synthesis, protein synthesis, intracellular ATP levels, and glucose-6-phosphate dehydrogenase activity. The results of all cell culture evaluations are reported as the concentration (ppm) required to cause a significant change from the controls, as determined by Duncan's multiple comparison test at 0.05 significance level. Results: While Ni²⁺ ion solutions altered metabolic functions at 3-30 ppm and Cr³⁺ and Mo⁶⁺ both at 10 and 100 ppm, Cr⁶⁺ and Be²⁺ were the most toxic causing cellular alterations at 0.04-12 ppm. Significance: These studies indicated that monitoring metabolic activities may be better than the normally used morphology and viability assays for evaluating biocompatibility.