In vitro cytotoxicity of orthodontic archwires in cortical cell cultures.
There have been a number of studies regarding the toxicity of orthodontic archwires, but little is known concerning the mechanism of their toxicity. This investigation used murine cortical cell cultures to examine the in vitro neurotoxicity of commonly used orthodontic metallic archwire alloys. The materials examined included 0.016 inch nickel-titanium (NiTi), copper-nickel-titanium, titanium-molybdenum, Elgiloy, and stainless steel archwire alloys. Standard sized samples of each material were placed on tissue culture inserts suspended above the cell cultures. Neuronal death was determined using the lactate dehydrogenase release assay 24 hours after exposure to the archwires. The results indicated that NiTi, copper-nickel-titanium and titanium-molybdenum alloys were not neurotoxic, while stainless steel and Elgiloy were significantly toxic. Washing the archwires for 7 days in a saline solution did not alter the toxicity. However, the free radical scavenger, trolox, blocked the toxicity of both stainless steel and Elgiloy, indicating that the death was free radical mediated. The caspase inhibitor, Z-VAl-Ala-Asp-fluoromethylketone (zVAD-FMK), blocked the toxicity of stainless steel, but not Elgiloy, suggesting that stainless steel induced apoptosis. Further evidence that stainless steel induced apoptosis was provided by propidium staining which showed nuclear chromatin condensation and fragmentation into discrete spherical or irregular shapes, characteristic of apoptosis. The specific metal responsible for the toxicity was not determined; the metals common to each of the toxic archwires were nickel, iron, and chromium.
David
Alexis
A
Department of Biomedical Sciences and School of Dentistry, Marquette University, Milwaukee, WI 53201, USA.
Lobner
Doug
D
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D061945:Caspase Inhibitors; D016923:Cell Death / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects*; D002839:Chromans / Q000494:pharmacology; D002858:Chromium Alloys / Q000633:toxicity; D003300:Copper / Q000633:toxicity; D003722:Dental Alloys / Q000633:toxicity*; D005609:Free Radicals / Q000037:antagonists & inhibitors; D007770:L-Lactate Dehydrogenase / Q000032:analysis; D051379:Mice; D008982:Molybdenum / Q000633:toxicity; D009474:Neurons / Q000187:drug effects*; D018696:Neuroprotective Agents / Q000494:pharmacology; D009532:Nickel / Q000633:toxicity; D009969:Orthodontic Wires; D013193:Stainless Steel / Q000633:toxicity; D014025:Titanium / Q000633:toxicity
D000590:Amino Acid Chloromethyl Ketones; D000975:Antioxidants; D061945:Caspase Inhibitors; D002839:Chromans; D002858:Chromium Alloys; D003722:Dental Alloys; D005609:Free Radicals; D018696:Neuroprotective Agents; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C040654:titanium nickelide; D013193:Stainless Steel; D003300:Copper; D009532:Nickel; D008982:Molybdenum; D014025:Titanium; D007770:L-Lactate Dehydrogenase; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid