ABSTRACT

Objectives

To evaluate the cytotoxicity effects of two different solder materials used for orthodontic appliances on human periodontal ligament fibroblast (HPLF) cells, and to determine whether the mechanism of toxicity may involve oxidative stress and apoptosis.

Materials and Methods

The silver solder samples (Leone and Summit) were soldered to orthodontic stainless steel bands and exposed to HPLF cells via cell culture inserts for 48 hours. Cytotoxicity effect of the soldered materials on HPLF cells was measured via tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) colorimetric assay (n = 10/sample) and morphological observation. In addition, the mechanism of cytotoxicity of the most toxic silver solder was investigated using both a caspase inhibitor Z-VAL-Ala-Asp-flu-oromethylketone (ZVAD-fmk) and the free radical scavenger Trolox (n = 8/sample). Statistical analysis was performed using one-way analysis of variance with a Bonferroni test. P < .05 was considered statistically significant.

Results

Compared to the control (no treatment, cells only), both silver solders were cytotoxic (P < .001). The bands alone were significantly cytotoxic compared to the control. There was a significant difference in cytotoxicity between the stainless steel bands alone and the Summit silver solder (P < .001), but not the Leone silver solder. The Summit silver solder was more cytotoxic than the Leone silver solder (P < .05). MTT results were supported by the microscopic morphological changes of the HPLF cells. Neither ZVAD-fmk nor Trolox provided significant protection.

Conclusions

The two silver solder materials demonstrated different levels of cytotoxicity, and neither oxidative stress nor apoptosis is involved in the mechanism of cytotoxicity.

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Author notes

a

Assistant Professor, Department of Orthodontics, Marquette University School of Dentistry, Milwaukee, Wis., USA.

b

Private Practice, Rosemount, Minn., USA.

c

Professor, Department of Biomaterials, Marquette University School of Dentistry, Milwaukee, Wis., USA.

d

Professor & Program Director, Department of Orthodontics, Marquette University School of Dentistry, Milwaukee, Wis., USA.

e

Assistant Professor, Department of Orthodontics, Marquette University School of Dentistry, Milwaukee, Wis., USA.

f

Professor, Department of Biomedical Science, Marquette University, Milwaukee, Wis.