Biocompatibility of three orthodontic silver solder materials: in vitro cytotoxicity testing

To comparatively evaluate the in vitro cytotoxicity of three commercially available silver solder materials in different forms-traditional silver solder with flux, silver solder incorporated with flux, and silver solder paste with flux-on Balb/c 3T3 fibroblast cell lines.

Ninety-six samples were categorized into four groups: group 1 (only cell culture medium), group 2 (silver solder + flux), group 3 (universal silver solder), and group 4 (silver solder paste with flux). Each group had 24 samples assessed at three intervals: 24 h (T1), 7 days (T2), and 30 days (T3). Cytotoxicity was evaluated using the neutral red uptake assay, measuring optical density at 540 nm. Data were analyzed using one-way analysis of variance (ANOVA), Tukey's post hoc test, and paired t‑tests (p < 0.05).

All test groups exhibited increased cytotoxicity over time, with the highest toxicity observed at 24 h. Group 4 (solder paste with flux) showed the greatest cytotoxicity (96.75% nonviable cells), followed by group 2 (76.13%) and group 3 (71.83%). The control group showed minimal change (16.4%). ANOVA revealed significant differences between groups at all-time points (p < 0.001). Post hoc analysis confirmed that the solder paste group was significantly more cytotoxic than the others. Time-dependent reductions in cell viability were observed, particularly between T2 and T3.

All tested silver solder materials demonstrated cytotoxic effects on Balb/c 3T3 fibroblasts. The silver solder and flux displayed the lowest cytotoxicity, followed by universal silver solder, and silver solder paste with flux demonstrating the highest cytotoxicity. These findings highlight the need for careful material selection in orthodontic appliance fabrication to minimize adverse biological effects.