Toxicity of Orthodontic Brackets Examined by Single Cell Tracking

Area of Science:

• Biomaterials Science
• Toxicology
• Cell Biology

Background:

• Traditional toxicity assays may mask subtle effects by averaging cellular responses.
• Single cell tracking offers a precise method to monitor individual cell behavior and progeny.
• This technique allows for the correlation of cell lineage with biological responses, including responses to toxicants.

Purpose of the Study:

• To investigate the cytotoxicity of orthodontic brackets using single cell tracking.
• To assess the impact of metal ions leached from orthodontic brackets on human dermal fibroblasts.
• To establish single cell tracking as a method for studying biomaterials toxicity.

Main Methods:

• Culture medium was pre-conditioned with orthodontic brackets from seven sources.
• Metal levels in conditioned media were analyzed using Inductively Coupled Plasma Mass Spectrometry.
• Human dermal fibroblasts were analyzed using single cell tracking to evaluate cell division, migration, and sister cell division synchronicity.

Main Results:

• Conditioned media showed varying levels of metals including Cr, Mn, Ni, Cu, Mo, Pb, Zn, Pd, and Ag.
• All bracket-conditioned media significantly reduced cell division (p < 0.05).
• Most media increased asynchronous sister cell division (p < 0.05), a novel indicator of toxicity, while some reduced cell migration (p < 0.05).

Conclusions:

• Orthodontic brackets exhibit cytotoxic effects on human dermal fibroblasts.
• Single cell tracking is an effective method for detecting subtle biomaterials cytotoxicity.
• The method identified increased asynchronous sister cell division as a sensitive marker for toxicity.