Preliminary study of genotoxicity evaluation of orthodontic miniscrews on mucosa oral cells by the alkaline comet assay

Short tandem repeat (STR) instability in the oral mucosa of patients submitted to fixed orthodontic therapy: a limitation of STR profile quality for human identification

The purpose of this study was to evaluate changes in short tandem repeat (STR) profile quality before and after fixed orthodontic therapy. Samples of oral epithelial cells were obtained from 28 volunteers who had an indication for orthodontic treatment. The samples were collected before and three months after starting orthodontic treatment with fixed appliances. DNA extraction and integrity were evaluated by electrophoresis, and STR profiles were obtained by polymerase chain reaction amplification and STR typing via capillary electrophoresis. DNA electrophoresis showed a higher proportion (7/28, 25%) of DNA degradation in the samples collected after fixed orthodontic treatment compared to those obtained before starting orthodontic therapy (3/28, 11%), however, changes in DNA were not significant (p=0.289). In concordance all STR profiles showed complete genotyping; however, imbalances in the size of heterozygotes and in the signal were detected in 25% of STR profiles after orthodontic therapy. Moreover, STR instability was demonstrated by an increase in stutter bands detected in 60% of the DNA profiles after treatment and a spurious allele of the D195433 marker was found in one sample after treatment. The STR profiles of samples obtained from the oral cavity with orthodontic appliances should be interpreted with caution. STR instability increases the incidence of artifacts that could compromise the quality of the results of tests performed in forensic DNA laboratories.

Assessment of metal ion accumulation in oral mucosa cells of patients with fixed orthodontic treatment and cellular DNA damage: a systematic review

Intraoral fixed appliances remain in the potentially corrosive environment of the mouth for an average of two years. Over time, corrosion causes the release of metal ions, such as nickel and chromium. These metals can become allergenic and cytotoxic, causing different conditions in the human body. The aim of this study therefore is to carry out a systematic review of the available scientific evidence on the accumulation of metal ions, and the genotoxic and cytotoxic effects in oral mucosa cells deriving from short- and long-term exposure to them. The systematic review is reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. The primary outcome (quantification of metal ion deposits and assessment of their genotoxic and/or cytotoxic effects) and secondary outcome (complementary analysis of cytotoxic and genotoxic effects) were examined. The Cochrane Collaboration tool and Toxicological data Reliability Assessment Tool (ToxRTool) were used for quality assessment. Once the search was performed, a total of seven articles met the inclusion criteria and were included in this study. Two main techniques were used to assess genotoxic effects: alkaline comet assay (6/7) and micronucleus method (1/7). Cytotoxicity was evaluated (4/7) using the trypan blue dye test. Accumulations of nickel (7/7), chromium (5/7), and other metals (zinc, cobalt, iron, manganese, molybdenum, titanium) were also quantified. The results allowed us to conclude that release of metal ions and acute cell and DNA damage in oral mucosa cells takes place in the early stages of treatment. However, more long-term studies are needed to evaluate chronic exposure to metals and DNA damage, as well as cellular capacity to recover DNA integrity.