Oxidative stress and genotoxicity in oral epithelial cells from subjects undergoing orthodontic treatment with fixed appliances

OBJECTIVES

The objective of this work was to evaluate the impact of fixed orthodontic appliances on oxidative stress (OS) and genotoxicity from oral epithelial cells.

MATERIALS AND METHODS

Samples of oral epithelial cells were obtained from fifty-one healthy voluntary subjects who had an indication for orthodontic treatment. The samples were obtained before treatment and after 6 and 9 months of treatment. OS was evaluated by quantitating 8-hydroxy-2'deoxyguanosine (8-OHdG) and by performing relative gene expression with antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT). DNA degradation and instability were evaluated by multiplex polymerase chain reaction (PCR) and fragment analysis for human identification.

RESULTS

The quantitation results showed that 8-OHdG increased during treatment, although this increase was not statistically significant. SOD increased by 2.5- and 2.6-fold after 6 and 9 months of treatment, respectively. CAT increased by threefold after 6 months of treatment, while after 9 months of treatment, the expression level decreased to a level similar to that before treatment. DNA degradation was found in 8% and 12% of DNA samples after 6 and 9 months of treatment, respectively, while DNA instability was detected in only 2% and 8% of DNA samples after 6 and 9 months of treatment, respectively.

CONCLUSIONS

The results showed that OS and genotoxicity slightly changed after treatment with a fixed orthodontic appliance; in addition, a biological adaptation response to the treatment may occur after 6 months.

CLINICAL RELEVANCE

OS and genotoxicity in the buccal cavity are risk factors for oral and systemic diseases. This risk may be reduced through antioxidant supplementation, by using thermoplastic materials, or by reducing the orthodontic treatment time.

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.