Genotoxicity of corrosion eluates obtained from orthodontic brackets in vitro

Heat shock protein 70 and the extent of nuclear damage in periodontal ligament compression side cells with orthodontic force application - An ex-vivo evaluation

OBJECTIVE

Increased levels of heat shock proteins after several types of stress play a central role in cellular homeostasis allowing for continued cell survival. This study was aimed at quantitatively analysing the expression pattern of major damage associated molecular patterns (DAMPs) - HSP70, and the amount of nuclear damage incident in periodontal ligament compression side cells.

MATERIAL AND METHODS

Sixteen subjects with bimaxillary dentoalveolar protrusion requiring extraction of all first premolars as part of orthodontic treatment were selected. Extractions were carried out pretreatment from control group. In the experimental group, a buccally directed spring, with force range of 70-120gms promoting bodily movement of maxillary first premolars was placed. Periodontal ligament was scraped from the middle third of the root from the compression side, the cells were isolated and cultured followed by HSP70 protein estimation with western blot analysis and the extend of nuclear damage was assessed with COMET assay.

RESULTS

Western Blot analysis of HSP70 revealed a statistically significant increased expression of HSP70 (P<0.05; CI=95%) in the force applied group compared with the control group. COMET assay could demonstrate significant amount of nuclear fragmentation in the compression side periodontal ligament cells in comparison to control group (P<0.05; CI=95%).

CONCLUSIONS

All these findings demonstrated, for the first time, that orthodontic force application augments release of HSP70 from periodontal ligament cells as a measure to restore tissue homeostasis. Further the study demonstrated that orthodontic forces induce DNA fragmentation, which is quantified more than double the amount observed in the control group.

In Vitro Determination of Genotoxicity Induced by Brackets Alloys in Cultures of Human Gingival Fibroblasts

Orthodontic brackets release ions that can be reabsorbed in the oral mucosa, potentially causing complications, including cytotoxic effects and mutagenic alterations. The aim was to evaluate the genotoxicity induced by orthodontic appliance alloys in cultures of human gingival fibroblasts by comet assay. Eluates were obtained from the following brackets alloys: EconoLine (SS: stainless steel), MiniMirage (Ni-Ti: nickel-titanium), Nu-Edge (Co-Cr: cobalt-chromium), In-Vu (PC-polycrystals (PC) aluminum oxide), and Monocrystal IZE (monocrystalline (MC) aluminum oxide). Each bracket was sterilized and exposed to a corrosive process for 35 days. The obtained eluates were tested for genotoxicity of human gingival fibroblasts (HGFA) by the alkaline comet assay. All study groups showed genotoxic effects; there was a significant difference (p < 0.0001) among groups. The eluates obtained from Ni-Ti showed a 16-times greater genotoxic effect. There were differences in genotoxicity after comparing the Ni-Ti with SS (p < 0.01) and Co-Cr brackets (p < 0.001). The ceramic was more genotoxic than metallic brackets (SS and Co-Cr), but less than the Ni-Ti. This in vitro model will be useful for further study of early DNA damage caused by brackets and other biomaterials used in the oral cavity before their introduction into the clinical setting.

Genotoxicity and cytotoxicity induced by eluates from orthodontic glass ionomer cements in vitro

The aim of this study was to investigate genotoxicity and cytotoxicity of some orthodontic glass ionomer cements commercially available by means of the single cell gel (comet) assay. For this purpose, five commercial orthodontic glass ionomer cements (Vidrion C®, Meron®, Optiband®, Multicure® and Ultra Band Lok®) were tested in murine fibroblasts in vitro. For this purpose, eluates from each cement were prepared according manufactures instructions at 0, 2, 4, 8, 18, 32 and 64 days of immersion in artificial saliva at 37 °C. All orthodontic glass ionomer cements failed to induce cytotoxicity to murine fibroblasts for all periods evaluated in this study. However, Vidrion C® was able to induce genotoxicity after 64 days of exposure to eluates. Meron® also demonstrated genotoxicity as depicted by increasing DNA damage on 2nd day. Multicure® demonstrated genotoxicity on 32nd day and Ultra band Lok on 18th, 32nd days of exposure. Taken together, our results demonstrated that orthodontic cements derived from resin-modified glass ionomer composite (Multicure®) and compomer (Ultra Band Lok®) cause genetic damage in mammalian cells in vitro.

In vitro and in vivo evidence of the cytotoxic and genotoxic effects of metal ions released by orthodontic appliances: A review

Intraoral fixed orthodontic appliances are frequently used in the clinical practice of dentistry. They are made from alloys containing different metals at various percentages. The use of these appliances leads to the long-term exposure of patients to these materials, and the potential toxic effects of this exposure raises concerns about patient safety. Thus, the biocompatibility (corrosion behaviour and toxicity) of these materials has to be evaluated prior to clinical use. In the present report, the most recent studies in the scientific literature examining metal ion release from orthodontic appliances and the toxic effects of these ions have been reviewed with a special focus on cytotoxicity and genotoxicity. Previous studies suggest that a case-by-case safety evaluation is required to take into account the increasing variability of materials, their composition and the manufacturing processes. Moreover, in vivo toxicity studies in regard to metal release, cytotoxicity and genotoxicity are still scarce. Therefore, in vitro and in vivo monitoring studies are needed to establish cause-effect relationships between metal ion release and biomarkers of cytotoxicity and genotoxicity. Further investigations could be performed to elucidate the toxic mechanisms involved in the observed effects with a special emphasis on oxidative damage.

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

Miniscrew implants are widely used nowadays in orthodontic treatments due to their good results in clinical practice. However, data regarding the biocompatibility of commercially available orthodontic miniscrews and temporary devices are very scarce, and their role as genotoxicity inducers has been not previously evaluated with the alkaline comet assay. The aim of this study was to investigate the DNA damage in buccal cells of patients subjected to orthodontic treatments. The alkaline comet assay has been applied in oral mucosa cells from patients treated with conventional orthodontic treatment in comparison to patients treated additionally with miniscrews, non-treated volunteers (control) and smoking volunteers (positive control). The application of orthodontic appliances and miniscrews induced significant and similar (2-fold) increases of %DNA in tail in comparison to control group. Females experienced a significant increase in %DNA in all the treatments in comparison to the control group, whereas males showed significant damage only with the combined orthodontic and miniscrew treatment. In conclusion, conventional orthodontic appliances induced genotoxicity, and the incorporation of miniscrews assayed did not imply any additional increase of DNA damage.

In vitro oxidative stress induced by conventional and self-ligating brackets

OBJECTIVE

To determine the in vitro oxidative stress induced by conventional and self-ligating brackets made of different materials.

MATERIALS AND METHODS

The concentration of oxidative stress marker 8-hydroxy-2'-deoxyguanosine (8-OHdG) in DNA of murine fibroblast cells L929 after in vitro exposure to three types of conventional and four types of self-ligating brackets was assessed. To determine viability and changes in the number of cells before and after exposure, trypan blue dye was used. Analysis of variance (ANOVA) was used for statistical analysis.

RESULTS

No significant difference in cell viability was noted between metal, ceramic, and polymeric conventional brackets, and self-ligating brackets made of combinations of those materials, but viability was significantly higher compared with positive controls (P < .05). The conventional sapphire ceramic bracket (Inspire Ice) showed high viability, the largest increase in the number of cells, and the lowest oxidative stress. A higher concentration of markers of oxidative stress was observed in full metal conventional and self-ligating brackets (MiniSprint and Speed) and in conventional polyurethane brackets (Quantum) compared with negative controls (P < .05).

CONCLUSION

All types of orthodontic brackets, regardless of the constituent materials, are a source of oxidative stress in vitro, but the highest stress was induced in the full metal and polyurethane brackets. Conventional ceramic brackets show the highest degree of biocompatibility compared with polymeric and metal brackets and self-ligating brackets made from combinations of these materials.