Risk Assessment of Oxidative Stress Induced by Metal Ions Released from Fixed Orthodontic Appliances during Treatment and Indications for Supportive Antioxidant Therapy: A Narrative Review

Orthodontic Alloy Wires and Their Hypoallergenic Alternatives: Metal Ions Release in pH 6.6 and pH 5.5 Artificial Saliva

Legislative framework addresses the issues of alloy corrosion, demanding the restricted use of probable carcinogenic, mutagenic, and toxic-for-human-reproduction (CMG) metals like nickel, cobalt, and chromium and demanding the development of new biomaterials. The aim of this research was to evaluate and compare the ion release of standard dental alloys and their hypoallergenic equivalents. Six types of orthodontic alloy wires (nickel-titanium (NiTi), coated NiTi, stainless steel (SS), Ni-free SS, and cobalt-chromium (CoCr) and titanium-molybdenum (TMA) were immersed into artificial saliva of pH 5.5 and 6.6. Release of metal ions was measured by inductively coupled plasma-mass spectrometry after 3, 7, 14 and 28 days. The data were analyzed using analysis of variance, and results with p < 0.05 were considered significant. NiTi released more Ti and Ni ions compared to the coated NiTi; SS released more iron, chromium, and nickel compared to the nickel-free SS. CoCr released cobalt in a high concentration and low amounts of chromium, nickel, and molybdenum compared to the molybdenum and titanium released by TMA. Release of metals from dental orthodontic alloys in vitro was overall lower at pH 6.6 and for the hypoallergenic equivalents when compared to standard dental alloys.

Streptococcus mitis enhances metal-induced apoptosis in reconstructed human gingiva but not skin

BACKGROUND

Commensal bacteria colonizing oral mucosa and skin play an essential role in maintaining host-microbiome homeostasis. It is unknown whether cytotoxicity resulting from metal ions leaching from medical devices may be influenced by commensal microbes.

OBJECTIVE

Determine whether the extent of apoptosis triggered by nickel or titanium ions is influenced by Streptococcus mitis and whether apoptosis occurs via the intrinsic or extrinsic apoptosis pathway.

METHODS

Reconstructed Human Gingiva (RHG) and Skin (RHS) were topically exposed to titanium or nickel salts in the presence or absence of S. mitis. Cytotoxicity and apoptosis were assessed by histology, immunohistochemistry, TUNEL assay, and Western Blot.

RESULTS

S. mitis alone resulted in negligible cytotoxicity. After metal exposure, localized apoptosis was observed in the epithelium and fibroblasts within the lamina propria hydrogel of both RHG and RHS. S. mitis enhanced metal-mediated apoptosis in gingiva but not in skin. Apoptosis was mediated via the extrinsic pathway caspase 8. Activation of the execution phase of apoptosis occurred via caspases 3 and 7, and PARP-1.

CONCLUSION

Our study supports the finding that metals have irritant, cytotoxic properties resulting in apoptosis when leaching into skin or gingiva. Particularly for gingiva, commensal microbes exaggerate this detrimental effect.

DNA fragmentation of lymphocytes and sperm cells induced by nickel released from orthodontic archwires: A preliminary study

Orthodontic brackets and archwires placed intraorally are subject to corrosion, leading to the release of cytotoxic metal ions. The aim of this study was to determine whether the use of orthodontic NiTi archwires increases systemic Ni levels and cause alterations on the DNA of cells unrelated to the oral environment such as lymphocytes and sperm cells. Human urine, semen and blood samples were collected before (baseline) sham placement of orthodontic archwires and 15 and 30 days after placement. Lymphocytes and sperm cells cells were evaluated by comet assay. Ni concentration levels in urine increased significantly between baseline and 15 days (p<0.01) and 15 and 30 days of exposure (p<0.01). Progressive decrease in sperm viability and motility was observed between the sampling periods. Lymphocytes and sperm cells showed DNA fragmentation. The increase in systemic concentration of nickel induced structural damage in the DNA of lymphocytes and human sperm cells.

Evaluating the Therapeutic Properties of Natural Products in Orthodontic and Surgical Treatment of Dentofacial Deformities: A Systematic Review of Clinical Trials

The use of natural products as alternatives to traditional pharmacological treatments in orthodontics is gaining interest due to their anti-inflammatory, antibacterial, and antioxidant properties. This systematic review synthesizes evidence from clinical trials to evaluate the efficacy of natural products in reducing inflammation and bacterial presence in orthodontic and orthognathic treatment settings. The database search was conducted across PubMed, Scopus, and Embase up to January 2024. The review focused on randomized controlled trials only. The selected studies centered on the anti-inflammatory, antibacterial, and antioxidant effects of natural products, adhering to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines for data extraction. Nine studies, totaling 358 participants, were included. Significant findings demonstrated a reduction in gingival inflammation by over 40% with the use of Aloe vera compared to chlorhexidine. Another study noted a decrease in bleeding on probing by 13.6 points in the treatment group over placebo. Additionally, honey showed a rapid modulation of plaque pH and significantly reduced bacterial counts of Streptococcus mutans. Furthermore, the use of resveratrol emulgel was linked to substantial improvements in gingival health, with a reduction in the gingival index and probing pocket depth. The results indicate that natural products can significantly enhance orthodontic treatment outcomes by reducing inflammation and bacterial levels. These products offer effective alternatives to traditional treatments and show potential for integration into routine orthodontic care protocols. Further research is encouraged to standardize application methods and dosages to maximize clinical benefits and patient satisfaction.

Lipid Peroxidation in Muscle Foods: Impact on Quality, Safety and Human Health

The issue of lipid changes in muscle foods under the action of atmospheric oxygen has captured the attention of researchers for over a century. Lipid oxidative processes initiate during the slaughtering of animals and persist throughout subsequent technological processing and storage of the finished product. The oxidation of lipids in muscle foods is a phenomenon extensively deliberated in the scientific community, acknowledged as one of the pivotal factors affecting their quality, safety, and human health. This review delves into the nature of lipid oxidation in muscle foods, highlighting mechanisms of free radical initiation and the propagation of oxidative processes. Special attention is given to the natural antioxidant protective system and dietary factors influencing the stability of muscle lipids. The review traces mechanisms inhibiting oxidative processes, exploring how changes in lipid oxidative substrates, prooxidant activity, and the antioxidant protective system play a role. A critical review of the oxidative stability and safety of meat products is provided. The impact of oxidative processes on the quality of muscle foods, including flavour, aroma, taste, colour, and texture, is scrutinised. Additionally, the review monitors the effect of oxidised muscle foods on human health, particularly in relation to the autooxidation of cholesterol. Associations with coronary cardiovascular disease, brain stroke, and carcinogenesis linked to oxidative stress, and various infections are discussed. Further studies are also needed to formulate appropriate technological solutions to reduce the risk of chemical hazards caused by the initiation and development of lipid peroxidation processes in muscle foods.

Oxidative Stress and Natural Products in Orthodontic Treatment: A Systematic Review

In recent years, orthodontics, a specialized branch of dentistry, has evolved considerably in terms of both techniques and materials used. Aimed at correcting dental malocclusions and craniofacial anomalies, it improves the functionality and aesthetics of the face and oral cavity. However, orthodontic treatment, in its developmental stages, may induce oxidative stress (O.S.) phenomena, with an increase in the production of reactive oxygen species (ROS), damaging the dental and periodontal tissues involved, affecting the short-, medium- and long-term results. Studies on the antioxidant effects of natural products (e.g., resveratrol, green tea, turmeric, etc.) in the medical field have aroused considerable interest in recent years. A systematic literature review was conducted on the PubMed, Scopus, and Web of Science databases using natural products (N.P.s), O.S., and orthodontic as keywords. The study aims to consider the determinants of the increase in ROS occurring during orthodontic treatment and the possibility of natural products being able to control and neutralize biochemical phenomena by restoring the physiological process in which the balance between the production of ROS and the ability of the body's antioxidant system to neutralize them is in favor of the latter.

Corrosion of Fixed Orthodontic Appliances: Causes, Concerns, and Mitigation Strategies

The orthodontic supply market is a prosperous billion-dollar industry, driven by an increasing demand for orthodontic appliances. The supremacy of metallic first-generation biomaterials is evident for manufacturing brackets, archwires, bands, and other components due to their well-recognized chemical inertness, spontaneous passivation, biocompatibility, and favorable mechanical properties combination. However, the oral cavity is the ultimate corrosion-promoting environment for any metallic material. In this work, the general picture of the intraoral degradation of fixed orthodontic appliances is first addressed, from the causes to the harmful effects and their oral clinical implications. Current mitigation strategies are also pointed out, including the alloys’ bulk composition adjustment combined with new and advanced manufacturing processes and/or their surface treatment or coating deposition. The versatile use of thin films and coatings stands out with different deposition technologies: Many in vivo and in vitro efforts have been devoted to oral aging, from monolithic to composite architectures and micro- to nano-scale materials, to meet the best and safest oral practice demands. Unfortunately, literature data suggest that even the existing commercially available protective coatings have drawbacks and are fallible. Further multidisciplinary research is still required to effectively mitigate the corrosion behavior of fixed orthodontic appliances.

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.

Engineering Antioxidant Surfaces for Titanium-Based Metallic Biomaterials

Prolonged inflammation induced by orthopedic metallic implants can critically affect the success rates, which can even lead to aseptic loosening and consequent implant failure. In the case of adverse clinical conditions involving osteoporosis, orthopedic trauma and implant corrosion-wear in peri-implant region, the reactive oxygen species (ROS) activity is enhanced which leads to increased oxidative stress. Metallic implant materials (such as titanium and its alloys) can induce increased amount of ROS, thereby critically influencing the healing process. This will consequently affect the bone remodeling process and increase healing time. The current review explores the ROS generation aspects associated with Ti-based metallic biomaterials and the various surface modification strategies developed specifically to improve antioxidant aspects of Ti surfaces. The initial part of this review explores the ROS generation associated with Ti implant materials and the associated ROS metabolism resulting in the formation of superoxide anion, hydroxyl radical and hydrogen peroxide radicals. This is followed by a comprehensive overview of various organic and inorganic coatings/materials for effective antioxidant surfaces and outlook in this research direction. Overall, this review highlights the critical need to consider the aspects of ROS generation as well as oxidative stress while designing an implant material and its effective surface engineering.

Toxicity of Metal Ions Released from a Fixed Orthodontic Appliance to Gastrointestinal Tract Cell Lines

The mechanism of toxicity and cellular response to metal ions present in the environment is still a very current area of research. In this work, which is a continuation of the study of the toxicity of metal ions released by fixed orthodontic appliances, eluates of archwires, brackets, ligatures, and bands are used to test the prooxidant effect, cytotoxicity, and genotoxicity on cell lines of the gastrointestinal tract. Eluates obtained after three immersion periods (3, 7, and 14 days) and with known amounts and types of metal ions were used. Four cell lines-CAL 27 (human tongue), Hep-G2 (liver), AGS (stomach) and CaCo-2 (colon)-were treated with each type of eluate at four concentrations (0.1×, 0.5×, 1.0×, and 2.0×) for 24 h. Most eluates had toxic effects on CAL 27 cells over the entire concentration range regardless of exposure time, while CaCo-2 proved to be the most resistant. In AGS and Hep-G2 cells, all samples tested induced free radical formation, with the highest concentration (2×) causing a decrease in free radicals formed compared to the lowest concentrations. Eluates containing Cr, Mn, and Al showed a slight pro-oxidant effect on DNA (on plasmid φX-174 RF I) and slight genotoxicity (comet assay), but these effects are not so great that the human body could not "resist" them. Statistical analysis of data on chemical composition, cytotoxicity, ROS, genotoxicity, and prooxidative DNA damage shows the influence of metal ions present in some eluates on the toxicity obtained. Fe and Ni are responsible for the production of ROS, while Mn and Cr have a great influence on hydroxyl radicals, which cause single-strand breaks in supercoiled plasmid DNA in addition to the production of ROS. On the other hand, Fe, Cr, Mn, and Al are responsible for the cytotoxic effect of the studied eluates. The obtained results confirm that this type of research is useful and brings us closer to more accurate in vivo conditions.

A Critical Appraisal of the Use and Properties of Nickel-Titanium Dental Alloys

Nickel-titanium (NiTi) archwires are used in dentistry for orthodontic treatment. NiTi alloys have favourable mechanical characteristics, such as superelasticity and shape memory, and are also known as a corrosion-resistant alloy. In specific cases, an archwire could be attacked by certain types of corrosion or wear degradation, which can cause the leaching of metal ions and a hypersensitive response due to increased concentrations of Ni in the human body. A systematic search of the literature retrieved 102 relevant studies. The review paper focuses on three main fields: (i) electrochemical properties of NiTi wires and the effect of different environments on the properties of NiTi wires (fluoride and low pH); (ii) tribocorrosion, a combination of chemical and mechanical wear of the material, and (iii) the biocompatibility of NiTi alloy and its subsequent effect on the human body. The review showed that corrosion properties are affected by microstructure, pH of saliva and the presence of fluorides. A high variation in published results should be, therefore, interpreted with care. The release of nickel ions was assessed using the same unit, showing that the vast majority of metal ions were released in the first few days of exposure, then a stable, steady state was reached. In tribocorrosion studies, the increased concentrations of Ni ions were reported.