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

Unveiling the Role of Metal Ion Concentration versus Immune Sensitization in Orthodontic Patients-A Long-Term Prospective Evaluation

Background: This longitudinal prospective study aimed to assess orthodontic patients' immune system response to metal ion release in saliva. Methods: Thirty adult patients (18-35 years) were equally divided into three groups: groups at the end (G1) and beginning (G2) of multibracket appliances (MBA) treatment and a non-treated control group (G3). Participants were evaluated at four timepoints within 21 days, with saliva samples being analyzed for metal ion concentrations and blood for the lymphocyte transformation test (LTT). Results: There were no significant differences between groups or timepoints for saliva. LTT analyses revealed hypersensitivity in one-third of all patients and 50% of G2 for nickel, with three developing sensitizations after MBA insertion. All nickel-sensitized patients exhibited varying elevated saliva nickel concentrations. The most nickel-sensitized patients had low ion saliva loads. In borderline nickel-sensitization cases, saliva ion concentrations were up to 20 times higher than the reference. Hypersensitivity to palladium, gold, and mercury was also observed. Conclusions: These findings indicate that increased MBA ion release was not inherently linked to the immune response (Type-IV sensitization), as reactions occurred even with ion levels below thresholds. This underlines the need for a comprehensive evaluation of the immune response to metal ion release in orthodontic patients.

Transport Properties in Multicomponent Systems Containing Cyclodextrins and Nickel Ions

In this work, we propose a comprehensive experimental study of the diffusion of nickel ions in combination with different cyclodextrins as carrier molecules for enhanced solubility and facilitated transport. For this, ternary mutual diffusion coefficients measured by Taylor dispersion method are reported for aqueous solutions containing nickel salts and different cyclodextrins (that is, α-CD, β-CD, and γ-CD) at 298.15 K. A combination of Taylor dispersion and other methods, such as UV-vis spectroscopy, will be used to obtain complementary information on these systems. The determination of the physicochemical properties of these salts with CDs in aqueous solution provides information that allows us to understand solute-solvent interactions, and gives a significant contribution to understanding the mechanisms underlying diffusional transport in aqueous solutions, and, consequently, to mitigating the potential toxicity associated with these metal ions. For example, using mutual diffusion data, it is possible to estimate the number of moles of each ion transported per mole of the cyclodextrin driven by its own concentration gradient.

Graphene-Based Coatings for Surface Modification and Their Applications in Fixed Orthodontics: A Scoping Review

BACKGROUND

Surface coating technology can assist fixed appliances by reducing friction, improving antibacterial characteristics, and increasing corrosion resistance. The application of functional coatings composed of graphene onto the surfaces of orthodontic brackets and archwires has been shown to enhance their mechanical qualities. The objective of the current study was to carry out a scoping analysis of published recent evidence on the utilization of graphene as a covering material in metallic orthodontic accessories, such as brackets and archwires; Methods: A scoping review was undertaken following the PRISMA-ScR guidelines. PubMed, Embase, the Cochrane Library, Dentistry and Oral Science Source, and Google Scholar were searched between 2003 and 2023; Results: In total, 38 potential references were detected, from which 10 were selected for this review. These articles addressed the benefits of the application of graphene-oxide functional coatings onto the surface of archwires and brackets during fixed orthodontic treatment. Orthodontic graphene-oxide-based coatings provide improved surface characteristics (e.g., reduced friction and anticorrosive effects), antibacterial capabilities, and biocompatibility. These characteristics can increase the effectiveness of orthodontic therapy, improve patient comfort, and lower the likelihood of problems; Conclusion: Orthodontists should be aware of and comprehend the prerequisites for using graphene-oxide-coated archwires and brackets to fulfill needs throughout their clinical practice.

Metal Release and Cytotoxicity of Different Orthodontic Bracket-Wire Combinations: An In Vitro Study

Aim

To quantify and compare the metal ions released from different bracket-wire combinations and to assess their cytotoxicity.

Materials and Methods

A total of 360 fabricated sectional fixed orthodontic appliances were divided into 6 groups. The first three groups consisted of stainless-steel brackets with stainless-steel, snickel-titanium (NiTi), and titanium-molybdenum alloy (TMA) archwires, and the other three groups were fabricated using ceramic brackets (polycrystalline alumina) with stainless-steel, NiTi, and TMA archwires. These appliances were immersed in artificial saliva (pH 6.5 ± 0.5, 37°C), for 1 week, 2 weeks, and 1 month. The nickel and chromium ions released in the artificial saliva were quantified using a flame atomic absorption spectrometer, and cytotoxicity assessment was performed using a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay on human cervical cancer cell line.

Results

The stainless-steel bracket groups displayed a significantly greater release of nickel and chromium ions compared to the ceramic bracket groups (P < 0.05). However, no significant differences were identified when comparing the three archwire types within the stainless-steel/ceramic bracket groups. At the end of 1 month, the % cell viability demonstrated by the appliances was in the decreasing order of stainless-steel-TMA > ceramic-stainless steel > stainless-steel-NiTi > ceramic-NiTi > stainless-steel-stainless steel > ceramic-TMA.

Conclusion

Considerably greater release of nickel and chromium ions was observed from the appliances utilizing stainless-steel brackets compared to those employing ceramic brackets. However, no remarkable difference in the levels of nickel and chromium ions was observed when comparing the three archwires: stainless steel, NiTi, and TMA. In the cytotoxicity assessment, the ceramic-TMA combination displayed the highest level of cytotoxicity, while the stainless-steel-TMA combination displayed the least cytotoxicity.

Nickel and copper ion release, deflection and the surface roughness of copper-nickel-titanium orthodontic archwire in sodium fluoride solution

OBJECTIVE

Sodium fluoride (NaF) is commonly used in oral hygiene products, leading to corrosion and reduced archwire properties. In addition, ion release can cause allergies and become toxic to the oral environment. This research aimed to observe the Nickel (Ni) and Copper (Cu) ions released that affected initial corrosion as deflection and surface roughness changed in the Copper-Nickel-Titanium (CuNiTi) archwire.

MATERIAL AND METHODS

The total samples were 54 copper-nickel-titanium (CuNiTi-Tanzo, American orthodontic®) archwires immersed in three solutions. Artificial saliva was used in the control group NaF 0.05%, and a NaF 0.15% solution was used in the intervention groups (n = 6). The groups were divided into three observation times (two, four, and six weeks). Cu and Ni ions released, deflection, the surface roughness of the archwires, and solution acidities were recorded and analyzed.

RESULTS

Ni and Cu ion release and surface roughness of the CuNiTi archwires significantly increased as the NaF concentration increased. The Ni ion release improved along the immersion period; the opposite was true for the Cu ion release. The solutions became more alkaline after the CuNiTi archwires were immersed. The pH and the archwires' deflections of the three solutions did not show significant differences.

CONCLUSION

The NaF increased Cu-Ni ion release and surface roughness but not the deflection force of the CuNiTi. The increase was affected by the concentration and duration of immersion.

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.

Toxicity of Orthodontic Brackets Examined by Single Cell Tracking

Subtle toxic effects may be masked in traditional assays that average or summate the response of thousands of cells. We overcome this by using the recent method of single cell tracking in time-lapse recordings. This follows the fate and behavior of individual cells and their progeny and provides unambiguous results for multiple simultaneous biological responses. Further, single cell tracking permits correlation between progeny relationships and cell behavior that is not otherwise possible, including disruption by toxins and toxicants of similarity between paired sister cells. Notably, single cell tracking seems not to have been previously used to study biomaterials toxicity. The culture medium was pre-conditioned by 79 days incubation with orthodontic brackets from seven separate commercial sources. Metal levels were determined by Inductively Coupled Plasma Mass Spectrometry. Metal levels varied amongst conditioned media, with elevated Cr, Mn, Ni, and Cu and often Mo, Pb, Zn, Pd, and Ag were occasionally found. The effect on human dermal fibroblasts was determined by single cell tracking. All bracket-conditioned media reduced cell division (p < 0.05), while some reduced cell migration (p < 0.05). Most bracket-conditioned media increased the rate of asynchronous sister cell division (p < 0.05), a seemingly novel measure for toxicity. No clear effect on cell morphology was seen. We conclude that orthodontic brackets have cytotoxic effects, and that single cell tracking is effective for the study of subtle biomaterials cytotoxicity.

Metal Release and Surface Degradation of Fixed Orthodontic Appliances during the Dental Levelling and Aligning Phase: A 12-Week Study

The purpose of the present study is twofold: (i) to assess the salivary nickel, chromium, and iron concentrations and (ii) to characterize the surface microstructure of the typical commercially available Ni-containing metallic appliances during the first 12-week orthodontic treatment period. A total of 85 unstimulated saliva samples were collected from patients before treatment, after 2 days, and after 1, 4, and 12 weeks. Salivary ion concentrations were determined by inductively coupled plasma optical emission spectroscopy, and data were analyzed with the Statistical Package for Social Sciences (IBM SPSS) software. The recorded mean metal concentrations were in the ranges of 132–175 µg/L for Ni, 171–192 µg/L for Cr, and 826–1023 µg/L for Fe. No statistically significant variations were observed between the different study times, and the null hypothesis (the concentrations of metallic ions in patients’ saliva did not significantly change after the placement of the orthodontic appliances) was accepted (p > 0.05). Mean salivary metallic ions were below toxic levels, and no adverse clinical reactions were registered. The intraoral surface degradation of the fixed components was corroborated by optical microscopy, scanning electron microscopy, and energy dispersive spectrometry. Microstructural analysis after complete orthodontic procedure confirmed different corrosion types, from pitting to biocorrosion.

Toxicological Profile of Biological Environment of Two Elastodontic Devices

Malocclusion and teething problems are common health problems globally, affecting people of all ages, especially children and adolescents. In addition to the pathophysiological complications associated with orthodontic problems, they also affect the well-being of the individual. Orthodontic appliances are frequently used, even from an early age, and their activity in different biological environments is very varied and incompletely described. Due to these considerations, the purpose of the study was to evaluate the toxicological profile of the biological environment (saliva at three pH values: 3, 7, and 10) of two elastodontic orthodontic appliances: Myobrace (MB) and LM TrainerTM 2 (LMD). In vitro techniques applied were conducted on human keratinocytes to evaluate cell viability (Alamar blue assay) and gene expression real-time reverse transcription–polymerase chain reaction (RT-PCR technique). In addition, it was assessed the irritating effect on the vascular plexus using as a biological model the chorioallantoic membrane of the hen’s egg by applying the hen’s egg-chorioallantoic membrane (HET-CAM) method. The obtained results showed a decrease in cell viability up to 82% in the case of LMD at pH = 3, a slight increase in mRNA expression for the anti-apoptotic marker (Bcl-2 and Bcl-xL), and a decrease in mRNA expression for the pro-apoptotic marker (Bad), and any type of toxic change at the capillary level (irritation score being below 0.9). Based on the data obtained, it can be stated that MB and LMD biological environments, at different pH values, present a safe toxicological profile.

Salivary pH Effect on Orthodontic Appliances: In Vitro Study of the SS/DLC System

Stainless steels (SS) are the most-used alloys for manufacturing fixed orthodontic appliances due to their attractive set of mechanical properties, biocompatibility, and high corrosion resistance. Nevertheless, during regular orthodontic treatments–taking at least around 2 years–the intraoral environment inevitably degrades these bioalloys, releasing metallic ions into the oral cavity. In the first part of this in vitro study, the corrosion resistance of commercial SS appliances (brackets, tubes, and bands) was evaluated in Fusayama-Meyer artificial saliva at pH values of 2.3 and 6.8 over the course of 30 days. As expected, the results corroborated that salivary pH highly influences corrosion behaviour. Released Ni, Cr, and Fe were within dietary intake values. In the second part, a novel approach for oral corrosion prevention based on the chemical inertness of DLC materials is presented. SS surfaces were functionalized with biocompatible a-C:H-sputtered coatings and submitted to the same experimental conditions. The anticorrosion ability of this system was demonstrated, preventing the pitting corrosion that occurred on the SS substrates. Despite the galvanic coupling effect due to the presence of the Cr-based interlayer, this study enhanced the potential use of the reactive sputter-deposited a-C:H coatings in orthodontics.

Can a-C:H-Sputtered Coatings Be Extended to Orthodontics?

Hydrogenated amorphous carbon (a-C:H) coatings are attractive materials for protecting metallic surfaces in extreme biological environments like the human oral cavity, due to the unusual combination of mechanical properties, superior bioinertness, and relative easier and cheaper production. In this work, two a-C:H coatings were deposited on AISI 316L substrates by reactive magnetron sputtering with two CH4 flows to assess if this outstanding system could extend its application range to orthodontics. A 30-day immersion test in Fusayama-Meyer artificial saliva was conducted to mimic an extreme acidic intraoral pH. Extracts were quantified and used to perform in vitro assays with mono- and co-cultures of macrophages and fibroblast to assess cell viability, while mechanical and structural behaviors were studied by nanoindentation and visible Raman. The empirically estimated H contents of ~28 and 40 at.% matched the hard and soft a-C:H coating regimes of 18 and 7 GPa, respectively. After immersion, no important structural/mechanical modifications occurred, regardless of the H content, without corrosion signs, delamination, or coating detachment. However, the adhesion-promoting Cr-based interlayer seems to reduce corrosion resistance via galvanic coupling. The highest biocompatibility was found for a-C:H coatings with the lowest H content. This study indicates that sputtered a-C:H are promising surface materials in orthodontics.

A New Setup for Simulating the Corrosion Behavior of Orthodontic Wires

The aim of this study was to create a new reliable setup to evaluate commercially available orthodontic wires used during orthodontic treatment. The setup includes various techniques applied for testing metal alloy materials. The materials were tested under extreme conditions to simulate their behavior in the mouth. The alloy composition of each wire was tested. The electrochemical (EC) testing and characterization of the corrosion performance of the wires was calculated by the electrochemical curves at pH = 1 in two different applied potentials to test the reaction of the material. The liquid collected after the EC measurements was analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) to verify the reliability of the EC curves and for a more accurate evaluation of the corrosion behavior of the wires. Therefore, the EC measurements were compared to the actual values obtained from the released ions found in the solution. At the end, a surface analysis was performed to detect corrosion on the wires. In conclusion, this study developed a setup to test and better understand the corrosion behavior and ion release of the orthodontic wires, metal alloy dental materials, and other metals used in the oral cavity. This method can contribute to dental material selection in patients with underlying health conditions.

In Vitro evaluation of immediate cytotoxicity of resterilised orthodontic bands on HGF-1 cell line

OBJECTIVES

The aim of this study was to evaluate the immediate cytotoxic effects of orthodontic molar bands, on HGF-1 cell line, after multiple times of sterilization following size selection procedure.

MATERIAL AND METHODS

48 stainless steel orthodontic molar bands were divided into 4 groups according to times of sterilization (1, 2, 4 and 8 times). A liquid extract containing the ions released from each band was prepared and the HGF-1 cell line was exposed to the extracts. 2 control groups (positive and negative) were designated. An MTT assay was performed, and the absorbance was read at 492nm in a microplate reader (Antos 2020, Austria).

RESULTS

There was no significant difference in pure optical density (OD) among the 4 groups (P=0.749) however a statistically significant difference was seen between the positive control group and other 4 groups (P<0.001).

CONCLUSION

The stainless-steel orthodontic bands used in this study were inert as manufactured and even multiple times of sterilization did not decrease the biocompatibility of these bands for clinical use. The present study shows that clinicians can sterilize the tried-in molar bands for at least 8 times without any risk of cytotoxicity for patients.

Cytotoxic evaluation of two orthodontic silver solder materials on human periodontal ligament fibroblast cells and the effects of antioxidant and antiapoptotic reagents

OBJECTIVES

To evaluate the cytotoxicity effects of two different solder materials used for orthodontic appliances on human periodontal ligament fibroblast (HPLF) cells, and to determine whether the mechanism of toxicity may involve oxidative stress and apoptosis.

MATERIALS AND METHODS

The silver solder samples (Leone and Summit) were soldered to orthodontic stainless steel bands and exposed to HPLF cells via cell culture inserts for 48 hours. Cytotoxicity effect of the soldered materials on HPLF cells was measured via tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) colorimetric assay (n = 10/sample) and morphological observation. In addition, the mechanism of cytotoxicity of the most toxic silver solder was investigated using both a caspase inhibitor Z-VAL-Ala-Asp-flu-oromethylketone (ZVAD-fmk) and the free radical scavenger Trolox (n = 8/sample). Statistical analysis was performed using one-way analysis of variance with a Bonferroni test. P < .05 was considered statistically significant.

RESULTS

Compared to the control (no treatment, cells only), both silver solders were cytotoxic (P < .001). The bands alone were significantly cytotoxic compared to the control. There was a significant difference in cytotoxicity between the stainless steel bands alone and the Summit silver solder (P < .001), but not the Leone silver solder. The Summit silver solder was more cytotoxic than the Leone silver solder (P < .05). MTT results were supported by the microscopic morphological changes of the HPLF cells. Neither ZVAD-fmk nor Trolox provided significant protection.

CONCLUSIONS

The two silver solder materials demonstrated different levels of cytotoxicity, and neither oxidative stress nor apoptosis is involved in the mechanism of cytotoxicity.

Protein carbonylation associated with nickel liberation in orthodontic gingival overgrowth

OBJECTIVE

To determine nickel levels and their impact on protein carbonylation in gum samples from patients with gingival overgrowth by orthodontic treatment.

DESIGN

A retrospective observational study with 33 patients divided into three groups. Group 1 patients with gingival overgrowth by orthodontic appliances; group 2 patients without gingival overgrowth but with a history of orthodontic treatment; group 3 patients without overgrowth and history of orthodontic appliances. Nickel level in gingiva samples was measured by atomic absorption while protein carbonylation was determined by Western Blot. Furthermore, three proteins were identified in carbonylated protein bands by mass spectrometry.

RESULTS

Statistically significant differences (p < 0,05) in tissue nickel levels among groups were established (nickel levels group 1: 1.33 ± 1.52; group 2: 0.33 ± 0.44; group 3: 0.20 ± 0.22 μg Ni/g tissue). Protein carbonylation was higher in patients with gingival enlargement (group 1) and history of appliance use (group 2) than controls (group 3). It was observed that band A of the Western blots presented the highest intensity (Rf 0.23) with an average intensity of 4.133.830 ± 1.958.569 for group 1; 4.420.146 ± 1.594.679 for group 2 and 2.110. 727 ± 1.640.721 for group 3. Also, the proteins Teneurin-4, Bromodomain adjacent to zinc finger domain protein 2B, Lysine-specific demethylase 5B, and Serum albumin, were identified from oxidized bands.

CONCLUSIONS

The gum of patients with gingival overgrowth by orthodontic appliances contains higher nickel residues and carbonylation of its proteins.

Comparison of Cell Viability and Chemical Composition of Six Latest Generation Orthodontic Wires

Orthodontic wires are made of alloys containing different metals, including nickel. It is important to evaluate their biocompatibility prior to use, owing to their long-term use in patients. This in vitro study compared the cytotoxicity and chemical composition of six latest orthodontic wires: Fantasia®, Tanzo®, FLI®, NT3®, DuoForce®, and Gummetal®. The before-use group consisted of wires that were not used in the mouth, and the after-use group consisted of wires that were used in the mouth for two months. The wires were placed in contact with human gingival fibroblasts (HGF) for 72 h, and cytotoxicity was determined using the resazurin test. The chemical composition and surface characterisation were evaluated by spectrometry and scanning electron microscopy. The groups were compared using ANOVA and Kruskal–Wallis test. Only the FLI® wires produced a 36% reduction in HGF viability (p < 0.05) and presented greater irregularities and loss of polymer structure. After-use wires showed a significant reduction in the percentage of nickel and the appearance of new elements (oxygen and carbon). Therefore, it can be concluded that no toxic ion release was noticed in this study. Rhodium-coated wires were more stable than PTFE-coated wires, and only the FLI® wires showed a slight cytotoxic effect.

In vitro and 48 weeks in vivo performances of 3D printed porous Fe-30Mn biodegradable scaffolds

Porous Fe-Mn biodegradable scaffolds fabricated by 3D printing are considered as a promising alternative biomaterial for repairing load-bearing bone defects. However, the mechanical adaptability, the thoughtful in vitro biocompatibility and especially the long-term in vivo osseointegration and biodegradation performances have not been investigated to date. Herein, the porous Fe-30Mn biodegradable scaffolds fabricated by selective laser melting (SLM) had the adjustable elastic modulus ranging from 10.04 GPa to 14.88 GPa by regulating the porosity from 37.89% to 47.17%. In vitro indirect and direct cytotoxicity as well as cell adhesion experiments demonstrated biocompatibility and a large number of cells with stretched filopodia adhered to the scaffolds. 48 weeks in vivo experiments showed that the scaffolds had no harm to liver and kidney, and exhibited long-term in vivo osseointegration performance. Volumes of the scaffolds decreased by 10.1-20.9%, and the retrieved scaffolds showed decreased elastic modulus (decreased by 34.1-42.3%) and yield strength (decreased by 15.8-23.3%) after the 48 weeks in vivo degradation. The Fe-30Mn-femoral condyle complex maintained the same level of stiffness as intact controls during 48 weeks. In summary, the porous Fe-30Mn biodegradable scaffolds fabricated by SLM could be a reliable and practical alternative for repairing load-bearing bone defects.

Are Metal Ions That Make up Orthodontic Alloys Cytotoxic, and Do They Induce Oxidative Stress in a Yeast Cell Model?

Compositions of stainless steel, nickel-titanium, cobalt-chromium and β-titanium orthodontic alloys were simulated with mixtures of Fe, Ni, Cr, Co, Ti and Mo metal ions as potential oxidative stress-triggering agents. Wild-type yeast Saccharomyces cerevisiae and two mutants ΔSod1 and ΔCtt1 were used as model organisms to assess the cytotoxicity and oxidative stress occurrence. Metal mixtures at concentrations of 1, 10, 100 and 1000 µM were prepared out of metal chlorides and used to treat yeast cells for 24 h. Every simulated orthodontic alloy at 1000 µM was cytotoxic, and, in the case of cobalt-chromium alloy, even 100 µM was cytotoxic. Reactive oxygen species and oxidative damage were detected for stainless steel and both cobalt-chromium alloys at 1000 µM in wild-type yeast and 100 µM in the ΔSod1 and ΔCtt1 mutants. Simulated nickel-titanium and β-titanium alloy did not induce oxidative stress in any of the tested strains.

Patient safety in dental care: an integrative review

Adverse events pose a serious problem for quality of healthcare. Dental practice is eminently invasive and involves close and routine contact with secretions; as such, it is potentially prone to the occurrence of adverse events. Various patient safety studies have been developed in the last two decades, but mostly in the hospital setting due to the organizational complexity, severity of the cases, and diversity and specificity of the procedures. The objective was to identify and explore studies on patient safety in Dentistry. An integrative literature review was performed in MEDLINE via PubMed, Scopus via Portal Capes, and the Regional Portal of the Virtual Health Library, using the terms patient safety and dentistry in English, Spanish, and Portuguese, starting in 2000. The research cycle in patient safety was used, as proposed by the World Health Organization to classify studies. We analyzed 91 articles. The most common adverse events were allergies, infections, diagnostic delay or failure, and technical error. Measures to mitigate the problem highlight the need to improve communications, encourage reporting, and search for tools to assist the management of care. The authors found a lack of studies on implementation and assessment of the impact of proposals for improvement. Dentistry has made progress in patient safety but still needs to transpose the results into practice, where efforts are crucial to prevent adverse events.

Functional Coatings for Orthodontic Archwires-A Review

In this literature review, the current state-of-art of coatings for orthodontic archwires’ increasing antimicrobial and relevant mechanical properties, such as surface topography, friction or corrosion resistance, has been presented. There is a growing request for orthodontic appliances, therefore, most researchers focus on innovative functional coatings to cover orthodontic archwires and brackets. Orthodontic appliances are exposed to the unfavorable oral cavity environment, consisting of saliva flow, food, temperature and appliance force. As a consequence, friction or biocorrosion processes may occur. This can affect the functionality of the orthodontic elements, causing changes in their microstructure, surface topography and mechanical properties. Furthermore, the material which the orthodontic archwire is made from is of particular importance in terms of the possible corrosion resistance. This is especially important for patients who are hypersensitive to metals, for example, nickel, which causes allergic reactions. In the literature, there are some studies, carried out in vitro and in vivo, mostly examining the antibacterial, antiadherent, mechanical and roughness properties of functional coatings. They are clinically acceptable but still some properties have to be studied and be developed for better results. In this paper the influence of additives such as nanoparticles of silver and nitrogen-doped TiO₂ applied on orthodontic brackets by different methods on the antimicrobial properties was analyzed. Future improvement of coating techniques as well as modification of the archwire composition can reduce the release of nickel ions and eliminate friction and bacterial adhesion problems, thus accelerating treatment time.

Removal of dental alloys and titanium attenuates trace metals and biological effects on liver and kidney

To determine whether the potential effects on liver and kidney caused by dental alloys could be reduced or terminated by the removal of nickel-chromium (Ni-Cr) alloy, cobalt-chromium (Co-Cr) alloy, and commercially pure titanium (CP-Ti), they were placed in the cheek pouches of Syrian hamsters according to ISO 10993-10. Then, the peak/plateau and end times of trace metals in the blood were determined with or without the removal of the dental alloys. Based on these time points, the trace metals and their effects on liver and kidney were examined. We found that trace metals released from these dental alloys and titanium were accumulated transiently in the blood, liver, and kidney but had no effect on the histopathology of the liver or kidney. Although the functions of the liver and kidney were compromised, the function of these tissues seemed to be clinically acceptable compared to those in control Syrian hamsters. In addition, the apoptotic effect on renal cells was terminated by removing the Ni-Cr and Co-Cr alloys, and that on hepatocytes was also eliminated by removing the Ni-Cr alloy. In contrast, the effect of the Co-Cr alloy on hepatocytes was temporary and recovered by itself. Taken together, Ni- and Co-based dental alloys and titanium have no effect on the histopathology or function of liver and kidney. Moreover, Ni-Cr and Co-Cr alloys induce transient trace metal accumulation and apoptotic effects in liver and kidney, which can be reduced or terminated by the removal of the alloys, while CP-Ti shows favorable biocompatibility.

Engineered metal oxide nanomaterials inhibit corneal epithelial wound healing in vitro and in vivo

Ocular exposure to metal oxide engineered nanomaterials (ENMs) is common as exemplified by zinc oxide (ZnO), a major constituent of sunscreens and cosmetics. The ocular surface that includes the transparent cornea and its protective tear film are common sites of exposure for metal ENMs. Despite the frequency of exposure of the ocular surface, there is a knowledge gap regarding the effects of metal oxide ENMs on the cornea in health and disease. Therefore, we studied the effects of metal oxide ENMs on the cornea in the presence or absence of injury. Cell viability of immortalized human corneal epithelial (hTCEpi) cells was assessed following treatment with 11 metal oxide ENMs with a concentration ranging from 0.5 to 250 μg/mL for 24 hours. An epithelial wound healing assay with a monolayer of hTCEpi cells was then performed using 11 metal oxide ENMs at select concentrations based on data from the viability assays. Subsequently, based on the in vitro results, in vivo testing of precorneal tear film (PTF) quantity and stability as well as a corneal epithelial wound healing were tested in the presence or absence ZnO or vanadium pentoxide (V₂O₅) at a concentration of 50 μg/mL. We found that WO₃, ZnO, V₂O₅ and CuO ENMs significantly reduced hTCEpi cell viability in comparison to vehicle control or the other metal oxide ENMs tested. Furthermore, ZnO and V₂O₅ ENMs also significantly decreased hTCEpi cell migration. Although ZnO and V₂O₅ did not alter PTF parameters of rabbits in vivo, corneal epithelial wound healing was significantly delayed by topical ZnO while V₂O₅ did not alter wound healing. Finally, hyperspectral images confirmed penetration of ZnO and V₂O₅ through all corneal layers and into the iris stroma. Considering the marked epithelial toxicity and corneal penetration of ZnO, further investigations on the impact of this ENM on the eye are warranted.

Oxidative Damage in Human Periodontal Ligament Fibroblast (hPLF) after Methylmercury Exposure

Human exposure to mercury (Hg) is primary associated with its organic form, methylmercury (MeHg), through the ingestion of contaminated seafood. However, Hg contamination is also positively correlated with the number of dental restorations, total surface of amalgam, and organic mercury concentration in the saliva. Among the cells existing in the oral cavity, human periodontal ligament fibroblast (hPLF) cells are important cells responsible for the production of matrix and extracellular collagen, besides sustentation, renewal, repair, and tissue regeneration. In this way, the present study is aimed at investigating the potential oxidative effects caused by MeHg on hPLF. Firstly, we analyzed the cytotoxic effects of MeHg (general metabolism status, cell viability, and mercury accumulation) followed by the parameters related to oxidative stress (total antioxidant capacity, GSH levels, and DNA damage). Our results demonstrated that MeHg toxicity increased in accordance with the rise of MeHg concentration in the exposure solutions (1-7 μM) causing 100% of cell death at 7 μM MeHg exposure. The general metabolism status was firstly affected by 2 μM MeHg exposure (43.8 ± 1.7%), while a significant decrease of cell viability has arisen significantly only at 3 μM MeHg exposure (68.7 ± 1.4%). The ratio among these two analyses (named fold change) demonstrated viable hPLF with compromised cellular machinery along with the range of MeHg exposure. Subsequently, two distinct MeHg concentrations (0.3 and 3 μM) were chosen based on LC50 value (4.2 μM). hPLF exposed to these two MeHg concentrations showed an intracellular Hg accumulation as a linear-type saturation curve indicating that metal accumulated diffusively in the cells, typical for metal organic forms such as methyl. The levels of total GSH decreased 50% at exposure to 3 μM MeHg when compared to control. Finally, no alteration in the DNA integrity was observed at 0.3 μM MeHg exposure, but 3 μM MeHg caused significant damage. In conclusion, it was observed that MeHg exposure affected the general metabolism status of hPLF with no necessary decrease on the cell death. Additionally, although the oxidative imbalance in the hPLF was confirmed only at 3 μM MeHg through the increase of total GSH level and DNA damage, the lower concentration of MeHg used (0.3 μM) requires attention since the intracellular mercury accumulation may be toxic at chronic exposures.

Genotoxic effects in oral mucosal cells caused by the use of orthodontic fixed appliances in patients after short and long periods of treatment

OBJECTIVE

This study aimed to evaluate the genotoxic effects in the oral epithelial cells of patients undergoing fixed orthodontic treatment and to compare these to a control group without treatment. The null hypothesis to be tested is that corrective orthodontic treatment at different periods does not cause genotoxic effects in patients.

MATERIAL AND METHODS

An observational cross-sectional study including 74 patients enrolled in corrective orthodontic treatment and 21 control patients, between 11 and 35 years of age, of both genders, participated in the research. Patients undergoing treatment were divided into four treatment groups differentiated by treatment periods: G1, n = 21 (1 month to 12 months); G2, n = 21 (13 to 24 months); G3, n = 23 (25 to 48 months); and G4, n = 9 (over 48 months). Cells were collected by scraping the internal side of the cheek and subsequently placed in tubes containing 0.9% sodium chloride solution. The sample underwent evaluation for genotoxic effects by means of the micronucleus test (MNT). Bivariate analyses were performed using parametric tests (t test or ANOVA) and nonparametric tests (Chi-square test, Kruskal-Wallis test, Dunn post-test). The adopted level of significance was 5%.

RESULTS

Statistically significant differences for any of the genotoxic abnormalities (binucleated, trinucleated, karyolysis, piknosis, nuclear buds) were not found except for karyolysis, which was higher in the control group than in G4 (p < 0.05).

CONCLUSIONS

This study did not demonstrate evidence of genotoxic effects even after long periods of corrective orthodontic treatment.

CLINICAL RELEVANCE

This study explores genotoxic effects in fixed orthodontic patients.

Synthesis and biomedical applications of graphitic carbon nitride quantum dots

This review summarizes the synthetic methods and addresses current applications and future perspectives of graphitic carbon nitride quantum dots in the biomedical field.

Genotoxic and cytotoxic effects of Haas appliance in exfoliated buccal mucosa cells during orthodontic treatment

OBJECTIVES

To evaluate the genotoxic and cytotoxic effects of Haas appliances through micronuclei test and cytogenetic damage analysis in buccal mucosa epithelial cells of patients undergoing orthodontic treatment.

MATERIALS AND METHODS

Twenty-eight patients, 6-12 years of age and of both genders, who required a Haas appliance for the correction of a posterior crossbite were included. Epithelial cells from the mucosa were collected by gently scraping the inside of both the right and left cheeks. The cells were collected before the insertion of the appliance (T0), 1 month after the device was installed (T1), and again 3 months after the appliance was immobilized (T2). The cells were processed to obtain slides. Feulgen/Fast Green was used as the staining method, and the number of normal, karyolytic, pyknotic, nuclear buds, bi/trinucleated, and micronucleus cells were counted under light microscopy. Cellular abnormalities were evaluated with parametric and nonparametric tests for comparison of the means by analysis of variance testing, Tukey posttest, or the Kruskal-Wallis test and then by Dunn's posttest. The significance level was 5%.

RESULTS

There were no statistically significant changes in the micronuclei in the evaluated periods ( P > .05). Nuclear buds increased at T1 ( P < .05), returning to baseline levels at T2. Other abnormalities (cariolytic, pyknotic, and bi/trinucleated cells) showed a significant increase at T1 and T2 ( P < .0001).

CONCLUSIONS

The Haas appliance did not cause an increase in micronuclei in cells of the buccal mucosa. However, statistically significant increases in cariolytic, pyknotic, and bi/trinucleated cells were observed during treatment, suggesting possible DNA damage.

The metal content of generic orthodontic brackets compared with proprietary brackets

Background

With minimal manufacturer information, a variety of ‘generic’ orthodontic brackets are available online from overseas distributors. The present study investigated the metal composition of generic orthodontic brackets compared with two well-known ‘proprietary’ brands.

Materials and methods

Ranging in price from AU$2.99 to $65, five sets of different generic brackets were obtained directly from China via eBay (G1, G2…G5). Proprietary brackets were obtained from American Orthodontics (P1) and Rocky Mountain Orthodontics (P2). The 11, 12, 13 and 14 brackets from each set were liquefied in an acid solution and subjected to trace element analysis using inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectroscopy (ICP-OES) with respect to nickel, chromium, iron, copper, molybdenum, manganese, cadmium, mercury, arsenic and lead. Statistical analysis investigated the compositional consistency within and between each brand.

Results

The composition of P1 and P2 agreed with the manufacturer’s data. The generic groups typically had low molybdenum and higher copper content and approximated either 17-4 or AISI304 stainless steels or a combination of both. No relationship between brand and consistency of manufacture could be identified. The cheapest bracket contained lead.

Conclusions

Generic and proprietary brackets showed differences in their metal composition that may have biocompatibility implications.

A CAD/CAM Zirconium Bar as a Bonded Mandibular Fixed Retainer: A Novel Approach with Two-Year Follow-Up

Stainless steel alloys containing 8% to 12% nickel and 17% to 22% chromium are generally used in orthodontic appliances. A major concern has been the performance of alloys in the environment in which they are intended to function in the oral cavity. Biodegradation and metal release increase the risk of hypersensitivity and cytotoxicity. This case report describes for the first time a CAD/CAM zirconium bar as a bonded mandibular fixed retainer with 2-year follow-up in a patient who is subjected to long-term treatment with fixed orthodontic appliance and suspected to have metal hypersensitivity as shown by the considerable increase of nickel and chromium concentrations in a sample of patient's unstimulated saliva. The CAD/CAM design included a 1.8 mm thickness bar on the lingual surface of lower teeth from canine to canine with occlusal rests on mesial side of first premolars. For better retention, a thin layer of feldspathic ceramic was added to the inner surface of the bar and cemented with two dual-cured cement types. The patient's complaint subsided 6 weeks after cementation. Clinical evaluation appeared to give good functional value where the marginal fit of digitized CAD/CAM design and glazed surface offered an enhanced approach of fixed retention.

A new design of a Nitinol ring-like wire for suturing in deep surgical field

The present work proposes a new suturing procedure based on self-accommodating suture points. Each suture point is made of a commercial NiTi wire hot-shaped in a single loop ring; a standard suture needle is then fixed at one end of the NiTi suture. According to this simple geometry, several NiTi suture stitches have been prepared and tested by tensile test to verify the closing force in comparison to that of commercial sutures. Further experimental tests have also been performed on anatomic samples from animals to verify the handiness of the NiTi suture. Moreover, surface quality of sutures has been carefully investigated via microscopy. Results show that the NiTi suture expresses high stiffness and a good surface quality. In addition, the absence of manual knotting allows for a simple, fast and safe procedure.