Functional Surface Coatings on Orthodontic Appliances: Reviews of Friction Reduction, Antibacterial Properties, and Corrosion Resistance

Evaluation of surface roughness, cytotoxicity, and antibacterial effects of silver nanoparticle coating on copper nickel titanium orthodontic arch wires - in vitro study

BACKGROUND

Surface roughness of arch wires directly impacts their corrosion behavior, friction resistance, and plaque accumulation, which may hinder tooth movement and lead to dental caries.

OBJECTIVES

The study aims to synthesize vanillin-mediated silver nanoparticles (AgNPs), characterize them, assess surface roughness and cytotoxicity of arch wires after silver nanoparticle coating, and test their antibacterial properties.

MATERIALS AND METHODS

Nine copper-nickel-titanium arch wires (CuNiTi) were cut into equal pieces. Three were sent for surface roughness assessment, three for cytotoxicity, and three for antibacterial testing. Dip coating of wires was done using the sol-gel thin film method. The surface roughness (Ra) before and after coating was evaluated using scanning electron microscopy and atomic force microscopy. Cytotoxicity testing was done with a (3- (4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay using gingival fibroblasts. Statistical analysis was done using SPSS software. Antibacterial activity against S. mutans was tested using the Agar-well diffusion method.

RESULTS

The CuNiTi wires were coated successfully, and the coating appeared homogeneous. The mean Ra after coating (297.3+/- 30.4 nm) was significantly less than that before coating (339.7+/-49.2 nm). AgNPs showed minimal cytotoxicity against human gingival fibroblasts at different concentrations. Optical microscopy showed over 90% viability between 12.5 and 100 µg/ml. At 100 µg/ml, only 80% of cells remained viable. AgNP coating is biocompatible at concentrations up to 75 µg/ml. There was a significant intergroup difference in the zone of inhibition (antibacterial activity) noted with higher values in noncoated wires. (P value <0.007).

CONCLUSION

AgNPs coated on CuNiTi arch wires showed reduced surface roughness and minimal cytotoxic effects on human gingival cells and good antibacterial activity against S. mutans compared to noncoated arch wires.

A Facile Surface Modification Scheme for Medical-Grade Titanium and Polypropylene Using a Novel Mussel-Inspired Biomimetic Polymer with Cationic Quaternary Ammonium Functionalities for Antibacterial Application

Medical device-associated infection remains a critical problem in the healthcare setting. Different clinical- or device-related methods have been attempted to reduce the infection rate. Among these approaches, creating a surface with bactericidal cationic functionality has been proposed. To do so, a sophisticated multi-step chemical procedure would be needed. Instead, a simple immersion approach was utilized in this investigation to render the titanium and polypropylene surface with the quaternary ammonium functionality by using a mussel-inspired novel lab-synthesized biomimetic catechol-terminated polymer, PQA-C8. The chemical oxidants, CuSO4/H2O2, as well as dopamine, were added into the novel PQA-C8 polymer immersion solution for one-step surface modification. Additionally, a two-step immersion scheme, in which the polypropylene substrate was first immersed in the dopamine solution and then in the PQA-C8 solution, was also attempted. Surface analysis results indicated the surface characteristics of the modified substrates were affected by the immersion solution formulation as well as the procedure utilized. The antibacterial assay has shown the titanium substrates modified by the one-step dopamine + PQA-C8 mixtures with the oxidants added and the polypropylene modified by the two-step scheme exhibited bacterial reduction percentages greater than 90% against both Gram-positive S. aureus and Gram-negative E. coli and these antibacterial substrates were non-cytotoxic.

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.

Static friction, surface roughness, and antibacterial activity of orthodontic brackets coated with silver and silver chitosan nanoparticles

BACKGROUND

To determine the effect of silver and silver chitosan nanocoatings on monocrystalline ceramic, polycrystalline ceramic, and metallic brackets regarding friction, roughness, and antibacterial effect against Streptococcus mutans.

METHODS

A total of 99 upper right premolar brackets with a 0.022 × 0.025 -inch slot were divided into three groups, each 33 according to coating material; the non-coated group, silver nanoparticles (AgNPs), and silver chitosan nanoparticles (Ag-CsNPs) groups. Each group was equally subdivided into the following three subgroups regarding bracket materials: monocrystalline ceramic, polycrystalline ceramic, and metallic brackets. A universal testing machine determined static friction on a custom-made acrylic jig. Then a profilometer machine was used to collect roughness data, and finally, the anti-cariogenic effect was measured with the disc diffusion technique's "minimum zone of inhibition" against Streptococcus mutans. Two-way ANOVA was used to compare data between groups and subgroups, followed by the Bonferroni test for multiple pair-wise comparisons.

RESULTS

The nanocoating effect on ceramic brackets' static friction was non-significant. The AgNPs and Ag-CsNPs coated metallic group revealed a significant increase in static friction-a significant effect of the nanocoating in the surface roughness of monocrystalline and polycrystalline ceramic brackets. A significant favorable effect of AgNPs and Ag-CsNPs against Streptococcus mutans was observed.

CONCLUSIONS

AgNPs and Ag-CsNPs coats are unsuitable for decreasing friction in metallic brackets or improving roughness in polycrystalline ceramic brackets. Nano coating can improve roughness in monocrystalline ceramic brackets. Coating brackets with AgNPs and Ag-CsNPs has a tremendous antibacterial effect on Streptococcus mutans, a substantial factor in the incidence of dental caries.

Bio-inspired nanocomposite coatings on orthodontic archwires with corrosion resistant and antibacterial properties

The corrosion resistance and antibacterial properties of fixed orthodontic devices are insufficient in the complex oral cavity, which delays tooth movement and causes enamel demineralization. To overcome the challenges, this research constructs a series of polydopamine-graphene oxide (PDA-GO) nanocoatings on representative NiTi archwires via self-assembly. The morphology, chemical structure, and multifunctional properties of coatings showed tunability dependent on the PDA/GO ratio. Optimized PDA-GO coatings with uniform and dense characteristics prolonged the diffusion path for the corrosive medium and reduced Ni dissolution in NiTi alloys. Meanwhile, the applied coatings endowed NiTi alloys with antibacterial activity against Streptococcus mutans due to the surface structures and inherent properties of PDA-GO. In vitro cytotoxicity tests further verified their good biocompatibility. This bio-inspired nanocomposite coating provides a practical reference for modification of dental metal surfaces to better behave in the intraoral environment.