Applications of nanotechnology in orthodontics: a comprehensive review of tooth movement, antibacterial properties, friction reduction, and corrosion resistance.

Nanotechnology has contributed important innovations to medicine and dentistry, and has also offered various applications to the field of orthodontics. Intraoral appliances must function in a complex environment that includes digestive enzymes, a diverse microbiome, mechanical stress, and fluctuations of pH and temperature. Nanotechnology can improve the performance of orthodontic brackets and archwires by reducing friction, inhibiting bacterial growth and biofilm formation, optimizing tooth remineralization, improving corrosion resistance and biocompatibility of metal substrates, and accelerating or decelerating orthodontic tooth movement through the application of novel nanocoatings, nanoelectromechanical systems, and nanorobots. This comprehensive review systematically explores the orthodontic applications of nanotechnology, particularly its impacts on tooth movement, antibacterial activity, friction reduction, and corrosion resistance. A search across PubMed, the Web of Science Core Collection, and Google Scholar yielded 261 papers, of which 28 met our inclusion criteria. These selected studies highlight the significant benefits of nanotechnology in orthodontic devices. Recent clinical trials demonstrate that advancements brought by nanotechnology may facilitate the future delivery of more effective and comfortable orthodontic care.

The corrosion resistance, cytotoxicity, and antibacterial properties of lysozyme coatings on orthodontic composite arch wires.

Objective: The corrosion resistance of new orthodontic composite arch wires (CAWs), which have excellent mechanical properties in a simulated oral environment, must be improved. This study explored the susceptibility to corrosion, in vitro cytotoxicity, and antibacterial properties of lysozyme-coated CAWs. Methods: Lysozyme coating of laser-welded CAW surfaces was prepared by liquid phase deposition. Four groups of CAW specimens were prepared: uncoated CAWs and CAWs coated with 20, 40, and 60 g L-1 lysozyme. The surface morphology of the lysozyme coatings was characterized by atomic force microscopy. The samples were immersed in artificial saliva (AS) for 2 weeks, and corrosion morphology was then observed by scanning electron microscopy. Corrosion behavior was characterized according to weight loss and electrochemical properties. The cytotoxicity and antibacterial properties of lysozyme-coated CAWs were assessed by cell counting kit-8 assay and a live/dead bacterial test, respectively. Results: Surfaces in the three lysozyme coating groups exhibited film-like deposition, the thickness of which increased with the lysozyme concentration. Surface pitting and copper ion precipitation decreased with increasing lysozyme concentration in coatings. The corrosion tendency declined as the corrosion and pitting potentials decreased. The corrosion morphology and electrochemical parameters together indicated that lysozyme coatings increased corrosion resistance. The coatings also reduced cytotoxicity to L-929 cells and increased anti-Staphylococcus aureus ability. Conclusions: Lysozyme coating of CAW surfaces by liquid phase deposition improved the corrosion resistance of CAWs. The protective coatings improved biocompatibility and endowed the CAW surfaces with certain degrees of anti-Staphylococcus aureus activity. Different lysozyme concentrations had different protective effects, with 40 g L-1 maybe being the ideal lysozyme concentration for CAW coatings.

Effect of Protein and Mechanical Strain on the Corrosion Resistance and Cytotoxicity of the Orthodontic Composite Arch Wire.

In this study, the effects of the exposure to different types of salivary proteins (fibrinogen, IgG, and mucin) and application of an in vitro bending strain on the laser welding orthodontic composite arch wire (CAW) were investigated, and the resultant corrosion behavior and cytotoxicity were studied in vitro. The purpose was to determine the mechanisms by which protein exposure and bending loads contribute to the corrosion of the CAW either alone or in combination by mimicking the clinical application. The results showed that the application of a mechanical strain significantly decreased the corrosion resistance of the CAW and increased the release of toxic corrosion products. The addition of the proteins inhibited the corrosion of the CAW, but the mechanical loads counteracted this effect. Mucin enhanced the corrosion resistance of the CAW. The effects of the proteins or strain, either alone or in combination, should be considered in the application of medical materials of heterogenetic alloys.