Functional Coatings for Orthodontic Archwires—A Review

Abstract

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.

Improvement of Properties of Stainless Steel Orthodontic Archwire Using TiO2:Ag Coating

“…Dental plaque is formed by both supragingival and subgingival bacteria, usually Streptococcus, Actinomyces, Lactobacillus, Porphyromonas, Tannerella, Fusobacterium, Prevotella, Bacteroides, Spirochaetes [3,4]. In addition to the mechanical removal of dental plaque and the use of preparations containing agents with antimicrobial properties, the use of nanoparticles that exhibit bacteriostatic/bactericidal properties is a promising strategy for reducing bacterial adhesion to biomaterials [29][30][31]. Mhaske et al investigated the impact of coating of stainless steel and nickel-titanium archwires with a layer containing silver on the survival of Lactobacillus acidophilus.…”

In Vitro Ion Release of Wires in Removable Orthodontic Appliances

“…This amount is way below the recent stated TWI of 13 μg/kg/w [ 30 ], but it shows that the manufacturer’s data do not completely fulfil the demands of a nickel-free product. The coating of wires either for removable or fixed appliances can reduce degradation of the wires [ 31 ], especially when we note that loaded wires release even more ions into the patient’s saliva. In mouse and rat models, high nickel intakes lead to genotoxic effects in animals.…”

Effects of Composite Resin on the Enamel after Debonding: An In Vitro Study—Metal Brackets vs. Ceramic Brackets

“…On the other hand, there are studies that demonstrated that the use of pre-orthodontic treatment fluoride lacquer or varnish develops lower bond strengths, which is likely to result in a higher frequency of premature detachment of the bracket [23]. More recently, Bącela J et al [24], in their study regarding coating the orthodontic devices, as well as modifying their surface with additives, showed that this method improves their mechanical properties and can minimize bacterial adhesion on the surface. Appropriate coating techniques enable the reduction in corrosivity, wear and tear, and its delamination.…”