Aesthetics have become increasingly crucial when it comes to determining the success of dental treatment, and in recent years, the demand for a better look has grown exponentially. The number of adults seeking orthodontic care increased from 14% to 27% between 2010 and 2014, based on a survey conducted by the American Association of Orthodontics back in 2015 [
An ideal outcome of bracket bonding to any surface should result in an attachment that is strong enough to endure the forces of orthodontic treatment and mastication without dislodgement, while at the same time be safe enough to avoid damage to the surface during debonding following the end of the treatment [
Although bands can be placed on restored teeth to overcome this obstacle, particularly in the posterior region, this might not be an acceptable solution in the anterior areas because of esthetic considerations. This is especially important in the interdental area due to the heightened rate at which recession occurs [
Patients are frequently given comprehensive treatment plans involving orthodontic procedures in order to achieve the best appearance, and practitioners find themselves having to place orthodontic brackets (OB) on a variety of restorations. The purpose of this study is to serve as a clinical guideline for the safest and most effective approaches taken to condition various surfaces for bonding to OB and provide background knowledge on the subject.
PubMed and EBSCO databases were searched, along with the use of Google Scholar search engine, to obtain relevant articles published in peer-reviewed journals. Only articles published in English were included and dated from 1955 to 2020. Older articles were used either as reference for the history and background information of the materials discussed in the article, due to the scarcity of recent literature on a particular subject, or to show the consistency of results between earlier and more recent test results. References of the obtained studies were also checked to minimize the possibility of missing any relevant studies. The obtained studies were assessed by two reviewers independently. Any disagreements were settled with a discussion with the third author.
The following keywords were used: Shear bond strength; Orthodontic bracket; Base design; Etching; Sandblasting; Laser; Conditioning; Enamel; Ceramic; Porcelain; Gold; Amalgam; Composite.
Bracket bases come in different shapes and forms. The design of the bracket base is a factor that influences bond strength to the attached surface. These designs include, but are not limited to, beaded, large-round-pitted, irregular, and metal mesh bases. It is difficult to determine which base design is superior as certain base designs performed particularly well with certain cements, but not as well with others [
Another factor that influences bond strength is the material the bracket is composed of. Ceramic brackets were introduced in the mid-1980s to provide a more esthetic orthodontic treatment option [
In spite of that, the ceramic brackets achieve a higher bond strength than metal brackets [
The material of the bracket is not the only factor in regards to the risk of damaging enamel during debonding. While applying tensile forces can debond the bracket more easily, they are more likely to result in cohesive failure. A cohesive failure within the cement between the tooth/restoration surface and the bracket will result in remnants of cement on the surface after debonding. Furthermore, debonding the bracket improperly may damage the enamel. This can occur in the form of cracks or fractures macroscopically or microscopically. This can be associated with complications including poor appearance, hypersensitivity, and a higher susceptibility to pulp inflammation and caries [
Conditioning of enamel is necessary to obtain a surface topography capable of providing retention to the cement, as well as the fact that the enamel surface, over time, loses its properties as it reacts with the various ions and particles present in saliva after exposure for long periods [
The current protocol for bonding brackets to enamel is to use 37% of OPhA for 15 seconds over the surface to be etched [
It should be noted that decalcifying the inorganic component of enamel makes it more susceptible to dental caries. This vulnerability is further exacerbated by the increased risk of plaque buildup around the OB [
The primary benefit of using lasers over acids is the effect of demineralization on enamel in the case of the latter [
Biocompatibility, a natural-looking appearance, and superior biomechanical properties are the characteristics of dental ceramics that led to their popularity as indirect restorative materials in modern restorative dentistry [
Acid is typically used to condition the surface for bonding. Two important factors to consider when conditioning a porcelain surface for bonding are the concentration of the etchant used and the amount of time that the surface is subjected to it. Increasing the exposure time will not necessarily result in a higher SBS. Contrarily, there are accounts of the SBS decreasing as a result of prolonged etching [
HFA requires special care when used in the oral cavity, as skin or mucosal exposure to a concentration as low as 0.1% may cause slow-healing-burns [
A neutralizing agent, such as CaCO3 or NaOCl, is recommended to be used after the application of HFA to eliminate any remaining acidity after washing off the acid. Etching with 9.6% HFA can achieve high bond strengths between ceramic and adhesive resins by reacting with the glass phase and secondary crystalline phase, while leaving the main crystalline phase intact [
Clinicians are challenged with having to bond orthodontic appliances to resin composite restorations or resin laminate veneers [
Significantly higher bond strengths are achieved with the use of ceramic brackets, and its use was recommended by Eslamian et al. [
Understandably, few tests were performed on amalgam conditioning methods for orthodontic purposes. Zachrisson et al. were the first to attempt orthodontic bonding brackets to amalgam [
Early methods of surface preparation involved the use of greenstone [
A systematic review on bonding OB to ceramic by Grewal Bach et al. concluded that etching with 9.6% HFA followed by silane application is the best protocol [
Panah et al. have suggested the use of patient-oriented protective measures such as neutralizing agents and rubber dams [
A recent study by Lyons et al. found that there is no statistical significance in SBS resulting from the use of HFA, AA, or OPhA as lithium disilicate conditioning agents with the use of Assurance Plus (Reliance Orthodontic Products; Illinois, USA) and Transbond XT (3M Unitek Orthodontics, Minnesota, USA) [
A study by Kwak et al. to evaluate the effect of different conditioning techniques on glazed zirconia yielded interesting results [
No significant correlation was found between roughness and bond strength values [
Newman [
Reynolds et al. reported that 5.88–7.84 MPa, more commonly cited as 6–8 MPa, is the maximum amount of tensile forces that brackets are subjected to [
Akova et al. stated that laboratory findings should not be interpreted as clinical recommendations because many environmental factors that potentially influence the bond strength of brackets to ceramic cannot be replicated in vitro [
Optimal bracket base design is difficult to determine as each base design reacts differently according to the bracket material and resin cement used. OPhA is the golden standard for conditioning enamel. Many studies have shown the effectiveness of lasers as an alternative to avoid demineralization; however, more studies are needed to verify their results due to the presence of contradicting literature. The current protocol is to use 9.6% HFA to condition ceramic; however, 5% HFA conditions ceramic just as well. In either case, HFA is toxic, and its intraoral use should be avoided altogether. Alternatives such as OPhA, CO2 laser, and AA with CoJet-Sand are also effective, and their use should be considered by clinicians. Monobond Etch & Prime is toxic and should not be used intraorally to condition ceramics. Using ceramic brackets and roughening composite surfaces with a bur achieves the best results. AA is the standard technique for conditioning both amalgam and gold surfaces. More recent studies showed that laser ablation gave better results for amalgam, while using AA with CoJet-Sand improves bonding for gold alloys. Finally, it is unclear how the value of 6–8 MPa came to be widely regarded as the maximum value of shear forces that an OB is subjected to. Therefore, it should not be used as a reference when testing SBS of OB.
The authors declare that they have no conflicts of interest.