With regard to bonding brackets, there are generally no differences between the various ligation methods, and the same selection criteria for bonding agents therefore apply.
Bonding to the natural tooth surface. Bonding to healthy enamel is a standardized procedure that involves either mechanical bonding (acid-etch technique) or chemical bonding (glass ionomer cements), or a combination of the two components (Table 6.2).
Increase in bond strength. Bonding in difficult conditions (e.g., when there is poor enamel quality, alterations in the enamel surface, deciduous teeth, composite restorations, or when moisture control is difficult) may require an adhesion booster such as Enhance (Reliance Orthodontics), which has been on the market for many years and has more recently been replaced by Assure. According to the manufacturer, this product increases the bond strength and has a greater fluoride content. Maximum Cure and Pro Seal (also Reliance Orthodontics), are also sealers but have a higher filler content than Assure and are therefore useful for sealing the tooth surface surrounding the bracket. Both products supposedly have protective characteristics, while at the same time providing bond strength comparable to that of other primers not featuring fluoride protection. The fluoride-releasing sealant is intended to protect the teeth over a 2-year period, which normally covers the duration of fixed appliance treatment.
Priming of previously filled or altered tooth surfaces. Due to the increasing numbers of adults who are seeking orthodontic treatment, orthodontists are more interested than ever to develop bonding strategies for teeth that have previously been filled with either composite, ceramic, or metal restorations. Bonding to composite almost always requires preparation of the previously polished surfaces. A chemical bond can be achieved by using a polymer conditioner (Plastic Conditioner; Reliance Orthodontics, see Table 6.3).
It is often necessary to bond to ceramic restorations such as veneers or crowns. The bonding techniques are similar to the bonding protocols for ceramic inlays and prosthetic restorations in restorative dentistry (Table 6.4). It is often necessary to roughen the surface of metal restorations before bonding. Conditioners to increase the bond strength to metal restorations are known as metal primers (Metal Primer; Reliance Orthodontics, see Table 6.5). Bonding protocols for the various types of surfaces are described in Table 6.6.
Table 6.2
Bonding to enamel
Mechanical macroretention
Buccal technique:-Lingual technique: microetching
Mechanical microretention
Conditioning of enamel with 30%-40% phosphoric acid
Chemical bonding
Primer-i.e., unfilled monomer or microfilled monomer penetrates into the mechanical microretentions created by enamel etching
Bonding agent
Composite or compomer
Table 6.3
Bonding to existing composite fillings, composite veneers, or acrylic denture teeth
Mechanical macroretention
Roughening of the surface with a microetcher or with a tungsten carbide burr
Additional bond strength enhancer
Polymer conditioner
Chemical bonding
Primer-i.e., unfilled or microfilled monomer penetrates into the mechanical macro-retentions and dissolves the polymer chains of the surrounding acrylic
Bonding agent
Composite
Table 6.4
Bonding to ceramic
Mechanical macroretention
Roughening of the surface with microetcher or fine diamond burrs
Mechanical microretention
Conditioning of the ceramic with 15%-20% hydrofluoric acid
