The Enamel Surface and Bonding in Orthodontics

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Current research on the enamel surface after different bonding and debonding procedures is discussed in this review. Preconditioning the enamel surface with a 37% orthophosphoric acid solution or gel for approximately 30 seconds dissolves the minerals and thus induces irreversible changes to the enamel. The cumulative enamel loss of pumicing, bonding, debonding, and clean ups is difficult to estimate precisely as minerals are not dissolved in a uniform way. Residual adhesive may persist in surface enamel after debonding. Resin tags can reach more than 20 μm into the enamel after bonding based on the acid-etching principle, and alteration of the prism structure even further. Little research is available on the long-term effect of residual adhesive material in surface enamel. Bonding systems using self-etching primers in combination with composite adhesives or resin-modified glass ionomer bonding systems provide bond strengths sufficient for clinical use in orthodontics. These bonding systems induce less adverse effects to the enamel surface, and hence the clean up process is easier for the orthodontist. The risk of leaving residual bonding material in surface enamel is thus less.

Section snippets

The Sound Enamel Surface

Enamel is characterized by a high mineral content (96 wt%) and by a low content of organic matter (0.4-0.8 wt%) and water (3.2-3.6 wt%). The mineral phase is generally described as calcium hydroxyapatite, which belongs to an isomorphous series of compounds known as apatites. The tightly packed, hexagonal, needle-shaped crystallites of the hydroxyapatite are the real units of enamel and are arranged into prisms. The appearance of the “keyhole” shaped prisms radiating from the dentinoenamel

Cleaning

Pumicing the enamel surface before conditioning has generally been considered a prerequisite for obtaining optimal bond strength. The rationale behind pumicing is that organic material like plaque and the acquired pellicle may inhibit optimal etching. Rotary instruments like rubber cups or polishing brushes are used. Typically, the pumicing process results in enamel loss of 5-14 μm, depending on the time and type of instruments used to clean the surface.12 Recently, Hosein et al13 using a

The Enamel Surface After Debonding

Debonding orthodontic attachments and removal of residual bonding material from the enamel surface include critical steps in the overall orthodontic management.5 Usually metal brackets can be debonded relatively easily by applying forces that peels the bracket base away from the tooth. Most often, such forces cause bond failure at the adhesive-bracket interface and most of the adhesive remain on the enamel surface after debonding.

The debonding and removal of ceramic brackets have in particular

Conclusion

The cumulative enamel loss of pumicing, bonding, debonding, and clean ups may appear relatively low compared with the thickness of the enamel surface (1500-2000 μm). More important is, however, whether residual adhesive persists in surface enamel after debonding. Resin tags can reach more than 20 μm into the enamel after bonding based on the acid-etching principle, and alteration of the prism structure even further. Using tungsten carbide burs in slow-speed handpiece or using debonding pliers

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