Orthodontic bonding is the process of securely attaching small metal or ceramic brackets to the surface of the teeth, forming the anchor points for the braces system. This procedure relies on a sophisticated adhesive system to create a durable, non-permanent connection to the tooth enamel. A successful bond ensures the bracket remains fixed throughout treatment, allowing the archwire to transmit the necessary forces to move the teeth into alignment. If the bond fails, force transmission stops, which interrupts and delays the overall treatment timeline.
The Clinical Steps of Bracket Bonding
The bonding procedure begins with meticulous preparation of the tooth surface to ensure maximum adhesion. First, the teeth are thoroughly cleaned and polished using a fluoride-free pumice paste to remove any plaque, debris, or the acquired pellicle layer that naturally forms on the enamel.
After cleaning, a dry field is established using cheek retractors and cotton rolls to prevent contamination from saliva, which can severely compromise the bond strength. The orthodontist then applies a conditioning agent, typically a gel containing 37% orthophosphoric acid, to the enamel surface for a specific duration, usually between 15 and 60 seconds. This acid etching process microscopically roughens the enamel, dissolving tiny portions of the hydroxyapatite crystals to create thousands of minuscule pores and undercuts.
The acid is then thoroughly rinsed away with water and the tooth is completely dried with oil-free compressed air. The etched enamel appears visibly frosty or chalky white, confirming the micro-retentive surface necessary for mechanical interlocking has been created. Next, a thin layer of liquid primer is applied to the etched enamel, which flows into these microscopic pores and prepares the surface for the main adhesive.
The bracket itself, which has a base designed with a fine mesh or mechanical retention features, is then coated with the composite resin adhesive. The bracket is carefully positioned on the tooth, and any excess adhesive, known as “flash,” is removed before curing. Finally, a high-intensity light is directed at the bracket and surrounding adhesive for a set time, often 10 to 15 seconds per bracket, which activates the photo-initiators in the resin to rapidly harden and finalize the bond.
The Adhesion System Components
The strong attachment between the bracket and the tooth is achieved through a multi-component chemical system. The initial conditioning of the enamel is primarily performed by a solution of 37% orthophosphoric acid. This etchant creates a porous topography on the enamel surface, which is the foundation for micromechanical retention.
Following the etch, a primer, which is a low-viscosity, hydrophilic resin material, is applied to penetrate the newly created enamel porosities. This primer acts as a wetting agent, ensuring the subsequent adhesive layer can intimately contact the prepared tooth surface. The final component is the adhesive material, a composite resin that is viscous and paste-like.
This composite resin flows into the primer-coated enamel surface and around the mechanical retention features, such as the wire mesh pad, on the back of the bracket. When exposed to the curing light, the resin undergoes polymerization, hardening to form a rigid connection that locks the bracket to the tooth. The combination of the etched enamel, the liquid primer, and the composite adhesive creates a robust interface capable of withstanding the forces of chewing and orthodontic movement.
Protecting the Bond
Once the brackets are bonded, the patient plays a significant role in maintaining the integrity of the adhesive interface. The bond is vulnerable to excessive, sharp, or sticky forces. Adhering to specific dietary restrictions is necessary to prevent premature bond failure (when a bracket detaches from the tooth surface).
Patients must strictly avoid consuming extremely hard foods (ice, nuts, hard candies) and sticky items (caramels, toffees), which exert a direct pulling force on the bracket. Crunchy foods, including popcorn, chips, and raw carrots, should also be avoided or cut into small pieces. These foods create high-stress forces that can overwhelm the adhesive or deform the bracket base, leading to detachment.
Certain habits must also be stopped, including chewing on foreign objects like pen caps, pencils, or fingernails, which apply concentrated, disruptive forces to the brackets. Poor patient compliance often results in bond failure, which requires an unscheduled appointment to rebond the bracket. Each instance of failure interrupts the continuous force application required for effective tooth movement, potentially extending the overall treatment duration.
Proper oral hygiene is also a protective measure for the bond, as it prevents the buildup of plaque and subsequent enamel demineralization around the bracket edges. Brushing three to five times a day, using interdental brushes, and flossing with a threader are essential to keep the enamel healthy and the bond site clean.