Bracket bonding succeeds on enamel with isolation, etching, priming and a correctly placed bracket. Restorations need different preparation: metal and zirconia usually need air abrasion with a suitable primer, while glass ceramics such as lithium disilicate and porcelain need hydrofluoric acid etching and a silane. Follow the adhesive manufacturer's instructions for each product.
Where to place the bracket
Place the bracket at the centre of the clinical crown, aligned with the long axis of the tooth, at the height recommended for your prescription. Consistent heights across the arch matter because each bracket expresses its built-in values only when it sits where the prescription expects it to sit. Use a bracket height gauge or a consistent measuring method until the eye is trained.
Bonding on healthy enamel
- Clean the tooth with a fluoride free prophylaxis paste and rinse.
- Isolate with cheek retractors and control saliva. Moisture contamination is the most common cause of failure.
- Etch with phosphoric acid (commonly 37 percent) for the time the manufacturer specifies, then rinse.
- Dry until the enamel shows a frosted appearance.
- Apply primer, place adhesive on the bracket, seat it, remove the excess and light cure.
Less than ideal tooth surfaces
Fluorosis and hypomineralised enamel, short or partially erupted crowns, and teeth with large restorations all bond less predictably. Roughen composite restorations before bonding, use a band where isolation cannot be achieved or where the crown is too short, and consider an adhesive that tolerates moisture on partially erupted teeth.
Bonding on different materials
| Surface | Usual preparation |
|---|---|
| Metal crown or amalgam | Air abrasion with alumina, then a metal primer |
| PFM, porcelain exposed | Hydrofluoric acid etch for a short time or air abrasion, then silane |
| Zirconia | Air abrasion, then a primer containing MDP (hydrofluoric acid does not etch zirconia) |
| Lithium disilicate (e.max) | Hydrofluoric acid etch (commonly 5 percent, time per manufacturer), then silane |
Hydrofluoric acid is hazardous. Protect the soft tissues and adjacent teeth and follow the product's safety instructions. Debonding a bracket from a ceramic surface can chip or fracture the restoration, so discuss this with the patient before bonding and plan the removal carefully.
Key takeaways
- Accurate bracket position decides how well the prescription is expressed.
- Moisture control is the most important step in bonding to enamel.
- Each restorative material needs its own surface treatment, so follow the manufacturer's instructions.
Frequently asked questions
Can brackets be bonded to zirconia crowns?
Yes, with air abrasion and a primer containing MDP, because hydrofluoric acid does not etch zirconia. Bond strength can be lower than on enamel, so tell the patient and plan debonding with care.
Why do brackets keep debonding?
The most frequent cause is moisture contamination during bonding. Other causes are poor etching, premature occlusal contact on the bracket and hard food or habits.