Engagers can sometimes fall off after you put them on. The reason why composite falls off of the porcelain is the etching and bonding agent.
The most common cause for why an engager might fall off when removing the aligner, is that the composite is not fully adhering to the tooth.
Bond failures are usually technique related and by doing each step well, the cumulative error in the chain of failure is reduced. When many of the steps are done less than ideal the engager may stay on at first but eventually it fails.
The cause for engagers failing may also be a combination of some of the following conditions, here's an example:
Forgetting to pumice the teeth, small amount of moisture by failing to maintain a dry field, and too thick a layer of bonding agent.
- Plaque might prevent the etch from working
- The tooth could be a restoration
- Lubricant from the engager template could have accidentally smeared on the tooth
- Compressed air that is used to dry the tooth is contaminated with oil or water
- Using too much primer
- Excess moisture or saliva
- Poor curing light
Try the following actions:
- When plaque prevents the etch from working, using a pumice will remove the plaque properly.
- If the tooth is a restoration, use a special etch for porcelain from your dental supplier. (Note: This does not always work.) Here is an article on bonding systems that may help you in choosing a bonding agent.
- If petroleum jelly from the template is accidentally smearing on the tooth, lift the template off of the tooth during insertion. Or, if possible, use the previous aligner to install the engager without using petroleum jelly. The composite won't adhere to used aligners as much as it will to new templates.
- Compressed air used to dry the tooth is contaminated with oil. This is the most common problem with compressed air and is hard to correct in the system. Make sure to service and maintain your compressors to ensure clean, dry air. Try drying the tooth with a low-heat blow dryer that can be bought at a dental suppler.
- Using too much primer will weaken the bond between the engager and the tooth. Primers are meant to work in thin layers. A blast of compressed air for 3-5 seconds can help thin out the layer of primer. Refer to the manufacturer's guidelines before attempting this for the first time.
- Intraoral retractors and saliva evacuation systems can help reduce excess moisture or saliva and will increase the integrity of your bonds.