For information regarding engagers that fall off, refer to the following:

• Definition
• Causes
• Solutions

Definition

Engagers can sometimes fall off after you put them on. The reason why composite falls off is usually a failure of the etching and bonding agent. 

Causes

The most common cause for why an engager might fall off when removing the aligner, is that the composite has not fully adhered 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 ideally the engager may stay on at first but eventually it fails.

Some possible causes for an engager falling off are:

• Plaque might be preventing 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
• Too much primer is being used
• There is an excess of moisture or saliva
• Poor curing light

The cause for engagers failing may also be a combination of conditions, here's an example:

Forgetting to pumice the teeth, a small amount of moisture is included by failing to maintain a dry field, and too thick a layer of bonding agent. 

Solutions

Try the following actions:

• When plaque prevents the etch from working, using a pumice should remove the plaque sufficiently.

• If the tooth is a restoration, use a special etch for porcelain from your dental supplier. (Note: This does not always work.) This article on bonding systems 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 a common problem with compressed air and is hard to correct in the system.  Be 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.

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