Passive Removable Appliances: Breaking Habits and Maintaining Results

Not every removable orthodontic appliance is designed to move teeth. Some play a different but equally important role: helping patients break harmful oral habits and maintaining the results achieved after orthodontic treatment. From habit-breaking appliances to different types of retainers, passive removable appliances are designed to control unwanted forces and support long-term treatment stability.

Habit Breakers

Habit breakers, such as tongue guards and palatal cribs, are used in cases of thumb-sucking or tongue-thrust habits (Profitt, 2018). The active components of these appliances are loops on the labial bow, which interfere with the patient's habit (Gawlik et al., 1995). Adam’s clasps or Southend clasps are sometimes incorporated into the design for retention (Profitt, 2018).

The crib or loops must be in line with the maxillary incisor tips to prevent interference with the lower incisors during maximum intercuspation (Abraham et al., 2013).

Oral Screen

An oral screen is a simple passive myofunctional appliance that eliminates abnormal forces from the lips and perioral musculature on the dentoalveolar structures and allows the forces of the tongue to expand the lower arch (Arora et al., 2013).

It is effective in treating acquired malocclusions resulting from abnormal habits such as lip sucking, thumb sucking, and mouth breathing (Arora et al., 2013).

Retention

Following orthodontic treatment, retainers are used to help maintain the corrected tooth position and prevent relapse. Several types of passive removable retainers can be used depending on the patient's needs.

Hawley Retainer

The Hawley retainer is an appliance that extends from canine to canine, with an anterior bow and clasps on the molars (Profitt, 2018). The adjustment loop of the Hawley anterior bow often prevents the wire from having full contact with the canines (Profitt, 2018).

Adam’s clasp or a C clasp can be incorporated for retention, and bite planes may sometimes be added to maintain overbite reduction (Rowlands et al., 2007). The labial bow can also be activated to close residual spaces (Rowlands et al., 2007).

Barrer Retainer

The Barrer retainer is “an appliance that is designed for minor adjustment of rotated incisors” (Sandler & Reed, 1988). It usually consists of acrylate bows both labially and lingually and is used in the mandible (Rowlands et al., 2007).

A Barrer retainer in the mandible was shown to be more effective than a wire Hawley bow in retaining contact between the lower incisors (Sandler & Reed, 1988).

Glass-Reinforced Clear Polymer Retainer

This is a removable maxillary retainer with a clear outer bow. It fits more tightly than a metal wire and provides a more aesthetic appearance (Profitt, 2018).

However, it cannot be adjusted to modify tooth positions without creating a new retainer (Profitt, 2018).

Vacuum Essix Retainer

A Vacuum Essix retainer is made from a clear thermoplastic plate created using vacuum pressure on the patient’s cast and fitted tightly over the patient's teeth (Jäderberg et al., 2012).

Because the material is thin and transparent, many patients prefer this type of retainer, resulting in better reported compliance (Jäderberg et al., 2012).

References

• Gawlik, J.A., Ott, N.W. and Mathieu, G.P., 1995. Modifications of the palatal crib habit-breaker appliance to prevent palatal soft tissue embedment. *ASDC Journal of Dentistry for Children*, 62, pp.409–411.

• Jäderberg, S., Feldmann, I. and Engström, C., 2012. Removable thermoplastic appliances as orthodontic retainers—a prospective study of different wear regimens. *The European Journal of Orthodontics*, 34(4), pp.475–479.

• Sandler, P.J. and Reed, R.T., 1988. Removable retainers: a modification of the Barrer appliance. *British Journal of Orthodontics*, 15(2), pp.127–129.