retainer

This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (July 2008)

Bottom (at left) and top (at right) Hawley retainers

Vacuum form retainer in the foreground (used on upper); illustration of an early Hawley retainer in the background

Orthodontic retainers are custom-made devices, made usually of wires or clear plastic, that hold teeth in position after surgery or any method of realigning teeth. They are most often used before or after dental braces to hold teeth in position while assisting the adjustment of the surrounding gums to changes in the bone. Most patients are required to wear their retainer(s) every night at first, with many also being directed to wear them during the day - at least initially. They should not be worn while eating food or drinking staining or acidic beverages (e.g., Cola products and coffee). There are three types of retainers typically prescribed by orthodontists and dentists: Hawley, Essix, and Bonded (Fixed) retainers.

Hawley Retainer

The underneath surface of an upper Wrap Around Hawley retainer resting on top of a retainer case

The best-known type is the Hawley retainer, which is made of a metal wire that surrounds the teeth and keeps them in place. Named after Dr. Hawley, the labial wire, or Hawley bow, incorporates 2 omega loops for adjustment. It is anchored in an acrylic arch that sits in the palate or lingual walls of the mouth. The acrylic is Methyl Methacrylate which comes in two parts; the polymer (powder) and monomer (liquid). The Hawley retainer is designed for treatment after use of products that close diastemas (gaps). The advantage of this type of retainer is that the metal wires can be adjusted to finish treatment and continue moving teeth as needed.^[1]

Recently, a more esthetic version of the Hawley retainer has been developed. For this alternative, the front metal wire is replaced with a clear wire called the ASTICS. This retainer is intended to be adjustable in a similar manner to the traditional Hawley retainer, which is not practical with vacuum-formed retainers.

Vacuum-formed (Essix) Retainer

Another common type is the vacuum formed retainer (VFR). This is a polypropylene or polyvinylchloride (PVC) material, typically .020" or .030" thick. Essix is a brand name many dental offices are familiar with. This clear or transparent retainer fits over the entire arch of teeth or only from canine to canine (clip on retainer) and is produced from a mold. It is similar in appearance to Invisalign trays, though the latter are not considered "retainers". VFRs, if worn 24 hours per day, do not allow the upper and lower teeth to touch because plastic covers the chewing surfaces of the teeth. Some orthodontists feel that it is important for the top and bottom chewing surfaces to meet to allow for "favorable settling" to occur. VFRs are less expensive, less conspicuous, and easier to wear than Hawley retainers. However, for patients with disorders such as Bruxism, VFRs are prone to rapid breakage and deterioration, especially if the material is PVC, a short chain molecule. This breaks down swiftly as compared to polypropylene, a long chain molecule. Dr. Sheridan suggests only night wearing of these retainers except a variant of it with provisional bridge that is used only at daytime.

Most removable retainers are supplied with a retainer case for protection. During the first few days of retainer use, many people experience extra saliva in their mouth. This is natural and is due to the presence of a new object inside the mouth and consequent stimulation of the salivary glands. It may be difficult to speak for a while after getting a retainer, but this speech difficulty should go away over time as one gets used to wearing it.

Fixed Retainers

An entirely different category of orthodontic retainers are fixed retainers. A fixed retainer typically consists of a passive wire bonded to the tongue-side of the (usually, depending on the patient's bite, only lower) incisors. Unlike the previously-mentioned retainer types, fixed retainers can not be removed by the patient. Some doctors prescribe fixed retainers regularly, especially where active orthodontic treatments have effected great changes in the bite and there is a high risk for reversal of these changes. Fixed retainers may lead to tartar build-up or gingivitis due to the difficulty of flossing while wearing these retainers.

References