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Retainer (orthodontics)

life science Maturity 11-13 Next article →

Orthodontic retainers are custom-made medical devices designed to maintain tooth position. After orthodontic surgery or realignment, teeth face a lifelong risk of relapse. Relapse is the tendency for teeth to return to their original, unstraightened positions. This movement occurs due to several biological factors. These include the recoil of periodontal fibres and pressure from surrounding soft tissues. Additionally, occlusion, which is how teeth meet, and a patient's ongoing growth and development can cause shifts.

Retainer
Retainer

By wearing a retainer, the surrounding periodontal fibres can adapt to changes in the bone. This process helps minimize changes to the final tooth position after treatment ends.

Removable retainers are devices that a patient can take in and out of the mouth. These may be worn part-time or full-time depending on an orthodontist's advice. One of the most famous types is the Hawley retainer. Named after its inventor, Dr. Charles A. Hawley, it consists of metal wires that typically surround the six anterior teeth. These wires, called a labial bow, are anchored into an acrylic baseplate that sits against the palate, or the roof of the mouth.

retainerBottom
retainerBottom

The Hawley retainer is robust and rigid. It allows for adjustments to continue minor tooth movements or to fix specific rotations. For example, an acrylic facing can be added to the labial bow to correct rotations. However, Hawley retainers can interfere with speech sounds like "d," "s," "t," and "i." They may also be less aesthetic than newer options.

A more modern removable option is the vacuum-formed retainer, or VFR. These are made from clear materials such as polypropylene or polyvinylchloride (PVC). They are created through a thermoforming process, which uses vacuum or pressure to shape the material.

Retainers
Retainers

VFRs are often nearly invisible when worn, providing an aesthetic advantage. Some designs fit the entire arch, while others are "clip-on" styles that only cover the teeth from canine to canine. Because VFRs cover the occlusal, or biting, surfaces, they may prevent the upper and lower teeth from touching if worn 24 hours a day. Some orthodontists suggest wearing them intermittently to allow for "favourable settling" of the teeth.

While VFRs are economical and easy to make, they have specific limitations. If worn while eating, they can act as a reservoir for cariogenic substances, which are substances that cause cavities. This can lead to decalcification of the teeth. Furthermore, patients with bruxism, or teeth grinding, may cause VFRs to break rapidly. Despite these risks, VFRs offer superior retention of lower incisors compared to many other removable types. Other specialized removable retainers include Begg retainers and Barrer retainers. Begg retainers have a labial bow that extends around the distal aspect of the terminal molar. Barrer retainers, also known as spring retainers, carry acrylic bows both labially and lingually.

Fixed retainers represent a different approach to orthodontic retention. Unlike removable versions, these stay in the mouth permanently. They typically consist of a wire bonded to the lingual or palatal surface of the anterior teeth. This bonding is achieved using acid etch and a material called composite.

Sarro
Sarro

Composite is used to bond and cover the wire while ensuring there is no interference in the interdental space between teeth. Fixed retainers are often used when instability is likely, such as in cases of severe rotations or median diastemas. They can be made with a smooth wire or a flexible multi-strand spiral wire. While they do not require the patient to remember to wear them, they are more difficult to clean. Patients must be diligent to prevent plaque accumulation and gingival inflammation.

Proper maintenance is essential to prevent dental issues. If retainers are not cleaned, they can trap food and lead to caries, or cavities. Removable retainers can be cleaned with a toothbrush, fragrance-free soap, or non-abrasive toothpaste. It is important to avoid very hot water, as this can cause the material to shrink. When not in use, retainers should be kept in a dry container and away from high temperatures. For fixed retainers, cleaning must be integrated into the nighttime oral hygiene routine. These habits ensure the appliance stays intact and the gums remain healthy.

Recent technological innovations are changing how patients manage their retention. Some practitioners worry that younger patients may not comply with wearing removable retainers. To address this, SMART Retainers and related mobile applications have been developed. These systems use the Internet of Things (IoT) and motion sensors to track and remind patients to use their devices. The mobile apps can even reward patients for consistent use. Some applications include a feature for parental notifications. If a child does not open their Smart Retainer Case, the parent receives a notification. This technology aims to decrease the number of adolescents needing additional orthodontic treatment due to non-compliance.

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