A dental retainer is a custom-made appliance worn after orthodontic treatment, designed to maintain the alignment of teeth. Many people wonder if the retainer they already have can close a space between teeth, known as a diastema. There is a frequent misunderstanding that a standard retainer is a passive device and cannot initiate major tooth correction. The primary function of a retainer is fundamentally different from active movement tools, and understanding this distinction is key to knowing which appliance is appropriate for closing gaps.
The Primary Role of Dental Retainers
Standard dental retainers are designed for stability and maintenance, serving as the final step after orthodontic work is completed. Their main purpose is “retention,” which means holding the teeth securely in their newly corrected positions to prevent them from shifting back toward their original alignment, a phenomenon called relapse. Teeth are constantly under various pressures from chewing, swallowing, and the natural elasticity of the periodontal ligaments, all of which encourage movement.
Retainers counteract these forces by acting as a passive barrier. A fixed retainer is a thin wire permanently bonded to the back of the front teeth, providing continuous support. Removable options, such as clear plastic aligner-style retainers (Essix) or the traditional Hawley retainer, are molded to the exact shape of the teeth post-treatment. Because these appliances fit the current dental configuration precisely, they do not exert the sustained, directional force necessary to physically move a tooth through the bone.
Active Devices Designed for Significant Gap Closure
Closing a significant gap requires active orthodontic treatment, which uses continuous, precise pressure to remodel the bone around the tooth roots. Devices like traditional metal or ceramic braces achieve gap closure by bonding brackets to the teeth and connecting them with a flexible archwire.
The archwire is tightened or adjusted to apply a gentle, sustained force that signals the body to break down bone tissue (resorption) and build new bone tissue (deposition). This controlled bone remodeling allows the entire tooth, including the root, to move into a new position, which is necessary for closing larger gaps effectively. Clear aligner systems, such as those made from a series of transparent, removable trays, operate on a similar principle of sustained pressure. Each aligner tray is fabricated to be slightly different from the current tooth position, guiding the teeth incrementally over time to close the space.
When a Retainer Might Influence Tooth Position
While standard retainers are passive, some appliances that look like retainers can be customized for minor active movement. If a small space, often less than two millimeters, reopens after previous orthodontic treatment (minor relapse), a modified retainer may be used to gently correct it. This is typically considered limited tooth movement, not comprehensive orthodontic treatment.
A Hawley retainer, for instance, can be manufactured with active components like adjusted wires or small finger springs built into the acrylic base. The orthodontist can periodically adjust the wire loop that sits across the front teeth, known as the labial bow, to exert a slight force that encourages the minor gap to close. This action primarily achieves “tipping” movement of the crown rather than the full root movement accomplished by braces. In contrast, an old or ill-fitting retainer that no longer matches the current tooth shape can sometimes cause unwanted minor shifting.