Orthodontic elastics, often simply called rubber bands, are a common element of treatment for people wearing braces or clear aligners. While the brackets and wires or the aligners are responsible for straightening individual teeth, the elastics serve a different, more complex purpose. They apply force between the upper and lower jaws, guiding them into a harmonious relationship. Many patients are instructed to wear these bands on both sides of the mouth, but receiving instructions to wear them only on one side often causes confusion. This asymmetrical prescription is a highly precise and necessary component of a personalized treatment plan.
The Primary Role of Orthodontic Elastics
Orthodontic elastics are categorized as intermaxillary appliances because they stretch between the upper (maxillary) and lower (mandibular) arches to correct the bite, or the way the teeth meet together. They provide the necessary force to move entire groups of teeth and adjust the jaw relationship, a movement that braces or aligners alone cannot efficiently achieve. Elastics are frequently used to address sagittal discrepancies, which are issues with the front-to-back alignment of the jaws.
A common application is the correction of a Class II malocclusion, often referred to as an overbite, where the upper jaw is positioned too far forward relative to the lower jaw. In this bilateral scenario, elastics run from the upper front teeth to the lower back teeth to pull the upper arch back and the lower arch forward. Conversely, a Class III malocclusion, or underbite, requires elastics that run from the lower front teeth to the upper back teeth to correct the opposite jaw position. These symmetrical uses demonstrate the general principle of elastics: applying consistent force over time to achieve a balanced bite.
Understanding Unilateral Bite Corrections
The instruction to wear an elastic only on one side directly indicates that the bite problem is asymmetrical, meaning the issue exists on one side of the mouth but not the other. Your orthodontist is targeting a specific imbalance that requires a unilateral correction. Applying force symmetrically when the problem is asymmetrical would create a new imbalance, as the mouth is not always a mirror image.
Midline Discrepancies
One frequent reason for unilateral wear is a midline discrepancy, where the center line of the upper teeth does not align with the center line of the lower teeth or the center of the face. An elastic worn on one side can gently pull the entire arch sideways to shift the jaw into proper alignment.
Unilateral Malocclusions
Similarly, a patient might present with a unilateral Class II or Class III malocclusion, where the bite is correct and stable on one side, but the jaw relationship is incorrect on the opposing side. In these cases, the elastic is applied only to the side with the misalignment to avoid disturbing the already-corrected side.
Crossbites and Occlusal Plane Correction
Another specific asymmetrical issue is a unilateral crossbite, where the upper teeth on one side bite inside or outside the lower teeth. Cross elastics, often placed diagonally across the arches, can move a single section of teeth into the correct position without affecting the other side. Unilateral elastics may also be prescribed to correct the occlusal plane, which is the imaginary line formed by the biting surfaces of the teeth. If this plane is tilted, applying a vertical elastic on the side that needs lifting or lowering can help level the bite, preventing unwanted side effects on the opposite side.
The Importance of Following Asymmetrical Instructions
The success of a unilateral elastic prescription relies heavily on strict patient compliance, as the force is precisely calculated to fix a specific imbalance. Failing to wear the elastics for the prescribed 20 to 24 hours per day will significantly slow down the treatment timeline, as teeth may relapse or stop moving entirely. The continuous force is necessary to ensure the bones and ligaments surrounding the teeth remodel correctly. Consistent wear also means replacing the elastics often, as they degrade and lose their force within a day.
It is equally important not to over-comply by wearing the elastic on the opposite side without instruction, or by doubling up the bands. Because the prescription is designed to address an existing asymmetry, applying force to the side that is already correct will introduce a new, unintended bite problem. This action can cause an undesirable overcorrection, which prolongs the overall treatment by requiring the orthodontist to correct the new issue. The instructions are a tailored biomechanical formula, and any deviation from the asymmetrical plan risks compromising the intended outcome.