Orthodontic elastics, commonly known as rubber bands, are small, stretchy accessories that play a significant role in orthodontic treatment. These bands are distinct from the tiny ligatures that secure the main wire to the bracket, or the continuous power chains used to close spaces between teeth on a single arch. The purpose of these inter-arch elastics is to apply force between the upper and lower jaws, not just to straighten individual teeth. They focus on correcting the relationship of the upper and lower arches when the mouth is closed, known as the bite. Braces alone primarily align teeth within a single arch, leaving the correction of jaw position to these removable elastics.
The Mechanics of Force Application
Orthodontic elastics work by providing a dynamic, directional pull that fixed braces cannot replicate. While brackets and wires apply stationary force to move teeth along the archwire, elastics introduce an inter-arch force spanning from the upper jaw to the lower jaw. This specialized force application guides the entire dental arch, or even the jaw structure, into a new position.
The orthodontist selects a specific size and strength of elastic (light, medium, or heavy) to deliver a precise amount of mechanical energy. The continuous force triggers biological responses in the periodontal ligament, allowing the teeth and bone to shift. Stretching the band between two points creates a vector force, which dictates the direction of movement. This directional pull gradually moves sections of teeth, or the entire jaw, to establish the correct bite relationship.
Correcting Major Bite Discrepancies
The most frequent reason for using elastics is to address malocclusions between the upper and lower teeth. These bands are customized to resolve various bite issues that braces alone cannot solve. The configuration and placement of the elastics determine the type of correction being performed.
A common application is correcting a Class II relationship, often called an overbite or overjet. Elastics typically run from a bracket near the back of the upper arch to a bracket near the front of the lower arch. This force vector pulls the upper teeth backward and the lower teeth forward, reducing the horizontal overlap. This helps the upper and lower teeth meet in a more ideal relationship.
The opposite problem, a Class III relationship or underbite, requires a reverse placement. The bands are stretched from a front bracket on the upper arch to a back bracket on the lower arch. This configuration applies force to move the upper teeth forward and the lower teeth back, correcting the reverse overlap. For both Class II and Class III corrections, elastics are commonly prescribed in medium or heavy force, often sized between 1/4-inch to 3/8-inch.
Other Bite Corrections
Elastics are also used in triangular or box configurations to correct vertical issues, such as an open bite where the front teeth do not touch when the jaw is closed. Cross-elastics can be utilized to align the center point of the upper and lower arches, known as the midline. For midline correction, a medium force elastic, often 3/16-inch in size, shifts the upper teeth laterally until they align with the lower teeth.
Patient Compliance and Treatment Outcomes
The success of bite correction with elastics depends on the patient’s commitment to wearing them as instructed. Since the bands are removable, the responsibility shifts from the orthodontist’s fixed appliance to the patient’s daily routine. Orthodontists typically instruct patients to wear the elastics for a majority of the day, often aiming for 22 to 24 hours daily, removing them only for eating and hygiene.
Inconsistent wear significantly delays the treatment timeline and compromises the final result. If elastics are not worn for the prescribed hours, the continuous force needed for biological tooth movement is lost, and teeth may drift back toward their original positions. This lack of adherence means the desired bite relationship may not be achieved, potentially leading to treatment failure.