Orthodontic elastics, commonly known as rubber bands, are a standard component of brace treatment used to correct complex bite misalignments that brackets and wires alone cannot address. These devices stretch between the upper and lower teeth to apply targeted force that guides the jaws and teeth into their correct relationship. A frequent question is whether wearing two elastics instead of one can accelerate the process. The answer involves understanding the delicate biological process of tooth movement, which is governed by precision, not simply maximum force.
The Function of Orthodontic Elastics
The movement of teeth is a biological phenomenon, relying on the remodeling of the bone that surrounds the tooth roots. Orthodontists prescribe elastics that deliver a specific, calibrated force to initiate this change. For effective and safe movement, the optimal force is light, often falling between 50 and 100 centiNewtons (about 5 to 10 grams of force per tooth).
This controlled, continuous pressure is transmitted through the tooth root to the periodontal ligament (PDL), a thin layer of tissue that anchors the tooth to the jawbone. Pressure on one side of the PDL stimulates specialized cells called osteoclasts to break down the surrounding bone. Tension on the opposite side signals osteoblasts to build new bone, allowing the tooth to move gradually. This cycle of bone resorption and deposition is inherently slow, and its efficiency is tied to the lightness and consistency of the applied force.
The Impact of Doubling the Force
Applying a second rubber band dramatically increases the force, often doubling or tripling the pressure far beyond the safe therapeutic range. Excessive force causes severe compression of the periodontal ligament. This extreme pressure physically collapses the microscopic blood vessels that run through the PDL, leading to ischemia, where blood flow is severely restricted.
The lack of blood flow results in tissue death, creating a cell-free area within the ligament known as hyalinization. This necrotic tissue acts as a hard barrier, completely halting the desired frontal bone resorption. Movement cannot resume until the body initiates a slower, less efficient process called undermining resorption, where cells attack the dead tissue from the bone marrow spaces below. Paradoxically, doubling the force does not speed up the process; instead, it creates a biological roadblock that significantly delays treatment.
Biological Risks of Excessive Strain
The application of excessive mechanical strain poses several severe and potentially irreversible risks to the dental structures. One significant consequence is external apical root resorption (EARR), which is the permanent shortening or blunting of the tooth roots. While microscopic resorption is common in orthodontic treatment, excessive force significantly increases the risk and severity of this irreversible loss of root structure.
Another serious risk is the loss of anchorage, involving the unintended movement of the anchor teeth. Elastics are designed to move specific teeth using other teeth as stable anchors. If the force from doubling the bands exceeds the capacity of the anchor teeth to resist movement, those teeth will shift in an unwanted direction, complicating the bite and requiring extensive correction. Furthermore, the tissue necrosis caused by the pressure can lead to localized inflammation and discomfort, potentially damaging the surrounding gum and bone tissue.
Why Consistency Trumps Increased Force
The most effective strategy for successful orthodontic treatment is strict adherence to the orthodontist’s instructions regarding elastic wear. Tooth movement relies on continuous force, meaning the elastics must be worn for the prescribed duration, typically 20 to 22 hours per day. Removing the bands for long periods allows the periodontal ligament to recover, and the teeth can shift back toward their original positions, undoing the progress made.
Consistent compliance with the single, prescribed elastic maintains the light, continuous pressure necessary to keep the bone remodeling cycle active without causing tissue necrosis. Patients should replace their elastics frequently, as instructed, because the material degrades and loses elasticity over the course of a day. If a patient feels their treatment is progressing too slowly, they should consult the orthodontist. The orthodontist can safely adjust the force or treatment plan, rather than attempting self-correction with extra bands.