Interproximal reduction (IPR) is a minor dental procedure used frequently in orthodontic treatment, particularly with clear aligner therapy. This technique involves carefully removing a very small amount of the outer tooth surface, known as enamel, from the sides of specific teeth. The main objective of IPR is to create minute amounts of space within the dental arch, allowing teeth to move into a better position. It is a common, conservative approach to managing minor tooth alignment issues without the need for more invasive methods.
Defining Interproximal Reduction
The concept of IPR is built upon the need for space to resolve minor crowding and refine the fit between the upper and lower teeth. When teeth are slightly overlapped or crowded, IPR provides a controlled method to generate the small amount of arch space required for successful alignment. This procedure is an alternative to extracting a permanent tooth, which is typically reserved for cases involving more severe crowding.
IPR is also applied to address tooth size discrepancies, such as a Bolton discrepancy, where the width ratio between the upper and lower teeth is unbalanced. By selectively reducing the size of certain teeth, the orthodontist can achieve a more stable and harmonizing bite. Reshaping the sides of teeth can also improve the contact points, which may reduce the appearance of “black triangles”—small, dark spaces that can form near the gumline after teeth are straightened.
The amount of enamel removed is minimal and highly controlled, usually ranging from 0.2 to 0.5 millimeters from a single contact point. Since the enamel layer is substantially thicker, this small reduction maintains the structural integrity of the tooth. When performed across several teeth, these small reductions accumulate to provide the total space needed for tooth movement.
The Clinical Procedure
The execution of IPR is a precise and carefully managed process that patients can expect to be quick and generally painless. Because enamel does not contain nerves, no anesthetic is typically required. The orthodontist first identifies the specific teeth that require reduction and the exact amount of space that needs to be created at each contact point, based on the treatment plan.
The reduction can be performed using either manual or mechanized tools, depending on the amount of enamel to be removed and the orthodontist’s preference. Manual reduction involves abrasive strips, which resemble fine sandpaper or a thin file, moved gently between the teeth. Mechanized reduction utilizes a specialized dental handpiece fitted with diamond-coated discs or fine burs.
Mechanized tools allow for a faster and more uniform reduction. To protect the gums and surrounding soft tissues, a thin metal strip or guard is often placed between the tooth being worked on and the gumline. Once the enamel has been reduced, the orthodontist uses small measuring gauges to confirm that the exact amount of space has been created.
The final step is smoothing and polishing the treated enamel surface immediately after the reduction is complete. This restores the tooth’s natural contour and prevents the accumulation of plaque. The entire process for a few contact points typically takes only a few minutes during a routine orthodontic appointment.
Addressing Common Patient Concerns
One frequent concern is whether removing enamel increases the risk of tooth decay. When the procedure is performed correctly, the risk of developing cavities does not increase compared to untreated teeth. The remaining enamel is sufficiently thick to protect the inner layers of the tooth.
To further protect the treated surface, the orthodontist frequently applies a topical fluoride varnish immediately following the polishing step. This helps the enamel remineralize and strengthen the surface. The long-term health and strength of the teeth are not compromised by this minimal surface area removal.
Another common question relates to patient comfort. Because the outer layer of enamel lacks nerve endings, the procedure itself is not painful, though patients may feel pressure or vibration. Some patients report a temporary, minor increase in sensitivity to hot or cold temperatures immediately following the IPR.
This short-term sensitivity typically resolves naturally within a few days to a week as the tooth adjusts to the new contour. IPR is a conservative and controlled method of tooth size modification. When used appropriately, this long-established procedure contributes to a stable and aesthetically pleasing final alignment.