Interproximal Reduction (IPR) is a controlled dental procedure that removes a minute amount of the outermost enamel layer from the sides of teeth. This technique is frequently used in modern orthodontic treatment, particularly with clear aligner therapy, to create necessary space for tooth movement. It is sometimes referred to as teeth “slenderizing,” “stripping,” or “enamel reduction.” The goal is mechanical: allowing crowded teeth to align properly without more invasive measures.
Why IPR is Used in Orthodontics
The primary indication for IPR is to gain a small amount of space within the dental arch when only minor to moderate crowding exists. Creating this space allows the teeth to move into their desired, uncrowded positions as guided by braces or clear aligners. This measured approach is a preferred alternative to extracting a permanent tooth when the space requirement is minimal.
Orthodontists precisely calculate the amount of space needed, which is typically less than 0.5 millimeters from each treated tooth surface. This conservative removal is often enough to resolve crowding that measures between 4 and 8 millimeters across the arch, allowing the entire dentition to be preserved while achieving a straight, stable result.
Another significant application is correcting a tooth size discrepancy, or Bolton Discrepancy. This occurs when the width of the upper teeth is disproportionate to the lower teeth, preventing the jaws from fitting together ideally. By subtly reducing the width of specific teeth, IPR helps establish a balanced, functional bite, improving overall occlusion.
The technique is also employed to enhance the final aesthetic outcome by reshaping contact points. When teeth are severely overlapped before treatment, alignment can sometimes leave small triangular gaps near the gumline called “black triangles.” Reshaping the sides of the teeth with IPR helps close these spaces, creating broader, more natural-looking contact between adjacent teeth.
The IPR Procedure: Tools and Technique
The IPR procedure begins with an assessment to identify the exact teeth that require reduction and the precise amount of enamel to be removed. The space created is carefully monitored using thin, calibrated metal gauges, confirming the space achieved matches the treatment plan. Because enamel does not contain nerve endings, the procedure generally involves no pain, though patients may feel pressure or vibration.
For the most minimal reductions, often 0.1 millimeters, the orthodontist may use manual abrasive strips. These thin, file-like strips are gently worked back and forth between the teeth, offering excellent control for a conservative result. This manual method is especially useful for breaking the initial contact between crowded teeth.
For larger reductions, up to the maximum safe limit per surface, powered instruments are often employed. These include slow-speed handpieces fitted with fine diamond-coated discs or specialized burs. The clinician must use a gentle, controlled back-and-forth motion, ensuring the tool remains parallel to the tooth’s long axis to prevent uneven surfaces. Throughout the process, surrounding soft tissues are protected with specialized guards to ensure patient safety.
Enamel Health and Post-Procedure Care
A common concern is whether removing enamel compromises the long-term health or strength of the teeth. IPR is considered safe when performed within established clinical guidelines, as it targets only a small portion of the thick, highly mineralized outer layer. The maximum recommended removal is typically less than 50% of the natural enamel thickness in the treated area.
Studies consistently show that IPR, when executed correctly, does not increase the risk of tooth decay (caries) or cause long-term tooth sensitivity. The enamel naturally contains a high mineral content, and the slight reduction is comparable to the natural wear that occurs over a lifetime. The most significant factor in maintaining tooth health post-procedure is the final step of polishing.
After the reduction is complete, the treated surfaces are carefully polished and smoothed to minimize microscopic roughness that could trap plaque. Following this, a topical fluoride varnish or a substance containing Casein Phosphopeptide-Amorphous Calcium Phosphate (CPP-ACP) is often applied. This application aids in surface remineralization, further strengthening the enamel. Patients are advised to maintain excellent oral hygiene, including diligent brushing and flossing, to ensure the long-term health of the treated teeth.