Interproximal Reduction (IPR), also known as slenderizing or stripping, is a routine orthodontic procedure. It involves the mechanical removal of a small amount of outer tooth enamel between adjacent teeth. This minimally invasive technique is a standard part of modern orthodontic treatment, especially with clear aligner therapy. The purpose of IPR is to create minute spaces within the dental arch, allowing teeth to move into their desired positions. It is a highly controlled process, performed with precision instruments to remove only fractions of a millimeter of the tooth’s hard, outer surface.
Why Orthodontists Use IPR
Orthodontists use IPR for several specific clinical indications, primarily when minimal space is required for successful tooth alignment. Its most common application is resolving mild to moderate dental crowding, typically ranging from four to eight millimeters of total space needed across the arch. By slightly reducing the width of multiple teeth, the procedure can often generate enough space to straighten crowded teeth without requiring the removal of whole teeth.
IPR is also a standard approach for correcting a Bolton Discrepancy, which is an uneven size ratio between the upper and lower teeth. Adjusting the width of specific teeth allows the upper and lower dental arches to fit together correctly, resulting in a stable and functional bite.
Furthermore, the technique is used to improve aesthetics by reshaping the contact area of teeth to minimize “black triangles.” These are small, dark spaces that can appear near the gum line after teeth have been aligned. Altering the tooth shape from triangular to more rectangular moves the contact point lower, helping gum tissue fill the space more naturally. Changing the tooth shape can also enhance the long-term stability and retention of the final orthodontic result.
How the IPR Procedure Works
The Interproximal Reduction procedure begins with the orthodontist carefully measuring and marking the contact points slated for reduction. This planning phase is often guided by digital treatment simulations, which specify the exact amount of enamel to be removed from each tooth surface. The total reduction typically ranges from 0.2 millimeters to a maximum of 0.5 millimeters per contact point, with the goal of removing only the minimal amount necessary.
During the procedure, the orthodontist uses specialized tools to perform the reduction. These instruments include manual abrasive strips, which resemble thin, flexible sanding files, and mechanical options like oscillating discs or rotary burs attached to a dental handpiece. The choice of tool depends on the amount of reduction required and the location of the tooth. Abrasive strips provide superior tactile control for very minor adjustments, while powered instruments are more efficient for larger, controlled reductions.
Patients generally report minimal discomfort during the process, often describing the sensation as feeling like a strong vibration or filing pressure. Since the outer layer of the tooth, the enamel, does not contain any nerves, the procedure rarely requires local anesthesia. The entire process is quick, often completed in a single appointment, or sometimes staged over several visits if the total reduction is extensive.
After the reduction is complete, the treated surfaces are meticulously smoothed and polished to prevent plaque buildup and ensure the tooth contour is natural and healthy. The orthodontist then uses thin metal gauges to confirm the precise amount of space that has been created.
Assessing Tooth Health and Safety
The primary concern about IPR often revolves around the long-term health of the tooth, but the procedure is considered safe and effective when performed within established limits. The average thickness of enamel on the sides of permanent teeth is substantial, typically ranging from 1.0 millimeters to 2.0 millimeters. Since IPR removes only a fraction of this thickness, usually between 0.1 and 0.25 millimeters from each surface, the remaining enamel is more than sufficient to maintain the tooth’s structural integrity.
Studies have demonstrated that proper IPR does not increase the long-term risk of dental decay or permanent tooth sensitivity. Any temporary sensitivity that may occur immediately following the procedure is typically mild and resolves on its own within a few days. The risk of pulp exposure, which is the internal nerve of the tooth, is negligible because the reduction is strictly superficial and confined to the enamel layer.
The safety of the procedure is dependent on the clinician’s precision and adherence to maximum removal guidelines. To minimize potential post-procedure issues, the stripped surfaces must be thoroughly polished to a smooth finish, eliminating any roughness that could attract plaque. Furthermore, a fluoride application is often provided immediately after IPR to aid in the remineralization of the newly adjusted enamel surface, offering added protection against decay.
Alternatives for Creating Dental Space
Interproximal Reduction is one of three main methods orthodontists use to create the space necessary for tooth movement, and it is usually the least invasive option.
The other two common methods are:
- Dental extraction: One or more teeth are completely removed to resolve severe crowding, typically when more than eight millimeters of space is needed per arch. This approach is reserved for complex cases where the arch length deficiency is too great to be managed conservatively.
- Arch expansion: This involves pushing the back teeth outward to widen the dental arch. This can be achieved through appliances like palatal expanders, which are primarily used in growing patients, or by simply moving the teeth outward with braces or aligners. Excessive outward movement can lead to thinning of the gum tissue and potentially gum recession.
IPR is specifically chosen when the space required is minimal, making it an excellent middle ground that avoids the permanence of extractions and the potential risks of over-expanding the dental arches. It is a targeted solution for fine-tuning the tooth-to-arch size relationship.