Interproximal reduction (IPR) (also called interproximal enamel reduction, slenderizing, air rotor stripping (ARS) or reproximation) is the practice of mechanically removing enamel from between the teeth to achieve orthodontic ends, such as to correct crowding, or reshape the contact area between neighboring teeth.
In 1944, Murray L. Ballard was the first to advocate for the stripping of the lower anterior teeth due to crowding in a paper published in The Angle Orthodontist. Other authors, also advocated about slenderizing the teeth for next 40 years but it was not until 1980s when John J. Sheridan's Air Rotor Stripping technique for Interproximal Reduction capture society wide interest. He published two papers in the Journal of Clinical Orthodontics in which he explained his ARS technique. He stated that the procedure of IPR can be used as an alternative to procedures of extraction or expansion of teeth during orthodontic treatment. In 2004, Zachrisson stated that IPR can be used to improve the esthetics of anterior teeth. When a crowded arch is aligned, "Black Triangles" form which can be removed with IPR of the anterior teeth.
Some evidence suggests that modern diets of soft and processed foods have resulted in a significant decrease in natural interproximal wear, making dental crowding more prevalent in modern populations.
About 50% of proximal Enamel can be stripped without causing any dental or Periodontal problems. According to Sheridan, 2.5mm of space from IPR of five anterior contacts and 6.4mm of space from IPR from eight posterior contacts can be obtained. It was recommended that no more than 0.5mm - 0.75mm should be removed from each proximal side of the anterior teeth.
Indications for IPR procedure are mild to moderate crowding, black triangles in anterior teeth.
Excessive heat is known to cause damage to the pulp of the tooth. Therefore, to protect pulp against potential damage of heat both Sheridan and Zachrissan recommend that water must be used while IPR to reduce any side-effects of this procedure on the dental pulp. IPR has also been known to cause caries and periodontal disease in teeth. However, the association has been a topic of debate for many years now. In fact, an observational study done by Zachrisson which looked at 61 subjects who went through IPR 10 years post-operatively, found that there was no signs of gingival recession or thinning of the labial gingiva in 93% of the patients.
It is recommended that to limit any side-effect of IPR, topical fluoride application on the treated teeth or part-time wear of a thermoformed Fluoride varnish infused retainer. In a study where participants received fluoride after IPR, it was determined that this group had lesser chances of developing caries on the tooth surfaces treated with IPR than the group who did not receive any fluoride.
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