What Is Interproximal Reduction In Orthodontics?

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The size and shape of the teeth can have as much to do with the appearance of your smile as anything that the orthodontist does with braces during treatment. Sometimes the teeth themselves must be altered to give the best orthodontic result. Interproximal reduction is one procedure that your orthodontist may use to make the teeth fit and look their best.

Interproximal reduction (IPR) is a simple procedure during which your orthodontist uses very precise tools to change the shape and size of your teeth, primarily on the sides where they touch each other. This is done for three reasons. First, the upper or lower sets of teeth may be naturally the wrong size and don't fit together well. Second, the shape of individual teeth may not allow them to lay next to each other ideally. This can adversely affect the appearance of a smile even though the teeth may fit perfectly. And third, IPR is used in cases of mild crowding so that the removal of teeth can be avoided.

When the teeth are the right sizes, the upper and lower sets fit together like gears. The upper teeth are naturally wider because they fit on the outside of the bottom teeth. This is most obvious when comparing the size of the upper and lower front teeth. If the upper teeth are too wide or the lower teeth are too narrow, an overbite, crowding of the upper teeth, or spaces present in the lower arch may result. If the upper teeth are too narrow or the lower teeth are too wide, there will be spaces in the upper, crowding in the lower, or an underbite relationship. Dr. Wayne Bolton was the first dentist to scientifically explain this back in 1958. If the upper and lower arches do not match because of their size, orthodontists say that the patient has a "Bolton discrepancy."

There are two options for correcting a Bolton discrepancy - making the teeth in the smaller arch bigger (composites, veneers, or crowns) or making the size of the teeth in the bigger arch smaller (interproximal reduction). In most patients there is plenty of extra enamel between the teeth. Using very thin diamond embedded tools, your orthodontist can polish away small amounts of enamel to allow your teeth to fit better. This is a quick, painless procedure than can be done without anesthesia. Not only does it solve the size problem, it is a far more permanent solution than adding artificial materials to the natural teeth in the smaller arch.

The second time your orthodontist may use interproximal reduction during your treatment is when you have teeth shaped such that they don't fit next to each other very well. This is most obvious in the front part of the mouth where two triangular shaped teeth are touching near the biting edges but there are triangular-shaped spaces closer to the gum line. These are sometimes called "dark triangles." The presence of dark triangles is determined by the shape of the teeth and the height of the gums between them. Your dentist can tell you how much each of these two variables contributes to your situation and if using IPR will improve the appearance of your smile.

The last reason for using IPR is when there is too much crowding to align the teeth as they are, but not enough to justify removing any. Interproximal reduction not only reduces crowding, it also creates smooth, flat surfaces that keep the teeth straight better after the braces have come off. Substantial amounts of space can be created by removing only tiny amounts of tooth structure from multiple teeth. If only ¼ mm of enamel is polished from each side of the six lower front teeth, the total amount of space created is 3mm!

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Research supports the use of interproximal reduction by showing no increased decay on the altered surfaces, greater stability after treatment, and no increase in sensitivity when the amount of enamel removed is kept within reasonable limits. Ask your orthodontist if interproximal reduction is right for your particular situation.


NOTE: The author, Dr. Greg Jorgensen, is a board-certified orthodontist who is in the private practice of orthodontics in Rio Rancho, New Mexico (a suburb on the Westside of Albuquerque). He was trained at BYU, Washington University in St. Louis, and the University of Iowa in the United States. Dr. Jorgensen’s 25 years of specialty practice and nearly 10,000 finished cases qualify him an expert in two-phase treatment, extraction and non-extraction therapy, functional orthodontics, clear aligners (Invisalign), and multiple bracket systems (including conventional braces, Damon and other self-ligating brackets, Suresmile, and lingual braces). This blog is for informational purposes only and is designed to help consumers understand currently accepted orthodontic concepts. It is not a venue for debating alternative treatment theories. Dr. Jorgensen is licensed to diagnose and treat patients only in the state of New Mexico. He cannot diagnose cases described in comments nor can he select treatment plans for readers. Please understand that because he has tens of thousands of readers each month, IT IS IMPOSSIBLE FOR HIM TO RESPOND TO EVERY QUESTION. Please read all of the comments associated with each article as most of the questions he receives each week have been asked and answered previously. The opinions expressed here are protected by copyright laws and can only be used with written permission from the author.