IPR, or interproximal reduction, is a procedure that removes small amounts of enamel from the sides of your teeth to create space for them to shift into better alignment. It’s one of the most common steps in Invisalign treatment, especially for adults with crowding. The amount removed is tiny, typically a fraction of a millimeter per tooth, and the procedure is a routine part of how clear aligner therapy works.
Why IPR Is Part of Invisalign Treatment
Your teeth need somewhere to go when aligners push them into new positions. If your mouth is crowded, there simply isn’t enough room for everything to line up neatly. IPR creates that room by slimming down the sides of specific teeth just enough for the aligners to do their job.
Without IPR, the main alternative for creating space is extraction, which means pulling a tooth entirely. For many patients, shaving off a hair’s width of enamel is a far less invasive solution. IPR can also help when upper and lower teeth don’t match well in size, a common situation where the teeth technically fit but don’t align properly because of natural size differences. In some cases, it also reshapes teeth that are slightly uneven, improving the final cosmetic result.
How Your Orthodontist Plans IPR
IPR isn’t done on the fly. When your orthodontist designs your Invisalign treatment using the ClinCheck software (the 3D planning tool that maps out every stage of your tooth movement), they decide exactly where IPR will happen, how much enamel to remove, and at which stage of treatment to do it. The software includes a dedicated IPR tool that lets the provider add, remove, or adjust reduction amounts for specific teeth. Some IPR may be scheduled before your first tray, while other reductions might happen partway through treatment, timed to a specific aligner stage.
This digital planning means the amount removed is precise and intentional. Your orthodontist isn’t guessing. They’re working from a model that accounts for every fraction of a millimeter.
What the Procedure Feels Like
IPR is quick and generally painless. Your orthodontist uses thin diamond-coated discs, flexible strips, or a small oscillating handpiece to file between the teeth being treated. Because enamel has no nerve endings on its outer surface, most patients don’t need any anesthesia. You’ll feel pressure and vibration, and you may hear a light grinding sound, but it’s not the same as having a cavity drilled.
Some patients report mild sensitivity afterward, particularly to cold drinks or air. This tends to resolve within a day or two. It’s similar in character to the general tooth sensitivity that many Invisalign patients experience when switching to a new aligner tray, which about 60% of patients describe as mild to moderate and which typically fades within three to five days.
After the enamel is reduced, your orthodontist polishes the surfaces smooth. This step matters because rough enamel can trap plaque more easily. Proper polishing helps the treated surfaces stay clean and healthy.
Is Removing Enamel Safe?
This is the most common concern patients have, and it’s a fair one. Enamel doesn’t grow back, so any amount removed is permanent. But the clinical evidence is reassuring. A well-known study by Zachrisson and colleagues concluded that IPR does not negatively affect the health of reduced teeth. Follow-up research by Jarjoura and colleagues supported this finding, showing that even applying fluoride after IPR provided little additional benefit, suggesting the enamel surface remained healthy on its own.
The key factor is technique. When IPR is performed properly and the surfaces are polished well, there’s no demonstrated increase in cavity risk. However, improper technique can leave deep surface irregularities that polishing alone can’t fix. Rough surfaces like these could promote plaque buildup and potentially increase the risk of cavities, gum inflammation, or sensitivity. This is one reason IPR should be performed by an experienced provider who follows it with thorough finishing.
It’s worth noting that some general dentists are more cautious about IPR than orthodontists. Research published in The Angle Orthodontist found that this hesitancy often stems from unfamiliarity with the studies showing that properly done IPR doesn’t raise cavity rates. Among orthodontists, the procedure is considered routine and well-supported.
What Happens After IPR
Immediately after IPR, you’ll notice small gaps between the treated teeth. These gaps are intentional, and your aligners are designed to close them over the following weeks or months. How quickly they close depends on where the IPR was done, how much space was created, and how your teeth respond to the aligners.
For some patients, the gaps close within a few trays. For others, particularly on the lower teeth or in cases where more enamel was removed, the spaces may remain visible for a longer stretch of treatment. This can be unsettling when you take your trays out to eat, but it’s a normal part of the process. The gaps are only temporary, and the final result accounts for all of that space being reclaimed as your teeth settle into their planned positions.
You don’t need to do anything special to care for your teeth after IPR. Continue brushing and flossing normally, and wear your aligners as directed. The treated surfaces will feel smooth once polished and shouldn’t require any extra maintenance.
How Much Enamel Gets Removed
The amount is small. A typical IPR session removes between 0.1 and 0.5 millimeters per contact point (the spot where two teeth touch). To put that in perspective, tooth enamel is generally 1 to 2 millimeters thick on the sides of your teeth, so IPR takes off only a fraction of what’s there. Your orthodontist uses thickness gauges to measure exactly how much has been removed, staying well within safe limits.
Not every tooth in your mouth will need IPR. Your ClinCheck plan specifies which teeth require reduction and how much. Some patients need IPR on just two or three contact points, while others with more crowding may need it in several areas across both arches.