Dr. Greg Jorgensen
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Rio Rancho, NM 87124

The Jorgensen Orthodontics Blog

What Is Interproximal Reduction In Orthodontics?

Posted by Dr. Jorgensen on May 24th, 2011

Smiling girlThe 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!

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.

90 comments so far in response to “What Is Interproximal Reduction In Orthodontics?”

  1. haley says:

    how much space can be created to push back protruded teeth with IPR? i have straight teeth little to no crowding my teeth go out a little bit and he wants to extract 4 teeth i’m sure there’s a more conservative way he wants to push it back 2-3 mm

  2. zehra says:

    hi,I am 31 years old and I was having the two upper baby canines non falling.I went to an orthodontist, he made some examinations, he started treatment with first gaining place for the permanent upper canines,then the baby canines have been extracted.İt’s been 6 months from the beginnig of the treatment.My problem is that now the upper front tooth have gone protruded,overjet.Befor my treatment I did not have any overjet.I ask my doctor about this situation, he tells me that my lower jaw is retracted and because there is not enough space for the canines it must be done like this.But now I cannot close my mouth like before and my cheeks are like weakened, people says I do not look like before in a bad way. My doctor proposed to extract two upper first molars to reduce the overjet with a risk of collapsing the upper lip.But I don’t even want any collapse in my upper lip. I was wondering if it could be possible to correct that overjet with IPR instead of extraction ?

    • Your front teeth moved forward because your canines needed more space. If you needed 4mm of space (2 on each side), you’d need 4mm of IPR and that would be way too much. Sometimes extractions are the only way to prevent what you are experiencing.

      • zehra says:

        Thanks for your quick answering, you said if I need 4 mm of space it would be too much of IPR. But in your review above if I had understood correctly it is possible to gain 3 mm of space with IPR of only ¼ mm of enamel polished from each side of the six front teeth. I was wondering if 3 mm of space is not enough to retract the upper front teeth at a level satisfying ? I am an opthalmologist so I can understand if you could explain me in details. Thank you sir.

        • In my experience, the maximum amount of IPR that I feel comfortable with would be between 3mm and 4mm in an entire arch. That equates to 1.5mm to 2.0mm of retraction. That is about the thickness of a dime and really not noticeable to the naked eye. I don’t think that IPR is a good approach to overjet reduction. It just doesn’t accomplish enough for the amount of tooth alteration required

  3. Lisa says:

    Hi Dr. Jorgensen, My new Ortho wants to perform IPR for a very small black hole inbetween my front two teeth and on all my teeth so they can go back smoothly. Along with my bottom jaw because I have one tother poking out (stopped wearing my retainer long time ago for the bottom) I’m worried that IPR may not bring them back to being straight and tightly together when I wear my clear retainer braces to push them back then long term plastic retainers? I’m worried it’s not safe and will make my teeth spaced out with gaps and not go back and look pretty. Meanwhile I met with another Ortho who quickly just suggested I either purchase a new retainer or go through an entire Invisalign procedure for 2 years. Isn’t that crazy how I received 2 different opinions from to Professional DDS? Pleas help, Please advise, Thank you in advance!! Lisa

    • Performing IPR on crooked teeth alone will not get them straight again. The teeth will need to be guided to their new (or former positions) by either braces or aligners. I use IPR all the time, but it is always done as part of treatment so that I can make sure the teeth are straight and the gaps closed.

  4. molly says:

    Does getting IPR hurt? How much can get shaved off (in cm) before hitting there nerves? How long would it take if someone were to get 7 teeth on the bottom slenderized?

    • Interproximal reduction is a fast and simple procedure that does not require anesthesia. I perform it every day and patients are very comfortable. The amount of enamel that is polished away on each surface ranges between 0.2mm and 0.5mm. The procedure itself takes less than a minute for half a dozen teeth.

  5. Yajayra says:

    Hello Dr. Jorgensen,

    I’m currently in braces. In the beginning of my treatment, my orthodontist recommended for me to extract two teeth from the left side of my mouth (one top one bottom) due to severe overcrowding. Now I’m about 2 years into my treatment and have noticed a deviation in my midline. It is slightly off by what I believe to be 2mm (could be up to 3mm), and is off centered from my facial midline (nose). It is really starting to make me feel self-conscious…I will be going to my next appointment soon and will bring up my concern to her, but wanted to know if IRP could be an option in fixing my midline? Is it possible to create the space needed and to move my teeth in the other direction? Do you have any other recommendations for treatment? Thank you in advance!

  6. Reem says:

    I have my 8th tray of invisalign and my dr suggested to me from tve begining that i don’t need to take teeth off but he said instead he will do IPR during my treatment because i’m feeling my teeth is has the forward problem and now with the alignments, i feel it came more forward. will this fix ? or should my dr do the IPR because last time he said you don’t need it yet !

    • Please discuss the need for and timing of IPR with your orthodontist. Many times it has to be delayed until later in treatment for different reasons. If you are still protrusive after the IPR has been performed, it may be that teeth should have been removed all along

  7. Ray says:

    Hi,

    I had 0.8 mm of IPR done in-between all anterior contacts of my lower incisors during Invisalign treatment (i.e. 0.4 mm of enamel was removed from each side). After finishing treatment, these teeth became sensitive to cold temperatures – e.g. drinking cold water and sucking in cold air cause sharp shooting pains in my lower front teeth. I’ve brought this up with my dentist and orthodontist, but both say nothing appears to be wrong. Is it possible that this sensitivity is due to the enamel lost from IPR?

    • It is possible, but uncommon. Everyone is different, so I can’t comment on whether or not 0.8mm was too much in your case. I can tell you that I limit my IPR to 0.5mm in most cases, but I have removed more than 0.8mm in others. It all depends upon the shape and size of the teeth of the patient. I would encourage that you get some topical fluoride to reduce the sensitivity.

  8. Alexa says:

    Hi there so I had braces for maybe 2yrs and have had them off almost a year and my right k-9 tooth shifted upwards and my orthodontist said he left room in my retainer for it to come down like “the book” said but it just slightly shifted upwards. I swear I wore my retainer the entire time. Today he shaved my teeth to allow room for it to come down but I’m worried it won’t and he said I’ll need braces again if it doesn’t work. How long will I it take for my tooth to come down? I really don’t want to wait 6months for braces again and it sucks hating my smile even more now. He said to wear my same retainer only at nights.

    • There is no way to tell if and when that tooth will move. The human body is so variable and what happens with one patient doesn’t always happen with another. You may need braces or aligners for a while more to get exactly what you’re looking for. Good luck!

  9. Tyler says:

    Hey Dr. Jorgensen,

    I remember getting spacers in my back molar teeth and had them for over a week before I had gotten traditional braces to fit those metal things around each tooth on each side for the braces when I was a pre-teen. Although now as an adult, and since I’m not in the same town now, I had gone to a different Orthodontist just to minorly align a few of my bottom inciser teeth with a Hawley retainer with a few S-springs for those teeth, the question I had was instead of using Spacers for the lower front teeth as well to make some room for the minor re-alignment, they decided to perform some IPR in between my two front lower incisors instead, so why do u suppose IPR is used instead of using Spacers in some cases like what I had in my back molar teeth before braces when I was younger? I know at least with the Spacers, it doesn’t remove any enamel at all so I wanted to get a better understanding as to why IPR would be used rather than placing the separaters between the teeth to make some room for treatment.

    Thanks

    • Great question Tyler. If your teeth are crowded because the space where they must be aligned is too small, spreading them out with spacers would not solve the problem. IPR is used when the size of the teeth and the space where they are to be aligned is different. Spacers are used to temporarily push teeth apart so that bands can be placed around them during treatment. The spaces created are not permanent and they go away soon after the bands are removed.

      • Tyler says:

        Hey Dr. Jorgensen,

        Thanks for the reply back on my previous message. Just an update, I’m still in this Hawley retainer to help realign a few of my lower incisors and I had just gone to my local Ortho for a follow up yesterday, and I was a bit surprised they never adjusted the S-springs this time and said to see me back in 8 weeks instead of 4 weeks like usual. This is only my 2nd follow up as I’ve only been in treatment for this since Feb. of 2018. My Ortho claims that I’m still in the treatment phase and that the teeth should improve some more before the 8 weeks which I sure hope so cause I’m getting a little nervous and anxiois now that there’s still this one tooth on the very front left side that’s a bit twisted yet with a slight space from the IPR, but the Ortho says that it should be fine and that there should be some more improvement yet with that space closing and tooth un-twisting.

        My question is now, how is this gonna happen if they didn’t adjust the springs in the back this month? Maybe it’s more of a matter of time vs frequency of adjustments Idk? Also, since my one top incisor tooth rubs up against my lower one a little when biting down, mostly when I first remove my retianers I notice it and they were saying at my follow up, that in order to move that tooth back some to help with the contact between the upper and lower tooth upon biting down, that IPR would have to be done once again but pry in between the teeth next to the other two that were done before tho. They said they can’t move teeth forward or back without creating some space for that first. I’m a bit confused as to why that is tho, cause in your experience, what does creating a little space have to do with pushing teeth back or moving them forward? Is it true too that the S-springs help to rotate the teeth rather than just pushing them outward, and the Hawley retainer metal wire on the front of the teeth almost act like regular braces as far as closing spaces and pushing teeth back goes? I’m trying to seek a second opinion, just to make sure my current Ortho is doing what’s best in my case! Trying to get a peace of mind with this process. Looking forward to ur reply again, seeing what you think of all this.

        Thanks

        • In my experience, the movements you are describing are too complex for a removable Hawley retainer with wires that push on the teeth to straighten them. They do not have enough precision or control to give the results you are seeking. I wouldn’t bet that you’re going to be happy with the results by just wearing your retainer another 8 weeks. The movements you are hoping for require either fixed braces or aligners with attachments glued to the teeth. I would need more “handles” on the tooth to accomplish such precise results.

          • Tyler says:

            Oh bummer, and in regards to the S-spring behind that one tooth of mine, the direction of it goes perpendicular to the direction of my slightly twisted tooth on the lower incisor. I was hoping that maybe that would help to align that tooth some between the S-spring behind it and metal wire in front going across it, so like sandwiching it in to flatten it out some, if that makes sense. This was the most affordable route for treatment in my case according to my Orthodontist that is. Should that slight space between my two front bottom teeth created by the IPR still close up all the way, either with the retainer or on it’s own I hope? In case I decided to discontinue the treatment. I also wanted to mention, upon removing my retainers, I notice my bite is always a little off, like some of my top front teeth hit up against my bottom front teeth and on the one side, my molars seem to not latch all the way when biting down. It slowly starts to improve tho the longer I leave those retainers out for. I wonder how common that is too.

            Thanks

          • You have outlined many reasons why I don’t use removable retainers with springs. They are less precise than aligners or braces. The space between your teeth created by IPR will definitely close, but it may not happen while you are wearing that retainer. I would discuss these issues with your orthodontist and see if you can convince him to use “minor tooth movement” aligners for your correction. I think you’ll be much happier.

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