What is IPR in aligners: Ultimate Guide for Doctors and Patients (2023)

Written by Dr. Febin Mary George | Medically Reviewed by Dr. Zein El Hammouz, DDS, MFD/RCSI.

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Table of Contents:

  1. What is IPR (Interproximal Reduction)?
  2. IPR in Orthodontics
  3. IPR Treatment for Patients
  4. IPR: Pros and Cons
  5. IPR: Before and After

Interproximal reduction is a very common procedure that is performed during orthodontic treatment. Every procedure has its own significance and the same holds true for interproximal reduction or IPR. So, what is IPR (interproximal reduction) and why is it done? Is it really necessary? This article is meant to tell you everything that you need to know about IPR as a doctor or a patient.

1.What is IPR (interproximal reduction)?

Dental IPR, commonly referred to as tooth polishing, slenderization or stripping, is a routine procedure carried out before you start your orthodontic treatment.

Though a very common procedure, IPR orthodontics is not meant to be done for every orthodontic case.

1.1. What does interproximal reduction do?

It involves the removal of a very small amount of enamel interproximally (tooth surfaces or areas between two adjoining teeth) to create space.(1) This space is utilized by the clear aligners or braces to align the crowded teeth.

1.2. Is IPR necessary for clear aligners? What is used for?

Yes, in some select cases, IPR is necessary for clear aligners. Your doctor will inform you if you require IPR after evaluating your case.

The main objective of IPR is to gain space by reducing the width of the teeth. The space so created helps in aligning the crowded teeth in the most natural way within the patient’s mouth.

1.2.1 Provision of/ creating spaces

In some cases, when a tooth is outside the correct dental alignment, the dental arch needs to be expanded minimally to accommodate the misaligned tooth and bring it back to its correct position.(2) Hence, IPR is immensely helpful in patients with slight to moderate dental crowding as one need not plan tooth removal to create space.

1.2.2. Front teeth protrusion

With the help of IPR, protruding front teeth can be fixed.(13) In front teeth protrusion, the upper front teeth flare out and sit infront of the lower front teeth when the upper and lower teeth are brought in contact with each other. In some cases, the lower front teeth can be angled more outwards than upper front teeth. IPR is performed on the front teeth of the protruded arch to make enough room for pulling the front teeth back to normal alignment.

Front teeth protrusion case study related to Interproximal Reduction and its benefits for the orthodontic treatment.

1.3. Interproximal reduction vs tooth extraction

Though interproximal reduction and tooth extraction are ways of gaining space to fix issues with tooth alignment, they are used in different situations.(3) Your dentist along with the Eon Aligner team will decide if IPR is ideal for you or not.

In cases of mild to moderate crowding, IPR may suffice whereas severe or complex crowding cases may need extraction of teeth. By just reducing an extremely thin layer of enamel, extraction of sound and healthy teeth can be avoided in mild cases of crowded or protruded teeth.

2. IPR in Orthodontics

2.1. Why do dentists file teeth for braces?

IPR is an orthodontic technique that flattens the contact surfaces of teeth through filing of the teeth.Dentists employ this technique for managing mild to moderate crowding, reducing the flaring of the front teeth and eliminating the need of tooth removal. (4) With the help of IPR, the teeth need to be moved only to shorter distances as compared to cases of tooth extraction.  Moreover, there is an increase in stability of the orthodontic treatment leading to lesser chances of relapse. According to Sheridan, IPR is very effective in resolving a crowding of 2.5mm in the front teeth.(5)

2.2 How do you explain IPR to a patient?

Patients may not understand what is IPR and what its potential benefits are. Hence, it is necessary for dental practitioners to explain it in simple terms. The best way to describe interproximal reduction would be - “polishing the sides of the teeth to make space, which can be used to align the teeth correctly.”

Dentist educating male patient about what is IPR and clear aligner treatment.

2.3. How to perform IPR?

2.3.1 Pre-IPR review by a doctor

  • The amount and the timing of IPR are predetermined and planned during the treatment setup phase with the help of our software. However, doctors should be able to make the final decision about when they need to perform the recommended IPR.
  • The doctor needs to confirm whether a separator like rubber or wire needs to be placed in between the teeth to create enough room for the IPR disc to pass interproximally with ease.
  • The dental practitioner should ascertain which teeth surfaces need to be reduced.
  • Finally, the doctor will decide the instruments and techniques required for IPR.

2.3.2. Pre-IPR preparation by staff

  • The treatment plan of the patient should be reviewed to find out if IPR is recommended for this visit or not.
  • If IPR is recommended, it needs to be confirmed whether the patient knows all about the procedure and has duly signed the informed consent form.
  • Arrange the necessary instruments for the doctor.
  • Know the spots and measurements of the recommended IPR.

2.3.3. Pre-IPR preparation of the patient

  • The entire IPR procedure should be explained to the patient and/or patient’s guardian.
  • Discuss the possible side effects of the procedure like minimal gum bleeding gums, sensitivity or improvement in the shape of the teeth.
  • If any pre-IPR separators need to be placed, they can be positioned with the help of a little numbing gel.

2.3.4. IPR kit

Generally, the IPR dental kit contains the following products-

  • Handheld abrasive strips
  • Abrasive strips with manual holder
  • Files that can be attached to a handpiece that works in oscillatory motion
  • Discs that are used in conjunction with a slow-speed handpiece
  • Disc guards that hold the discs so that they can attached to the handpiece
  • Diamond burs that can be fixed to high-speed handpiece.
  • Remineralization and hypersensitivity products like fluoride varnish.

Interproximal reduction file used to create space between teeth to allow tooth movement.

Picture depicting an Eon Aligner company tool used to work with clear aligners.

2.3.5. IPR techniques

Manual method

  • This method is used for minimal reduction.
  • The abrasive strips with manual holders are held and passed in between the teeth in a back-and-forth motion.
  • This method gives better control to the doctor.

Mechanical method

  • Mechanical method is considered when the IPR is slightly beyond the scope of manual reduction. (6)
  • There is no need for topical anesthesia as only a thin layer of enamel is shaved off without disturbing the underlying nerves and blood vessels.
  • If the teeth are too crooked, pre-IPR separation is recommended with the help of a saw that is used to break the contact points between adjacent teeth.
  • The enamel layer is trimmed in increments and after every step, the amount of space created by IPR  is measured with the help of a gauge. This step is done to prevent overtrimming.

2.4. Interproximal reduction for Black Triangles

Are you upset with those black triangular spaces in between your teeth when you smile? Interproximal stripping could be the right solution for you! Black triangles are actually open gingival embrasures and you may be having them due to-

  • Crowding- When crooked teeth are straightened through braces, the receding gum line becomes more and more visible revealing the dark triangles.(7)
  • Triangular shape of the teeth- The contact surface between triangular shaped teeth is less when compared to rectangular shaped teeth. Hence, there are more dark spaces shown in triangular shaped teeth.

"Black triangles between teeth. Triangular tooth shape  that can be fixed with clear aligner treatment "

2.5. Interproximal reduction for flared teeth

Flared teeth is when the upper front teeth called the incisors are projecting outwards and forwards. (14)Trimming the teeth through IPR makes it possible for the orthodontists to pull the flared teeth back through clear aligners by making use of the space created by interproximal reduction.

3. IPR Treatment for Patients

3.1. Candidates for IPR

IPR is an excellent non-invasive technique of creating space that can help in bringing about effective teeth movement through clear aligners. The ideal candidates for IPR are those with (8):-

  • Minor Class II discrepancy
  • Crowding
  • Tooth size discrepancy
  • Minor Class III dicrepancy

3.2. Does interproximal reduction damage teeth?

No. The tooth is reduced by orthodontists who understand the physiology of every tooth. Hence, you can rest assured that your teeth will not be damaged as the reduction is done in accurately, in harmony with the natural oral structure, based on the correct measurements.

3.3. Is interproximal reduction painful?

Your nerves that pick up the pain signals are located within the pulp, the deepest layer of the tooth. As enamel is the most superficial layer and only an extremely thin layer is shaved off during the process of slenderization, you will not feel any pain.

Three-dimensional representation of a tooth pulp chamber, depicting all its parts.

3.4. Does enamel grow back?

No. Once the enamel is lost, it will not grow back. But the good news is that the enamel removed through IPR is well within the safe limits and will not pose any harm to you as it’s very minimal.

3.5. Will it give me gum disease?

IPR, specifically, will not lead to gum disease, whatsoever.(9) Gum diseases totally depend on the way you maintain your oral hygiene. Hence, brush and floss routinely so that your gums remain healthy and strong

3.6. How much can a doctor remove with IPR?

Studies show that 50% of the enamel on the proximal surface of a tooth can be safely trimmed without any periodontal or dental risks.(10) Most commonly, only a very fine layer of enamel is removed. And the recommended amount is  most of the time divided between two teeth. For instance, if 0.5mm IPR is recommended for one contact point, then 0.25mm from each tooth of that contact point is removed.

3.7. How long does it take?

The entire procedure may take only a couple of minutes and a bit longer when done manually. The time depends on the number of teeth that need to undergo IPR.

3.8. How much does interproximal reduction cost?

The cost of IPR dental may vary according to the patient needs. Minor IPR procedures may cost you anywhere between $50 to $300. Contact your orthodontist to get a clearer picture about the cost of every step involved in your clear aligners treatment.

4. Interproximal Reduction: Pros and Cons

4.1 Interproximal reduction side effects

While opting for clear aligners, you should consider consulting a qualified dentist who has the necessary skillset to meet your dental needs effectively. Every step of clear aligners need accuracy and genuine experience so as to achieve the desired outcome.

IPR may have a couple of side effects. Most of these are due to excessive trimming or inaccuracy of the dentist. Common side effects of interproximal reduction are (11)-

  • Increased sensitivity to hot and cold foods
  • Slight discomfort during the procedure
  • Damage to pulp (nerve tissue) with excess trimming- There is a high possibility of pulp damage in young patients as they have large pulp chambers

5. IPR Before and After

Before IPR, the orthodontic specialist should evaluate the condition of every tooth in the arch and then decide on the amount of IPR needed. This is because every tooth has a different morphology and hence, a different thickness of enamel interproximally.

After IPR, the specialist polishes the trimmed interproximal surface to avoid creating ledges . In some cases, you may be advised to avoid cold beverages in the first few days after IPR to reduce discomfort. Your doctor will note down all the changes in width of the teeth due to interproximal reduction before and after.



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