November 3, 2022By Dr. TannerIn Invisalign6 Minutes

Interproximal Reduction (IPR)

A key to Invisalign success!

One of the most important “tools” used with Invisalign treatment is interproximal reduction. Also known as IPR, this technique allows the orthodontist to address tooth size discrepancies, alleviate crowding, eliminate triangular spaces between teeth (from gum recession), reduce protrusion and modify tooth shape/form. Before getting into the specifics of these different indications, only an orthodontist or a skilled dentist can perform IPR.

  • Direct-to-consumer companies like Smile Direct Club, Byte, and Candid are severely limited in what cases they can successfully treat with their aligner systems because there is no way to perform “at home” IPR.

What is IPR? IPR involves removing a small amount of enamel along the sides of teeth. The amount of reduction typically ranges from .2mm to .5mm which is about the thickness of 2 to 5 sheets of paper. Enamel width is approximately 1.5mm so this procedure does not compromise the integrity of teeth. Most IPR is performed in the front of the mouth – typically on incisors and canines. Following IPR, the enamel surfaces are polished to preserve surface integrity and prevent plaque retention. The only residual effect from IPR can be a temporary increase to cold sensitivity.

How is IPR performed? First and foremost, the procedure does not require local anesthetic. If necessary, a small amount of topical anesthetic cream can be applied to the gums if polishing is to be done below the gum line. There are many different instruments or tools that can be used for IPR. The simplest is with sanding strips. These are either single- or double-sided thin metal strips with an abrasive coating that can gently remove enamel with a seesaw action. Another option is to use a diamond embedded disk with a protective shield on a slow speed hand piece. The rotating disk is slid between the contact of the teeth and moved in an up and down direction. The patient may feel some vibration but no discomfort. There are other tools, but these are the two most common.

Now let’s get into of the importance of IPR and why it is necessary for so many successful outcomes with clear aligner therapy. As mentioned earlier, IPR helps with the following situations with Invisalign treatment:

  1. Tooth size discrepancies
  2. Alleviation of crowding to avoid tooth or teeth extractions
  3. Elimination of black triangular spaces at gingival margins
  4. Reducing protrusion or flaring of incisors

Tooth size discrepancies occur when teeth (usually the upper lateral incisors) are narrow or there is a missing or extracted lower incisor. In either case, performing interproximal reduction in the opposite arch of the discrepancy (lower arch with small upper lateral incisors or upper arch with a missing / extracted lower incisor) will improve the coordination and fit of the top to bottom front teeth.

Many times, it is not desirable to extract a tooth or teeth to alleviate crowding. However, to prevent unwanted flaring of teeth, expansion of the arches and/or address the arch length discrepancies, the logical choice is to perform IPR. Up to 5mm of space can be gained by removing .5mm of enamel between 10 contacts in each arch. This amount of space gain is appropriate to alleviate mild to moderate crowding.

Flaring of teeth and/or over-expansion of the arches can lead to instability of the occlusion, relapse of alignment (crowding), and gum recession.

Black triangles develop below the contact points of teeth when there has been gum recession and the gum tissue no longer fill the space between the teeth. Black triangles also become apparent when teeth, that have been overlapped for a long time, are straightened with orthodontic treatment. Again, there is an absence of gum tissue to fill the interdental space leaving an unsightly “hole” or void. Reshaping the incisors so that the side walls are less divergent and more parallel allows the orthodontist to bring teeth closer together thus minimizing black triangles.

A final use of IPR is to reduce protrusion of upper teeth. Performing this procedure can dramatically improve the overbite without extracting maxillary teeth. An overbite of 5 to 7mm can be reduced to 2 to 4mm which is within the range of normal. Lip posture will also improve along with facial esthetics as the upper incisors are retracted.

IPR is a beneficial and important “tool” for successful clear aligner treatment. Don’t limit your options – go to a trained orthodontist for Invisalign. There are so many advantages with this amazing system!

If you have questions about the benefits of Invisalign treatment, please call Visage Orthodontics to schedule a visit with Dr. Tanner, your Santa Fe Invisalign specialist. Dr. Tanner will review everything in detail and develop a customized treatment plan to fit your lifestyle and budget.

A confident and beautiful smile is right around the corner!