What does interproximal reduction remove?
Interproximal reduction is a step that slightly reshapes only the side surfaces of the teeth, and only their outer layer, the enamel. It's also called IPR, and it's different from the reduction for porcelain veneers or crowns, which grinds the entire front surface. “You're going to grind the sides of my healthy teeth?” Many people's faces stiffen the moment I explain it, because they're worried their teeth will become sensitive or weak.
Generally, around 0.1–0.5mm is reshaped at each contact, within the thickness of the enamel, and the needed room is opened by spreading it over several contacts. Enamel thickness and tooth width differ from person to person, so the same amount isn't applied to everyone.
When is interproximal reduction done?
- When there's slightly too little room to straighten overlapping teeth (straightening them without room makes the teeth tilt outward)
- When adding a little room in orthodontic treatment without extractions
- When the width ratio of the upper and lower teeth doesn't match, or one tooth is unusually wide
- When moving the contact point toward the gum to reduce a black triangle that appears after the overlap is resolved
| Amount of space lacking | Interproximal reduction | Other methods |
|---|---|---|
| Small | A small amount at several contacts | Not done if there's already room |
| Moderate | Combined with reshaping, moving the molars back, and so on | One method alone doesn't open enough room |
| Large | Not closed with the side surfaces alone | Planning includes extraction or expansion |
How is the amount of interproximal reduction decided?
The needed room is calculated first and then divided across several contacts. For example, if the front teeth are 2mm short of space for alignment, 2mm isn't removed from one spot; it's opened a little at a time across several contact surfaces. In the clinic, I often hear, “How many millimeters will you shave?” Rather than the amount removed, I first decide where the teeth should be after treatment and design the room needed to move them there. Even when the same amount of space is needed, for one person reshaping the side surfaces is right, and for another, moving the molars back or widening the arch is right.
When shouldn't interproximal reduction be done?
If there's already room, or if room can be made by moving the molars back or widening the dental arch, I don't touch the side surfaces. I also don't do it on surfaces that already have cavities, surfaces where the enamel is thin, or surfaces that would trap food after reshaping. Interproximal reduction doesn't replace extraction, so if the shortage is large, I also look at orthodontics with extraction or expansion. Extraction isn't the default either. I don't tell everyone it's fine just because only a little is removed.
Does interproximal reduction cause sensitivity or cavities?
When it's limited to within the enamel, it's often done without anesthesia, and sensitivity is rare or brief. If your gums are sensitive or the teeth were already sensitive, it may be uncomfortable for a while. If the reshaped surfaces aren't finished smoothly, plaque settles easily, so I also explain final polishing, fluoride treatment, and flossing during orthodontic treatment.
During treatment, small gaps may be visible for a while at the reshaped spots, but they close again as the appliance moves the teeth. Seeing a gap doesn't mean the treatment has gone wrong.
How we do it at Wonjin Dental
Just because the front teeth overlap a little, I don't go straight to the side surfaces. I look at the room needed, the tilt of the front teeth, the width of the dental arch, how far the lips protrude, and the bite after treatment together before deciding whether to touch the side surfaces, and I first explain which teeth will be opened and by how much, and how it differs from other methods. I use the same standard for partial orthodontics, which moves only a few front teeth. During your consultation, feel free to ask, “Why do I need interproximal reduction?”
Frequently asked questions
Does interproximal reduction weaken teeth?
Reshaping only a small amount within the thickness of the enamel is considered not to have a significant effect on tooth strength. It isn't done on surfaces that are already thin or have cavities.
Is interproximal reduction done all at once?
Depending on the order of movement, it's done at once or split over several visits. It's often more accurate to reshape after the overlapping teeth have been straightened a little.
Is interproximal reduction done with clear aligners too?
Even with a removable appliance, the same step is included if room is needed. The name of the appliance doesn't create space for you.
Will the reshaped spots open up again after orthodontic treatment ends?
If you wear your retainer well, it's rare for them to open up again. If you neglect your retainer, gaps can form regardless of interproximal reduction.
