MI Paste is applied directly to your teeth after brushing, left on for a minimum of 3 minutes, and then spit out without rinsing. The paste delivers calcium and phosphate to your enamel in a form that can absorb into weakened areas, making it a popular recommendation for sensitivity, dry mouth, and white spot lesions after braces. Getting the technique right is simple, but a few details make a real difference in how well it works.
How MI Paste Works on Enamel
The active ingredient in MI Paste is a milk-derived compound called Recaldent (CPP-ACP). It works by stabilizing clusters of calcium, phosphate, and hydroxide ions into tiny complexes that stay dissolved rather than clumping together. When you apply the paste to your teeth, these ions settle onto the enamel surface and diffuse into weakened areas beneath it. This process, called remineralization, essentially resupplies the minerals your enamel has lost to acid exposure.
There are two versions of the product. Standard MI Paste contains only CPP-ACP. MI Paste Plus adds 900 ppm of fluoride, which allows the compound to also form calcium fluoride phosphate complexes. The fluoride version is often recommended for people at higher risk of cavities, while the original version is suitable for anyone who already uses a fluoride toothpaste and wants additional mineral support.
Step-by-Step Application
Start by brushing your teeth with your regular toothpaste and flossing as usual. MI Paste is not a replacement for toothpaste. It goes on after your normal routine.
Squeeze a pea-sized amount onto a clean finger or a cotton swab. Spread a thin layer across all the surfaces of your teeth, paying extra attention to any areas your dentist has flagged, such as white spots or sensitive zones near the gumline. You don’t need a thick coating. A thin, even film gives the minerals enough contact with your enamel.
Once applied, leave the paste on your teeth for a minimum of 3 minutes. The manufacturer’s instructions say to hold it in your mouth “as long as possible,” so longer is better. Many people leave it on for 5 to 10 minutes. During this time, try not to swallow it. Let your saliva pool and spit as needed.
After the waiting period, spit thoroughly but avoid rinsing your mouth with water. Skipping the rinse lets residual minerals continue absorbing into your enamel. Do not eat or drink for 30 minutes after application.
Using a Custom Tray
If your dentist has made you a custom fluoride tray (the kind that fits snugly over your teeth), you can load MI Paste into the tray instead of using your finger. Squeeze a thin ribbon of paste along the inner surface of the tray, seat it over your teeth, and leave it undisturbed for a minimum of 3 minutes. This method keeps the paste in even contact with every tooth surface, which can be helpful if you’re treating widespread white spots or generalized sensitivity. After removing the tray, spit thoroughly and avoid rinsing.
When and How Often to Apply
The most effective time to use MI Paste is at bedtime, after your final brushing. Your saliva flow drops significantly while you sleep, which means less natural rinsing and more time for the minerals to work. Applying it right before bed maximizes contact time.
Once daily at bedtime is the standard recommendation. Your dentist may suggest twice daily (morning and night) if you’re dealing with active sensitivity, high cavity risk, or significant white spot lesions. Follow whatever frequency your provider recommends, since needs vary quite a bit depending on your situation.
What MI Paste Can and Can’t Do
MI Paste is commonly recommended for white spot lesions, the chalky white marks that often appear on teeth after braces come off. It’s also used for tooth sensitivity, dry mouth symptoms, and general enamel strengthening. The logic is sound: delivering extra calcium and phosphate to demineralized enamel helps rebuild its mineral content.
The clinical evidence, however, is more modest than you might expect. A randomized controlled trial of 115 patients with white spot lesions found that MI Paste Plus did not produce significantly better results than normal home care over an 8-week period. Professional evaluators saw about 21% improvement in the MI Paste Plus group compared to 27% in the control group that used only standard oral hygiene. This doesn’t mean the product is useless, but it does suggest that consistent brushing, flossing, and fluoride toothpaste do most of the heavy lifting. MI Paste is best understood as a supplement to good habits, not a substitute for them.
MI Paste will not reverse cavities that have already broken through the enamel surface. Once decay creates an actual hole in a tooth, that damage requires a filling. The product targets early-stage demineralization, the soft, weakened enamel that hasn’t yet progressed to a cavity.
Who Should Not Use MI Paste
MI Paste is derived from casein, a milk protein. If you have a milk protein allergy, do not use any version of the product. The labeling also warns against use by anyone with a hydroxybenzoates allergy, which relates to a preservative in the formula. If you experience any allergic reaction (swelling, itching, rash), stop using it immediately and rinse your mouth with water.
For children, MI Paste products are considered safe from age 2 and up when used in pea-sized amounts. Children under 6 should be supervised to avoid swallowing, and the tube should be kept out of their reach. For children under 2, check with a dentist or pediatrician before using it.
Storage and Shelf Life
Both MI Paste and MI Paste Plus have a shelf life of 30 months from the date of manufacture. Store the tube at room temperature and check the expiration date printed on the packaging. An expired tube won’t be harmful, but the mineral compounds may lose effectiveness over time.