MI Paste is a tooth cream made by GC America that delivers calcium and phosphate directly to your enamel, helping repair early damage and reduce sensitivity. It’s not a regular toothpaste. You use it after brushing as a separate treatment step, and it works by restoring minerals that acids and bacteria strip away from your teeth over time.
How MI Paste Works
The key ingredient in MI Paste is a compound called Recaldent, derived from milk protein. It goes by the technical name CPP-ACP (casein phosphopeptide-amorphous calcium phosphate), but what matters is what it does: it keeps calcium and phosphate in a form your teeth can actually absorb. Normally, calcium phosphate becomes insoluble at neutral pH and can’t penetrate enamel effectively. The milk-derived protein in MI Paste holds these minerals in a stable, amorphous state so they stay available at the tooth surface.
Once applied, the protein attaches to the biofilm on your teeth and releases calcium, phosphate, and hydroxide ions right where they’re needed. This creates a supersaturated environment around the enamel, which slows mineral loss and accelerates the natural repair process. Think of it as flooding the tooth surface with the exact building blocks enamel is made of, in a form that can actually be incorporated back into weakened areas.
MI Paste vs. MI Paste Plus
There are two main versions. Standard MI Paste contains only CPP-ACP with no fluoride, making it suitable for people who want or need a fluoride-free option. MI Paste Plus adds 900 ppm of fluoride to the formula. Fluoride enhances remineralization by helping calcium and phosphate bind more tightly into the enamel crystal structure, so the two ingredients work synergistically.
GC America also makes a product called MIPaste ONE, which is formulated more like a traditional toothpaste. It contains sodium fluoride (0.24%) and potassium nitrate (5%) alongside bioavailable calcium. This version is designed as an all-in-one anti-cavity toothpaste rather than a separate treatment step.
What MI Paste Is Used For
White Spot Lesions
One of the most common uses is treating white spot lesions, those chalky white marks that often appear on teeth after braces come off. These spots are areas where minerals have leached out of the enamel but the surface hasn’t broken down into a full cavity yet. In a clinical trial published in the Dental Research Journal, patients who applied MI Paste Plus nightly for 12 weeks saw a 65% reduction in the area of their white spot lesions. Their mineral content increased by about 16%, compared to just 5% in a control group using standard home care alone. The appearance of the spots also improved significantly.
Tooth Sensitivity
MI Paste also helps with sensitivity. When applied to teeth, the calcium phosphate compound precipitates onto exposed dentin and physically plugs the tiny tubules that transmit pain signals to the nerve. In a randomized clinical trial studying bleaching-related sensitivity, about 80% of participants reported reduced sensitivity with MI Paste use. The average pain score over a 14-day bleaching period was 27.5 with MI Paste versus 37.9 without it.
Other Common Uses
Dentists also recommend MI Paste for patients with dry mouth (which accelerates enamel breakdown due to reduced saliva), after professional teeth whitening, for early-stage cavities that haven’t progressed beyond the enamel surface, and for people at high risk of decay due to diet, medications, or medical treatments like radiation therapy.
How to Apply MI Paste
MI Paste is typically used once daily at bedtime. The steps are straightforward:
- Brush first. Clean your teeth thoroughly with regular toothpaste to remove plaque and food debris.
- Apply a pea-sized amount along the gum line of your upper and lower teeth, focusing on any areas with white marks or known weak spots.
- Leave it on for 2 to 3 minutes. Don’t spit or swallow during this time.
- Spit out the excess after the waiting period, but do not rinse your mouth.
- Avoid eating or drinking for 30 minutes after application.
The goal is to let the paste sit on your teeth as long as possible. Leaving it on overnight gives it extended contact time. In clinical studies, some protocols used a clear retainer to hold the paste against the teeth for 30 minutes, which can be helpful if you’re targeting specific areas. Your dentist can advise whether a tray-based approach makes sense for your situation.
Safety and Who Should Avoid It
MI Paste is classified as an over-the-counter product and no harmful effects were observed in clinical trials. However, because the active ingredient is derived from milk protein (casein), anyone with a milk protein allergy or a hydroxybenzoates allergy should not use it. This is a genuine safety concern, not a minor precaution. The product labeling also states it should be kept out of reach of children under 6.
For people with milk allergies who still want a remineralizing paste, other calcium phosphate products exist that don’t use casein as the delivery mechanism. Your dentist can point you toward an appropriate alternative.
What to Realistically Expect
MI Paste isn’t a miracle product, and it won’t reverse cavities that have already broken through the enamel surface. It works on early, pre-cavity damage where the mineral structure is weakened but still intact. For white spot lesions, clinical results show meaningful improvement over about 12 weeks of consistent nightly use. You won’t see dramatic changes in the first few days. For sensitivity, relief tends to be faster, with many people noticing a difference within the first couple of weeks.
Results depend heavily on consistent use. The paste works by maintaining a mineral-rich environment at the tooth surface over time, so sporadic application won’t deliver the same benefit as a nightly routine. It also works best as part of an overall oral care plan that includes proper brushing, limiting acidic foods and drinks, and regular dental visits to catch problems before they progress beyond the point where remineralization can help.