Teeth stain from two broad categories of causes: substances that build up on the outer surface and changes that happen inside the tooth itself. Understanding which type you’re dealing with matters because surface stains can often be polished or brushed away, while internal discoloration requires chemical whitening or professional treatment to improve.
Surface Stains vs. Internal Discoloration
Dentists sort tooth staining into extrinsic (surface) and intrinsic (internal). Extrinsic stains collect on the thin protein film that coats your enamel within seconds of brushing, called the pellicle. This film is sticky by nature; it increases the ability of pigmented compounds and bacteria to latch onto the tooth. Plaque and tartar buildup give stains even more surface area to grab onto. That’s why staining is less likely on a clean, smooth enamel surface and more likely in areas where brushing and flossing are inconsistent.
Intrinsic stains sit inside the tooth structure, either in the enamel or the deeper layer called dentin. They can form during childhood while teeth are still developing, or accumulate with age. One important detail: extrinsic stains that sit on the tooth long enough can eventually work their way inward and become intrinsic, which is a good reason not to ignore surface discoloration.
Food, Drinks, and How They Leave Color Behind
The biggest everyday culprits are coffee, tea, red wine, and deeply pigmented foods like blueberries and tomato sauce. These contain chromogens, intensely colored molecules that bond to the protein pellicle on your teeth. Tea and red wine also contain tannins, compounds that help chromogens stick more effectively. Some stains bond directly and strongly to the pellicle, while others get trapped in plaque and tartar deposits already sitting on the tooth.
Acidity plays an underappreciated role. Enamel starts to soften and lose minerals at a pH of about 5.5, and many popular drinks fall below that threshold. Citrus juice, soda, sports drinks, and wine are all acidic enough to temporarily weaken enamel, making it more porous. A more porous surface absorbs pigment more readily. This is why drinking orange juice before coffee, or swirling red wine that’s both acidic and deeply pigmented, is a particularly effective recipe for staining.
Rinsing your mouth with water after acidic or pigmented foods helps wash away chromogens before they bind. Waiting 20 to 30 minutes before brushing after something acidic gives your saliva time to re-harden the enamel so you don’t scrub away softened mineral.
Tobacco and Nicotine Products
Smoking is one of the most powerful staining agents. Cigarette smokers show roughly 35% worse dental discoloration compared to people who have never smoked, measured on standardized whiteness scales. The primary offender is tar, the sticky residue of combustion, which deposits dark brown and yellow pigments directly onto enamel and into the pellicle.
E-cigarettes and heated tobacco products stain teeth significantly less than traditional cigarettes. Research from the Center of Excellence for the Acceleration of Harm Reduction found that exclusive users of these devices had teeth nearly as white as former smokers who quit entirely. The reason is straightforward: these devices don’t burn tobacco, so they don’t produce the tar-based pigments responsible for most smoking-related discoloration. Nicotine itself has a yellowish tint and can contribute some staining, but it’s far less aggressive than tar.
Medications That Change Tooth Color
Several common medications cause staining through different mechanisms. Tetracycline antibiotics are the most well-known offender. When taken during tooth development (roughly before age eight, or during pregnancy), they bind permanently into the tooth structure, producing grey, yellow, or brown bands that darken with light exposure over time. This is a true intrinsic stain and one of the hardest to treat.
Chlorhexidine, a prescription antibacterial mouthwash often prescribed after dental procedures, leaves yellowish-brown surface stains with regular use. These are extrinsic and can be removed by a dental cleaning, but they build up quickly if you’re using the rinse daily.
A less obvious category includes medications that cause dry mouth as a side effect. Antihistamines like diphenhydramine, blood pressure medications (including ACE inhibitors, calcium channel blockers, and beta-blockers), and many antidepressants reduce saliva flow. Saliva is your mouth’s natural rinse cycle. It washes away food debris, neutralizes acids, and keeps the pellicle from accumulating too much pigment. When saliva production drops, staining from every other source on this list gets worse. Cholesterol-lowering medications in powder form, like cholestyramine, can also discolor teeth when sipped slowly, because the liquid sits against the enamel for an extended time.
Dental Trauma and Nerve Damage
A tooth that turns grey or dark brown after being hit or injured is showing signs of internal bleeding. The impact ruptures tiny blood vessels inside the tooth’s pulp chamber, and blood seeps into the microscopic tubes that make up the dentin layer. As hemoglobin breaks down, it leaves behind iron-containing deposits called hemosiderin that can’t be reabsorbed. The tooth darkens from the inside out.
This doesn’t always mean the nerve has died. Some traumatized teeth that turn grey will gradually lighten as the body partially clears the blood breakdown products. Others stay dark permanently, which may or may not indicate a dead pulp. A dentist can test nerve responsiveness to determine whether the tooth needs further treatment. Internal bleaching, where a whitening agent is placed inside the tooth, is sometimes effective for this type of discoloration.
Fluorosis and Developmental Stains
Fluoride strengthens enamel and prevents cavities, but too much during childhood tooth development causes fluorosis, a condition that produces white spots, streaks, or in severe cases brown pitting on the enamel surface. The U.S. Department of Health and Human Services recommends a fluoride concentration of 0.7 milligrams per liter in drinking water, a level designed to protect teeth without causing cosmetic damage.
Fluorosis happens when children ingest excess fluoride from multiple sources simultaneously: fluoridated water, swallowed toothpaste, and fluoride supplements. The risk window is primarily from birth through about age eight, while permanent teeth are forming beneath the gums. Mild fluorosis (faint white lines) is common and purely cosmetic. Severe fluorosis with brown discoloration is rare in areas where water fluoridation is properly managed.
Aging and Natural Wear
Teeth naturally yellow with age for a straightforward structural reason. The outer enamel layer is translucent white, while the dentin underneath is naturally yellow. Over decades, enamel thins from normal chewing, acidic foods, and brushing. As the enamel layer gets thinner, more of the yellow dentin shows through. At the same time, dentin itself gets thicker and darker with age. The combined effect is a gradual shift from bright white toward yellow that no amount of brushing will reverse because the color change isn’t on the surface.
What Works for Each Type of Stain
Surface stains respond to mechanical removal. Regular brushing with a whitening toothpaste (which contains mild abrasives), professional cleanings, and good flossing habits keep chromogens from building up. Once surface stains are established, a dental hygienist’s scaling and polishing instruments are usually effective.
For deeper or intrinsic stains, chemical whitening is the standard approach. Over-the-counter whitening strips typically contain around 6.5% hydrogen peroxide. Custom trays from a dentist commonly use 10% carbamide peroxide (which breaks down into roughly 3.5% hydrogen peroxide) worn overnight. In-office power bleaching uses concentrations up to 35% hydrogen peroxide, sometimes with light activation, and produces faster results in a single visit. Higher concentrations aren’t always better for long-term outcomes, but they do work faster.
Tetracycline staining, severe fluorosis, and trauma-related grey teeth are the most stubborn cases. These often require either extended bleaching protocols, internal bleaching for individual teeth, or cosmetic coverings like veneers when whitening alone isn’t enough.