How do teeth get stained?
Over time, salivary proteins build up on tooth enamel forming a thin film or “pellicle” on the surface of the tooth. Food particles, bacteria, and teeth staining agents tend to cling to this film. The pellicle provides protection for the tooth from acids that would attack the enamel. Chewing wears away the pellicle on the biting surfaces of teeth, but within two hours the pellicle is filled in, as soon as saliva comes in contact with the teeth again.
Tooth enamel’s hydroxylapatite crystal rod matrix is naturally porous leaving teeth vulnerable to staining agents without the pellicle’s protective properties. The pellicle doesn’t only remain on the surface of the tooth, but can also penetrate into the enamel. Researchers have discovered that some dental bacteria can actually eat through the pellicle and reach the insides of the enamel where there pellicle has already burrowed.
Eating and drinking acidic things followed by improper brushing and flossing techniques can damage the pellicle and cause the mineral matrix of the enamel to break down in a process called “demineralization”. When the mineral matrix weakens, microscopic spaces in the enamel remain open longer allowing stains to work their way below the surface.
Unfortunately, the pellicle’s sticky nature also contributes to tooth staining. Food particles and staining substances like tannins and other pigments to cling to the pellicle and alter the appearance of the teeth. The pellicle and related surface stains can’t be cleaned away by brushing alone. And so, may people turn to whitening products.
What causes Teeth Stains?
Teeth stains happen for a variety of reasons. But, generally speaking, there are two main categories of teeth staining: intrinsic and extrinsic.
Extrinsic staining happens on the outside of the tooth or enamel and is caused by dyes or pigments (chromogens) in food and drinks that stick to the pellicle, thereby changing the color of the tooth, and by substances that cause a chemical interaction on the tooth surface. Food dyes are considered non-metallic sources of tooth discoloration; chemical interactive substances are considered “metallic”. Such substances include:
- Red wine;
- Coffee, tea, soda, sports drinks;
- Blueberries, raspberries;
- Apples and potatoes;
- Over exposure to metallic salts, eg: iron, copper, potassium permanganate, silver nitrate, stannous fluoride;
- Chlorhexidine mouthrinses (Chlorhexidine is known as a cationic antiseptic)
The basic rule of thumb when it comes to figuring out whether a food will stain your teeth or not is that if you’re worried that the food will stain clothes, it will also stain your teeth.
Intrinsic staining is discoloration that happens inside the tooth. Interior staining of teeth can be caused by:
- Medications (eg: tetracycline, doxyxycline) -Tetracycline and doxyxycline are antibiotics and are used to treat bacterial infections, acne and asthma among other uses;
- Medical treatments (eg: chemotherapy);
- Tooth decay;
- Fluorosis caused by over-exposure to fluoride;
- Conditions during pregnancy that affect mineralization of enamel in utero; and,
- Root decay and root canal treatment.
Teeth can also change color as the enamel erodes over time and the yellowish dentin beneath shows through or is exposed completely. This can happen due to:
- Normal wear and tear;
- Decreased or inadequate saliva production;
- Gastro esophageal Reflux Disease (GERD);
- Clenching and grinding of the teeth (bruxism); or,
- Acidic foods or drinks.
Silver fillings (amalgam) may also affect the color of areas of the tooth around the filling.