Nearly everyone takes it for granted that white teeth are a good thing, a desirable thing. The whiter the better! Well, it’s true. One reason the appeal of a gleaming smile seems to be instinctive is that white teeth are an indicator of youth and health. Our distant ancestors no doubt relied on this and other physical characteristics in selecting mates.
Today, our social lives and relationships are still shaped by the appearance of our teeth. Research has consistently shown that people with white teeth are judged more appealing, even when the judges are not able to explain why they found them more appealing. People with discolored teeth are often perceived as cold, or distant, because they control their facial expressions to conceal their dental issues. We want white. Here’s the “how”.
WHAT COLOR ARE TEETH, ANYWAY?
Three elements give a tooth its color: enamel, dentin, and light.
Enamel is the outermost layer of a healthy tooth. It’s the hardest tissue in the human body and serves to protect the softer dentin layer under it, and the innermost soft tissues, the pulp and nerve. Enamel has three properties which determine its contribution to the tooth’s color.
Enamel is translucent. Some of the light striking it passes through and is reflected back by the dentin. The texture of enamel, smoother or rougher, affects the way light passes through it and is reflected by it. It’s porous, so it absorbs substances that come into contact with it. Thicker, smoother, unstained enamel reflects more light and has a brighter, whiter look.
Dentin, the layer beneath the enamel, is yellow. Therefore, the thinner enamel is, the more the yellow tone of the dentin contributes to the tooth’s color.
Enamel’s thickness is initially determined by genetic endowment, but over the course of our lives, things like acidic food and drinks, brushing, decay, and aging tend to make it get thinner. Other things being equal, there is a trend over time toward the dark and yellow. Dentin itself tends to darken with age, compounding the trend.
In addition to the darkening trend due to thinning enamel, we stain our teeth with the foods and beverages we consume. The pores in dental enamel, and any plaque that we’ve allowed to form on our teeth, readily absorb stain from dark-colored drinks like red wine, cola, coffee, tea, and the berry juices. Any foods that can stain your tablecloth, like beets and blueberries, probably can stain your teeth, too. Tobacco use is an infamous cause of stained teeth.
Infected root canals darken teeth from the inside. The dying tissues turn brown and soak into the surrounding dentin, which darkens, in turn.
Childrens’ teeth can be stained by tetracycline antibiotics taken before age 8, or if mom took tetracycline during the second half of her pregnancy. Excessive exposure to fluoride at critical developmental stages is another cause of childhood discoloration.
In children and in adults, trauma can cause a tooth to darken.
LET THERE BE WHITE
Americans are famous for the attention we pay to our teeth, and especially for our pursuit of gleaming white smiles. We are motivated whiteners. A survey found that 40% of us would be willing to give up desserts for a brighter smile! We have lots of options to choose from in our pursuit of whiteness.
Having decided to act on the desire for a white, bright smile, some people take a shot at the DIY approach. There are several homespun and traditional methods involving things like Indian oil pulling, baking soda, apple cider vinegar, activated charcoal, kaolin clay, and fruit peels. Rinsing, swishing, and brushing are the typical modes of application.
Some of these methods sometimes do produce some whitening in some people. The scientific evidence for their effectiveness is scant or absent. Most people who are serious about owning a bright smile soon realize they need a more serious strategy.
There are over-the-counter whitening products available that mimic home treatment procedures used by dentists. These kits generally include a whitening agent in gel form and a mouthpiece or strip with which the gel is applied and held on the teeth. The effectiveness of these DIY kits is limited by the strength of the whitening gel, which is weaker than that used by dentists, and by the random fit of the mouthpiece or strip to the user’s teeth.
TO THE DENTIST!
Here’s where a dentist can ride in on a white horse. Whitening is the most-requested cosmetic dental procedure, so the materials technology, equipment, and methods have advanced to meet the demand. Extrinsic discoloration, the kind resulting from coffee, red wine, and so forth, is treatable by home application of dentist-provided materials, or in the office. Intrinsic discoloration, inside the tooth, is treated only in the office.
IS THERE A DENTIST IN THE HOUSE?
When the dentist’s home treatment option is chosen, the dentist custom-fits upper and lower mouthpieces to the patient and provides a whitening gel. At home, the patient applies the gel to the mouthpieces and wears them for several hours every day.
The in-office procedure uses more powerful whitening agents, and so is more complex. The duration and number of office visits depend primarily upon the dentist’s treatment decisions, whether larger or smaller numbers of teeth are treated in each visit. A typical scenario is one to three appointments, each lasting 30 to 90 minutes.
First, the dentist makes sure the targetted teeth are as clean as possible, using a polishing paste to remove any superficial stains or bits of debris. Next, the “before” color of the polished teeth is measured, either by visual comparison with standardized color tabs or with an electronic spectrophotometer or colorimeter. This benchmark supports post-treatment evaluation of the results.
The next step is to establish protection for the patient’s gums, mouth, and face. The whitening agents used by dentists are significantly more powerful than the do-it-yourself gels sold over the counter, and can irritate or injure soft tissues they come in contact with. One tactic is to position a rubber or latex dental dam, perforated to accommodate the teeth and cover the gums. More recently, dentists have introduced the liquid dam, a neutral gel that’s applied to the gums and set with a curing lamp. Cheek retractors, gauze, cotton, a bib, and safety glasses fill out the complete set of precautions.
Whitener is then applied to the teeth selected for treatment, and allowed to do its work for 30-60 minutes. The dentist may refresh the whitener during treatment with additional applications. The treatment is completed by suctioning off the whitener and washing off the teeth.
Professional whitening is certainly the most effective way to go. That said, patients are happy with the results only if their expectations are met or exceeded, so a bit of realism is in order. The shade seen in the mirror the morning after will likely be a little darker than it was immediately after treatment, and follow-up office treatments, or at-home treatments, may be necessary to achieve peak whiteness.
Whitening, no matter how successful, does not make teeth immune to discoloration going forward so changes in consumption habits may be needed to maintain the desired shade. Coffee, red wine, and the other usual suspects will still darken teeth. A reasonable expectation, with good maintenance and prevention, is that a professional whitening will last as long as three years.