Types of staining, and why the difference matters
- Extrinsic stain
- Extrinsic stain sits on the outside of the tooth and comes from coffee, tea, red wine and tobacco. A cleaning at a hygiene appointment removes much of it, so a brown film along the gum line may not need whitening at all.
- Intrinsic stain
- Intrinsic stain is color within the dentine, under the enamel. Enamel thins with age and the yellower layer beneath begins to show through, and old trauma and some medications can change the color from within. Peroxide reaches this layer gradually.
- Tetracycline banding
- These are gray, blue or brown bands laid down when the antibiotic was taken while the teeth were still developing. The pattern responds poorly to whitening. Months of nightly trays lighten some cases slightly, and many respond better to veneers.
- One dark tooth
- A tooth that darkened after an injury or root canal therapy is discolored from the inside, so gel on the outside does little. Internal bleaching suits some root treated teeth, and otherwise a veneer on that tooth is the usual recommendation.
How professional whitening works
Every effective product contains hydrogen peroxide, or carbamide peroxide, which breaks down into it. The molecule passes through enamel into dentine, where it breaks large pigmented molecules into smaller ones that reflect more light. Nothing is painted on and nothing is stripped away.
The amount of change depends on concentration multiplied by contact time. In-office gel is strong and used in short timed cycles with the gums protected. Take-home gel is weaker and worn for much longer. Custom trays hold it against the enamel and keep it off the gum, where it would cause irritation.
Whitening lightens teeth without making them uniform. White spots often look more obvious partway through, a translucent biting edge stays translucent, and every tooth has its own limit that no one can predict in advance. Recording the starting shade helps, because a gradual change is difficult to judge from memory.
In-office whitening or custom take-home trays
Both use peroxide and both are effective. They differ in strength, in how quickly the result appears, and in how much of the process you manage yourself.
| Consideration | In-office session | Custom take-home trays |
|---|---|---|
| How it is done | Strong gel applied in the chair with the gums protected | Weaker gel in trays made from impressions of your teeth, worn daily |
| Time to a result | Visible change the same day | The result builds over a couple of weeks, longer for resistant stain |
| Sensitivity | More likely to be pronounced, and it usually settles in a day or two | Milder, and easier to control by spacing the sessions |
| Touch-ups | Another appointment each time | You keep the trays, so a night or two maintains the shade |
Strips, charcoal and whitening toothpaste
Some of these products are effective, some have no effect, and some cause harm.
- Whitening strips contain genuine peroxide and do lighten teeth, at lower cost. The strip is a single shape, so coverage can be uneven on crowded or rotated teeth.
- Whitening toothpaste works by abrasion. It lifts surface stain and does not change the color inside the tooth, and the more abrasive formulations can wear exposed root surfaces.
- Charcoal powders, lemon juice and vinegar. Charcoal is abrasive, and there is no good evidence that it alters the color inside a tooth. Acid can make teeth look briefly lighter by frosting the surface, and it dissolves enamel, which doesn't grow back.
- Whitening at a kiosk or salon. Whitening without a dental examination first means nothing has been checked for decay, cracks or gum problems, and peroxide reaching any of those can be uncomfortable.
Sensitivity, safety and maintaining the result
Peroxide passes through enamel and dentine and briefly irritates the nerve inside the tooth. People feel that as sharp cold sensitivity, or as short twinges with no obvious trigger. The sensation is usually temporary and stops when treatment stops.
The sensitivity can be managed. Potassium nitrate gel in the tray calms the nerve, fluoride blocks the microscopic tubules in dentine, and shortening or spacing the sessions works without compromising the end result. If it becomes painful, stop treatment and give us a call.
An examination beforehand is important. Whitening won't repair a cracked tooth, and gel reaching an untreated cavity can be very uncomfortable. Afterward the color drifts back gradually, faster with coffee or red wine, so many tray users repeat a night or two of treatment every few months.
Common questions about teeth whitening
How white will my teeth become?
There's no way to predict it precisely. Yellow-toned teeth generally respond better than gray ones, and evenly colored teeth respond better than banded ones. An examination gives you a realistic idea of the range to expect.
How much does teeth whitening cost?
It depends on the method and on whether new trays are made. Call (559) 683-4694 and ask, or bring it up at your examination. Whitening is cosmetic, so it is usually not a benefit under a dental plan. See insurance.
Is whitening safe for enamel?
Peroxide whitening has been in routine dental use for decades, and used as directed under supervision, the effect people usually notice is temporary sensitivity. Problems tend to trace back to overuse, acidic home remedies or abrasive powders.
Will it work on my crown or my white filling?
Crowns and fillings keep the shade they were made in, so whitening won't change them. If a restoration on a front tooth no longer matches, we whiten the natural teeth first, then replace that restoration to the new shade. See porcelain crowns.