Professional Dental Whitening Guide: How It Works and What to Check Before Treatment

Professional teeth whitening is a procedure in which a high-concentration whitening agent is applied to the teeth at the dental clinic to lighten their color. Because the teeth are not cut, temporary sensitivity is common, and the effect varies with the cause of discoloration and the condition of the teeth. In Korea it is for appearance improvement, so national health insurance does not apply and the cost differs by clinic.

Published 2026-11-08 · Updated 2026-11-08 · DentalStatics editorial team

Key facts

How whitening works	Oxygen released as hydrogen peroxide or carbamide peroxide breaks down bleaches enamel and dentin (source: Ministry of Food and Drug Safety (MFDS, 식품의약품안전처))
Drug standard	Whitening agents above 3% hydrogen peroxide are drugs (source: Ministry of Food and Drug Safety (MFDS))
Types of whitening	Professional whitening, general whitening, and at-home (consumer) whitening (source: Ministry of Food and Drug Safety (MFDS))
Sensitivity after the procedure	A common temporary symptom that usually disappears within a few days (source: Korea Disease Control and Prevention Agency (KDCA, 질병관리청) National Health Information Portal)
Health insurance	Treatment for appearance improvement is not covered (source: National Health Insurance Service (NHIS, 국민건강보험공단))

How does professional whitening lighten teeth?

Hydrogen peroxide or carbamide peroxide, the main ingredients of whitening agents, release oxygen as they break down. The Ministry of Food and Drug Safety (MFDS) explains that this oxygen bleaches enamel and dentin to produce the whitening effect. KDCA material likewise treats lightening the color of the dentin inside the tooth with a chemical agent as the core of whitening.

The MFDS divides whitening into professional whitening received at a dental clinic, general whitening done at places such as dental clinics, and at-home whitening done at home. Products above 3% hydrogen peroxide are classified as drugs, so high-concentration agents are used within dental treatment.

The relationship between concentration of the active ingredient and side effects also appears in MFDS guidance. The stronger the agent, the faster the effect, but the risk of side effects also rises. So dentists protect the gums and control the time and number of applications.

What do I check before professional whitening?

If cavities or gum disease are severe, it is better to finish that treatment before whitening. If there is a sore in the mouth, irritation from the whitening agent can be strong, so it is put off until the sore has healed.

If the front teeth have resin, crowns or laminates, only the natural teeth lighten after whitening, which can cause a color difference. Planning in advance, before whitening, whether to replace such restorations later makes it easier to match the color.

The cause of discoloration is also checked. Unlike pigment staining from coffee or tobacco, discoloration from fluorosis formed during tooth development or from drugs may respond to whitening differently, so other treatments may be considered as well.

What about sensitivity and gum irritation after whitening?

The KDCA explains that temporary hypersensitivity after whitening treatment is common but mostly disappears within days. If sensitivity does not go away, or spontaneous pain occurs even when resting, you need to see the dentist again.

The MFDS advises that if sensitivity after whitening is severe, you should stop whitening and consult a dentist. Gums turning red or sore can be a sign that the agent or device does not fit well.

For the first few days after the procedure, avoiding very cold or hot food helps reduce discomfort. Ask the dental clinic that did the procedure whether you may use sensitivity toothpaste.

People who already had sensitive teeth may feel stronger sensitivity after whitening, so it is good to say so before starting. The KDCA lists causes of sensitive teeth such as incorrect brushing, gum treatment, eating acidic food, decay and tooth cracks, and if there is such a cause, managing it comes before whitening.

How do I make the whitening effect last?

There is no fixed duration for how long the whitening lasts, and it varies with eating habits and smoking. As ways to protect the color after whitening, the MFDS recommends cutting down on smoking and strongly pigmented food, and brushing right after meals.

Right after whitening, rinsing so that no whitening agent remains in the mouth and brushing with a soft toothbrush without toothpaste is recommended. Checking the color change at regular checkups makes it easier to judge when additional whitening is needed.

The speed at which whitened teeth look yellow again differs by person. Continuing to smoke or often drinking dark-colored drinks can bring staining back quickly, so before considering additional whitening, cutting down on such habits is the way to protect the effect.

What about the cost and insurance of professional whitening?

In National Health Insurance Service (NHIS) guidance, treatment for appearance improvement and removal of tooth stains are non-covered items. Therefore professional whitening for cosmetic purposes is not covered by national health insurance, and the patient pays the full cost.

The cost varies with the number of sessions, the number of teeth, and whether home whitening materials used together are included. Items and prices of non-covered care can be explained before treatment, so check the total number of sessions and conditions for extra costs in advance.

The expected number of sessions, the cost per session and whether there is a bundled price
Whether dental clinic whitening and home whitening materials are both included
How the remaining cost is handled if you stop midway because of severe sensitivity
Whether scaling or cavity treatment is needed before whitening, and its cost

Common myths and facts

Myth: The higher the concentration of the whitening agent, the better, without exception.

According to the MFDS, the stronger the agent, the faster the effect, but the possibility of side effects also grows.

Myth: If your teeth are sensitive after whitening, they are damaged.

Sensitivity after whitening is a common temporary symptom and usually disappears within a few days. If it lasts long or spontaneous pain occurs, have it checked at the dental clinic.

Myth: Whitening also lightens the color of resin or crowns.

Whitening works on natural teeth, so a color difference with existing restorations can arise; discuss whether to replace them before whitening.

Frequently asked questions

How many sessions of professional whitening are needed?

The number needed varies with the original tooth color, the cause of discoloration and the desired brightness. There is no officially set number, so at the first consultation check the expected number, the cost per session and the conditions if you stop midway.

Can I have dental whitening during pregnancy?

The MFDS advises that it is better to avoid whitening products during pregnancy. If you are breastfeeding or planning a pregnancy, tell the dentist and discuss it before setting a whitening schedule.

Can I whiten during orthodontic treatment?

The MFDS does not recommend at-home whitening products for orthodontic patients. With braces attached, the agent does not reach under the appliance and the color can be uneven, so dental whitening is also usually scheduled after orthodontic treatment ends. Discuss the whitening timing together with the orthodontic clinic.

Will teeth look lighter with scaling alone?

If tartar and staining on the tooth surface are the cause, scaling and polishing alone can make the teeth look lighter. Changing the color of the tooth itself is whitening, so the first step is to have the dentist distinguish whether it is staining or tooth color. Doing scaling before whitening also helps the agent reach the tooth surface evenly.

What should I not eat right after whitening?

Strongly pigmented foods such as coffee, black tea, wine and curry, and tobacco, can bring discoloration back, so it is better to cut down. While you have sensitivity, also avoid very cold or hot food.

References

Korean version →