Cavity and Root Canal Treatment Guide: Treatment by Stage, Resin and Sealant Health Insurance, and Root Canal Duration

A cavity is a disease in which acid produced when oral bacteria break down sugar dissolves the tooth, and treatment varies with how deep it has gone. In the early stage fluoride slows its progress; once a hole forms it is filled with resin or an inlay; and if the nerve is infected, a crown is placed after root canal treatment. In Korea, resin fillings for permanent teeth up to age 12 and sealants on large molars up to age 18 are covered by health insurance, and root canal treatment often takes 3 to 4 or more visits at intervals averaging 3 to 7 days.

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

Key facts

Resin filling health insurance	Permanent-tooth cavities up to age 12, 30% copay (outpatient clinic level), in effect since January 2019 (source: Ministry of Health and Welfare (보건복지부))
Expanded resin coverage age	Expansion from the current 12 to 13 approved (September 2026 Health Insurance Policy Deliberation Committee) (source: Ministry of Health and Welfare (보건복지부))
Sealants (pit and fissure sealing)	Cavity-free first and second large molars up to age 18, 10% copay (source: National Health Insurance Service (NHIS, 국민건강보험공단))
Topical fluoride application	Uninsured, as it is for cavity prevention (source: National Health Insurance Service (NHIS, 국민건강보험공단))
Root canal treatment visits	3 to 4 or more visits at intervals averaging 3 to 7 days, ranging from finishing the same day to several months (source: Korea Disease Control and Prevention Agency (KDCA, 질병관리청) National Health Information Portal)
Root canal treatment success rate	Reported at 60 to 90%, with a 10-year success rate of about 70 to 80% (source: Korea Disease Control and Prevention Agency (KDCA, 질병관리청) National Health Information Portal)
Regular checkup interval	Once a year if there is no oral disease; every 6 months if you have recently had treatment (source: Korea Disease Control and Prevention Agency (KDCA, 질병관리청) National Health Information Portal)

Why do cavities form and how do they progress?

A cavity occurs when plaque, a mass of bacteria clinging to the tooth surface, breaks down sugar in food and produces acid that gradually dissolves the tooth surface. If you eat sweet foods often or your mouth is dry from reduced saliva, acid lingers longer and cavities form more easily.

A cavity starts in the outer enamel, passes through the inner dentin, and burrows to the pulp where the nerve and blood vessels are. Even if the visible hole is small, it often spreads widely inside, so it is hard to be reassured just because it does not hurt.

Enamel cavity: white or brown spots, usually no pain
Dentin cavity: sensitivity to cold and sweets, a hole forms
Progression to the pulp: spontaneous throbbing, pain worse at night
Inflammation at the root tip: pus in the gums, pain on biting, facial swelling

What treatment is done at each stage?

An early cavity before a hole forms can be monitored while slowing its progress with fluoride application and better tooth brushing. The KDCA National Health Information Portal explains that fluoride application is done not only for prevention but also to stop the progress of cavities that have already formed.

Once a hole forms, the decayed part is ground away and filled immediately with a material such as resin, amalgam or glass ionomer, or, if the extent is large, restored with an inlay made from an impression. If the nerve is infected, root canal treatment is done, and a heavily weakened tooth is wrapped in a crown. If the tooth has collapsed too far to be saved, an implant or bridge is considered after extraction.

Even for a cavity of the same size, the suitable material differs depending on whether it is a front tooth or a molar, how much chewing force it bears, and how high the risk of new decay is. The National Health Information Portal explains that the depth and position of the cavity, the likelihood of recurrence and diet are considered together when choosing a filling material, so it is best to hear the pros and cons of each material together with whether health insurance applies before deciding.

Is resin treatment covered by health insurance?

From January 2019, the Ministry of Health and Welfare applied health insurance to light-cured composite resin fillings for permanent-tooth cavities in children up to age 12, with a 30% copay at the outpatient clinic level. The National Health Insurance Service states that baby teeth are not eligible and that treatment for wear, erosion, fracture and cosmetic purposes is also excluded.

In its briefing on the September 2026 Health Insurance Policy Deliberation Committee results, the Ministry of Health and Welfare said it would widen the composite resin benefit by one year, from the current 12 to 13. For other ages, resin fillings are uninsured and costs differ by dental clinic, so it is best to confirm the cost before treatment.

When is root canal treatment done and how long does it take?

The National Health Information Portal advises that root canal treatment may be needed when cold or hot things touch the tooth, when the tooth hurts severely even at rest, or when pus frequently forms in the gums. If an infected pulp is left alone, inflammation spreads through the root tip to the surrounding bone and the tooth may eventually have to be extracted.

Root canal treatment removes the infected pulp, cleans and disinfects the root canals, and fills them with a sealing material, and proceeds in 3 to 4 or more visits at intervals averaging 3 to 7 days. Depending on the case, it may finish in one day or take several months. A molar that has completed treatment or a heavily ground tooth is wrapped in a crown so that it does not break.

What if root canal treatment does not work well?

The National Health Information Portal gives the root canal success rate as 60 to 90% and the 10-year success rate as about 70 to 80%. It also explains that Koreans' lower second molars often have complex C-shaped root canals, so the success rate is lower.

If inflammation returns in a treated tooth, retreatment, in which the existing filling material is removed and the tooth is disinfected again, is considered first. If the root-tip inflammation still does not heal, apicoectomy, in which the gum is opened and the root tip is cut off, or intentional replantation, in which the tooth is briefly extracted, treated and replanted, is considered.

What should you do to prevent cavities?

The National Health Information Portal recommends brushing with fluoride toothpaste at least twice a day, and always brushing before bed. It is best to use toothpaste with 1,000 ppm or more fluoride for adults, clean between the teeth with floss, and reduce both the amount and frequency of sugary snacks and drinks.

For children, sealants that fill the deep grooves on the chewing surfaces of molars and fluoride application at the dentist help. Sealants on cavity-free first and second large molars up to age 18 are covered by health insurance with a 10% copay. For regular checkups, you are advised to go once a year if there is no oral disease, and every 6 months if you have recently had treatment.

Can cavities form again in a treated tooth?

Restorations such as resin, inlays and crowns do not decay themselves, but new decay can form at the margin where the restoration meets the tooth. This is called secondary decay, and the National Health Information Portal explains that problems such as fracture or secondary decay can occur when resin has been used for a long time.

Secondary decay progresses hidden under the restoration and is hard to see from the outside. The more treated teeth you have, the more you should take care to brush and floss the margin areas and to have them checked on X-rays at regular checkups, which is the way to reduce the scope of retreatment.

Detailed guides

Frequently asked questions

Can I put off cavity treatment if it does not hurt?

Cavities at the enamel and the start of the dentin often do not hurt, so pain is not a reliable way to know how far they have progressed. By the time it starts to hurt, it has often progressed close to the nerve, so if a checkup finds a cavity, treating it while small removes less tooth.

Does health insurance cover resin treatment for adults too?

Insurance for light-cured composite resin fillings covers permanent-tooth cavities in children up to age 12, and a plan to widen it to 13 has been approved. For other ages it is uninsured and costs differ by dental clinic, and depending on position and size you may choose a covered material such as amalgam.

How many visits does root canal treatment take?

The National Health Information Portal says it proceeds in 3 to 4 or more visits at intervals averaging 3 to 7 days. Depending on the degree of inflammation and root canal shape, it can finish in one visit or take several months, and the time to place the crown is added separately.

The temporary filling came out during root canal treatment.

If the temporary sealing material of a tooth under treatment comes out, saliva and bacteria can enter the root canal, so tell the dentist as soon as possible. Until then, do not chew on that tooth or touch it with your tongue or hands.

If I have a sealant, will I not get cavities?

A sealant blocks the deep grooves on the chewing surface of molars and reduces cavities there, but it does not prevent cavities between teeth or near the gums. Sealants can also come off, so have its condition checked at regular checkups and keep brushing and flossing.

How do I find out the cost of cavity treatment?

For covered materials such as amalgam, the copay is calculated from the fixed fee, while for uninsured treatments such as adult resin or inlays, prices differ by dental clinic. You can look up uninsured medical fees by institution on the HIRA website and the Geongang-eum app.

References

Korean version →