Can a cavity in a molar be treated with resin?

If the decay is small, resin fillings are used on molars too. However, when the area is large on a tooth that takes heavy biting force, or extends between teeth (proximal surfaces), indirect restorations such as inlays may be considered because of limits in bonding and reproducing shape. It is decided case by case.

When do dentists recommend an inlay?

An inlay is considered when the decay is too large to handle with a direct filling or the tooth takes heavy biting force. An inlay is made precisely outside the mouth from an impression and then bonded, which helps reproduce shape, but the tradeoff is that more tooth is removed than with a direct filling.

Is glass ionomer (GI) a low-quality material because insurance covers it?

No. GI is a covered filling material that keeps tooth removal to a minimum and releases fluoride. It is relatively less resistant to wear, so it does not suit every location, but it is a valid option where indicated, such as at the neck of the tooth.

Isn't amalgam banned because of mercury?

In Korea, amalgam is still a filling material covered by National Health Insurance. Some have raised concerns about mercury exposure and fewer clinics use it, but its use is not banned.

Is a gold inlay stronger than other materials?

Gold rarely breaks and has a long track record, but its color is noticeable, and because it is harder than natural teeth, adjusting the bite (occlusion) is important. Ceramic materials have the advantage of being tooth-colored, but their fracture characteristics vary by material. Every material has pros and cons, so the decision depends on the location and bite.

Why wasn't I told about insurance-covered materials first?

Amalgam and GI fillings, and light-cured resin for permanent teeth in children aged 12 and under, are covered. Each material has different indications and a covered material may not suit some cases, so you can ask the dentist to explain both covered and non-covered options during the consultation.

← Cavities guide

Choosing a Cavity Filling Material: How Resin, Inlays, GI, Amalgam and Crowns Are Decided

Published August 20, 2026 Updated August 20, 2026 Based on official HIRA and Ministry of Health and Welfare data and public sources

In the analysis of patient comments about Cavities, Choosing a material formed a question cluster of about 1,700 comments. The material depends on decay depth, location, biting force and remaining tooth. Covers resin, inlays, crowns, glass ionomer and amalgam, resin limits on molars, and covered materials. SOURCE Analysis of patient comments on YouTube dental content (DentStat) · public sources listed under References · Data as of June 28, 2026

Key facts

Types of material	Direct fillings (resin, GI, amalgam) and indirect restorations (inlays, crowns) ^[1]
Covered filling materials	Amalgam and glass ionomer (GI) ^[2]
Light-cured resin	Covered for cavity treatment in permanent teeth of children aged 12 and under ^[2]
Selection criteria	Decided by decay depth, location, biting force and amount of remaining tooth ^[1]
Comments analyzed	1,700 questions on choosing a material: the largest cavity theme ^[3]

What types of cavity filling materials are there?

They fall broadly into direct fillings placed on the spot (resin, glass ionomer, amalgam) and indirect restorations made outside the mouth from an impression and then bonded (inlays, crowns) [1]. Which material is used depends on the depth and location of the decay, whether the area takes biting force, and how much tooth remains [1].

Material	Method	Features	Health insurance
Amalgam	Direct filling	Metal-based filling with a long track record	Covered [2]
Glass ionomer (GI)	Direct filling	Minimal tooth removal, releases fluoride, relatively less resistant to wear	Covered [2]
Composite resin	Direct filling	Tooth-colored, little tooth removal	Covered for permanent teeth of children aged 12 and under [2]
Inlay (gold, ceramic, etc.)	Indirect restoration	Precisely made, suited to larger areas	Non-covered
Crown	Indirect restoration (full)	Covers and protects the whole tooth	Non-covered in principle

DentStat analyzed 1,700 patient comments about choosing a material on YouTube dental content. Material choice was the largest theme among cavity questions, showing demand for explanations of “why this material” [3].

Can cavities in molars and between teeth be treated with resin?

It depends on the size and location. Resin is a direct filling material that reduces tooth removal, but it shrinks in volume as it hardens (polymerization shrinkage), which limits filling a large area at once [1]. In areas that take heavy biting force or are hard to keep dry, such as the chewing surfaces of molars or between teeth (proximal surfaces), bonding and reproducing the contact with the neighboring tooth become more difficult, so indirect restorations are considered when the area is large [1]. “Can molars get resin too?” was a recurring question in the comment analysis, and the key point is that the decision differs by the size of the decay even on the same tooth [3].

When is an inlay considered?

An inlay is considered for large decay that is hard to shape with a direct filling. The tooth is prepared, an impression is taken, and the inlay is made precisely outside the mouth and bonded, which helps reproduce the shape of the chewing surface and the contact point with the neighboring tooth [1]. The tradeoff is that more tooth is removed than with a direct filling, to suit the shape of the restoration [1]. It is hard to say that either resin or an inlay is always better; the decision depends on decay depth, location, biting force and remaining tooth, and experts also differ on borderline cases [1]. The comment analysis showed much distrust along the lines of “the criteria for inlays are vague,” and checking the explanation of the evidence, such as diagnostic images and X-rays, helps with the decision [3].

Which materials are covered by health insurance?

Amalgam and glass ionomer (GI) fillings are covered, and light-cured composite resin is covered for cavity treatment in permanent teeth of children aged 12 and under [2]. GI keeps tooth removal to a minimum and releases fluoride, so it is used where indicated, such as the neck of the tooth, but it is relatively less resistant to wear and coming loose, so it may not suit areas with heavy biting force [1]. Some have raised concerns about mercury exposure from amalgam and fewer clinics use it, but it is not banned in Korea and remains on the coverage list [2]. A covered material may not suit every case, so you can ask the dentist to explain both covered and non-covered (not paid by Korea’s National Health Insurance) options during the consultation [2].

How do materials such as gold and zirconia differ?

Each material has tradeoffs in strength, wear and appearance. Gold rarely breaks and has a long track record but its color is noticeable, and with materials harder than natural teeth, adjusting the bite is important so the opposing teeth are not overloaded [1]. Zirconia and ceramic materials have the advantage of being tooth-colored, but their fracture characteristics vary by material [1]. Comments repeatedly compared materials, such as “gold is better” or “they recommended zirconia,” but the shared premise is that a simple comparison is difficult unless the location, bite and remaining tooth are the same [3].

Common myths and facts

Common myth	What the evidence shows
”Resin is always the answer and inlays are overtreatment”	Depending on size and biting force, there are indications where indirect restorations are considered [1]
“Resin is too weak for molars”	It is used on molars too when the area is small [1]
“GI is low quality because it’s an insurance material”	It is a covered material with advantages depending on location, such as minimal tooth removal and fluoride release [1][2]
“Amalgam has been banned”	It remains a covered filling material in Korea [2]
“One material is better in every case”	Each material has tradeoffs, so it depends on location, bite and size [1]

For cavity stages, treatment and health insurance in general, see the cavity guide. For dental clinics by area, see find a dentist.

Frequently asked questions

Can a cavity in a molar be treated with resin?: If the decay is small, resin fillings are used on molars too. However, when the area is large on a tooth that takes heavy biting force, or extends between teeth (proximal surfaces), indirect restorations such as inlays may be considered because of limits in bonding and reproducing shape. It is decided case by case.
When do dentists recommend an inlay?: An inlay is considered when the decay is too large to handle with a direct filling or the tooth takes heavy biting force. An inlay is made precisely outside the mouth from an impression and then bonded, which helps reproduce shape, but the tradeoff is that more tooth is removed than with a direct filling.
Is glass ionomer (GI) a low-quality material because insurance covers it?: No. GI is a covered filling material that keeps tooth removal to a minimum and releases fluoride. It is relatively less resistant to wear, so it does not suit every location, but it is a valid option where indicated, such as at the neck of the tooth.
Isn't amalgam banned because of mercury?: In Korea, amalgam is still a filling material covered by National Health Insurance. Some have raised concerns about mercury exposure and fewer clinics use it, but its use is not banned.
Is a gold inlay stronger than other materials?: Gold rarely breaks and has a long track record, but its color is noticeable, and because it is harder than natural teeth, adjusting the bite (occlusion) is important. Ceramic materials have the advantage of being tooth-colored, but their fracture characteristics vary by material. Every material has pros and cons, so the decision depends on the location and bite.
Why wasn't I told about insurance-covered materials first?: Amalgam and GI fillings, and light-cured resin for permanent teeth in children aged 12 and under, are covered. Each material has different indications and a covered material may not suit some cases, so you can ask the dentist to explain both covered and non-covered options during the consultation.

Find a dental clinic

Compare dental clinics by area and treatment in the area shortlists, or see nationwide figures in dental clinic statistics for South Korea.

References

National Health Information Portal: Dental Caries (Tooth Decay) · Korea Disease Control and Prevention Agency (KDCA)
National Health Insurance Coverage Criteria for Cavity Filling Materials (Amalgam, Glass Ionomer, Light-Cured Resin) · Ministry of Health and Welfare · National Health Insurance Service (NHIS)
Analysis of Patient Comments on YouTube Dental Content: 1,700 Cavity Comments on Choosing a Material (collected 2026-06-28) · DentStat (Osamil Inc.)

This content is general information based on public sources and does not replace diagnosis, prescription or treatment for any individual. If you have symptoms, consult a dentist.