Dental inlays and onlays vs. fillings and crowns: What's the difference?

You may be familiar with fillings and crowns, but an inlay or onlay can be harder to picture. If your dental provider has recommended one, you're probably wondering what it covers and why it's the right choice for your tooth. 

An inlay repairs an area inside the tooth’s chewing surface. An onlay extends over one or more of its raised points. Both restore part of a tooth, while a crown covers the visible tooth more fully. A dentist may suggest one when a tooth has too much damage for a filling but not enough to need a crown.¹ 

What you'll learn: 

• How inlays, onlays, fillings and crowns differ in coverage 

• What to ask about your provider's treatment recommendation 

• How appointments and material options may vary 

• How to care for your restoration and plan for costs 

Want help understanding your options? Schedule a dental exam with an Aspen Dental provider to discuss the tooth and the recommended repair.

What is a dental inlay or onlay? 

An inlay or onlay is a restoration made to fit a prepared area of a tooth. Unlike a traditional filling shaped directly in your mouth, it is made separately and then placed on the tooth. You may hear these called “indirect fillings.”² The terminology can sound complicated, but it describes how the repair is made. 

Inlay vs. onlay: What part of the tooth is covered? 

The raised points on the chewing surfaces of your back teeth are called cusps. An inlay stays within those points. An onlay goes further, extending onto the chewing surface to take in one or more cusps as well as the area inside the tooth.¹ 

A photo or model of the planned area can make the distinction easier to follow than the names alone, so it’s reasonable to request one. 

How do inlays and onlays compare with fillings and crowns? 

These treatments all repair teeth, but they do not cover the same areas. Here is the basic comparison:¹

• Filling: Repairs a cavity by replacing the decayed portion with filling material

• Inlay: Repairs an area between the cusps without covering them

• Onlay: Restores the damaged area and covers one or more cusps

• Crown: Fits over the tooth as a cap, providing more extensive coverage

An inlay or onlay may suit a tooth that needs more than a filling but does not need a full crown.² That is a useful starting point, not a rule you can apply by looking at a tooth yourself.

For a closer look at the other two options, read Aspen Dental's guide to dental crowns vs. fillings. 

Why might your provider recommend an inlay or onlay? 

There is no simple cutoff that makes an inlay or onlay the right choice instead of a crown. An individual assessment matters.³ Rather than focusing only on whether the cavity is “big” or “small,” ask your provider to explain the recommendation in terms of your tooth. 

Useful questions include: 

• Which parts of my tooth need repair or coverage? 

• Why would a filling or crown be less suitable? 

• What are the trade-offs between the options available to me? 

• Would any other treatment be needed first? 

You do not need to arrive knowing which restoration to choose. The goal is to leave understanding why a particular option has been recommended. 

What materials are used for inlays and onlays? 

Options include gold and tooth-colored materials such as ceramic or porcelain and dental composite.³ If appearance matters to you, ask how the proposed material will look when you smile and whether the tooth is visible. 

Material choice is also a good time to discuss cost and expectations. Your provider can tell you which options the practice offers, why one material is recommended and the factors that could affect how it performs in your case. A general durability claim is not a guarantee for your tooth. 

What happens during an inlay or onlay appointment? 

For a lab-made restoration, treatment generally involves an impression or scan followed by another appointment for placement. Some practices use computer-assisted design and manufacturing to make an indirect filling during a single visit.² Find out which process is planned before you arrange time off or transportation. 

Your appointment discussion should also cover how the tooth will be prepared, how you will be kept comfortable and whether you will need a temporary restoration between visits. Before leaving, make sure you know what you can eat and whom to contact if something feels wrong. 

How do you care for a dental inlay or onlay? 

Keep up with daily brushing, cleaning between teeth and regular dental visits. A restoration still needs ongoing care; if it feels off or leaves a bad taste, that’s a reason to call your dental provider right away.¹ 

Follow the aftercare advice for your particular restoration. It’s also worth finding out how the restoration will be checked at future visits and whether any of your chewing habits need attention. Keep those instructions somewhere you can find them rather than trying to remember every detail from the appointment. 

To discuss a recommended repair, schedule a visit with your local dental provider and ask them to walk you through the options for your tooth. 

Dental inlays and onlays vs. fillings and crowns: What's the difference? FAQs 

Can an inlay replace an old filling? 

Yes, an inlay can replace an existing filling in suitable cases.³ That does not mean every old filling needs an upgrade. Ask what problem the proposed replacement would address and why an inlay is being considered. 

Does getting an inlay or onlay hurt? 

Your provider numbs the area with local anesthesia first, as for a filling, because inlays and onlays are types of indirect fillings. If you feel anything during the procedure, say so and your provider can numb the area further.² 

Will dental insurance cover an inlay or onlay? 

Check your plan's benefits for the specific treatment and material being proposed. Ask the dental office for a written estimate and confirm your expected share with your insurer before treatment. Be clear about whether the estimate includes any additional appointments or procedures. 

Sources 

¹ Cleveland Clinic: “Restorative Dentistry.” https://my.clevelandclinic.org/health/treatments/10924-dental-restorations 

² Cleveland Clinic: “Dental Fillings.” https://my.clevelandclinic.org/health/treatments/17002-dental-fillings 

³ American College of Prosthodontists: “Inlays and Onlays.” https://www.gotoapro.org/inlays-onlays/