Filling vs Inlay vs Onlay vs Crown: What’s the difference and which is the right one for you?

So your dentist has told you that you need some work done and you aren’t sure what it is or what your other options are. Well, for the sake of brevity, we created this infographic to give you the breakdown on the basic restorations. This infographic is also ordered by price, from least to most expensive.

Infographic: Filling vs Inlay vs Onlay vs Crown vs Implant

Now that you’re an expert, let’s compare them in a bit more detail.


The Dental Filling vs The Inlay

In theory, these two can often be used interchangeably, but inlays are typically reserved for much larger cavities. They both involve removing the existing cavity with a drill and filling that empty space, but how that space is filled is where they primarily differ. With a filling, an amalgam or composite material is used to fill the space, and it’s a much quicker process, involving only a single visit.

With an inlay, the space is filled with a single, solid piece that is usually fabricated in a lab, although they can sometimes be made in-office, and they are typically made out of a material like gold or ceramic. The inlay must be made precisely to the shape and size of the empty space, otherwise food and bacteria will enter the space, resulting in further decay. The upside to an inlay is that they do not contract to the same degree as a filling after being placed, so there is less chance of the restoration failing for that reason, or creating a gap between the filling and the surrounding tooth structure. Inlays also create a tougher and theoretically more durable surface for use when chewing, and as such, an inlay should be more reliable long term, although the data on that is mixed and inconclusive.

Aside from an inlay being more expensive than a filling, the number one reason they are very rarely seen is that dental insurance almost never covers them. The inlay will be downgraded to a filling by the insurance company (or in other words, the insurance company refuses to pay for an inlay and will only pay the price for a filling), resulting in either the dentist losing money, or the patient being given a bill. As such, inlays are typically reserved for patients without insurance, or patients that fully understand the additional cost above a filling.

Onlays vs Dental Crowns

These are your more major single-tooth restorations, reserved for larger areas of decay where a filling or inlay won’t work due to the amount of tooth structure that must be removed. The primary distinction between an onlay and an inlay is that an onlay will cover a cusp of the tooth, whereas an inlay only fills the area between the cusps. The cavity is still drilled from the tooth, and an onlay is fabricated to the exact size and shape of the space. Conversely, a crown will cover the entire biting surface of the tooth, as well as the tooth structure above the gum line.

Compared to a crown, an onlay is a less aggressive restoration when one can be performed, as less tooth structure needs to be removed in order to place the onlay. The costs are similar, but an onlay is a little cheaper than a crown. As such, an onlay is actually the preferred restoration when possible. However, the caveat here is that an onlay is more difficult to do correctly and more reliant on the skill of the dentist. The other big issue is that, similar to inlays, dental insurance less frequently covers an onlay. However, they will cover a crown, meaning that, as expected, crowns have become widely favored by dentists and patients alike.

If this sounds a lot like dental insurance companies are dictating patient care, I would agree with you.

This is not a comprehensive list of dental procedures by any means. Things like bridges, implant crowns, 3/4 crowns, dentures, and veneers are also very prevalent.