Inlays and onlays are custom-fitted dental restorations that repair damaged back teeth when a standard filling isn’t enough but a full crown would be too aggressive. They sit in a middle ground, preserving more of your natural tooth structure than a crown while offering more strength and coverage than a filling. Dentists sometimes call them “indirect restorations” because they’re fabricated outside your mouth, then bonded into place.
How Inlays and Onlays Differ
The distinction comes down to how much of the tooth they cover. Your back teeth (molars and premolars) have raised points on their chewing surface called cusps. These cusps do most of the heavy lifting when you chew.
An inlay fits within those cusps, like a puzzle piece nestled inside the tooth. It restores the chewing surface without touching the cusps themselves. When decay or damage is confined to the grooves and valleys between the cusps, an inlay is the right fit.
An onlay extends further. It covers one or more of the cusps, wrapping over part of the tooth’s top surface. When a fracture or cavity has weakened or destroyed a cusp, an onlay rebuilds that structure while still leaving as much healthy tooth as possible intact.
When They’re Used Instead of Fillings or Crowns
Standard composite fillings work well for small to medium cavities where the surrounding tooth structure is still strong. But when the damaged area is too large for a filling to hold up under chewing forces, an inlay or onlay becomes the better option. Fillings are placed soft and hardened in your mouth, which limits how large they can reliably be. Inlays and onlays are fabricated as a solid piece and then cemented in, giving them more structural integrity for bigger repairs.
On the other end of the spectrum, a full crown covers the entire visible portion of the tooth. Getting a crown requires shaving down the tooth significantly on all sides. Inlays and onlays require less removal of tooth structure, preserving more of what’s naturally there. This is a meaningful advantage: keeping more of your own tooth means the tooth stays stronger long term, and you have more options if it ever needs additional work down the road. In cases where a crown might seem like the obvious choice, it’s worth asking your dentist whether an onlay could accomplish the same thing with less tooth removal.
Materials Used
Inlays and onlays are made from porcelain (ceramic), composite resin, or gold. Each has trade-offs.
- Porcelain/ceramic: The most popular choice for visible teeth. These can be color-matched to blend with your natural enamel and are highly resistant to staining. They’re strong but can chip under extreme force.
- Composite resin: Also tooth-colored and slightly less rigid than porcelain, which some dentists prefer because they flex more like natural tooth. They tend to cost a bit less than ceramic options.
- Gold: Extremely durable and gentle on opposing teeth. Gold restorations can last decades, but they’re visually obvious, which makes them less popular for teeth that show when you smile.
What the Procedure Looks Like
There are two ways to get an inlay or onlay: the traditional two-visit approach or a same-day option using digital milling technology.
Traditional (Two Visits)
At the first appointment, your dentist removes the decayed or damaged portion of the tooth and takes an impression. That impression goes to a dental lab, where a technician crafts the restoration from the chosen material. You’ll wear a temporary filling for one to two weeks while the lab works. At the second visit, the temporary comes out, the permanent inlay or onlay is checked for fit, and it’s bonded into place with dental cement.
Same-Day (CAD/CAM)
Some dental offices use chairside milling systems that scan your tooth digitally and carve the restoration from a ceramic block right in the office. The dentist prepares the tooth, takes a digital scan, designs the restoration on a computer, and mills it on-site. The piece is then refined, characterized to match your tooth color, and fired in a small oven to reach full strength. After that, the inner surface is etched and treated with a bonding agent, and it’s cemented onto your prepared tooth. The whole process takes a single visit, typically one to two hours.
How Long They Last
Inlays and onlays are built to be durable. A prospective study tracking composite resin inlays and onlays found a 100% success rate at 6 years, with an 85% success rate at the 9-year mark. Ceramic and gold restorations generally last even longer, with many lasting 15 to 30 years depending on the material and how well they’re maintained.
When failures do happen, the most common causes are small fractures of the tooth’s cusp, discoloration along the margins where the restoration meets the tooth, and gradual breakdown of the cement bond. Margin staining tends to come from coffee, tea, and other pigmented foods, as well as smoking. The cement layer is considered the weakest point of the restoration, and over time, tiny gaps can develop as the cement wears, letting staining and bacteria creep in.
Recovery and Aftercare
Recovery after getting an inlay or onlay is minimal. Some sensitivity to hot and cold is normal within the first 24 hours. During that window, stick to soft foods at moderate temperatures and drink mostly water. Dark beverages like coffee and tea can irritate freshly treated gums, so it helps to avoid them on the first day. Stay away from sticky, chewy, or very hard foods for at least a day or two, since these can pull on the restoration before the cement has fully bonded.
After that initial period, you can eat normally. Long-term care is straightforward: brush twice a day, floss daily, and keep up with regular dental cleanings. There’s nothing special you need to do beyond what you’d do for your natural teeth. The margins where the restoration meets the tooth are the most vulnerable area, so thorough brushing along the gumline helps prevent decay from developing at those edges.
Cost and Insurance
Inlays and onlays typically cost between $650 and $1,200 per tooth, which is comparable to the mid-range cost of a crown ($500 to $3,000). The exact price depends on the material, the size of the restoration, and where you live. Most dental insurance plans categorize inlays and onlays as major restorative work and cover up to 50% of the cost, similar to how they handle crowns. Check your specific plan, since coverage varies and some plans have waiting periods for major restorations.