Dental inlays and onlays are indirect restorations used to repair damaged or decayed teeth when a traditional filling is not sufficient but a full dental crown may not be necessary. They are made outside the mouth and then bonded or cemented to the prepared tooth.
Medically reviewed by Dr. Walter Kostrzewski, DMD
Dr. Kostrzewski has more than two decades of experience in dentistry and reviews the dental information published by ACE Dental Resource.
The main attraction is tooth preservation: a partial-coverage restoration can restore a damaged area while leaving more sound tooth structure than many full-coverage preparations. But an inlay or onlay is not automatically more conservative or more durable in every clinical situation. The amount and location of tooth loss, remaining cusps, bite forces, caries risk and restoration material all matter.
What Is an Inlay?
An inlay fits within the prepared internal portion of a tooth and does not normally cover the cusps. It is commonly considered when damage is too extensive for a direct filling but the cusps remain sufficiently intact for partial coverage.
What Is an Onlay?
An onlay is larger and extends over one or more cusps. It can be useful when a tooth has lost enough structure that protecting a weakened cusp is part of the treatment plan.
| Restoration | Where it sits | Typical role |
|---|---|---|
| Filling | Directly placed into a prepared cavity. | Small to moderate defects that can be restored predictably with direct material. |
| Inlay | Within the tooth, between the cusps. | Selected larger defects where cusps can be preserved. |
| Onlay | Within the tooth and over one or more cusps. | Teeth with greater structural loss requiring cusp coverage. |
| Crown | Covers the prepared clinical crown. | Teeth requiring more extensive protection or restoration. |
Inlay vs. Onlay: Which One Do You Need?
The dentist decides based on the amount of healthy tooth remaining, the location of the defect, the strength of the remaining cusps and the forces placed on the tooth. The terms should not be treated as a simple size scale in which an onlay is always “better” than an inlay.
How Are Inlays and Onlays Made?
1. Examination and planning
The dentist evaluates decay, cracks, existing restorations, pulp status, periodontal health and the remaining tooth structure.
2. Tooth preparation
Decay or defective restorative material is removed and the tooth is shaped so the planned restoration can fit and function correctly.
3. Impression or digital scan
A traditional impression or digital scan records the prepared tooth. The restoration may be fabricated in a laboratory or with an in-office CAD/CAM workflow.
4. Temporary protection
If the definitive restoration cannot be placed during the same appointment, the tooth may receive a temporary restoration while the inlay or onlay is fabricated.
5. Try-in and bonding
The dentist checks the fit, contacts, appearance and bite before permanently bonding or cementing the restoration.
Modern CAD/CAM systems can shorten the laboratory stage and may allow some restorations to be designed and placed in one visit. That is a workflow difference, not proof that every same-day restoration is clinically superior.
What Materials Are Used?
Inlays and onlays may be made from ceramics, composite resin or metal such as gold. Material selection depends on the tooth, available space, functional forces, esthetic requirements, bonding strategy and the dentist’s judgment.
| Material | Potential advantages | Considerations |
|---|---|---|
| Ceramic/glass ceramic | Tooth-colored and can provide strong esthetic results. | Fracture and debonding remain possible complications. |
| Composite resin | Tooth-colored and can be useful in selected cases. | Long-term survival varies by material and clinical situation. |
| Gold | Excellent clinical track record and high durability. | Metallic appearance and laboratory cost can make it less attractive to some patients. |
How Long Do Inlays and Onlays Last?
There is no single guaranteed lifespan. A systematic review and meta-analysis found high survival for ceramic and resin inlays, onlays and overlays overall, while fractures, endodontic complications, secondary caries and debonding were among reported failures. [1]
Another systematic review found that ceramic partial-coverage restorations can have high medium- and long-term survival, but fracture was a common cause of failure and risk appeared higher in some non-vital teeth and patients with parafunctional habits. [2]
A 2022 systematic review and meta-analysis comparing ceramic and resin partial-coverage restorations found higher estimated survival for several ceramic groups at five and ten years, although the available evidence is heterogeneous and material choice should be individualized. [3]
Are Inlays and Onlays Better Than Crowns?
Not automatically. Partial-coverage restorations can preserve tooth structure when enough sound tooth remains, but a crown may be more appropriate when a tooth is extensively weakened. A 2018 systematic review found high five-year survival across inlays/onlays and crowns but also emphasized heterogeneity and complications such as caries and ceramic fracture. [4]
| Situation | Possible direction |
|---|---|
| Limited structural loss with strong cusps | A filling or inlay may be considered depending on the defect. |
| Moderate loss involving or threatening a cusp | An onlay may provide partial coverage. |
| Extensive structural loss | A crown or another restorative strategy may be considered. |
| Very deep decay or pulp involvement | Endodontic or other treatment may need to be addressed before definitive restoration. |
Does Getting an Inlay or Onlay Hurt?
The tooth is normally anesthetized during preparation. Temporary sensitivity can occur afterward, particularly if the restoration is deep. Persistent pain, sensitivity to heat/cold or pain on biting should be reported to the dentist.
Inlay and Onlay Cost
Fees vary by material, tooth, laboratory, location, complexity and whether additional treatment is required. The old fixed prices on this page are no longer appropriate as a current cost guide. Ask for a written estimate covering the examination, X-rays or scans, preparation, temporary restoration if needed, laboratory or CAD/CAM work, bonding and follow-up.
Inlays and Onlays vs. Dental Bonding
Direct composite bonding is placed and shaped in the mouth and can be useful for smaller or selected defects. Inlays and onlays are fabricated indirectly and may be selected when more extensive posterior tooth structure has been lost. The choice depends on the tooth and defect rather than a simple “stronger is better” rule. See our dental bonding guide.
Care After an Inlay or Onlay
- Brush twice daily with fluoride toothpaste.
- Clean between teeth every day.
- Limit frequent exposure to sugary or acidic foods and drinks.
- Do not use a restored tooth to bite very hard objects.
- Address grinding or clenching if your dentist identifies it as a risk.
- Attend routine examinations so recurrent decay, cracks and restoration margins can be monitored.
Questions to Ask Before Treatment
| Question | Why it matters |
|---|---|
| How much healthy tooth structure will remain? | Tooth preservation is central to choosing partial versus full coverage. |
| Why is an inlay/onlay preferable to a filling or crown in my case? | It clarifies the clinical rationale rather than relying on marketing language. |
| Which material do you recommend and why? | Materials have different esthetic and mechanical properties. |
| Can the restoration be made in one visit? | This depends on the practice’s equipment and the clinical case. |
| What happens if it fractures or comes loose? | Understanding repair and replacement options helps with long-term planning. |
Bottom Line
Inlays and onlays are useful partial-coverage restorations for selected damaged teeth. Their main advantage is the ability to restore a tooth while preserving appropriate amounts of sound structure. The best choice depends on the remaining tooth, bite, caries risk, material, restoration design and long-term maintenance—not simply on whether the restoration is marketed as “minimally invasive.”
Research and Sources
- Morimoto S, et al. Survival Rate of Resin and Ceramic Inlays, Onlays, and Overlays: A Systematic Review and Meta-analysis. Journal of Dental Research. 2016. PubMed.
- Abduo J, Sambrook JR. Longevity of ceramic onlays: A systematic review. Journal of Esthetic and Restorative Dentistry. 2018. PubMed.
- Comparative evaluation of clinical performance of ceramic and resin inlays, onlays, and overlays: A systematic review and meta-analysis. Journal of Conservative Dentistry. 2022. PubMed.
- Vagropoulou G, et al. Complications and survival rates of inlays and onlays vs complete coverage restorations: A systematic review and analysis of studies. Journal of Oral Rehabilitation. 2018. PubMed.
Editorial note: This page provides general dental information and is not a diagnosis or substitute for an examination by a dentist.