Unlike a conventional filling, which is shaped directly inside the mouth, inlays and onlays are designed and fabricated outside the mouth. After removing decay, the existing restoration, and any tooth structure that is too fragile to be preserved, the tooth is recorded using an intraoral scanner. The restoration is then digitally designed and precisely manufactured in a dental laboratory or using CAD/CAM technology. Once completed, it is tried in, carefully checked, and securely bonded to the tooth using adhesive techniques.
Inlays and onlays are particularly indicated when the loss of tooth structure is too extensive to be treated predictably with a conventional filling, while enough healthy tissue remains to avoid the need for a full crown. They may be used in the presence of a large cavity, a leaking or fractured restoration, weakened cusps, or to protect certain root canal-treated teeth.
These restorations can be made from ceramic or CAD/CAM resin composite materials. Ceramics provide excellent aesthetic stability and good resistance to wear, while composite-based materials are generally more flexible and can often be adjusted or repaired more easily. There is no single material that is ideal for every patient. The choice depends on the condition of the tooth, the available space, the bite, the forces generated during chewing, and the patient’s aesthetic and functional requirements.
The main advantage of inlays and onlays is their ability to preserve more of the natural tooth structure. Compared with a full crown, they allow treatment to focus mainly on the damaged or weakened areas while maintaining the healthy tissue that is still present. They also make it possible to accurately restore the shape of the tooth, re-establish proper contact with neighbouring teeth, and protect weakened cusps from fracture. When correctly indicated, carefully performed, and regularly monitored, partial adhesive restorations provide reliable aesthetic, functional, and long-term clinical results.⁴
1. Dietschi D, Maeder M, Meyer JM, Holz J. In vitro resistance to fracture of porcelain inlays bonded to tooth. Quintessence International. 1990;21(10):823–831.
2.Didier Dietschi, Roberto Spreafico. Adhesive Metal-Free Restorations: Current Concepts in the Aesthetic Treatment of Posterior Teeth. 1997, Quintessence Publishing
3. Dietschi D, Moor L. Evaluation of the marginal and internal adaptation of different ceramic and composite inlay systems after an in vitro fatigue test. Journal of Adhesive Dentistry. 1999;1(1):41–56.
4.Dietschi D, Spreafico R. Evidence-based concepts and procedures for bonded inlays and onlays. Part III: A case series with long-term clinical results and follow-up. International Journal of Esthetic Dentistry. 2019;14(2):118–133.