When a filling isn't enough, but a crown is too much
Large cavities and cracked cusps can leave a tooth too compromised for composite, yet still with plenty of healthy structure worth keeping. An onlay (sometimes called a partial crown) is a custom porcelain piece, designed with CAD/CAM technology, that replaces exactly the damaged portion and bonds to the rest.
Why we like them
- Conservative: far more natural tooth preserved than a full crown
- Strong: porcelain restores the tooth's ability to take chewing load
- Precise: digitally designed and milled for a tight, long-lasting fit
- Seamless: colour-matched so it disappears into the tooth
Is your tooth an onlay candidate?
The honest test is how much sound wall remains. A tooth with one broken cusp or one large, tired filling, but otherwise strong walls, is the classic onlay case: we replace the damaged portion and keep everything healthy. A tooth that is mostly filling, cracked through, or already root-treated usually needs the full protection of a crown instead; the reasoning behind that line is laid out in our filling-or-crown guide, and your written plan will say plainly which side your tooth sits on.
What the two visits look like
At the first visit the damaged portion and any decay are removed, the tooth is shaped conservatively, and a digital impression is taken; you leave with a temporary protecting the tooth. The porcelain piece is then precision-milled and, at the second visit, bonded in place, with the bite checked and polished until it feels like nothing happened. Aftercare is the same as any bonded restoration: our aftercare guide covers the settling-in week.
How long do onlays last?
Bonded porcelain onlays routinely serve for ten to fifteen years and often longer, comparable to crowns, because porcelain takes chewing load the way enamel does. The usual failure mode isn't the porcelain; it's new decay at a neglected margin, which routine check-ups exist to catch while it's trivial. Health fund extras typically class onlays as major dental, and your written quote includes the item numbers to check your rebate first.