Dental Inlays & Onlays
Durable, tooth-coloured restorations for larger cavities — between a filling and a crown.
Inlays and onlays are custom-made restorations that repair larger cavities while preserving more natural tooth than a crown.
Materials
Made from porcelain or composite for strength and a natural look.
The Restoration Between a Filling and a Crown
When decay or fracture is too large for a direct filling but the tooth does not yet need a crown, an inlay or onlay fills the gap. Both are made in a laboratory (or milled chairside) and bonded into place.
An inlay sits within the cusps. An onlay also covers one or more cusps, protecting a weakened wall. Neither requires the tooth to be reduced all round.
Why It Preserves More Tooth Than a Crown
A crown demands 1.5–2 mm of reduction on every surface. An onlay removes only what is diseased plus a defined thickness over the cusps it protects. On a heavily filled molar, that difference can be the entire remaining wall of tooth.
Because the tooth keeps more structure and the restoration bonds adhesively, the restored tooth is stronger than the same tooth prepared for a crown. See the reduction comparison.
When an Onlay Is the Right Answer
A large old amalgam filling with thin, unsupported walls. A fractured cusp. A cracked tooth where the crack stops above the pulp — the onlay binds the tooth together, exactly as a crown would, without removing the outer surfaces.
Heavily restored molars are candidates for an onlay before they split, not after. That timing is where money is genuinely saved.
Materials
Ceramic (E-max/lithium disilicate): tooth-coloured, bonds superbly to enamel, the usual choice.
Zirconia: where forces are very high, or in bruxism.
Composite: cheaper, more repairable, less durable.
Gold: unfashionable and, biomechanically, still excellent — kind to the opposing tooth and extremely long-lived.
Bonding is to enamel. If the cavity extends deep beneath the gum onto root dentine, adhesion suffers and a crown may be sounder.
What to Ask
“Can this be an onlay rather than a crown?” It is a fair question, and a good dentist welcomes it. “How much tooth will each option remove?” “Which material, and why?”
The ladder runs: filling → bonding → inlay → onlay → crown. Each step down removes more tooth, permanently.
This page provides general information and does not replace professional dental advice. Always consult a qualified dentist about your individual case.
Frequently Asked Questions
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