What is the difference between an inlay, an onlay and a crown?
An inlay is a lab-made filling that sits inside the cusps of a back tooth. An onlay also covers one or more cusps, and a crown covers the whole visible tooth. All three are made outside the mouth from a scan or impression and then bonded or cemented. Creative Arts in Dubai does not list inlays or onlays as a treatment; when a filling is not enough, the tooth is restored with a crown.
Who treats you here Dr. Khalid Saeed Co-founder & Dentist · Dr. Kinan Bonni Dentist · Dr. Marina Antoniuk Dentist
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What are inlays and onlays?
Fillings come in two broad kinds. A direct filling, such as white composite, is placed soft into the cavity and hardened in the mouth in one visit. An indirect restoration is made outside the mouth, usually in a dental laboratory, from a scan or impression of the prepared tooth, then fixed in place at a second visit. Inlays, onlays and crowns are all indirect; they differ in how much of the tooth they cover.
- Inlay: fills a cavity in the biting surface and between the teeth, staying inside the raised points (cusps) of the tooth. It looks much like a large filling.
- Onlay: extends over one or more cusps to protect them. It is sometimes called a partial crown.
- Overlay or table-top: covers the whole biting surface but not the sides of the tooth. Terms vary, and some dentists use "onlay" for all of these.
- Crown: covers the entire visible tooth down to the gum line.
Inlays and onlays are made today mostly in ceramic, including lithium disilicate and feldspathic porcelain, or in laboratory-processed composite resin. Gold inlays and onlays are an older option that some dentists still use for back teeth. Ceramic and composite versions are bonded with adhesive, which is why the tooth surface must be kept completely dry while they are fitted.
Filling, inlay, onlay or crown: how do they compare?
General characteristics for a back tooth. Which one suits a particular tooth depends on how much sound tooth is left, where the edges of the damage are and how the teeth meet.
| Restoration | How much of the tooth it covers | How it is made | Visits | Usually considered for |
|---|---|---|---|---|
| Direct composite filling | Only the cavity | Built up and hardened in the mouth | Usually one | Small to moderate cavities with strong surrounding walls |
| Inlay | The cavity, within the cusps | Made in a lab from a scan or impression | Usually two, with a temporary in between | Larger cavities where the cusps are still strong |
| Onlay or overlay | The cavity plus one or more cusps, or the whole biting surface | Made in a lab from a scan or impression | Usually two | Weakened cusps on a tooth that still has healthy sides |
| Crown | The whole visible tooth | Made in a lab from a scan or impression | Usually two | Little sound tooth left, cracks, root-treated back teeth, or a change of shape or colour |
Some clinics mill restorations at the chair in a single visit; that is a separate choice explained in our guide to chairside versus lab-made crowns.
When might an inlay or onlay be considered?
The argument for an onlay is about keeping tooth structure. To fit a crown, the dentist reduces the tooth all the way around to make space for the material. An onlay covers only the parts that need protecting, so the healthy side walls of the tooth can be left alone. Dentists who use onlays often consider them in situations like these:
- A large old filling has failed, but the outer walls of the tooth are still thick and sound.
- One cusp is undermined or has chipped, while the rest of the tooth is strong.
- The cavity is too wide for a direct filling to rebuild the contacts and the biting surface reliably.
- The edges of the damage sit above the gum, where the surface can be kept dry for bonding.
Situations that usually work against an inlay or onlay include damage that extends deep below the gum, where bonding is unreliable; very heavy grinding; poor control of decay; and a tooth so broken down that too little remains to bond to. Whether a white composite filling would still do the job is a related question; our guide to white versus silver fillings covers direct materials, and fillings at Creative Arts explains how cavities are restored there.
When is a crown the better choice?
A partial restoration is only sensible when the remaining tooth is strong enough to carry the bite on its own walls. A crown wraps the whole tooth and holds it together, which matters in several common situations:
- Cracked teeth. When a crack runs into the tooth, covering it completely helps hold the pieces together. Our page on a cracked tooth explains how cracks are assessed.
- Root-treated back teeth. Molars and premolars that have had a root canal usually need their cusps covered. Our guide to a crown after a root canal explains why and when.
- Very little tooth left, or damage reaching below the gum, where bonding is less reliable.
- Changing shape, size or colour, or when the tooth supports a bridge.
- Replacing an existing crown that has failed.
Crowns come in several materials with different strengths and looks, explained in our guide to types of dental crowns. The general comparison between a large filling and a crown, without the partial options, is covered in crown or filling.
How long do ceramic inlays and onlays last?
The most cited summary is a 2016 systematic review and meta-analysis in the Journal of Dental Research by Morimoto and colleagues. It estimated survival of glass-ceramic and feldspathic porcelain inlays, onlays and overlays at 92–95% after five years and 91% after ten years. The most common reasons they failed were fracture or chipping of the ceramic, followed by problems with the nerve of the tooth needing root canal treatment; new decay at the edges and loss of bonding were less frequent.
Two cautions apply. These are averages from clinical studies, often carried out in university settings with careful case selection, not a promise for any one tooth. And a long life depends on what happens after fitting: cleaning between the teeth, regular check-ups, a bite that is checked and adjusted, and protection with a night guard if you grind. The same habits extend the life of a crown or a filling.
What Creative Arts offers
Inlays and onlays are not among the treatments Creative Arts lists. When a back tooth needs more than a filling here, it is usually restored with a crown made by Creative Art Dental Lab in the same building, typically in 3–5 working days. If you would like to know whether a partial restoration could suit your tooth, ask at your assessment and the dentist will explain the options and the reasoning.
What does getting an inlay or onlay usually involve?
The sequence resembles that of a crown, with less tooth removed:
- First visit. Under local anaesthetic, decay and any old filling are removed and the cavity is shaped with smooth, slightly tapered walls so the restoration can slide into place. The tooth is scanned or an impression is taken, the shade is recorded and a temporary filling protects it.
- In the laboratory. The restoration is designed to fit the cavity and the opposing teeth, then milled, pressed or layered in ceramic or composite.
- Second visit. The temporary is removed, the fit and the contacts with the neighbouring teeth are checked, and the tooth is isolated so it stays dry while the restoration is bonded. The bite is then adjusted and polished.
Some sensitivity to cold for a short time afterwards is common with any restoration. A bite that feels high, or pain that keeps building, should be checked rather than waited out.
Told a back tooth needs more than a filling? See how dental crowns are planned in Dubai, from the assessment and digital scan to a lab-made crown matched to your teeth.
Explore dental crownsWhat should you ask if an inlay or onlay is suggested?
Whichever clinic suggests a partial restoration, these questions help you understand the recommendation:
- Why is a direct filling not enough for this tooth, and why is a full crown not needed?
- Are there cracks, and how far do they run?
- Where are the edges of the damage relative to the gum, and can the tooth be kept dry for bonding?
- Which material is planned, and who makes it?
- How will the bite be checked, and do I need a night guard because I grind?
- What happens if it chips or comes loose: repair, re-bonding or a crown?
A clear answer to each one is a good sign that the choice was made for your tooth rather than by habit. For the crown route, our guide to the dental crown procedure explains each visit.