Inlay vs Onlay vs Crown: What's the Difference?

You've got a tooth that's too damaged for a regular filling, but it isn't falling apart either. Your dentist mentions an inlay, or maybe an onlay, or possibly a crown. And now you're sitting in the chair, wondering what the difference even is.

Here's the short version. An inlay, an onlay, and a crown all repair a damaged back tooth, and the main difference is how much of the tooth each one covers. An inlay sits inside the tooth between the raised points. An onlay covers one or more of those points. A crown covers the whole tooth. That's the heart of the inlay vs onlay vs crown question, and the rest of this guide explains how that plays out for your tooth, your budget, and how long the repair will last.

After 30+ years restoring teeth for families across Campbelltown and the wider Macarthur region, the team at Bradbury Dental Surgery has placed thousands of these. So let's walk through what each one actually does.

What's the Difference Between an Inlay, an Onlay, and a Crown?

The difference comes down to coverage. Inlays, onlays and crowns are all what dentists call indirect restorations, meaning they're custom-made outside your mouth (in a lab or with in-clinic milling) and then bonded onto the tooth. What sets them apart is how much tooth structure each one replaces.

Think of the chewing surface of a back tooth. It has raised points called cusps, with a dip in the middle.

Restoration	What it covers	Best for
Inlay	The area inside the cusps, like a custom-made filling	Decay or damage contained between the cusps
Onlay	One or more cusps plus the biting surface	Larger damage that reaches the cusps, but the tooth is still mostly sound
Crown	The entire tooth above the gum line	A tooth that's cracked, heavily decayed, or weakened

Onlays sometimes get called "partial crowns," because they sit halfway between an inlay and a full crown in terms of coverage. The more damage your tooth has, the further along that scale you go.

When Do You Need an Inlay or Onlay Instead of a Filling?

You need a dental inlay or onlay when the damage is too big for a standard filling but the tooth is too healthy to justify a crown. That's the sweet spot these restorations are made for.

A normal white filling works well for small to moderate cavities. But once the cavity gets wide or deep, a direct filling starts to struggle. It can weaken the tooth, wear faster, or leak around the edges over time. We see this a lot in patients who've had the same large filling redone two or three times over the years and want something that lasts longer.

Inlays and onlays are stronger because they're made as one solid, custom piece and bonded in. They restore more of the chewing strength of the original tooth while keeping more of your natural structure than a crown would. For background on how tooth decay progresses and why early repair matters, healthdirect has a helpful overview of tooth decay.

If your dentist has flagged a large old filling that keeps failing, our white fillings options in Campbelltown are sometimes still the right call for smaller repairs. It really depends on how much sound tooth is left.

Is an Onlay Better Than a Crown?

An onlay is often the better choice when the tooth still has enough healthy structure to support it, because it preserves more of your natural tooth. A crown is the better choice when the tooth is badly broken down and needs full coverage to stay protected.

Neither one is "better" across the board. They solve different problems.

The big advantage of an onlay is conservation. To fit a crown, a dentist has to file the whole tooth down into a smaller peg so the cap can sit over it. An onlay only replaces the damaged part. Less of your natural tooth gets removed, and in our experience, that's a real benefit, especially for younger patients who'll have that tooth for many decades.

So why are crowns still so common? Sometimes there simply isn't enough tooth left to bond an onlay to. After a root canal, for example, a tooth can become brittle and often needs the full protection a crown gives. If you're weighing up coverage after root canal therapy, our guide on what's normal after a root canal is worth a read. And when a crown is the right answer, you can learn about our dental crown service in Campbelltown.

The honest answer most of the time: the right choice depends on how many healthy teeth remain. A good dentist will lean toward the most conservative option that'll actually hold up.

What Are Inlays and Onlays Made Of?

Inlays and onlays are usually made from one of three materials: ceramic or porcelain, gold, or composite resin. Each has trade-offs in looks, strength, and cost.

Ceramic inlays and onlays are the most popular today. They match the colour of your natural teeth almost perfectly, which is why most patients choose them, especially for teeth that show when you smile. Modern ceramics are strong and bond well to the tooth.

Gold is the old workhorse. It's tough as anything and gentle on the teeth it bites against, and some dentists will tell you they'd pick gold for their own back molars. The catch is obvious: it doesn't look like a tooth. Most patients these days don't want gold on show, so it's become less common.

Composite resin is the budget-friendly option. It's tooth coloured and cheaper than ceramic, but it generally doesn't last as long. For a back tooth taking heavy chewing load, we'll often steer patients toward ceramic for the extra longevity.

How Long Do Inlays and Onlays Last?

Inlays and onlays typically last 10 to 15 years, and often much longer with good care. The research backs this up. A systematic review of ceramic onlays found survival rates of 91 to 100% in the medium term and up to 98.5% over the longer term, with the most common cause of failure being fracture of the material (published in the dental literature on PubMed). Another large review put 5-year survival for inlays, onlays and crowns all above 90%.

So they're a reliable, long-term repair. Not a quick patch.

A few things shorten that lifespan, and clinical experience really shows here. Teeth that have had a root canal (nonvital teeth) tend to fail a bit sooner. And grinding is a big one. About half the cracked and worn restorations we see at Bradbury Dental Surgery trace back to nighttime clenching and grinding that the patient didn't even know they were doing. If you grind, a nightguard isn't optional, it's what protects the investment. We cover practical fixes in our guide on how to manage teeth grinding naturally.

On cost, here's the part most overseas articles skip for Australian patients. In Australia, ceramic and porcelain inlays or onlays generally run from a few hundred dollars up to over $1,000 per tooth, with gold often landing in the $600 to $1,000 range. Your out-of-pocket cost depends on the material, how complex the repair is, and your health fund. One thing worth checking before you commit: most "extras" cover has an annual limit, and a single inlay or onlay can eat a good chunk of it. Sometimes it makes sense to split treatment across two calendar years to make the most of your rebates. Ask your fund what they'll pay before the appointment.

Which One Is Right for Your Tooth?

The right restoration depends almost entirely on how much healthy tooth is left after the decay or damage is removed. A Campbelltown dentist can only make the final call once they've cleaned out the affected area and can see what they're working with.

Here's the rough logic we use:

1. Small to moderate cavity, plenty of sound tooth left: a filling or inlay.

2. Larger damage reaching the cusps, but the tooth is still mostly solid: an onlay.

3. Cracked, heavily decayed, or post-root-canal tooth that needs full protection: a crown.

   
   

A small black spot on the surface can hide a much bigger problem underneath, and sometimes a large stain turns out to be shallow. That's why we don't promise a specific treatment before we've actually looked. Every tooth is a bit different.

If you've been told you need more than a filling and you want to understand your options, check out our dental inlays and onlays in Campbelltown. It's all part of our wider restorative dentistry care.

Not sure whether your tooth needs an inlay, an onlay, or a crown? It's worth getting a proper look before the damage spreads. We assess and place these restorations regularly at Bradbury Dental Surgery, and we can usually talk you through the best option in a single visit. Call us on (02) 4628 2151 or book online.

Frequently Asked Questions

What is the difference between an inlay and an onlay? 

An inlay fits inside the tooth, in the area between the raised cusps, much like a custom-made filling. An onlay covers more, extending over one or more cusps and the biting surface. The simplest way to remember it: an onlay covers a cusp, an inlay doesn't.

Do inlays and onlays hurt? 

The procedure itself is done under local anaesthetic, so you shouldn't feel pain during it. Some mild sensitivity for a few days afterward is normal as the tooth settles. If discomfort lasts beyond a week or gets worse, it's worth having it checked.

Are inlays and onlays worth it? 

For the right tooth, yes. They're stronger and longer lasting than large fillings, and they preserve more natural tooth than a crown. Most last well over a decade. The main trade-off is that they cost more than a filling and usually take two visits unless your clinic has same-day milling.

Is an onlay cheaper than a crown? 

Often, an onlay costs slightly less than a crown, though the two can be similar depending on the material and the tooth. The bigger consideration is usually how much healthy tooth you keep, not the price difference, since both are durable, long-term restorations.