There's a sentence I find myself saying almost every week: "The root canal saves the tooth, but the onlay keeps it."
Patients often think that once the root canal is done, the job's finished. I wish it were that simple. Here's why there's one more step, and why it matters so much.
The bit nobody tells you
When a root-treated tooth is lost, it's usually not because the root canal didn't work. It's because the tooth broke.
By the time a tooth needs a root canal, it's normally had a tough time of it: decay, old fillings, maybe a crack or two. Some of the tooth has been lost along the way, and what's left isn't as strong as it used to be.
Your back teeth have little pointy bits on top. Every time you chew, they take the pressure. In a weakened tooth, those pointy bits can snap off, or the whole tooth can split. And unfortunately, teeth don't come with a warranty. If the crack goes too deep, the tooth has to come out, even though the root canal itself was a success.
It's a bit like fixing the engine on your car and then leaving the doors hanging off.
How we protect it
The fix is to cover the top of the tooth so it's held together and the pressure from chewing is spread out. I think of it as a strong lid for the tooth.
There are two ways to do this:
- A crown covers the whole tooth like a cap. It's the one most people have heard of, but fitting one means filing away quite a lot of healthy tooth.
- An onlay just covers the top of the tooth and the parts that need protecting. It does the same job, but you keep more of your own tooth. That's why it's now my go-to.
You might hear people use the words crown and onlay as if they're the same thing, and that's fine. What matters is that the tooth gets covered.
Does every tooth need one?
Most back teeth do, because they do the heavy lifting when you eat (steak, nuts, the occasional toffee you promised yourself you wouldn't have). Front teeth have an easier life, so a good filling is often enough. We'll look at your tooth together and work out what it needs.
All done in one visit
Here's the good news: you don't need to come back for a second appointment. Instead of messy moulds, I take a quick 3D scan of your tooth with a small camera. Our CEREC machine then makes your onlay or crown right here at the practice while you wait.
By the end of the appointment, it's fitted and you're on your way. No temporary, no second visit, and one less thing to remember.
Please don't leave it too long
After your root canal, the tooth has a temporary filling. The clue is in the name: it isn't meant to last. Until the tooth is properly covered, it's at risk of breaking. I've seen too many teeth that made it through a root canal, only to crack a few months later while waiting for their onlay. Because we can make yours in a single visit, there's no reason to wait.
What it costs
An onlay at our practice is £940. You can see our full price list on the Chalfont Dentist fees page, and you can spread the cost with 0% interest-free finance through Tabeo.
The bottom line
The root canal saves the tooth. The onlay keeps it. If you've had a root canal and haven't had the tooth covered yet, get in touch and we'll sort it out. You can also read about what having a root canal is really like.
