Porcelain Inlays and Onlays – The Information you need to know

What is a dental inlay or onlay?

Inlays and onlays are what we call indirect restorations- this means they are made outside the mouth from an impression and then cemented or bonded into the tooth.

Contrast this with a filling that is placed directly into the mouth.

I guess they fall somewhere between a filling and a crown and tend to be used to restore pieces of missing tooth where the area is a bit large for a filling but may not yet require a crown.

These days, they are most commonly made from porcelain and then bonded to the teeth. Gold can also used very successfully and has been for many years.

An inlay as the names suggests sits inside the tooth, compared to an onlay which is bonded onto the tooth, thus replacing some or all of the biting surface; more commonly the latter.

The area of decay, chip or existing filling will largely determine the shape of the restoration though it may be modified to protect other parts of the tooth where necessary.

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Why would you need inlays or onlays? Problems they can solve

Inlays or onlays are used to restore back teeth (both premolars and molars).

Depending on circumstances, they can be used instead of a filling, instead of a crown, instead of a root canal and instead of the post and crown where the nerve is healthy, but there is no tooth structure to hold the crown.

They can be used to restore part of or all of a tooth that has been cracked, and is under heavy biting forces. It can also replace a filling that has failed, or where another piece of tooth came away or simply for a large hole or cavity in a tooth.


I’ve already explained how the onlay sits on the tooth to replace part of it and the inlay sits inside the tooth: the tooth dictates the shape and size.

So now the option is simply gold or porcelain: both are excellent materials though porcelain is used more often because of its aesthetics and its ability to actually bond to the tooth via etching the porcelain and etching the tooth and then chemically attaching the two together.

Gold is great for thin sections where strength is required, but for one reason or another the preparation can’t be extended further.

I’ve seen some excellent gold inlays last over 20 years and look as good as the day they were put in.

Porcelain restorations can be either zirconia or emax: the latter is more common as it can be bonded. Zirconia is very strong, a little less aesthetic and is cemented on like a gold inlay.

What’s the treatment procedure?

The procedure is very similar to a crown though the first appointment generally takes less time and is easier to temporize.

Assuming you have already had a consultation with Dr Jamie, the nerve has responded positively i.e. your tooth doesn’t need a root canal and the x ray is fine, both inlays and onlays will take two appointments.

The first appointment is for the preparation – here we will make you numb, remove any old filling material or dental decay and shape the area to check that there are no undercuts so the final restoration will sit in nicely.

We may shape or modify the rest of tooth to improve the retention, or reduce the height of the tooth, to allow an onlay to cover the whole biting surface for additional protection.

We will take a shade if it’s a porcelain onlay and take an impression to send to the lab.
A temporary material will be put in for the 1-2 weeks, whilst the restoration is made in our lab.
The second appointment involves making you numb again, popping off the temporary, cleaning up the tooth and then using an appropriate material to prepare and bond in the inlay or onlay to the tooth.

We use very strong adhesive cements to chemically bond the porcelain to the tooth. Gold inlays or gold onlays are cemented in slightly differently.

We clean off any excess, check the bite is right and the contact with the teeth next door is correct… so you’ll have no excuses for not flossing…then you’re all done.

What are the risks and problems with this treatment?

The risks with inlays and onlays are the same as for a crown and a filling:

This includes the onlay coming off – unlikely but it can happen: it may be due to the cement failing or excessive forces being placed on it by your bite.

Inlays, as they sit inside the teeth are less likely to come out – the restoration, or another part of the tooth could break off or fracture- not likely but it does happen if there is insufficient thickness of material to give the required strength.

As with crowns or large deep fillings, occasionally the nerve inside can play up and we may need to go through the top of the restoration to access the middle of the tooth and perform a root canal procedure…. It’s generally not necessary to replace the restoration, though on a molar tooth the treatment may need to progress to a crown… if the whole biting surface isn’t all in the same material.

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What’s the success rate/ how long do they last?

Both Inlays and onlays are regarded as long-term solutions for repairing your teeth and would be expected to last a similar number of years to a crown (10-20 years): longer than a filling would in the same situation.

The actual amount of time it lasts will depend, as I have said for most restorations, on the dentist (their experience and the quality of the preparation, impression, temporary and cementation); the technician (how well the inlay/onlay is made and the accuracy of the fit); the inlay or onlay (which material, which bonding technique); the tooth (how much tooth is there to bond too? The state of the nerve) and finally the patient (how well you look after it by brushing and flossing once it has been placed).

Alternative treatments?

The alternatives to an inlay or an onlay are a filling or a dental crown.

In general small holes and restorations in back teeth are most easily and cheaply restored with fillings, very broken down or root filled posterior teeth by crowns.

Let’s delve a little deeper… when you place a large white filling the composite material shrinks on setting and even though we do our best to minimize this effect, it sets up forces on the tooth which can, over time, cause it to fail. The bigger the filling, the more shrinkage and the more likely it is to fail.

Drum roll please…. enter the inlay/onlay – because it is made from an impression of the space and then bonded in, it sits passively in the tooth without exerting any force, and in doing so predictably restores the tooth for the long term.

Most dentists would agree that the dental crown remains the most predictable way to restore a heavily broken down tooth, though sometimes dentists are little quick (in Dr Jamie’s opinion) to jump to a crown from a moderate size filling… often an inlay or onlay can be used in these circumstances, and of course, it’s cheaper!

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What are the costs involved?

Fillings are the most economic way to restore a tooth.

Dental crowns and inlays and onlays required not only two appointments so take more chair time but have an additional lab stage, since the restoration needs to be made by a skilled dental technician- this increases the cost.

You would expect to pay not quite as much as a crown but considerably more than a filling.

The material used, be it porcelain or gold, and the dentist performing the treatment will also affect the price.

Dr Jamie prides himself providing excellent quality – Australian made restorations at a reasonable cost…head to a dentist in the city and you’d pay considerably more.

Aftercare and recovery?

You will leave the first appointment with a temporary restoration- it’s important to keep the tooth nice and clean, but be careful when flossing so as not to dislodge restoration.

Sometimes a bit of temporary sensitivity can be experienced and it will of course feel somewhat different- tongues are curious beasts.

If you experience any severe pain, please contact us right away- although this is unlikely.

You will also be numb, so just be careful not to bite your lip, nothing too hot to eat and watch eating or drinking in public until the effect has worn off… as you may end up ‘wearing’ whatever it is you are eating.

Once the final inlay/ onlay has been placed, you can treat it as a normal tooth – brushing and flossing- yes flossing!)

It will be set when you leave… so you’re good to go.

Summary Box:

Treatment time2 appointments – 1st 1 hour, 2nd 30 minutes (2 weeks later)

Have a Question?

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Alternatively if you would prefer to speak with someone directly or book an appointment, please call our lovely staff at the Maroubra Dental Centre on 02 9133 4005.

Like more information?

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Check out:

  1. Dr Jamie’s education site; Jamiethedentist.com where you can hear him speak and read about TOPIC in a lot more detail.
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