What is an onlay?
Onlays are restorations that protect your teeth from fracturing. They are used on molar teeth that are either cracked, heavily broken down or ones that have had root canal treatments.
Onlays do the job that crowns used to do but with much less drilling of your tooth which preserves tooth structure and reducing the risk of further problems with your teeth.
Onlays have become more popular recently and require dentists to have a good understanding of modern techniques to be made effectively.
Key facts about onlays
If your teeth are cracked, root-filled or have large cavities or fillings, they are at risk of fracturing and needing removal.
Onlays prevent this by covering the biting surfaces of your teeth and holding them together.
An onlay requires 2 appointments: a preparation one and then 1 to fit the only usually 2 weeks later. Some clinics that have in house milling machines or labs may be able to do this on the same day.
Onlays last around 12-15 years if they are done and looked after well.
Teeth that are recommended to have onlays are usually compromised and there is always going to be an increased risk of these teeth needing root canal treatments in the future, whether the onlay is done or not. If that is the case, the onlay may need to be replaced for a new one.
A molar tooth with a large filling where the wall has broken
The same tooth restored with a porcelain onlay
What’s the difference between an onlay and a crown?
A dental crown wraps around the entire tooth, whereas an onlay only covers the biting surface of your tooth and any areas of the tooth that are weak or broken. Onlays are only used for back teeth (premolars and molars).
The choice between having a crown or an onlay will be made by your dentist, they both do the same thing (protect your teeth from fracturing in the long run) but an onlay requires much less drilling of your teeth. Your dentist will advise on the best option based on the status of the tooth and their own skill and comfort levels.
It is our opinion that most of the time if a tooth doesn’t have a crown already an onlay will usually always be a better option.
What’s involved in the treatment?
In most dental practices, an onlay will require 2 appointments. Some clinics have access to on-site labs or milling machines and can make the onlay on the same day.
Appointment 1 - Preparation of the tooth
Your dentist will:
Provide you with local anaesthetic to make sure your tooth is numb
Remove the existing fillings in your teeth
Prepare the tooth for the onlay, this means drilling the tooth to the right height and shape for the onlay
Take an impression, or a digital scan of your tooth to send to the lab
Place a temporary onlay on the tooth, either sculpted by hand or by using a mould taken at the start of the appointment
The temporary onlay will make sure you don’t experience too much discomfort in between your appointments. Your dentist will advise you about any specific measures you need to take to look after the temporary onlay depending on the material they have used.
Appointment 2 - Fitting the onlay
Your dentist will:
Numb the tooth
Remove the temporary onlay
Check the fit of the onlay and adjust it as required
Glue the onlay into place
Polish away any sharp areas on the onlay
Adjust the onlay to make sure you are biting on the tooth properly
Teeth with large silver fillings and cracks
Teeth prepared for onlays
Teeth with porcelain onlays fitted
Aftercare and maintenance of onlays
Immediately after the treatment
There may be some discomfort around the tooth due to the nature of the work, slight sensitivity and aching is common for a few days after having an onlay fitted as the tooth underneath settles. If this ache gets worse or the sensitivity is still there after 1 week, contact your dentist who may need to check that the onlay is fitted properly.
Cleaning the onlay
It is important that you take good care in cleaning your onlay, normal brushing alongside flossing and interdental brushing is extremely important to stop bacteria getting trapped at the edges of the onlay and causing decay.
Routine check-ups
Your dentist will inspect the onlay every year during your routine checkups and will take x-rays regularly to make sure there is no decay starting around the edges of the onlay.
Chat with our dentists for free
If you want to speak to one of our dentist about onlays or anything else, press the button below to start a free online consultation.
More articles about Onlays
Root-filled teeth are at a high risk of cracking in half. This short post will explain why and what you need to do to protect your tooth.