Many people expect a new filling to need hours to dry, like plaster or glue. A white filling does not work that way: it is hardened with a blue light, layer by layer, and is set before you sit up. A silver amalgam filling is different again, because it hardens through a chemical reaction that keeps building strength through the first day.
White fillings are set by light, not by time
Tooth-coloured composite is a resin filled with fine glass or ceramic particles. It stays soft while the dentist shapes it, which is what makes it possible to sculpt. Once each layer is in place, a curing light shines blue light onto it, and that light starts a reaction that links the resin molecules together and turns the paste solid.
Each layer needs only seconds. In a laboratory study by Mobarak and colleagues in Operative Dentistry in 2009, a high-intensity LED curing light used for just 10 seconds produced enough setting in all four tooth-coloured materials tested. Deeper fillings are built up in several layers so the light can reach all the way through each one.
By the time the filling has been shaped, checked against your bite and polished, it is hard. You do not need to protect it while it dries. Our guide to getting a filling, step by step describes the whole appointment.
Silver fillings keep hardening through the first day
Amalgam is a mixture of metals that sets by a chemical reaction once it is mixed. It is firm when you leave, but it is not yet at full strength. In a laboratory comparison of five amalgams, Suchatlampong and colleagues found that all of them had reached about 90% or more of their seven-day strength by 24 hours, and two got there within six hours.
That is why the usual advice after an amalgam filling is to avoid hard, crunchy or sticky food on that side for the first day. Normal soft meals are fine once the numbness has gone. If you are weighing up materials, our article on whether silver amalgam fillings are safe covers the evidence.
Waiting for feeling to return matters more
For most people, the real limit after a filling is the local anaesthetic, not the filling. While your lip, cheek or tongue is numb, it is easy to bite them or burn them on a hot drink without noticing. Feeling usually returns within a few hours. Our articles on how long dental numbness lasts and when you can have coffee after a filling go into more detail, and eating after a filling covers the first day of meals.
When a set filling still does not feel right
A filling can be fully set and still need a small adjustment. The most common reason is a high spot, where your teeth meet the new filling before the rest of your bite. It is hard to judge while you are numb, and once feeling returns it can make the tooth ache when you chew. A quick visit to smooth it down usually fixes it.
Some sensitivity to cold, sweet food or biting pressure is also common for a few days, and occasionally a few weeks, especially after a deeper filling. It should gradually improve. Pain that is sharp, lingers after the trigger has gone, wakes you at night or is getting worse should be checked, as should a filling that feels rough, cracked or loose. Our guide on what to do about a broken filling explains the next steps.
Common questions
Can I chew on a white filling straight away?
The filling can take normal chewing once it has been cured. Wait until the numbness has worn off so you do not bite your cheek or tongue.
Why was I told to avoid chewing on one side for a day?
That advice usually applies to amalgam fillings, which reach most of their strength over the first 24 hours. It can also apply if other work was done at the same visit.
My bite feels uneven after the filling. Will it settle by itself?
Usually not. A high filling tends to stay high and can make the tooth sore. Let your dentist know so it can be adjusted, which normally takes only a few minutes.
If a tooth is sore or you think you may need a filling, finding it early often means a smaller repair. You can read about our general dental care or see current new-patient options on our offers page.
This article is general information only and is not a substitute for personal dental advice. Please see a dentist to discuss your own situation.
