According to the Telegraph, they may soon become obsolete.
Researchers at King's College London found that the drug Tideglusib stimulates the stem cells contained in the pulp of teeth so that they generate new dentine – the mineralised material under the enamel.
Teeth already have the capability of regenerating dentine if the pulp inside the tooth becomes exposed through a trauma or infection, but can only naturally make a very thin layer, and not enough to fill the deep cavities caused by tooth decay.
But Tideglusib switches off an enzyme called GSK-3 which prevents dentine from carrying on forming.
Scientists showed it is possible to soak a small biodegradable sponge with the drug and insert it into a cavity, where it triggers the growth of dentine and repairs the damage within six weeks.
The tiny sponges are made out of collagen so they melt away over time, leaving only the repaired tooth.
. . .
The procedure has so far only been used in mouse teeth, but it was shown to 'fill the whole injury site'.
And Tideglusib has already been shown to be safe in clinical trials of patients with Alzheimer's disease so scientists say that the treatment could be fast-tracked into dental practices.
There's more at the link.
This is fascinating. I don't know how they plan to replace the outer layer of enamel over the dentine (another type of relatively painless filling or coating, perhaps?), but if the present system of fillings can be replaced by something more permanent, it'll be a real blessing. I've had several old fillings that started to leak, undetectably, thereby worsening the damage to the tooth until there was no alternative but to crown it. This looks like it might do away with that problem.