Just been to the dentist - it got me thinking about the amazing materials they use. Rapid setting, no smell or taste. Rock hard in seconds, Good adhesion, workable.
Does anyone know what the science is behind such materials?
The stuff my dentist uses is UV cure and I'm pretty sure it does smell.
MBQ
There's a pile of vast tomes on the subject here (gf's a hygienist). Dental materials aren't especially interesting for re-use in non- dentistry. They're obsessed with non-toxicity, which rules out many better performing materials. Chances are that if dentists have something fairly good, there's a poisonous equivalent that's better and cheaper.
Usually they're UV cure, because it's one good way to avoid the toxicity of a more chemically-active material. A good dentist will cure in thin layers, lazy ones pack the whole cavity and then cook it from the top.
UV cured epoxy I think.
I have had the UV cured stuff in the past - but this repair was just applied and was hard in seconds - no application of UV.
What? Like mercury amalgam? :-)
Also fluoride content (if I understand correctly, this is an intentional addition to at least some materials) can have its own sorry set of toxic effects. :-(
I said they were obsessed with talking about it, I didn't say they'd stopped using the traditional nostrums!
They still use good old Victorian gutta percha for root canal work.
Not toxic in the way it's used correctly in dentistry though. Toothpaste is potentially fatal, if the baby chews through a tubeful of it. The main health problem with fluoride is chronic toxicity from groundwater.
I had the whole side fall off one of my molars that had been filled many years before. Went to see my dentist and he first cleaned up the bad edges, then attacked it with a micro sand blaster. Yes, that's exactly what it was, and he said it was to improve the bond between the filler and tooth. He then mixed up the epoxy stuff (white) and built the tooth back up. It took just a couple of minutes and I don't think it was UV cured. He then ground a new 'tooth-like' profile on it, and the job was done. Like 10 minutes start to finish. That was probably 3 years ago, and it still feels and looks exactly like tooth. As you said, a remarkable material to stand up to the daily rigours that one of the main chewing teeth has to.
Arfa
Asked my dentist about this a while ago. In fact I don't think the UV cure is epoxy (but it did have a very long name). I doubt if you'd consider it apart perhaps from making small models if you saw the price. We use dental silicone, either the putty or the twin tube stuff, for replicating engineering defects and that costs an arm and a leg too.
Sounds like glass ionomer cement
Owain
I'll take your word for that ! So what are the properties of this material ? Is it used a lot in dental work ? Elsewhere ? Expensive ?
Arfa
Maybe - I do not have information to hand about the relative impacts of fluoride from different sources. And I do know that in my schooldays, we were encouraged to swallow toothpaste if had been too slow at swilling before lights out, or when camping, etc. But I do have this:
Cytotoxicity of dental glass ionomers evaluated using dimethylthiazol diphenyltetrazolium and neutral red tests. Lönnroth EC, Dahl JE.
Department of Human Work Sciences, Lule a, University of Technology, Sweden. snipped-for-privacy@arb.luth.se
The purpose of this study was to assess the cytotoxicity of some commonly used glass ionomers. Three chemically cured glass ionomers (Fuji II, Lining cement, and Ketac Silver) and one light-cured (Fuji II LC) were tested. Extracts of mixed non-polymerized materials and polymerized specimens were prepared in accordance with ISO standard
10993-12. The polymerized specimens were cured and placed either directly in the medium (freshly cured), left for 24 h (aged), or aged plus ground before being placed in the medium. The cytotoxicity of extracts was evaluated on mouse fibroblasts (L, 929), using dimethylthiazol diphenyltetrazolium (MTT) and neutral red (NR) assays. Further, the concentrations of aluminum, arsenic and lead were analyzed in aqueous extracts from freshly cured and aged samples, and the fluoride levels analyzed in aqueous extracts from freshly cured samples. All extracts except that of non-polymerized Ketac Silver were rated as severely cytotoxic in both assays. Extracts of polymerized material were significantly more cytotoxic than extracts of non-polymerized material. All freshly cured glass ionomers released aluminum and fluoride concentrations far above what is considered cytotoxic (aluminum >0.2 ppm and fluoride >20 ppm). Extracts from freshly cured Lining Cement contained the highest concentrations of aluminum and fluoride (215 ppm and 112 ppm). Extracts from freshly cured Ketac Silver had the lowest concentrations of aluminum and fluoride but the highest of lead (100 ppm). It can be concluded that all extracts from non-cured, freshly cured, and aged glass ionomers contained cytotoxic levels of substances. Curing did not reduce the toxicity significantly.Not sure if formulations have changed, the research has been updated, etc. since then.
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