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Thanks to everyone who responded. I discussed with my dentist, but we couldn't identify any gluten sources. Here are the summary of the replies I received. 

Yes, from powdered gloves. This even happened after my DH's dentist pulled her gloves off in front of me. I wasn't even the patient and I had a reaction that night. That's when I realized that the "corn starch" powder in the gloves was very contaminated corn starch. After that I asked them to use only non-powdered gloves and I never had another reaction although have had extensive dental treatment although never had a bridge held in place 

Yes, and I request GF now (they use baking soda to polish if they're out of the GF polish). You even need to be careful of dental Floss. Reach mint waxed, for example, was not GF last time I checked. 

OK, so I'm a dentist with Celiac and have investigated the materials we use. Pretty much no gluten in any of them, it's just a different set of chemistry entirely. 

I think I remember reading somewhere that a teenager had a reaction to her retainer… it took awhile to figure it out. 



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