PITTSBURGH (KDKA) — Invisalign, a clear removable device without ceramic brackets or wires, was approved by the Food and Drug administration in 1998.

Now the FDA is sending a warning letter to the company it needs to be more forthcoming with problems.

Carnegie Mellon University professor Adrian Perrig wanted braces, but not a mouth full of metal.

“I teach and I also give many talks. From time to time it’s just convenient to pop out and being able to speak without having anything in your mouth,” he says.

He went for Invisalign, a clear version of braces for his teeth.

“Pop right in,” he demonstrates.

The transparency was appealing. “Many people don’t even notice that I was wearing them,” he remarks.

He has done quite well, but a handful of patients haven’t.

Swollen, sore lips, mouth ulcers and a burning tongue which is a rare allergic reaction requiring hospitalization.

“I haven’t had one patient that has complained of that specific sensation,” says Squirrel Hill orthodontist Dr. Sean Sherman. “In speaking with my territory manager, he has heard of a couple of patients that it did happen to and they had to terminate treatment within the first or second aligner.”

The FDA has sent a letter to Align Technology, warning the manufacturer it failed to comply with reporting requirements for medical devices that cause injury or death. The company could be fined or have assets seized. Align Technology reported $312 million in sales last year.

“We have similar things come up in orthodontics often that we have to warn the patients of. This may be a new one,” says Dr. Sherman.

It would need more investigation, but Dr. Sherman wonders if people who use bleaching agents in the aligners might be a subset at risk for this complication. Using the alingers to bleach teeth is not what they were designed for and is not recommended.