Madonna just turned 55 ... but she definitely doesn't act like most 55-year-olds we know.

The singer visited her Hard Candy fitness center in Rome on Wednesday, where her smile reflected camera flashes -- all thanks to her ridiculous grill!

This isn't the first time we've seen her black and gold mouthpiece, as she Instagrammed a photo of it back in July, but she hasn't worn it too much in public yet.

It's not exactly the most flattering grill we've ever seen though. The black almost makes it look like she has bad gums. Eek!

The Queen of Pop isn't the only one to bling out her teeth though -- check out the gallery above to see Rihanna's gun grill, plus Lady Gaga and more.

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