Even though Nelly has a hit song about them and more and more people are wearing them, the removable  mouth jewelry known as “grills” are not merely decorative. According to Randall Rose, DDS, a dentist specializing in cosmetic dentistry and implants, grills, some of which cost as much as $10,000, cause tooth decay.

“One of the biggest things is they don’t fit the teeth accurately, and because they don’t, it  makes it easy for food and bacteria to trap in those areas,” says Rose.

Rose says improper use and care of the fronts can result in serious gum disease, cavities, decay, and other dental problems. Also, in many states, only a licensed dentist and assistants are allowed to make a dental mold or structure to be worn in the mouth.

“So, if you’ve got people going into a shop letting a jeweler or a tattoo artist, someone who does piercing, do it, my understanding is they’re practicing dentistry without a license,” Rose says.