The tooth crowns that have been used for thousands of years are finally being replaced.

But for some patients, they may be difficult to find.

A study published in the journal PLOS ONE found that the popularity of the dental crown has dropped off significantly over the past decade.

Researchers analyzed the data from the US Centers for Disease Control and Prevention’s National Center for Health Statistics and Health, the largest health tracking database in the world.

They found that overall, the share of Americans who had used the crown dropped from 75 percent in 2005 to 63 percent in 2012.

The dental crown was first introduced to the US in the 19th century by dentists in England.

It has been widely used for more than 1.2 million years, including in some African cultures.

Dr. John E. Hausman, a senior scientist at the CDC, told CNN Health that the decline in use is not surprising.

“We’re seeing fewer and fewer people using the crown, but it’s not because of the disease, because people are being more careful about who they’re using the tooth crown on,” he said.

For some, the decline could be due to the increasing cost of using the devices, such as replacing a crown.

Hausman said that the number of Americans using the dental device has been on the rise for some time, but that the trend began in the 1990s.

Experts said that dentists should keep an eye on their patients’ health to ensure that the dental equipment is working properly.

“The more teeth that are being replaced, the more likely we are to see the rate of disease increase,” Hausmann said.

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