Denise Richards: Good Genes or Good Docs?

There's no denying that Denise Richards is drop dead gorgeous.

Here’s a 27-year-old version of the hot young actress at a anniversary party in Los Angeles back in 1998 (left) and 19 years later ... the smoke show and mother of two -- who recently celebrated her 46th birthday -- at a movie premiere in Hollywood last month (right).

Wild thing.

The question is...