'The Swan' Dentist -- License to Drill On the Line Over Badly Botched Grill

The dentist to the stars -- who fixed grills on "The Swan" -- may have filled her last cavity after drilling a patient for $641K worth of work, and now the Dental Board of California wants to take her license.

According to the Board's complaint, Dr. Sherri Worth did a ton of work on Ingrid Valdez who initially sought treatment in 2009 for a "gummy smile" and some discolored teeth. However, Valdez ended up getting multiple root canals, ill-fitting veneers, and bleeding gums.

The complaint even accuses Worth of performing laser surgery on Valdez without adequate training.

Valdez sued Worth in 2010 for malpractice, and won the $641,000 judgement. Even worse for Worth -- the case raised flags with the Dental Board of California ... which launched an investigation.

Worth's clients include Tommy Lee, Anna Kendrick, and Mark McGwire ... and she's confident her practice isn't in jeopardy. Worth tells us the allegations are 5 years old and the result of "professional jealousy by a competitor."

Although she lost the malpractice suit ... she says independent experts found no negligence on her part, and she's confident she'll be vindicated.