A dentist has filed a $5 million lawsuit against a co-author of "The Rules," saying she violated the rules when she created a Web site calling him a liar.

Dr. Larry W. Rosenthal also says in papers filed in Manhattan state Supreme Court that Ellen Fein has tried to put the bite on him for $100,000.

Fein's shakedown attempt, Rosenthal says, includes the site LyingDentist.com, which his court papers call "a forum for maliciously defaming Dr. Rosenthal and interfering with his dental practice."

"Among other things, the Web site carried a statement accusing Dr. Rosenthal of lying, which continues until this day, and incorporated defamatory statements" from BadDentist.com, a site created by another of Rosenthal's patients, the lawsuit says.

Comments on LyingDentist.com include, "Larry W. Rosenthal is a Big Fat Liar."

Rosenthal's lawyer, David Jaroslawicz, said Monday that Fein, who co-wrote the best-seller "The Rules: Time-tested Secrets for Capturing the Heart of Mr. Right," was a former patient whose claim of dissatisfaction with his client was resolved and a general release was signed by her in February 1998.

Yet, the lawsuit says, Fein barged into Rosenthal's office on Feb. 23, 2006, "and began to scream at him in front of an office filled with patients, accusing him of, among other things, ruining her life and her marriage."

With the assistance of her lawyer Ann McGrane, who is also named as a defendant, Fein "sought to extort money from the plaintiffs," court papers say.

Jaroslawicz said he believed Fein was picking on Rosenthal because he is a high-profile, successful cosmetic dentist who, court papers say, reportedly has treated Donald Trump, Bruce Springsteen, Catherine Zeta-Jones and Joan Rivers.

Fein, who was also sued under the name Feingertz, did not return a call for comment.

McGrane said she planned to file a motion to dismiss Rosenthal's lawsuit and said she was sure it would be granted. She would not comment further.

Fein's book, a 1995 best-seller co-authored with Sherrie Schneider, tells women how to play hard to get to land a husband. Her rules include: Make your date wait; always let the man do the asking; don't offer to pay; and don't set foot in public without makeup.