Dentists Marc Lowenberg and Gregg Lituchy give movie stars - and the masses - reason to smile.

Actress Amanda Peet is designed for stardom: vibrant blue eyes, sculpted cheekbones, flawless complexion. Of course, nobody's perfect. While she was filming the 2000 comedy Isn't She Great with costar John Cleese, the British actor pulled her aside one day to offer a bit of career advise: "You are quite lovely,' he told me," recalls Peet, "'but, he said, 'you really need to get that tooth taken care of.'"

Indeed, Peet's otherwise perfect façade was marred by one discolored tooth. Off she went to the go-to dentists for celebrity smiles: Marc Lowenberg and Gregg Lituchy. At their Manhattan headquarters, Lowenberg quickly bleached Peet's troubled tooth and had her grinning again in no time. "Marc and Gregg are really careful and protective," says Peet, 33. "I adore them." She isn't alone. Chris Rock, Heidi Klum, Julianna Margulies and Sarah Michelle Gellar have all opened wide for them. Long before Friends, Courtney Cox was a patient. "She was auditioning for the Bruce Springsteen video 'Dancing in the Dark,'" recalls Lowenberg. "On the way to the audition, she stopped to get her teeth cleaned." (She got the part - as a concertgoer plucked from the audience to dance with the Boss.)

Lituchy, 46, and Lowenberg, 59 - both of whom are married and have two and four children respectively - are also restoring smiles to less famous faces. Many years ago, because of frequent TV and magazine appearances, they began receiving letter from people in dire need of dental work but without the necessary cash. (A full set of veneers, for example, can run up to $40,000, and most insurance won't cover cosmetic procedures.) Lowenberg and Lituchy now treat about 25 pro bono patients a year - patients like Melissa Marks, 35, whose mother wrote the dentists after seeing them on TV and described how her daughter's teeth were left in shambles from chemotherapy to battle systemic lupus. "You'd be surprised how many people cover their mouth or come off as unfriendly when they can be this warm, wonderful person," says Lituchy.

Lowenberg, who grew up in Elmont, NY, got his big break in 1972. Just one year out of New York University dental school, he began treating several members of the Rolling Stones, who were referred to him by their physician. "They used to come here en masse," says Lowenberg. "Let's just say that [working on them] was quite an experience." Word spread, and soon Iggy Pop, Bryan Ferry and Brian Eno were making appointments. Twelve years later, with a growing practice, he partnered with Brooklyn-bred Columbia dental school grad Lituchy, and in the late '80s they became pioneers in porcelain veneers, the thin covers for teeth that act in much the same way as fake fingernails. "People weren't used to seeing incredible-looking teeth all over the place," says Lituchy. As cosmetic dentistry - especially whitening and veneers - became rapidly more common, "[business] just sort of exploded for us." Also good for business: While patients are having their mouths worked on, they can watch movies or get a foot massage. There's even a new penthouse for out-of-town clients to use during their stay. Not that the hospitality hasn't been returned. "One patient was so happy with his teeth that he offered me the use of his private jet," says Lowenberg. So, did he take him up on it? "I'm going to Antigua," he says - with a smile.