According to the American Academy of Cosmetic Dentistry (AACD), which has seen its membership numbers swell by more than 49 per cent in the past three years to just over 7,000, sales of teeth whitening products and services have jumped 300 per cent, while the use of veneers increased by more than 250 per cent between 1996 and 2000.

Eric Nelson of the AACD attributes the growth to technological advancement in the field of veneers, which are thin porcelain shells that are bonded to the teeth and typically last 10 to 20 years. Nelson also credits a mini-boom in dental spas that attempt to make teeth-cleaning and other services a pampering experience. "The whole idea is to make patients feel more comfortable," he says.

And, don't forget, more attractive. To achieve that, more dentists are bringing dermatologists into their practices, giving their time-pressed patients the opportunity to get a set of veneers and Botox injections under one roof. Rozenberg, who sells her jaw and neck cream at Henri Bendel in New York, administers Restylane injections herself. American Dental Association guidelines stipulate that she is allowed to perform any procedure on the face and jaw area within her scope of training and the ethics of the profession but they leave the regulation of the treatments to individual state licensing boards.

But even if the law permits dentists to give wrinkle-filling injections, should they? Jonathan Levine, the dentist behind GoSmile, a teeth-whitening product, says dentists should leave the injections to the dermatologists. "It is outside their general expertise," he says. "People need to do what they do best. A team approach is necessary."

Most dentists heed that advice. For example, last year Jeff Golub-Evans invited a dermatologist into his Manhattan office after years of referring clients to some of the city's top skin doctors. "My job is not necessarily to make the teeth better but to make the entire face look better," he says.

Of course, it can work the other way, too. David Colbert, a New York dermatologist, is in talks to bring a dentist into his pristine 11,000 sq ft office in Manhattan's Flatiron district. Colbert does a lot of work on patients who have recently had veneers on their teeth because, as he says: "What good is a perfect set of teeth if you have a crinkled chin?" Colbert recently helped a patient with porcelain veneers complete their smile rejuvenation by using Restylane to fill in the nasal-labial folds and a small amount of Botox to diminish so-called lipstick lines radiating from the patient's upper lip.

Jennifer Jablow, one of Manhattan's fastest-rising stars in the area of cosmetic dentistry, says she often shares patients with top dermatologist Neil Sadick but prefers to do her work first. "Sometimes it is best to get the teeth done first," she says, "We can build the teeth out in the back of the mouth, even a couple of millimetres could create a dramatic effect in facial contour and the broadness of the smile."

Elsewhere, there is more evidence of the convergence between cosmetic dentistry and dermatology. Christopher Orr, president of the British Academy of Cosmetic Dentistry, a two-year-old association with more than 200 members, says his London office includes a number of dental specialists plus two plastic surgeons and "someone who specialises in Botox".

Orr says his patients frequently take advantage of the convenience of having a dermatologist or plastic surgeon down the hall. "Fifty per cent of the patients who come in the door are seen by two or three practitioners," he says, adding that he also has a psychotherapist on staff.

Maybe that helps when they want to lose the frozen smile.