The eyes may be the window to the soul, but the mouth is the doorway to the body. And science is showing more and more just how important it is to keep that doorway clear. When bacteria take up residence, the result can be life-threatening infection, heart disease, diabetes and other problems.

And the guardians of that doorway are important indicators of health as well. A lot of physical problems are rooted in the teeth and the way they fit the mouth and each other. Many headaches, back and neck pains can be traced to teeth or jaws that are out of alignment.

The professional most likely to fix those problems is a cosmetic dentist. Cosmetic? Granted, most treatments will make a person look a lot better, but many cosmetic dentistry procedures are about much more than looks. Have you examined lately just what the dentist can do?

OUT WITH THE OLD, IN WITH THE NEW Once upon a time, Paul Patient visited Dr. Dentist and replaced nasty decay with a shiny silver mercury filling. But today Paul gets bonded restorations. Usually made of porcelain, they blend in with his teeth, and he no longer looks like a robot when he smiles.

As in other cosmetic dental procedures, there's a good medical reason for Paul to cast out the old metal fillings and replace them with new ones. Bonded porcelain "restores 85 to 90 percent of the natural strength of the tooth," says Sarasota cosmetic dentist Dr. Burr Bakke. Not so with silver mercury fillings. "They actually break teeth," Bakke says. "They expand and contract, getting up to three or four times larger when you drink or eat something hot. Then with something cold, they contract." Not only is the shape-shifting hard on the natural teeth, but the process leaves periodic gaps between the filling and the tooth, providing a snug little home for bacteria.

IMPLANT REVOLUTION Perhaps the biggest change in dentistry recently is the technology of implants. Traditionally, missing teeth have been replaced in steps, over a number of months, with surgeries. The first step (after a complete examination) places the anchor in the bone. The patient waits for about six months for the bone to grow around the anchor and hold it in place. If it isn't done in the first procedure, a second surgery is needed to attach a post to the anchor, and after several weeks, an artificial tooth is made and fitted to the post during one or several visits.

But a new program offered by Nobel Biocare is to implant technology what the microwave was to the cook. It allows the dentist to take images of the patient's jaw with a CT scan (often in the office) and use sophisticated software to pinpoint where the implant should be placed. Special equipment is used, like a hole-punch on the bone, to create a space that's exactly the right size to hold and stabilize the artificial tooth. The patient really can have "Teeth in an Hour," as the program is called, and with very little pain, since the process is suture and scalpel free.

DENTAL OFFICE OR DAY SPA? From hot towels to foot massages, the extra services (and distractions) your cosmetic dentist offers might actually make you look forward to the experience. And there's good medical reason to do so.

"We realize that sitting in the dental chair is not easy," says Dr. Francisco J. Marcano of Sarasota Center for Cosmetic Dentistry. He and his staff go many extra miles to counteract any unease patients may feel. "The more comfortable they are in the chair, the more receptive they're going to be to Novocain or any kind of procedure we do. If I need to numb you and you're apprehensive, the body releases hormones that block [the effect of the medication]." Similarly, if the body is at ease, there will be less muscular resistance to a shot as well.

The practice starts working at putting patients at ease from "hello." Juices, flavored waters, coffee and tea are available in the waiting area, where patients sit in massage chairs until appointment time. In the dental chair, they're offered paraffin hand treatments as well as neck, hand and foot massage by a certified massage therapist. Patients stay relaxed throughout procedures by listening to music of their choice on an iPod or watching a DVD.

WHITEN UP! Those whose pearly whites have dimmed a bit over the years can choose from a range of options in whitening procedures today, at a range of prices as well. From the days of Arm & Hammer and Pearl Drops, we've come a long way.

Some dentists offer whitening with custom-designed trays. Over the course of several weeks at home, the patient applies carbamide peroxide to the tray and wears it daily or nightly, sometimes twice a day, gradually whitening the teeth.

BriteSmile is one of a few companies marketing one-hour whitening procedures to dentists worldwide. It's all done in the office. In this case, hydrogen peroxide gel is applied to the teeth, which are then exposed to gas plasma blue light, and the patient walks out with teeth often many shades lighter (yellow teeth bleach better than brown, and brown bleach better than gray). Zoom is a similar product. Both have women leaving the dentist's office and heading for the lipstick counter for the brightest shade of red they've worn in years.

Porcelain veneers offer a permanent way to whiter teeth. The dentist removes a layer of enamel from the tooth (so the bonded tooth is translucent like a natural one) and bonds glass in its place. The result is a strong tooth that stays bright. It's the most expensive and the longest-lasting option.

INVISIBLE ORTHODONTIA Maybe natural selection and the human tendency to favor mates with symmetrical features explain why straight teeth have been coveted for centuries. Crude metal bands have even been found on mummies' teeth and likely were the beginnings of braces. Experts believe catgut was strung through the bands in order to close the gaps between teeth.

Fortunately orthodontics has moved well beyond animal innards, to malleable metal and now plastic devices that are barely visible and are even removable, making them especially attractive to adults.

"Teeth are dynamic. They shift, they move around some," says Dr. David C. Sundeen of Sarasota Dental Excellence, who frequently puts braces on adults. That movement can cause a crooked tooth to affect other teeth over time, making a bad bite progressively worse, creating new or larger spaces for bacteria to collect, and causing any number of new problems. And straight teeth are not only more attractive, they're also easier to clean, Sundeen says.

Enter Invisalign, nearly invisible braces. "Even when talking with someone [wearing Invisalign], a lot of people don't know they're on," says Sundeen. "But if you have a special date or a speech to give, you can take them out. They're always optional, so people have a lot more control over them. Of course, the more you wear them the faster they'll work."

First a three-dimensional model is made of the teeth. Then a series of snap-on, custom-fit aligners is made. Each is worn for about a two-week interval, with the series of appliances working to move the teeth gradually into the desired positions over six months, a year or more.

Even people who wore braces when they were younger can be candidates for adult orthodontics, Sundeen says. He cites the story of one woman who had braces as a youth. "But in her mid-30s, her teeth started to get a bit crooked. She stopped smiling openly. She waited until her 60s, and then went through it. She's 65 now," and very happy with the way her teeth look. After treatment, Sundeen's orthodontic patients typically tell him how much it has improved their self-esteem.

FACE LIFTS WITHOUT SURGERY As a person ages, normal use can cause the teeth to become ground down and therefore shorter. Facial tissue that once covered teeth no longer does. The result: wrinkles.

Cosmetic dentists have been using porcelain to add length back to those teeth, which causes the facial tissue to stretch out again and eliminate wrinkles. The face then looks longer and thinner-and often, younger.

SMILE, YOU'RE ON INTRA-ORAL CAMERA If seeing is believing, there's no doubt about the power of one new dental tool. Intra-oral cameras allow both practitioner and patient to see exactly what's going on. About the size of a Magic Marker, the camera fits easily into the patient's mouth, magnifying images as many as 60 times. It plugs into a computer's USB port, and images are projected on the monitor. It's primarily a video camera but also can freeze frames for closer study.

Many models operate as both intra- and extra-oral video and digital cameras, capable of working in extremes of light, from bright offices to dark mouths.

Dr. Christine Koval of Koval & Koval Dental Associates uses intra-oral cameras as well as lasers, digital X-rays and other state-of-the-art equipment in a practice where "the focus is on smile enhancement, with emphasis on improving the biting function."

The sophisticated equipment allows her to perform complete smile makeovers in as little as two visits; and in her hands, they are the tools of an artist. Koval also works in stained glass and photography, pastimes not too far afield of the work she does every day in the office.

"I think you have to be an artist to be a good aesthetic dentist," Koval says. "You have to visualize what the art is, what you're going to do, before taking on the task."

THE BITE MUST BE RIGHT "A lot of people think that cosmetic dentistry is just bleaching or whitening the teeth," says Marcano. "That's a misconception. It's more than aesthetics, it's function. It's having the jaws join together in the proper way."

When a person's jaws do not line up correctly, patient and dentist enter into that territory where "cosmetic" doesn't seem to apply. Pain is the motivator for patients with chronic headaches and backaches. Correcting the jaw alignment does make a person more attractive, but that merely sweetens the deal.

"We have a very specialized computer program that's accurate to within one to two microns of where the bite should be," says Bakke. That's a greatly improved precision on the former standard bite accuracy of nine microns-especially considering one millimeter is equal to 10 microns.

"What we're doing is neuromuscular dentistry," says Bakke, "using a TENS [transcutaneous electrical nerve stimulation] unit and a Myomonitor computer program." Both use electrical impulses, the TENS to relax the muscles and decrease pain and the Myomonitor to measure how well muscles respond to stimulation. This enables the dental team to realign the jaws, whether by trimming and bonding, orthodontic work or both, and alleviate aches, pains and other problems.

When the bite is off, Bakke explains, a person usually compensates by dropping the jaw down and forward, because it's more comfortable. Add bad posture, which is the norm, and the process of slouching in a chair causes your body to compensate by pulling on the muscles at the back of your head, to keep it upright, and pulling the jaw back. The result is the push-me-pull-you of muscle resistance, "and you end up with sore, unhappy muscles."

And since nobody looks great when they're in pain, there's a little bit about this "cosmetic" dentistry term that really does make sense.

HOW MUCH?

The more cosmetic dentistry veers into art, the more its costs reflect not only the materials and the time, but the skill of the professional. Prices for dental work also vary by region of the country and even by city.

Bearing that in mind, here are some general price ranges for procedures mentioned. Most are not covered by dental insurance plans, but financing is usually available.

Bonded restoration of a worn tooth: $95 to $225, depending on number of tooth surfaces to be bonded.

Fillings with tooth-colored resin: $150 to $200 for a single surface (compared to $75 to $145 for metal)

Implants: $1,200 to $3,000 per tooth for traditional surgical procedure done over the course of several months; costs can rise dramatically if bone grafting or other procedures are required. The "Teeth in an Hour" implants cost about the same, but take much less time and far less recovery.

Orthodontics: Adult, full mouth, $5,000 and up.

Reshaping: $50 and up.

Veneers: Composite resin, $250 or more per tooth; porcelain, $700 to $2,500 per tooth.

Whitening: From $300 to $500 for dentist-prepared tray and materials for home bleaching; Britesmile, Zoom and other in-office one-visit procedures, $600 and up.