Medicine: Taking Stock of Bonding

There may be a better way to a whiter bite without drilling

“Every tooth in a man’s head is more valuable than a diamond.” So wrote Cervantes in the early 17th century. The great Spanish novelist was not being quixotic. In his day, teeth were not easily replaced. But modern visitors to dentists’ chairs in search of a gleaming grin find the artificial variety just about as dear as a diamond. Encasing even one chipped or rotted tooth in a cap can run anywhere from $300 to $600, and the process is tedious and uncomfortable. Lately, however, a less expensive alternative has been gaining popularity. Called tooth bonding, it not only costs less but is easier to do, and, enthusiasts claim, looks better when the job is done. Declares Chicago Dentist Marvin Berman: “Bonding is one of the greatest things to come along since fluoride and the high-speed drill.”

In putting on a cap, also known as a crown or jacket, the tooth is ground to a stump, then a porcelain or gold jacket prepared in the dental laboratory from a wax impression is carefully cemented on. Capping even one tooth can take three or four sittings. In bonding, there is no drilling, no anesthetic is used, and several teeth can be bonded during a single visit to the dentist. Diluted phosphoric acid is applied to the natural tooth, etching microscopic pores into the enamel. Next comes a coat of liquid plastic to seal the tooth. Then a paste composed of plastic and finely ground quartz, glass or silica is patted on in thin layers tinted to match the natural teeth and molded into the desired shape. After each layer is applied, it is exposed for up to 40 seconds to either ultraviolet or visible light beams. This triggers a reaction that hardens and bonds the layer to the underlying material. The newly built tooth is then contoured and polished.

In the past few years, some dentists have added another step: bonding a thin laminate veneer, a prefabricated plastic shield much like an artificial fingernail, to the front of the tooth. Even with a veneer, the cost per tooth is one-third to a half that of capping.

Bonding is mainly used to rebuild chipped, broken or irregularly shaped teeth, to close gaps and to improve the look of teeth permanently discolored by smoking, foods or drugs. Capping can camouflage the same conditions, but bonding can also anchor metal bridges containing replacements for missing teeth or orthodontic braces that use plastic brackets in place of metal bands. Capping is generally avoided in the case of children because the tooth is not fully formed. Bonding has no such problem. Says Berman: “Children are always falling down and breaking their teeth. Bonding is an absolute godsend.”

Bonding does, however, have a number of limitations that many dentists believe are being overlooked. Warns Martin Blitzer of New York City’s Mount Sinai: “It’s no panacea.” Unlike capping, it cannot be used on the biting surface of the back teeth, where great strength is needed to take the punishment of chewing. Nor does it produce quite as desirable a surface as capping. Dentists say it should not be used on heavy smokers or coffee drinkers because bonded teeth are slightly more susceptible to staining. Bonded teeth also may require frequent checkups, perhaps as many as four times a year, and last only five to ten years, compared with about ten to 20 years for capped teeth.

Dentists are most cautious about the new laminate veneers. Says Dr. Cornells Pameijer of Boston University: “I don’t use it. It gives the tooth a dead look.” Another concern, says Dan Nathanson of Tufts dental school in Boston, is that the shields tend to fall off: “If you have six teeth with plastic veneers, there’s a good chance you’ll lose one within a year.”

However the veneer debate is resolved, dentists report a rapid increase in bonding’s popularity. Says Ronald Goldstein of Atlanta: “My practice used to be 70% crown and bridgework and 30% bonding. Now it is the reverse.”