When the Federal Food and Drug Administration allowed Premier Laser Systems Inc. in Irvine, Calif., to market the first laser for hard-tissue applications last year, many in the industry hailed it as a monumental advance. Problems soon surfaced with the lifetime of the optical fiber light-delivery system, and acceptance has been slow. In addition, researchers have been refining a rival technique called micro air abrasion, which costs less than laser technology. Dentists express fewer reservations about Nd:YAG and diode lasers for treating periodontal disease. Because the laser cuts and also stops patients' bleeding, it provides dentists with a relatively bloodless surgical site, thereby increasing visibility of the surgical site and reducing the risk of transmitting blood-borne diseases. Estimates about future market penetration of lasers must consider a number of factors: ease of use, cost, reliability and patient comfort. The estimated 1 to 3 percent of the nation's dentists who use lasers also tend to be their most vocal proponents. To attract other dentists, costs will have to decrease.