Study 2. Volunteers in study 2 will have their teeth cleaned at the second visit and the tooth fittings placed onto the back teeth with a dental adhesive. The fittings will be worn for up to 72 hours, during which time volunteers can eat a regular diet and brush their teeth. Mouthwash should not be used while the fittings are in place. At the third, fourth and fifth visits, some of the fittings will be removed and, if necessary, the tooth surface will be polished. The last of the fittings will be removed at the fifth visit and the volunteer will spit into a tube to collect saliva for examination for bacteria.