Study 1. Volunteers in study 1 will have their mouthpiece checked at the second visit, have a teeth cleaning, and have the mold put in place. The mouthpiece will be worn for up to 8 hours, during which time soft foods can be eaten. Mouthwash should not be used while the device is in place. At the volunteer's third (last) visit, the mouthpiece will be removed and the volunteer will spit into a tube to collect saliva for examination for bacteria.