1. Beckman Laser Institute, University of California Irvine, Irvine, CA 92697, USA
2. College of Optical Sciences, University of Arizona Tucson, Tucson, AZ 85721, USA
3. School of Dental Hygiene, West Coast University, Anaheim, CA 92617, USA
4. College of Dental Hygiene, Concorde Career College, Garden Grove, CA 92840, USA