INCLUSION CRITERIA:  Must have all their upper and lower anterior teeth  Must have good oral hygiene  EXCLUSION CRITERIA:  Pregnancy or breastfeeding  Systemic disease  Taking NSAIDs or other drug treatment.  Periodontal disease  Enamel hypoplasia  Teeth stained by tetracycline or fluorosis  Dental malposition or orthodontic treatment with fixed appliances  Canine teeth lighter than A1  Restoration on anterior teeth  Cervical lesions  Symptoms of dental pain  Previous tooth whitening experience.