| Eligibility Criteria | |
|---|---|
| Inclusion Criteria | Exclusion Criteria |
| were aged between 18 to 30 years old | had dentin hypersensitivity |
| had good general and oral health | had congenital enamel defects |
| had caries-free anterior teeth | had visible cracks on enamel |
| had anterior-free restorations | had periodontal disease |
| had canines with shade A2 or darker | had a previous bleaching procedure |