The primary aim of this study is to assess whether the design of the bleaching tray used in at-home bleaching treatment is directly correlated with the risk of gingival irritation. Additionally, it aims to investigate whether the design influences the likelihood of dental sensitivity and its impact on the degree of tooth whitening.

Visit 1: Study information and delivery of informed consent. Recording of the patient's medical history, general examination, and prophylaxis. Alginate impressions will be taken of the upper and lower arches for all patients who meet the inclusion criteria. The impressions will be poured into plaster, and individualized bleaching trays will be made for each patient according to the predetermined assignment ( 1mm extended or 3 mm extended bleaching tray). A positioning guide tray will be fabricated for color measurement.

Visit 2: Initial color measurement with a spectrophotometer and the positioning guide. Each patient will receive their individualized trays. Additionally, they will be given 3 syringes of bleaching agent (Opalescence 16%, Ultradent Products). Each patient will be provided with an instruction sheet and recording sheets to fill out daily during the 3-week study period. They will record if they had gingival irritation and the degree of dental sensitivity.

Visit 3: First-week bleaching review. Data collection (gingival irritation + color + sensitivity).

Visit 4: Second-week bleaching review. Data collection (gingival irritation + color + sensitivity).

Visit 5: Third-week bleaching review and end of the study. Data collection (gingival irritation + color + sensitivity).

Inclusion Criteria:

• No oral or systemic pathology
• Periodontally healthy
• No cavities
• Tooth shade of the upper and lower canines A2 or darker

Exclusion Criteria:

• Adhesive restorations or prostheses in the anterior region
• Enamel or dentin alterations
• Smoking
• Pregnant women
• Undergone prior bleaching treatment