Aim of The Study This study aims is to evaluate color change, dentin hypersensitivity and patient satisfaction after different bleaching techniques at different time intervals.

Materials(subjects)& Methods

• Chemically activated bleaching kit.
• Light activated bleaching kit. This will be a randomized single-blind clinical trial, patients attending the faculty. Thirty-two patients will be selected for the study. Oral hygiene steps will be taken at the first visit, as well as scaling and polishing of the teeth. Patients will be divided into two groups according to the bleaching technique used. Group 1: chemical bleaching, Group 2: light activated bleaching.

Color change measurements:

Tooth color measurements will be performed at baseline T0, immediately after bleaching treatment T1, 1-week T2 and 1-month T3 after bleaching using a spectrophotometer. The whiteness index will be also calculated to verify the perceived bleaching effect.

Dentin hypersensitivity will be evaluated at baseline D0, immediately after bleaching treatment D1, 1 week (D2) and 3 month (D3) after bleaching using Visual Analogue Scale VAS numbered from 0 (no pain) to 10 (maximum extreme pain).

At the end of the study (3 months) a questionnaire was given to the patients to assess their satisfaction with bleaching treatment.

patients attending the faculty clinic will be screened and selected for the study according to the following inclusion criteria and exclusion criteria, inclusion criteria;

• Patients must be between 18 and 45 years old to avoid hypersensitivity resulting from the immature pulp in young populations, or the apparent yellowish color of dentin resulting from enamel wear in older populations.
• Presence of six sound maxillary anterior teeth.
• Patient having brown or yellowish stains.
• Good oral health maintained by routine brushing.
• Generalized tooth staining ranging from A2 or darker according to the value-oriented shade guide (Vita easy shade).
• Patient is willing to sign a consent form and can attend all recall visits.

Exclusion criteria:

• Existing anterior crowns or any restorations on anterior teeth that will interfere with the bleaching process.
• Smoker or alcoholic patient.
• Patients suffering from active periodontal diseases and exposed roots.
• Patient who undergone previous whitening procedure.
• Pregnant and lactating women. Thirty-two patients will be selected for the study. Oral hygiene steps will be taken at the first visit, as well as scaling and polishing of the teeth. Patients will be divided into two groups according to the bleaching technique used. Group 1: chemical bleaching, Group 2: light activated bleaching.

Bleaching techniques:

• Chemically activated bleaching: the patient's lips will be covered in Vaseline for protection, a cheek retractor is used to pull the lips and cheeks away from the teeth to shield them from the bleaching gel and to prevent gel leakage, the gingiva is properly dried, and a gingival protector liquid dam is added to all exposed gingiva and cured according to the manufacturer's instructions. Bleaching gel is uniformly added to the teeth and bleaching procedure will be conducted according to the manufacturer's instructions in one session for 20 min.
• Light activated bleaching: same protection protocol is used in addition to protective eye wear for both patient and operator. Bleaching gel is uniformly added to the teeth and light bleaching procedure will be conducted according to the manufacturer's instructions in one session for 20 min.

Color change measurements:

Tooth color measurements will be performed at baseline T0, immediately after bleaching treatment T1, 1-week T2 and 1-month T3 after bleaching using a spectrophotometer. The measured values will be recorded in the units of CIELab color space. CIE L* parameter shows the degree of lightness, a* is indicative of redness/greenness, and b* indicates yellowness/blueness. Variations in L*, a*, and b* axes and chromatic alteration will be performed at each period and compared to baseline using the following calculation: ΔE* = [(ΔL*)2 + (Δa*)2 + (Δb*)2]1/2.

Whiteness index (WID):

The whiteness index will be also calculated to verify the perceived bleaching effect. The WID is a simple linear formulation that uses the CIELab chromatic coordinate values, in which the higher the values obtained, the greater the bleaching effect provided by a given procedure. WID will be calculated using the following formula: WID = (0.511 × L ∗) - (2.324 × a ∗) - (1.100 × b ∗).

Evaluation of postoperative dentin hypersensitivity:

Dentin hypersensitivity will be evaluated at baseline D0, immediately after bleaching treatment D1, 1 week (D2) and 3 month (D3) after bleaching using Visual Analogue Scale VAS numbered from 0 (no pain) to 10 (maximum extreme pain).

Evaluation of patient satisfaction:

At the end of the study (3 months) a questionnaire was given to the patients to assess their satisfaction with bleaching treatment. Multi-item measure of satisfaction will be used to evaluate patients' perceptions of importance and performance of four characteristics of a bleaching treatment; final tooth color, color stability, length of treatment and comfort during treatment. Patients will be asked to rate the perceived importance of each characteristic on a 7-point Likert scale anchored by 1='Not at all important' and 7='Very important'. The perceived performance of each characteristic will be assessed on a scale anchored by 1='Very bad' and 7='Excellent'. Difference between performance and importance scores of individual service characteristics will be then calculated to form a third variable, the gap score, which will be used as an indicator of patient satisfaction. Also, the overall satisfaction of patients with the bleaching service will be measured separately on a 7-point scale anchored by 1='Not at all satisfied' and 7='Very satisfied'.

Inclusion Criteria:

• Presence of six sound maxillary anterior teeth.
• Patient having brown or yellowish stains.
• Good oral health maintained by routine brushing.
• Generalized tooth staining ranging from A2 or darker according to the value-oriented shade guide (Vita easy shade).
• Patient is willing to sign a consent form and can attend all recall visits.

Exclusion Criteria:

• Existing anterior crowns or any restorations on anterior teeth that will interfere with the bleaching process.
• Smoker or alcoholic patient.
• Patients suffering from active periodontal diseases and exposed roots.
• Patient who undergone previous whitening procedure.
• Pregnant and lactating women.