The aim of the study is to clinically assess the peroxide levels in saliva during bleaching with 9.5% hydrogen peroxide using a tray with or without reservoir.

Statement of the Problem There is more concern about the possible adverse effect of bleaching agent, patients report gastrointestinal mucosal irritation e.g. a burning palate, throat and minor upsets in the stomach and intestine. Some adverse effects of hydrogen peroxide as a dental bleaching agent include dentin sensitivity and/or gingival irritation led by unstable and reactive H+ free radicals and low pH from prolonged use. Peroxide is a highly reactive substance which can damage oral soft tissues and hard tissues when present in high concentrations and with exposures of prolonged duration. (Alqahtani, 2014). Several researches have focused on the problem of gel ingestion and potential peroxide release in saliva (Dahl et al, 2003; Watt et al, 2004; Bernardon et al, 2010; Goldberg et al, 2010).

Rationale

Reservoirs are modifications in the tray molds to increase the amount of bleaching material carried by the bleaching tray, seeking greater bleaching efficacy. The use of reservoirs in the bleaching trays was initially seen as positive, since higher accumulation of material could provide the patient with greater treatment efficacy. Martini et al, 2020 stated that there is no significant difference between groups whitened with and without reservoirs for gingival irritation or tooth sensitivity. Most authors and bleaching gel manufacturers recommend the use of reservoirs to increase the amount of product available for bleaching and to allow for complete seating of the bleaching tray, although that the reservoirs decrease tray retention and increase lab fabrication time and cost (Javaheri et al, 2000). The presence of reservoirs decreases the retention of the tray, allowing more room for the gel but also reducing the adaptation of the tray. That may cause more leakage of the material, which may lead to more peroxide level in saliva. (Haywood et al, 1992).

A major concern for clinicians was the potential toxicological effect of hydrogen peroxide contacting soft tissues. A safe hydrogen peroxide exposure level (no observed effect level) was determined with catalase-deficient mice, reporting a maximum dose of 26 mg/kg/d. This corresponds to the dose level in humans, considering the conventional uncertainty factor of 100-fold, of 0.26 mg/kg/d (IGHRC, 2003; Hannig et al, 2005; Li et al, 2011). The safety of hydrogen peroxide products used for at home bleaching regarding peroxide release in saliva has not been fully proven.

Inclusion Criteria:

1. Good general health.
2. Absence of non-carious cervical lesions, active caries, gingival recession, or periodontal disease.
3. Do not use orthodontics appliance or removable prosthesis.
4. Maxillary anterior teeth without caries, restorations and/or endodontic treatment.
5. Mild generalized staining.

Exclusion Criteria:

1. Smoking or alcohol dependent patients.
2. Pregnancy and lactating women.
3. Parafunctional habits or pathologies.
4. Periapical alterations.
5. Use of medicaments that alter salivary flow.
6. Patients who had already undergone tooth bleaching
7. Patients with severe internal tooth discoloration as tetracycline stain, fluorosis or endodontic treatment.
8. Tooth hypersensitivity.
9. Presence of cracks or fractures.
10. Periodontal affection sign and symptoms.