Guidelines for the selection of tooth whitening products amongst those available on the market.

BACKGROUND: Several tooth whiteners are available on the market, and the ideal choice should be determined by efficacy and optimal clinical results. OBJECTIVES: The purpose of this study was to compare the reported clinical success rates of different tooth whitening products. SEARCH STRATEGY: The relevant literature (1998 - 2011) was studied, using as sources the databases: Google Scholar, Science Direct, Medline and Pubmed. SELECTION CRITERIA: The material was clearly identified, the manufacturers' instructions were respected and the sample size stated. RESULTS AND CONCLUSIONS: This descriptive report on 49 papers focuses on the total colour change, measured with a calibrated shade guide and also numerically (colourimeter, chromameter or spectrophotometer), the relapse of the colour change and tooth sensitivity. In general, the dentist-supervised at-home bleaching and the in-office treatment gave approximately the same initial percentage improvement of tooth whitening. However, the relapse after a four week or longer period was significantly higher for the in-office treatment. The treatment of choice should be a dentist supervised at-home bleaching product which generally contains approximately 10% carbamide peroxide applied over about 14 days for about eight hours per night. Tooth sensitivity should not be a general problem although some subjects might choose to discontinue treatment as a result of sensitivity.

The radiolysis of aqueous solutions of ethylene.

The products of the radiolysis of deaerated aqueous solutions of ethylene at atmospheric pressure are butane, hexane, octane, decane, acetaldehyde, butyraldehyde, ethanol, butanol, and hydrogen perioxide. Product yields, especially those of the aldehydes and hydrogen peroxide, increase with increasing ethylene concentration and decrease with increasing pH and radiation dose. Addition of efficient electron scavengers increases the yields of oxidized products and decreases the yields of reduced products. The results are compatible with a mechanism in which OH radicals add to rather than abstract from ethylene. Computer-aided analysis of the kinetics of competing reactions indicates that the low yields of aldehydes are related to the ability of these compounds to act as internal scavengers of solvated electrons.