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Is Tooth Whitening Safe?
Most studies confirm that tooth whitening is safe and effective. Whitening gels that contain 10 percent carbamide peroxide (equivalent to 3.6 percent hydrogen peroxide) have not been shown to cause any damage to the enamel of the tooth. Higher concentrations of carbamide and hydrogen peroxide available from the dentist may weaken the enamel, but most of these formulas also contain fluoride offsetting this potential side-effect. People who use higher concentrations of whitening agents can also receive prescription fluoride gels from their dentist to help further protect their teeth.

If tooth sensitivity or gum irritation occur, it is best to start using the whitening product less frequently -- say, every other day instead of every day -- and reduce the amount of time spent whitening. Prescription fluoride is also used to treat sensitivity sometimes associated with tooth whitening. Irritation of the gums can occur from either the in-office, at-home or over-the-counter tooth whitening systems. Gum irritation is usually mild and reversible, but can be treated with over-the-counter products such as Orajel.



Alloxan and streptozotocin are widely used to induce experimental diabetes in animals
EXCERPT:
The mechanism of alloxan and streptozotocin action in B cells of the rat pancreas.
Szkudelski T.

Department of Animal Physiology and Biochemistry, University of Agriculture, Poznan, Poland.

Abstract
Alloxan and streptozotocin are widely used to induce experimental diabetes in animals. The mechanism of their action in B cells of the pancreas has been intensively investigated and now is quite well understood. The cytotoxic action of both these diabetogenic agents is mediated by reactive oxygen species, however, the source of their generation is different in the case of alloxan and streptozotocin. Alloxan and the product of its reduction, dialuric acid, establish a redox cycle with the formation of superoxide radicals. These radicals undergo dismutation to hydrogen peroxide. Thereafter highly reactive hydroxyl radicals are formed by the Fenton reaction. The action of reactive oxygen species with a simultaneous massive increase in cytosolic calcium concentration causes rapid destruction of B cells. Streptozotocin enters the B cell via a glucose transporter (GLUT2) and causes alkylation of DNA. DNA damage induces activation of poly ADP-ribosylation, a process that is more important for the diabetogenicity of streptozotocin than DNA damage itself. Poly ADP-ribosylation leads to depletion of cellular NAD+ and ATP. Enhanced ATP dephosphorylation after streptozotocin treatment supplies a substrate for xanthine oxidase resulting in the formation of superoxide radicals. Consequently, hydrogen peroxide and hydroxyl radicals are also generated. Furthermore, streptozotocin liberates toxic amounts of nitric oxide that inhibits aconitase activity and participates in DNA damage. As a result of the streptozotocin action, B cells undergo the destruction by necrosis.