A study of hydrogen peroxide chemistry and photochemistry in tea stain solution with relevance to clinical tooth whitening
Available online 31 July 2012
Abstract
Objective
Tooth
whitening using hydrogen peroxide is a complex process, and there is
still some controversy about the roles of pH, temperature, chemical
activators, and the use of light irradiation. In this work the basic
interactions between whitening agents and stain molecules are studied in
simple solutions, thus avoiding the physics of diffusion and light
penetration in the tooth to give clarity on the basic chemistry which is
occurring.
Method
The
absorbance of tea stain solution at 450 nm was measured over a period
of 40 min, with various compositions of whitening agent added (including
hydrogen peroxide, ferrous gluconate and potassium hydroxide) and at
the same time the samples were subjected to blue light (465 nm) or
infra-red light (850 nm) irradiation, or alternatively they were heated
to 37 °C.
Results
It
is shown that the reaction rates between chromogens in the tea solution
and hydrogen peroxide can be accelerated significantly using ferrous
gluconate activator and blue light irradiation. Infra red irradiation
does not increase the reaction rate through photochemistry, it serves
only to increase the temperature. Raising the temperature leads to
inefficiency through the acceleration of exothermic decomposition
reactions which produce only water and oxygen.
Conclusion
By
carrying out work in simple solution it was possible to show that
ferrous activators and blue light irradiation significantly enhance the
whitening process, whereas infra red irradiation has no significant
effect over heating. The importance of controlling the pH within the
tooth structure during whitening is also demonstrated.
Comments