Journal of Dental Research, Vol 72, 67-71, Copyright © 1993 by International & American Associations for Dental Research Online Journals
The effects of etching, micro-abrasion, and bleaching on surface enamel
L. S. Tong, M. K. Pang, N. Y. Mok, N. M. King and S. H. Wei
Department of Children's Dentistry & Orthodontics, Faculty of Dentistry, University of Hong Kong, Sai Ying Pun.
Conservative techniques for improving the appearance of discolored teeth
have become popular in the past decade. These include: in-office bleaching
with 30% hydrogen peroxide, which is applied on etched enamel with a gauze
pad and then exposed to a bleaching light; home bleaching with a mild form
of peroxide, such as 10% carbamide peroxide, which is applied on the tooth
surface with custom-made mouthguards; and enamel micro-abrasion with 18%
hydrochloric acid, which is applied in a pumice slurry. In this study, the
in-office bleaching and enamel micro-abrasion techniques were performed on
extracted teeth for investigation of their microscopic effects on the
surface enamel. Specimens treated only with 37% phosphoric acid showed an
enamel loss of 5.7 +/- 1.8 microns. The specimens treated with 37%
phosphoric acid followed by 30% hydrogen peroxide showed enamel loss of 5.3
+/- 1.6 microns; this loss was probably not caused by the hydrogen
peroxide, but rather by the etching with 37% phosphoric acid which preceded
the hydrogen peroxide application. A direct application of 18% hydrochloric
acid for 100 s resulted in a loss of 100 +/- 47 microns. The extent of
enamel loss was much greater when the 18% hydrochloric acid was applied in
a pumice slurry for the same period of time (360 +/- 130 microns), and the
effect was time-dependent. Thus, the pumice and rotary prophy cup used in
conjunction with the 18% hydrochloric acid contributed markedly to the loss
of surface enamel, enhancing the non-selective stain-removing action of the
hydrochloric acid. Therefore, the hydrochloric acid-pumice technique must
be used clinically with caution.
