Bleaching agents may change surface micro-morphology of enamel, Finds study

Hence, Nazish Fatima from the Ziauddin University conducted the present study to assess the efficacy of home bleaching agents. The author set up an experimental study on forty- five-sound human third molar crowns, all of which were extracted for periodontal reasons.

The discs were prepared at Material Engineering Department of NED University of Engineering and Technology, Karachi, and surface morphology was analyzed at Centralized Science Laboratory of Karachi University, Pakistan. Longitudinal sections were made using diamond disks (0.2 mm) underwater lubrication to obtain enamel slabs measuring (3 mm x 3 mm).

The slabs were embedded in polystyrene resin by using 2.0 cm diameter PVC molds, leaving the outer enamel surface uncovered by the resin. Ninety dental enamel slabs were prepared. The slabs were then randomly divided into 3 groups. Each group contained thirty specimens (n=30). Group 1 was kept in artificial saliva at 37°C in an incubator (Memart, Germany) during the whole experiment. Group 2 was treated with power whitening gel (White Smile 2011, Germany). Group 3 was treated with a tooth whitening pen (White Smile 2011, Germany).

The most central region or the region that was most representative of the entire surface area was used. The SEM (Jeol-Japan-JSM6380A, JAPAN) micrographs were examined to determine the type of surface presented. The enamel changes were classified as no or mild alteration, moderate alteration, and severely altered surface.

The results revealed that regarding micro-morphology, the enamel surface of control groups showed a smooth surface in general with some scattered clear scratches due to the polishing procedure. The specimens bleached in group 2 and group 3, represented areas of mild erosion.

This led the author to conclude that "bleaching with 38% Hydrogen Peroxide (HP) and 16% Carbamide Peroxide (CP) resulted in mild changes in surface micro-morphology of enamel."