A COMPARATIVE STUDY OF BLEACHING WITH HYDROGEN PEROXIDE VERSUS CARBAMIDE PEROXIDE ON ENAMEL SURFACE AND THE EFFECT OF AMORPHOUS CALCIUM PHOSPHATE APPLICATION FOLLOWING BLEACHING (SCANNING ELECTRON MICROSCOPE ATTACHED WITH ENERGY DISPERSIVE X-RAY ANALYZER STUDY).

Bleaching agents have effect on chemical and morphological structure of enamel that must be taken into account when this therapy is used. Aim: reveal and compare the effect of two bleaching agents containing a high a concentration of hydrogen peroxide (HP) and carbamide peroxide (CP) on enamel surface and evaluate the re-mineralizing effect of amorphous calcium phosphate gel (ACP) on enamel surface. Material and method: 32 extracted human upper first premolars were divided into 4 Control groups (CG) (before bleaching procedure), was named as: CG I, CG II, CG III and CG IV. 4 Experimental groups (EG) in which the teeth of the control groups utilized as experimental after bleaching procedure. Teeth were subjected to 40% HP in EGI, 35% CP bleaching in EGII, 40% HP & ACP in EGIII and 35 % CP & ACP in EGIV. All groups were prepared to SEM analysis and EDAX. Results: Both HP and CP significantly altered enamel superficial surface structure causing irregular surface, erosive lesions and craters. Globular precipitates covering the entire enamel surface and occlusion of enamel rod ends were detected following ACP application.The chemical profile results revealed decrease in Ca and P contents of enamel surface following bleaching, while they increased after application of ACP and the opposite was to the carbon content. Conclusion: Hydrogen peroxide and carbamide peroxide have an erosive effect on enamel surface while ACP has a re-mineralizing effect