The Effects Of Different Carbamide Peroxide Whitening Agents On The Character Of Enamel And Clinical Evaluation

Nightguard vital bleaching (NGVB) has become more popular among both dentists and patients as a simple, effective, and safe procedure to lighten discolored teeth. The original technique involved the application of a 10% carbamide peroxide (CP) solution as the active whitening agent. Many modifications, improvements, and variations in the clinical technique have occurred over past years. One of the changes includes the use of CP in concentration greater than 10%. Currently, whitening solutions of 12 to 35% CP exists on the market for at-home whitening. Some clinicians and manufactures claim that higher-concentration CP whitening solutions are more effective and quicker in obtaining an esthetically bleaching result. On the other hand, it should be concerned about the possibility of increased side effects, such as tooth sensitivity and gingival irritation and effects on the tooth surface with the higher-concentration CP.Although pre-restorative carbamide peroxide bleaching is gaining popularity, its effect on the bond strength to composite has been inconclusive.The goal of this study was to evaluate the effects of 3 higher- concentration CP whitening solutions on the tooth surface in vivo with the scanning electron microscope and micro-hardness tester; the degree of color change, rebound effect, pulp sensitivities, and gingival status associated with using 2 concentration of CP in vivo; and the effects of bleaching on the shear bond strength of enamel to composite resin in different post-treatment times in vitro.The results suggest that:1. The SEM suggested there are slightly and local etching on the enamel surface of 30%CP treated group, no significant difference was observed on the 16%CP, 15%CP, and control group. There were no significantly differences on the micro-hardness of the enamel between the treated groups and the control group.2. At the end of 2nd week 30%CP fP 16%CP mean AE * were 10.45 and 8.12, at the end of &iri month were 4.03 and 3.57. Both the tooth bleached with 2 concentration of CP had a significant color change. Using of the 30 %CP resulted in significantly more lightness than 16%CP during first few weeks, at the end of the study there were no statistically significant difference. In addition, there were statistically significant differences on the gingival irritation, no statistically significant difference on the tooth sensitivity.3. There were significant differences in shear bond strength of composite resin to enamel in different post-treat time. Immediately bonding after bleaching resulted reduction about 58%. In 2 weeks, the bond strength could nearly returned to the untreated control group.