الفهرس 
IntroductionOnly 14 pages are availabe for public view
Abstract
With the increasing demand for esthetic appearance, a great development of bleaching products has been developed. Therefore, the present investigation was done to evaluate the effect of three concentrations of Carbamide Peroxide bleaching agents on mineral content and surface topography.
Three chemically activated bleaching materials with different concentrations of bleaching agents were used in this investigation. All were composed of 11% Fluoride, 3% Potassium nitrate and three concentrations of Carbamide Peroxide (10%, 15% and 35%).
A total of twenty eight upper extracted molars specimens were collected from sound non cracked teeth that extracted for periodontal problems with age range (40 to 50) years old. All the teeth were cleaned of blood and debris using an ultrasonic scaler. Specimens were divided into four main groups (n = 7).
Each crown was separated from the root at the cement-enamel junction and sectioned vertically in mesio-distal direction to obtain two fragments (facial, palatal half) by diamond disk under a water-coolant system. Facial half was used because of its flatness.
Whitening tray was fabricated from a vacuum formed sheet to provide 0.7mm spacer to create a reservoir for the whitening gel. All bleaching procedures were achieved according to manufacturer’s instructions as Opalescence PF 15% for 6 hours, Opalescence PF 20% for 4 hours and Opalescence PF 35% for 30 minutes.
Testing procedures were done over all specimens before and after bleahing to evaluate the surface morphology by SEM. The quantitative calibration for Calcium, Phosphorus was done using the EDS analysis.
The results were collected, tabulated and statistically analyzed to show the effect each concentration on enamel surface morphology. It was shown that all concentrations were capable to do surface alteration but the more concentration the more alternation.
Calcium element ratio didn’t show any statistically significant difference but high concentration of carbamide peroxide could affect on Phosphorus ratio between the experimental groups.
Conclusions:
Under the limitation of this investigation, the following conclusions could be drawn:
1- There is a direct correlation between surface topography, mineral content and concentration of bleaching agent.
2- Low concentrations of carbamide peroxide are more conservative than high concentration on human enamel surface.
3- The method of SEM-EDS analysis seems to be a non-invasive technique and highly effective for screening topographic and elemental changes of human enamel.
Recommendations:
1. It is recommended to study the effect of different bleaching concentrations on enamel bonding.
2. Further investigations are recommended to evaluate cumulative effect of several applications of bleaching agents on enamel.