Raneen Ahmed Gohar; Omaima Mohamed Safwat And Shereen Hafez Ibrahim,

ABSTRACT
Objective: This Study Was Conducted To Evaluate The Change In The Mineral Content And Ultra-morphological Picture Of Enamel Bleached With Bleaching Agent Comprising And Not Comprising Fluoride.

Materials and Methods: A Total Number Of 14 Intact And Freshly Extracted Human Central Incisors Were Used In This Study. Each Tooth Was Divided Into Three Equal Thirds Of Enamel And Dentine Blocks. The Middle Third Is Assigned For For B0 (control Group), The Mesial Third Is Assigned For B1 (bleaching Without Fluoride) While The Distal Third Is Assigned For B2 (bleaching With Fluoride). Each Group Further Divided Into Two Subgroups According To PH Cycle (C). Where C1 Represents No PH Cycle And C2 Represents PH Cycle. Elemental And Ultramorphological Analysis Were Done For All Specimens In All Groups And Subgroups For Sound Unbleached Enamel, After Bleaching Procedure (under Manufacturer Instructions) And After PH Cycle. Quantitative Energy Dispersive X-ray Spectroscopy Elemental Analysis Was Performed On The Enamel Surface To Determine The Elemental Levels (%) Of Calcium (Ca), Phosphorus (P). The Calcium (Ca) And Phosphorus (P) Contents Were Evaluated In Weight Percent (wt. %) And The Mean Ca/P Ratios Were Calculated. The Ultra-morphological Analysis Was Done Using The Environmental Scanning Electron Microscope. One Image Was Obtained From The Center Of Each Enamel Surface Specimen With Magnification Of 4000X. Data Were Collected, Tabulated And Statistically Analyzed.

Results: Quantitative Energy Dispersive X-ray Spectroscopy Elemental Analysis Showed A Statistical Significant Difference Among The Three Groups (control, Bleaching Without Fluoride And Bleaching With Fluoride) In Ca Wt % And P Wt % While It Showed No Significant Difference Among Three Groups After Performing PH Cycle. However, Ca/P Ration Showed No Significant Difference Among The Three Groups But Showed A Significant Difference After Performing PH Cycle. SEM Photomicrographs Showed Morphological Changes In Enamel Surface After Bleaching With No Fluoride As Increase In Porosity, Erosion Giving Etching Like Appearance, While In Bleaching Comprising Fluoride The Morphologic Changes Were Minimal With Surface Discontinuity. After PH Cycle, Bleached Enamel Tends To Return Back To The Normal.

Conclusions: Bleaching Had An Equally Adverse Effect On Both Calcium And Phosphorous Content Of Dental Enamel. The Incorporation Of Fluoride In The Bleaching Agents Lessened Its Demineralizing Effect Also Caused Minimal Morphologic Changes In The Enamel Surface. The Incorporation Of Fluoride In The Bleaching Agent Enhanced The Remineralizing Capacity Of Artificial Saliva During PH Cycling Also Helped The Enamel Surface To Return Back To The Normal.