الفهرس 
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Abstract
The aim of the study is to compare the effectiveness of using Er: YAG and Er,Cr:YSGG lasers in debonding of two different types of ceramic brackets and its effect on enamel surface.
One hundred and forty-four premolars were chosen from extracted teeth due to orthodontic reasons from patients seeking orthodontic treatment in the Department of Orthodontics, Faculty of Dentistry, Ainshams University. The teeth were sound with no cracks or enamel defects that may occur from the extraction forces.
Polycrystalline and monocrystalline ceramic brackets were used in this study, the brackets were bonded to the buccal surface of the teeth. The teeth were divided into 3 groups: mechanical debonding (Control group), Er:YAG debonding and Er,Cr:YSGG debonding, each group further subdivided into two subgroups of polycrystalline and monocrystalline brackets.
The teeth used in the laser group were accessed to the pulp chamber to allow the use of thermocouple device to measure the change in temperature in the pulp chamber.
The results were evaluated by Adhesive Remnant index (ARI), Temperature increase, time of debonding and Enamel damage. It concluded that the use of Laser to debond ceramic brackets is effective and more convenient than conventional method, monocrystalline brackets are faster in debonding with Er:YAG laser than Er,Cr:YSGG laser, no significant difference in ARI between monocrystalline brackets, and a highly significant difference in ARI between polycrystalline brackets in which the Er,Cr:YSGG laser showed lower values of ARI than the other two methods.
The rise of temperature in the two laser groups were withing the biological limit making it safe to use in debonding of ceramic brackets.
No enamel damage was noted in any of the groups.