الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The present study was conducted to evaluate the potential use of Er:YAG laser on cutting dentin safely with different energy levels and bonding of either etched or conditioned lased dentin to resin composite or glass ionomer filling materials .
It was conducted on 200 prepared dentin samples either non lased or ablated with different energy levels of 200 mJ , 300 mJ , 400mJ and 500 mJ of Er:YAG laser . Half of the samples either etched or non etched to bond to resin composite & the other half either conditioned or non conditioned to bond to glass ionomer filling material . The surface roughness were measured for all samples before laser ablation, after laser ablation, after pretreatment of the dentin surfaces. The shear bond strengths between dentin surfaces and restorative materials were measured and statistically analyzed. The microstructure changes were evaluated by scanning electron microscope.
Under the limitation of this investigation the following conclusions could be drawn :
1- The increase of Er:YAG laser energy levels followed by increase in dentin surface roughness even after etching or conditioning.
2- The increase in Er:YAG laser energy level used followed by the increase of the bond strengths of unetched dentin to resin composite.
3-While the increase of Er:YAG laser energy level used followed by the decrease of bond strength of etched dentin to resin composite .
4- The increase of Er:YAG laser energy level used followed by the decrease of bond of dentin to glass ionomer restorative material either before or after conditioning .
5- Using Er:YAG laser for preparing dentin surfaces affecting surface morphological characteristics which may interfere with bonding of tooth colored restorative materials to lased dentin.
6- Still the conventional method is preferable than Er:YAG laser for dentin preparation.
Recommendations:
1 - It is recommended to use Er:YAG laser at energy levels 200 mJ followed by acid pretreatment of dentin before application of tooth colored restoratives as it shows highest shear bond strength and minimal dentin surface alteration
2 - It is recommended to study the interaction patterns between dentin and resin composite or glass ionomer when the Er:YAG laser was used for cavity preparation .