الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
• Aim: The aim of the study is to clinically evaluate and compare the antimicrobial effect of calcium hydroxide paste, 980 nm diode laser and combined effect of diode laser and Ca (OH)2 pasteon extracted root canals infected with E. faecalis. Methodology: Eighty single rooted extracted human permanent teeth were infected with E. faecalis then divided into four equal groups as follow: Group 1 (Ca (OH)2 Group): The infected canals were medicated with prefilled syringes of Ca (OH)2 paste UltraCal XS, then incubated at 37˚C for 7 days. Group 2 (Diode laser Group): The infected canals in this group were irradiated with 2 W diode laser 980 nm for 1 minute then root canals were sampled immediately. Group 3 (Combination group diode laser 2 W and Ca (OH)2 for 7 days): The infected canals in this group were irradiated with 2 W diode laser 980 nm for 1 minute, then Ca (OH)2 was introduced into the canals. Then root canals were incubated at 37˚C for 7 days. Group 4 (Combination group diode laser 1 W and calcium hydroxide for 2 days): The infected canals in this group were irradiated with 1 W diode laser 980 nm for 30 minutes, then Ca (OH)2 was introduced into the canals. Then root canals were incubated at 37˚C for 2 days. Antibacterial efficacy was assessed by intracanal sampling before and after treatment by paper point method. These samples were cultured on K F streptococcus agar media then incubated for two days then colony forming units were counted, also assessment included evaluation of the scanning electron microscope SEM for morphological and ultrastructural analysis for root canal wall, smear layer, dentinal tubules and dentine surface. Results showed that in group 1 there was 96 %
reduction of bacterial count, while in group 2 it was 98.9 %, in group 3 it was 99.8 % and in group 4 it was 99.5 %. The scanning electron microscope SEM evaluation revealed partial sealing of the dentinal tubules opening, scattered calcium hydroxide remnant and melted dentin after laser irradiation. Conclusions: Combination of diode laser and calcium hydroxide seemed to be the best effective treatment against E. faecalis.