Abstract :
Purpose was to compare the effect of number of visits (1-visit, 2-visits with (Ca(OH)2) dressing for 7 days) on bacterial count in necrotized root canals with no apical lesions. Forty patients were accepted. Teeth selected (n=40) were all single-canaled, single-rooted with necrotized pulp and no apical lesions. Teeth were divided into 2 equal groups based on treatment method (G1, G2). Samples were collected from canals before preparation (S1, S3). Preparation in both groups was done using rotary and hand files with NaOCl (5.25%) and EDTA (17%) as irrigants, CHX (2%) was used in the final rinse. Root canals in G1 were treated in a single visit, while using a two-visits approach in G2. A dressing of (Ca(OH)2) was applied in root canals of G2 after preparation for 7 days. Samples were collected from root canals before filling (S2, S4) in both groups. All samples were transported to bacteriology lab in fluid thioglycollate transport medium, and later were cultured on blood agar then incubated in aerobic and anaerobic conditions for 24 hours. Colony forming units (CFU) were counted and bacterial reduction in (S1, S3) and (S2, S4) was analyzed. None of the treatment methods rendered the root canals bacteria-free. G1 had a bacterial reduction average of (74.59%) for anaerobes and (75.13%) for aerobes, whereas G2 had (90.20%) for anaerobes and (82.36%) for aerobes. Difference was statistically significant (p<0.05). Two-visits treatment with (Ca(OH)2) dressing for 7 days reduced bacterial count more than single visit treatment.