title: Effect of smear layer and root-end cavity thickness on apical sealing ability of MTA as a root-end filling material: a bacterial leakage study.
abstract: OBJECTIVE
  The aim of this study was to investigate the effect of the cavity thickness and smear layer on apical sealing ability of mineral trioxide aggregate (MTA) as a root-end filling material.
  
  
  METHODS
  Seventy single-rooted maxillary central teeth were used in this study. All teeth were instrumented to size 50 using a step-back technique. The selected teeth were randomly divided into 4 groups, each containing 15 experimental samples and 5 positive and 5 negative control samples. In the first and second groups (smear+), the teeth were irrigated with only 5.25% NaOCl. In the third and fourth groups (smear-), the teeth were irrigated with 17% EDTA and 5.25% NaOCl to remove the smear layer. Also, in the first and third groups, cavities were prepared as 3 mm. In the second and fourth groups, cavities were prepared as 5 mm. All the root-end cavities were then filled with MTA. Nail varnish was applied to all external root surfaces to the level of the resected root-ends to prevent lateral microleakage. Samples were sterilized in an ethylene oxide sterilizer for 12 hours. The apical 3-4 mm of the roots were immersed in brain heart infusion culture medium with phenol red indicator within culture chambers. The coronal access of each specimen was inoculated every 48 hours with a suspension of Enterococcus faecalis. Bacterial leakage was monitored every 24 hours for 4 weeks. The data obtained were analyzed using a chi-squared test, with alpha = .05 as the level for statistical significance.
  
  
  RESULTS
  There were no statistically significant differences in rate of bacterial leakage among the experimental groups at 1-4 weeks (P > .05). Also, there was no difference between the groups when the 2 thickness groups were combined (P > .05). However, there was statistically significant differences when the 2 smear groups were combined for 4-week observation periods (P < .05). Removal of the smear layer caused significantly more apical microleakage than when the smear layer was left intact for 4 weeks.
  
  
  CONCLUSIONS
  The thickness of root-end cavity (3 or 5 mm) had no influence in the bacterial leakage of the root end filled with MTA. Removing the smear layer may not be necessary in root-end cavities filled with MTA.
authors.affiliation: Department of Operative Dentistry, Faculty of Dentistry, Karadeniz Technical University, Trabzon, Turkey. tahsiny@hotmail.com
authors.forename: Tahsin
authors.initials: T
authors.lastname: Yildirim
authors.forename: Kürşat
authors.initials: K
authors.lastname: Er
authors.forename: Tamer
authors.initials: T
authors.lastname: Taşdemir
authors.forename: Erhan
authors.initials: E
authors.lastname: Tahan
authors.forename: Kurtuluş
authors.initials: K
authors.lastname: Buruk
authors.forename: Ahmet
authors.initials: A
authors.lastname: Serper
mesh_terms: D017607:Aluminum Compounds; D017610:Calcium Compounds; D016009:Chi-Square Distribution; D003763:Dental Leakage / Q000517:prevention & control*; D003786:Dental Pulp Cavity / Q000382:microbiology / Q000473:pathology*; D004338:Drug Combinations; D013293:Enterococcus faecalis; D006801:Humans; D007180:Incisor; D008437:Maxilla; D010087:Oxides; D012184:Retrograde Obturation / Q000295:instrumentation / Q000379:methods*; D012387:Root Canal Filling Materials; D017640:Silicates; D016369:Smear Layer
chemical_list: D017607:Aluminum Compounds; D017610:Calcium Compounds; D004338:Drug Combinations; D010087:Oxides; D012387:Root Canal Filling Materials; D017640:Silicates; C086631:mineral trioxide aggregate