Siriporn TimpawatSomsak SripanaratanakulMahidol UniversityRoi-ED Province Hospital2018-07-042018-07-041998-01-01Journal of Endodontics. Vol.24, No.5 (1998), 343-345009923992-s2.0-0032062435https://repository.li.mahidol.ac.th/handle/20.500.14594/18352The effect of two different root canal cements and removal of the smear layer on the apical seal in roots obturated with Thermafil obturators was tested. Thirty extracted human mandibular first molars with 60 canals (mesial roots) were instrumented with the use of a step-back technique. Teeth were placed into 6 groups of 10 canals each. The first three groups had the smear layer removed with EDTA and NaOCl, and the other three groups were irrigated with NaOCl only. Canals were obturated using Thermafil without sealer cement or Thermafil with Ketac-Endo or Thermafil with zinc oxide-eugenol cement. All roots were placed in India ink for 4 days. The roots were cleared, and the degree of linear dye penetration was measured. The study showed that root canal cement significantly improved the apical seal of the Thermafil obturation technique (p < 0.05), whether the smear layer was removed or not. The apical seal exhibited by Ketac-Endo was not significantly different from that provided by zinc oxide-eugenol cement (p > 0.05), regardless of the presence or absence of a smear layer. Copyright © 1998 by The American Association of Endodontists.Mahidol UniversityDentistryArticleSCOPUS10.1016/S0099-2399(98)80131-3