| Background:In recent years, fiber posts and resin-based luting cements have been recommended to rebuild endodontically treated teeth due to their dentin-matching mechanical characteristics, leading to fewer and favorable root fractures. Several in vitro studies demonstrated that predominant failures of bonding occurred at the cement-dentin interface. The efficacy of the dentin adhesive mostly depends upon the smear layer removal and the resin dentin interdiffusion zone (RDIZ) formation. Smear layer might be much more difficult to remove with regular water irrigation as manufacturer recommended, because of the narrow and deep circumstance of post space. Therefore, it seems still a challenge to achieve the appropriate condition of root canal dentin for effective bonding. To the author's knowledge, few studies have focused on the efficacy of smear layer and debris removal with different irrigations after post space preparation. However, these studies lacked data on the effects of the irrigants on the bond effectiveness after post space preparation. Objectives:One purpose of this study was to evaluate the effect of different irrigating solutions on smear layer removal on root canal surfaces after post space preparation, and to study whether additional ultrasonic irrigation has any effect on smear layer removal. Another purpose of this study was to evaluate the effect of different post space irrigants on dentin bonding effectiveness.Materials and Methods:1. Forty-eight anterior teeth were endodontically treated and cut transversely 2 mm coronal to the cemento-enamel junction. After post space preparation they were assigned to six groups: group A, 14% EDTA; group B, 5.25% NaOCl; group C, 0.9% NaCl; group D, 14% EDTA with ultrasonic activation; group E, 5.25% NaOCl with ultrasonic activation; group F, 0.9% NaCl with ultrasonic activation. After irrigation for 1 min respectively, specimens were then longitudinally sectioned in labio-lingual direction and examined under FE-SEM for debris removal at the apical, middle, and coronal thirds of the root canal. Kruskal-Wallis H test and Mann-Whitney U test were used for smear layer removal.2. Twelve anterior teeth were endodontically treated and cut transversely 2 mm coronal to the cemento-enamel junction. After post space preparation they were assigned to three groups: group A, 14% EDTA; group B, 5.25% NaOCl; group C, 0.9% NaCl. After irrigation for 1 min respectively, the specimens were filled with a self-etching adhesive system (Panavia F). All filled roots were stored in deionized water at 37℃for 1 week before observation. Specimens were longitudinally sectioned in labio-lingual direction and prepared for evaluation of RDIZ and resin tags at the apical, middle, and coronal thirds of the root canal. Results:1. EDTA performed significantly better than NaCl and NaOCl in smear layer removal (P<0.01 ), and no significant differences were found among the apical, middle, and coronal thirds in the EDTA group ( P>0.05 ). Additional ultrasonic irrigation did not improve smear layer removal significantly ( P>0.05 ) .2. Resin tag formation and RDIZ differed between the three irrigant groups. In group EDTA uniform RDIZ and resin tags were formed. In groups NaOCl and NaCl discontinuous gaps were observed between the dentin and resin cement along the entire root. Fewer and shorter resin tags were found.Conclusions:Different irrigants have significantly different effects on smear layer removal and bonding effectiveness after post space preparation. EDTA could effectively remove smear layer and improve the bond effectiveness. Moreover, the bond effectiveness of the evaluated self-etching adhesive system has a close relation to the smear layer removal. Therefore, irrigation with EDTA for 1min could effectively improve the smear layer removal and RDIZ formation, conducing to excellent bond effectiveness when self-etching adhesive systems are used for fiber post bonding. |
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