Evaluation of the Influence of Smear Layer on the Apical and Coronal Sealing Ability of Two Sealers Funda Kont Çobankara, DDS, PhD, Necdet Adanır, DDS, PhD, and Sema Belli, DDS, PhD The aim of this in vitro study was to determine the effect of the smear layer on apical and coronal leakage in root canals obturated with AH26 or Roe- koSeal sealers. A total of 160 maxillary anterior teeth extracted for periodontal reasons were used. The root canals were prepared to a size #7 with ProFile .06 taper Series 29 rotary instruments in a crown-down manner. Eight groups were created by all possible combinations of three factors: smear layer (present/absent), leakage assessment (apical/coronal), and sealer used (AH26/Roeko- Seal). All teeth were obturated using lateral con- densation technique of gutta-percha. A fluid filtra- tion method was used to test apical or coronal leakage. According to the results of this study, the smear () groups displayed higher apical and coronal leakage than those smear () groups for both root canal sealers (p < 0.05). There was no statistically significant difference in either apical or coronal leakage between RoekoSeal and AH26, re- gardless of the presence or absence of the smear layer (p > 0.05). However, apical leakage was sig- nificantly higher than coronal leakage for both root canal sealers used in this study (p < 0.05). Under the conditions of this study, the results indicate that removal of the smear layer has a positive ef- fect in reducing apical and coronal leakage for both AH26 and RoekoSeal root canal sealers. One of the objectives of a successful endodontic treatment is the total obturation of the root canal system. To achieve this, the root canal filling must seal the canal space both apically and coronally to prevent the ingress of microorganisms or tissue fluids into the canal space. Apical leakage is considered a common reason for the clinical failure of endodontic therapy (1). Likewise, coronal leak- age is also reported to be an important reason for failure (2, 3). Many filling materials have been used in root canal therapy in an attempt to achieve success. The material most commonly recom- mended for obturation is gutta-percha combined with a sealer. Gutta-percha is considered an impermeable core material; there- fore, leakage through an obturated root canal is expected to take place at the interfaces between sealer and dentin or sealer and gutta-percha, or through voids within the sealer. Hence, the sealing quality of a root canal filling depends much on the sealing ability of the sealer (4). Many studies have indicated that leakage, whether apical or coronal, adversely affects the success of root canal therapy. There- fore, leakage studies on sealers remain important and necessary to determine the most suitable materials and to gain more understand- ing of the factors influencing the sealing properties. A review of a large number of published leakage studies points to general agreement that leakage occurs between the root filling and the root canal wall (5, 6). Therefore, anything that may influence the adaptation of the root filling to the canal wall is of great significance in determining the degree and the extent of leakage, and ultimately the prognosis of the endodontic therapy. In endodontic therapy, the smear layer formation results from root canal preparation and is mainly composed of inorganic com- ponents (dentin debris) and organic materials, such as pulp tissue remnants, bacteria, and blood cells (7, 8). There has been much interest in the possible effect of the smear layer on the leakage of the root canal sealer. However, there is still no consensus on the influence of the smear layer on the development of an effective seal of the root canal system. The aim of this in vitro study was to determine the effect of the smear layer on apical and coronal leakage in root canals obturated with laterally condensed gutta-percha and AH26 or RoekoSeal (RSA RoekoSeal Automix, Langenau, Germany) sealers. MATERIALS AND METHODS One hundred sixty maxillary anterior teeth (extracted for peri- odontal reasons) with straight root canals and fully developed apices were selected, cleaned of extraneous soft tissue and calcu- lus, decoronated at or below the cementoenamel junction, and stored in deionized water until use. In an attempt to standardize the length of canal involved in the experiment, similar root segments were used, with a length of approximately 17 mm. The pulp of each tooth was removed with a barbed broach. Canal patency was determined by passing a size 10 K file (Kerr, Romulus, MI) through the apical foramen. Working lengths were established 1.0 mm short of the apical foramen, and the roots were instrumented using ProFile .06 taper Series 29 rotary instruments (Tulsa Dental Products, Tulsa, OK). The same operator instrumented all the teeth JOURNAL OF ENDODONTICS Printed in U.S.A. Copyright © 2004 by The American Association of Endodontists VOL. 30, NO. 6, JUNE 2004 406