Effects of Different Curing Units and Luting Agents on Push-out Bond Strength of Translucent Posts Yahya Orc ¸un Zorba, PhD,* Ali Erdemir, PhD, † Ali Turkyilmaz, † and Ayc ¸e U ¨ nverdi Eldeniz, PhD ‡ Abstract Introduction: The aim of this study was to evaluate the effects of different curing units and 2 luting cements on the push-out bond strength of a translucent fiber post. Methods: Thirty maxillary incisor roots were endodon- tically treated. Post spaces were prepared, and the smear layers were removed. Posts (FRC Postec Plus) were luted with either a self-etch cement (Panavia F 2.0) or a self-adhesive cement (Maxcem). Luting agents were then light-activated with a quartz-tungsten- halogen, a blue light–emitting diode, or a plasma-arc curing unit. Roots/cemented posts were transversally sectioned from coronal to apical. Push-out tests were performed, and data were analyzed by using three- way analysis of variance and Tukey tests. Results: Push-out bond strengths were significantly affected by the type of luting agent (P < .05) and root region (P < .05). The type of light source used in curing did not affect push-out bond strengths (P > .05). Conclusions: Self- adhesive resin cement provided higher bond strength than the self-etch cement when smear layer was removed before the post cementation. The push-out bond strength in the apical portion of the root was significantly lower than in the coronal region. The use of different curing units in the photoirradiation of dual-cured resin cement did not affect the retention of the fiber post as a result of the limited light transmission capability of this post. (J Endod 2010;36:1521–1525) Key Words Curing units, luting agents, push out bond strength F iber posts, in combination with resin cements, have been widely used to restore endodontically treated teeth (1). The resin cements can be categorized according to adhesion technique as etch-and-rinse, self-etch, or self-adhesive. Although all 3 classes of cements have been investigated, the correct clinical choice among them is not always clear (2). In terms of polymerization, resin cements can be self-curing, light-curing, or dual- curing. Self-curing cement is difficult to manipulate and place because of its limited working time. Light-curing resin is not recommended for fiber-post cementation because of inadequate depth of cure in the apical portion of the root, even when trans- lucent posts are used (3). Dual-curing cement sets mainly through radical polymeriza- tion that is initiated by either light exposure or self-cures. Although dual-cured resin cements have been recommended for the cementation of fiber posts, some dual- cured cements might not reach to an adequate degree of conversion in the absence of light (4); therefore, light-curing is recommended (5). Adequate curing is considered to be especially important in the apical portion of the root canal (6). Various types of curing units are routinely available for the light activation of composite resins, including quartz tungsten halogen (QTH), light-emitting diodes (LED), plasma arcs (PAC), and lasers (7). However, limited data are available about the effects of different light sources on post bond strength. The purpose of this in vitro study was to evaluate the effects of different light- curing techniques and adhesives on the retention of fiber posts in different root regions. The null hypothesis is that the push-out strength of root canal fiber posts is not signif- icantly affected by curing technique, type of adhesive system, or root region. Materials and Methods Thirty extracted human maxillary incisor teeth with straight root canals were used in this study. Crowns were removed to obtain a root height of 17 mm. A working length of 1 mm above the radiographic apex was established. The root canals were instru- mented by using stainless steel K-files (#08-10-15; Dentsply Maillefer, Ballaigues, Switzerland), Mtwo rotary nickel-titanium instruments (#10-15-20-25; Sweden & Mar- tina, Due Carrare, Padova, Italy), and .06 taper profiles (#30-35-40; Dentsply Maillefer) mounted in a 16:1 gear-reduction handpiece driven by an electric motor (X-Smart; Dentsply DeTrey GmbH, Konstanz, Germany). Instrumentation was performed under a loupe (Heine, Herrsching, Germany) at 2.5 magnification. The root canals were irrigated with 2.5% sodium hypochlorite after each instrument. The root canals were dried with paper points and obturated with gutta-percha cones and AH Plus sealer (Dentsply) by using a lateral condensation technique with a finger spreader (Mani Inc, Tochigi, Japan). Immediately after obturation, the post spaces were prepared by removing 10 mm of gutta-percha by using a #2 Peeso reamer (Mani Inc., Tochigi-Ken, Japan), retaining at least 5 mm of root filling at the apical level (8). The canal walls were enlarged by using FRC Postec Plus low-speed post drill (#1; Ivoclar-Vivadent, Schaan, Liechtenstein), and the smear layer was removed by using ultrasonic agitation (ART P1; Bonart Co, Taiwan), with a #15 hand-file and 5 mL of 17% ethylenediaminetetraacetic acid (EDTA) followed by 5 mL of 5.25% NaOCl as an irrigant. Final irrigation was accomplished with 10 mL of distilled water. The root canals were dried by using paper points. Before cementation, posts (FRC Postec Plus) were cleaned with 95% ethanol, and a single layer of silane coupling agent (Monobond-S; Ivoclar-Vivadent) was applied to From the *Department of Restorative Dentistry and Endodontics, Faculty of Dentistry, Erciyes University, Kayseri, Turkey; † Department of Endodontics, Faculty of Dentistry, Kirikkale University, Kirikkale, Turkey; and ‡ Department of Endodontics, Faculty of Dentistry, Selcuk University, Konya, Turkey. Address requests for reprints to Dr Yahya Orcun Zorba, Department of Restorative Dentistry and Endodontics, Faculty of Dentistry, Erciyes University, 38039, Melikgazi, Kayseri, Turkey. E-mail address: orcunzorba@kku.edu.tr. 0099-2399/$0 - see front matter Copyright ª 2010 American Association of Endodontists. doi:10.1016/j.joen.2010.04.026 Basic Research—Technology JOE — Volume 36, Number 9, September 2010 Effects of Curing and Luting Agents on Push-out Bond Strength 1521