An Alternative Adhesive Strategy to Optimize Bonding to Root Dentin Sema Belli, DDS, PhD,* Funda Kont Cobankara, DDS, PhD,* Betul Ozcopur, DDS, PhD, † Evrim Eliguzeloglu, DDS, PhD, † and Gurcan Eskitascioglu, DDS, PhD † Abstract Introduction: This study examined the hypothesis that the shear-bond strengths of AH Plus (AH) and Hybrid Root Seal (HRS) to root dentin might be optimized by using a powdered dentin-reinforced bonding procedure. Methods: The surfaces of root halves obtained from extracted human premolars were ground (800-grit silicon carbide paper), treated (5.25% NaOCl 17% EDTA for 5 minutes followed by distilled water) and randomly allo- cated into two groups according to the sealer and then into three subgroups according to bonding procedure. Dentin particles with a maximum size of 25 mm were incorporated into the adhesive of Clearfil Liner Bond 2V, and groups were created as follows: no adhesive, adhesive alone, and with powdered dentin reinforced adhesive; 3  3 mm high buildups were created using sealer and allowed to set (37  C, 100% humidity, 72 hours). Shear tests were performed (1 mm/min). Data were calculated as MPa and analyzed (two-way analysis of variance, Tukey test). Results: A significant difference was found between the groups (P = .000). Adhesive or reinforced adhesive had a negative effect on the shear- bond strength of AH, but they significantly increased the shear-bond strength of HRS (P = .000). HRS showed a similar bond strength with either adhesive alone or adhesive reinforced with powdered dentin. AH group was characterized by mixed failure, whereas the predom- inant failure type of the HRS group was cohesive failure within the sealer. Conclusions: Reinforcing adhesive resin with powdered dentin may be considered an alter- native for optimizing the bonding of methacrylate-based sealers to root dentin and might affect the shear bond strength. (J Endod 2011;37:1427–1432) Key Words Adhesion, in vitro test, powdered dentine, root dentine, self-etch adhesive R esin-based sealers have gained popularity with the recent growing interest in adhesive endodontics (1). However, several factors make adhesion to the root canal system a challenge, such as chemical substances used during the biomechanical preparation (2), volumetric changes that occur in resin-based sealers during polymerization (3), debonding of the sealer because of polymerization shrinkage stresses (4), and various geometric factors (5). Studies on alternative strategies to improve bonding to root dentin determined that adhesive systems were effective in optimizing bond strengths to radicular dentin (6, 7) and in improving sealing ability (8). Self-etching adhesives with acidic monomers have recently gained popularity. These systems are easy to apply and are characterized by reduced technique sensitivity. Because the acidic functional monomers are not rinsed off, the potential exists for further demineralization (9). Maeda et al (10) and Iwasa et al (11) incorporated powdered dentin to self-etching primers in order to neutralize continuous etching activity (12) and to test possible pH changes that occur during the reactions (13). They concluded that dentin has a strong buffering capacity (10) and a strong modula- tion effect against the acidity of self-etching adhesives (11). Fillers have also been added to adhesives in order to improve bond strengths by reinforcing the hybrid layer and reducing polymerization shrinkage (14). The lack of shrinkage stress relief is one of the major problems associated with endodontic bonding because of the high cavity configuration-factor (C-factor) (5, 15). Filler may also give the bond a gel-like consistency (16), which results in a thicker bonding-resin layer (16, 17). Adhesives with thicker bonding-resin layers may act as stress breakers, confirming the elastic bonding concept and resulting in a superior bond (18). The term ‘‘monoblock,’’ literally meaning a single unit, has recently become a familiar term in the endodontic literature (19). Achieving a mechanically homogenous unit with root dentin using adhesive materials should be the goal of successful endodontic treatment although this is not always possible in the clinical conditions. Monoblocks in endodontically treated teeth and potential negative outcomes of different interfaces with various elastic modules have been explained (20). Incorporating powdered dentin into adhesives has the potential to help create a more dentin-like adhe- sive interface between the sealer and the root dentin, thus supporting the monoblock concept (20) and a strong ionic interaction between the root dentin and the adhesive material to enhance the bond strength. Thus, the purpose of this study was to test the hypothesis that shear-bond strengths of an epoxy-resin-based sealer AH Plus (AH) (Dentsply, De Trey, Konstanz, Germany) and a 4-methacryloxyethyl trimellitate anhydride (4-META) containing the self-etching, self-adhesive sealer, Hybrid Root Seal (HRS) (Sun Medical, Tokyo, Japan), to root dentin might be optimized by incorporating a powdered dentin-reinforced, self-etching bonding procedure. Materials and Methods The materials used in the study are listed in Table 1. Preparation of Root Surfaces Forty-two extracted human premolar teeth that had been stored in distilled water for a maximum of 2 months were used. Soft-tissue covering surfaces were scaled using periodontal curettes (Dufflex, Rio de Janeiro, RJ, Brazil). The crowns From *Selcuk University Faculty of Dentistry, and † Yuzuncuyil University Faculty of Dentistry, Van, Turkey. Address requests for reprints to Dr Sema Belli, Selcuk University Faculty of Dentistry, Konya, Turkey. E-mail address: sbelli@selcuk.edu.tr 0099-2399/$ - see front matter Copyright ª 2011 American Association of Endodontists. doi:10.1016/j.joen.2011.06.014 Basic Research—Technology JOE — Volume 37, Number 10, October 2011 An Alternative Strategy for Bonding to Root Dentin 1427