Efficacy of polyphasic calcium phosphates as a direct pulp capping material Wakako Kiba a , Satoshi Imazato a, *, Yusuke Takahashi a , Seisuke Yoshioka a , Sigeyuki Ebisu a , Takayoshi Nakano b a Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, Japan b Department of Materials Science and Engineering, Osaka University Graduate School of Engineering, Japan 1. Introduction For direct pulp capping, Ca(OH) 2 -based materials have been used clinically for many years. 1,2 However, Ca(OH) 2 -based materials have no adhesive properties toward either dentin or overlaid resins, and they provide poor sealing of the exposed site. 3,4 Since their physical properties are low, they are prone to dissolution by acid-etching 5 and demonstrate low durability. 6 As an alternative to Ca(OH) 2 -based materials, usage of mineral trioxide aggregate (MTA) or resinous adhesives for vital pulp therapy has been proposed. MTA exhibits good sealing ability when used for root-end filling, 7 while it has no journal of dentistry 38 (2010) 828–837 article info Article history: Received 24 November 2009 Received in revised form 29 June 2010 Accepted 30 June 2010 Keywords: Direct pulp capping Calcium phosphates Dentin bridge Odontoblasts Ca release Rat abstract Objectives: Polyphasic calcium phosphates (Poly-CaP), a complex of hydroxyapatite (HAp) and soluble calcium phosphates including a-tricalcium phosphate and tetracalcium phos- phate, demonstrate promoting effects on hard tissue formation by osteoblasts. We hypoth- esized that a Poly-CaP block with a soluble calcium phosphates phase on one side and an insoluble HAp phase on the other side is useful for vital pulp therapy as it may promote dentin regeneration and provide the surface effective to achieve sealing. The purpose of this study was to investigate the efficacy of Poly-CaP as a direct pulp capping material by examining the Ca-release profile, the in vivo ability to induce reparative dentinogenesis, and the bonding of HAp surface with adhesive systems. Methods: Poly-CaP prepared by annealing crude HAp disc was immersed in buffer solution at pH 7.4 or 4.0, and the concentration of Ca released was measured until 15 days. The pulp of 9- week-old Wister rat molar was exposed and capped with Poly-CaP or HAp block, and dentin bridge formation and pulpal inflammation was evaluated histopathologically after 2 or 4 weeks. Etch & rinse or self-etching adhesive was bonded to HAp surface, and the interface was observed using SEM. Results: Poly-CaP exhibited continuous release of Ca with significantly greater amount than HAp at both pH conditions (P < 0.05, Student’s t-test). Animal tests demonstrated formation of complete dentin bridge at higher rate for Poly-CaP compared with HAp after 4 weeks (P < 0.05, Steel–Dwass test). Impregnation of resin into etched HAp surface, with production of intimate contact at the bonding interface, was seen for all adhesives. Conclusions: Poly-CaP is a potentially useful material for direct pulp capping with the advantages to promote dentin bridge formation and to provide tight sealing by adhesives. # 2010 Elsevier Ltd. All rights reserved. * Corresponding author at: Department of Restorative Dentistry and Endodontology, Osaka University Graduate School of Dentistry, 1-8, Yamadaoka, Suita, Osaka 565-0871, Japan. Tel.: +81 6 6879 2927; fax: +81 6 6879 2927. E-mail address: imazato@dent.osaka-u.ac.jp (S. Imazato). available at www.sciencedirect.com journal homepage: www.intl.elsevierhealth.com/journals/jden 0300-5712/$ – see front matter # 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.jdent.2010.06.016