© 2014 Società Italiana Biomateriali - eISSN 2280-8000 J Appl Biomater Funct Mater 2014; 000-000 Vol. 0 no. 0, - 1 ORIGINAL ARTICLE Calcium silicate and calcium hydroxide materials for pulp capping: biointeractivity, porosity, solubility and bioactivity of current formulations Maria Giovanna Gandoli 1 , Francesco Siboni 1 , Tatiana Botero 2 , Maurizio Bossù 3 , Francesco Riccitiello 4 , Carlo Prati 1,5 1 Unit of Odontostomatological Sciences, Laboratory of Biomaterials and Oral Pathology, Department of Biomedical and NeuroMotor Sciences, University of Bologna, Bologna - Italy 2 Department of Cariology, Restorative Science and Endodontics, University of Michigan, Ann Arbor, Michigan - USA 3 Unit of Paediatric Dentistry, Department of Odontostomatological and Maxillo-Facial Sciences, University of Rome Sapienza, Rome - Italy 4 Department of Odontostomatological and Maxillofacial Sciences, University of Naples Federico II, Naples - Italy 5 Unit of Odontostomatological Sciences, Endodontic Clinical Section, Department of Biomedical and NeuroMotor Sciences, University of Bologna, Bologna - Italy DOI: 10.5301/jabfm.5000201 Accepted: January 10, 2014 ABSTRACT Aim: The chemical-physical properties of novel and long-standing calcium silicate cements versus conventional pulp capping calcium hydroxide biomaterials were compared. Methods: Calcium hydroxide–based (Calxyl, Dycal, Life, Lime-Lite) and calcium silicate–based (ProRoot MTA, MTA Angelus, MTA Plus, Biodentine, Tech Biosealer capping, TheraCal) biomaterials were examined. Calcium and hydroxyl ion release, water sorption, interconnected open pores, apparent porosity, solubility and apatite-forming ability in simulated body luid were evaluated. Results: All calcium silicate materials released more calcium. Tech Biosealer capping, MTA Plus gel and Biodentine showed the highest values of calcium release, while Lime-Lite the lowest. All the materials showed alkalizing activity except for Life and Lime-Lite. Calcium silicate materials showed high porosity values: Tech Biosealer capping, MTA Plus gel and MTA Ange- lus showed the highest values of porosity, water sorption and solubility, while TheraCal the lowest. The solubility of water- containing materials was higher and correlated with the liquid-to-powder ratio. Calcium phosphate (CaP) deposits were noted on materials surfaces after short aging times. Scant deposits were detected on Lime-Lite. A CaP coating composed of spherulites was detected on all calcium silicate materials and Dycal after 28 days. The thickness, continuity and Ca/P ratio differed markedly among the materials. MTA Plus showed the thickest coating, ProRoot MTA showed large spherulitic de- posits, while TheraCal presented very small dense spherulites. Conclusions: Calcium silicate-based cements are biointeractive (ion-releasing) bioactive (apatite-forming) functional bio- materials. The high rate of calcium release and the fast formation of apatite may well explain the role of calcium silicate biomaterials as scaffold to induce new dentin bridge formation and clinical healing. Key words: Bioactivity, Calcium hydroxide cements, Calcium silicate cements, MTA cements, Porosity, Pulp capping materials INTRODUCTION Pulp capping biomaterials are placed as a protective layer on the exposed vital pulp on the floor of deep cavi- ties after removal of deep carious lesions or after traumatic exposure. These protective biomaterials should possess specific bioproperties like biocompatibility, biointerac- tivity (ion-releasing – i.e., release of biologically relevant ions) and bioactivity (apatite-forming ability) to promote pulp cell activity and the formation of new reparative dentin. Calcium hydroxide, initially proposed in 1930 as a “remineralizing agent” in direct pulp capping (1), plays a key role in the biological events of reparative dentinogen- esis when in close proximity to pulp tissues, due to the re- lease of calcium (Ca) and hydroxyl (OH) ions. An influx of