Characterization of Wet Powder-Sprayed Zirconia/ Calcium Phosphate Coating for Dental Implants Karoline Pardun, Dipl. Biol.;* Laura Treccani, Dr. rer. nat; † Eike Volkmann, MSc; ‡ Giovanni Li Destri, PhD; § Giovanni Marletta, MSc; ¶ Philipp Streckbein, MD, DDS;** Christian Heiss, MD, PhD; †† Kurosch Rezwan, Dr. Ing ‡‡ ABSTRACT Purpose: Yttria-stabilized zirconia (TZ) is used for dental applications because of its low toxicity and beneficial mechanical properties, but it does not stimulate bone regeneration around the implant due to its bioinertness. Therefore, hydroxya- patite (HA) coatings are often utilized to increase the surface bioactivity and to achieve a better osseointegration. These coatings, however, are chemically nonstable and provide a weak bonding to the substrate surface. Materials and Methods: In this study, zirconia substrates were coated with a calcium phosphate/zirconia mixture to achieve ceramic coatings with a high bioactivity potential and a good mechanical stability.The coatings were obtained by wet powder spraying (WPS). Pure HA and TZ coatings were employed as reference materials. The coatings were characterized with regard to microstructure, surface roughness, and phase composition. Scratch tests were carried out to investigate the coating adhesion. The influence of the coating on the mechanical strength was evaluated with the ball on three balls test (B3B). In addition, zirconia dental implant screws were also coated and inserted in a biomechanical test block and bovine rip bone. Results: After sintering, the mixed coating exhibited a porous morphology with a surface roughness of about 4 mm and a total porosity of 17%. Phase analysis showed a transformation from TZ and HA to calcium zirconium oxide and tricalcium phosphate. Investigations of the bond strength confirmed a strong adhesion of the mixed coating to the substrate, while the biaxial fracture strength was only slightly affected. Insertion experiments confirmed the scratch test results and evidenced an intact mixed coating on the zirconia screw. Conclusions: The present study revealed a higher stability and firm adhesion of the mixed coating compared with a pure calcium phosphate coating. We also successfully demonstrate the particular versatility of the WPS technique for dental implants by coating a complex curved surface. KEY WORDS: coating adhesion, dental implants, hydroxyapatite, wet powder spraying, zirconia INTRODUCTION The material surface features and composition of ortho- pedic and dental implants play a crucial role for proper bone tissue interaction. Today, titanium or titanium alloys represent standard materials for dental applica- tions because of their biocompatibility and favorable mechanical properties. 1 Yttria-stabilized zirconia (TZ), on the other hand, is used in the biomedical field due to its low toxicity and beneficial mechanical properties, like high bending strength, fracture toughness, and hardness, compared with metals and other ceramics. Although TZ is known for its good biocompatibility, it does not stimulate extensive bone regeneration around the implant because of its bioinertness. 2–7 However, lack of material integration in the surrounding bone can *Research associate, Advanced Ceramics, University of Bremen, Bremen, Germany; † senior scientist, Advanced Ceramics, University of Bremen, Bremen, Germany; ‡ research associate, Advanced Ceramics, University of Bremen, Bremen, Germany; § postdoctoral researcher, Department of Chemical Sciences, University of Catania, Catania, Italy; ¶ professor, Department of Chemical Sciences, University of Catania, Catania, Italy; ** senior consultant, Department of Cranio- Maxillo-Facial Surgery, University Hospital, Justus-Liebig-University Giessen, Giessen, Germany; †† vice head, Department of Trauma Surgery, University Hospital of Giessen-Marburg, Giessen, Germany, and Laboratory of Experimental Surgery, Giessen, Germany; ‡‡ profes- sor, Advanced Ceramics, University of Bremen, Bremen, Germany Reprint requests: Prof. Kurosch Rezwan, Advanced Ceramics, Univer- sity of Bremen, Am Biologischen Garten 2, 28359 Bremen, Germany; e-mail: krezwan@uni-bremen.de The authors declare no conflicts of interest © 2013 Wiley Periodicals, Inc. DOI 10.1111/cid.12071 1