Sol–gel derived bioactive coating on zirconia: Effect on flexural strength and cell proliferation Khalil Shahramian, 1,2 Heidi Leminen, 3 Ville Meretoja, 1 Paula Linderb€ ack, 2 Ilkka Kangasniemi, 2 Lippo Lassila, 2,4 Aous Abdulmajeed, 1,2,5 Timo N€ arhi 1,2,3 1 Department of Prosthetic Dentistry and Stomatognathic Physiology, Institute of Dentistry, University of Turku, FI-20520 Turku, Finland 2 Turku Clinical Biomaterials Center (TCBC), University of Turku, 20520 Turku, Finland 3 Clinic of Oral Diseases, Turku University Central Hospital, FI-20520 Turku, Finland 4 Department of Biomaterials Science, Institute of Dentistry, University of Turku, FI-20520 Turku, Finland 5 Department of General Practice, School of Dentistry, Virginia Commonwealth University, Richmond, Virginia Received 7 June 2016; revised 6 August 2016; accepted 14 August 2016 Published online 00 Month 2016 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.b.33780 Abstract: The purpose of this study was to evaluate the effect of sol–gel derived bioactive coatings on the biaxial flexural strength and fibroblast proliferation of zirconia, aimed to be used as an implant abutment material. Yttrium stabilized zirco- nia disc-shaped specimens were cut, ground, sintered, and finally cleansed ultrasonically in each of acetone and ethanol for 5 minutes. Three experimental groups (n 5 15) were fabri- cated, zirconia with sol–gel derived titania (TiO 2 ) coating, zirco- nia with sol–gel derived zirconia (ZrO 2 ) coating, and non- coated zirconia as a control. The surfaces of the specimens were analyzed through images taken using a scanning elec- tron microscope (SEM), and a non-contact tapping mode atomic force microscope (AFM) was used to record the surface topography and roughness of the coated specimens. Biaxial flexural strength values were determined using the piston-on- three ball technique. Human gingival fibroblast proliferation on the surface of the specimens was evaluated using AlamarBlue assay TM . Data were analyzed using a one-way analysis of variance (ANOVA) followed by Tukey’s post-hoc test. Additionally, the biaxial flexural strength data was also statistically analyzed with the Weibull distribution. The biaxial flexural strength of zirconia specimens was unaffected (p > 0.05). Weibull modulus of TiO 2 coated and ZrO 2 coated groups (5.7 and 5.4, respectively) were lower than the control (8.0). Specimens coated with ZrO 2 showed significantly lower fibroblast proliferation compared to other groups (p < 0.05). In conclusion, sol–gel derived coatings have no influence on the flexural strength of zirconia. ZrO 2 coated specimens showed significantly lower cell proliferation after 12 days than TiO 2 coated or non-coated control. V C 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 00B: 000–000, 2016. Key Words: dental implant, zirconia, bioactive coating, sol– gel, flexural strength How to cite this article: Shahramian K, Leminen H, Meretoja V, Linderb€ ack P, Kangasniemi I, Lassila L, Abdulmajeed A, N€ arhi T. 2016. Sol–gel derived bioactive coating on zirconia: Effect on flexural strength and cell proliferation. J Biomed Mater Res Part B 2016:00B:000–000. INTRODUCTION For the past decades, titanium has been the material of choice in oral implantology, taking advantage of its inert and biocom- patible properties. 1 However, extensive research has been con- ducted to optimize the properties of titanium oral implants for better clinical success. An important property that plays a cru- cial role in the long-term success of implants is their ability to attach to surrounding soft-tissue creating a peri-implant seal. Problems like peri-implantitis or even implant loss may arise as a result of migration of oral bacteria along the implant surface due to the lack of a bond between the implant and the oral mucosa. 2–6 To overcome this, a variety of techniques and surface treatments have been introduced. Sol–gel derived titania (TiO 2 ) coatings are one of the surface treatments that have shown improved soft tissue attachment. They possess the advantages of having a simple production process that can be readily depos- ited on geometrically difficult surfaces and have the possibility to incorporate biologically active molecules. 7 These coatings are also favored by the lack of formation of a fibrous capsule, which if formed, will eventually lead to movements at the implant- tissue interface. 6–10 With the shift in material development in prosthetic den- tistry toward metal-free restorations, zirconia abutments are found as an alternative to titanium. Zirconia has superior esthetic properties and has the capacity to be colored. 11,12 In addition, the toughening mechanisms occurring within the structure of zirconia, its high bending strength, fairly high hardness, and Young’s modulus in the same order of magni- tude of stainless steel alloys (approximately 210 GPa), all give the material additional advantages and interest for use in Correspondence to: K. Shahramian; e-mail: khalsha@utu.fi Conflict of Interest: The authors declare no conflict of interest with any of the products used in this project. V C 2016 WILEY PERIODICALS, INC. 1