Biomechanical and histological evaluation of the osseointegration capacity of two types of zirconia implant

International Journal of Nanomedicine Dovepress open access to scientific and medical research O r i g in a l R e s e a r c h International Journal of Nanomedicine downloaded from https://www.dovepress.com/ by 213.32.98.221 on 12-Jul-2018 For personal use only. Open Access Full Text Article Biomechanical and histological evaluation of the osseointegration capacity of two types of zirconia implant This article was published in the following Dove Press journal: International Journal of Nanomedicine 7 December 2016 Number of times this article has been viewed Jian-min Han 1,2 Guang Hong 3 Hong Lin 1 Yoshinaka Shimizu 4 Yuhan Wu 2 Gang Zheng 1 Hongyu Zhang 5 Keiichi Sasaki 2 Department of Dental Materials, National Engineering Laboratory for Digital and Material Technology of Stomatology, Peking University School and Hospital of Stomatology, Beijing, People’s Republic of China; 2 Division of Advanced Prosthetic Dentistry, 3Liaison Center for Innovative Dentistry, 4Department of Oral Pathology, Graduate School of Dentistry, Tohoku University, Sendai, Japan; 5State Key Laboratory of Tribology, Department of Mechanical Engineering, Tsinghua University, Beijing, People’s Republic of China 1 Abstract: The purpose of this study was to evaluate the biomechanical and histological behavior of a ceria-stabilized zirconia–alumina nanocomposite (NanoZr) in comparison with that of 3 mol% yttria-stabilized tetragonal zirconia polycrystalline (3Y-TZP) in Sprague Dawley rats. Cylindrical NanoZr and 3Y-TZP implants (diameter 1 mm, length 2 mm) were used. Implantsurface morphology and surface roughness were determined by scanning white-light interferometry and scanning electron microscopy, respectively. The cylindrical zirconia implants were placed at the distal edge of the femur of Sprague Dawley rats. At weeks 2, 4, and 8, the interfacial shear strength between implant and bone was measured by push-in test. Histological analysis was performed using hard-tissue sections. Bone–implant contact (BIC), the thickness of new bone around the implant within the bone marrow area, and osteoclast numbers were evaluated. The average surface roughness of 3Y-TZP (Sa 0.788 µm) was significantly higher than that of NanoZr (Sa 0.559 µm). The shear strengths of 3Y-TZP and NanoZr were similar at 2 weeks, but at 4 and 8 weeks the shear strength of NanoZr was higher than that of 3Y-TZP. The average BIC values within the bone marrow area for 3Y-TZP and NanoZr were 25.26% and 31.51% at 2 weeks, 46.78% and 38% at 4 weeks, and 47.88% and 56.81% at 8 weeks, respectively. The average BIC values within the cortical area were 38.86% and 58.42% at 2 weeks, 66.82% and 57.74% at 4 weeks, and 79.91% and 78.97% at 8 weeks, respectively. The mean BIC value did not differ significantly between the two zirconia materials at any time point. The NanoZr implants were biocompatible, capable of establishing close BIC, and may be preferred for metal-free dental implants. Keywords: zirconia, dental implant, zirconia–alumina nanocomposite, push-in test, histomorphometry Introduction Correspondence: Guang Hong Liaison Center for Innovative Dentistry, Graduate School of Dentistry, Tohoku University, 4-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan Tel/fax +81 22 717 8278 Email 6507 submit your manuscript | www.dovepress.com International Journal of Nanomedicine 2016:11 6507–6516 Dovepress © 2016 Han et al. This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License (http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms (https://www.dovepress.com/terms.php). http://dx.doi.org/10.2147/IJN.S119519 Powered by TCPDF (www.tcpdf.org) Zirconia ceramics were introduced to dentistry more than two decades ago. In addition to its use for crown and bridge construction, there is considerable interest in the use of zirconia in implant dentistry.1,2 Due to its outstanding mechanical properties, stable physical and chemical properties, and excellent biocompatibility, it can offset the grayish appearance of gingiva3–5 and the potential hypersensitivity of titanium metal implants.6–9 Metal-free dental zirconia implants are thus of considerable interest. Most of the zirconia used in implant dentistry is in the form of 3 mol% yttriastabilized tetragonal zirconia polycrystalline (3Y-TZP). Various studies have verified that 3Y-TZP induces no or a slight inflammatory reaction and protein adsorption, osteoblast/osteoblast-like cell attachment, spreading, proliferation, differentiation, bone–implant contact (BIC) rates, and bone–implant bond strength (push-in Dovepress International Journal of Nanomedicine downloaded from https://www.dovepress.com/ by 213.32.98.221 on 12-Jul-2018 For personal use only. Han et al or torque-out test), similarly to titanium implants.10–15 The flexural strength of 3Y-TZP is 900–1,200 MPa, and its fracture toughness is 8–10 MPa⋅m½.16 The static fracture strength of a 3Y-TZP implant is 725–850 N, which is within the limits of acceptability for clinical implant dentistry.17 However, zirconia implants have a high risk of fracture. Gahlert et al18 reported that the failure rate of zirconia implants approached 10% after 20–50 months (average 36.75 months) of prosthetic loading, and Osman et al19 reported a 4.1% fracture rate of zirconia implants after 1 year of follow-up; in contrast, titanium dental implants rarely fracture.20 Fracture of dental zirconia implants may be associated with their lower physical and mechanical properties and low-temperature aging degradation and/or stress fatigue. Therefore, a highly reliable metal-free material with greater strength and toughness and enhanced resistance to fatigue and low-temperature aging degradation is required for use in dental implants. A Ce-TZP-based nanostructured zirconia–alumina composite (NanoZr) composed of 10 mol% cerium dioxide (CeO2)-stabilized TZP as a matrix and 30 vol% of Al2O3 as a second phase was developed by Nawa et al.21,22 Due to its unique intergranular type of nanostructure, in which several 10–100 nm Al2O3 particles are trapped within the ZrO2 grains and several 10 nm ZrO2 particles are trapped within the Al2O3 grains, the flexural strength and fracture toughness of NanoZr are 1,500 MPa and 18 MPa⋅m½, respectively.16 It shows complete resistance to low-temperature aging degradation in comparison with Y-TZP.11,16 Additionally, the cyclic fatigue strength of NanoZr is twice that of 3Y-TZP.23 Our previous study showed that NanoZr has cell attachment comparable to that of 3Y (...truncated)