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ePaper created 2017-11-09, 09:28:26 | version 1.38.0
technology | Fig. 2 Fig. 1 Figs. 1 & 2: DORA 14801 provides in-house testing of dental implants according to ISO 14801. Ceramics in implant dentistry Due to the possible negative effects of titanium, as well as the positive features of ceramics, the clinical applica- tion of implants made from different novel ceramic bio- materials has become more active. Such ceramic mate- rials include single- and poly-crystal alumina23, bioactive glasses24, hydroxyapatite25, and zirconia26. Furthermore, zirconium oxide coatings (approximately 100 nm) of Ti6AI4V, or titanium orthopaedic implants, usually after the application of macro-texturing methods, may pro- mote bone growth and thus provide evidence of en- hanced implant osseointegration.27, 28 Y-TZP is currently considered an attractive and advantageous endosse- ous dental implant material due to its high biocompati - bility, improved mechanical features, high radiopacity, and easy handling during abutment preparation.29, 30 Zirconia ceramic is well-tolerated by bone- and soft-tis- sues and possesses mechanical stability.31 Since the dif- ference in bone-to-implant attachment strength between bio-inert ceramics and stainless steel was not signif- icant, it was indicated that the affinity of bone to bio- inert ceramics has almost the same capacity as metal alloys.32 In vitro culture tests were performed to verify biocompatibility, genetic effects, and osteoblast interac- tions of potential zirconia implant substrates. A series of well-reviewed studies showed no adverse response, sur- face-specific and non-surface-specific proliferation, at- tachment and spreading of osteoblasts, and no genetic effect of zirconia on bone formation.33–36 Animal studies that focused on zirconia implants with- out loading demonstrated comparable qualitative and quantitative characteristics to that of the titanium im- plants in biocompatibility and osteoinductivity.37, 38 In vivo studies proved that micro-modification of Y-TZP im- plants, resulting in a roughened surface, was beneficial for initial bone healing, bone apposition, and interfacial shear strength.39 Different studies were performed to define the feasibility of zirconia implant systems. A finite element assessment of the loading resistance revealed non-distractive and well-distributed stress patterns, sim- ilar to those of titanium implants.40 Regarding the impact of the design (one or two pieces) on the biomechanical behaviour of Y-TZP implants using chewing simulation testing conditions, a prototype two- piece zirconia implant revealed low fracture resistance at the level of the implant head and therefore questionable clinical performance,41 while one-piece zirconia implants seem to be clinically applicable. More recently, Schepke et al. (2017) conducted a study to describe the histologic and histomorphometric features of a functional endos- seous Y-TZP implant in a human subject.42 It was shown that the histologic data provided further evidence of the potential of such implants to osseointegrate to a similar degree as titanium in humans. To date, there are several commercially available zirco- nia implant systems on the market.43 Some provide both one- and two-piece designs and the others provide only one-piece designs. Despite some promising preliminary clinical results, no clinical long-term data are available concerning zirconia implants. Survival rates after one year were reported at 93 per cent (189 one-piece im- plants, Z-Systems)44, 98 per cent (66 one-piece implants, Z-Systems)26, and 100 per cent (one-piece implants, implants 1 2017 35