Clinical Evaluation Of Implant-supported Zirconium Oxide Ceramic Restorations In Posterior Area

Alone with the development of oral material, Zirconium oxide ceramic gradually takeplace of porcelain-fused-to-metal (PFM) and aluminum oxide alike and becomes the vastdevelopment prospective biomaterial in recent years. Zirconium oxide has highmechanical strength with flexural strength of900-1200Mpa and compressive strength of2000Mpa. Furthermore, Zirconia is also widely used in clinic because of the variousfeatures of stable chemical properties, biocompatibility, precise manufacturing, highstrength, no influencing on magnetic resonance imaging (MRI). Zirconia has outstandingaesthetic advantages when used in anterior area. But the clinical performance would beaffected by complications related to ceramic when reparing the posterior. So far, whetherzirconia is recommended to use in the posterior regions of the mouth does not reach anagreement. Especially in the field of implantology, relavant clinical research is rare.If in the position of high occlusal force, the risk of mechanical complications ofzirconium ceramic prosthesis would increase during long-term circular loading without theprocess of adapting to occlusion because of its intrinsic rigidity. In addition, since thetissue similar to periodontal ligament doesn’t exist around the implant, the force loadingon the implant can not be buffered. These conditions may lead to the peri-implant bonelevel change under the stress. For these reason, it is an issue worth studying that theclinical outcome and the influence of zirconia restoration on peri-implant tissue health. Part I Clinical outcome of implant-supported zirconium oxide ceramic restorationsin posterior areaObjectivesThis study retrospectively evaluated the clinical performance of implant-supportedzirconium oxide ceramic restorations in posterior area through analyzing clinical andradiographic data.MethodsThe clinical and radiographic data of323patients with implant-supported zirconiumoxide ceramic restorations were collected during the period July2011to June2012.Information was available for387prosthesis and525implants. The clinical items,including prosthesis integrity, marginal fit, modified sulcus bleeding index(mSBI),modified plaque index(mPLI), probing depth(PD) were examined. The cumulativesurvival rate(CSR) of implant and performance of prosthesis was investigated. SPSS18.0was applied to analyze the data.Results264(81.7%) patients, which contains315(81.4%) prosthesis and423(80.1%) implants,were examined after a mean observation period of18.8±3.8months. CSR of implants is100%. During the observation period, mechanical complications including24(9.1%)chipping of veneering porcelain and1(0.3%)loss of retention were observed. Nomechanical complication of implants was recorded. The average mSBI is0.45±0.78(0～3). The average mPLI is0.35±0.73(0～2). The average PD is2.74±1.08mm(1～7mm).14(3.3%)implants suffered peri-implant mucositis.ConclusionsThe implant-supported zirconium oxide single crown in posterior area showed goodclinical results and can be used as material repairing single missing tooth in posteriorimplant insertion areas. But zirconia prosthesis without veneering porcelain should berecommended to apply clinically in multi-unit tooth missing because of high mechanicalability. Part II Clinical research of influence of implant-supported zirconium oxideprostheses in posterior area on peri-implant marginal bone loss (MBL)ObjectivesThe purpose of this experiment is to discuss influence of relative loading factors ofimplant-supported zirconium oxide prosthesis on MBL.MethodsThe clinical and radiographic data of323patients with implant-supported zirconiumoxide ceramic restorations were collected during the period July2011to June2012.Information was available for387prosthesis and525implants. The vertical distancebetween peri-implant marginal bone level and abutment level was measured at the time ofprosthesis installation and follow-up respectively. The value of MBL wasobtained. Multiple linear regression was applied to analyze factors of MBL.ResultsThe average MBL is0.28±0.35mm (0~1.97mm) from1-year after implant loading tofollow-up. Significant differences in MBL among opposing natural teeth and that ofopposing implant-supported restoration (P=0.030)were found. Significant difference inMBL is also showed between implant-supported single crown(SC) and double-unitcrown(P=0.023).These differences may influenced by other factors, including the positionand brand of implants, occurrence of chipping, history of periodontitis, and so on.ConclusionsExcessive marginal bone loss did not occurred around implants under the loading ofzirconia prostheses.Different opposing structure and implant restoration have effect onMBL. MBL of implant-supported double-unit crown was higher than that ofimplant-supported single crown when they were in maxillary molar or bleeding onprobing. MBL of implant with opposing implant-supported restoration was higher thanthat of implant with opposing natural teeth when they were in maxillary.