| Titanium has been considered as "gold standard" for dental implants and impalnt abutments because of its excellent biocompatibility. Howerver, there are many practical problems, which is a limitation for its clinical application. Owing to the exposure of metal color, titanium abutments have poor esthetic outcomes in those patients whose gingiva is thin or the shoulder of implants are shallow. Recently, with the improvement of living standard and the development of dental implantology, both clinicians and patients have more and more requests on esthetic restorations, especially involving the maxillary anterior implants. ZrO2ceramic abutments are becoming more and more popular with clinicians and patients due to the excellent esthetic properties. Howerver, compared with titanium abutments, little is known about the effects of ZrO2ceramic abutments on peri-implant soft tissues. Therefore, the study will contribute to a better understanding of the effects of ZrO2ceramic abutments on peri-implant soft tissues according to the following three parts.Part I The Study of Oral Bacterial Colonization on Zirconium Dioxide and Titanium Surfaces1. Adhension Properties of Oral Pathogenic Bacteria on Zirconium Dioxide and Titanium Surfaces:An in Vitro StudyZrO2and Ti samples were fabricated and polished using silicon carbide abrasive paper. Samples from each group were used to evaluate topographic pattern under SEM and AFM. Samples from each group were evaluated roughness using profilometer and contact angles. SEM was used to observe the adhesive efficacy of Pg and Ss qualitatively. MTT assays were applied to count the quantity of Pg and Ss adhered to ZrO2and Ti surfaces in4h. The surfaces topographies were similar of ZrO2and Ti samples, but ZrO2surfaces were smoother than Ti surfaces. SEM observation showed that fewer Pg and Ss were adhered on ZrO2surfaces than Ti surfaces. The quantities of Pg adhered to ZrO2in4h were significant lower than Ti surfaces. The quantities of Ss adhered to ZrO2and Ti surfaces in4h were similar.2. Confocal Laser Scanning Microscope Evaluation of Early Bacterial Colonization on Zirconium Dioxide and Titanium Surfaces:An in Vivo StudySamples of ZrO2and Ti were fabricated and polished using silicon carbide abrasive paper. Samples from each group were evaluated topographic pattern under SEM and AFM. Samples from each group were to evaluate roughness using profilometer and contact angles. Eight volunteers were selected in this study. The samples were cemented at the buccal surfaces of maxillary first molars. All samples were removed after48h, immersed in SYTO-9and propidium iodide (PI) fluorescent to stain for adherent bacteria and observed with CLSM. Fewer bacteria were observed in ZrO2group thanTi group. However, there was no statistical difference between two groups.Part Ⅱ The Influence of Human Gingival Fibroblast Biological Bahavior on Zirconium Dioxide and Titanium Surfaces3. Attachment, Proliferation and Gene Expression of Human Gingival Fibroblast on Zirconium Dioxide and Titanium SurfacesZrO2and Ti disks were fabricated and polished using silicon carbide abrasive paper. Samples from each group were used to evaluate topographic pattern under SEM and AFM. Samples from each group were evaluated roughness using profilometer and contact angles. After primary HGFs were seeded on these disks, cell morphology was examined by SEM at3h,6h,12h and24h. Cell proliferation was evaluated by a CCK-8kit and Acrodine orange (AO) at1d,3d and5d. Gene expression levels of various integrins, collagens and fibronectin were measured by real-time PCR. The surfaces topographies were similar of ZrO2and Ti disks, but ZrO2surfaces were smoother than Ti surfaces. HGF seeded on ZrO2surfaces appeared to be more aligned at24h. With respect to proliferation, HGF proliferated faster on ZrO2surfaces than Ti surfaces, but there were no statistical differences. The expression levels of integrin as and β3at24h on ZrO2surfaces were inhibited compared to Ti. Conversely, the expression levels of collagen Ⅰ and collagen Ⅲ at24h on ZrO2surfaces was up-regulated compared to Ti. The expression level of fibronectin was similar on both ZrO2and Ti surfaces.4. Human Gingival Fibroblast Response to Zirconium Dioxide and Titanium Surfaces after Exposed to LipopolysaccharideZrO2and Ti disks were fabricated and polished using silicon carbide abrasive paper. Samples from each group were evaluated topographic pattern under SEM and AFM. Samples from each group were used to evaluate roughness using a profilometer and contact angles. After primary HGFs were seeded on these disks, HGFs were exposed to1-20μg/ml LPS for24h, the RNA were collected. HGFs were also exposed to10μg/ml LPS from1h to12h and the RNA were collected. The gene expression of TNF-a and IL-1β secreted by HGF on ZrO2and Ti surfaces were analysed by real-time PCR. Gene expressions of TNF-a and IL-1β were up-regulated by LPS in dose depedent manner and time depedent manner. The mRNA expresion levels of TNF-a on ZrO2surfaces were significant lower than Ti after6h, and the differences were more significant when HGFs were exposed to LPS at12h.Part Ⅲ Soft Tissue Response to Zirconium Dioxide and Titanium Healing Abutments:A Study in Dogs5. Comparison of Inflammatory Mediators in Peri-implant Crevicular Fluid around Zirconium Dioxide and Titanium Healing Abutments:A Study in DogsThe third and fourth mandibular premolars and the first mandibular molar of three Beagle dogs were extracted bilaterally. Eight implants were inserted each dog after healing. Two months later, the ZrO2and Ti healing abutments were connected. Two weeks later, PICF were collected as the initial time. Then ligatures were placed around the neck of healing abutments unilaterally to induce inflammation. PICF were collected again after four weeks. The volume of PICF and inflammatory mediators, ALP, AST, TNF-a and IL-1β in PICF around ZrO2and Ti healing abutments were analyzed. The volumes of PICF around ZrO2and Ti healing abutments in ligation sides were higher than non-ligation sides after ligation. The volume of PICF around ZrO2healing abutments in ligation sides was higher than that of Ti healing abutments after ligation. The levels of ALP and AST in PICF around ZrO2healing abutments were lower than those of Ti healing abutments in both sides of ligation and non-ligation. The levels of TNF-a and IL-1β in PICF in ligation side were higher than non-ligation sides. The level of TNF-a in PICF around ZrO2healing abutments were higher than that of Ti healing abutments in ligation sides, while the levels of IL-1β in PICF around ZrO2healing abutments were lower than that of Ti healing abutments in ligation sides. However, there were no statistical differences.6. Clinical Indices and Histological Observation of Soft Tissues to Zirconium Dioxide and Titanium Healing Abutments:A Study in DogsThe models of ZrO2and Ti healing abutments were constructed with three Beagle dogs as described in study5. The periodontal indices of GI, PI and PPD were evaluated. Histological observation was used to evaluate the inflammatory cells inflitration around ZrO2and Ti healing abutments in both ligation and non-ligation sides. The results showed that GI of ligation sides were significant higher than non-ligation sides. There were no differences of PI. PPD in ZrO2ligation sides was deeper than ZrO2non-ligation sides. The result of HE staining showed that the inflammation cells were concentrated in the soft tissues around healing abutments in ligation sides. The immunohistochemistry of TNF-a and IL-1β revealed that inflammation cells were expressed at the basement memberane zone, soft tissues around ZrO2and Ti healing abutments and endothelial cells of vessels in the vicinity. The were no statistical differences of the amount of inflammation cells around ZrO2healing abutments and Ti healing abutments both in ligation sides and non-ligation sides. |
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