The Effects of Syndecan on Osteoblastic Cell Adhesion Onto Nano-Zirconia Surface

Effect of the connection structure of zirconia dental implants on biomechanical properties

The connection structure of zirconia dental implants significantly influences their biomechanical behavior and plays a crucial role in the overall service performance of the implant system. This study aims to compare the stress distribution of zirconia implants featuring various internal connection structures under different working conditions. Four distinct types of connection structures were designed for zirconia dental implants: triangular, quadrilateral, hexagonal, and hexalobular plus connections. Additionally, the finite element method was employed to analyze these structures under three working conditions: a static load test model, a bone level model, and a torsion model. Results indicated that in the static load test model, the hexagonal structure experienced the highest stress value at 1284.9 MPa due to its thin neck wall, whereas the hexalobular plus connected implant exhibited the lowest stress value at 1252.9 MPa. In the bone level model, the triangular connection structure demonstrated poor stress distribution for cortical bone and cancellous bone at 69.606 MPa and 7.8191 MPa, respectively. Conversely, the hexalobular plus connection yielded superior stress results for cortical bone and cancellous bone, with values of 66.24 MPa and 5.1327 MPa, respectively. In the torsion model, the hexalobular plus-connected implant exhibits the highest stress value at 237.6 MPa, while maintaining the smallest force transmission angle. Therefore, given that the abutment necessitates a greater range of installation angles and improved torque transmission, the hexalobular plus connection structure may represent the optimal choice.

Antibacterial Zirconia Surfaces from Organocatalyzed Atom-Transfer Radical Polymerization

Antibacterial coatings are becoming increasingly attractive for application in the field of biomaterials. In this framework, we developed polymer coating zirconia with antibacterial activity using the "grafting from" methodology. First, 1-(4-vinylbenzyl)-3-butylimidazolium chloride monomer was synthesized. Then, the surface modification of zirconia substrates was performed with this monomer via surface-initiated photo atom transfer radical polymerization for antibacterial activity. X-ray photoelectron spectroscopy, ellipsometry, static contact angle measurements, and an atomic force microscope were used to characterize the films for each step of the surface modification. The results revealed that cationic polymers could be successfully deposited on the zirconia surfaces, and the thickness of the grafted layer steadily increased with polymerization time. Finally, the antibacterial adhesion test was used to evaluate the antibacterial activity of the modified zirconia substrates, and we successfully showed the antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa strains.

Promoted Abutment-Soft Tissue Integration Around Self-Glazed Zirconia Surfaces with Nanotopography Fabricated by Additive 3D Gel Deposition

Introduction

Improving the biological sealing around dental abutments could promote the long-term success of implants. Although titanium abutments have a wide range of clinical applications, they incur esthetic risks due to their color, especially in the esthetic zone. Currently, zirconia has been applied as an esthetic alternative material for implant abutments; however, zirconia is purported to be an inert biomaterial. How to improve the biological activities of zirconia has thus become a popular research topic. In this study, we presented a novel self-glazed zirconia (SZ) surface with nanotopography fabricated by additive 3D gel deposition and investigated its soft tissue integration capability compared to that of clinically used titanium and polished conventional zirconia surfaces.

Materials and Methods

Three groups of disc samples were prepared for in vitro study and the three groups of abutment samples were prepared for in vivo study. The surface topography, roughness, wettability and chemical composition of the samples were examined. Moreover, we analyzed the effect of the three groups of samples on protein adsorption and on the biological behavior of human gingival keratinocytes (HGKs) and human gingival fibroblasts (HGFs). Furthermore, we conducted an in vivo study in which the bilateral mandibular anterior teeth of rabbits were extracted and replaced with implants and corresponding abutments.

Results

The surface of SZ showed a unique nanotopography with nm range roughness and a greater ability to absorb protein. The promoted expression of adhesion molecules in both HGKs and HGFs was observed on the SZ surface compared to the surfaces of Ti and PCZ, while the cell viability and proliferation of HGKs and the number of HGFs adhesion were not significant among all groups. In vivo results showed that the SZ abutment formed strong biological sealing at the abutment-soft tissue interface and exhibited markedly more hemidesmosomes when observed with a transmission electron microscope.

Conclusion

These results demonstrated that the novel SZ surface with nanotopography promoted soft tissue integration, suggesting its promising application as a zirconia surface for the dental abutment.

Family with sequence similarity 20 member B regulates osteogenic differentiation of bone marrow mesenchymal stem cells on titanium surfaces

Successful bone regeneration on titanium (Ti) surfaces is a key process in dental implant treatment. Bone marrow mesenchymal stem cells (BMSCs) are fundamental cellular components of this process, and their early recruitment, proliferation, and differentiation into bone-forming osteoblasts are crucial. A proteoglycan (PG)-rich layer has been reported to exist between Ti surfaces and bones; however, the molecules that could potentially affect the formation of this layer remain unknown. Family with sequence similarity 20 member B (FAM20B) is a newly identified kinase that regulates the synthesis of glycosaminoglycans, an important component of the PG-rich layer. Because FAM20B is also closely associated with bone development, in this study, we examined the function of FAM20B in osteogenic differentiation of BMSCs on Ti surfaces. For this, BMSC cell lines with knocked down FAM20B (shBMSCs) were cultured on Ti surfaces. The results showed that the depletion of FAM20B reduced the formation of a PG-rich layer between the Ti surfaces and cells. The shBMSCs exhibited downregulated expression of osteogenic marker genes (ALP and OCN) and decreased mineral deposition. Moreover, shBMSCs reduced the molecular levels of p-ERK1/2, which plays an important role in MSC osteogenesis. The nuclear translocation of RUNX2, an important transcription factor for osteogenic differentiation, on the Ti surfaces is inhibited by the depletion of FAM20B in BMSCs. Moreover, the depletion of FAM20B reduced the transcriptional activity of RUNX2, which is important in regulating the expression of osteogenic genes. STATEMENT OF SIGNIFICANCE: Bone healing and regeneration on implanted titanium surfaces is a cell-material interaction. Such an interaction is enabled by bone marrow mesenchymal stem cells (BMSCs), and their early recruitment, proliferation, and differentiation into bone-forming osteoblasts are essential for bone healing and osseointegration. In this study, we found that the family with sequence similarity 20-B influenced the formation of a proteoglycan rich layer between BMSCs and the titanium surface and regulated the differentiation of BMSCs into bone-forming osteoblasts. We believe that our study contributes significantly to the further exploration of bone healing and osseointegration mechanisms on implanted titanium surfaces.