[Osteoblast reaction on SLA and microgrooved implant surfaces]

In Vitro Effect of Modified Polyetheretherketone (PEEK) Implant Abutments on Human Gingival Epithelial Keratinocytes Migration and Proliferation

Improving soft tissue attachment to implant abutments is a crucial factor for enduring health and maintenance of soft peri-implant tissue health. In this in vitro study we aimed to compare the biocompatibility of three different abutment surfaces: titanium, zirconia and modified polyetheretherketone (PEEK). Surface topography, roughness and wettability were investigated with scanning electron microscopy, profilometer and contact angle meter, respectively. Human gingival epithelial keratinocytes were examined for viability, morphology, proliferation and migration by using tetrazolium salt colorimetric assay, scanning electron microscopy imaging, immunofluorescence bromodeoxyuridine analysis and scratch wound healing assays. Roughness measurements revealed differences between the investigated surfaces. Keratinocytes cultured on all examined surfaces indicated adhesion and attachment by means of scanning electron microscopy imaging. Cell viability assays showed no significant differences between the groups (p > 0.05). The modified PEEK surface similarly improved surface roughness in comparison to titanium and zirconia, which resulted in greater and equivalent cell proliferation and migration. The study methodology showed here may emphasize the importance of cell interactions with different abutment materials, which in part increases the changes of implant success. PEEK, titanium and zirconia surface types used in this study showed mostly similar epithelial biological responses.

Dynamic behavior of different quantities of osteoblasts during formation of micromass cultures

Implantation of micromass cultures of osteoblastic cells offers the possibility of scaffold free tissue engineering for example, regeneration of bone defects. However, the details of cell dynamics during the formation of these micromasses are still not well understood. This study aims to investigate and clarify the extent to which cell quantity influences the dynamics of micromass formation of osteoblastic cell cultures. For this purpose, the migration and aggregation during this process are investigated by optical inspection employing image processing software that allows for automated tracking of cell groups using digital image correlation. An exponential time behavior is observed with respect to the velocity of the cells and the distance of the cells to their common center of gravity. Characteristic time constants are derived as quantitative measures of the cell dynamics. The results indicate that the time constants strongly depend on the quantity of cells, that is, will decrease with increasing cell quantity. © 2018 International Society for Advancement of Cytometry.

A histological study of mineralised tissue formation around implants with 3D culture of HMS0014 cells in Cellmatrix Type I-A collagen gel scaffold in vitro

We cultured HMS0014 Yub621b cells within a 3D collagen gel scaffold (Cellmatrix Type I-A) and aimed to study the fate and contribution of human bone-derived mesenchymal stem cells (MSCs) in the guided bone regeneration(GBR)-engineered tissue which has developed around the titanium (Ti) test dental implant (IP) in vitro. The light microscopy (LM) and transmission electron microscopy (TEM) results of the peri-IP tissue indicated that collagen fibrils of the Cellmatrix Type I-A gel were accumulated and fabricated to provide a 3D meshwork for proliferation and differentiation of the HMS0014 cells in the top (cell) layer; mineralisation of the GBR tissue had commenced since day 1 and became markedly deposited between days 7 and 14 of the experiment. TEM observation revealed sedimentation of cement line at the periphery of the interwoven Cellmatrix fibres and fibrils in the ECM scaffold of the GBR tissue; matrix vesicle-mediated and appositional collagen-mediated mineralisation were identified in the peri-IP ECM scaffold. The fine structure study of the plurimorphic osteoblast(Ob)-like osteogeneic cells demonstrated numerous membranous organelles related with vesicular trafficking, secretion and endocytosis in the cytoplasm; well-developed cytoskeleton networks and intercellular junctional complexes were also observed. The specimens on fluorescence immunohistochemistry (IHC) by confocal laser-scanning microscopy (LSM) showed the expression of LC3 and Cx43 associated with autophagic-lysosomal degeneration pathway and signal conduction mediated with gap junctions (GJS) in maintaining tissue homeostasis of the Ob-like cells which grew and degenerated in the 3D scaffold. Results from this in vitro study suggest that Ob-like HMS0014 cells actively regulate turnover of the peri-IP ECM to recapitulate the development and formation of osteoid tissue-engineered material which might contribute to augment osseointegration around the dental implant.

Investigation of biomaterials by human epithelial gingiva cells: an in vitro study

Introduction

In modern medicine and dentistry the use of biomaterials is a fast developing field of increasing interest. Especially in dentistry the interaction between biomaterials like implant materials and the soft tissue in the oral cavity is in the focus of daily research. In this context the high importance of testing materials and their surfaces concerning their biocompatibility towards corresponding cells is very likely. For this purpose this study investigates cells derived from human gingival biopsies on different materials and surfaces.

Methods

Cells in this study were cultivated out of human biopsies by a grow out explant technique and were sub cultivated on titanium, zirconium dioxide and collagen membrane specimens. To characterise the cells on the material surfaces used in this study immunohistochemical and histological staining techniques as well as different methods of microscopy (light microscopy and SEM) were applied.

Results

With the aid of the explant technique and the chosen cell cultivation method it was possible to investigate the human gingiva derived cells on different materials. The data of the present study show that the human gingival cells attach and proliferate on all three tested materials by exhibiting characteristic gingival keratinocyte protein expression even after long periods of culture e.g. up to 70 days.

Conclusions

It could be shown that the three tested materials titanium, zirconium dioxide and collagen membrane (and their special surfaces) are good candidates for the application as materials in the dental gingival environment or, in the case of the collagen membrane as scaffold/cell-carrier for human gingival cells in tissue engineering.

A comparison of biocompatibility and osseointegration of ceramic and titanium implants: an in vivo and in vitro study

This study compared the biocompatibility in vitro and the osseointegration in vivo of zirconium and titanium implants regarding implant surfaces and the bone-implant contacts. The different implant surfaces and the biocompatibility of zirconium versus titanium implants were determined by vitality and cytotoxic tests in vitro. The contact of the osteoblasts to the implant surface was determined by scanning electron microscopy (SEM). The in vivo study for osseointegration was performed in domestic pigs over 4 and 12 weeks. In each animal, 4 zirconium and 4 titanium implants (WhiteSky, BlueSky, Bredent, Germany) were inserted in the os frontale and analysed by histomorphometry. Cytotoxicity and SEM showed good biocompatibility in relation to the investigated implant materials. Histological results showed direct bone-implant contact of the implant surfaces. The zirconium implants showed a slight delay in osseointegration in terms of bone-implant contact as measured by histomorphometry (after 4 weeks, zirconium (59.3 ± 4.6%) versus titanium (64.1 ± 3.9%); after 12 weeks, zirconium (67.1 ± 2.3%) versus titanium (73.6 ± 3.2%). A statistically significant difference between the two groups was not observed. The results indicated similar biocompatibility and osseointegration for zirconium compared to titanium implants.

A preliminary study of the dental implant therapy--initial osteogenesis of human mesenchymal stem (HMS0014) cells on titanium discs with different surface modifications

HMS0014 cells were GBR-engineered to proliferate and differentiate into mature osteoblast(Ob)-like cells, which initiated hard tissue matrix deposition in both monolayer and PuraMatrix 3-D cultures. Subsequently, the osteogenesis initiated with attachment/adhesion of HMS0014 cells on either Titanium (Ti) or Ti alloy discs modified with osteoconductive/ osteoinductive surface textures/substrates (e.g., Disc-AO, Disc-HA, Disc-SPI) was histologically assessed. The results obtained were as follows: 1) The HMS0014 cells actively proliferated and differentiated into mature Obs to initiate mineralisation of the ECM since day 1 in both monolayer and 3-D cultures; mineralization was prominently progressed between day 7 and day 14 of cultures. 2) The SEM of 60-minute(min)s specimens demonstrated a loose distribution of proliferating spherical-to-polygonal (10 to 40 microm in diameter, avg.) cells with a bulging cell body sending out many minute filopodia and some lamellipodia to attach with the substrate in the concavities. 3) In the 180-min specimens, the cultured HMS0014 cells actively proliferated and spread into flat, large polygonal cells with prominent lamellipodia and dendritic filopodia (30 microm x 90 microm to 100 microm x 200 microm, approx.) to employ cell-to-substrate and intercellular attachments. 4) On the other hand, the present immunohistochemistry of the attached HMS0014 cells demonstrated the co-expression of F-actin (actin filaments of the cytoskeleton) and CD51 (aV integrin) in both the 60-min and 180-min specimens. We concluded that the present GBR method enhanced HMS0014 cells to initiate an osteogenesis process with a direct bone-to-substratum contact on Ti discs which were subject to different surface modifications.

Behavior of osteoblastic cells cultured on titanium and structured zirconia surfaces

BACKGROUND

Osseointegration is crucial for the long-term success of dental implants and depends on the tissue reaction at the tissue-implant interface. Mechanical properties and biocompatibility make zirconia a suitable material for dental implants, although surface processings are still problematic. The aim of the present study was to compare osteoblast behavior on structured zirconia and titanium surfaces under standardized conditions.

METHODS

The surface characteristics were determined by scanning electron microscopy (SEM). In primary bovine osteoblasts attachment kinetics, proliferation rate and synthesis of bone-associated proteins were tested on different surfaces.

RESULTS

The results demonstrated that the proliferation rate of cells was significantly higher on zirconia surfaces than on titanium surfaces (p < 0.05; Student's t-test). In contrast, attachment and adhesion strength of the primary cells was significant higher on titanium surfaces (p < 0.05; U test). No significant differences were found in the synthesis of bone-specific proteins. Ultrastructural analysis revealed phenotypic features of osteoblast-like cells on both zirconia and titanium surfaces.

CONCLUSION

The study demonstrates distinct effects of the surface composition on osteoblasts in culture. Zirconia improves cell proliferation significantly during the first days of culture, but it does not improve attachment and adhesion strength. Both materials do not differ with respect to protein synthesis or ultrastructural appearance of osteoblasts. Zirconium oxide may therefore be a suitable material for dental implants.