In vivo monitoring of the bone healing process around different titanium alloy implant surfaces placed into fresh extraction sockets

Improving the osseointegration and soft tissue sealing of zirconia ceramics by the incorporation of akermanite via sol infiltration for dental implants

Zirconia ceramics are promising dental implant materials due to their high-grade biocompatibility, high mechanical strength, and distinctive aesthetic appearance. Nevertheless, zirconia ceramics are bio-inert with a lack of osseointegration and soft tissue sealing, which limits dental implant applications. As such, the fabrication of zirconia ceramics with high mechanical strength, excellent osseointegration and soft tissue sealing performance remains a great challenge in the dental restoration field. In this article, a novel zirconia ceramic with akermanite (AKT) modification by the negative pressure infiltration method is presented. The effects of AKT sol infiltration at different times on the morphology, phase composition, mechanical properties, bioactivity, osseointegration and soft tissue sealing of the modified zirconia ceramics have been systematically investigated. The modified zirconia ceramics feature excellent mechanical properties and significantly improved surface roughness, hydrophilia, and apatite mineralization ability as compared with unmodified zirconia ceramics. Furthermore, cell-culture experiment results indicated that the surface modification of zirconia ceramics could promote adhesion, spreading, migration, proliferation and osteogenic differentiation of mouse bone marrow stromal stem cells (mBMSCs), as well as the early adhesion, spreading, proliferation and fibroblast differentiation of human gingival fibroblasts (HGFs) in vitro. The prepared bioactive zirconia distinctively enhanced the alkaline phosphate (ALP) activity, osteogenesis-related gene expression of mBMSCs and fibroblast-related-gene expression of HGFs. The in vivo evaluation confirmed that 15-TZP ceramics could promote bone-implant osseointegration to the greatest extent as compared with pure zirconia ceramics. To conclude, our research has shown that AKT-modified zirconia ceramics can achieve bone integration and soft tissue sealing, indicating that they have a lot of potential for application as a novel dental implant material in the clinical setting.

The response of soft tissue cells to Ti implants is modulated by blood-implant interactions

Titanium-based dental implants have been highly optimized to enhance osseointegration, but little attention has been given to the soft tissue-implant interface, despite being a major contributor to long term implant stability. This is strongly linked to a lack of model systems that enable the reliable evaluation of soft tissue-implant interactions. Current in vitro platforms to assess these interactions are very simplistic, thus suffering from limited biological relevance and sensitivity to varying implant surface properties. The aim of this study was to investigate how blood-implant interactions affect downstream responses of different soft tissue cells to implants in vitro, thus taking into account not only the early events of blood coagulation upon implantation, but also the multicellular nature of soft tissue. For this, three surfaces (smooth and hydrophobic; rough and hydrophobic; rough and hydrophilic with nanostructures), which reflect a wide range of implant surface properties, were used to study blood-material interactions as well as cell-material interactions in the presence and absence of blood. Rough surfaces stimulated denser fibrin network formation compared to smooth surfaces and hydrophilicity accelerated the rate of blood coagulation compared to hydrophobic surfaces. In the absence of blood, smooth surfaces supported enhanced attachment of human gingival fibroblasts and keratinocytes, but limited changes in gene expression and cytokine production were observed between surfaces. In the presence of blood, rough surfaces supported enhanced fibroblast attachment and stimulated a stronger anti-inflammatory response from macrophage-like cells than smooth surfaces, but only smooth surfaces were capable of supporting long-term keratinocyte attachment and formation of a layer of epithelial cells. These findings indicate that surface properties not only govern blood-implant interactions, but that this can in turn also significantly modulate subsequent soft tissue cell-implant interactions.

Scientometric Analysis of Dental Implant Research over the Past 10 Years and Future Research Trends

BACKGROUND

We conducted a bibliometrics analysis to explore the recent trends in dental implant research which could help researchers have a clear grasp of the relevant research hotspots and prospects. Material and Methods. Altogether, 15,770 articles on dental implants, from January 1, 2010, to October 31, 2019, were selected from the Web of Science Core Collection. We used BICOMB software to extract the high-frequency MeSH terms and construct binary and coword matrices. gCLUTO software was used for biclustering and visual analysis, Ucinet 6 software for social network analysis, SCIMAT software for strategic diagram building, Citespace 5.5 software to form timeline visualization, and VOSviewer software, eventually, for bibliometrics cocitation network.

RESULTS

Altogether, 72 high-frequency keywords were extracted from the selected articles and 4 clusters and 7 subcategories were identified through biclustering analysis in the dental implant research field. The use of the strategic diagram also enabled us to find the research hotspot and development trends.

CONCLUSIONS

The survival rate of dental implants and subsequent restoration have always been the core focus of research. Sinus floor elevation and guided bone regeneration are worthy of constant exploration owing to their reliability. With continuous improvement in technology, immediate loading could become a future research hot spot.

Early cell response of osteogenic cells on differently modified implant surfaces: Sequences of cell proliferation, adherence and differentiation

OBJECTIVES

Osseointegration of dental implants is a crucial prerequisite for long-term survival. Therefore, surface modifications are needed to interact with the extracellular environment and to trigger osteogenic cell responses such as cell proliferation, adherence, and differentiation. The purpose of this study was to investigate different surface modifications in vitro over 2 weeks.

MATERIALS AND METHODS

Commercially available cells from a human osteogenic cell line (HHOB-c) were cultivated on the following surfaces: titanium with smooth surfaces (polished titanium (P), machined titanium (M), polyetheretherketone (Peek)), titanium with rough and hydrophilised surfaces (acid etched titanium (A), sandblasted acid etched titanium (SA and SA2), sandblasted acid etched hydrophilised (SAH), titanium plasma painted titanium (TPS)), titanium with calcium phosphate-containing surfaces (titanium plasma painted calcium phosphate modified titanium (TPS-CaP), sandblasted calcium phosphate modified titanium (S-CaP), sandblasted acid etched calcium phosphate modified titanium (SA-CaP)), and zirconium-oxide (yttrium amplified zirconium (Z), yttrium amplified Ca²⁺ delivering zirconium (Z-Ca)). Tissue culture polystyrene (TCPS) served as a control. Cell count was assessed after 24 h, 48 h, 72 h, 7 d, and 14 d; osteogenic cell adherence and differentiation were analysed by using cellular Quantitative Immuno-Cytochemistry (QIC) assay for alkaline phosphatase (AP), osteocalcin (OC), integrin alpha V (ITGAV), and talin (T).

RESULTS

All tested surfaces showed a positive influence on the differentiation and adherence of osteogenic cells, especially P, M, A, TCPS, and Peek. After 48 h, the surfaces M, SA and SAH had induced a positive influence on adherence, whereas SA2, SA, and SAH triggered proliferation after 14 d.

CONCLUSIONS

Rough and hydrophilised surface modifications, such as SAH, trigger osteogenic cell responses. These in vitro results highlight the potential use of SAH surface modifications of dental implants and indicate further clinical studies are warranted.

Low dose effect of bisphosphonates on hMSCs osteogenic response to titanium surface in vitro

Since the 1980s, titanium (Ti) implants have been routinely used to replace missing teeth. This success is mainly due to the good biocompatibility of Ti and the phenomenon of osseointegration, with very early events at implant placement being important in determining good osseointegration. However, enhancing implant performance with coatings such as hydroxyapatite (HA) and calcium phosphate has proved largely unsuccessful. Human mesenchymal stem cells (hMSCs) are the first osteogenic cells to colonise implant surfaces and offer a target for enhancing osseointegration. We previously reported that small doses of bisphosphonate (BP) may play an integral role in enhancing hMSC proliferation and osteogenic differentiation. The aim of this study is to investigate whether small doses of bisphosphonates enhance proliferation and osteogenic differentiation of hMSCs on Ti surfaces, to enhance bone osseointegration and to accelerate wound healing around the implant surface. Our data suggests that treating cells with small doses of BP (100 nM & 10 nM) induces significant hMSC stimulation of osteogenic markers including calcium, collagen type I and ALP compared to control group on titanium surfaces (P < 0.05). In addition, cell proliferation and migration were significantly enhanced on titanium surfaces (P < 0.05).

COMP-Ang1 prevents periodontitic damages and enhances mandible bone growth in an experimental animal model

COMP-Ang1, a chimera of angiopoietin-1 (Ang1) and a short coiled-coil domain of cartilage oligomeric matrix protein (COMP), is under consideration as a therapeutic agent enhancing tissue regeneration with increased angiogenesis. However, the effect of COMP-Ang1 on periodontitic tissue damages and the related mechanisms are not yet investigated. We initially explored whether a local delivery of COMP-Ang1 protects lipopolysaccharide (LPS)/ligature-induced periodontal destruction in rats. As the results, μCT and histological analyses revealed that COMP-Ang1 inhibits LPS-mediated degradation of periodontium. COMP-Ang1 also suppressed osteoclast number and the expression of osteoclast-specific and inflammation-related molecules in the inflamed region of periodontitis rats. Implanting a COMP-Ang1-impregnated scaffold into critical-sized mandible bone defects enhanced the amount of bone in the defects with increased expression of bone-specific markers. The addition of COMP-Ang1 prevented significantly osteoclast differentiation and activation in LPS-stimulated RAW264.7 macrophages and inhibited the phosphorylation of c-Jun, mitogen-activated protein kinases, and cAMP response element-binding protein in the cells. On contrary, COMP-Ang1 increased the level of phosphatidylinositol 3-kinase (PI3K) in LPS-exposed macrophages and a pharmacological PI3K inhibitor diminished the anti-osteoclastogenic effect of COMP-Ang1. Similarly, COMP-Ang1 blocked the expression of inflammation-related molecules in LPS-stimulated human periodontal ligament fibroblasts (hPLFs). Further, the COMP-Ang1 enhanced differentiation of hPLFs into osteoblasts by stimulating the expression of bone-specific markers, Tie2, and activator protein-1 subfamily. Collectively, our findings may support the therapeutic potentials of COMP-Ang1 in preventing inflammatory periodontal damages and in stimulating new bone growth.

Insulin-like growth factor binding protein-3 affects osteogenic efficacy on dental implants in rat mandible

Insulin like growth factor binding protein-3 (IGFBP-3) in bone cells and its utilization in dental implants have not been well studied. The aim of this study was to determine the osteogenic efficacy of chitosan gold nanoparticles (Ch-GNPs) conjugated with IGFBP-3 coated titanium (Ti) implants. Ch-GNPs were conjugated with IGFBP-3 plasmid DNA through a coacervation process. Conjugation was cast over Ti surfaces, and cells were seeded on coated surfaces. For in vitro analysis the expression of different proteins was analyzed by immunoblotting. For in vivo analysis, Ch-GNP/IGFBP-3 coated implants were installed in rat mandibles. Four weeks post-implantation, mandibles were examined by microcomputed tomography (μCT), immunohistochemistry, hematoxylin & eosin and tartrate resistance acid phosphatase staining. In vitro overexpressed Ch-GNP/IGFBP-3 coated Ti surfaces was associated with activation of extracellular signal related kinase (ERK), inhibition of the stress activated protein c-Jun N-terminal kinase (JNK) and enhanced bone morphogenetic protein (BMP)-2 and 7 compared to control. Further, in vivo, Ch-GNP/IGFBP-3 coated implants were associated with inhibition of implant induced osteoclastogenesis molecules, receptor activator of nuclear factor kappa-B ligand (RANKL) and enhanced expression of osteogenic molecules including BMP2/7 and osteopontin (OPN). The μCT analysis demonstrated that IGFBP-3 increased the volume of newly formed bone surrounding the implants compared to control (n=5; p<0.05). These results support the view that IGFBP-3 overexpression diminishes osteoclastogenesis and enhances osteogenesis of Ti implants, and can serve as a potent molecule for the development of good implantation.

Differences in Healing Patterns of the Bone-Implant Interface between Immediately and Delayed-Placed Titanium Implants in Mouse Maxillae

BACKGROUND

There are no available data on the healing process at the bone-implant interface after immediate implant placement.

PURPOSE

This study aimed to establish an animal experimental model of titanium implants placed in mouse maxillae and compare the healing pattern of the bone-implant interface after immediate implant placement with that after delayed implant placement.

MATERIALS AND METHODS

Maxillary first molars (M1) from 4-week-old mice were extracted and replaced with the implant following drilling (immediate-placement group). In contrast, M1 from 2-week-old mice were extracted, followed by drilling and implantation after 4 weeks (delayed-placement group). The decalcified samples at 0-28 days after implantation were processed by immunohistochemistry, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, and tartrate-resistant acid phosphatase histochemistry. The elements and bone volume of undecalcified samples were quantitatively analyzed by an electron probe microanalyzer.

RESULTS

Osseointegration was completed by 28 days after the procedure in both groups. There were no differences in contact area, bone loss at the cervical area, or rate of calcification at the bone-implant interface between the two groups.

CONCLUSIONS

This study found no significant differences in the chronological healing process at the bone-implant interface between the two groups at the cellular level.

Titanium Surface Roughing Treatments contribute to Higher Interaction with Salivary Proteins MG2 and Lactoferrin

Some surface treatments performed on titanium can alter the composition of salivary pellicle formed on this abiotic surface. Such treatments modify the titanium's surface properties and can promote higher adsorption of proteins, which allow better integration of titanium to the biotic system.

PURPOSE

This study aimed to evaluate the interactions between salivary proteins and titanium disks with different surface treatments.

MATERIALS AND METHODS

Machined titanium disks (n = 48) were divided into four experimental groups (n = 12), according to their surface treatments: surface polishing (SP); acid etching (A); spot-blasting plus acid etching (SB-A); spot-blasting followed by acid etching and nano-functionalization (SB-A-NF). Titanium surfaces were characterized by surface roughness and scanning electron microscopy (SEM). Specimens were incubated with human saliva extracted from submandibular and sublingual glands. Total salivary protein adsorbed to titanium was quantified and samples were submitted to western blotting for mucin glycoprotein 2 (MG2) and lactoferrin identification.

RESULTS

Surface roughness was statistically higher for SB-A and SB-A-NF groups. Scanning electron microscopy images confirmed that titanium surface treatments increased surface roughness with higher number of porous and scratches for SB-A and SB-A-NF groups. Total protein adsorption was significantly higher for SB-A and SB-A-NF groups (p < 0.05), which also presented higher interactions with MG2 and lactoferrin proteins.

CONCLUSION

The roughing of titanium surface by spot-blasting plus acid etching treatments contribute to higher interaction with salivary proteins, such as MG2 and lactoferrin.

CLINICAL SIGNIFICANCE

Titanium surface roughing increases the interactions of the substratum with salivary proteins, which can influence the integration of dental implants and their components to the oral environment. However, those treatments should be used carefully intraorally, avoiding increase biofilm formation.

Interaction of progenitor bone cells with different surface modifications of titanium implant

Changes in the physical and chemical properties of Ti surfaces can be attributed to cell performance, which improves surface biocompatibility. The cell proliferation, mineralization ability, and gene expression of progenitor bone cells (D1 cell) were compared on five different Ti surfaces, namely, mechanical grinding (M), electrochemical modification through potentiostatic anodization (ECH), sandblasting and acid etching (SLA), sandblasting, hydrogen peroxide treatment, and heating (SAOH), and sandblasting, alkali heating, and etching (SMART). SAOH treatment produced the most hydrophilic surface, whereas SLA produced the most hydrophobic surface. Cell activity indicated that SLA and SMART produced significantly rougher surfaces and promoted D1 cell attachment within 1 day of culturing, whereas SAOH treatment produced moderate roughness (Ra=1.26μm) and accelerated the D1 cell proliferation up to 7 days after culturing. The ECH surface significantly promoted alkaline phosphatase (ALP) expression and osteocalcin (OCN) secretion in the D1 cells compared with the other surface groups. The ECH and SMART-treated Ti surfaces resulted in maximum ALP and OCN expressions during the D1 cell culture. SLA, SAOH, and SMART substrate surfaces were rougher and exhibited better cell metabolic responses during the early stage of cell attachment, proliferation, and morphologic expressions within 1 day of D1 cell culture. The D1 cells cultured on the ECH and SMART substrates exhibited higher differentiation, and higher ALP and OCN expressions after 10 days of culture. Thus, the ECH and SMART treatments promote better ability of cell mineralization in vitro, which demonstrate their great potential for clinical use.

The effects of different wavelength UV photofunctionalization on micro-arc oxidized titanium

Many challenges exist in improving early osseointegration, one of the most critical factors in the long-term clinical success of dental implants. Recently, ultraviolet (UV) light-mediated photofunctionalization of titanium as a new potential surface treatment has aroused great interest. This study examines the bioactivity of titanium surfaces treated with UV light of different wavelengths and the underlying associated mechanism. Micro-arc oxidation (MAO) titanium samples were pretreated with UVA light (peak wavelength of 360 nm) or UVC light (peak wavelength of 250 nm) for up to 24 h. UVC treatment promoted the attachment, spread, proliferation and differentiation of MG-63 osteoblast-like cells on the titanium surface, as well as the capacity for apatite formation in simulated body fluid (SBF). These biological influences were not observed after UVA treatment, apart from a weaker effect on apatite formation. The enhanced bioactivity was substantially correlated with the amount of Ti-OH groups, which play an important role in improving the hydrophilicity, along with the removal of hydrocarbons on the titanium surface. Our results showed that both UVA and UVC irradiation altered the chemical properties of the titanium surface without sacrificing its excellent physical characteristics, suggesting that this technology has extensive potential applications and merits further investigation.