The effect of hydrofluoric acid treatment on titanium implant osseointegration in ovariectomized rats

Application of advanced surface modification techniques in titanium-based implants: latest strategies for enhanced antibacterial properties and osseointegration

Titanium-based implants, renowned for their excellent mechanical properties, corrosion resistance, and biocompatibility, have found widespread application as premier implant materials in the medical field. However, as bioinert materials, they often face challenges such as implant failure caused by bacterial infections and inadequate osseointegration post-implantation. Thus, to address these issues, researchers have developed various surface modification techniques to enhance the surface properties and bioactivity of titanium-based implants. This review aims to outline several key surface modification methods for titanium-based implants, including acid etching, sol-gel method, chemical vapor deposition, electrochemical techniques, layer-by-layer self-assembly, and chemical grafting. It briefly summarizes the advantages, limitations, and potential applications of these technologies, presenting readers with a comprehensive perspective on the latest advances and trends in the surface modification of titanium-based implants.

Unexpected early loosening of rectangular straight femoral Zweymüller stems with an alumina-reduced surface after total hip arthroplasty-a prospective, double-blind, randomized controlled trial

BACKGROUND

Alumina particles from the grit blasting of Ti-alloy stems are suspected to contribute to aseptic loosening. An alumina-reduced stem surface was hypothesized to improve osseointegration and show comparable short-term outcomes to those of a standard stem.

METHODS

In this prospective, double-blind, randomized trial, 26 standard (STD) and 27 experimental new technology (NT) stems were implanted. The latter were additionally treated by acid etching and ice blasting to remove alumina particles from the grit-blasting process. Follow-up occurred at 12 and 24 months. Bone mineral density (BMD) around the stem was measured by a dual-energy x-ray absorptiometry device (DEXA). Radiographs were reviewed for alterations. Clinical scoring comprised the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Harris Hip Score (HHS). Survival rates were calculated up to 50 months.

RESULTS

Lower mean BMD and more severe cortical hypertrophies were found in the NT group. At 12 months, radiolucent lines were observed mostly in the metaphyseal zone for both groups, with a progression tendency in the NT group at 24 months. At 12 months, pain scores and the WOMAC total and physical activity scores were significantly lower in the NT group, without any differences thereafter. The number of NT stem revisions amounted to 6 (24%) and 11 (41%) at 24 and 50 months, respectively.

CONCLUSION

In the NT group, unexpected catastrophic failure rates of 41% caused by early aseptic loosening were noted within 50 months. Compared with the STD stems, NT stems lead to poor clinical and radiographic results.

LEVEL OF EVIDENCE

II.

TRIAL REGISTRATION

NCT05053048.

Effect of Er:YAG Pulsed Laser-Deposited Hydroxyapatite Film on Titanium Implants on M2 Macrophage Polarization In Vitro and Osteogenesis In Vivo

In a previous study, we successfully coated hydroxyapatite (HAp) onto titanium (Ti) plates using the erbium-doped yttrium aluminum garnet pulsed-laser deposition (Er:YAG-PLD) method. In this study, we performed further experiments to validate the in vitro osteogenic properties, macrophage polarization, and in vivo osseointegration activity of HAp-coated Ti (HAp-Ti) plates and screws. Briefly, we coated a HAp film onto the surfaces of Ti plates and screws via Er:YAG-PLD. The surface morphological, elemental, and crystallographic analyses confirmed the successful surface coating. The macrophage polarization and osteogenic induction were evaluated in macrophages and rat bone marrow mesenchymal stem cells, and the in vivo osteogenic properties were studied. The results showed that needle-shaped nano-HAp promoted the early expression of osteogenic and immunogenic genes in the macrophages and induced excellent M2 polarization properties. The calcium deposition and osteocalcin production were significantly higher in the HAp-Ti than in the uncoated Ti. The implantation into rat femurs revealed that the HAp-coated materials had superior osteoinductive and osseointegration activities compared with the Ti, as assessed by microcomputed tomography and histology. Thus, HAp film on sandblasted Ti plates and screws via Er:YAG-PLD enhances hard-tissue differentiation, macrophage polarization, and new bone formation in tissues surrounding implants both in vitro and in vivo.

Biomimetic Hydroxyapatite Composite Coatings with a Variable Morphology Mediated by Silk Fibroin and Its Derived Peptides Enhance the Bioactivity on Titanium

Various modifications performed on titanium alloy surfaces are shown to improve osteointegration and promote the long-term success of implants. In this work, a bioactive nanostructured hydroxyapatite (HA) composite coating with a variable morphology mediated by silk fibroin (SF) and its derived peptides (Cs) was prepared. Numerous experimental techniques were used to characterize the constructed coatings in terms of morphology, roughness, hydrophilicity, protein adsorption, in vitro biomineralization, and adhesion strength. The mixed protein layer with different contents of SF and Cs exhibited different secondary structures at different temperatures, effectively mediating the electrodeposited HA layer with different characteristics and finally forming proteins/HA composite coatings with versatile morphologies. The addition of Cs significantly improved the hydrophilicity and protein adsorption capacity of the composite coatings, while the electrodeposition of the HA layer effectively enhanced the adhesion between the composite coatings and Ti surface. In the in vitro mineralization experiments, all the composite coatings exhibited excellent apatite formation ability. Moreover, the composite coatings showed excellent cell growth and proliferation activity. Osteogenic induction experiments revealed that the coating could significantly increase the expression of specific osteogenic markers, including ALP, Col-I, Runx-2, and OCN. Overall, the proposed modification of the Ti implant surface by protein/HA coatings had good potential for clinical applications in enhancing bone induction and osteogenic activity of implants.

Influence of Magnesium Content on the Physico-Chemical Properties of Hydroxyapatite Electrochemically Deposited on a Nanostructured Titanium Surface

The aim of this research was to obtain hydroxyapatite (HAp)-based coatings doped with different concentrations of Mg on a Ti nanostructured surface through electrochemical techniques and to evaluate the influence of Mg content on the properties of HAp. The undoped and doped HAp-based coatings were electrochemically deposited in galvanostatic pulsed mode on titania nanotubes with a diameter of ~72 nm, being designed to enhance the adhesion of the HAp coatings to the Ti substrate. The obtained materials were investigated by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-Ray Diffraction (XRD), and Fourier-Transform Infra-Red spectroscopy (FTIR). The adhesion of the coatings to the substrate was also evaluated with the help of the “tape-test” and the micro-scratch test. The morphology (SEM) of all the coatings is made of very thin and narrow ribbon-like crystals, with some alterations with respect to the Mg amount in the coatings. Thus, a concentration of 1 mM of Mg in the electrolyte leads to wider and thicker ribbon-like crystals, while a concentration of 1.5 mM in the electrolyte generated a morphology that resembles the undoped HAp. Both phase composition (XRD) and chemical bonds (FTIR) analysis proved the formation of HAp in all coatings. Moreover, according to XRD, all coatings have a strong orientation toward the (002) plane. Irrespective of the Mg content, all coatings registered an average roughness between approx. 500 and 600 nm, while the coating thickness increased after addition of Mg, from a value of 9.6 μm, for the undoped HAp, to 11.3 μm and ~13.7 μm for H/Mg1 and H/Mg2, respectively. In terms of adhesion, it was shown that the coatings a H/Mg2 had a poorer adhesion when compared to H/Mg1 and the undoped HAp (H), which registered similar adhesion, indicating that a concentration of 1.5 mM of Mg in the electrolyte reduces the adhesion of the Hap-based coatings to the nanostructured surface. The obtained results indicated that Mg concentrations up to 1 mM in the electrolyte can enhance the properties of HAp-based coatings electrochemically deposited on a nanostructured surface, while even a slightly higher concentration of 1.5 mM can negatively impact the characteristics of HAp coatings.

Osseointegration Effect of Micro-Nano Implants Loaded With Kaempferol in Osteoporotic Rats

Objective: To investigate the effect of osseointegration of kaempferol loaded on the surface of micro-nanomorphic implants in ovariectomized rats.

Methods: Titanium flakes were polished to obtain the PT group, anodized and acid-etched to obtain the NT and WNT groups, loaded with kaempferol to obtain the KNT and KWNT groups, and spin-coated on chitosan-gelatin composite film to obtain the KNT-CG and KWNT-CG groups. In vitro experiments were performed to observe the physicochemical properties of the titanium tablets in each group through scanning electron microscopy and contact angle experiments. The cytotoxicity and drug release pattern were observed using CCK-8 and drug release assays. An osteoporosis rat model was established. Pure titanium implants were divided into PT, NT, WNT, KNT-CG, and KWNT-CG groups after the same treatment and used in the in vivo experiments and then implanted in the femur of mice in each group. After 4 weeks, all samples were collected for toluidine blue staining, micro-computed tomography scanning, and bone morphometry analysis to evaluate their osteogenic properties.

Results: According to scanning electron microscopy, the surface of the titanium flakes had a micro-nano morphology in the WNT group and the KNT and KWNT groups were functionally loaded with kaempferol. In CCK-8 and drug release experiments, the loaded kaempferol and gelatin composite membranes showed no significant toxic effects on cells. The drug release time in the KNT-CG and KWNT-CG groups was significantly longer than that in the KNT and KWNT groups, with the release time in the KWNT-CG group reaching 15 days. In vivo experiments micro-computed tomography and bone morphometry analysis showed that the osteoporosis model had been successfully constructed. The bone volume fraction around the implant increased. Toluidine blue staining showed new bone formation and a significantly increased number of bone trabeculae.

Conclusion: Kaempferol micro-nanocomposite coating improved the osseointegration ability of implants in osteoporotic rats.

Effect of micro/nanoscaled Ti phosphate/Ti oxide hybrid coating on the osseointegration of Ti implants

OBJECTIVES

This study was performed to fabricate a bionic coating with titanium (Ti) phosphate to promote the osseointegration of Ti substrate implants.

METHODS

Phosphorylated micro/nanocoating was prepared on the surface of pure titanium (i.e., TiP-Ti) by hydrothermal process under special pressure, and the untreated smooth pure titanium (cp-Ti) was selected as the control. To evaluate the characteristics of the coating surface, scanning electron microscopy, X-ray diffraction, atomic force microscopy, and contact-angle measurement were performed. In addition, the effects of TiP-Ti on the proliferation, adhesion, and differentiation of rat bone marrow mesenchymal stem cells (BMSCs) were investigated by using in vitro cytology. Finally, TiP-Ti implants were implanted into the rat tibia, and the effect of TiP-Ti on the osseointegration in the host was evaluated after 12 weeks.

RESULTS

The TiP-Ti surface presented a bionic structure with coexisting nanoscale 3D spatial structure and microscale pores. In vitro experiments showed that the BMSCs had enhanced adhesion, proliferation, and osteogenic differentiation on the TiP-Ti surface. Furthermore, in vivo, TiP-Ti showed considerably stronger osseointegration compared with pure titanium, and the ultimate shear strength and maximum pushing force were significantly improved.

CONCLUSIONS

A bionic structure with TiP-Ti micro/nanoscale coating was successfully fabricated, indicating a promising method for modifying the surface of implants.

Boron-incorporated micro/nano-topographical calcium silicate coating dictates osteo/angio-genesis and inflammatory response toward enhanced osseointegration

Orthopedic implant coatings with optimal surface features to achieve favorable osteo/angio-genesis and inflammatory response would be of great importance. However, to date, few coatings are capable of fully satisfying these requirements. In this work, to take advantage of the structural complexity of micro/nano-topography and benefits of biological trace elements, two types of boron-containing nanostructures (nanoflakes and nanolamellars) were introduced onto plasma-sprayed calcium silicate (F-BCS and L-BCS) coatings via hydrothermal treatment. The C-CS coating using deionized water as hydrothermal medium served as control. Boron-incorporated CS coating stimulated osteoblastic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs). Specifically, the combination of β1 integrin-vinculin-mediated cell spreading and activation of bone morphogenetic protein signaling pathway acted synergistically to cause significant upregulation of runt-related transcription factor 2 (RUNX2) protein and Runx2 gene expression in BMSCs on the F-BCS coating surface, which induced the transcription of downstream osteogenic differentiation marker genes. F-BCS coating allowed specific boron ion release, which favored angiogenesis as evidenced by the enhanced migration and tube formation of human umbilical vein endothelial cells in the coating extract. Boron-incorporated coatings significantly suppressed the expression of toll-like receptor adaptor genes in RAW264.7 macrophages and subsequently the degradation of nuclear factor-κB inhibitor α, accompanied by the inactivation of the downstream pro-inflammatory genes. In vivo experiments confirmed that F-BCS-coated Ti implant possessed enhanced osseointegration compared with L-BCS- and C-CS-coated implants. These data highlighted the synergistic effect of specific nanotopography and boron release from orthopedic implant coating on improvement of osseointegration.

The Calcium Phosphate Modified Titanium Implant Combined With Platelet-Rich Plasma Treatment Promotes Implant Stabilization in an Osteoporotic Model

ABSTRACT

Osteoporosis as a kind of systemic bone metabolic disease has become one of the most prevalent diseases among the middle- and old-age, characterized with low bone mass and disruptive osseous microenvironment. The poor bone condition both in quantity and quality makes it daunting for osteoporotic patients who are submitted to dental implantation, joint replacement therapy, or orthopedic surgery. Since calcium phosphate (CaP) and platelet-rich plasma (PRP) treatment, all have improving the effect on bone regeneration. Inspired by this fact, the authors introduced a kind of novel implant with CaP modified surface by HPT (hydrothermal & pressure) treatment in this study. After producing, the authors tested its physicochemical properties through scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscope (XPS) and contact-angle measurement. Then the authors desired to investigate the effect of this CaP-modified implant on bone regeneration and stabilization maintenance combined with PRP treatment by establishing an osteoporotic rat model. After 3 months of surgery, the authors collected all the specimens and evaluated new bone formation by micro-computed tomography (micro-CT) analysis, biomechanical test, and histologic assessment. All the results in vivo experiment showed the CaP modified implant combined with PRP treatment could improve the osteoinductive effect under osteoporotic condition, leading to better maintenance for stabilization between bone and implant interface, which might be rendered as a promising clinical method for osteoporotic patients when they receive orthopedic surgeries.

Osseointegration of a novel dental implant in canine

This study aimed to compare and verify the osseointegration performance of a novel implant (NI) in vivo, which could provide a useful scientific basis for the further development of NIs. Thirty-two NIs treated with hydrofluoric acid and anodization and sixteen control implants (CIs) were placed in the mandibles of 8 beagles. Micro-CT showed that the trabecular number (Tb.N) significantly increased and trabecular separation (Tb.Sp) significantly decreased in the NIs at 2 weeks. Significant differences were found in the trabecular thickness, Tb.N, Tb.Sp, bone surface/bone volume ratio, and bone volume/total volume ratio between the two groups from the 2nd–4th weeks. However, there were no significant differences between the two groups in the bone volume density at 2, 4, 8, or 12 weeks or bone-implant contact at 2 or 4 weeks, but the BIC in the CIs was higher than that in the NIs at the 8th and 12th weeks. Meanwhile, the histological staining showed a similar osseointegration process between the two groups over time. Overall, the NIs could be used as new potential implants after further improvement.

Biomineralization inspired engineering of nanobiomaterials promoting bone repair

A biomineralization processes is disclosed for engineering nanomaterials that support bone repair. The material was fabricated through a hot press process using electrospun poly(lactic acid) (PLA) matrix covered with hybrid composites of carbon nanotubes/graphene nanoribbons (GNR) and nanohydroxyapatite (nHA). Various scaffolds were devised [nHA/PLA, PLA/GNR, and PLA/nHA/GNR (1 and 3%)] and their structure and morphology characterized through Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), and Atomic force microscope (AFM). Moreover, thorough biocompatibility and toxicity studies were performed. Here, in vivo studies on toxicity and cytotoxicity were conducted in aqueous dispersions of the biomaterials at concentrations of 30, 60, and 120 μg/mL using the Allium cepa test. Further toxicity studies were performed through hemolysis toxicity tests and genotoxicity tests evaluating the damage index and damage frequencies of DNAs through comet assays with samples of the animals' peripheral blood, marrow, and liver. Additionally, the regenerative activity of the scaffolds was analyzed by measuring the cortical tibiae of rats oophorectomized implanted with the biomaterials. Biochemical analyzes [glutamic pyruvic transaminase (GPT), glutamic oxaloacetic transaminase (GOT), urea, calcium, phosphorus, and alkaline phosphatase (ALP)] were also performed on blood samples. The results suggested a toxicity and cytotoxicity level for the GNR biomaterials at a concentration of 60 and 120 μg/mL, but non-toxicity and cytotoxicity for the 30 μg/mL concentration. The scaffolds obtained at a concentration of 0.3 mg/cm² were not toxic in the hemolysis test and demonstrated no cytotoxicity, genotoxicity, and mutagenicity in the blood, marrow, and liver analyzes of the animals, corroborating data from the biochemical markers of GPT, GOT, and urea. Tissue regeneration was performed in all groups and was more pronounced in the group containing the combination of nHA/GNR (3%), which is consistent with the data obtained for the calcium, serum phosphorus, and ALP concentrations. Consequently, the study indicates that the engineered nanobiomaterial is a promising candidate for bone tissue repair and regenerative applications. STATEMENT OF SIGNIFICANCE: The scientific contribution of this study is the engineering of a synthetic hybrid biomaterial, in nanoscale by a pressing and heating process. A biodegradable polymeric matrix was covered on both sides with a carbonated hybrid bioceramic/graphene nanoribbons (GNR), which has hydrophilic characteristics, with chemical elements stoichiometrically similar to bone mineral composition. The nanomaterial displayed promising bone regeneration ability, which is the first example to be used in an osteoporotic animal model. Moreover, detailed biocompatibility and toxicity studies were performed on the nanomaterials and their compositions, which is of great interest for the scientific community.

Genipin and insulin combined treatment improves implant osseointegration in type 2 diabetic rats

BACKGROUND

Type 2 diabetes mellitus (T2DM) has a harmful effect on the stability and osseointegration of dental implants. T2DM induces mitochondrial damage by inhibiting AMPK signaling, resulting in oxidative stress and poor osteogenesis in the peri-implant bone area. Genipin is a major component of gardenia fruits with strong antioxidant, anti-inflammation, and antidiabetic actions, and it also can activate mitochondrial quality control via the AMPK pathway. The purpose of this study was to investigate the effects of genipin and insulin treatment on implant osseointegration in T2DM rats and explore the underlying mechanisms.

METHODS

Streptozotocin-induced diabetic rats received implant surgery in their femurs and were then assigned to five groups that were subjected to different treatments for three months: control group, T2DM group, insulin-treated T2DM group (10 IU/kg), genipin-treated T2DM group (50 mg/kg), and the genipin and insulin combination-treated T2DM group. Then, we regularly assessed the weight and glucose levels of the animals. Rats were euthanized at 3 months after the implantation procedure, and the femora were harvested for microscopic computerized tomography analysis, biomechanical tests, and different histomorphometric assessment.

RESULTS

The results indicated that the highest blood glucose and oxidative stress levels were measured for the T2DM group, resulting in the poorest osseointegration. The combination-treated T2DM group mitigated hyperglycemia and normalized, reactivated AMPK signaling, and alleviated oxidative stress as well as reversed the negative effect of osseointegration. There were beneficial changes observed in the T2DM-genipin and T2DM-insulin groups, but these were less in comparison to the combination treatment group.

CONCLUSION

Our study suggests that treatment with genipin in combination with insulin could be an effective method for promoting implant osseointegration in T2DM rats, which may be related to AMPK signaling.

The morphological effect of nanostructured hydroxyapatite coatings on the osteoinduction and osteogenic capacity of porous titanium

Weak osteogenic activity affects the long-term fixation and lifespan of titanium (Ti) implants. Surface modification along with a built-in porous structure is a highly considerable approach to improve the osteoinduction and osseointegration capacity of Ti. Herein, the osteoinduction and osteogenic activities of electrochemically deposited (ED) nanoplate-like, nanorod-like and nanoneedle-like hydroxyapatite (HA) coatings (named EDHA-P, EDHA-R, and EDHA-N, respectively) were evaluated in vitro and in vivo by comparison with those of acid/alkali (AA) treatment. The results revealed that the apatite forming ability of all nanostructured EDHA coatings was excellent, and only 12 h of soaking in SBF was needed to induce a complete layer of apatite. More serum proteins adsorbed on EDHA-P than others. In cellular experiments, different from those on EDHA-R and EDHA-N, the cells on EDHA-P presented a polygonal shape with lamellipodia extension, and thus exhibited a relatively larger spreading area. Furthermore, EDHA-P was more favorable for the enhancement of the proliferation and ALP activity of BMSCs, and the up-regulation of OPN gene expression. Based on the good biological performance in vitro, EDHA-P was selected to further evaluate its osteoinduction and osteogenic activities in vivo by comparison with AA treatment. Interestingly, a greater ability of ectopic osteoinduction was observed in the EDHA-P group compared to that in the AA group. At the osseous site, EDHA-P promoted more bone on/ingrowth, and had a higher area percentage of newly formed bone in the bone-implant interface and inner pores of the implants than in the AA group. Thus, a nanoplate-like HA coating has good potential in improving the osteoinductivity and osteogenic activity of porous Ti implants in clinical applications.

Effects of novel non-thermal atmospheric plasma treatment of titanium on physical and biological improvements and in vivo osseointegration in rats

Titanium (Ti) has achieved extensive applications due to its excellent biocompatibility and mechanical properties. Plasma can enhance surface hydrophilia of Ti with decreased carbon contamination. The traditional conditions using a single gas plasma was for longer treatment time and more prone to being contaminated. We designed and developed novel and universal apparatus and methods with a special clamping device of non-thermal atmospheric plasma (NTAP) treatment using mixed gas for Ti surface activation. We systematically and quantitatively investigated the effective effects of NTAP-Ti. The surface water contact angle decreased by 100%, the carbon content decreased by 80% and oxygen content increased by 50% in the novel NTAP-Ti surfaces. NTAP treatment accelerated the attachment, spread, proliferation, osteogenic differentiation and mineralization of MC3T3-E1 mouse preosteoblasts in vitro. The percentage of bone-to-implant contact increased by 25–40%, and the osteoclasts and bone resorption were suppressed by 50% in NTAP-Ti in vivo. In conclusion, NTAP-Ti substantially enhanced the physical and biological effects and integration with bone. The novel and universal apparatus and methods with a special clamping device using gas mixtures are promising for implant activation by swiftly and effectively changing the Ti surface to a hydrophilic one to enhance dental and orthopedic applications.

Optimized Nanointerface Engineering of Micro/Nanostructured Titanium Implants to Enhance Cell-Nanotopography Interactions and Osseointegration

The success of orthopedic implants requires rapid and complete osseointegration which relies on an implant surface with optimal features. To enhance cellular function in response to the implant surface, micro- and nanoscale topography have been suggested as essential. The aim of this study was to identify an optimized Ti nanostructure and to introduce it onto a titanium plasma-sprayed titanium implant (denoted NTPS-Ti) to confer enhanced immunomodulatory properties for optimal osseointegration. To this end, three types of titania nanostructures, namely, nanowires, nanonests, and nanoflakes, were achieved on hydrothermally prepared Ti substrates. The nanowire surface modulated protein conformation and directed integrin binding and specificity in such a way as to augment the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) and induce a desirable osteoimmune response of RAW264.7 macrophages. In a coculture system, BMSCs on the optimized micro/nanosurface exerted enhanced effects on nonactivated or lipopolysaccharide-stimulated macrophages, causing them to adopt a less inflammatory macrophage profile. The enhanced immunomodulatory properties of BMSCs grown on NTPS-Ti depended on a ROCK-medicated cyclooxygenase-2 (COX2) pathway to increase prostaglandin E2 (PGE2) production, as evidenced by decreased production of PGE2 and concurrent inhibition of immunomodulatory properties after treatment with ROCK or COX2 inhibitors. In vivo evaluation showed that the NTPS-Ti implant resulted in enhanced osseointegration compared with the TPS-Ti and Ti implants. The results obtained in our study may provide a prospective approach for enhancing osseointegration and supporting the application of micro/nanostructured Ti implants.

Effect of van der Waals interactions on the adhesion strength at the interface of the hydroxyapatite–titanium biocomposite: a first-principles study

Hydroxyapatite (HAP) is frequently used as biocompatible coating on Ti-based implants. In this context, the HAP-Ti adhesion is of crucial importance. Here, we report ab initio calculations to investigate the influence of Si incorporation into the amorphous calcium-phosphate (a-HAP) structure on the interfacial bonding mechanism between the a-HAP coating and an amorphous titanium dioxide (a-TiO₂) substrate, contrasting two different density functionals: PBE-GGA, and DFT-D3, which are capable of describing the influence of the van der Waals (vdW) interactions. In particular, we discuss the effect of dispersion on the work of adhesion (W_ad), equilibrium geometries, and charge density difference (CDD). We find that replacement of P by Si in a-HAP (a-Si-HAP) with the creation of OH vacancies as charge compensation results in a significant increase in the bond strength between the coating and substrate in the case of using the PBE-GGA functional. However, including the vdW interactions shows that these forces considerably contribute to the W_ad. We show that the difference (W_ad − W_ad(vdW)) is on average more than 1.1 J m⁻² and 0.5 J m⁻² for a-HAP/a-TiO₂ and a-Si-HAP/a-TiO₂, respectively. These results reveal that including vdW interactions is essential for accurately describing the chemical bonding at the a-HAP/a-TiO₂ interface.

Dispersion interactions play a significant role in altering the bonding strength of the hydroxyapatite coating to the substrate, and such interactions is critical in molecular simulations.

PTPN2 improves implant osseointegration in T2DM via inducing the dephosphorylation of ERK

Type 2 diabetes mellitus (T2DM) is considered to compromise implant osseointegration. Protein tyrosine phosphatase non-receptor type 2 (PTPN2) regulates glucose metabolism, systemic inflammation, and bone regeneration. This study aimed to investigate the role of PTPN2 in implant osseointegration in T2DM and explore the potential mechanisms. Streptozotocin-induced diabetic rats received implant surgery, with or without local overexpression of PTPN2 for three months, and implant osseointegration was examined by histological evaluation, micro-CT analysis, pull-out test, and scanning electron microscope. Rat bone marrow stem cells (RBMSCs) were isolated and exposed to high glucose, and osteogenic differentiation was evaluated by alizarin red staining, ALP assay, and Western blot analysis. Overexpression of PTPN2 could improve impaired implant osseointegration in T2DM rats and promote osteogenic differentiation of RBMSCs in high glucose. In addition, p-ERK level in RBMSCs was increased in high glucose and decreased after PTPN2 overexpression. These results suggest that PTPN2 promotes implant osseointegration in T2DM rats and enhances osteogenesis of RBMSCs in high glucose medium via inducing the dephosphorylation of ERK. PTPN2 may be a novel target for the therapy of impaired implant osseointegration in T2DM patients.

Impact statement

Using both in vivo and in vitro approaches, we made important findings that PTPN2 promoted implant osseointegration in T2DM rats and enhanced osteogenesis of RBMSCs in high glucose medium. The positive effects of PTPN2 on osteogenesis are related to the dephosphorylation of ERK and the inhibition of MAPK/ERK pathway. PTPN2 may be a novel target for the therapy of impaired implant osseointegration in T2DM patients.

Exploring the mechanism behind improved osteointegration of phosphorylated titanium implants with hierarchically structured topography

Titanium (Ti) and its alloys have been frequently used in dental and orthopedic implants, but the undesired oxide layer easily formed on the surface tends to be the cause of implant failure for Ti-based implants. To address this problem, we herein prepared a phosphorylated Ti coating (TiP-Ti) with a micro/nano hierarchically structured topography on commercially pure Ti implants by a hydrothermal method to improve its osteointegration capacity. The surface morphology, chemical composition, and biological activity were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), contact-angle measurement, and protein adsorption assay. Osteointegration of TiP-Ti implants in rat tibia was investigated by biomechanical testing, micro-CT and histological analyses. We further explored the proposed mechanism which improves osteointegration of TiP-Ti implants by proliferation, adhesion, and differentiation assays of rat bone marrow mesenchymal stem cells (BMSCs). Our results demonstrated that the improved osteointegration mainly benefited from the better spread and adhesion of BMSCs on the micro/nano hierarchically structured TiP-Ti surfaces compared to hydroxyapatite coated Ti (HA-Ti), the positive control, and untreated Ti (untreated-Ti), the negative control. In conclusion, TiP-Ti surface is a promising candidate implant surface design to accelerate the osteointegration of Ti-based implants in biomedical applications.

Effects of capsaicin-induced sensory denervation on early implant osseointegration in adult rats

The presence of nerve endings around implants is well-known, but the interaction between the peripheral nervous system and the osseointegration of implants has not been thoroughly elucidated to date. The purpose of this study was to test the effects of selective sensory denervation on early implant osseointegration. Forty male Sprague-Dawley rats were divided randomly into two groups, group A and group B, and they were treated with capsaicin and normal saline, respectively. One week later, titanium implants were placed in the bilateral femurs of the rats. Three and six weeks after implantation, histological examination, microcomputed tomography and biomechanical testing were performed to observe the effect of sensory denervation on implant osseointegration. At three weeks and six weeks, bone area, trabecular bone volume/total bone volume and bone density were significantly lower in group A than in group B. Similarly, the bone-implant contact rate, trabecular number and trabecular thickness were clearly lower in group A than in group B at three weeks. However, the trabecular separation spacing in group A was greater than that in group B at both time points. Biomechanical testing revealed that the implant-bone binding ability of group A was significantly lower than that in group B. The research demonstrated that sensory innervation played an important role in the formation of osseointegration. Selective-sensory denervation could reduce osseointegration and lower the binding force of the bone and the implant.

Promoting Osseointegration of Ti Implants through Micro/Nanoscaled Hierarchical Ti Phosphate/Ti Oxide Hybrid Coating

In this study, micro/nanoscaled hierarchical hybrid coatings containing titanium (Ti) phosphate and Ti oxide have been fabricated with the aim of promoting osseointegration of Ti-based implants. Three representative surface coatings, namely, micro/nanograss Ti (P-G-Ti), micro/nanoclump Ti, (P-C-Ti), and micro/nanorod Ti (P-R-Ti), have been produced. In-depth investigations into the coating surface morphology, topography, chemical composition, and the surface/cell interaction have been carried out using scanning electron microscopy, transmission electron microscope, X-ray photoelectron spectroscopy, X-ray diffraction, contact-angle measurement, and protein adsorption assay. In addition, in vitro performance of the coating (cell proliferation, adhesion, and differentiation) has been evaluated using rat bone marrow stromal cells (BMSCs), and in vivo assessments have been carried out based on a rat tibia implantation model. All the hybrid coating modified implants demonstrated enhanced protein adsorption and BMSC viability, adhesion and differentiation, with P-G-Ti showing the best bioactivity among all samples. Subsequent i n vivo osseointegration tests confirmed that P-G-Ti has induced a much stronger interfacial bonding with the host tissue, indicated by the 2-fold increase in the ultimate shear strength and over 6-fold increase in the maximum push-out force compared to unmodified Ti implants. The state-of-the-art coating technology proposed for Ti-based implants in this study holds great potential in advancing medical devices for next-generation healthcare technology.

Electrically bioactive coating on Ti with bi-layered SnO2–TiO2 hetero-structure for improving osteointegration

SnO₂–TiO₂ surface with the bi-layered structure on Ti provides internal electric stimulation to promote osteointegration of implant.

A comparison of micro-CT and histomorphometry for evaluation of osseointegration of PEO-coated titanium implants in a rat model

The aim of the present study was to determine the correlation between bone volume density (BV/TV) around a titanium implant determined by micro-computed tomography (micro-CT) and bone area density (BA/TA) measurements obtained using histomorphometry. An intramedullary rat femur implant model was evaluated to compare raw titanium implants with plasma electrolytic oxidation (PEO)-coated titanium implants. Titanium and PEO-treated titanium pins were inserted into rat femurs under general anesthesia. The animals were sacrificed and femurs harvested at 0, 2, 4 and 6 weeks, and subsequently, histomorphometry and micro-CT were performed. BV/TV and BA/TA values were strongly and positively correlated at all time points and locations (with all correlation coefficients being >0.8 and with P < 0.001). BV/TV and BA/TA were significantly higher proximal to the growth plate than distal to the growth plate, with estimated differences of 14.10% (P < 0.001) and 11.95% (P < 0.001), respectively. BV/TV and BA/TA were significantly higher on the PEO-coated surface than on the raw titanium surface, with estimated differences of 3.20% (P = 0.044) and 4.10% (P = 0.018), respectively. Therefore, quantitative micro-CT analysis of BV/TV is correlated with BA/TA determined by histomorphometry when artifacts around titanium implants are minimized by a region of interest modification.

Effects of different hierarchical hybrid micro/nanostructure surfaces on implant osseointegration

BACKGROUND

Hierarchical hybrid micro/nanostructure implant surfaces are considered to better mimic the hierarchical structure of bone and the nanostructures substantively influence osseointegration through managing cell behaviors.

PURPOSE

To enhance implant osseointegration for further clinical application, we evaluated the material properties and osseointegration effects of hierarchical surfaces with different nano-morphologies, using a rat model.

MATERIALS AND METHODS

Two representative surface fabrication methods, hydrofluoric (HF) acid etching combined with anodization (HF + AN) or magnetron sputtering (HF + MS), were selected. Sample material properties were evaluated by scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray photoemission spectroscopy, and epoxy resin docking tensile test. Implants with different surfaces were inserted into the distal femurs of rats. After 12 weeks, osseointegration was examined by microcomputed tomography (micro-CT), histological, and biomechanical tests.

RESULTS

Tensile testing demonstrated high bonding strength at coating/implant in the HF + MS group. Micro-CT revealed increased bone volume/total volume and significantly reduced trabecular separation in HF + MS versus other groups. Histological analysis showed significantly higher HF + MS bone-to-implant contact (74.78 ± 4.40%) versus HF + AN (65.11 ± 5.10%) and machined samples (56.03 ± 3.23%). The maximal HF + MS pull-out force increased by 33.7% versus HF + AN.

CONCLUSIONS

These results indicated that HF + MS surfaces exhibited superior material property in terms of bonding strength and favorable implant osseointegration compared to other groups.

Effect of Hydrofluoric Acid Etching Time on Titanium Topography, Chemistry, Wettability, and Cell Adhesion

Titanium implant surface etching has proven an effective method to enhance cell attachment. Despite the frequent use of hydrofluoric (HF) acid, many questions remain unresolved, including the optimal etching time and its effect on surface and biological properties. The objective of this study was to investigate the effect of HF acid etching time on Ti topography, surface chemistry, wettability, and cell adhesion. These data are useful to design improved acid treatment and obtain an improved cell response. The surface topography, chemistry, dynamic wetting, and cell adhesiveness of polished Ti surfaces were evaluated after treatment with HF acid solution for 0, 2; 3, 5, 7, or 10 min, revealing a time-dependent effect of HF acid on their topography, chemistry, and wetting. Roughness and wetting increased with longer etching time except at 10 min, when roughness increased but wetness decreased. Skewness became negative after etching and kurtosis tended to 3 with longer etching time. Highest cell adhesion was achieved after 5–7 min of etching time. Wetting and cell adhesion were reduced on the highly rough surfaces obtained after 10-min etching time.

Substrate-Regulated Growth of Plasma-Polymerized Films on Carbide-Forming Metals

Although plasma polymerization is traditionally considered as a substrate-independent process, we present evidence that the propensity of a substrate to form carbide bonds regulates the growth mechanisms of plasma polymer (PP) films. The manner by which the first layers of PP films grow determines the adhesion and robustness of the film. Zirconium, titanium, and silicon substrates were used to study the early stages of PP film formation from a mixture of acetylene, nitrogen, and argon precursor gases. The correlation of initial growth mechanisms with the robustness of the films was evaluated through incubation of coated substrates in simulated body fluid (SBF) at 37° for 2 months. It was demonstrated that the excellent zirconium/titanium-PP film adhesion is linked to the formation of metallic carbide and oxycarbide bonds during the initial stages of film formation, where a 2D-like, layer-by-layer (Frank-van der Merwe) manner of growth was observed. On the contrary, the lower propensity of the silicon surface to form carbides leads to a 3D, island-like (Volmer-Weber) growth mode that creates a sponge-like interphase near the substrate, resulting in inferior adhesion and poor film stability in SBF. Our findings shed light on the growth mechanisms of the first layers of PP films and challenge the property of substrate independence typically attributed to plasma polymerized coatings.

Novel bioactive materials developed by simulated body fluid evaluation: Surface-modified Ti metal and its alloys

Until the discovery of the bone-bonding activity of Bioglass by Hench et al. in the early 1970s, it had not been demonstrated that a synthetic material could bond to living bone without eliciting a foreign body reaction. Since then, various kinds of materials based on calcium phosphate, such as sintered hydroxyapatite and β-tricalcium phosphate have also been shown to bond to living bone. Until the discovery of the bone-bonding activity of Ti metal formed with a sodium titanate surface layer by the present authors in 1996, it had not been shown that a metallic material could bond to living bone. Since then, various kinds of surface-modified Ti metal and its alloys have been found to bond to living bone. Until the discovery of the osteoinduction of porous hydroxyapatite by Yamasaki in 1990, it was unknown whether a synthetic material could induce bone formation even in muscle tissue. Since then, various kinds of porous calcium phosphate ceramics have been shown to induce osteoinduction. Until the discovery of osteoinduction induced by a porous Ti metal formed with a titanium oxide surface layer by Fujibayashi et al. in 2004, it had been unclear whether porous metals would be able to induce osteoinduction. These novel bioactive materials have been developed by systematic research into the apatite formation that occurs on surface-modified Ti metal and its related materials in an acellular simulated body fluid (SBF) having ion concentrations almost equal to those of human blood plasma. Some of the novel bioactive materials based on Ti metal are already in clinical use or clinical trials, such as artificial hip joints and spinal fusion devices. In the present paper, we review how these novel bioactive materials based on Ti metal have been developed based on an evaluation of apatite formation in SBF. Without the SBF evaluation, these novel bioactive materials would most likely never have been developed.

STATEMENT OF SIGNIFICANCE

On the basis of systematic study of apatite formation on a material in a simulated body fluid, various kinds of novel bioactive materials possessing not only bone-bonding activity and but also various other functions such as bone growth promotion, antibacterial activity and osteoinduction have been developed. Some of them are already successfully applied to clinical applications or trials for artificial hip joints and spinal fusion devices. It is shown in the present paper how these novel bioactive materials have been developed.

The synergistic effect of TiO2 nanoporous modification and platelet-rich plasma treatment on titanium-implant stability in ovariectomized rats

For several decades, titanium and its alloys have been commonly utilized for endosseous implantable materials, because of their good mechanical properties, chemical resistance, and biocompatibility. But associated low bone mass, wear and loss characteristics, and high coefficients of friction have limited their long-term stable performance, especially in certain abnormal bone-metabolism conditions, such as postmenopausal osteoporosis. In this study, we investigated the effects of platelet-rich plasma (PRP) treatment and TiO₂ nanoporous modification on the stability of titanium implants in osteoporotic bone. After surface morphology, topographical structure, and chemical changes of implant surface had been detected by scanning electron microscopy (SEM), atomic force microscopy, contact-angle measurement, and X-ray diffraction, we firstly assessed in vivo the effect of PRP treatment on osseointegration of TiO₂-modified implants in ovariectomized rats by microcomputed tomography examinations, histology, biomechanical testing, and SEM observation. Meanwhile, the potential molecular mechanism involved in peri-implant osseous enhancement was also determined by quantitative real-time polymerase chain reaction. The results showed that this TiO₂-modified surface was able to lead to improve bone implant contact, while PRP treatment was able to increase the implant surrounding bone mass. The synergistic effect of both was able to enhance the terminal force of implants drastically in biomechanical testing. Compared with surface modification, PRP treatment promoted earlier osteogenesis with increased expression of the RUNX2 and COL1 genes and suppressed osteoclastogenesis with increased expression of OPG and decreased levels of RANKL. These promising results show that PRP treatment combined with a TiO₂-nanomodified surface can improve titanium-implant biomechanical stability in ovariectomized rats, suggesting a beneficial effect to support the success of implants in osteoporotic bone.

Production of a biofunctional titanium surface using plasma electrolytic oxidation and glow-discharge plasma for biomedical applications

In this study, the authors tested the hypotheses that plasma electrolytic oxidation (PEO) and glow-discharge plasma (GDP) would improve the electrochemical, physical, chemical, and mechanical properties of commercially pure titanium (cpTi), and that blood protein adsorption on plasma-treated surfaces would increase. Machined and sandblasted surfaces were used as controls. Standard electrochemical tests were conducted in artificial saliva (pHs of 3.0, 6.5, and 9.0) and simulated body fluid. Surfaces were characterized by scanning electron microscopy, energy-dispersive spectroscopy, x-ray photoelectron spectroscopy, atomic force microscopy, x-ray diffraction, profilometry, Vickers microhardness, and surface energy. For biological assay, the adsorption of blood serum proteins (i.e., albumin, fibrinogen, and fibronectin) was tested. Higher values of polarization resistance and lower values of capacitance were noted for the PEO and GDP groups (p < 0.05). Acidic artificial saliva reduced the corrosion resistance of cpTi (p < 0.05). PEO and GDP treatments improved the surface properties by enrichment of the surface chemistry with bioactive elements and increased surface energy. PEO produced a porous oxide layer (5-μm thickness), while GDP created a very thin oxide layer (0.76-μm thickness). For the PEO group, the authors noted rutile and anatase crystalline structures that may be responsible for the corrosion barrier improvement and increased microhardness values. Plasma treatments were able to enhance the surface properties and electrochemical stability of titanium, while increasing protein adsorption levels.

Development of a novel biomimetic micro/nano-hierarchical interface for enhancement of osseointegration

In the present study, a novel biomimetic micro/nano-hierarchical interface was obtained and an unexpected trabecular bone-like interface was given.

Growth of Novel Ceramic Layers on Metals via Chemical and Heat Treatments for Inducing Various Biological Functions

The present authors' systematic studies on growth of novel ceramic layers on Ti metal and its alloys by chemical and heat treatments for inducing bone-bonding bioactivity and some other biological functions are reviewed. Ti metal formed an apatite on its surface in a simulated body fluid, when heat-treated after exposure to strong acid solutions to form rutile surface layer, or to strong alkali solutions to form sodium titanate surface layer. Both types of Ti metal tightly bonded to the living bone. The alkali and heat treatment was applied to the surface Ti metal of an artificial hip joint and successfully used in the clinic since 2007. The acid and heat treatments was applied to porous Ti metal to induce osteoconductivity as well as osteoinductivity. The resulting product was successfully used in clinical trials for spinal fusion devices. For the Ti-based alloys, the alkali and heat treatment was little modified to form calcium titanate surface layer. Bone-growth promoting Mg, Sr, and Zn ions as well as the antibacterial Ag ion were successfully incorporated into the calcium titanate layer.

Bioactive titanate layers formed on titanium and its alloys by simple chemical and heat treatments

To reveal general principles for obtaining bone-bonding bioactive metallic titanium, Ti metal was heat-treated after exposure to a solution with different pH. The material formed an apatite layer at its surface in simulated body fluid when heat-treated after exposure to a strong acid or alkali solution, because it formed a positively charged titanium oxide and negatively charged sodium titanate film on its surface, respectively. Such treated these Ti metals tightly bonded to living bone. Porous Ti metal heat-treated after exposure to an acidic solution exhibited not only osteoconductive, but also osteoinductive behavior. Porous Ti metal exposed to an alkaline solution also exhibits osteoconductivity as well as osteoinductivity, if it was subsequently subjected to acid and heat treatments. These acid and heat treatments were not effective for most Ti-based alloys. However, even those alloys exhibited apatite formation when they were subjected to acid and heat treatment after a NaOH treatment, since the alloying elements were removed from the surface by the latter. The NaOH and heat treatments were also not effective for Ti-Zr-Nb-Ta alloys. These alloys displayed apatite formation when subjected to CaCl₂ treatment after NaOH treatment, forming Ca-deficient calcium titanate at their surfaces after subsequent heat and hot water treatments. The bioactive Ti metal subjected to NaOH and heat treatments has been clinically used as an artificial hip joint material in Japan since 2007. A porous Ti metal subjected to NaOH, HCl and heat treatments has successfully undergone clinical trials as a spinal fusion device.

Effects of calcium phosphate nanocrystals on osseointegration of titanium implant in irradiated bone

Radiotherapy may compromise the integration of implant and cause implant loss. Implant surface modifications have the possibility of promoting cell attachment, cell growth, and bone formation which ultimately enhance the osseointegration process. The present study aimed to investigate the effects of calcium phosphate nanocrystals on implant osseointegration in irradiated bone. Sixteen rabbits were randomly assigned into control and nano-CaP groups, receiving implants with dual acid-etched surface or dual acid-etched surface discretely deposited of nanoscale calcium-phosphate crystals, respectively. The left leg of all the rabbits received 15 Gy radiation, followed by implants placement one week after. Four animals in each group were sacrificed after 4 and 12 weeks, respectively. Implant stability quotient (ISQ), ratio of bone volume to total volume (BV/TV), bone growth rate, and bone-to-implant contact (BIC) were evaluated. The nano-CaP group showed significantly higher ISQ (week 12, P = 0.031) and bone growth rate (week 6, P = 0.021; week 9, P = 0.001) than that in control group. No significant differences in BV/TV and BIC were found between two groups. Titanium implant surface modified with CaP nanocrystals provides a potential alternative to improve bone healing around implant in irradiated bone.

Effect of a hierarchical hybrid micro/nanorough strontium-loaded surface on osseointegration in osteoporosis

This study evaluated the effect of a hierarchical hybrid micro/nanorough titanium strontium-loaded (MNT-Sr) surface on osseointegration under osteoporotic conditions.

Estrogen deficiency does not decrease the in vitro osteogenic potential of rat adipose-derived mesenchymal stem cells

Osteoporosis due to estrogen deficiency is an increasing bone health issue worldwide: new strategies are being studied for regenerative medicine of bone pathologies in these patients. The most commonly used cells for tissue engineering therapy are the bone marrow mesenchymal stem cells (BMSCs), but they might be negatively affected by aging and estrogen deficiency. Besides the general advantages of adipose-derived mesenchymal stem cells (ADSCs) over BMSCs, ADSCs also seem to be less affected by aging than BMSCs, but in the literature, little is known about ADSCs in estrogen deficiency. The present study investigated the in vitro behavior of ADSCs, isolated from healthy (SHAM) and estrogen-deficient (OVX) rats. Phenotype, clonogenicity, viability, and osteogenic differentiation, at both cellular and molecular levels, were evaluated with or without osteogenic stimuli. Pro-inflammatory cytokines, growth factors, and adipogenic differentiation markers were also analyzed. There were no significant differences between OVX and SHAM ADSCs in some analyzed parameters. In addition, clonogenicity, osteopontin (Spp1) gene expression, alkaline phosphatase (ALP) activity at 2 weeks of culture, total collagen (COLL), osteocalcin (Bglap) gene expression and production, and matrix mineralization were significantly higher in OVX than in SHAM ADSCs. Besides the increase in some osteogenic markers, peroxisome proliferator-activated receptor gamma (Pparg) gene was also more expressed in OVX in osteogenic medium, with a concomitant estrogen receptor 1 (Esr1) gene expression decrease. These results underlined that ADSCs were not affected by estrogen deficiency in an osteogenic microenvironment.

Improving osseointegration of Co-Cr by nanostructured titanium coatings

This study reports the deposition of nanostructured Ti films on Co-Cr substrates to improve their surface characteristics and biocompatibility. The microstructure of the Ti films was controlled by application of negative substrate bias voltages. The surface roughness of Co-Cr implants was increased significantly after Ti coatings. The nanostructured Ti films are found to improve osteointergration of Co-Cr implants as indicated by enhancing cellular attachment, proliferation and differentiation, which was attributed mainly to the application of a biocompatible Ti coating, possessed a higher surface area for cell attachments and growth.

Smad7 modulates TGFβ signaling during cranial suture development to maintain suture patency

Craniosynostosis, the premature fusion of one or more sutures between the calvarial bones, is a common birth defect. Mutations in genes encoding receptors for the transforming growth factor-beta (TGFβ) family of signaling molecules have been associated with craniosynostosis, but how TGFβ signaling is regulated during suture development is not known. In the present study, we found that expression of Smad2 and Smad3, intracellular mediators of canonical TGFβ signaling, gradually increases during early postnatal suture development in rat in both the coronal suture (CS), which remains patent throughout life, and the posterior frontal suture (PFS), which undergoes programmed closure by postnatal day 22. The amounts of phosphorylated Smad2 and Smad3 proteins showed a similar gradual increase in the PFS and CS, but in the CS, Smad2/3 activation was suppressed after neonatal day 10. The suppression of Smad2/3 activation in the CS correlated with upregulation of Smad7 expression. We demonstrate that siRNA-mediated knockdown of Smad7 caused increased phosphorylation of Smad2 and Smad3 and induced osseous obliteration of the CS from postnatal days 10 to 22. The Smad7 siRNA-induced CS closure was associated with significantly increased levels of Fgf10 and phosphorylated ERK1/2 in the suture mesenchyme. Moreover, addition of the Erk1/2 inhibitor U0126 partially blocked Smad7-siRNA-induced CS closure. These findings suggest that canonical TGFβ signaling induces suture closure at least in part through activation of FGF and ERK signaling and that Smad7 plays an important role in maintaining suture patency by suppressing canonical TGFβ signaling during suture development.

Vitamin D3 and insulin combined treatment promotes titanium implant osseointegration in diabetes mellitus rats

This study investigated the effect of insulin and vitamin D(3) (VD(3)) treatment on implant osseointegration in diabetic mellitus (DM) rats. DM was induced by administration of streptozotocin in rats, which received implants insertion in the femur. Then animals were subjected to different treatment and divided to the following group: control, diabetic, insulin-treated diabetic, VD(3)-treated diabetic, insulin and VD(3) combination-treated diabetic rats. The glucose levels and weight of rats were periodically evaluated, and serum 25(OH)D(3) levels in rats were measured at the end of the experiment. Animals were sacrificed at 12 weeks after surgery, the peri-implant trabecular microstructure, implant fixation and implant osseointegration were measured by microscopic computerized tomography (micro-CT) evaluation, push-out test and histomorphometric analysis. Diabetic rats displayed significantly higher blood glucose level, lower body weight, lower serum 25(OH)D(3) levels, and less implant osseointegration than controls. Insulin treatment showed restorative effect on body weight and serum 25(OH)D(3) levels of diabetic rats, but the blood glucose level in diabetic rats were still substantially higher compared to controls after 14 days therapy of insulin. Combined treatment restored hyperglycemia in diabetic rats to be normal, and reversed the impaired osseointegration capacity of implants, with the bone volume ratio and percent osseointegration increased by 1.37-fold and 1.6-fold in micro-CT evaluation, the maximal push-out force and ultimate shear strength by 1.3-fold and 2.1-fold in push-out test, and the bone-to-implant contact and bone area ratio increased by 2.57-fold and 1.44-fold in histomorphometric analysis. Monotreatment also enhanced implant fixation, but less. These results indicated that insulin and VD(3) combined treatment may be an effective approach to enhance implant fixation in diabetic rats, but whether the results could be extrapolated to human needs further study.

Comparative molecular assessment of early osseointegration in implant-adherent cells

OBJECTIVE

The objective of our study is to identify the early molecular processes involved in osseointegration associated with a micro roughened and nanosurface superimposed featured implants.

MATERIALS AND METHODS

Thirty-two titanium implants with surface topographies exhibiting a micro roughened (AT-II) and nanosurface superimposed featured implants (AT-I) were placed in the tibiae of 8 rats and subsequently harvested at 2 and 4 days after placement. Total RNA was isolated from cells adherent to retrieved implants. A whole genome microarray using the Affymetrix Rat Gene 1.1 ST Array followed by validation of select genes through qRT-PCR was used to describe the gene expression profiles that were differentially regulated by the implant surfaces.

RESULTS

While significant differences at the gene level were not noted when comparing the two-implant surfaces at each time point, the microarray identified several genes that were differentially regulated at day 4 vs. day 2 for both implant surfaces. A total of 649 genes were differentially regulated at day 4 vs. day 2 in AT-I and 392 genes in AT-II implants. Functionally relevant categories related to ossification, skeletal system development, osteoblast differentiation, bone development, bone mineralization and biomineral tissue development were upregulated and more prominent at AT-I (day 4 vs. day 2) compared to AT-II. Analysis of the downregulated gene lists (day 4 vs. day 2) with average fold change >2 (were not statistically significant) revealed the biological processes involved with the inflammatory/immune response gene expression. The number of genes that were associated with the inflammatory/immune response category was greater for AT-I than AT-II.

CONCLUSIONS

The presence of nanosurface features modulated in vivo bone response. Gene regulation implicating osteogenesis as well as the inflammatory/immune responses that occur as a function of surface topography may affect bone mass shortly after implant placement.

Systematic review of pre-clinical models assessing implant integration in locally compromised sites and/or systemically compromised animals

OBJECTIVE

The aim was to systematically search the dental literature for pre-clinical models assessing implant integration in locally compromised sites (part 1) and systemically compromised animals (part 2), and to evaluate the quality of reporting of included publications.

METHODS

A Medline search (1966-2011) was performed, complimented by additional hand searching. The quality of reporting of the included publications was evaluated using the 20 items of the ARRIVE (Animals in Research In Vivo Experiments) guidelines.

RESULTS

One-hundred and seventy-six (part 1; mean ARRIVE score = 15.6 ± 2.4) and 104 (part 2; 16.2 ± 1.9) studies met the inclusion criteria. The overall mean score for all included studies amounted to 15.8 ± 2.2. Housing (38.3%), allocation of animals (37.9%), numbers analysed (50%) and adverse events (51.4%) of the ARRIVE guidelines were the least reported. Statistically significant differences in mean ARRIVE scores were found depending on the publication date (p < 0.05), with the highest score of 16.7 ± 1.6 for studies published within the last 2 years.

CONCLUSIONS

A large number of studies met the inclusion criteria. The ARRIVE scores revealed heterogeneity and missing information for selected items in more than 50% of the publications. The quality of reporting shifted towards better-reported pre-clinical trials within recent years.

In vitro osteogenic properties of two dental implant surfaces

Current dental implant research aims at understanding the biological basis for successful implant therapy. The aim of the study was to perform a full characterization of the effect of two commercial titanium (Ti) surfaces, OsseoSpeed and TiOblast, on the behaviour of mouse preosteoblast MC3T3-E1 cells. The effect of these Ti surfaces was compared with tissue culture plastic (TCP). In vitro experiments were performed to evaluate cytotoxicity, cell morphology and proliferation, alkaline phosphatase activity, gene expression, and release of a wide array of osteoblast markers. No differences were observed on cell viability and cell proliferation. However, changes were observed in cell shape after 2 days, with a more branched morphology on OsseoSpeed compared to TiOblast. Moreover, OsseoSpeed surface increased BMP-2 secretion after 2 days, and this was followed by increased IGF-I, BSP, and osterix gene expression and mineralization compared to TiOblast after 14 days. As compared to the gold standard TCP, both Ti surfaces induced higher osteocalcin and OPG release than TCP and differential temporal gene expression of osteogenic markers. The results demonstrate that the gain of using OsseoSpeed surface is an improved osteoblast differentiation and mineralization, without additional effects on cell viability or proliferation.

Identification of early response genes to roughness and fluoride modification of titanium implants in human osteoblasts

PURPOSE

Tissue response after implantation determines the success of the healing process. This response is not only dependent on the chemical properties of the implant surface but also by the surface topography or its roughness. Although in vitro and in vivo studies show improved results with rough- and fluoride-modified implants, the mechanisms behind these findings are still unknown.

METHODS AND MATERIALS

Here, we have used a two-step procedure to identify novel genes related to the early response of primary human osteoblasts to roughness and fluoride-modified titanium implants.

RESULTS

Two hundred seventeen genes responding to roughness were identified by microarray analysis and 198 genes responding to fluoride, 33 genes were common. Those identified genes related to bone and mineralization were further investigated by real-time reverse-transcriptase polymerase chain reaction. After 1 day of culture, toll-like receptor 3, ankylosis-progressive homolog, decorin, osteocalcin, and runt-related transcription factor-2 were classified as responsive genes to roughness; Distal-less homeobox-2 and Tuftelin-1 as responsive genes to fluoride treatment. Responsive genes to both treatments were collagen type I, parathyroid hormone-like hormone, hairy and enhancer of split-1, follistatin, ectonucleotide pyrophosphatase/phosphodiesterase-1, and thyroid hormone receptor-alpha.

CONCLUSION

Our strategy was useful for identifying novel genes that might be involved in the early response of osteoblasts to rough and fluoride-modified titanium implants.

Bone regeneration related to calcium phosphate-coated implants in osteoporotic animal models: a meta-analysis

BACKGROUND

Osteoporosis is a frequent human metabolic bone disorder. Prospectively, global ageing of populations will lead to a major increase of subjects being diagnosed with osteoporosis and in need for dental rehabilitation. However, as local osteoporosis of the jaws affects bone quantity and quality of edentulous regions, osseointegration of dental implants might be hampered. Consequently, calcium phosphate ceramic-coated implants have been suggested to compensate for low bone quantity/density and for impaired bone healing in osteoporosis. Nonetheless, up to now no meta-analytical assessment of the relevant preclinical literature to quantify such a possible positive effect has been undertaken.

MATERIALS AND METHODS

PubMed search, limited to animal models, to identify a possible positive effect of calcium phosphate-coated implants on bone regeneration, was carried out. Further, the reference lists of related review articles and publications selected for inclusion in this review were systematically screened. The primary outcome variables were bone-to-implant contact percentage as assessed histomorphometrically and mechanical stability testing.

RESULTS

The electronic search in the database of the National Library of Medicine resulted in the identification of 2704 titles. These titles were initially screened by the two independent reviewers for possible inclusion, resulting in further consideration of 51 publications. Screening the abstracts led to 22 full-text articles. From these articles, 16 reports were excluded. Finally, six of these original research reports could be selected for evaluation. Additionally, eight publications were identified by manual search. Thus, a total of 14 articles were included for analysis.

CONCLUSIONS

It was concluded that (1) in osteoporotic animal models calcium phosphate ceramic-coated implants are associated with improved bone-to-implant healing as compared to noncoated implants. Moreover, (2) essentially due to quality characteristics of the analyzed original research articles a negative impact of osteoporosis on bone-to-implant healing could not be confirmed. Besides, (3) the established positive bone-to-implant healing effect of calcium phosphate ceramic coatings does not differ between osteoporotic and nonosteoporotic, healthy animal models.