Increased bone contact to a calcium-incorporated oxidized commercially pure titanium implant: an in-vivo study in rabbits

Fusion peptide engineered "statically-versatile" titanium implant simultaneously enhancing anti-infection, vascularization and osseointegration

Although antimicrobial titanium implants can prevent biomaterial-associated infection (BAI) in orthopedics, they display cytotoxicity and delayed osseointegration. Therefore, versatile implants are desirable for simultaneously inhibiting BAI and promoting osseointegration, especially "statically-versatile" ones with nonessential external stimulations for facilitating applications. Herein, we develop a "statically-versatile" titanium implant by immobilizing an innovative fusion peptide (FP) containing HHC36 antimicrobial sequence and QK angiogenic sequence via sodium borohydride reduction promoted Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC-SB), which shows higher immobilization efficiency than traditional CuAAC with sodium ascorbate reduction (CuAAC-SA). The FP-engineered implant exhibits over 96.8% antimicrobial activity against four types of clinical bacteria (S. aureus, E. coli, P. aeruginosa and methicillin-resistant S. aureus), being stronger than that modified with mixed peptides. This can be mechanistically attributed to the larger bacterial accessible surface area of HHC36 sequence. Notably, the implant can simultaneously enhance cellular proliferation, up-regulate expressions of angiogenesis-related genes/proteins (VEGF and VEGFR-2) of HUVECs and osteogenesis-related genes/proteins (ALP, COL-1, RUNX-2, OPN and OCN) of hBMSCs. In vivo assay with infection and non-infection bone-defect model reveals that the FP-engineered implant can kill 99.63% of S. aureus, and simultaneously promote vascularization and osseointegration. It is believed that this study presents an excellent strategy for developing "statically-versatile" orthopedic implants.

The feasibility of eco-friendly electrical discharge machining for surface modification of Ti: A comparison study in surface properties, bioactivity, and cytocompatibility

This study provided an eco-friendly manufacturing method for Ti implants by combining machining and surface treatment processes. Ti was machined by electrical discharge machining (EDM) in a water-based dielectric in order to reduce environmental impact and improve operational health. The feasibility of this eco-friendly EDM was evaluated by tested the bioactivity and cytocompatibility of the EDM-treated Ti and the commercially micro-arc oxidation (MAO)-treated Ti was used as a control group. Pulsed MAO and EDM treatments were applied on Ti in an aqueous solution containing hydroxyapatite (HA) with the same concentration (30 g/L) under the same voltage and treatment period. The two surface modification processes were compared from the aspects of surface composition, coating structure, and coating adhesion. Furthermore, in vitro bioactivity and cellular biocompatibility of the MAO- and EDM-treated Ti films were tested. Both treatments produced Ti oxide containing Ca and P on Ti, and the EDM-formed film possessed more Ca, with its Ca/P value closer to HA, as compared to the MAO-formed film. The MAO-formed films had micropores and nanopores in the middle region and film/substrate interface, respectively. Pores only existed on the surface of the EDM-formed films. The MAO-formed films were fractured, but the EDM-formed films maintained their original structure under tensile stress, tested according to the ASTM C633 standard. The bioactivity of the EDM-treated surface was higher than that of the MAO-treated and untreated Ti surface. After 24 h cell incubation, the EDM-treated surface exhibited a significantly higher number of cells than untreated Ti and the MAO-treated surface.

PHYSICOCHEMICAL CHARACTERIZATION: COMPARATIVE EVALUATION OF ALLOGRAFT BIOMATERIALS AND AUTOGENOUS BONE

Objectives: bone substitutes used in oral surgery include allografts, xenografts and synthetic materials that are frequently used to compensate bone loss or to reinforce repaired bone by encouraging new bone ingrowth into the defect site. The aim of this study was to evaluate a number ofphysical and chemical properties in a variety of allografts biomaterials used in oral surgery and to compare them with those of autogenous bone. Materials and methods: autogenous bone andfive different allograft biomaterials were studied by high-resolution X-ray diffractometry, atomic absorption spectrometry, laser diffraction, and checked for their chemical composition, calcium release concentration, crystallinity and granulation size. Results: the highest calcium release concentration was 24.94 mg/gforPuros® and the lowest one was 4.05 mg/gfor OsteoSponge® compared to 20.15 mg/g to natural bone. The range ofparticles size, in term of median size D50, varied between 394.24 pm for DIZG Spongiosa® and 902.41 pm for OsteoSponge®, compared to 282.1 pm for natural bone. Bone and Puros® displayed a hexagonal shape as bone except and OsteoSponge® which showed a triclinic shape and all the rest showed monoclinic shape. Conclusion: a bone substitute of choice depends largely on its clinical application that is associated to its biological and mechanical performance. These morphological differences between biomaterials greatly influence their in-vivo behavior of biomaterials. Significant differences were detected in terms of calcium concentration, particles size, and crystallinity.

Synergistic effect of nanotopography and bioactive ions on peri-implant bone response

Both bioactive ion chemistry and nanoscale surface modifications are beneficial for enhanced osseointegration of endosseous implants. In this study, a facile synthesis approach to the incorporation of bioactive Ca²⁺ ions into the interlayers of nanoporous structures (Ca-nano) formed on a Ti6Al4V alloy surface was developed by sequential chemical and heat treatments. Samples with a machined surface and an Na⁺ ion-incorporated nanoporous surface (Na-nano) fabricated by concentrated alkali and heat treatment were used in parallel for comparison. The bone response was investigated by microcomputed tomography assessment, sequential fluorescent labeling analysis, and histological and histomorphometric evaluation after 8 weeks of implantation in rat femurs. No significant differences were found in the nanotopography, surface roughness, or crystalline properties of the Ca-nano and Na-nano surfaces. Bone–implant contact was better in the Ca-nano and Na-nano implants than in the machined implant. The Ca-nano implant was superior to the Na-nano implant in terms of enhancing the volume of new bone formation. The bone formation activity consistently increased for the Ca-nano implant but ceased for the Na-nano implant in the late healing stage. These results suggest that Ca-nano implants have promising potential for application in dentistry and orthopedics.

Cytotoxicity of Titanate-Calcium Complexes to MC3T3 Osteoblast-Like Cells

Monosodium titanates (MST) are a relatively novel form of particulate titanium dioxide that have been proposed for biological use as metal sorbents or delivery agents, most recently calcium (II). In these roles, the toxicity of the titanate or its metal complex is crucial to its biological utility. The aim of this study was to determine the cytotoxicity of MST and MST-calcium complexes with MC3T3 osteoblast-like cells; MST-Ca(II) complexes could be useful to promote bone formation in various hard tissue applications. MC3T3 cells were exposed to native MST or MST-Ca(II) complexes for 24–72 h. A CellTiter-Blue® assay was employed to assess the metabolic activity of the cells. The results showed that MST and MST-Ca(II) suppressed MC3T3 metabolic activity significantly in a dose-, time-, and cell-density-dependent fashion. MST-Ca(II) suppressed MC3T3 metabolism in a statistically identical manner as native MST at all concentrations. We concluded that MST and MST-Ca(II) are significantly cytotoxic to MC3T3 cells through a mechanism yet unknown; this is a potential problem to the biological utility of these complexes.

Classification and Effects of Implant Surface Modification on the Bone: Human Cell-Based In Vitro Studies

Implant surfaces are continuously being improved to achieve faster osseointegration and a stronger bone to implant interface. This review will present the various implant surfaces, the parameters for implant surface characterization, and the corresponding in vitro human cell-based studies determining the strength and quality of the bone-implant contact. These in vitro cell-based studies are the basis for animal and clinical studies and are the prelude to further reviews on how these surfaces would perform when subjected to the oral environment and functional loading.

Precipitation of Calcium Phosphates in the Presence of Collagen Type I on Four Different Bioactive Titanium Surfaces: an in Vitro Study

OBJECTIVES

To compare the properties of calcium phosphate precipitation on four different bioactive surface preparations and one control surface in the simulated body fluid model with added collagen type I.

MATERIAL AND METHODS

Blasted titanium discs were treated with four different surface modifications, alkali and heat, sodium fluoride, anodic oxidation and hydroxyapatite coating. The discs were divided into five groups where one group, the blasted, served as control. The discs were immersed in simulated body fluid and collagen for 24 h, 3 days, 1 week and 2 weeks and then analysed by optical interferometry, scanning electron microscopy/energy dispersive X-ray analysis and X-ray photoelectron spectroscopy.

RESULTS

All surfaces show small precipitates after 3 days which with longer immersion times increase. After 2 weeks the surfaces were completely covered with precipitates, and Ca/P ratios were approximately 1.3, independently on surface preparation. The fluoridated discs showed significantly (P ≤ 0.05) higher degree of CaP after one week of immersion as compared to the other surface preparations. The collagen type I content increased with time, as reflected by increased nitrogen content.

CONCLUSIONS

The results from this study indicate that a fluoridated titanium surface may favour precipitation of calcium phosphate in the presence of collagen type I, as compared to the other surface treatments of the present study.

Bioactivity and Surface Characteristics of Titanium Implants Following Various Surface Treatments: An In Vitro Study

This study compared the surface topography, hydrophilicity, and bioactivity of titanium implants after 3 different surface treatments (sandblasting and acid etching, modified sandblasting and acid etching, and thermal oxidation) with those of machined implants. One hundred indigenously manufactured threaded titanium implants were subjected to 3 methods of surface treatment. The surface roughness of the nontreated (Group A) and treated samples (Groups B through D) was evaluated with a scanning electron microscope (SEM) and profilometer. The wettability was visually examined using a colored dye solution. The calcium ions attached to the implant surface after immersing in simulated body fluid (SBF) were assessed on days 1, 2, and 7 with an atomic electron spectroscope. The data were analyzed statistically. The SBF test allowed the precipitation of a calcium phosphate layer on all surface-treated samples, as evidenced in the SEM analysis. A significantly higher amount of calcium ions and increased wettability were achieved in the thermally oxidized samples. The mean roughness was significantly lower in Group A (0.85 ± 0.07) compared to Group B (1.35 ± 0.17), Group C (1.40 ± 0.14), and Group D (1.36 ± 0.18). The observations from this in vitro study indicated that surface treatment of titanium improved the bioactivity. Moreover, results identified the implants that were sandblasted, acid etched, and then oxidized attracted more calcium ions.

Osseointegration: hierarchical designing encompassing the macrometer, micrometer, and nanometer length scales

OBJECTIVE

Osseointegration has been a proven concept in implant dentistry and orthopedics for decades. Substantial efforts for engineering implants for reduced treatment time frames have focused on micrometer and most recently on nanometer length scale alterations with negligible attention devoted to the effect of both macrometer design alterations and surgical instrumentation on osseointegration. This manuscript revisits osseointegration addressing the individual and combined role of alterations on the macrometer, micrometer, and nanometer length scales on the basis of cell culture, preclinical in vivo studies, and clinical evidence.

METHODS

A critical appraisal of the literature was performed regarding the impact of dental implant designing on osseointegration. Results from studies with different methodological approaches and the commonly observed inconsistencies are discussed.

RESULTS

It is a consensus that implant surface topographical and chemical alterations can hasten osseointegration. However, the tailored combination between multiple length scale design parameters that provides maximal host response is yet to be determined.

SIGNIFICANCE

In spite of the overabundant literature on osseointegration, a proportional inconsistency in findings hitherto encountered warrants a call for appropriate multivariable study designing to ensure that adequate data collection will enable osseointegration maximization and/or optimization, which will possibly lead to the engineering of endosteal implant designs that can be immediately placed/loaded regardless of patient dependent conditions.

Nanometer scale titanium surface texturing are detected by signaling pathways involving transient FAK and Src activations

Background

It is known that physico/chemical alterations on biomaterial surfaces have the capability to modulate cellular behavior, affecting early tissue repair. Such surface modifications are aimed to improve early healing response and, clinically, offer the possibility to shorten the time from implant placement to functional loading. Since FAK and Src are intracellular proteins able to predict the quality of osteoblast adhesion, this study evaluated the osteoblast behavior in response to nanometer scale titanium surface texturing by monitoring FAK and Src phosphorylations.

Methodology

Four engineered titanium surfaces were used for the study: machined (M), dual acid-etched (DAA), resorbable media microblasted and acid-etched (MBAA), and acid-etch microblasted (AAMB). Surfaces were characterized by scanning electron microscopy, interferometry, atomic force microscopy, x-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy. Thereafter, those 4 samples were used to evaluate their cytotoxicity and interference on FAK and Src phosphorylations. Both Src and FAK were investigated by using specific antibody against specific phosphorylation sites.

Principal Findings

The results showed that both FAK and Src activations were differently modulated as a function of titanium surfaces physico/chemical configuration and protein adsorption.

Conclusions

It can be suggested that signaling pathways involving both FAK and Src could provide biomarkers to predict osteoblast adhesion onto different surfaces.

Osteoconductive Potential of Mesoporous Titania Implant Surfaces Loaded with Magnesium: An Experimental Study in the Rabbit

BACKGROUND

Mesoporous coatings enable incorporation of functional substances and sustainedly release them at the implant site. One bioactive substance that can be incorporated in mesoporous is magnesium, which is strongly involved in bone metabolism and in osteoblast interaction.

PURPOSE

The aim of this experimental study was to evaluate the effect of incorporation of magnesium into mesoporous coatings of oral implants on early stages of osseointegration.

MATERIAL AND METHODS

Titanium implants were coated with thin films of mesoporous TiO2 having pore diameters of 6 nm and were loaded with magnesium. The implant surfaces were extensively characterized by means of interferometry, atomic force microscopy, scanning electron microscopy, and energy-dispersive spectroscopy and then placed in the tibiae of 10 rabbits. After 3 weeks of healing, osseointegration was evaluated by means of removal torque testing and histology and histomorphometry.

RESULTS

Histological and biomechanical analyses revealed no side effects and successful osseointegration of the implants. The biomechanical evaluation evidenced a significant effect of magnesium doping on strengthening the implant-bone interface.

CONCLUSIONS

A local release of magnesium from the implant surfaces enhances implant retention at the early stage of healing (3 weeks after implantation), which is highly desirable for early loading of the implant.

In vitro evaluation of human fetal osteoblast response to magnesium loaded mesoporous TiO2 coating

This work aimed to evaluate the in vitro response of Transfected Human Foetal Osteoblast (hFOB) cultured on a magnesium-loaded mesoporous TiO2 coating. The application of mesoporous films on titanium implant surfaces has shown very promising potential to enhance osseointegration. This type of coating has the ability to act as a framework to sustain bioactive agents and different drugs. Magnesium is the element that, after calcium, is the most frequently used to dope titanium implant surfaces, since it is crucial for protein formation, growth factor expression, and aids for bone mineral deposition on implant surfaces. Mesoporous TiO2 films with an average pore-size of 6 nm were produced by the evaporation-induced self-assembly method (EISA) and deposited onto titanium discs. Magnesium loading was performed by soaking the mesoporous TiO2 discs in a magnesium chloride solution. Surface characterization was conducted by SEM, XPS, optical interferometry, and AFM. Magnesium release profile was assessed at different time points using a Magnesium Detection kit. Cell morphology and spreading were observed with SEM. The cytoskeletal organization was stained with TRITC-conjugated Phalloidin and cell viability was evaluated through a mitochondrial colorimetric (MTT) assay. Furthermore, gene expression of bone markers and cell mineralization were analyzed by real time RT-PCR and alizarin-red staining, respectively. The surface chemical analysis by XPS revealed the successful adsorption of magnesium to the mesoporous coating. The AFM measurements revealed the presence of a nanostructured surface roughness. Osteoblasts viability and adhesion as well as the gene expression were unaffected by the addition of magnesium possibly due to its rapid burst release, however, were enhanced by the 3D nanostructure of the TiO2 layer.

Implications of Surface and Bulk Properties of Abutment Implants and Their Degradation in the Health of Periodontal Tissue

The aim of the current review was to investigate the implications of the surface and bulk properties of abutment implants and their degradation in relation to periodontal health. The success of dental implants is no longer a challenge for dentistry. The scientific literature presents several types of implants that are specific for each case. However, in cases of prosthetics components, such as abutments, further research is needed to improve the materials used to avoid bacterial adhesion and enhance contact with epithelial cells. The implanted surfaces of the abutments are composed of chemical elements that may degrade under different temperatures or be damaged by the forces applied onto them. This study showed that the resulting release of such chemical elements could cause inflammation in the periodontal tissue. At the same time, the surface characteristics can be altered, thus favoring biofilm development and further increasing the inflammation. Finally, if not treated, this inflammation can cause the loss of the implant.

Apatite-forming ability of titanium in terms of pH of the exposed solution

In order to elucidate the main factor governing the capacity for apatite formation of titanium (Ti), Ti was exposed to HCl or NaOH solutions with different pH values ranging from approximately 0 to 14 and then heat-treated at 600°C. Apatite formed on the metal surface in a simulated body fluid, when Ti was exposed to solutions with a pH less than 1.1 or higher than 13.6, while no apatite formed upon exposure to solutions with an intermediate pH value. The apatite formation on Ti exposed to strongly acidic or alkaline solutions is attributed to the magnitude of the positive or negative surface charge, respectively, while the absence of apatite formation at an intermediate pH is attributed to its neutral surface charge. The positive or negative surface charge was produced by the effect of either the acidic or alkaline ions on Ti, respectively. It is predicted from the present results that the bone bonding of Ti depends upon the pH of the solution to which it is exposed, i.e. Ti forms a bone-like apatite on its surface in the living body and bonds to living bone through the apatite layer upon heat treatment after exposure to a strongly acidic or alkaline solution.

Osseointegration of two different phosphate ion-containing titanium oxide surfaces in rabbit cancellous bone

OBJECTIVE

This study assessed the osseointegration of grit-blasted titanium (Ti) implants with a hydrophilic phosphate ion-incorporated oxide surface in rabbit cancellous bone, and compared its bone healing with commercially available phosphate-incorporated clinical implants obtained by micro-arc oxidation (TiUnite, TU implant).

MATERIAL AND METHODS

The hydrophilic phosphate-incorporated Ti surface (P implant) was produced by hydrothermal treatment on grit-blasted moderately rough-surfaced clinical implant. The TU surface was used as a control. The surface characteristics were evaluated by field emission-scanning electron microscopy, X-ray photoelectron spectroscopy, optical profilometry, and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Thirty-two threaded implants with lengths of 10 and 3.3 mm diameter (16 P implants and 16 TU implants) were placed in the femoral condyles of 16 New Zealand White rabbits. Histomorphometric analysis, removal torque tests, and surface analysis of the torque-tested implants were performed 4 weeks after implantation.

RESULTS

The P and TU implants displayed micro-rough surface features with similar Ra values at the micron-scale. ICP-AES analysis revealed that both the P and TU implants released phosphate ions into the solution. The torque-tested P and TU implants exhibited a considerable quantity of bone attached to the surface. The P implants exhibited significantly higher bone-implant contact percentages, both in terms of the all threads region and the total lateral length of implants compared with the TU implants (P < 0.01), but no statistical difference was found for the removal torque values.

CONCLUSION

These results suggest that the phosphate-incorporated Ti oxide surface obtained by hydrothermal treatment achieves rapid osseointegration in cancellous bone by increasing the degree of bone-implant contact.

Nanostructured positively charged bioactive TiO2 layer formed on Ti metal by NaOH, acid and heat treatments

Nanometer-scale roughness was generated on the surface of titanium (Ti) metal by NaOH treatment and remained after subsequent acid treatment with HCl, HNO(3) or H(2)SO(4) solution, as long as the acid concentration was not high. It also remained after heat treatment. Sodium hydrogen titanate produced by NaOH treatment was transformed into hydrogen titanate after subsequent acid treatment as long as the acid concentration was not high. The hydrogen titanate was then transformed into titanium oxide (TiO(2)) of anatase and rutile by heat treatment. Treated Ti metals exhibited high apatite-forming abilities in a simulated body fluid especially when the acid concentration was greater than 10 mM, irrespective of the type of acid solutions used. This high apatite-forming ability was maintained in humid environments for long periods. The high apatite-forming ability was attributed to the positive surface charge that formed on the TiO(2) layer and not to the surface roughness or a specific crystalline phase. This positively charged TiO(2) induced apatite formation by first selectively adsorbing negatively charged phosphate ions followed by positively charged calcium ions. Apatite formation is expected on the surfaces of such treated Ti metals after short periods, even in living systems. The bonding of metal to living bone is also expected to take place through this apatite layer.

Effect of nanoporous TiO2 coating and anodized Ca2+ modification of titanium surfaces on early microbial biofilm formation

Background

The soft tissue around dental implants forms a barrier between the oral environment and the peri-implant bone and a crucial factor for long-term success of therapy is development of a good abutment/soft-tissue seal. Sol-gel derived nanoporous TiO₂ coatings have been shown to enhance soft-tissue attachment but their effect on adhesion and biofilm formation by oral bacteria is unknown.

Methods

We have investigated how the properties of surfaces that may be used on abutments: turned titanium, sol-gel nanoporous TiO₂ coated surfaces and anodized Ca²⁺ modified surfaces, affect biofilm formation by two early colonizers of the oral cavity: Streptococcus sanguinis and Actinomyces naeslundii. The bacteria were detected using 16S rRNA fluorescence in situ hybridization together with confocal laser scanning microscopy.

Results

Interferometry and atomic force microscopy revealed all the surfaces to be smooth (S_a ≤ 0.22 μm). Incubation with a consortium of S. sanguinis and A. naeslundii showed no differences in adhesion between the surfaces over 2 hours. After 14 hours, the level of biofilm growth was low and again, no differences between the surfaces were seen. The presence of saliva increased the biofilm biovolume of S. sanguinis and A. naeslundii ten-fold compared to when saliva was absent and this was due to increased adhesion rather than biofilm growth.

Conclusions

Nano-topographical modification of smooth titanium surfaces had no effect on adhesion or early biofilm formation by S. sanguinis and A. naeslundii as compared to turned surfaces or those treated with anodic oxidation in the presence of Ca²⁺. The presence of saliva led to a significantly greater biofilm biovolume but no significant differences were seen between the test surfaces. These data thus suggest that modification with sol-gel derived nanoporous TiO_2, which has been shown to improve osseointegration and soft-tissue healing in vivo, does not cause greater biofilm formation by the two oral commensal species tested than the other surfaces.

Preparation of bioactive Ti metal surface enriched with calcium ions by chemical treatment

A calcium solution treatment was applied to a NaOH-treated titanium metal to give it bioactivity, scratch resistance and moisture resistance. The titanium metal was soaked in a 5 M NaOH solution and then a 100 mM CaCl(2) solution to incorporate Ca(2+) ions into the titanium metal surface by ion exchange. This treated titanium metal was subsequently heated at 600 degrees C and soaked in hot water at 80 degrees C. The NaOH treatment incorporated approximately 5 at.% Na(+) ions into the Ti metal surface. These Na(+) ions were completely replaced by Ca(2+) ions by the CaCl(2) treatment. The number of Ca(2+) ions remained even after subsequent heat and water treatments. Although the NaOH-CaCl(2)-treated titanium metal showed slightly higher apatite-forming ability in a simulated body fluid than the NaOH-treated titanium metal, it lost its apatite-forming ability during the heat treatment. However, subsequent water or autoclave treatment restored the apatite-forming ability of the NaOH-CaCl(2)-heat-treated titanium metal. Although the apatite-forming ability of the NaOH-heat-treated titanium metal decreased dramatically when it was kept at high humidity, that of NaOH-CaCl(2)-heat-water-treated titanium metal was maintained even in the humid environment. The heat treatment increased the critical scratch resistance of the surface layer of the NaOH-CaCl(2)-treated titanium metal remarkably, and it did not deteriorate on subsequent water treatment.