Titanium--the material of choice?

Finite element analysis of the mechanical performance of self-expanding endovascular stents made with new nickel-free superelastic β-titanium alloys

New Ni-free superelastic β-titanium alloys from the Ti-Zr-Nb-Sn system have been designed in this study to replace the NiTi alloy currently used for self-expanding endovascular stents. The simulation results, carried out by finite element analysis (FEA) on two β-type Ti-Zr-Nb-Sn alloys using a commonly used superelastic constitutive model, were in good agreement with the experimental uniaxial tension data. An ad-hoc self-expanding coronary stent was specifically designed for the present study. To assess the mechanical performance of the endovascular stents, a FEA framework of the stent deployed in the arterial system was established, and a simply cyclic bending loading was proposed. Six comparative simulations of three superelastic materials (including NiTi for comparison) and two arterial configurations were successfully conducted. The mechanical behaviours of the stents were analysed through stress localization, the increase in artery diameter, contact results, and distributions of mean and alternating strain. The simulation results show that the Ti-22Zr-11Nb-2Sn (at. %) alloy composition for the stent produces the largest contact area (9.92 mm2) and radial contact force (49.5 mN) on the inner surface of the plaque and a higher increase in the stenotic artery diameter (70 %) after three vascular bending cycles. Furthermore, the Ti-22Zr-11Nb-2Sn stent exhibited sufficient crimping capacity and reliable mechanical performance during deployment and cyclic bending, which could make it a suitable choice for self-expanding coronary stents. In this work, the implementation of finite element analysis has thus made it possible to propose a solid basis for the mechanical evaluation of these stents fabricated in new Ni-free superelastic β-Ti alloys.

Fibroblasts and osteoblasts behavior after contact with different titanium surfaces used as implant abutment: An in vitro experimental study

Background

The goal of this in vitro study was to compare three different surfaces: two types of implant surfaces commercially available ([a] smooth/machined and [b] acid-treated surface) versus (c) anodized surface. Discs were manufactured with commercially pure titanium (CP) grade IV, which were subsequently analyzed by scanning microscopy and fibroblastic and osteoblastic cell cultures.

Methods

Ninety-nine discs (5 × 2 mm) were manufactured in titanium grade IV and received different surface treatments: (i) Mach group: machined; (ii) AA group: double acid etch; and (iii) AN group: anodizing treatment. Three discs from each group were analyzed by Scanning Electron Microscopy (SEM) to obtain surface topography images and qualitatively analyzed by EDS. Balb/c 3T3 fibroblasts and pre-osteoblastic cells (MC3T3-E1 lineage) were used to investigate each group's biological response (n = 10/cellular type). The data were compared statistically using the ANOVA one-way test, considered as a statistically significant difference p < 0.05.

Results

The AA group had numerous micropores with diameters between 5 and 10 μm, while nanopores between 1 and 5 nm were measured in the AN group. The EDX spectrum showed a high titanium concentration in all the analyzed samples. The contact angle and wetting tension were higher in the AA, whereas similar results were observed for the other groups. A lower result was observed for base width in the AA, which was higher in the other two groups. The AN showed the best values in the fibroblast cells, followed by Mach and AA; whereas, in the culture of the MC3T3 cells, the result was precisely the opposite (AA > Mach > AN). There was similar behavior for cell adhesion for the test groups (Mach and AN), with greater adhesion of Balb/c 3T3 fibroblasts compared to MC3T3 cells; in the AA group, there was greater adherence for MC3T3 cells compared to Balb/c 3T3 fibroblasts.

Conclusions

The findings suggest that different surface characteristics can produce different biological responses, possibly cell-line dependent. These findings have important implications for the design of implantable medical devices, where the surface characteristics can significantly impact its biocompatibility.

Clinical outcomes of zirconia implants: a systematic review and meta-analysis

PURPOSE

To assess the clinical outcomes of zirconia dental implants based on an updated systematic literature review.

METHODS

An electronic search was performed in three databases, last updated in June 2023, supplemented by hand searching. The eligibility criteria were clinical studies reporting patients rehabilitated with zirconia implants. The cumulative survival rate (CSR) of implants was calculated. A meta-analysis for marginal bone loss (MBL) under different follow-up times and a meta-regression assessing the relationship between mean MBL and follow-up were done.

RESULTS

Twenty-five studies were included (4017 implants, 2083 patients). Seven studies had follow-up longer than 60 months. 172 implants failed, after a mean of 12.0 ± 16.1 months (min-max 0.3-86.0), of which 47 early failures, and 26 due to implant fracture, the majority in narrow-diameter implants. The 10-year CSR was 95.1%. Implants with coronal part prepared by drills presented statistically significant lower survival than non-prepared implants (p < 0.001). Two-piece implants presented lower survival than one-piece implants (p = 0.017). Implants discontinued from the market presented lower survival than the commercially available ones (p < 0.001). The difference in survival was not significant between implants in maxilla and mandible (p = 0.637). The mean MBL fluctuated between 0.632 and 2.060 mm over long periods of observation (up until 132 months). There was an estimated MBL increase of 0.005 mm per additional month of follow-up.

CONCLUSION

Zirconia implants present high 10-year CSR and short-term low MBL. The review was registered in PROSPERO (CRD42022342055).

CLINICAL RELEVANCE

The clinical outcomes observed for zirconia dental implants are very promising, although these have not yet been extensively studied as titanium alloy implants.

Bone marrow stromal cells generate an osteoinductive microenvironment when cultured on titanium-aluminum-vanadium substrates with biomimetic multiscale surface roughness

Osseointegration of titanium-based implants possessing complex macroscale/microscale/mesoscale/nanoscale (multiscale) topographies support a direct and functional connection with native bone tissue by promoting recruitment, attachment and osteoblastic differentiation of bone marrow stromal cells (MSCs). Recent studies show that the MSCs on these surfaces produce factors, including bone morphogenetic protein 2 (BMP2) that can cause MSCs not on the surface to undergo osteoblast differentiation, suggesting they may produce an osteogenic environmentin vivo. This study examined if soluble factors produced by MSCs in contact with titanium-aluminum-vanadium (Ti6Al4V) implants possessing a complex multiscale biomimetic topography are able to induce osteogenesis ectopically. Ti6Al4V disks were grit-blasted and acid-etched to create surfaces possessing macroscale and microscale roughness (MM), micro/meso/nanoscale topography (MN), and macro/micro/meso/nanoscale topography (MMN^TM). Polyether-ether-ketone (PEEK) disks were also fabricated by machining to medical-grade specifications. Surface properties were assessed by scanning electron microscopy, contact angle, optical profilometry, and x-ray photoelectron spectroscopy. MSCs were cultured in growth media (GM). Proteins and local factors in their conditioned media (CM) were measured on days 4, 8, 10 and 14: osteocalcin, osteopontin, osteoprotegerin, BMP2, BMP4, and cytokines interleukins 6, 4 and 10 (IL6, IL4, and IL10). CM was collected from D14 MSCs on MMN^TMand tissue culture polystyrene (TCPS) and lyophilized. Gel capsules containing active demineralized bone matrix (DBM), heat-inactivated DBM (iDBM), and iDBM + MMN-GM were implanted bilaterally in the gastrocnemius of athymic nude mice (N= 8 capsules/group). Controls included iDBM + GM; iDBM + TCPS-CM from D5 to D10 MSCs; iDBM + MMN-CM from D5 to D10; and iDBM + rhBMP2 (R&D Systems) at a concentration similar to D5-D10 production of MSCs on MMN^TMsurfaces. Legs were harvested at 35D. Bone formation was assessed by micro computed tomography and histomorphometry (hematoxylin and eosin staining) with the histology scored according to ASTM 2529-13. DNA was greatest on PEEK at all time points; DNA was lowest on MN at early time points, but increased with time. Cells on PEEK exhibited small changes in differentiation with reduced production of BMP2. Osteoblast differentiation was greatest on the MN and MMN^TM, reflecting increased production of BMP2 and BMP4. Pro-regenerative cytokines IL4 and IL10 were increased on Ti-based surfaces; IL6 was reduced compared to PEEK. None of the media from TCPS cultures was osteoinductive. However, MMN-CM exhibited increased bone formation compared to iDBM and iDBM + rhBMP2. Furthermore, exogenous rhBMP2 alone, at the concentration found in MMN-CM collected from D5 to D10 cultures, failed to induce new bone, indicating that other factors in the CM play a critical role in that osteoinductive microenvironment. MSCs cultured on MMN^TMTi6Al4V surfaces differentiate and produce an increase in local factors, including BMP2, and the CM from these cultures can induce ectopic bone formation compared to control groups, indicating that the increased bone formation arises from the local response by MSCs to a biomimetic, multiscale surface topography.

Antibacterial nanopatterned coatings for dental implants

Dental implants, usually made of titanium, are exposed to hostile oral microflora that facilitate bacterial infections and subsequent inflammation. To mitigate these processes, we coated titanium substrates with block copolymer nanopatterns and investigated the bactericidal effect of these coatings against Gram-positive and Gram-negative bacteria. We found that the bactericidal efficacy of the coatings depends on their morphology and surface chemistry as well as on the bacterial strain: an optimal combination can lead to significant bacterial death for a short time, i.e. 90% for 90 min. Human gingival fibroblasts in contact with the nanopatterned coatings showed similar cell attachment and morphology as on bare Ti. Immunostaining assays showed similar levels of CCR7 and CD206 in macrophages cultured over the nanopatterns and bare Ti, demonstrating adequate properties for tissue integration. The nanopatterns induced a small increase in macrophage aspect ratio, which might indicate early states of M2 polarization, given the absence of CD206.

Effect of Titanium and Zirconia Nanoparticles on Human Gingival Mesenchymal Stromal Cells

Nano- and microparticles are currently being discussed as potential risk factors for peri-implant disease. In the present study, we compared the responses of human gingival mesenchymal stromal cells (hG-MSCs) on titanium and zirconia nanoparticles (<100 nm) in the absence and presence of Porphyromonas gingivalis lipopolysaccharide (LPS). The primary hG-MSCs were treated with titanium and zirconia nanoparticles in concentrations up to 2.000 µg/mL for 24 h, 72 h, and 168 h. Additionally, the cells were treated with different nanoparticles (25−100 µg/mL) in the presence of P. gingivalis LPS for 24 h. The cell proliferation and viability assay and live−dead and focal adhesion stainings were performed, and the expression levels of interleukin (IL)-6, IL-8, and monocyte chemoattractant protein (MCP)-1 were measured. The cell proliferation and viability were inhibited by the titanium (>1000 µg/mL) but not the zirconia nanoparticles, which was accompanied by enhanced apoptosis. Both types of nanoparticles (>25 µg/mL) induced the significant expression of IL-8 in gingival MSCs, and a slightly higher effect was observed for titanium nanoparticles. Both nanoparticles substantially enhanced the P. gingivalis LPS-induced IL-8 production; a higher effect was observed for zirconia nanoparticles. The production of inflammatory mediators by hG-MSCs is affected by the nanoparticles. This effect depends on the nanoparticle material and the presence of inflammatory stimuli.

The Effect of Microcosm Biofilm Decontamination on Surface Topography, Chemistry, and Biocompatibility Dynamics of Implant Titanium Surfaces

Since the inception of dental implants, a steadily increasing prevalence of peri-implantitis has been documented. Irrespective of the treatment protocol applied for the management of peri-implantitis, this biofilm-associated pathology, continues to be a clinical challenge yielding unpredictable and variable levels of resolution, and in some cases resulting in implant loss. This paper investigated the effect of microcosm biofilm in vitro decontamination on surface topography, wettability, chemistry, and biocompatibility, following decontamination protocols applied to previously infected implant titanium (Ti) surfaces, both micro-rough -Sandblasted, Large-grit, Acid-etched (SLA)-and smooth surfaces -Machined (M). Microcosm biofilms were grown on SLA and M Ti discs. These were treated with TiBrushes (TiB), combination of TiB and photodynamic therapy (PDT), combination of TiB and 0.2%CHX/1%NaClO, plus or minus Ultraviolet-C (UV-C) radiation. Surface topography was evaluated by Scanning Electron Microscopy (SEM) and Laser Surface Profilometry. Surface function was analysed through wettability analysis. Surface chemistry evaluation of the discs was performed under SEM/Energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Biocompatibility was tested with the cytocompatibility assay using human osteoblast-like osteosarcoma cell line (MG-63) cells. Elemental analysis of the discs disclosed chemical surface alterations resulting from the different treatment modalities. Titanium, carbon, oxygen, sodium, aluminium, silver, were identified by EDX as the main components of all the discs. Based on the data drawn from this study, we have shown that following the decontamination of Ti surfaces the biomaterial surface chemistry and topography was altered. The type of treatment and Ti surface had a significant effect on cytocompatibility (p = 0.0001). Although, no treatment modality hindered the titanium surface biocompatibility, parameters such as the use of chemical agents and micro-rough surfaces had a higher cytotoxic effect in MG-63 cells. The use of smooth surfaces, and photofunctionalisation of the TiO₂ layer had a beneficial effect on cytocompatibility following decontamination.

Biomimetic Implant Surfaces and Their Role in Biological Integration—A Concise Review

Background: The increased use of dental implants in oral rehabilitation has been followed by the development of new biomaterials as well as improvements in the performance of biomaterials already in use. This triggers the need for appropriate analytical approaches to assess the biological and, ultimately, clinical benefits of these approaches. Aims: To address the role of physical, chemical, mechanical, and biological characteristics in order to determine the critical parameters to improve biological responses and the long-term effectiveness of dental implant surfaces. Data sources and methods: Web of Science, MEDLINE and Lilacs databases were searched for the last 30 years in English, Spanish and Portuguese idioms. Results: Chemical composition, wettability, roughness, and topography of dental implant surfaces have all been linked to biological regulation in cell interactions, osseointegration, bone tissue and peri-implant mucosa preservation. Conclusion: Techniques involving subtractive and additive methods, especially those involving laser treatment or embedding of bioactive nanoparticles, have demonstrated promising results. However, the literature is heterogeneous regarding study design and methodology, which limits comparisons between studies and the definition of the critical determinants of optimal cell response.

Is There a Better Biomaterial for Dental Implants than Titanium?—A Review and Meta-Study Analysis

This article focuses on preclinical studies and reviews the available evidence from the literature on dental implant and abutment materials in the last decade. Specifically, different peri-implantitis materials and how surface modifications may affect the peri-implant soft-tissue seal and subsequently delay or hinder peri-implantitis are examined. This review analyzed more than 30 studies that were Randomized Controlled Trials (RCTs), Controlled Clinical Trials (CCTs), or prospective case series (CS) with at least six months of follow-up. Meta-analyses were performed to make a comparison between different implant materials (titanium vs. zirconia), including impact on bone changes, probing depth, plaque levels, and peri-implant mucosal inflammation, as well as how the properties of the implant material and surface modifications would affect the peri-implant soft-tissue seal and peri-implant health conditions. However, there was no clear evidence regarding whether titanium is better than other implant materials. Clinical evidence suggests no difference between different implant materials in peri-implant bone stability. The metal analysis offered a statistically significant advantage of zirconia implants over titanium regarding developing a favorable response to the alveolar bone.

Intranuclear cell uptake and toxicity of titanium dioxide and zirconia particles as well as bacterial adhesion on dental titanium- and zirconia-implants

OBJECTIVE

Previous studies have shown that particles can be released from dental titanium (Ti)- and zirconia (ZrO₂)-implants. Titanium dioxide (TiO₂)- and ZrO₂-particles were compared regarding their toxicity and intranuclear cell uptake as well as the adhesion of various anaerobic bacteria on Ti- and ZrO₂-implants.

METHODS

Cyto- and genotoxicity of TiO₂-microparticles (TiO₂-MPs) and TiO₂-nanoparticles (TiO₂-NPs) in periodontal ligament (PDL)-hTERT cells were determined with XTT test and DNA damage with comet assay. Particle sizes of TiO₂- and ZrO₂-particles were measured with scanning electron microscope. Intranuclear uptake in PDL-hTERT cells was determined with laser scanning confocal microscopy. Adhesions of relevant anaerobic mouth bacteria Porphyromonas gingivalis, Prevotella intermedia and Aggregatibacter actinomycetemcomitans on Ti- and ZrO₂-implants were investigated by cultivation and counting bacterial colonies.

RESULTS

Particle size measurements revealed that 99% of the TiO₂-NPs had a size below 100 nm and 88% of the TiO₂-MPs sizes were between 50 and 200 nm. Following EC₅₀ values were found for particles (mg/l): 92 (TiO₂-MPs) and 15 (TiO₂-NPs). A significant increase in olive tail moment (OTM) was found for TiO₂-NPs at a concentration of 1/10 EC₅₀. TiO₂- and ZrO₂-NPs had a higher intranuclear cell uptake efficiency, compared to corresponding TiO₂- and ZrO₂-MPs. All investigated particles could be detected in cell nucleus. Adhesion of all investigated bacterial species was significantly higher on Ti-implants, compared to ZrO₂-implants.

CONCLUSION

Ti usually develops an oxide layer (TiO₂). Particles released from Ti-implants should be TiO₂-particles or Ti-particles coated with a TiO₂-layer. Toxicity of released Ti-particles depends on their oxidation state and on their size (NP or MP). Particularly, NPs were more cyto- and genotoxic compared to the corresponding MPs. TiO₂- and ZrO₂-NPs showed a significant increase in the intranuclear cell uptake ratio at higher exposure concentration, compared to lower concentrations and consequently might lead to a higher potential of DNA damage. Adhesion of bacteria to ZrO₂-implants is reduced, compared to Ti-implants. Therefore, ZrO₂-implants might contribute to reduced biological complications (e.g. periimplantitis).

A Clinical and Radiographic Evaluation of Zirconia Dental Implants: 10-Year Follow-Up

PURPOSE

The aim is to evaluate the survival and success rates, as well as the marginal bone loss (MBL) and periodontal indexes, of zirconia implants with 10-year follow-up.

MATERIALS AND METHODS

10 patients were selected and 26 one-piece zirconia implants were used for the rehabilitation of single tooth or partially edentulous ridge. After 10 years, a clinical-radiographic evaluation was performed in order to estimate peri-implant tissue health and marginal bone loss.

RESULTS

The survival and success rates were 100%. The average marginal bone loss from baseline to 120 months after surgery was 0.92 ± 0.97 mm.

CONCLUSION

One-piece zirconia dental implants are characterised by high biocompatibility, low plaque adhesion, and absence of microgap that can be related to the clinical success of these implants.

Surface Treatment and Bioinspired Coating for 3D-Printed Implants

Three-dimensional (3D) printing technology has developed rapidly and demonstrates great potential in biomedical applications. Although 3D printing techniques have good control over the macrostructure of metallic implants, the surface properties have superior control over the tissue response. By focusing on the types of surface treatments, the osseointegration activity of the bone-implant interface is enhanced. Therefore, this review paper aims to discuss the surface functionalities of metallic implants regarding their physical structure, chemical composition, and biological reaction through surface treatment and bioactive coating. The perspective on the current challenges and future directions for development of surface treatment on 3D-printed implants is also presented.

Secondary stability achieved in dental implants with a calcium-coated sandblasted, large-grit, acid-etched (SLA) surface and a chemically modified SLA surface placed without mechanical engagement: A preclinical study

OBJECTIVES

To assess the osseointegration of calcium-coated (CS) and chemically modified, sandblasted, large-grit, acid-etched (MS) dental implants with a lack of primary mechanical stability.

MATERIALS AND METHODS

Eighteen implants in CS and MS groups each were loosely placed in the mandible of six mongrel dogs and allowed to heal for 2, 4 and 8 weeks. Implant stability quotient (ISQ) and implant stability test (IST) values recorded periodically and bone-to-implant contact (BIC) and the number of Haversian canals per 1 mm² measured histologically were statistically analysed (p < .05).

RESULTS

All CS and MS implants placed survived. Compared with immediately after installation, ISQ and IST values in both groups increased significantly to over 76 at 2 weeks (p < .0083) and remained stable thereafter. BIC was significantly greater at 8 weeks (61.3 ± 13.6% in CS group; 57.6 ± 5.9% in MS group) compared to 2 and 4 weeks in both groups (p < .017). There were no significant intergroup differences in ISQ, IST or BIC at different time points. Significantly more Haversian canals were observed in group CS (6.2 ± 1.0/mm² ) compared with group MS at 4 weeks (3.7 ± 1.8 /mm² ; p < .05), while intergroup difference was not significant at 8 weeks.

CONCLUSION

Both CS and MS implants inserted without primary stability obtained osseointegration within 2 weeks, and lamellar bone adjacent to the implants was first observed at 8 weeks. The formation of primary osteons was more active at 4 weeks in group CS than in group MS.

Influence of surface termination of ultrananocrystalline diamond films coated on titanium on response of human osteoblast cells: A proteome study

Successful osseointegration, i.e. the fully functional connection of patient's bone and artificial implant depends on the response of the cells to the direct contact with the surface of the implant. The surface properties of the implant which trigger cell responses leading to its integration into the surrounding bone can be tailored by surface modifications or coating with thin layers. One potential material for such applications is ultrananocrystalline diamond (UNCD). It combines the exceptional mechanical properties of diamond with good biocompatibility and possibility of coating as thin uniform films on different substrates of biological interest. In the current work we firstly deposited UNCD films on titanium-coated substrates and applied oxygen or ammonia plasma to modify their surface properties. The as-grown and modified UNCD exhibited relatively smooth surfaces with topography dominated by rounded features. The modifications induced oxygen- or amino-terminated surfaces with increased hydrophilicity. In addition, the UNCD coatings exhibited very low coefficient of friction when diamond was used as a counterpart. As-grown and modified UNCD samples were applied to study the responses of human osteoblast MG63 cells triggered by surfaces with various terminations assessed by proteomic analysis. The results revealed that the coating of Ti with UNCD as well as the plasma modifications resulting in O- or NH₂-terminated UNCD induced upregulation of proteins specific for cytoskeleton, cell membrane, and extracellular matrix (ECM) involved in the cell-ECM-surface interactions. Proteins from each of these groups, namely, vimentin, cadherin and fibronectin were further studied immunocytochemically and the results confirmed their increased abundance leading to improved cell-to-surface adhesion and cell-to-cell interactions. These findings demonstrate the potential of implant coating with UNCD and its surface modifications for better osseointegration and bone formation.

Surface treatment of 3D printed porous Ti6Al4V implants by ultraviolet photofunctionalization for improved osseointegration

Three-dimensional (3D)-printed porous Ti6Al4V implants play an important role in the reconstruction of bone defects. However, its osseointegration capacity needs to be further improved, and related methods are inadequate, especially lacking customized surface treatment technology. Consequently, we aimed to design an omnidirectional radiator based on ultraviolet (UV) photofunctionalization for the surface treatment of 3D-printed porous Ti6Al4V implants, and studied its osseointegration promotion effects in vitro and in vivo, while elucidating related mechanisms. Following UV treatment, the porous Ti6Al4V scaffolds exhibited significantly improved hydrophilicity, cytocompatibility, and alkaline phosphatase activity, while preserving their original mechanical properties. The increased osteointegration strength was further proven using a rabbit condyle defect model in vivo, in which UV treatment exhibited a high efficiency in the osteointegration enhancement of porous Ti6Al4V scaffolds by increasing bone ingrowth (BI), the bone-implant contact ratio (BICR), and the mineralized/osteoid bone ratio. The advantages of UV treatment for 3D-printed porous Ti6Al4V implants using the omnidirectional radiator in the study were as follows: 1) it can significantly improve the osseointegration capacity of porous titanium implants despite the blocking out of UV rays by the porous structure; 2) it can evenly treat the surface of porous implants while preserving their original topography or other morphological features; and 3) it is an easy-to-operate low-cost process, making it worthy of wide clinical application.

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An omnidirectional radiator based on ultraviolet photofunctionalization was invented..

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The omnidirectional radiator can evenly treat the surface of the porous implants..

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The present method can enhance osteoinetegration of porous Ti6Al4V implants in a convenient way with a low cost.

Tantalum as a Novel Biomaterial for Bone Implant: A Literature Review

Titanium (Ti) has been used in metallic implants since the 1950s due to various biocompatible and mechanical properties. However, due to its high Young’s modulus, it has been modified over the years in order to produce a better biomaterial. Tantalum (Ta) has recently emerged as a new potential biomaterial for bone and dental implants. It has been reported to have better corrosion resistance and osteo-regenerative properties as compared to Ti alloys which are most widely used in the bone-implant industry. Currently, Tantalum cannot be widely used yet due to its limited availability, high melting point, and high-cost production. This review paper discusses various manufacturing methods of Tantalum alloys, including conventional and additive manufacturing and also discusses their drawbacks and shortcomings. Recent research includes surface modification of various metals using Tantalum coatings in order to combine bulk material properties of different materials and the porous surface properties of Tantalum. Design modification also plays a crucial role in controlling bulk properties. The porous design does provide a lower density, wider surface area, and more immense specific strength. In addition to improved mechanical properties, a porous design could also escalate the material's biological and permeability properties. With current advancement in additive manufacturing technology, difficulties in processing Tantalum could be resolved. Therefore, Tantalum should be considered as a serious candidate material for future bone and dental implants.

Benefits and Biosafety of Use of 3D-Printing Technology for Titanium Biomedical Implants: A Pilot Study in the Rabbit Model

BACKGROUND

Titanium has been used in osteosynthesis for decades and its compatibility and safety is unquestioned. Studies have shown that there is release and collection of titanium in the organ systems with little note of toxicity. The gold standard is considered to be titanium osteosynthesis plate produced by milling methods. The use of customized titanium plates produced with 3D printing, specifically direct metal laser sintering, have found increasing use in recent years. It is unknown how much titanium is released in these printed titanium implants, which is known to be potentially porous, depending on the heat settings of the printer. We hypothesize that the amount of titanium released in printed titanium implants may be potentially more or equal compared to the gold standard, which is the implant produced by milling.

METHODS

We studied the biosafety of this technology and its products by measuring serum and organ titanium levels after implantation of 3D-printed versus traditionally fabrication titanium plates and screws in a pilot study using the rabbit model. A total of nine rabbits were used, with three each in the control, milled and printed titanium group. The animals were euthanized after six months. Serum and organs of the reticuloendothelial system were harvested, digested and assayed for titanium levels.

RESULTS

Organ and serum titanium levels were significantly higher in rabbit subjects implanted with titanium implants (milled and printed) compared to the control group. However, there was no significant difference in organ and serum titanium levels of subjects implanted with milled and traditionally fabricated titanium implants.

CONCLUSIONS

The biosafety of use of 3D-printed titanium implants and traditionally fabricated titanium implants are comparable. With this in mind, 3D-printed custom implants can not only replace, but will very possibly surpass traditionally fabricated titanium implants in the mode and extent of use.

Biofilm Formation on the Surface of (Poly)Ether-Ether-Ketone and In Vitro Antimicrobial Efficacy of Photodynamic Therapy on Peri-Implant Mucositis

Poly-ether-ether-ketone (PEEK) is an aesthetically pleasing natural material with good biocompatibility and shock absorption characteristics. The application of PEEK as a dental implant or abutment is expected to reduce the risk of failure and enhance aesthetics. Given that approximately one in 15 patients have allergic reactions to antibiotics, photodynamic therapy (PDT) has been gaining attention as an alternative treatment. Herein, the applicability of PEEK dental implants or abutments was investigated using material analyses, biofilm formation assay, and cell viability tests. The possible use of PDT for peri-implant mucositis was evaluated with the biofilm removal assay. The obtained data were analyzed based on the multivariate analysis of variance, paired t-tests, and the Pearson correlation coefficient (α = 0.05). The results revealed that PEEK was significantly less conducive to the formation of biofilms with S. mutans and A. actinomycetemcomitan (p < 0.001) but exhibited comparable MG-63 (human osteoblast-like) osteoblast cell viability (p > 0.05) to the other materials. PDT had similar antimicrobial efficacy and yielded similar biofilm removal effects to antibiotics. Altogether, these findings suggest that PEEK has attractive features and can serve as an alternative material for dental implants or abutments. In cases where peri-implant mucositis occurs, PDT can be used as an accessible therapeutic approach.

One-Step Liquid Phase Polymerization of HEMA by Atmospheric-Pressure Plasma Discharges for Ti Dental Implants

Dental implants can fail due to various factors, in which bad tissue integration is believed to have a significant role. Specific properties of the implant surface, such as its chemistry and roughness, are of paramount importance to address specific cell responses, such as the adsorption of proteins, as well as the adhesion and differentiation of cells, which are suitable for biomaterial and tissue engineering. In this study, an acrylate-containing coating was produced on titanium surfaces through the atmospheric pressure plasma treatment of a liquid precursor, 2-hydroxyethyl methacrylate. A hydrophilic coating was obtained, showing retention of the monomer chemistry as assessed by FTIR analysis and XPS. Enhanced fibroblast adhesion and decreased Staphylococcus aureus and Escherichia coli adhesion were recorded, showing that this is a suitable method to produce biocompatible coatings with a reduced bacterial adhesion.

Effects of surface roughness of ceria-stabilized zirconia/alumina nanocomposite on the morphology and function of human gingival fibroblasts

We evaluated the biological effects of implant abutments made from ceria-stabilized zirconia/alumina nanocomposite (Ce-TZP/Al₂O₃) with surface roughness variations using human gingival fibroblasts (HGF-1) in the transmucosal region. Two types of titanium (Ti) and Ce-TZP/Al₂O₃ disks with different surface roughness profiles were prepared (Ra0.9 and Ra0.02). Surface properties were evaluated using SEM, EDX, and wettability analysis. Biological parameters including cell adhesion, proliferation and morphology, collagen deposition, and inflammatory cytokine expression were evaluated for each disk. Surface morphology analysis of Ce-TZP/Al₂O₃ and Ti elucidated the uniform linear structures of Ra0.9 and the smooth and flat structures of Ra0.02. Cell morphology showed spindle-shaped and large, circular forms, respectively. Cell adhesion and proliferation and collagen deposition were significantly increased on Ce-TZP/Al₂O₃ Ra0.02 disk compared with the others, with no significant differences in cytokine expression among all the disks. The reduced surface roughness of Ce-TZP/Al₂O₃ was advantageous for promoting biological effects in the transmucosal region.

Systematic investigation of metallosis associated with magnetically controlled growing rod implantation for early-onset scoliosis

AIMS

To investigate metallosis in patients with magnetically controlled growing rods (MCGRs) and characterize the metal particle profile of the tissues surrounding the rod.

METHODS

This was a prospective observational study of patients with early onset scoliosis (EOS) treated with MCGRs and undergoing rod exchange who were consecutively recruited between February 2019 and January 2020. Ten patients were recruited (mean age 12 years (SD 1.3); 2 M:8 F). The configurations of the MCGR were studied to reveal the distraction mechanisms, with crucial rod parts being the distractable piston rod and the magnetically driven rotor inside the barrel of the MCGR. Metal-on-metal contact in the form of ring-like wear marks on the piston was found on the distracted portion of the piston immediately outside the barrel opening (BO) through which the piston rod distracts. Biopsies of paraspinal muscles and control tissue samples were taken over and away from the wear marks, respectively. Spectral analyses of the rod alloy and biopsies were performed to reveal the metal constituents and concentrations. Histological analyses of the biopsies were performed with haematoxylin and eosin staining.

RESULTS

Titanium (Ti), vanadium (V), and neodymium (Nd) concentrations in the biopsies taken near the wear marks were found to be significantly higher than those in the control tissue samples. Significantly increased Nd concentrations were also found in the tissues near the barrel of the MCGR. Chronic inflammation was revealed by the histological studies with fibrosis and macrophage infiltration. Black particles were present within the macrophages in the fibrotic tissues.

CONCLUSION

Ti and V were generated mainly at the BO due to metal-on-metal contact, whereas the Nd from the rotor of the MCGR is likely released from the BO during distraction sessions. Phagocytotic immune cells with black particles inside raise concern regarding the long-term implications of metallosis. Cite this article: Bone Joint J 2020;102-B(10):1375-1383.

A Comprehensive Review on the Corrosion Pathways of Titanium Dental Implants and Their Biological Adverse Effects

The main aim of this work was to perform a comprehensive review of findings reported by previous studies on the corrosion of titanium dental implants and consequent clinical detrimental effects to the patients. Most studies were performed by in vitro electrochemical tests and complemented with microscopic techniques to evaluate the corrosion behavior of the protective passive oxide film layer, namely TiO2. Results revealed that bacterial accumulation, dietary, inflammation, infection, and therapeutic solutions decrease the pH of the oral environment leading to the corrosion of titanium. Some therapeutic products used as mouthwash negatively affect the corrosion behavior of the titanium oxide film and promote changes on the implant surface. In addition, toothpaste and bleaching agents, can amplify the chemical reactivity of titanium since fluor ions interacting with the titanium oxide film. Furthermore, the number of in vivo studies is limited although corrosion signs have been found in retrieved implants. Histological evaluation revealed titanium macro- and micro-scale particles on the peri-implant tissues. As a consequence, progressive damage of the dental implants and the evolution of inflammatory reactions depend on the size, chemical composition, and concentration of submicron- and nanoparticles in the surrounding tissues and internalized by the cells. In fact, the damage of the implant surfaces results in the loss of material that compromises the implant surfaces, implant-abutment connections, and the interaction with soft tissues. The corrosion can be an initial trigger point for the development of biological or mechanical failures in dental implants.

Oral Implants: The Paradigm Shift in Restorative Dentistry

The discovery of the phenomenon "osseointegration," or functional ankylosis, has led to the development of oral implants with high clinical performance. Consequently, the placement of titanium implants has changed the paradigms of restorative dentistry. Implants are used to prevent placing reconstructions anchored on natural teeth when these are vital and intact. Furthermore, implants are suitable to improve subjective chewing function and to replace missing and strategically important abutments. The osseointegration process is characterized by a predictable sequence of healing events that encompass the formation of woven bone, parallel fibers, and lamellar bone and result in fully functional bone that will remodel throughout life. While the osseointegration facilitates the use of implants as prosthetic abutments, it has to be kept in mind that the peri-implant soft tissue may be subject to biological complications. This, in turn, may result in an infectious process that will jeopardize the osseointegration. Consequently, the monitoring of the peri-implant tissues is an important aspect, and early intervention in situations with peri-implant mucositis is mandatory for the prevention of peri-implantitis. Hence, it is evident that oral implants need lifelong maintenance care if their longevity is to be assured.

Implant Soft-Tissue Attachment Using 3D Oral Mucosal Models-A Pilot Study

PURPOSE

The aim of this study was to investigate soft-tissue attachment to different metal, ceramic, and polymer implant surfaces using an inflamed, three-dimensional (3D), tissue-engineered, human oral mucosal model, as well as multiple-endpoint qualitative and quantitative biological approaches.

METHODS

Normal human oral fibroblasts, OKF6/TERT-2 keratinocytes and THP-1 monocytes were cultured, and full-thickness, 3D oral mucosal models were engineered inside tissue culture inserts. Sand-blasted and acid-etched (SLA) and machined (M) titanium-zirconium alloy (TiZr; commercially known as Roxolid; Institut Straumann AG, Switzerland), ceramic (ZrO2), and polyether ether ketone (PEEK) rods (Ø 4 mm × 8 mm) were inserted into the center of tissue-engineered oral mucosa following a Ø 4mm punch biopsy. Inflammation was simulated with addition of the lipopolysaccharide (LPS) of Escherichia coli (E. coli) and tumor necrosis factor (TNF)-alpha to the culture medium. Implant soft-tissue attachment was assessed using histology, an implant pull-test with PrestoBlue assay, and scanning electron microscopy (SEM).

RESULTS

Inflamed, full-thickness, 3D human oral mucosal models with inserted implants were successfully engineered and histologically characterized. The implant pull-test with PrestoBlue assay showed higher viability of the tissue that remained attached to the TiZr-SLA surface compared to the other test groups. This difference was statistically significant (p < 0.05). SEM analysis showed evidence of epithelial cell attachment on different implant surfaces.

CONCLUSIONS

The inflamed, 3D, oral mucosal model has the potential to be used as a suitable in vitro test system for visualization and quantification of implant soft-tissue attachment. The results of our study indicate greater soft tissue attachment to TiZr-SLA compared to TiZr-M, ceramic, and PEEK surfaces.

Antibacterial and Osteogenic Activity of Titania Nanotubes Modified with Electrospray-Deposited Tetracycline Nanoparticles

The nanotubular surface of titanium implants is known to have superior osteogenic activity but is also vulnerable to failure because of induced bacterial attachment and consequent secondary infection. Here, the problem was attempted to be solved by depositing nanosized tetracycline (TC)-loaded particles in poly(lactic-co-glycolic acid) on titania nanotubes (TNTs) using the electrospray deposition method. The antibacterial effect of the newly formed TNT surface was considered using the common pathogen Staphylococcus aureus. Maintenance of the biocompatibility and osteogenic characteristics of TNTs has been tested through cytotoxicity tests and osteogenic gene expression/extra-cellular matrix mineralization, respectively. The results showed that TNTs were successfully formed by anodization, and the characterization of TC deposited on the TNTs was controlled by varying the spraying parameters such as particle size and coating time. The TC nanoparticle-coated TNTs showed antibacterial activity against Staphylococcus aureus and biocompatibility with MC3T3-E1 pre-osteoblasts, while the osteogenic activity of the TNT structure was preserved, as demonstrated by osteocalcin and osteopontin gene expression, as well as Alizarin red staining. Hence, this study concluded that the electrosprayed TC coating of TNTs is a simple and effective method for the formation of bactericidal implants that can maintain osteogenic activity.

Wetting properties of blood lipid fractions on different titanium surfaces

Background

Blood is the first tissue contacting the implant surface and starting the biological interactions to enhance osseointegration and stimulate bone formation with the progenitor cytokines, chemokines, and growth factors. The coagulation cascade initiates the first step of osseointegration between implant and neighboring tissues. The wound healing may be inadequate unless the blood wets the implant surface properly. Wettability is one of the most important features of the implant surface while lipid level constitutes a milestone that may change the energy of blood, which determines its distribution on implant material. Thus, the aim of this study was to evaluate the effect of lipid component of blood as cholesterol and its treatment on their wetting behavior of titanium surfaces.

Methods

Five surface groups were formed including grade 4 titanium-machined, grade 4 titanium-SLA, grade 4 titanium-SLActive, Roxolid-SLA, and Roxolid-SLActive. In healthy, hyperlipidemic, and treatment situations, blood was taken from eight rabbits and dropped to the disc surfaces. Contact angles were measured between the blood samples and disc surfaces.

Results

A significant difference was found between both machined and SLActive surfaces, SLA and SLActive surfaces in the hyperlipidemic period, and only Roxolid-SLA and SLActive surfaces during the treatment period. When evaluated according to time, only grade 4-machined and Grade 4-SLA surfaces showed a significant difference.

Conclusions

Our findings indicated that each period has its own characteristics and showed the importance of cholesterol in blood structure on applicability of implant surfaces.

Antibacterial Properties of Triethoxysilylpropyl Succinic Anhydride Silane (TESPSA) on Titanium Dental Implants

Infections related to dental implants are a common complication that can ultimately lead to implant failure, and thereby carries significant health and economic costs. In order to ward off these infections, this paper explores the immobilization of triethoxysilylpropyl succinic anhydride (TESPSA, TSP) silane onto dental implants, and the interaction of two distinct monospecies biofilms and an oral plaque with the coated titanium samples. To this end, titanium disks from prior machining were first activated by a NaOH treatment and further functionalized with TESPSA silane. A porous sodium titanate surface was observed by scanning electron microscopy and X-ray photoelectron spectroscopy analyses confirmed the presence of TESPSA on the titanium samples (8.4% for Ti-N-TSP). Furthermore, a lactate dehydrogenase assay concluded that TESPSA did not have a negative effect on the viability of human fibroblasts. Importantly, the in vitro effect of modified surfaces against Streptococcus sanguinis, Lactobacillus salivarius and oral plaque were studied using a viable bacterial adhesion assay. A significant reduction was achieved in all cases but, as expected, with different effectiveness against simple mono-species biofilm (ratio dead/live of 0.4) and complete oral biofilm (ratio dead/live of 0.6). Nevertheless, this approach holds a great potential to provide dental implants with antimicrobial properties.

Control of Peri-Implant Mucous Inflammation by Using Chlorhexidine or Ultraviolet C Radiation for Cleaning Healing Abutments. Double-Blind Randomized Clinical Trial

Two-phase implants must be exposed to the external environment after the period of osteointegration has elapsed. For this purpose, a healing abutment is placed passing through the mucosa while forming the emergence profile. The continuous connection and disconnection can lead to an alteration in the tissue maturation, both because of the contact of bacterial plaque and because of the mechanical trauma that involves its manipulation, manifesting with different degrees of erythema or bleeding. To assess whether this epithelium disruption can be counteracted, a blinded study design was developed on 150 unitary implant patients divided into three groups (n = 50), applying chlorhexidine (group 1), ultraviolet C (UV-C) at a wavelength of 254 nm (group 2)and no treatment as a control group (group 3), during each of the disconnections and connections during the prosthodontic treatment (1 time per week for four weeks). All groups showed a better epithelium aspect at the end of the evaluation. Although there were no statistically significant differences in the degree of inflammation, the UV-C treated group had the lowest plaque accumulation, and the highest was for the chlorhexidine-treated group.

Developing Nanostructured Ti Alloys for Innovative Implantable Medical Devices

Recent years have witnessed much progress in medical device manufacturing and the needs of the medical industry urges modern nanomaterials science to develop novel approaches for improving the properties of existing biomaterials. One of the ways to enhance the material properties is their nanostructuring by using severe plastic deformation (SPD) techniques. For medical devices, such properties include increased strength and fatigue life, and this determines nanostructured Ti and Ti alloys to be an excellent choice for the engineering of implants with improved design for orthopedics and dentistry. Various reported studies conducted in this field enable the fabrication of medical devices with enhanced functionality. This paper reviews recent development in the field of nanostructured Ti-based materials and provides examples of the use of ultra-fine grained Ti alloys in medicine.

The Affinity of Human Fetal Osteoblast to Laser-Modified Titanium Implant Fixtures

Introduction:

Implant surface modification methods have recently involved laser treatment to achieve the desired implant surface characteristics. Meanwhile, surface modification could potentially introduce foreign elements to the implant surface during the manufacturing process.

Objectives:

The study aimed to investigate the surface chemistry and topography of commercially available laser-modified titanium implants, together with evaluating the cell morphology and cell adhesion of human fetal osteoblast (hFOB) seeded onto the same implants.

Method:

Six (6) samples of commercially available laser-modified titanium implants were investigated. These implants were manufactured by two different companies. Three (3) implants were made from commercially pure grade 4 Titanium (Brand X); and three were made from grade 5 Ti6Al4V (Brand Y). The surface topography of these implants was analyzed by scanning electron microscope (SEM) and the surface chemistry was evaluated with electron dispersive x-ray spectroscopy(EDS). Human fetal osteoblasts were seeded onto the implant fixtures to investigate the biocompatibility and adhesion.

Results & Discussion:

Brand X displayed dark areas under SEM while it was rarely found on brand Y. These dark areas were consistent with their organic matter. The hFOB cell experiments revealed cell adhesion with filopodia on Brand X samples which is consistent with cell maturation. The cells on Brand Y were morphologically round and lacked projections, one sample was devoid of any noticeable cells under SEM. Cell adhesion was observed early at 48 hrs in laser-irradiated titanium fixtures from both the brands.

Conclusion:

The presence of organic impurities in Brand X should not be overlooked because disruption of the osseointegration process may occur due to the rejection of the biomaterial in an in-vivo model. Nevertheless, there was insufficient evidence to link implant failure directly with carbon contaminated implant surfaces. Further studies to determine the toxicity of Vanadium from Ti6Al4V in an in-vivo environment should indicate the reason for different cell maturation.

Crestal bone response to loaded zirconia and titanium implants: a radiographic and histometric analysis in canines

OBJECTIVES

To evaluate the crestal bone response to a two-piece zirconia implant compared with a control titanium implant using periapical radiographs (PAs) and histometry.

MATERIALS AND METHODS

Thirty zirconia and 30 titanium implants were placed in healed posterior mandibles of five canines. Full-ceramic single-tooth restorations were cemented after 6 weeks of healing. Three observers measured the distance between the implant shoulder and the crestal bone (DIB) at placement, loading, and harvesting after 4 or 16 weeks in function. The influence of implant material and loading time on DIB as well as the inter-observer agreement were analyzed. Additionally, histometric distance between implant shoulder and most coronal bone-to-implant contact (IS-cBIC) was compared with DIB.

RESULTS

Mean DIB values increased between 4 and 16 weeks of loading for both zirconia (from 1.66 to 2.25 mm; P < 0.0001) and titanium (from 1.81 to 1.95 mm; P = 0.06). Zirconia yielded mean IS-cBIC values of 2.18 mm and 2.48 mm (P < 0.001) and titanium 2.23 mm and 2.34 mm (P = 0.27) after 4 and 16 weeks, respectively. The raters reached an excellent intraclass correlation coefficient. PAs underestimated the bone loss on average by 0.39 mm.

CONCLUSIONS

Zirconia implants showed a greater increase of DIB during early healing and function than titanium.

CLINICAL RELEVANCE

Crestal peri-implant tissue dimensions may show more pronounced changes around two-piece zirconia implants during early healing. PAs may underestimate peri-implant bone loss.

Osteogenesis regulation of mesenchymal stem cells via autophagy induced by silica–titanium composite surfaces with different mechanical moduli

The high surface elastic modulus of the titanium (Ti) implant is one of the critical factors causing poor osteointegration between the implant surface and surrounding bone tissue.

The Effect of Hot Working on the Mechanical Properties of High Strength Biomedical Ti-Nb-Ta-Zr-O Alloy

Beta titanium alloy Ti-35Nb-6Ta-7Zr-0.7O (wt%) was developed as a material intended for the manufacturing of a stem of a hip joint replacement. This alloy contains only biocompatible elements and possesses a very high yield strength already in the cast condition (900 MPa). However, the porosity, large grain size and chemical inhomogeneity reduce the fatigue performance below the limits required for utilization in the desired application. Two methods of hot working, die forging and hot rolling, were used for processing of this alloy. Microstructural evolution, tensile properties and fatigue performance of the hot worked material were investigated and compared to the cast material. Microstructural observations revealed that porosity is removed in all hot-worked conditions and the grain size is significantly reduced when the area reduction exceeds 70%. Static tensile properties were improved by both processing methods and ultimate tensile strength (UTS) of 1200 MPa was achieved. Fatigue results were more reproducible in the hot rolled material due to better microstructural homogeneity, but forging leads to an improved fatigue performance. Fatigue limit of 400 MPa was achieved in the die-forged condition after 70% of area reduction and in the hot rolled condition after 86% of area reduction.

Accentuated osseointegration in osteogenic nanofibrous coated titanium implants

Anchoring of endosseous implant through osseointegration continues to be an important clinical need. Here, we describe the development of superior endosseous implant demonstrating enhance osseointegration, achieved through surface modification via coating of osteogenic nanofibres. The randomized bio-composite osteogenic nanofibres incorporating polycaprolactone, gelatin, hydroxyapatite, dexamethasone, beta-glycerophosphate and ascorbic acid were electrospun on titanium implants mimicking bone extracellular matrix and subsequently induced osteogenesis by targeting undifferentiated mesenchymal stem cells present in the peri-implant niche to regenerate osseous tissue. In proof-of-concept experiment on rabbit study models (n = 6), micro-computed tomography (Micro-CT), histomorphometric analysis and biomechanical testing in relation to our novel osteogenic nanofibrous coated implants showed improved results when compared to uncoated controls. Further, no pathological changes were detected during gross examination and necropsy on peri-implant osseous tissues regenerated in response to such coated implants. The findings of the present study confirm that osteogenic nanofibrous coating significantly increases the magnitude of osteogenesis in the peri-implant zone and favours the dynamics of osseointegration.

Mechanical aspects of dental implants and osseointegration: A narrative review

With the need of rapid healing and long-term stability of dental implants, the existing Ti-based implant materials do not meet completely the current expectation of patients. Low elastic modulus Ti-alloys have shown superior biocompatibility and can achieve comparable or even faster bone formation in vivo at the interface of bone and the implant. Porous structured Ti alloys have shown to allow rapid bone ingrowth through their open structure and to achieve anchorage with bone tissue by increasing the bone-implant interface area. In addition to the mechanical properties of implant materials, the design of the implant body can be used to optimize load transfer and affect the ultimate results of osseointegration. The aim of this narrative review is to define the mechanical properties of dental implants, summarize the relationship between implant stability and osseointegration, discuss the effect of metallic implant mechanical properties (e.g. stiffness and porosity) on the bone response based on existing in vitro and in vivo information, and analyze load transfer through mechanical properties of the implant body. This narrative review concluded that although several studies have presented the advantages of low elastic modulus or high porosity alloys and their effect on osseointegration, further in vivo studies, especially long-term observational studies are needed to justify these novel materials as a replacement for current Ti-based implant materials.

Mechanical Properties of Ti-15Mo Alloy Prepared by Cryogenic Milling and Spark Plasma Sintering

Metastable β-Ti alloy Ti-15Mo was prepared by cryogenic ball milling in a slurry of liquid argon. Material remained ductile even at low temperatures, which suppressed particle refinement, but promoted intensive plastic deformation of individual powder particles. Repetitive deformation of powder particles is similar to the multidirectional rolling and resembles bulk severe plastic deformation (SPD) methods. Initial and milled powders were compacted by spark plasma sintering. Sintered milled powder exhibited a refined microstructure with small β-grains and submicrometer sized α-phase precipitates. The microhardness and the yield tensile strength of the milled powder after sintering at 850 °C attained 350 HV and 1200 MPa, respectively. Low ductility of the material can be attributed to high oxygen content originating from the cryogenic milling. This pioneering work shows that cryogenic milling followed by spark plasma sintering is able to produce two-phase β-Ti alloys with refined microstructure and very high strength levels.

Effect of the High-Pressure Torsion (HPT) and Subsequent Isothermal Annealing on the Phase Transformation in Biomedical Ti15Mo Alloy

Ti15Mo metastable beta Ti alloy was solution treated and subsequently deformed by high-pressure torsion (HPT). HPT-deformed and benchmark non-deformed solution-treated materials were annealed at 400 °C and 500 °C in order to investigate the effect of UFG microstructure on the α-phase precipitation. Phase evolution was examined using laboratory X-ray diffraction (XRD) and by high-energy synchrotron X-ray diffraction (HEXRD), which provided more accurate measurements. Microstructure was observed by scanning electron microscopy (SEM) and microhardness was measured for all conditions. HPT deformation was found to significantly enhance the α phase precipitation due the introduction of lattice defects such as dislocations or grain boundaries, which act as preferential nucleation sites. Moreover, in HPT-deformed material, α precipitates are small and equiaxed, contrary to the α lamellae in the non-deformed material. ω phase formation is suppressed due to massive α precipitation and consequent element partitioning. Despite that, HPT-deformed material after ageing exhibits the high microhardness exceeding 450 HV.

Biomechanical analysis of the osseointegration of porous tantalum implants

STATEMENT OF PROBLEM

Although implants containing porous tantalum undergo osseointegration, whether this material significantly alters new bone formation and improves implant stability during healing in comparison to titanium is unclear.

PURPOSE

The purpose of this in vivo study was to determine the influence of the inclusion of porous tantalum into a dental implant on the biomechanical properties of the bone-implant interface and peri-implant bone which may contribute to secondary implant stability.

MATERIAL AND METHODS

Threaded titanium implants with a porous tantalum midsection (Trabecular Metal Dental Implant; Zimmer Biomet) or without (Tapered Screw-Vent; Zimmer Biomet) were placed in rabbit tibiae and allowed to heal for 4, 8, or 12 weeks. The implants were evaluated by resonance frequency analysis and removed with surrounding bone for nanoindentation testing. Two-way ANOVA was used to determine the impact of implant type, bone region, and time on the outcomes implant stability quotient (ISQ), hardness, and elastic modulus (α=.05).

RESULTS

Resonance frequency analysis found no significant difference in ISQ values between implant types at 4, 8, or 12 weeks, and ISQ values did not increase for either implant over time. Nanoindentation showed no significant differences in hardness or elastic modulus in newly formed bone adjacent to either implant type at any time point.

CONCLUSIONS

The stiffness of the bone-implant interface was similar for threaded titanium implants with or without porous tantalum when placed in the rabbit tibia and allowed to heal for at least 4 weeks. The new peri-implant bone adjacent to dental implants containing porous tantalum showed no difference in nanomechanical properties to the new bone around implants comprised completely of threaded titanium at all healing time points.

Electrochemical evaluation of the hydrogen peroxide- and fluoride-induced corrosive property and its recovery on the titanium surface

PURPOSE

This study aimed to elucidate the effects of hydrogen peroxide (H₂O₂) and sodium fluoride (NaF) on titanium surfaces under conditions mimicking those encountered during dental treatment.

METHODS

Titanium samples were immersed in artificial saliva (AS), 1M H₂O₂, 1M H₂O₂ with catalase, 1000ppmF NaF, 1M H₂O₂ with 1000ppmF NaF, or 9000ppmF NaF (9000ppmF NaF: pH 5.3, other solutions: pH 6.5) for 3min. The electrochemical properties of the titanium samples were analyzed before and after the immersion procedures using a potentiostat. The amounts of titanium eluted into each solution were measured using inductively coupled plasma mass spectrometry. The post-immersion color changes (ΔE*ab) and gloss values of the titanium samples were determined using spectrophotometry. Moreover, the solution-treated titanium samples were subsequently immersed in AS and analyzed electrochemically at 1, 2, 3, 4, 6, 8, and 24h.

RESULTS

The immersion of titanium in any of the solutions except 1000ppmF NaF caused significant increases in corrosive and passive currents and significant reductions in polarization resistance. No titanium elution or color changes were observed, except when 9000ppmF NaF was used. After immersion in AS, the electrochemical properties of all of the titanium samples, except the 9000ppmF NaF-treated samples, recovered within 24h.

CONCLUSIONS

One M H₂O₂ and 1000ppmF NaF can be used alone or in combination in the clinical setting without causing significant titanium corrosion because the corrosive properties they induce is reversible. However, highly concentrated acidic fluorides can cause irreversible corrosion.

Improving the surface energy of titanium implants by the creation of hierarchical textures on the surface via three-dimensional elliptical vibration turning for enhanced osseointegration

An increase in bone-implant contact and an increase in surface hydrophilicity are the two important factors involved in improving osseointegration. Therefore, three-dimensional elliptical vibration turning method is applied to increase the hydrophilicity of titanium surface by the generation of hierarchical nano- and micro-textures. That being the case, face turning process at different cutting conditions is carried out in this research. Surface roughness and the contact angle of water drops with machined surfaces were selected to be measured for the analysis of surface hydrophilicity. The results show that an additional surface area can be achieved by the generation of micro- or nano-textures, resulting in a lower contact angle. Furthermore, intermittent movement of cutting tool in vibration cutting causes the process to be more stable, achieving the desired range of surface roughness.

Effect of cobalt ions on the interaction between macrophages and titanium

Inflammation and bone reduction around dental implants are described as peri‐implantitis and can be caused by an inflammatory response against bacterial products and toxins. Titanium (Ti) forms aggregates with serum proteins, which activate and cause release of the cytokine interleukin (IL‐1β) from human macrophages. It was hypothesized that cobalt (Co) ions can interact in the formation of pro‐inflammatory aggregates, formed by titanium. To test this hypothesis, we differentiated THP‐1 cells into macrophages and exposed them to Ti ions alone or in combination with Co ions to investigate if IL‐1β release and cytotoxicity were affected. We also investigated aggregate formation, cell uptake and human biopsies with inductively coupled plasma atomic emission spectroscopy and electron microscopy. Co at a concentration of 100 µM neutralized the IL‐1β release from human macrophages and affected the aggregate formation. The aggregates formed by Ti could be detected in the cytosol of macrophages. In the presence of Co, the Ti‐induced aggregates were located in the cytosol of the cultured macrophages, but outside the lysosomal structures. It is concluded that Co can neutralize the Ti‐induced activation and release of active IL‐1β from human macrophages in vitro. Also, serum proteins are needed for the formation of metal‐protein aggregates in cell medium. Furthermore, the structures of the aggregates as well as the localisation after cellular uptake differ if Co is present in a Ti solution. Phagocytized aggregates with a similar appearance seen in vitro with Ti present, were also visible in a sample from human peri‐implant tissue. © 2018 The Authors Journal of Biomedical Materials Research Part A Published by Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A:2518–2530, 2018.

Osteoclastogenesis Behavior of Zirconia for Dental Implant

Zirconia is worth studying as an alternative to dental titanium implants to overcome the disadvantages of titanium. This study investigated the surface characteristics of the zirconia implant material and osteoclastogenesis responses on the surface compared with titanium. Yttrium oxide-stabilized 5% tetragonal zirconia polycrystalline specimens were manufactured, and osteoclast-precursor cells were cultured and differentiated into osteoclasts on the specimens. Surface shape, roughness, and chemical composition were evaluated. After culturing, cell morphologies and differentiation capacity were analyzed using tartrate-resistant acid phosphatase activity (TRACP). mRNA of two critical transcription factors, nuclear factor of activated T-cells 1 (NFATc1) and c-Fos were measured, and protein levels of NFATc1 and c-Fos were investigated. The zirconia specimens had rhomboid-like shapes with smooth surfaces and exhibited no difference in surface roughness compared to the titanium specimens. Morphologies of differentiated osteoclasts on both materials were similar. TRACP activity on the zirconia showed comparable results to that on the titanium. The mRNA value of NFATc1 on the zirconia was higher than that on the titanium at day four. The protein level of c-Fos was expressed thicker on the zirconia when compared to the titanium at day two. The results of this study suggest that zirconia material provides adequate osteoclastogenesis behaviors for dental implant use.

Bioactive TiNbSn alloy prepared by anodization in sulfuric acid electrolytes

The bioactivity of anodized near-β TiNbSn alloy with low Young's modulus prepared in sulfuric acid electrolytes was examined to explore the osseointegration mechanism with a focus on the role of anodic oxide. Hydroxyapatite (HA) precipitated on the surface of anodic oxide following immersion in Hank's solution, and precipitation accelerated with increase in the sulfuric acid concentration of the electrolyte. HA is formed on the surface of as-anodized oxide without subsequent annealing or hot water (HW) treatment. This outcome differs from that of a previous study using anodized TiNbSn alloy prepared in acetic acid electrolytes requiring for subsequent HW treatment. It was found that the oxide anodized in sulfuric acid electrolyte contains a large amount of internal pores and is highly crystallized thick TiO₂, whereas the same prepared in the acetic acid electrolyte is low crystalline thin TiO₂ containing a small amount of pores. The present anodized TiNbSn alloy is preferred for maintaining the low Young's modulus of the alloy and eliminating the subsequent treatment to increase the Young's modulus. A model to rationalize the bioactivity of the present anodic oxide is proposed based on the series of studies. It is concluded that the sulfuric acid electrolyte is favorable for both HA formation and low Young's modulus, and the bioactivity is attributed to the anodic TiO₂ that facilitates incorporation of bone ingredients.

The chemical surface evaluation of black and white porous titanium granules and different commercial dental implants with energy-dispersive x-ray spectroscopy analysis

BACKGROUND

The chemical surface structure of the porous titanium grafts has not been found to study in the literature on the similarity of chemical surfaces of different commercial dental implants.

PURPOSE

The purpose of this study is to investigate the chemical composition and surface energies of white (WPTG) and black porous titanium granules (PTG) by energy dispersive x-ray spectrometry (EDX) analysis to compare with different commercial dental implant surface.

MATERIALS AND METHODS

The surface chemical compositions of six commercially available dental implants with different surface structures, PTG and WPTG were examined by EDX analysis. Surface analyzes were performed on the apical, middle, and coronal parts of each implant and on the top, flank, and valley regions on each side. Surface analyzes of dental implants were evaluated at ×200 and ×2000 magnifications. The EDX evaluation of PTG grafts were evaluated at ×250, ×2000, ×5000, and ×50 000 magnifications.

RESULTS

PTG grafts showed elements of Na (8.88 ± 9.98%), Cl (2.44 ± 1.96%), and Al (0.99 ± 0.37%) as well as Ti (90.06 ± 11.34%) molecule at ×5000 magnification. In WPTG, Ti (%34.55 ± 6.41%) and O (%65.44 ± 6.42%) molecules were detected.

CONCLUSIONS

It has been found that PTG surface was not made of pure titanium, it has different chemical molecules at larger magnifications. Cell culture and experimental studies are needed to establish a relationship between the different commercial implants and the surface structure of the titanium granules.

Effects of ultraviolet treatment and alendronate immersion on osteoblast-like cells and human gingival fibroblasts cultured on titanium surfaces

In this study, we evaluated the effects of ultraviolet (UV) treatment and alendronate (ALN) immersion on the proliferation and differentiation of MG-63 osteoblast-like cells and human gingival fibroblasts (HGFs) cultured on titanium surfaces. MG-63 cells were used for sandblasted, large grit, and acid-etched (SLA) titanium surfaces, and HGFs were used for machined (MA) titanium surfaces. SLA and MA specimens were subdivided into four groups (n = 12) according to the combination of surface treatments (UV treatment and/or ALN immersion) applied. After culturing MG-63 cells and HGFs on titanium discs, cellular morphology, proliferation, and differentiation were evaluated. The results revealed that UV treatment of titanium surfaces did not alter the proliferation of MG-63 cells; however, HGF differentiation and adhesion were increased in response to UV treatment. In contrast, ALN immersion of titanium discs reduced MG-63 cell proliferation and changed HGFs into a more atrophic form. Simultaneous application of UV treatment and ALN immersion induced greater differentiation of MG-63 cells. Within the limitations of this cellular level study, simultaneous application of UV treatment and ALN immersion of titanium surfaces was shown to improve the osseointegration of titanium implants; in addition, UV treatment may be used to enhance mucosal sealing of titanium abutments.

Three-Dimensional Finite Element Analysis of Stress Distribution in Zirconia and Titanium Dental Implants

Zirconia has been presented as an alternative biomaterial to titanium, commercially presented as a single-body implant and/or as an abutment, demonstrating clinically biocompatible favorable results in white and rose esthetics. However, the number of long-term in vivo studies and mechanical tests evaluating the response of stress distribution compared with titanium implants is still limited. The aim of the study was to compare the principal peak stresses in the peri-implant bone around titanium and zirconia implants using the finite element method. Four groups of 3-dimensional models were constructed for the tests: G1, external hexagon titanium implant with a zirconia abutment; G2, zirconia implant with a zirconia abutment; G3, single-body titanium implant; and G4, single-body zirconia implant. Axial and oblique loads of 100 N at 45° were simulated in the prosthetic crown. The bone results showed that the peak stresses decreased by 12% in zirconia implants with 2 parts for axial load and 30% for the oblique load. In single-body implants, the peak stresses decreased 12% in the axial load and 34% in the oblique load when a zirconia implant was used compared with a titanium implant. Although the stress values in megapascals are similar, it can be concluded that the zirconia implants decrease the stress peaks at the peri-implant bone area around the implant platform when compared with titanium implants.

Tuning Nanopore Diameter of Titanium Surfaces to Improve Human Gingival Fibroblast Response

The aim of this study was to determine the optimal nanopore diameter of titanium nanostructured surfaces to improve human gingival fibroblast (hGF) response, with the purpose of promoting gingiva integration to dental implant abutments. Two TiO₂ nanoporous groups with different diameters (NP-S ~48 nm and NP-B ~74 nm) were grown on Ti foils using an organic electrolyte containing fluoride by electrochemical oxidation, varying the applied voltage and the interelectrode spacing. The surfaces were characterized by scanning electron microscope (SEM), atomic force microscopy (AFM), and contact angle. The hGF were cultured onto the different surfaces, and metabolic activity, cytotoxicity, cell adhesion, and gene expression were analyzed. Bigger porous diameters (NP-B) were obtained by increasing the voltage used during anodization. To obtain the smallest diameter (NP-S), apart from lowering the voltage, a lower interelectrode spacing was needed. The greatest surface area and number of peaks was found for NP-B, despite these samples not being the roughest as defined by Ra. NP-B had a better cellular response compared to NP-S. However, these effects had a significant dependence on the cell donor. In conclusion, nanoporous groups with a diameter in the range of 74 nm induce a better hGF response, which may be beneficial for an effective soft tissue integration around the implant.