Cytocompatibility of medical biomaterials containing nickel by osteoblasts: a systematic literature review

Combined Use of Chitosan and Olfactory Mucosa Mesenchymal Stem/Stromal Cells to Promote Peripheral Nerve Regeneration In Vivo

Peripheral nerve injury remains a clinical challenge with severe physiological and functional consequences. Despite the existence of multiple possible therapeutic approaches, until now, there is no consensus regarding the advantages of each option or the best methodology in promoting nerve regeneration. Regenerative medicine is a promise to overcome this medical limitation, and in this work, chitosan nerve guide conduits and olfactory mucosa mesenchymal stem/stromal cells were applied in different therapeutic combinations to promote regeneration in sciatic nerves after neurotmesis injury. Over 20 weeks, the intervened animals were subjected to a regular functional assessment (determination of motor performance, nociception, and sciatic indexes), and after this period, they were evaluated kinematically and the sciatic nerves and cranial tibial muscles were evaluated stereologically and histomorphometrically, respectively. The results obtained allowed confirming the beneficial effects of using these therapeutic approaches. The use of chitosan NGCs and cells resulted in better motor performance, better sciatic indexes, and lower gait dysfunction after 20 weeks. The use of only NGGs demonstrated better nociceptive recoveries. The stereological evaluation of the sciatic nerve revealed identical values in the different parameters for all therapeutic groups. In the muscle histomorphometric evaluation, the groups treated with NGCs and cells showed results close to those of the group that received traditional sutures, the one with the best final values. The therapeutic combinations studied show promising outcomes and should be the target of new future works to overcome some irregularities found in the results and establish the combination of nerve guidance conduits and olfactory mucosa mesenchymal stem/stromal cells as viable options in the treatment of peripheral nerves after injury.

Nanoparticle-based model of anti-inflammatory drug releasing LbL coatings for uncemented prosthesis aseptic loosening prevention

Introduction

The only treatment for aseptic loosening is the replacement of the prosthesis through revision surgery. A preventive approach, achieved through anti-inflammatory drugs released from the device, has shown to be a viable strategy; however, the performance of these devices is not yet satisfactory thus further improvements are necessary.

Methods

We used titanium nanoparticles as a model for implant surfaces and developed a coating containing dexamethasone (DEX) using layer-by-layer deposition.

Results

The amount of deposited drug depended on the number of layers and the release was sustained for months. The efficiency of the released DEX in reducing inflammation markers (tumor necrosis factor alpha and IL-6) produced by human monocytes and macrophages was similar to the pure drug at the same concentration without negative impacts on the viability and morphology of these cells.

Conclusion

These coatings were not inferior to medical grade titanium (the standard material used in uncemented devices) regarding their ability to sustain osteoblasts and fibroblasts growth.

Salivary Nickel and Chromium Levels in Orthodontic Patients with and Without Periodontitis: a Preliminary Historical Cohort Study

Many periodontal patients may need orthodontic treatment. Alterations in oral environment particularly the reduction of pH in periodontal patients could affect metal ion release from orthodontic appliances. However, there is no study on metal ion release in periodontal patients. The aim of this preliminary study was to comparatively evaluate, for the first time, salivary levels of nickel and chromium in periodontal patients (versus healthy controls) under orthodontic treatment for 2 months. In this in vivo study, 40 subjects were evaluated. Patient selection and standardization of orthodontic treatment protocols were prospectively designed and performed. Two groups of n = 20 each (control: healthy orthodontic patients, cohort: orthodontic patients with periodontitis) underwent similar protocols of fixed orthodontic treatment for 2 months. After 2 months, salivary nickel and chromium concentrations of the case and cohort groups were measured using inductively coupled plasma mass spectrometry (ICP-MS). The values were compared between the two groups using t test. There were 10 men and 10 women in each group. The mean age of patients was 34.6 ± 3.6 years old. The salivary level of nickel was 338.2 ± 235.5 ng/ml and 182.8 ± 116.5 ng/ml in the cohort and control groups, respectively (P = 0.0118). The salivary level of chromium was 7.4 ± 3.15 ng/ml in the cohort and 6.35 ± 2.39 ng/ml in the control group (P = 0.2214). Salivary level of nickel might be considerably higher in periodontal patients undergoing 2 months of orthodontic treatment compared to orthodontic patients with healthy gingivae.

Effects of Restoring the Primary Dentition with Stainless-Steel Crowns on Children's Salivary Nickel and Chromium Levels, and the Associations with Saliva pH: a Preliminary Before-After Clinical Trial

Nickel and chromium existing in stainless-steel crowns (SSCs, used in pediatric dentistry) might be cytotoxic and allergenic. However, no in vivo studies have examined their salivary levels in children using SSCs, or in young children without SSCs. Also, the effect of acidity on metal ion release has not yet been evaluated in any previous in vivo studies in the whole literature. Therefore, this preliminary before-after clinical trial was conducted. Salivary nickel/chromium levels of 30 children before and after 2 months of placement of SSCs were measured using atomic absorption spectrophotometry. Salivary pH was measured with a digital pH meter. The effects of treatment, pH, number of SSCs, gender, and age on salivary ions were analyzed statistically (α = 0.05, β = 0.15). Salivary nickel concentrations increased from 4.9010 ± 4.7390 to 5.6320 ± 4.7210 μg/L (P = 0.000, paired t test). Chromium increased from 0.3273 ± 0.5214 to 0.4199 ± 0.6404 μg/L (P = 0.016). Saliva pH increased from 6.81 ± 0.52 to 7.04 ± 0.47 (P = 0.000). Ion levels were not correlated with pH (P > 0.14), except chromium in the follow-up (rho = - 0.435, P = 0.016). Nickel increase (but not chromium increase) was correlated with pH increase (rho = 0.367, P = 0.046). Age was only correlated with baseline chromium (rho = 0.373, P = 0.042). Being male was associated with baseline/follow-up nickel levels (P ≤ 0.030). SSC number was not correlated with ions or pH (P > 0.36). It was shown for the first time that SSCs might increase salivary nickel and chromium concentrations and reduce saliva acidity. Nickel increase might be in line with pH elevation. The raised pH might be associated with reduced chromium release. Boys might have higher nickel levels than might girls, with or without SSCs.

The Spatiotemporal Control of Osteoblast Cell Growth, Behavior, and Function Dictated by Nanostructured Stainless Steel Artificial Microenvironments

The successful application of a nanostructured biomaterial as an implant is strongly determined by the nanotopography size triggering the ideal cell response. Here, nanoporous topography on 304L stainless steel substrates was engineered to identify the nanotopography size causing a transition in the cellular characteristics, and accordingly, the design of nanostructured stainless steel surface as orthopedic implants is proposed. A variety of nanopore diameters ranging from 100 to 220 nm were fabricated by one-step electrolysis process and collectively referred to as artificial microenvironments. Control over the nanopore diameter was achieved by varying bias voltage. MG63 osteoblasts were cultured on the nanoporous surfaces for different days. Immunofluorescence (IF) and scanning electron microscopy (SEM) were performed to compare the modulation in cell morphologies and characteristics. Osteoblasts displayed differential growth parameters and distinct transition in cell behavior after nanopore reached a certain diameter. Nanopores with 100-nm diameter promoted cell growth, focal adhesions, cell area, viability, vinculin-stained area, calcium mineralization, and alkaline phosphatase activity. The ability of these nanoporous substrates to differentially modulate the cell behavior and assist in identifying the transition step will be beneficial to biomedical engineers to develop superior implant geometries, triggering an ideal cell response at the cell-nanotopography interface.

Employing the cyclophosphate to accelerate the degradation of nano-hydroxyapatite/poly(amino acid) (n-HA/PAA) composite materials

Owing to the good degradability and biocompatibility of polyphosphoesters (PPEs), the aim of the current study was to investigate a novel degradable composite of nano-hydroxyapatite/poly(amino acid) (n-HA/PAA) with cyclophosphate (CPE) via in situ melting polymerization to improve the degradation of n-HA/PAA. The structure of each composite was characterized via Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The degradation properties were studied in terms of the weight loss and pH in a phosphate-buffered saline (PBS) solution, while the surface morphology was examined using a scanning electron microscope-energy dispersive spectrometer (SEM-EDS) after soaking the surface in simulated body fluid (SBF). The cell proliferation, cell adhesion, and alkaline phosphatase (ALP) activity were used for the analysis of cytocompatibility. The weight loss results showed that the n-HA/PAA composite was 9.98 wt%, weighed after soaking in the PBS solution for 12 weeks, whereas the nano-hydroxyapatite/polyphosphoester-amino acid (n-HA/PPE-AA) composite was 46.94 wt%. The pH of the composites was in a suitable range between 6.64 to 7.06 and finally stabilized at 7.39. The SEM and EDS results revealed the formation of an apatite-like layer on the surface of the n-HA/PPE-AA composites after soaking in SBF for one week. The cell counting Kit 8 (CCK-8) assay of the cell culture in the leaching liquid of the n-HA/PPE-AA composites exhibited non-cytotoxicity and high-proliferation, and the cell adhesion showed the well spreading and normal phenotype extension of the cells on the n-HA/PPE-AA composites surface. Concurrently, the co-culture results of the composites and cells confirmed that the n-HA/PPE-AA composites exhibited a higher ALP activity. In summary, the results demonstrated that the n-HA/PPE-AA composites had a controllable degradation property, good bioactivity, and cytocompatibility.

Effects of fixed orthodontic treatment on nickel and chromium levels in gingival crevicular fluid as a novel systemic biomarker of trace elements: A longitudinal study

INTRODUCTION

Nickel and chromium might induce hypersensitivity. Therefore, they are of interest to orthodontists. Gingival crevicular fluid (GCF) is highly relevant to orthodontic treatments and might reflect systemic changes associated with the inflammatory response induced by orthodontic forces. Therefore, it might also be used to show metal ion changes. Nevertheless, baseline metal levels of GCF are unknown, and the effect of orthodontic treatment on GCF metal levels has not been investigated. The aim of this study was to assess the levels of nickel and chromium in GCF.

METHODS

Based on a pilot study, the sample size was predetermined as 24 × 3 measurements to obtain test powers above 90%. Nickel and chromium concentrations were measured before treatment and 1 month and 6 months later in 12 female and 12 male patients who had fixed orthodontic appliances using atomic absorption spectrophotometry. The gingival index was also evaluated in each session. The effects of treatment on GCF ions were analyzed using repeated-measures analysis of variance and Friedman tests (α = 0.05, β ≤0.01).

RESULTS

The gingival index worsened over time (chi-square test, P <0.001). The mean nickel levels were 3.894 ± 1.442, 5.913 ± 2.735, and 19.810 ± 8.452 μg per gram, respectively, at baseline, month 1, and month 6. Chromium concentrations were 1.978 ± 0.721, 4.135 ± 1.591, and 13.760 ± 3.555 μg per gram, respectively. Compared with the baseline, nickel increased by 150% and 510%, respectively, in the first and sixth months (Friedman, P <0.0001), and chromium increased by 200% and 700%, respectively (analysis of variance, P <0.0001).

CONCLUSIONS

Six months of fixed orthodontic treatment might intensify the levels of nickel and chromium in the GCF as well as gingival inflammation.

Biocompatibility and Inflammatory Potential of Titanium Alloys Cultivated with Human Osteoblasts, Fibroblasts and Macrophages

The biomaterials used to maintain or replace functions in the human body consist mainly of metals, ceramics or polymers. In orthopedic surgery, metallic materials, especially titanium and its alloys, are the most common, due to their excellent mechanical properties, corrosion resistance, and biocompatibility. Aside from the established Ti6Al4V alloy, shape memory materials such as nickel-titanium (NiTi) have risen in importance, but are also discussed because of the adverse effects of nickel ions. These might be reduced by specific surface modifications. In the present in vitro study, the osteoblastic cell line MG-63 as well as primary human osteoblasts, fibroblasts, and macrophages were cultured on titanium alloys (forged Ti6Al4V, additive manufactured Ti6Al4V, NiTi, and Diamond-Like-Carbon (DLC)-coated NiTi) to verify their specific biocompatibility and inflammatory potential. Additive manufactured Ti6Al4V and NiTi revealed the highest levels of metabolic cell activity. DLC-coated NiTi appeared as a suitable surface for cell growth, showing the highest collagen production. None of the implant materials caused a strong inflammatory response. In general, no distinct cell-specific response could be observed for the materials and surface coating used. In summary, all tested titanium alloys seem to be biologically appropriate for application in orthopedic surgery.

Nickel-free vs conventional braces for patients allergic to nickel: Gingival and blood parameters during and after treatment

INTRODUCTION

Allergic and inflammatory reactions have commonly been associated with the release of metal ions during orthodontic treatment. Our objective was to evaluate prospectively gingival and blood status in patients allergic to nickel.

METHODS

Allergy to nickel was diagnosed using a patch test. Two groups were established: conventional braces (n = 21) and nickel-free braces (n = 21). The gingival index was used to determine gingival status before treatment, periodically for 12 months (evaluations every 3 months), and 1 month after the removal of the braces. Blood status was evaluated with a complete blood count, including the quantification of nickel and immunoglobin E before treatment, during treatment, and 1 month after removal of the braces. The data were analyzed using Mann-Whitney, Student t, Wilcoxon, repeated measures analysis of variance, Friedman, and chi-square tests. Either the Pearson or the Spearman correlation coefficients were calculated, when appropriate.

RESULTS

The number of basophils increased significantly among the evaluations in both groups (conventional, P = 0.002; nickel-free, P = 0.001), whereas the number of eosinophils and the immunoglobin E levels decreased significantly in the conventional group (P = 0.004). Plasma nickel levels were increased before and during treatment, and decreased 1 month after removing the braces in both groups, but the differences were significant only in the nickel-free group (P = 0.002). No correlations were found between the concentrations of nickel and immunoglobin E, basophils, or eosinophils, or between the gingival index and either bands or segmented neutrophils (P ≥ 0.05).

CONCLUSIONS

Patients treated with nickel-free braces had better gingival health and smaller blood changes than did those treated with conventional braces. All abnormalities tended to be eliminated after the removal of the braces.

Effects of Fixed Orthodontic Treatment Using Conventional, Copper-Included, and Epoxy-Coated Nickel-Titanium Archwires on Salivary Nickel Levels: A Double-Blind Randomized Clinical Trial

Orthodontic archwires, especially nickel-titanium (NiTi) ones, are a major source of nickel release. Despite their importance, no in vivo studies have assessed the ion release from conventional or new generations of NiTi archwires (copper-included and epoxy-coated). This double-blind parallel randomized clinical trial was done on 84 saliva specimens sampled at two time points from 42 orthodontic patients. The patients were randomly divided into three groups of NiTi, copper NiTi (NiTiCu), and epoxy NiTi archwires (n = 14 each). The effects of 2-month treatment, wire types, gender, and age on pretreatment, posttreatment, and time-dependent differences were analyzed statistically (α = 0.05). Salivary nickel concentrations were 10.4571 ± 0.77168 and 11.0779 ± 0.81232 μg/L, respectively, in the baseline and second month. This increase was significant (P = 0.0000, paired t test). The extents of nickel increase in different groups were 0.8279 ± 0.14 (NiTi), 0.6493 ± 0.10 (NiTiCu), and 0.385 ± 0.11 (epoxy-coated NiTi) μg/L (P = 0.0000, one-way analyses of variance (ANOVA)). Differences between each two archwire types were significant (P = 0.000, Tukey). Age and gender did not play a role. It can be concluded that NiTi archwires might increase nickel salivary levels. Epoxy-coated NiTi followed by copper NiTi archwires might release less nickel compared to conventional NiTi ones.

In vitro and in vivo evidence of the cytotoxic and genotoxic effects of metal ions released by orthodontic appliances: A review

Intraoral fixed orthodontic appliances are frequently used in the clinical practice of dentistry. They are made from alloys containing different metals at various percentages. The use of these appliances leads to the long-term exposure of patients to these materials, and the potential toxic effects of this exposure raises concerns about patient safety. Thus, the biocompatibility (corrosion behaviour and toxicity) of these materials has to be evaluated prior to clinical use. In the present report, the most recent studies in the scientific literature examining metal ion release from orthodontic appliances and the toxic effects of these ions have been reviewed with a special focus on cytotoxicity and genotoxicity. Previous studies suggest that a case-by-case safety evaluation is required to take into account the increasing variability of materials, their composition and the manufacturing processes. Moreover, in vivo toxicity studies in regard to metal release, cytotoxicity and genotoxicity are still scarce. Therefore, in vitro and in vivo monitoring studies are needed to establish cause-effect relationships between metal ion release and biomarkers of cytotoxicity and genotoxicity. Further investigations could be performed to elucidate the toxic mechanisms involved in the observed effects with a special emphasis on oxidative damage.

Effects of fixed orthodontic treatment using conventional versus metal-injection molding brackets on salivary nickel and chromium levels: a double-blind randomized clinical trial

INTRODUCTION

Despite the importance of nickel and chromium release from orthodontic brackets, there are no in vivo or in vitro studies on this issue in the case of metal-injection molding (MIM) brackets.

METHODS

Saliva samples were collected from 30 orthodontic patients divided randomly into two groups of conventional and MIM brackets, before treatment and 2 months later. Approved attendees with odd and even numbers were, respectively, assigned to the control and treatment groups. For blinding, the patients were not informed of their bracket types, and the saliva samples were coded. Nickel and chromium levels were determined using atomic absorption spectrophotometry. Data were analysed using repeated-measures two-way analysis of covariance, independent-samples t-test, chi-squared, Spearman and point-biserial correlation coefficients, Mann-Whitney, and Wilcoxon tests (α = 0.05).

RESULTS

Mean nickel level increased from 7.87±8.14 (pre-treatment) to 12.57±9.96 (2nd month) in the control group, and from 8.62±9.85 (pre-treatment) to 8.86±6.42 µg/l in the MIM group. Both of these increases were significant (Wilcoxon P < 0.03). Average chromium level changed from 0.25±0.56 (pre-treatment) to 0.35±0.62 and from 0.42±0.48 to 0.26±0.57 µg/l in the MIM group. Only the reduction observed in the MIM group was significant (Wilcoxon P = 0.0438). Age and gender had no significant influence on ion levels (P > 0.1). The differences between both ions' levels measured in the 60th day in both bracket groups were not significant (Mann-Whitney P > 0.05). The extents of changes over time were not significantly different between the bracket types (Mann-Whitney P > 0.05).

LIMITATIONS

The sample size was not predetermined based on power calculations. The spectrophotometer was limited to detecting chromium concentrations above 0.25 µg/l. Ion discharge from brackets might continuously change. The current in vivo methods are unable to take such fluctuations into account.

CONCLUSION

Nickel might increase in patients undergoing treatment with both bracket types, although the rate of increase might be greater in patients under treatment with conventional brackets. Using MIM brackets might reduce salivary chromium for a trivial but generalizable amount. Still, ion levels leached from conventional versus MIM brackets might not show a difference after 2 months. Age and gender might not affect the ion levels in normal people or orthodontic patients.

REGISTRATION

The protocol is registered offline at the university library.

PROTOCOL

The protocol was not published before the trail commencement.

FUNDING

Self-funded (S. H.).

CONFLICT OF INTEREST

None to declare.

Possible implications of Ni(II) on oral IL-1β-induced inflammatory processes

OBJECTIVES

Nickel (Ni) is one of the main metal elements in orthodontic and prosthetic devices. Different effects of Ni are described ranging from an induction of local inflammation to allergy and cancerous/mutagenic properties. Inflammatory reactions are frequently observed in the oral cavity, but the interrelationship of Ni with those events is still unknown. Therefore, we focused on the impact of Ni on inflammation in vitro.

METHODS

In accordance to previous immersion tests of our lab, human gingival fibroblasts (HGFs) (n=6) were exposed to a pro-inflammatory environment using interleukin-1 beta (IL-1β) and additionally stimulated with different Ni(II) concentrations (400 and 4000ng/ml). At varying time points the expression of pro- and anti-inflammatory as well as matrix degeneration proteins, i.e. MMPs, were analyzed. Furthermore, proliferation assays, wound healing tests and the detection of NF-κB activation were conducted. Unstimulated HGFs served as control.

RESULTS

Our experiments showed that low clinical average Ni(II) levels did not alter pro-inflammatory cytokines significantly compared to control (p>0.05). Instead, a 10-fold higher dose up-regulated these mediators significantly in a time-dependent manner (p<0.01). This was even more pronounced combining both Ni(II) concentrations with an inflammatory condition (p<0.001), MMP expressions were in line with our findings (p<0.001). The mRNA data were supported by proliferation and wound closure assays (p<0.001). However, the combination of both stimuli induced contradictory results. Analyzing NF-κB activation revealed that our results may be in part attributed to NF-κB.

SIGNIFICANCE

Our in vitro study implicated that Ni(II) has various modifying effects on IL-1β-induced inflammatory processes depending on the concentration.

Effect of thermomechanical pre-treatment on short- and long-term Ni release from biomedical NiTi

The effect of annealing and deformation on short-term (21days) and long-term (8months) Ni release from biomedical NiTi wires is studied. The deformation of annealed NiTi wires causes cracking and flaking of the surface oxide layer. Flaking of oxide particles does not uncover the Ni-rich layer underneath the surface oxide layer, since at sites where flaking occurs, a thin (∼25nm) layer of oxide remains on top of this Ni-rich layer. The number of cracks in the oxide and Ni-rich layer, respectively, increases with deformation, and intercrystalline crack propagation into the Ni-rich layer and the NiTi bulk is observed. In plastically deformed wires, the cracks may remain opened, providing access of immersion liquid to these zones. Characteristics and quantity of short-term Ni release are significantly affected by the pre-deformation, resulting in an up to 2 times higher total Ni release within the first 21days of deformed compared to annealed wires. Pre-deformation does not significantly influence long-term Ni release; all annealed and deformed samples exhibit similar long-term Ni release rates. The source of Ni during short-term release is the Ni contained in the surface zone of the oxide layer. For high pre-deformation, the Ni-rich layer is a second source for Ni. This second source is also the cause for Ni release in long-term immersion experiments.

Effect of fixed orthodontic therapy on urinary nickel levels: a long-term retrospective cohort study

Nickel constitutes about 8-60 % of orthodontic alloys. It is known as an allergenic/cytotoxic trace metal. Therefore, it should be investigated in patients undergoing orthodontic treatment which might last for 2 or 3 years. However, no controlled studies have assessed the influence of orthodontic treatments of longer than 5 months on its systemic levels. Thus, the aim of this retrospective cohort study was to evaluate systemic nickel in patients undergoing orthodontic therapy for a minimum period of 1 year. In this study, urinary nickel concentrations in 20 female and 10 male patients being treated with stainless steel appliances were measured using atomic absorption spectrophotometry. The same procedure was done on a control group of the patients' same-gender near-age siblings (n = 30). The effect of treatment and gender on urinary nickel levels were assessed using a repeated-measures two-way analysis of variance (ANOVA) and a Tukey test (α = 0.05). The mean treatment duration was 17.1 ± 6.4 months (range, 12-21). The mean nickel concentrations in male and female patients were 9.67 ± 3.25 and 9.9 ± 3.83 μg/L, respectively. These statistics for male and female control subjects were 6.65 ± 2.57 and 8.43 ± 2.94 μg/L, respectively. The ANOVA showed a statistically significant difference between the urinary nickel levels of the treatment and the control groups (P = 0.009) but not between the genders (P = 0.194). The interaction between gender and treatment was also nonsignificant (P = 0.337). The Tukey test indicated that the increase in nickel was higher in male patients, in comparison to their brothers (P < 0.05). It could be concluded that orthodontic therapy for longer durations with stainless-steel archwires might elevate slightly, but significantly, urinary nickel levels.

Effects of long-term fixed orthodontic treatment on salivary nickel and chromium levels: a 1-year prospective cohort study

Effect of long-term orthodontic treatment on salivary nickel and chromium has not been quite assessed except in few retrospective studies with controversial results. The aim of this prospective study was to measure salivary levels of these ions during 1 year of orthodontic treatment. Saliva samples were collected from 20 orthodontic patients, before treatment (control) and 6 and 12 months later. Nickel and chromium concentrations were determined using atomic absorption spectrophotometry. Data were analyzed using one- and two-way repeated-measures ANOVA, Bonferroni, Friedman (α = 0.05), and Wilcoxon signed-ranks tests (α = 0.016). Average nickel level changed from 9.75 ± 5.02 to 10.37 ± 6.94 and then to 8.32 ± 4.36 μg/L in 1 year. Average chromium concentration changed from 3.86 ± 1.34 to 4.6 ± 6.11 and then to 2.04 ± 1.66 μg/L. Alterations in nickel values were not statistically significant [P = 0.468 (ANOVA)], but fluctuations in chromium levels were [P = 0.021 (Friedman)]. The decrease in chromium concentration after 12 months was significant compared to the control [P = 0.004 (Wilcoxon)]. Although slightly increased after 6 months, the concentration of both ions dropped to levels slightly lower than the control groups after 12 months.

Surface modification of biomaterials using plasma immersion ion implantation and deposition

Although remarkable progress has been made on biomaterial research, the ideal biomaterial that satisfies all the technical requirements and biological functions is not available up to now. Surface modification seems to be a more economic and efficient way to adjust existing conventional biomaterials to meet the current and ever-evolving clinical needs. From an industrial perspective, plasma immersion ion implantation and deposition (PIII&D) is an attractive method for biomaterials owing to its capability of treating objects with irregular shapes, as well as the control of coating composition. It is well acknowledged that the physico-chemical characteristics of biomaterials are the decisive factors greatly affecting the biological responses of biomaterials including bioactivity, haemocompatibility and antibacterial activity. Here, we mainly review the recent advances in surface modification of biomaterials via PIII&D technology, especially titanium alloys and polymers used for orthopaedic, dental and cardiovascular implants. Moreover, the variations of biological performances depending on the physico-chemical properties of modified biomaterials will be discussed.