Systemic levels of metallic ions released from orthodontic mini-implants

Development of a novel hybrid Ti6Al4V-ZrO2 surface with high wear resistance by laser and hot pressing techniques for dental implants

The development of implant metal-free surfaces has gained attention since non-benefic results have been reported related to the metallic ions released from metal implants to the human body. Ceramic coatings have been proposed as a possible solution however, the detachment of these coatings, during implantation or even in function, can compromise its function. In order to overcome this problem, this work proposes a novel hybrid Ti6Al4V-ZrO2 surface, starting with laser texturing of the Ti6Al4V substrate by Laser Nd:YV04, followed by the allocation of the zirconia (ZrO2) powder and its subsequent sintering by hot pressing process. Results revealed that zirconia strongly adheres to titanium textured surfaces since no detachment was found under tribological and adhesion scratch tests. Moreover, the tribological results showed that the incorporation of zirconia into textured titanium surface reduces significantly the wear rate of titanium (≈93%), which is a good indicator of low metallic particles/ions released to the body. These results suggest that this novel surface with good aesthetic properties and improved wear resistance (given by zirconia) and mechanical resistance (from titanium) can be a promising solution for dental implants, especially for implant/abutment or abutment/ceramic contact zones, and thus have a huge impact on the long-term performance of implants.

Minimization of Adverse Effects Associated with Dental Alloys

Metal alloys are one of the most popular materials used in current dental practice. In the oral cavity, metal structures are exposed to various mechanical and chemical factors. Consequently, metal ions are released into the oral fluid, which may negatively affect the surrounding tissues and even internal organs. Adverse effects associated with metallic oral appliances may have various local and systemic manifestations, such as mouth burning, potentially malignant oral lesions, and local or systemic hypersensitivity. However, clear diagnostic criteria and treatment guidelines for adverse effects associated with dental alloys have not been developed yet. The present comprehensive literature review aims (1) to summarize the current information related to possible side effects of metallic oral appliances; (2) to analyze the risk factors aggravating the negative effects of dental alloys; and (3) to develop recommendations for diagnosis, management, and prevention of pathological conditions associated with metallic oral appliances.

Nrf2 in the Field of Dentistry with Special Attention to NLRP3

The aim of this review article was to summarize the functional implications of the nuclear factor E2-related factor or nuclear factor (erythroid-derived 2)-like 2 (Nrf2), with special attention to the NACHT (nucleotide-binding oligomerization), LRR (leucine-rich repeat), and PYD (pyrin domain) domains-containing protein 3 (NLRP3) inflammasome in the field of dentistry. NLRP3 plays a crucial role in the progression of inflammatory and adaptive immune responses throughout the body. It is already known that this inflammasome is a key regulator of several systemic diseases. The initiation and activation of NLRP3 starts with the oral microbiome and its association with the pathogenesis and progression of several oral diseases, including periodontitis, periapical periodontitis, and oral squamous cell carcinoma (OSCC). The possible role of the inflammasome in oral disease conditions may involve the aberrant regulation of various response mechanisms, not only in the mouth but in the whole body. Understanding the cellular and molecular biology of the NLRP3 inflammasome and its relationship to Nrf2 is necessary for the rationale when suggesting it as a potential therapeutic target for treatment and prevention of oral inflammatory and immunological disorders. In this review, we highlighted the current knowledge about NLRP3, its likely role in the pathogenesis of various inflammatory oral processes, and its crosstalk with Nrf2, which might offer future possibilities for disease prevention and targeted therapy in the field of dentistry and oral health.

Is titanium alloy Ti-6Al-4 V cytotoxic to gingival fibroblasts-A systematic review

OBJECTIVES

Grade V titanium alloy (Ti-6Al-4 V) is a well-recognized metallic biomaterial for medical implants. There has been some controversy regarding the use of this alloy in medical devices in relation to the toxicity of vanadium. In Dentistry, Ti-6Al-4 V remains prevalent. This systematic review aims to evaluate the effects of Ti-6Al-4 V on cells relevant to oral environments such as gingival fibroblasts.

MATERIALS AND METHODS

A literature search was undertaken for relevant English language publications in the following databases: Dental and Oral Science, Medline and Web of Science. The electronic search was supplemented with a search of references.

RESULTS

After application of inclusion and exclusion criteria. A total of eight papers are included in this review. These papers were all in vitro studies and were categorized into whole implant, discs, or implant particles based on the type of test materials used in the studies.

CONCLUSION

Based on the analyses of the eight included studies in this review, if Ti-6Al-4 V as a material is unchallenged, i.e., as a whole implant in pH neutral environments, there appears to be little effect on fibroblasts. If Ti-6Al-4 V is challenged through corrosion or wear (particle release), the subsequent release of vanadium and aluminium particles has an increased cytotoxic effect in vitro in comparison to commercially pure titanium, hence concerns should be raised in the clinical setting.

Physicochemical and Biological Characterization of Ti6Al4V Particles Obtained by Implantoplasty: An In Vitro Study. Part I

Implantoplasty is a mechanical decontamination technique that consists of polishing the supra-osseous component of the dental implant with peri-implantitis. This technique releases metal particles in the form of metal swarf and dust into the peri-implant environment. In the present in vitro study, the following physicochemical characterization tests were carried out: specific surface area, granulometry, contact angle, crystalline structure, morphology, and ion release. Besides, cytotoxicity was in turn evaluated by determining the fibroblastic and osteoblastic cell viability. As a result, the metal debris obtained by implantoplasty presented an equivalent diameter value of 159 µm (range 6–1850 µm) and a specific surface area of 0.3 m²/g on average. The particle had a plate-like shape of different sizes. The release of vanadium ions in Hank’s solution at 37 °C showed no signs of stabilization and was greater than that of titanium and aluminum ions, which means that the alloy suffers from a degradation. The particles exhibited cytotoxic effects upon human osteoblastic and fibroblastic cells in the whole extract. In conclusion, metal debris released by implantoplasty showed different sizes, surface structures and shapes. Vanadium ion levels were higher than that those of the other metal ions, and cell viability assays showed that these particles produce a significant loss of cytocompatibility on osteoblasts and fibroblasts, which means that the main cells of the peri-implant tissues might be injured.

Effect of Mo and space holder content on microstructure, mechanical and corrosion properties in Ti6AlxMo based alloy for bone implant

The porous alloys of Ti6Al(3-15)Mo were developed to replace the fractured bone; the alloy consists of 6 wt% of Al which was taken as α the phase stabilizer and (3-15) wt% Mo with an increment of 3 wt% was taken as β phase stabilizer. The porosity of these fabricated porous alloys was controlled by adjusting volume% of the ammonium bicarbonate (SH). These porous samples were characterized in terms of their microstructure, compressive strength, elastic modulus, energy absorption, ion release and corrosion rate in simulated body fluid (SBF) and these properties are compared with the existing alloys and human bone. The fabricated porous samples were characterized, and the obtained results were analysed as a function of Mo concentration and the volume% of space holder content. Three phases were found in the microstructure: α, α₂ and β phase of titanium. Increase in Mo content from 3 to 15 wt% has increased the volume fraction of β phase from 7.45% to 64.09% and Kirkendall pores also are observed to be increased with increase in Mo content. α and α₂ phase was differentiated by the TEM and phase map of EBSD images. The plateau stress, elastic modulus and energy absorption are observed to be decreased, and the densification strain is observed to be increased with the addition of Mo and SH content. The released ion concentration and corrosion rate are far below the tolerance limits of Ti, Al and Mo elements, in the static immersion test conducted in SBF solution.

Understanding the implant performance of magnetically controlled growing spine rods: a review article

PURPOSE

Early-Onset Scoliosis (EOS) (defined as a curvature of the spine ≥ 10° with onset before 10 years of age) if not properly treated, can lead to increased morbidity and mortality. Traditionally Growing Rods (TGRs), implants fixated to the spine and extended every 6-8 months by surgery, are considered the gold standard, but Magnetically Controlled Growing Rods (MCGRs) avoid multiple surgeries. While the potential benefit of outpatient distraction procedure with MCGR is huge, concerns still remain about its risks, up to the release of a Medical Device Alert (MDA) by the Medicines and Healthcare Regulatory Agency (MHRA) advising not to implant MCGRs until further notice. The aim of this literature review is to (1) give an overview on the use of MCGRs and (2) identify what is currently understood about the surgical, implant and patient factors associated with the use of MCGRs.

METHODS

Systematic literature review.

RESULTS

Surgical factors such as use of single rod configuration or incorrect rod contouring might affect early failure of MCGRs. Patient's older age and higher BMI are correlated with rod slippage. Wear debris and distraction mechanism failure may result from implant design and iteration.

CONCLUSION

Despite the complications reported, this technology still offers one of the best solutions to spine surgeons dealing with severe EOS. Lowering the complication rate by identifying risk factors for failure is possible and further studies in this direction are required. Once the risk factors are well described, some of these can be addressed enabling a safer use of MCGRs.

Distribution and Chemical Speciation of Exogenous Micro- and Nanoparticles in Inflamed Soft Tissue Adjacent to Titanium and Ceramic Dental Implants

Degradation of the implant surface and particle release/formation as an inflammation catalyst mechanism is an emerging concept in dental medicine that may help explain the pathogenesis of peri-implantitis. The aim of the present study was a synchrotron-based characterization of micro- and nanosized implant-related particles in inflamed human tissues around titanium and ceramic dental implants that exhibited signs of peri-implantitis. Size, distribution, and chemical speciation of the exogenous micro- and nanosized particle content were evaluated using synchrotron μ-X-ray fluorescence spectroscopy (XRF), nano-XRF, and μ-X-ray absorption near-edge structure (XANES). Titanium particles, with variable speciation, were detected in all tissue sections associated with titanium implants. Ceramic particles were found in five out of eight tissue samples associated with ceramic implants. Particles ranged in size from micro- to nanoscale. The local density of both titanium and ceramic particles was calculated to be as high as ∼40 million particles/mm³. μ-XANES identified titanium in predominantly two different chemistries, including metallic and titanium dioxide (TiO₂). The findings highlight the propensity for particle accumulation in the inflamed tissues around dental implants and will help in guiding toxicological studies to determine the biological significance of such exposures.

Cytotoxicity of orthodontic temporary anchorage devices on human periodontal ligament fibroblasts in vitro

Objectives

The objective of this study is to test cytotoxicity of four brands of commercially available orthodontic temporary anchorage devices (TADs).

Setting and sample population

Twenty-four (six for each brand, i.e., Aarhus [AO]; Dual top [RMO]; Vector TAS [ORMCO]; and Unitek TAD [3M UNITEK]) TADs were tested.

Materials and methods

Twenty-four (six for each brand, i.e., Aarhus [AO]; Dual top [RMO]; Vector TAS [ORMCO]; and Unitek TAD [3M UNITEK]) TADs were individually incubated in complete cell culture medium and shaken at a rate of 1.5 rpm at 37°C for 30 days to extract possible toxic substances in conditioned media (CM). To test cytotoxicity, human periodontal ligament fibroblasts were cultured and exposed to the CM for 24 hr, followed by the examinations of morphological changes, cell viability (MTT assay), and cell damage (lactate dehydrogenase [LDH] assay).

Results

No morphological changes were observed in any of the four brands of TADs compared with the negative control. LDH assay showed that none of the four brands of TADs caused significant cell damage after CM treatment compared with the negative control (P > .05). No significant differences were found between any of the four brands of TADs (P > .05). MTT assay showed similar results as did the LDH assay, except for a statistically significant difference found in the TADs from 3M UNITEK compared with the negative control (P = .047).

Conclusions

According to the International Standard Organization standards, except for the TAD from 3M, none of the other three brands of commercially available TADs (from AO, RMO, and ORMCO) exhibited significant cytotoxicity, suggesting their safe clinical applications.

Titanium Ions Promote Exogenous Calcium-Dependent Calcium Influx in Activated Jurkat T Cells: A Possible Mechanism to Explain Its Immunostimulatory Properties

Titanium and its alloys have been widely used in dental and orthopedic implants. Owing to the biotribocorrosion behavior of implants in simulated oral environment, Ti(IV) ions could be released into surrounding tissues. Current studies have found that Ti(IV) ions could affect the biological activities of immune cells in adjacent tissues and subsequently jeopardize the long-term performance of implant prostheses. However, the potential mechanism underlying its immunomodulatory properties remains unclear. Calcium signaling has been confirmed to be involved in regulation of lymphocyte immune function. Therefore, we hypothesize that Ti(IV) ions modulated T cell function through the change of intracellular calcium concentrations. This study is aimed at exploring the role of intracellular calcium responses in the modulatory effect of Ti(IV) ions on unactivated and phytohemagglutinin-activated Jurkat T cells. Here, we confirmed that Ti(IV) ions within a certain concentration range induced CD69 expression on both unactivated and activated T cells in our study. Additionally, the combined stimulation with Ti(IV) ions and PHA increased expression of IL-1β, TNF-α, and RANKL. Furthermore, we found that treatment with Ti(IV) induced a transitory increase in the levels of [Ca²⁺]_i in activated Jurkat cells, dependent on the presence of exogenous calcium. Treatment with different doses of Ti(IV) for 24 h significantly increased the levels of [Ca²⁺]_i in the activated Jurkat cells in a dose-dependent manner, but had little effect in the unactivated cells. Treatment with Ti(IV) did not significantly affect the PLCγ1 activation and inositol-1,4,5-trisphosphate (IP₃) secretion in Jurkat cells. Taken together, these data indicated that Ti(IV) enhanced calcium influx during the T cell activation, independent of IP₃-mediated intracellular calcium release. Our work provides insights into the mechanism involved in the regulation of lymphocyte behaviors under the effect of Ti(IV) ions, which may help to develop therapeutic strategies for dental implant failures.

Proliferation of Osteoblasts on Laser-Modified Nanostructured Titanium Surfaces

Nanostructured titanium has become a useful material for biomedical applications such as dental implants. Certain surface properties (grain size, roughness, wettability) are highly expected to promote cell adhesion and osseointegration. The aim of this study was to compare the biocompatibilities of several titanium materials using human osteoblast cell line hFOB 1.19. Eight different types of specimens were examined: machined commercially pure grade 2 (cpTi2) and 4 (cpTi4) titanium, nanostructured titanium of the same grades (nTi2, nTi4), and corresponding specimens with laser-treated surfaces (cpTi2L, cpTi4L, nTi2L, nTi4L). Their surface topography was evaluated by means of scanning electron microscopy. Surface roughness was measured using a mechanical contact profilometer. Specimens with laser-treated surfaces had significantly higher surface roughness. Wettability was measured by the drop contact angle method. Nanostructured samples had significantly higher wettability. Cell proliferation after 48 hours from plating was assessed by viability and proliferation assay. The highest proliferation of osteoblasts was found in nTi4 specimens. The analysis of cell proliferation revealed a difference between machined and laser-treated specimens. The mean proliferation was lower on the laser-treated titanium materials. Although plain laser treatment increases surface roughness and wettability, it does not seem to lead to improved biocompatibility.

Polymeric materials and films in dentistry: An overview

The use of polymeric materials (PMs) and polymeric films (PMFs) has increased in medicine and dentistry. This increasing interest is attributed to not only the excellent surfaces of PMs and PMFs but also their desired mechanical and biological properties, low production cost, and ease in processing, allowing them to be tailored for a wide range of applications. Specifically, PMs and PMFs are used in dentistry for their antimicrobial, drug delivery properties; in preventive, restorative and regenerative therapies; and for corrosion and friction reduction. PMFs such as acrylic acid copolymers are used as a dental adhesive; polylactic acids are used for dental pulp and dentin regeneration, and bioactive polymers are used as advanced drug delivery systems. The objective of this article was to review the literatures on the latest advancements in the use of PMs and PMFs in medicine and dentistry. Published literature (1990–2017) on PMs and PMFs for use in medicine and dentistry was reviewed using MEDLINE/PubMed and ScienceDirect resources. Furthermore, this review also explores the diversity of latest PMs and PMFs that have been utilized in dental applications, and analyzes the benefits and limitations of PMs and PMFs. Most of the PMs and PMFs have shown to improve the biomechanical properties of dental materials, but in future, more clinical studies are needed to create better treatment guidelines for patients.

The role of citrate, lactate and transferrin in determining titanium release from surgical devices into human serum

The presence of ionic titanium in the serum of patients with titanium implants is currently unexplained. This is presumed due to corrosion, and yet the serum titanium concentration measured in patients is far greater than that predicted by its solubility. The binding of titanium ion as Ti(IV) to human transferrin (hTF) in serum indicates that Ti(IV) ions interact with human physiology. This is an intriguing finding since there is currently no known role for titanium ions in human physiology. Thus, understanding the factors that determine in vivo titanium ion release is relevant to further understanding this metal's interactions with human biochemistry. The present study sought to determine the extent of titanium ion release of into human serum in vitro, and the role of citrate, lactate and hTF in this process. It was found that, when surgical devices of commercially pure titanium were placed into human serum, citrate and lactate concentrations were the prime determinants of titanium release. Crystallography revealed Ti(IV) bound to hTF in the presence of citrate alone, signalling that citrate can act as an independent ligand for Ti(IV) binding to hTF. Based on these findings, a two-stage process of titanium ion release into human serum that is dependent upon both citrate and hTF is proposed to explain the ongoing presence of titanium ion in human subjects with implanted titanium devices.

Evaluation of cytotoxicity and corrosion resistance of orthodontic mini-implants

Objective:

To evaluate and compare in vitro cytotoxicity and corrosion resistance of mini-implants from three different commercial brands used for orthodontic anchorage.

Methods:

Six mini-implants (Conexão(tm), Neodent(tm) and SIN(tm)) were separately immersed in artificial saliva (pH 6.76) for 30 and 60 days. The cytotoxicity of the corrosion extracts was assessed in L929 cell cultures using the violet crystal and MTT assays, as well as cell morphology under light microscopy. Metal surface characteristics before and after immersion in artificial saliva were assessed by means of scanning electron microscopy (SEM). The samples underwent atomic absorption spectrophotometry to determine the concentrations of aluminum and vanadium ions, constituent elements of the alloy that present potential toxicity. For statistical analysis, one-way ANOVA/Bonferroni tests were used for comparisons among groups with p < 0.05 considered significant. Statistical analysis was carried out with Graph Pad PRISM software Version 4.0.

Results:

No changes in cell viability or morphology were observed. Mini-implants SEM images revealed smooth surfaces with no obvious traces of corrosion. The extracts assessed by means of atomic absorption spectrophotometry presented concentrations of aluminum and vanadium ions below 1.0 µg/mL and 0.5 µg/mL, respectively.

Conclusion:

Orthodontic mini-implants manufactured by Conexão(tm), Neodent(tm) and SIN(tm) present high corrosion resistance and are not cytotoxic.

Influence of acid treatment on surface properties and in vivo performance of Ti6Al4V alloy for biomedical applications

The purpose of this work was to investigate the influence of acid treatment on the surface properties and in vivo performance of titanium grade 5 (Ti6Al4V) alloy. Mini-implants with surface treatment were inserted into New Zealand rabbit tibia for 1, 4 and 8 weeks. SEM analysis showed intercommunicated micropores in acid treated samples. AFM showed micron and sub-micron roughness. The thickness of the titanium oxide layer increased with surface treatment, with a significant reduction of Al and V concentration. Acid treated implant removal torque was larger than without treatment. The implants/bone interface of acid treated implants showed dense adhered Ca/P particles with spreading osteoblasts after 4 weeks and newly formed bone trabeculae after 8 weeks. Analysis of rabbit blood that received treated implant showed lower Al and V contents at all times. Acid treatment improved surface morphology and mechanical stability, which allowed initial events of osseointegration, while Al-V ion release was reduced. GRAPHICAL ABTSRACT.

Are clinical findings of systemic titanium dispersion following implantation explained by available in vitro evidence? An evidence-based analysis

Although the presence of titanium wear particles released into tissues is known to induce local inflammation following the therapeutic implantation of titanium devices into humans, the role that titanium ions play in adverse tissue responses has received little attention. Support that ongoing titanium ion release occurs is evidenced by the presence of ionic titanium bound to transferrin in blood, and ongoing excretion in the urine of patients with titanium devices. However, as reports documenting the presence of titanium within tissues do not distinguish between particulate and ionic forms due to technical challenges, the degree to which ionic titanium is released into tissues is unknown. To determine the potential for titanium ion release into tissues, this study evaluates available in vitro evidence relating to the release of ionic titanium under physiological conditions. This is a systematic literature review of studies reporting titanium ion release into solutions from titanium devices under conditions replicating the interstitial pH and constituents. Inclusion and exclusion criteria were defined. Of 452 articles identified, titanium ions were reported in nine media relevant to human biology in seventeen studies. Only one study, using human serum replicated both physiological pH and the concentration of constituents while reporting the presence of titanium ions. While there is insufficient information to explain the factors that contribute to the presence of titanium ions in serum of humans implanted with titanium devices, currently available information suggests that areas of future inquiry include the role of transferrin and organic acids.

A comparative evaluation of ion release from different commercially-available orthodontic mini-implants – an in-vitro study

Background

Titanium alloy mini-implants have become popular in recent times and have been extensively used and studied. Although corrosion resistance of orthodontic materials has always been of concern, this property has been the least explored. The present study aimed to assess the composition, surface characterisation and corrosion resistance of five commercially available mini-implants by assaying ion release in artificial saliva.

Methods

Ten mini-implants each from five companies were obtained: Group 1 – AbsoAnchor (Dentos Inc, South Korea); Group 2 – Microimplant Anchorage System (MIA, Biomaterials Korea); Group 3 – The Orthodontic Mini Anchorage System (TOMAS, Dentaurum, Germany); Group 4 – mini-implants (Denticon, Maharashtra, India); Group 5 – orthodontic mini-implants (J.J.Orthodontics, Kerala, India). One mini-implant from each group was subjected to characterisation and surface microstructure analysis using Energy Dispersive Atomic Spectrometry (EDAX) and Scanning Electron Microscope (SEM), respectively. Ten miniimplants were immersed for 30 days in Fusayama-Meyer artificial saliva solution and the release of titanium, aluminium and vanadium ions was detected with Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES). The Kruskal-Wallis test was used for multi-variate analysis. In order to determine the significant differences between the groups on independent samples, the Mann-Whitney U test (bi-variate analysis) was applied.

Results and conclusion

All groups showed machining defects but surface pitting after immersion was mostly evident in Group 4. Although the composition of all the implants was comparable, there was a statistically significant difference in the Ti, Al and V release between Group 4 – the group with maximum release – and Group 2, the group with least release.

Metal elements in tissue with dental peri-implantitis: a pilot study

OBJECTIVES

Dental peri-implantitis is characterized by a multifactorial etiology. The role of metal elements as an etiological factor for peri-implantitis is still unclear. The aim of this study was to investigate the incidence of metal elements in bone and mucosal tissues around dental Grade 4 CP titanium implants with signs of peri-implantitis in human patients.

METHODS

In this prospective pilot study, all patients were enrolled consecutively in two study centers. Bone and soft tissue samples of patients with peri-implantitis with indication for explantation were analyzed for the incidence of different elements (Ca, P, Ti, Fe) by means of synchrotron radiation X-ray fluorescence spectroscopy (SRXRF) and polarized light microscopy (PLM). The existence of macrophages and lymphocytes in the histologic specimens was analyzed.

RESULTS

Biopsies of 12 patients (seven bone samples, five mucosal samples) were included and analyzed. In nine of the 12 samples (75%), the SRXRF examination revealed the existence of titanium (Ti) and an associated occurrence with Iron (Fe). Metal particles were detected in peri-implant soft tissue using PLM. In samples with increased titanium concentration, lymphocytes were detected, whereas M1 macrophages were predominantly seen in samples with metal particles.

CONCLUSION

Titanium and Iron elements were found in soft and hard tissue biopsies retrieved from peri-implantitis sites. Further histologic and immunohistochemical studies need to clarify which specific immune reaction metal elements/particles induce in dental peri-implant tissue.

In vivo determination of aluminum, cobalt, chromium, copper, nickel, titanium and vanadium in oral mucosa cells from orthodontic patients with mini-implants by Inductively coupled plasma-mass spectrometry (ICP-MS)

Miniscrews are used as orthodontic anchorage devices in the dentistry clinical practice but the in vivo metallic release from these structures has been not previously investigated. The aim of this study was to determine the content of Al, Co, Cr, Cu, Ni, Ti and V in oral mucosa cells of control subjects, patients under orthodontic treatment and with both, orthodontic treatment and miniscrew, in order to know the contribution of these mini-implants to the total metallic content. ICP-MS measurements revealed the following ascending order: Cr<Ni<Ti<Cu<Al, and Co and V were practically undetected. Significant differences in comparison to the control group were found for Cu in the orthodontic group, and for Ni in both, orthodontic and orthodontic+miniscrew groups. Potential correlations among metallic elements and with some clinical factors were also explored. These findings suggest that miniscrews do not increase significantly the metal release.

Preliminary study of genotoxicity evaluation of orthodontic miniscrews on mucosa oral cells by the alkaline comet assay

Miniscrew implants are widely used nowadays in orthodontic treatments due to their good results in clinical practice. However, data regarding the biocompatibility of commercially available orthodontic miniscrews and temporary devices are very scarce, and their role as genotoxicity inducers has been not previously evaluated with the alkaline comet assay. The aim of this study was to investigate the DNA damage in buccal cells of patients subjected to orthodontic treatments. The alkaline comet assay has been applied in oral mucosa cells from patients treated with conventional orthodontic treatment in comparison to patients treated additionally with miniscrews, non-treated volunteers (control) and smoking volunteers (positive control). The application of orthodontic appliances and miniscrews induced significant and similar (2-fold) increases of %DNA in tail in comparison to control group. Females experienced a significant increase in %DNA in all the treatments in comparison to the control group, whereas males showed significant damage only with the combined orthodontic and miniscrew treatment. In conclusion, conventional orthodontic appliances induced genotoxicity, and the incorporation of miniscrews assayed did not imply any additional increase of DNA damage.

Retrieval analysis of immediately loaded orthodontic mini-implants: material and tissue characterization

OBJECTIVE

To investigate the morphological and compositional alterations of retrieved orthodontic mini-implants and the type of adjacent bone, in relation to loading period and anatomical region.

MATERIALS AND METHODS

Seventy orthodontic mini-implants (Aarhus: n = 35 and AbsoAnchor: n = 35) were placed in the maxilla and mandible of 33 orthodontic patients for anchorage purposes. All mini-implants were immediately loaded for a period specified by treatment plan. Fifty-nine mini-implants were retrieved (Aarhus: n = 29 and AbsoAnchor: n = 30) and examined by stereomicroscopy, reflection Fourier transform infrared microspectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Tissue samples adjacent to the implants were histologically examined to identify the bone type.

RESULTS

Changes in surface finish, formation of biological integuments, and compositional alterations mainly due to adsorption of proteinaceous material (rich in C, O, N, OH, NH, CH2/CH3, amide I, II, and III, and CH-OH) were identified in all mini-implants. In some cases, mineralized fragments were identified (rich in Ca, P, and Ca-P). In 25 out of the 59 histological sections examined, woven and lamellar bone types were detected. In 12 sections, only woven bone was detected, whereas in the residual 22, only lamellar bone was identified. A significant correlation was found between histological result and loading time but not between histology and region.

CONCLUSION

Morphological and elemental alterations were found for both types of mini-implant surfaces. An increase of the loading period increased the possibility of lamellar bone development around mini-implants.

Effect of pH on in vitro biocompatibility of orthodontic miniscrew implants

Background

Although the clinical use of miniscrews has been investigated on a large scale, little is known about their biocompatibility. Since low pH can affect corrosion resistance, the aim of this study was to evaluate the cytotoxic effect of orthodontic miniscrews in different pH conditions.

Methods

Four orthodontic miniscrews of stainless steel and grade IV and grade V titanium were immersed in a pH 7 and pH 4 saline solution for 1, 7, 14, 21, 28, and 84 days. Human osteogenic sarcoma cells (U2OS), permanent human keratinocytes (HaCat), and primary human gingival fibroblasts (HGF) were exposed to eluates, and the mitochondrial dehydrogenase activity was measured after 24 h to assess the cytoxicity. The results were analyzed using the Mann-Whitney U test (P < 0.05).

Results

When exposed to pH 7-conditioned eluates, the cell lines showed an even greater viability than untreated cells. On the contrary, the results revealed a statistically significant decrease in U2OS, HaCat, and HGF viability after exposure to eluates obtained at pH 4. Among the cell lines tested, HGF showed the most significant decrease of mitochondrial activity. Interestingly, grade V titanium miniscrews caused highest toxic effects when immersed at pH 4.

Conclusions

The results suggested that at pH 7, all the miniscrews are biocompatible while the eluates obtained at pH 4 showed significant cytotoxicity response. Moreover, different cell lines can produce different responses to miniscrew eluates.

Nanostructured severe plastic deformation processed titanium for orthodontic mini-implants

Titanium mini-implants have been successfully used as anchorage devices in Orthodontics. Commercially pure titanium (cpTi) was recently replaced by Ti-6Al-4V alloy as the mini-implant material base due to the higher strength properties of the alloy. However, the lower corrosion resistance and the lower biocompatibility have been lowering the success rate of Ti-6Al-4V mini-implants. Nanostructured titanium (nTi) is commercially pure titanium that was nanostructured by a specific technique of severe plastic deformation. It is bioinert, does not contain potentially toxic or allergic additives, and has higher specific strength properties than any other titanium applied in medical implants. The higher strength properties associated to the higher biocompatibility make nTi potentially useful for orthodontic mini-implant applications, theoretically overcoming cpTi and Ti-6Al-4V mini-implants. The purposes of the this work were to process nTi, to mechanically compare cpTi, Ti-6Al-4V, and nTi mini-implants by torque test, and to evaluate both the surface morphology and the fracture surface characteristics of them by SEM. Torque test results showed significant increase in the maximum torque resistance of nTi mini-implants when compared to cpTi mini-implants, and no statistical difference between Ti-6Al-4V and nTi mini-implants. SEM analysis demonstrated smooth surface morphology and transgranular fracture aspect for nTi mini-implants. Since nanostructured titanium mini-implants have mechanical properties comparable to titanium alloy mini-implants, and biocompatibility comparable to commercially pure titanium mini-implants, it is suggestive that nanostructured titanium can replace Ti-6Al-4V alloy as the material base for mini-implants.

Serum titanium, niobium, and aluminum levels after instrumented spinal arthrodesis in children

STUDY DESIGN

A prospective cohort study.

OBJECTIVE

To determine serum titanium, niobium, and aluminum levels in pediatric patients within the first postoperative year after instrumented spinal arthrodesis.

SUMMARY OF BACKGROUND DATA

Instrumented spinal arthrodesis is a common procedure to correct scoliosis and kyphosis. Titanium-based instrumentation is increasingly favored due to enhanced biomechanical properties, but concerns have arisen regarding metal debris release and the potential for local and systemic complications.

METHODS

The pattern of systemic metal release over time was evaluated by measuring serum titanium, niobium, and aluminum levels preoperatively and 1 week, 1 month, 6 months, and 12 months after instrumented spinal arthrodesis using a titanium alloy. Serum metal levels were measured using high-resolution inductively coupled plasma mass spectrometry.

RESULTS

Thirty-two patients were included in the study group. Mean age at surgery was 14.7 years. Preoperative and postoperative concentrations of serum titanium and niobium were significantly different (P = 0.0001). Median postoperative serum concentrations of titanium and niobium were elevated 2.4- and 5.9-fold above the normal range respectively with 95% and 99% of samples elevated postoperatively. A significant and rapid rise in serum titanium and niobium levels was observed within the first postoperative week, after which elevated serum levels persisted up to 12 months.

CONCLUSION

We report abnormally elevated serum titanium and niobium levels in patients with titanium-based spinal instrumentation up to 12 months. The long-term systemic consequences of debris generated by wear and corrosion of spinal instrumentation is unclear but concerning, particularly as these implants inserted into the pediatric population may remain in situ for beyond 6 decades.

Corrosion of orthodontic temporary anchorage devices

Corrosion of orthodontic miniscrews or temporary anchorage devices (TADs) has been proposed as a contributor to inflammation, which in turn is a factor in the clinical success of miniscrews. The purpose of this study was to measure the electrochemical properties of orthodontic miniscrews in artificial saliva with and without fluoride. The corrosion properties of three miniscrew products (VectorTAS, Ormco Corp.; Unitek TAD, 3M Unitek; and Through-Hole Screw, American Orthodontics) were tested in an artificial saliva (Fusayama-Meyer) with (1500 ppm) or without fluoride (n = 10/product/solution). Open circuit potential (OCP), polarization resistance (R p), and corrosion current (I corr) were measured and statistically analysed with the Friedman/Tukey least significant difference tests. No significant differences (P > 0.05) between miniscrews with regard to OCP, R p, and I corr were found except that the American Orthodontics miniscrews had a significantly (P < 0.05) more noble OCP compared to the others. Incorporation of 1500 ppm fluoride in the artificial saliva significantly (P < 0.001) lowered the OCP, reduced the polarization resistance, and increased the corrosion current of each miniscrew product. Few differences existed in the electrochemical properties of miniscrews from the three different manufacturers; however, exposure to fluoride was detrimental to the corrosion properties of all miniscrews.

Do sand blasted with large grit and acid etched surface treated mini-implants remain stationary under orthodontic forces?

OBJECTIVES

To determine the positional stability of sand blasted, large grit, and acid-etched (SLA) surface-treated mini-implants (C-implants) used as the exclusive source of anchorage during en masse retraction.

MATERIALS AND METHODS

A retrospective clinical investigation was performed comparing pretreatment cone beam computed tomography (CBCT) images with those taken after en masse retraction of the six anterior teeth. Force was applied to 16 C-implants (1.8 mm in diameter, 8.5 mm in length) placed between the upper second premolars and first molars. Three-dimensional superimposition of CBCT data using mutual information was used to evaluate the positional difference of C-implants between preretraction and postretraction CBCT data.

RESULTS

There was no significant difference in mini-implant position between the preretraction and postretraction CBCT evaluation.

CONCLUSIONS

The SLA-coated C-implant provides stationary anchorage as well as stable anchorage during orthodontic tooth movement.

Assessment of the genetic risks of a metallic alloy used in medical implants

The use of artificial implants provides a palliative or permanent solution for individuals who have lost some bodily function through disease, an accident or natural wear. This functional loss can be compensated for by the use of medical devices produced from special biomaterials. Titanium alloy (Ti-6Al-4V) is a well-established primary metallic biomaterial for orthopedic implants, but the toxicity of the chemical components of this alloy has become an issue of concern. In this work, we used the MTT assay and micronucleus assay to examine the cytotoxicity and genotoxicity, respectively, of an extract obtained from this alloy. The MTT assay indicated that the mitochondrial activity and cell viability of CHO-K1 cells were unaffected by exposure to the extract. However, the micronucleus assay revealed DNA damage and an increase in micronucleus frequency at all of the concentrations tested. These results show that ions released from Ti-6Al-4V alloy can cause DNA and nuclear damage and reinforce the importance of assessing the safety of metallic medical devices constructed from biomaterials.