Synergistic interactions between corrosion and wear at titanium-based dental implant connections: A scoping review

Chronic exposure to TiO2 micro- and nano particles: A biochemical and histopathological experimental study

The aim of this work was to analyze the effects of long-term exposure to titanium dioxide (TiO2) micro- (MPs) and nanoparticles (NPs) (six and 12 months) on the biochemical and histopathological response of target organs using a murine model. Male Wistar rats were intraperitoneally injected with a suspension of TiO2 NPs (5 nm; TiO2-NP5 group) or MPs (45 μm; TiO2-NP5 group); the control group was injected with saline solution. Six and 12 months post-injection, titanium (Ti) concentration in plasma and target organs was determined spectrometrically (ICP-MS). Blood smears and organ tissue samples were evaluated by light microscopy. Liver and kidney function was evaluated using serum biochemical parameters. Oxidative metabolism was assessed 6 months post-injection (determination of superoxide anion by nitroblue tetrazolium (NBT) test, superoxide dismutase (SOD) and catalase (CAT), lipid peroxidation, and paraoxonase 1). Titanium (Ti) concentration in target organs and plasma was significantly higher in the TiO2-exposed groups than in the control group. Histological evaluation showed the presence of titanium-based particles in the target organs, which displayed no structural alterations, and in blood monocytes. Oxidative metabolism analysis showed that TiO2 NPs were more reactive over time than MPs (p < .05) and mobilization of antioxidant enzymes and membrane damage varied among the studied organs. Clearance of TiO2 micro and nanoparticles differed among the target organs, and lung clearance was more rapid than clearance from the lungs and kidneys (p < .05). Conversely, Ti concentration in plasma increased with time (p < .05). In conclusion, neither serum biochemical parameters nor oxidative metabolism markers appear to be useful as biomarkers of tissue damage in response to TiO2 micro- and nanoparticle deposits at chronic time points.

Longevity of different abutments placed on narrow diameter implants: Assessment of structural damage and loosening

OBJECTIVES

To evaluate structural damage and loosening of abutments placed on narrow diameter implants after cyclic fatigue.

METHODS

Sixty Morse taper narrow diameter implants (Neodent, Brazil) received two types of abutments (1PA- one-piece abutment or 2PA- two-piece abutment), which were randomly divided into 3 fatigue experiments (n = 10). The implants were placed into a customized supporting holder and a software-assisted digital torque wrench secured the manufacturer recommended torque for each abutment. Cone beam computed tomography (CBCT) scans were acquired, before and after fatigue, and post-processed (software e-Vol DX) to assess damage and abutment displacement. The boundary fatigue method was adapted to use 2 × 106 cycles, 2 Hz of frequency and constant peak load of 80 N (first experiment) that varied according to the failure rate of previous specimens (second and third experiments). Failure was evaluated using CBCT scans and removal torque values. Data were used to estimate long-term torque degradation, probability of failure and Weibull modulus (software ALTA PRO9).

RESULTS

All 2PA specimens became loosen independently of the applied fatigue load, and structural bending was observed in 14 abutments. Eight 1PA got loosen during the fatigue experiment. The Weibull analysis showed a lower modulus (m = 1.0; 0.7, 1.4) for 1PA than for 2PA (m = 2.6; 2, 3.4) resulting in longer predicted lifetimes and slower torque degradation for 1PA than for 2PA specimens.

SIGNIFICANCE

1PA showed greater long-term survival probability than 2PA. Predicting the lifetime and mechanical behavior of implant-abutment systems are useful information to clinicians during the decision-making process of oral rehabilitations.

Tribocorrosion of 3D printed dental implants: An overview

With the advancements in dental science and the growing need for improved dental health, it has become imperative to develop new implant materials which possess better geometrical, mechanical, and physical properties. The oral environment is a corrosive environment and the relative motion between the teeth also makes the environment more hostile. Therefore, the combined corrosion and tribology commonly known as tribocorrosion of implants needs to be studied. The complex shapes of the dental implants and the high-performance requirements of these implants make manufacturing difficult by conventional manufacturing processes. With the advent of additive manufacturing or 3D-printing, the development of implants has become easy. However, the various requirements such as surface roughness, mechanical strength, and corrosion resistance further make the manufacturing of implants difficult. The current paper reviews the various studies related to3D-printed implants. Also, the paper tries to highlight the role of 3D-Printing can play in the area of dental implants. Further studies both experimental and numerical are needed to devise optimized conditions for 3D-printing implants to develop implants with improved mechanical, corrosion, and biological properties.

Emerging factors affecting peri-implant bone metabolism

Implant dentistry has evolved to the point that standard implant osseointegration is predictable. This is attributed in part to the advancements in material sciences that have led toward improvements in implant surface technology and characteristics. Nonetheless, there remain several cases where implant therapy fails (specifically at early time points), most commonly attributed to factors affecting bone metabolism. Among these patients, smokers are known to have impaired bone metabolism and thus be subject to higher risks of early implant failure and/or late complications related to the stability of the peri-implant bone and mucosal tissues. Notably, however, emerging data have unveiled other critical factors affecting osseointegration, namely, those related to the metabolism of bone tissues. The aim of this review is to shed light on the effects of implant-related factors, like implant surface or titanium particle release; surgical-related factors, like osseodensification or implanted biomaterials; various drugs, like selective serotonin reuptake inhibitors, proton pump inhibitors, anti-hypertensives, nonsteroidal anti-inflammatory medication, and statins, and host-related factors, like smoking, diet, and metabolic syndrome on bone metabolism, and aseptic peri-implant bone loss. Despite the infectious nature of peri-implant biological complications, these factors must be surveyed for the effective prevention and management of peri-implantitis.

Wear at the implant-framework interface between titanium implant platform and the additively manufactured titanium and cobalt-chromium frameworks

PURPOSE

To measure the wear at the implant interface between the Grade 4 titanium (Ti) of the implant and frameworks fabricated using two additively manufactured alloys (Ti alloy and cobalt-chromium [Co-Cr]) pre- and post-artificial aging.

MATERIAL AND METHODS

Three-unit frameworks supported by two implants were additively manufactured (Atlantis; Dentsply Sirona) using Ti and Co-Cr dental alloys. Two implants (OsseoSpeed EV, Astra Tech; Dentsply Sirona) were torqued on each non-engaging framework. The assembled implant-frameworks were secured into polyurethane foam blocks. Groups were created based on the material and surface assessed: framework (Ti-framework and Co-Cr-framework groups) and implant (Ti-implant group). Two subgroups were created depending on the location: premolar (PM) and molar (M). Computed tomography images were obtained pre- (as manufactured) and post-simulated mastication procedures. The pre- and post-simulated mastication files of each specimen were aligned using the best-fit algorithm using a metrology program. Wear was measured by calculating the volumetric discrepancies at the implant interface on 64 measurement points per area analyzed. Three-way ANOVA and Tukey tests were used to analyze the data (α = 0.05).

RESULTS

The mean volumetric discrepancy values ranged from 0.8 to 3.1 µm among all the subgroups tested. The group (framework vs. implant) (p < 0.001) and tooth location (p < 0.001) were significant factors of the mean volumetric discrepancy values obtained. The framework group presented with significantly lower volumetric discrepancy mean values (1 µm) compared with the implant group (3 µm), whereas the premolar area obtained significantly lower mean volumetric discrepancy values (1.9 µm) compared with the molar location (2.3 µm).

CONCLUSIONS

Volumetric discrepancies were found at the implant-framework interface tested between the pre- and post-artificial aging measurements ranging from 1 to 3 µm after 1,200,000 cyclic loading that simulated approximately 12 months of function.

Titanium particles in peri-implantitis: distribution, pathogenesis and prospects

Peri-implantitis is one of the most important biological complications in the field of oral implantology. Identifying the causative factors of peri-implant inflammation and osteolysis is crucial for the disease's prevention and treatment. The underlying risk factors and detailed pathogenesis of peri-implantitis remain to be elucidated. Titanium-based implants as the most widely used implant inevitably release titanium particles into the surrounding tissue. Notably, the concentration of titanium particles increases significantly at peri-implantitis sites, suggesting titanium particles as a potential risk factor for the condition. Previous studies have indicated that titanium particles can induce peripheral osteolysis and foster the development of aseptic osteoarthritis in orthopedic joint replacement. However, it remains unconfirmed whether this phenomenon also triggers inflammation and bone resorption in peri-implant tissues. This review summarizes the distribution of titanium particles around the implant, the potential roles in peri-implantitis and the prevalent prevention strategies, which expects to provide new directions for the study of the pathogenesis and treatment of peri-implantitis.

Surface modification of titanium implants with Mg-containing coatings to promote osseointegration

Titanium (Ti) and Ti alloys are commonly used in dental implants, which have good biocompatibility, mechanical strength, processability, and corrosion resistance. However, the surface inertia of Ti implants leads to delayed integration of Ti and new bone, as well as problems such as aseptic loosening and inadequate osseointegration. Magnesium (Mg) ions can promote bone regeneration, and many studies have used Mg-containing materials to modify the Ti implant surface. This systematic review summarizes the methods, effects, and clinical applications of surface modification of Ti implants with Mg-containing coatings. Database collection was completed on Janury 1, 2023, and a total of 29 relevant studies were ultimately included. Mg can be compounded with different materials and coated to the surface of Ti implants using different methods. In vitro and in vivo experiments have shown that Mg-containing coatings promote cell adhesion and osteogenic differentiation. On the one hand, the surface roughness of implants increases with the addition of Mg-containing coatings, which is thought to have an impact on the osseointegration of the implant. On the other hand, Mg ions promote cell attachment through binding interactions between the integrin family and FAK-related signaling pathways. And Mg ions could induce osseointegration by activating PI3K, Notch, ERK/c-Fos, BMP-4-related signaling pathways and TRPM7 protein channels. Overall, Mg-based coatings show great potential for the surface modification of Ti implants to promote osseointegration. STATEMENT OF SIGNIFICANCE: The inertia surface of titanium (Ti) implants leads to delayed osseointegration. Magnesium (Mg) ions, known for promoting bone regeneration, have been extensively studied to modify the surface of Ti implants. However, no consensus has been reached on the appropriate processing methods, surface roughness and effective concentration of Mg-containing coatings for osseointegration. This systematic review focus on the surface modification of Ti implants with Mg-containing compounds, highlighting the effects of Mg-containing coatings on the surface properties of Ti implants and its associated mechanisms. Besides, we also provide an outlook on future directions to promote the clinical application of Mg-modified implants.

Fit and forget: The future of dental implant therapy via nanotechnology

Unlike orthopedic implants, dental implants require the orchestration of both osseointegration at the bone-implant interface and soft-tissue integration at the transmucosal region in a complex oral micro-environment with ubiquitous pathogenic bacteria. This represents a very challenging environment for early acceptance and long-term survival of dental implants, especially in compromised patient conditions, including aged, smoking and diabetic patients. Enabling advanced local therapy from the surface of titanium-based dental implants via novel nano-engineering strategies is emerging. This includes anodized nano-engineered implants eluting growth factors, antibiotics, therapeutic nanoparticles and biopolymers to achieve maximum localized therapeutic action. An important criterion is balancing bioactivity enhancement and therapy (like bactericidal efficacy) without causing cytotoxicity. Critical research gaps still need to be addressed to enable the clinical translation of these therapeutic dental implants. This review informs the latest developments, challenges and future directions in this domain to enable the successful fabrication of clinically-translatable therapeutic dental implants that would allow for long-term success, even in compromised patient conditions.

The Progress in Tribocorrosion Research (2010-21): Focused on the Orthopedics and Dental Implants

Tribocorrosion is an integration of two areas-tribology and corrosion. It can be defined as the material degradation caused by the combined effect of corrosion and tribological process at the material interfaces. Significant development has occurred in the field of tribocorrosion over the past years. This development is due to its applications in various fields, such as aerospace, marine, biomedical, and space. Focusing on biomedical applications, tribocorrosion finds its applications in the implants used in cardiovascular, spine, orthopedics, trauma, and dental areas. It was reported that around 7.2 million Americans are living with joint implants. Implant surgery is a traumatic and expensive procedure. Tribocorrosion can affect the lifespan of the implants, thus leading to implant failure and a potential cause of revision surgery. Hence, it is essential to understand how tribocorrosion works, its interaction with the implants, and what procedures can be implemented to protect materials from tribocorrosion. This paper discusses how tribocorrosion research has evolved over the past 11 years (2010-2021). This is a comprehensive overview of tribocorrosion research in biomedical applications.

Heat Accumulation-Induced Surface Structures at High Degrees of Laser Pulse Overlap on Ti6Al4V Surfaces by Femtosecond Laser Texturing

In this work, femtosecond laser pulses at high repetition rates were used to fabricate unique microstructures on the surface of Ti6Al4V. We investigated the influence of pulse overlap and laser repetition rates on structure formation. Laser texturing with a high degree of overlap resulted in melting of the material, leading to the formation of specific microstructures that can be used as cavities for drug delivery. The reason for melt formation is attributed to local heat accumulation at high repetition rates. Such structures can be fabricated on materials with low thermal conductivity, which prevent heat dissipation into the bulk of the material. The heat accumulation effect has also been demonstrated on steel, which also has low thermal conductivity.

Peri-implantitis after 40 years: Evidence, mechanisms, and implications: A mapping review

STATEMENT OF PROBLEM

The high prevalence of peri-implantitis (PI) continues to plague patients and the disease is resistant to present treatment regimens. An analysis of the available research is lacking.

PURPOSE

Given the abundance and diversity of research on the topic of PI, the purpose of this mapping review was to synthesize the literature on the prevention of PI, the histopathology of the disease, the state of present therapeutics, and any emerging treatments.

MATERIAL AND METHODS

An extensive literature search was undertaken by using the electronic databases of PubMed, Web of Science, and Science Direct. The keyword strings were peri-implantitis, dental implant, risk assessment, histopathology, prosthesis design, and treatment. The filters applied were time interval from 2000 to 2002; language, English.

RESULTS

A total of 3635 articles were taken from PubMed, 3686 articles from Web of Science, and 2450 articles from Science Direct. After applying the inclusion and exclusion criteria to the titles and abstracts of selected investigations, 214 studies were retrieved.

CONCLUSIONS

The evidence reflects a concerning incidence of PI, without a predictable treatment protocol. An in-depth patient risk assessment considering risk modification, emphasis on surgical and restorative expertise, and strict recall and maintenance is essential to minimize PI.

An efficient metal-organic framework-based drug delivery platform for synergistic antibacterial activity and osteogenesis

Bone implants for clinical application should be endowed with antibacterial activity, biocompatibility, and even osteogenesis-promoting properties. In this work, metal-organic framework (MOF) based drug delivery platform was used to modify titanium implants for improved clinical applicability. Methyl Vanillate@Zeolitic Imidazolate Framework-8 (MV@ZIF-8) was immobilized on the polydopamine (PDA) modified titanium. The sustainable release of the Zn²⁺ and MV causes substantial oxidative damage to Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The increased reactive oxygen species (ROS) significantly up-regulates the expression of oxidative stress and DNA damage response genes. Meanwhile, the structural disruption of lipid membranes caused by the ROS, the damage caused by Zinc active sites and the damage accelerated by the MV are both involved in inhibiting bacterial proliferation. The up-regulated expression of the osteogenic-related genes and proteins indicated that the MV@ZIF-8 could effectively promote the osteogenic differentiation of the human bone mesenchymal stem cells (hBMSCs). RNA sequencing and Western blotting analysis revealed that the MV@ZIF-8 coating activates the canonical Wnt/β-catenin signaling pathway through the regulation of tumor necrosis factor (TNF) pathway, thereby promoting the osteogenic differentiation of the hBMSCs. This work demonstrates a promising application of the MOF-based drug delivery platform in bone tissue engineering.

Abutment rotational freedom on five implant systems with different internal connections

STATEMENT OF PROBLEM

Information regarding the rotational freedom of internal connection implants is sparse.

PURPOSE

The purpose of this in vitro study was to compare the rotational freedom of different internal conical and internal nonconical connections.

MATERIAL AND METHODS

Thirty implants, 30 straight manufactured standard abutments, and 30 standard abutment screws were obtained for each of the 5 implant systems tested. Three implant systems had indexed internal conical connections with different antirotational geometries: hexagon (Naturall+), cam-groove (ID CAM M), and octagon (Bone Level). Two implant systems had internal nonconical connections with hexagonal antirotational geometry (Tapered Screw-Vent and Seven). The implants were mounted in a steel plate, and a metal reference arm was attached to the abutment. Before tightening the standard abutment screw, a modified torque wrench was used to rotate the abutment clockwise until reaching the clockwise rotational endpoint. This modified torque wrench was connected to the abutment's outer surface. It allowed free access to the standard abutment screw for a second torque wrench, specific to each implant system. The modified torque wrench applied a controlled torque of 5 Ncm, which held the abutment at the clockwise rotational endpoint. The standard abutment screw was then tightened to the manufacturer's specified torque value with the second torque wrench. Angle value corresponding to the clockwise endpoint was measured microscopically between a fixed reference point on the steel plate and the reference arm. The abutment was then unscrewed and removed. The same procedure was carried out to rotate the abutment counterclockwise and measure the angle value corresponding to the counterclockwise rotational endpoint. The rotational freedom was finally determined from the differences in the angles between the clockwise and counterclockwise rotational endpoints. Rotational freedom angle values were summarized as descriptive statistics (means, standard deviations). The normality test (Kolmogorov-Smirnov) was applied, and the Kruskal-Wallis test was performed. The Wilcoxon signed-rank test was used to isolate the implant system differences from each other (α=.05).

RESULTS

The lowest mean rotational freedom angles were obtained for Bone Level (conical connection, 0.17 degrees) and Tapered Screw-Vent (nonconical connection, 0.05 degrees). These systems were followed in increasing order by ID CAM M (conical connection, 0.50 degrees), Seven (nonconical connection, 1.98 degrees), and Naturall+ (conical connection, 2.49 degrees). Compared with each other, all implant systems had significant statistical differences in rotational freedom angles (P<.05).

CONCLUSIONS

Significant differences were found among the 5 implant systems. The lowest mean rotational freedom angles were obtained both with a conical connection (Bone Level) and a nonconical connection (Tapered Screw-Vent).

Physical and mechanical changes on titanium base of three different types of hybrid abutment after cyclic loading

PURPOSE

This study investigated the physical and mechanical changes in the titanium base of three different hybrid abutment materials after cyclic loading by estimating the post-load reverse torque value (RTV), compressive side fulcrum wear pattern of titanium base, and surface roughness.

MATERIALS AND METHODS

A total of 24 dental implants were divided into three groups (n = 8 each): Group Z, LD, and P used zirconia, lithium disilicate, and polyetheretherketone, respectively, for hybrid abutment fabrication. RTV was evaluated after cyclic loading with 50 N for 1.2 × 10⁶ chewing cycles. The compressive sides of the titanium bases were analyzed using a scanning electron microscope, and the roughness of the affected areas was measured using an optical profilometer after loading. Datasets were analyzed using Kruskal-Wallis test followed by Mann-Whitney tests with the Bonferroni correction (α = .05).

RESULTS

Twenty-three samples passed the test; one LD sample fractured after 770,474 cycles. Post-load RTV varied significantly depending on the hybrid-abutment material (P = .020). Group P had a significantly higher median of post-load RTVs than group Z (16.5 and 14.3 Ncm, respectively). Groups LD and P showed minor signs of wear, and group Z showed a more pronounced wear pattern. While evaluating compressive side affected area roughness of titanium bases, lower medians were shown in group LD (Ra 0.16 and Rq 0.22 µm) and group P (Ra 0.16 and Rq 0.23 µm) than in group Z (Ra 0.26 and Rq 0.34 µm); significant differences were found only among the unaffected surface and group Z.

CONCLUSION

The hybrid abutment material influences the post-load RTV. Group Z had a more pronounced wear pattern on the compressive side of titanium base; however, the surface roughness was not statistically different among the hybrid-abutment groups.

Docosahexaenoic Acid-Loaded Nanostructured Lipid Carriers for the Treatment of Peri-Implantitis in Rats

Being the most common cause of implant failure, peri-implantitis is defined as a pathological condition associated with the occurrence of peri-implant plaque, characterized by peri-implant mucosal inflammation and progressive loss of the supporting bone tissue attributed to the persistence of pro-inflammatory cytokines. Docosahexaenoic acid (DHA), which is a type of omega-3 polyunsaturated fatty acid, is generally used for the treatment of many inflammatory diseases. However, a suitable form for dosing and its therapeutic effect on peri-implantitis remain unclear. In this study, a novel nanostructured lipid carrier (NLC) loaded with squalene and DHA was fabricated (DHA-loaded NLC). The encapsulation efficiency and drug loading efficiency values of the DHA-loaded NLC were 78.13% ± 1.85% and 28.09% ± 0.48%, respectively. The release of DHA was gradual and steady until 144 h. In addition, the free-radical-scavenging rate of DHA-loaded NLC (0.57 ± 0.03) was much higher than that of sole DHA (0.17 ± 0.003). By inhibiting nuclear factor-κB p65 nuclear translocation, DHA-loaded NLC prevented the activation of nuclear factor-κB downstream inflammatory pathways and exerted anti-inflammatory effects on macrophages. Moreover, DHA-loaded NLC showed better effects on preventing alveolar bone resorption of rat peri-implantitis model than sole DHA. Hence, DHA-loaded NLC enhanced the anti-inflammatory bioavailability of DHA, offering a novel approach for the treatment of peri-implantitis.

Enhanced Corrosion Resistance and Local Therapy from Nano-Engineered Titanium Dental Implants

Titanium is the ideal material for fabricating dental implants with favorable biocompatibility and biomechanics. However, the chemical corrosions arising from interaction with the surrounding tissues and fluids in oral cavity can challenge the integrity of Ti implants and leach Ti ions/nanoparticles, thereby causing cytotoxicity. Various nanoscale surface modifications have been performed to augment the chemical and electrochemical stability of Ti-based dental implants, and this review discusses and details these advances. For instance, depositing nanowires/nanoparticles via alkali-heat treatment and plasma spraying results in the fabrication of a nanostructured layer to reduce chemical corrosion. Further, refining the grain size to nanoscale could enhance Ti implants' mechanical and chemical stability by alleviating the internal strain and establishing a uniform TiO₂ layer. More recently, electrochemical anodization (EA) has emerged as a promising method to fabricate controlled TiO₂ nanostructures on Ti dental implants. These anodized implants enhance Ti implants' corrosion resistance and bioactivity. A particular focus of this review is to highlight critical advances in anodized Ti implants with nanotubes/nanopores for local drug delivery of potent therapeutics to augment osseo- and soft-tissue integration. This review aims to improve the understanding of novel nano-engineered Ti dental implant modifications, focusing on anodized nanostructures to fabricate the next generation of therapeutic and corrosion-resistant dental implants. The review explores the latest developments, clinical translation challenges, and future directions to assist in developing the next generation of dental implants that will survive long-term in the complex corrosive oral microenvironment.

Ion release and local effects of titanium metal particles from dental implants: An experimental study in rats

BACKGROUND

The objective of this study was to evaluate the accumulation of ions in blood and organs caused by titanium (Ti) metal particles in a mandibular defect in rats, together with a description of the local reaction of oral tissues to this Ti alloy debris.

METHODS

Twenty Sprague-Dawley rats were randomly distributed into three groups: an experimental group with a mandibular bone defect filled with metallic debris obtained by implantoplasty; a positive control group; and a negative control group. Thirty days after surgery, the rats were euthanized and perilesional tissue surrounding the mandibular defect was removed, together with the lungs, spleen, liver, and brain. Two blood samples were collected: immediately before surgery and before euthanasia. The perilesional tissue was histologically analyzed using hematoxylin-eosin staining, and Ti, aluminum, and vanadium ion concentrations in blood and organs were measured by TQ-ICP-MS. Descriptive and bivariate analyses of the data were performed.

RESULTS

All rats with implanted metal debris showed metal particles and a bone fracture callus on the osseous defect. The metal particles were surrounded by a foreign body reaction characterized by the presence of histiocytes and multinucleated giant cells (MNGCs). The experimental group had a significant higher concentration of Ti ions in all studied organs except lung tissue (p < 0.05). In addition, there were more V ions in the brain in the experimental group (p = 0.008).

CONCLUSIONS

Although further studies are required to confirm the clinical relevance of these results, Ti metal particles in the jaw might increase the concentration of metal ions in vital organs and induce a foreign body reaction.

Regulatory assessment of nano-enabled health products in public health interest. Position of the scientific advisory board of the French National Agency for the Safety of Medicines and Health Products

Nanomaterials are present in a wide variety of health products, drugs and medical devices and their use is constantly increasing, varying in terms of diversity and quantity. The topic is vast because it covers nanodrugs, but also excipients (that includes varying proportions of NMs) and medical devices (with intended or not-intended (by-products of wear) nanoparticles). Although researchers in the field of nanomedicines in clinical research and industry push for clearer definitions and relevant regulations, the endeavor is challenging due to the enormous diversity of NMs in use and their specific properties. In addition, regulatory hurdles and discrepancies are often cited as obstacles to the clinical development of these innovative products. The scientific council of the Agence Nationale de Sécurité du Médicament et des produits de santé (ANSM) undertook a multidisciplinary analysis encompassing fundamental, environmental and societal dimensions with the aim of identifying topics of interest for regulatory assessment and surveillance. This analysis allowed for proposing some recommendations for approximation and harmonization of international regulatory practices for the assessment of the risk/benefit balance of these products, considering as well the public expectations as regards efficacy and safety of nanomaterials used in Health products, in terms of human and environmental health.

Osseointegration Properties of Titanium Implants Treated by Nonthermal Atmospheric-Pressure Nitrogen Plasma

Pure titanium is used in dental implants owing to its excellent biocompatibility and physical properties. However, the aging of the material during storage is detrimental to the long-term stability of the implant after implantation. Therefore, in this study, we attempted to improve the surface properties and circumvent the negative effects of material aging on titanium implants by using a portable handheld nonthermal plasma device capable of piezoelectric direct discharge to treat pure titanium discs with nitrogen gas. We evaluated the osteogenic properties of the treated samples by surface morphology and elemental analyses, as well as in vitro and in vivo experiments. The results showed that nonthermal atmospheric-pressure nitrogen plasma can improve the hydrophilicity of pure titanium without damaging its surface morphology while introducing nitrogen-containing functional groups, thereby promoting cell attachment, proliferation, and osseointegration to some extent. Therefore, nitrogen plasma treatment may be a promising method for the rapid surface treatment of titanium implants.

An update of interbody cages for spine fusion surgeries: from shape design to materials

INTRODUCTION

Discectomy and interbody fusion are widely used in the treatment of intervertebral disc-related diseases. Among them, the interbody cage plays a significant role. However, the complications related to the interbody cage, such as nonunion or pseudoarthrosis, subsidence, loosening, and prolapse of the cage, cannot be ignored. By changing the design and material of the interbody fusion cage, a better fusion effect can be obtained, the incidence of appeal complications can be reduced, and the quality of life of patients after interbody fusion can be improved.

AREAS COVERED

This study reviewed the research progress of cage design and material and discussed the methods of cage design and material to promote intervertebral fusion.

EXPERT OPINION

Current treatment of cervical and lumbar degenerative disease requires interbody fusion to maintain decompression and to promote fusion and reduce the incidence of fusion failure through improvements in implant material, design, internal structure, and function. However, interbody fusion is not an optimal solution for treating vertebral instability.Abbreviations: ACDF, Anterior cervical discectomy and fusion; ALIF, anterior lumbar interbody fusion; Axi-aLIF, axial lumbar interbody fusion; BAK fusion cage, Bagby and Kuslich fusion cage; CADR, cervical artificial disc replacement; DBM, decalcified bone matrix; HA, hydroxyapatite; LLIF/XLIF, lateral or extreme lateral interbody fusion; MIS-TLIF, minimally invasive transforaminal lumbar interbody fusion; OLIF/ATP, oblique lumbar interbody fusion/anterior to psoas; PEEK, Poly-ether-ether-ketone; PLIF, posterior lumbar interbody fusion; ROI-C, Zero-profile Anchored Spacer; ROM, range of motion; SLM, selective melting forming; TLIF, transforaminal lumbar interbody fusion or.

Improvement in osteogenesis, vascularization, and corrosion resistance of titanium with silicon-nitride doped micro-arc oxidation coatings

Titanium (Ti) implants have been widely used for the treatment of tooth loss due to their excellent biocompatibility and mechanical properties. However, modifying the biological properties of these implants to increase osteointegration remains a research challenge. Additionally, the continuous release of various metal ions in the oral microenvironment due to fluid corrosion can also lead to implant failure. Therefore, simultaneously improving the bioactivity and corrosion resistance of Ti-based materials is an urgent need. In recent decades, micro-arc oxidation (MAO) has been proposed as a surface modification technology to form a surface protective oxide layer and improve the comprehensive properties of Ti. The present study doped nano silicon nitride (Si₃N₄) particles into the Ti surface by MAO treatment to improve its corrosion resistance and provide excellent osteoinduction by enhancing alkaline phosphatase activity and osteogenic-related gene expression. In addition, due to the presence of silicon, the Si₃N₄-doped materials showed excellent angiogenesis properties, including the promotion of cell migration and tubule formation, which play essential roles in early recovery after implantation.

Preventing Peri-implantitis: The Quest for a Next Generation of Titanium Dental Implants

Titanium and its alloys are frequently the biomaterial of choice for dental implant applications. Although titanium dental implants have been utilized for decades, there are yet unresolved issues pertaining to implant failure. Dental implant failure can arise either through wear and fatigue of the implant itself or peri-implant disease and subsequent host inflammation. In the present report, we provide a comprehensive review of titanium and its alloys in the context of dental implant material, and how surface properties influence the rate of bacterial colonization and peri-implant disease. Details are provided on the various periodontal pathogens implicated in peri-implantitis, their adhesive behavior, and how this relationship is governed by the implant surface properties. Issues of osteointegration and immunomodulation are also discussed in relation to titanium dental implants. Some impediments in the commercial translation for a novel titanium-based dental implant from "bench to bedside" are discussed. Numerous in vitro studies on novel materials, processing techniques, and methodologies performed on dental implants have been highlighted. The present report review that comprehensively compares the in vitro, in vivo, and clinical studies of titanium and its alloys for dental implants.

Stability of implant-abutment connection in three different systems after fatigue test

Aim

Abutment screw loosening of implant-supported prosthesis causes a mismatch between the abutment and the implant. This screw loosening is influenced by the implant-abutment connection type, however, with contradictory results reported in different studies. The present study evaluates the stability of abutment-implant connections in three different systems before and after the fatigue test.

Settings and Design

Thirty implants (4.3 mm in diameter and 12 mm in length) were divided into three groups of 10: Implantium, Zimmer, and straight internal hexagonal connection (SIC) implants.

Materials and Methods

Two torques of 35 Ncm with an interval of 10 min were applied, followed by measuring removal torque value (RTV). The samples were re-torqued and then underwent a simulation of 1-year chewing clinical performance of dental implant under axial force of 400 N, with a frequency of 8 Hz (one million cycles). After fatigue test, the RTV was calculated and recorded.

Statistical Analysis

The mean RTVs obtained before and after cyclic load were analyzed by SPSS version 22 software using multivariate analysis.

Results

Significant differences in RTV and role of cyclic loading were found between SIC and Implantium groups (P = 0.006 and 0.021, respectively), as well as between Zimmer and SIC groups (P = 0.032 and 0.006, respectively), but not between Zimmer and Implantium groups (P = 0.771 and 0.248, respectively).

Conclusion

The type of connection could affect the screw loosening, the preload loss, and the implant component stability. SIC group revealed the highest RTVs before and after cyclic loading.

Analysis of the Microbiome on the Surface of Corroded Titanium Dental Implants in Patients with Periimplantitis and Diode Laser Irradiation as an Aid in the Implant Prosthetic Treatment: An Ex Vivo Study

The paper presents the optimization of diode laser irradiation of corroded dental implants in order to reduce the number of microorganisms associated peri-implantitis. The research included the identification of microorganisms on the surface of removed dental implants in patients with peri-implantitis and the assessment of the biocidal effectiveness of the diode laser against these microorganisms. Laser desorption/mass spectrometry (MALDI-TOF MS) was used to identify microorganisms and metagens were examined by next generation sequencing (NGS). Irradiation was performed with a diode laser with a wavelength of λ = 810, operating mode: 25 W/15.000 Hz/10 μs, average = 3.84 W with the number of repetitions t = 2 × 15 s and t = 3 × 15 s. The structure and surface roughness of the implants were analysed before and after laser irradiation by optical profilometry and optical microscopy with confocal fixation. In total, 16 species of Gram-positive bacteria and 23 species of Gram-negative bacteria were identified on the surface of the implants. A total of 25 species of anaerobic bacteria and 12 species with corrosive potential were detected. After diode laser irradiation, the reduction in bacteria on the implants ranged from 88.85% to 100%, and the reduction in fungi from 87.75% to 96.77%. The reduction in microorganisms in the abutment was greater than in the endosseous fixture. The applied laser doses did not damage, but only cleaned the surface of the titanium implants. After 8 years of embedding, the removed titanium implant showed greater roughness than the 25-year-old implant, which was not exposed to direct influence of the oral cavity environment. The use of a diode laser in an optimised irradiation dose safely reduces the number of microorganisms identified on corroded dental implants in patients with peri-implantitis.

Diagnostic tests for titanium hypersensitivity in implant dentistry: a systematic review of the literature

PURPOSE

There are rising concerns about titanium hypersensitivity reaction regarding dental endosseous implants. This review aims to summarize and compare the validity and reliability of the available dermatological and laboratory diagnostic tests regarding titanium hypersensitivity. The following PICO design was used: In Patients with titanium dental implants (P) does epicutaneous testing (ECT) (I), compared to lymphocyte transformation test (LTT) or Memory Lymphocyte Immunostimulation Assay (MELISA) (C) detect hypersensitivity reactions (O)? A literature search was performed including all studies dealing with this topic. Studies regarding orthopedic implants were excluded.

METHODS

Three databases (MEDLINE PubMed, Cochrane Library, SciELO) were screened for suitable studies and an additional manual search was also performed. Literature regarding hypersensitivity reactions in orthopedic implants, hypersensitivity reactions regarding implants not related to dental or maxillofacial surgery, animal studies and in vitro studies were excluded. A quality assessment of all selected full-text articles was performed. Randomized, controlled trials were evaluated with the Cochrane Risk of Bias Tool I. Cohort studies were assessed according to the New Castle-Ottawa Scale and case series according to Moga et al. (Development of a quality appraisal tool for case series studies using a modified Delphi technique. 2012).

RESULTS

10 studies were included in the quantitative synthesis and available for the endpoint diagnostics of intolerance reactions to titanium dental implants: 2 clinical studies, 7 cohort studies and 1 case series. The potential for bias (internal validity) for these studies was overall rated as high.

CONCLUSIONS

The study of the available literature regarding ECT and MELISA or LTT in patients with suspected titanium hypersensitivity showed inconsistent results in terms of reliability and validity and thus, those tests should be regarded cautiously. There is strong evidence that titanium hypersensitivity in dental implants is associated with innate immunity: unspecific pro-inflammatory responses due to particle induced hyperreactivity of macrophages or toxicological responses especially towards nanoparticles rather than activation of the adaptive immune system. Therefore, tests detecting allergies do not seem expedient and inflammatory clinical signs should be regarded as leading parameters.

Impurities in commercial titanium dental implants - A mass and optical emission spectrometry elemental analysis

OBJECTIVE

Titanium (Ti) is considered bioinert and is still regarded as the "gold standard" material for dental implants. However, even 'commercial pure' Ti will contain minor fractions of elemental impurities. Evidence demonstrating the release of Ti ions and particles from 'passive' implant surfaces is increasing and has been attributed to biocorrosion processes which may provoke immunological reactions. However, Ti observed in peri-implant tissues has been shown to be co-located with elements considered impurities in biomedical alloys. Accordingly, this study aimed to quantify the composition of impurities in commercial Ti dental implants.

METHODS

Fifteen commercial titanium dental implant systems were analyzed using inductively coupled plasma-mass spectrometry (ICP-MS) and optical emission spectrometry (ICP-OES).

RESULTS

The elemental composition of implants manufactured from commercially pure grades of Ti, Ti-6Al-4V, and the TiZr alloy (Roxolid) conformed to the respective ISO/ASTM standards or manufacturers´ data (TiZr/Roxolid). However, all implants investigated included exogenous metal contaminants including Ni, Cr, Sb, and Nb to a variable extent. Other contaminants detected in a fraction of implants included As and the radionuclides U-238 and Th-232.

SIGNIFICANCE

Although all Ti implant studies conformed with their standard compositions, potentially allergenic, noxious metals and even radionuclides were detected. Since there are differences in the degree of contamination between the implant systems, a certain impurity fraction seems technically avoidable. The clinical relevance of these findings must be further investigated, and an adaptation of industry standards should be discussed.

Comprehensive Review on the Degradation Chemistry and Toxicity Studies of Functional Materials

In recent decades there has been growing interest of material chemists in the successful development of functional materials for drug delivery, tissue engineering, imaging, diagnosis, theranostic, and other biomedical applications with advanced nanotechnology tools. The efficacy and safety of functional materials are determined by their pharmacological, toxicological, and immunogenic effects. It is essential to consider all degradation pathways of functional materials and to assess plausible intermediates and final products for quality control. This review provides a brief insight into chemical degradation mechanisms of functional materials like oxidation, photodegradation, and physical and enzymatic degradation. The intermediates and products of degradation were confirmed with analytical methods such as proton nuclear magnetic resonance (¹H NMR), gel permeation chromatography (GPC), UV-vis spectroscopy (UV-vis), infrared spectroscopy (IR), differential scanning calorimetry (DSC), mass spectroscopy, and other sophisticated analytical methods. These analytical methods are also used for regulatory, quality control, and stability purposes in industry. The assessment of degradation is important to predetermine the behavior of functional materials in specific storage conditions and can be relevant to their behavior during in vivo applications. Another important aspect is the evaluation of the toxicity of functional materials. Toxicity can be accessed with various methods using in vitro, in vivo, ex vivo, and in silico models. In vitro cell culture methods are used to determine mitochondrial damage, reactive oxygen species, stress responses, and cellular toxicity. In vitro cellular toxicity can be measured by MTT assay, LDH leakage assay, and hemolysis. In vivo studies are performed using various animal models involving zebrafish, rodents (mice and rats), and nonhuman primates. Ex vivo studies are also used for efficacy and toxicity determinations of functional materials like ex vivo potency assay and precision-cut liver slice (PCLS) models. The in silico tools with computational simulations like quantitative structure-activity relationships (QSAR), pharmacokinetics (PK) and pharmacodynamics (PD), dose and time response, and quantitative cationic-activity relationships ((Q)CARs) are used for prediction of the toxicity of functional materials. In this review, we studied the principle methods used for degradation studies, different degradation pathways, and mechanisms of functional material degradation with prototype examples. We discuss toxicity assessments with different toxicity approaches used for estimation of the safety and efficacy of functional materials.

Effects of titanium dioxide microparticles and nanoparticles on cytoskeletal organization, cell adhesion, migration, and proliferation in human gingival fibroblasts in the presence of lipopolysaccharide

BACKGROUND AND OBJECTIVE

Titanium wear particles may participate in the etiology of peri-implantitis. However, the influence of titanium wear particles on biological behavior of human gingival fibroblasts (HGFs) in the presence of LPS is still not clear. The present study demonstrated the effects of titanium dioxide micro- and nanoparticles (TiO₂  MPs and NPs) on HGF cell viability, cytoskeletal organization, adhesion, migration, and proliferation in vitro, and LPS was used to mimic the in vivo condition.

METHODS

Primary HGFs were treated with TiO₂ MPs (primary particle size <5 μm, 0.1 mg/ml) and NPs (primary particle size <100 nm, 0.1 mg/ml) with or without 1 μg/ml LPS. The effects of TiO₂ MPs and NPs on HGFs cell viability was measured by CCK-8 assay. The proliferation of HGF was detected by Ki67 nuclear staining. The confocal laser scanning microscope (CLSM) was used to detect the internalization of TiO₂ MPs and NPs in HGFs as well as the arrangement of F-actin, vinculin, and vimentin organization. Wound healing assay and transwell assay were performed to measure the migration of HGFs induced by TiO₂ MPs and NPs. Cell adhesion was measured using fibronectin-coated plates. The relative mRNA and protein expression of adhesion relative protein such as focal adhesion kinase (FAK), fibronectin (FN), and type I collagen (COL1) were measured using quantitative RT-PCR and western blot analysis. One-way analysis of variance (ANOVA) and Student's t-test were used to analyze the statistical significance, and p < .05 was considered statistically significant.

RESULTS

TiO₂ NPs significantly inhibited HGF cell viability, proliferation, and migration compared with TiO₂ MPs group and control group. Compared with control group (2.64 ± 0.09), the mean absorbance of the cells in 1 mg/ml TiO₂ MPs group and 0.25 mg/ml TiO₂ NPs group were significantly decreased to 1.93 ± 0.33 (p < .05) and 2.22 ± 0.18 (p < .01), respectively. The cytoskeleton disruption was found in TiO₂ NPs group. The mRNA and protein expression were significantly downregulated by TiO₂ NPs. Furthermore, both TiO₂ NPs and MPs induced more adverse effects on HGFs in the presence of LPS.

CONCLUSION

Our results indicate that TiO₂ NPs but not TiO₂ MPs significantly disrupt the cytoskeletal organization and inhibited cell adhesion, migration, and proliferation of HGFs. However, in the presence of LPS, TiO₂ MPs, and TiO₂ NPs enhance these negative effects in HGFs. Titanium wear particles are probably involved in the initiation and progression of peri-implant diseases.

Electrochemical Corrosion of Titanium and Titanium Alloys Anodized in H2SO4 and H3PO4 Solutions

Titanium and its alloys have superior electrochemical properties compared to other alloy systems due to the formation of a protective TiO2 film on metal surfaces. The ability to generate the protective oxide layer will depend upon the type of alloy to be used. The aim of this work was to characterize the electrochemical corrosion behavior of titanium Ti-CP2 and alloys Ti-6Al-2Sn-4Zr-2Mo, Ti-6Al-4V, and Ti Beta-C. Samples were anodized in 1 M H2SO4 and H3PO4 solutions with a current density of 0.025 A/cm2. Electrochemical tests on anodized alloys were carried out using a three-electrode cell and exposed in two electrolytes, i.e., 3.5 wt % NaCl and 3.5 wt % H2SO4 solutions at room temperature. Scanning electron microscopy (SEM) was used to observe the morphology of anodized surfaces. The electrochemical techniques used were cyclic potentiodynamic polarization (CPP) and electrochemical noise (EN), based on the ASTM-G61 and G199 standards. Regarding EN, two methods of data analysis were used: the frequency domain (power spectral density, PSD) and time-frequency domain (discrete wavelet transform). For non-anodized alloys, the results by CCP and EN indicate icorr values of ×10−6 A/cm2. However, under anodizing conditions, the icorr values vary from ×10−7 to ×10−9 A/cm2. The PSD Ψ0 values are higher for non-anodized alloys, while in anodized conditions, the values range from −138/−122 dBi (A2·Hz−1)1/2 to −131/−180 dBi (A2·Hz−1)1/2. Furthermore, the results indicated that the alloys anodized in the H3PO4 bath showed an electrochemical behavior that can be associated with a more homogeneous passive layer when exposed to the 3.5 wt % NaCl electrolyte. Alloys containing more beta-phase stabilizers formed a less homogeneous anodized layer. These alloys are widely used in aeronautical applications; thus, it is essential that these alloys have excellent corrosion performance in chloride and acid rain environments.

Pyroptosis-Mediated Periodontal Disease

Pyroptosis is a caspase-dependent process relevant to the understanding of beneficial host responses and medical conditions for which inflammation is central to the pathophysiology of the disease. Pyroptosis has been recently suggested as one of the pathways of exacerbated inflammation of periodontal tissues. Hence, this focused review aims to discuss pyroptosis as a pathological mechanism in the cause of periodontitis. The included articles presented similarities regarding methods, type of cells applied, and cell stimulation, as the outcomes also point to the same direction considering the cellular events. The collected data indicate that virulence factors present in the diseased periodontal tissues initiate the inflammasome route of tissue destruction with caspase activation, cleavage of gasdermin D, and secretion of interleukins IL-1β and IL-18. Consequently, removing periopathogens’ virulence factors that trigger pyroptosis is a potential strategy to combat periodontal disease and regain tissue homeostasis.

Corrosion of titanium under simulated inflammation conditions: clinical context and in vitro investigations

Titanium and alloys thereof are widely utilized for biomedical applications in the fields of orthopedics and dentistry. The corrosion resistance and perceived biocompatibility of such materials are essentially related to the presence of a thin passive oxide layer on the surface. However, during inflammation phases, the immune system and its leukocytic cells generate highly aggressive molecules, such as hydrogen peroxide and radicals, that can significantly alter the passive film resulting in the degradation of the titanium implants. In combination with mechanical factors, this can lead to the release of metal ions, nanoparticles or microscaled debris in the surrounding tissues (which may sustain chronic inflammation), bring about relevant health issues and contribute to implant loss or failure. After briefly presenting the context of inflammation, this review article analyses the state-of-the-art knowledge of the in vitro corrosion of titanium, titanium alloys and coated titanium by reactive oxygen species and by living cells with an emphasis on electrochemical and microstructural aspects. STATEMENT OF SIGNIFICANCE: Inflammation involves the production of reactive oxygen species that are known to alter the passive layer protecting titanium implants against the aggressive environment of the human body. Inflammatory processes therefore contribute to the deterioration of biomedical devices. Although review articles on biomaterials for implant applications are regularly published in the literature, none has ever focused specifically on the topic of inflammation. After briefly recalling the clinical context, this review analyses the in vitro studies on titanium corrosion under simulated inflammation conditions from the pioneer works of the 80s and the 90s till the most recent investigations. It reports about the status of this research area for a multidisciplinary readership covering the fields of materials science, corrosion and implantology.

Comparison of Corrosion Products From Implant and Various Gold-Based Abutment Couplings: The Effect of Gold Plating

This study compared titanium (Ti), palladium (Pd), platinum (Pt), and gold (Au) ion release following induced accelerated tribocorrosion from three Au alloy abutment groups coupled with Ti implants over time; investigated contacting surface structural changes; and explored the effect of Au plating. Three abutment groups, G (n = 8, GoldAdapt, Nobel Biocare), N (n = 8, cast UCLA, Biomet3i), and P (n = 8, cast UCLA, Biomet3i, Au plated), coupled with implants (Nobel Biocare), immersed in 1% lactic acid, were cyclically loaded. Ions released (ppb) at T1, T2, and T3, simulating 3, 5, and 12 months of function, respectively, were quantified by inductively coupled plasma mass spectrometry (ICP-MS) and compared. Surface degradation and fretted particle composition after T3 were evaluated with scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX). ICP-MS data were nonparametric, expressed as medians and interquartile ranges. SEM/EDX showed pitting, crevice corrosion, and fretted particles on the components. Released ion concentrations in all groups across time significantly decreased for Pd (P < .001, median range: 1.70-0.09), Pt (P = .021, 0.55-0.00), and Au (P < .001, 1.01-0.00) and increased for Ti (P = .018, 2.49-5.84). Total Ti release was greater than other ions combined for G (P = .012, 9.86-2.30) and N (P < .001, 13.59-5.70) but not for P (P = .141, 8.21-3.53). Total Ti release did not differ between groups (P = .36) but was less variable across group P. On average, total ion release was 13.77 ppb (interquartile range 8.91-26.03 ppb) across the 12-month simulation. Tribocorrosion of Ti implants coupled with Au abutments in a simulated environment was evidenced by fretted particles, pitting, and crevice corrosion of the coupling surfaces and release of ions. More Ti was released compared with Pd, Pt, and Au and continued to increase with time. Abutment composition influenced ion release. Au-plated abutments appeared to subdue variation in and minimize high-concentration spikes of titanium.

In Vitro Corrosion of SiC-Coated Anodized Ti Nano-Tubular Surfaces

Peri-implantitis leads to implant failure and decreases long-term survival and success rates of implant-supported prostheses. The pathogenesis of this disease is complex but implant corrosion is believed to be one of the many factors which contributes to progression of this disease. A nanostructured titanium dioxide layer was introduced using anodization to improve the functionality of dental implants. In the present study, we evaluated the corrosion performance of silicon carbide (SiC) on anodized titanium dioxide nanotubes (ATO) using plasma-enhanced chemical vapor deposition (PECVD). This was investigated through a potentiodynamic polarization test and bacterial incubation for 30 days. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze surface morphologies of non-coated and SiC-coated nanotubes. Energy dispersive X-ray (EDX) was used to analyze the surface composition. In conclusion, SiC-coated ATO exhibited improved corrosion resistance and holds promise as an implant coating material.

Research to Clinics: Clinical Translation Considerations for Anodized Nano-Engineered Titanium Implants

Titania nanotubes (TNTs) fabricated on titanium orthopedic and dental implants have shown significant potential in "proof of concept" in vitro, ex vivo, and short-term in vivo studies. However, most studies do not focus on a clear direction for future research towards clinical translation, and there exists a knowledge gap in identifying key research challenges that must be addressed to progress to the clinical setting. This review focuses on such challenges with respect to anodized titanium implants modified with TNTs, including optimized fabrication on clinically utilized microrough surfaces, clinically relevant bioactivity assessments, and controlled/tailored local release of therapeutics. Further, long-term in vivo investigations in compromised animal models under loading conditions are needed. We also discuss and detail challenges and progress related to the mechanical stability of TNT-based implants, corrosion resistance/electrochemical stability, optimized cleaning/sterilization, packaging/aging, and nanotoxicity concerns. This extensive, clinical translation focused review of TNTs modified Ti implants aims to foster improved understanding of key research gaps and advances, informing future research in this domain.

Biomechanical behavior of functionally graded S53P4 bioglass-zirconia dental implants: Experimental and finite element analyses

OBJECTIVES

The aim of this work was to evaluate the biomechanical behavior of one-piece zirconia implants with a functionally graded bioglass (BG) layer as compared to monolithic zirconia and BG-coated implants, using the finite element method (FEM).

METHODS

Zirconia disks were infiltrated with bioglass S53P4 and then morphologically inspected by scanning electron microscopy (SEM) followed by mechanical analyses on micro-indentation tests for further biomechanical validation using the finite element method (FEM). On modeling, zirconia dental implants anchored into mandibular bone were simulated on occlusal loading as recorded under mastication. Three types of implants were simulated: i) free of BG coating, ii) with 100 μm or 150 μm thick conventional BG coatings; and iii) with graded BG coatings involving 3 different chemical composition distributions. The stress state at both implant and bone were evaluated using the FEM. The mechanically-induced bone remodelling was analyzed through the bone strain results.

RESULTS

Infiltration of BG into a zirconia structure resulted in a ∼100 μm thick layer with an exponential-like gradation of chemical composition and properties. Regarding the FEM calculations, the BG coating induced up to 30% decrease on stress in the implant body when compared to the monolithic zirconia implant. The gradient of chemical composition also improved the stresses' distribution. The stresses distribution towards the BG-coatings were significantly high and could lead to failure. Stresses on the bone were recorded down to its strength threshold, with insignificant influence of the coating layer. The bone strain values on all models indicates further bone remodelling although BG-coated and BG-graded zirconia implants showed the highest strain magnitude that may enhance the mechanical stimulation for bone maintenance.

SIGNIFICANCE

Graded BG-zirconia dental implants showed enhanced overall biomechanical behaviour as compared to the BG-coated or monolithic zirconia dental implants. Also, such biomechanical improvements noticed for the BG-graded system should be considered in combination with the well-known osseointegration benefits of bioactive glasses.

Passive Layers and Corrosion Resistance of Biomedical Ti-6Al-4V and β-Ti Alloys

The high specific strength, good corrosion resistance, and great biocompatibility make titanium and its alloys the ideal materials for biomedical metallic implants. Ti-6Al-4V alloy is the most employed in practical biomedical applications because of the excellent combination of strength, fracture toughness, and corrosion resistance. However, recent studies have demonstrated some limits in biocompatibility due to the presence of toxic Al and V. Consequently, scientific literature has reported novel biomedical β-Ti alloys containing biocompatible β-stabilizers (such as Mo, Ta, and Zr) studying the possibility to obtain similar performances to the Ti-6Al-4V alloys. The aim of this review is to highlight the corrosion resistance of the passive layers on biomedical Ti-6Al-4V and β-type Ti alloys in the human body environment by reviewing relevant literature research contributions. The discussion is focused on all those factors that influence the performance of the passive layer at the surface of the alloy subjected to electrochemical corrosion, among which the alloy composition, the method selected to grow the oxide coating, and the physicochemical conditions of the body fluid are the most significant.

Impact of exogenous metal ions on peri-implant bone metabolism: a review

The development of effective methods to promote the osseointegration of dental implants by surface modification is an area of intense research in dental materials science. Exogenous metal ions present in the implant and surface modifications are closely related to the bone metabolism around the implant. In the complex oral microenvironment, the release of metal ions caused by continuous corrosion of dental implants has an unfavorable impact on the surrounding tissue, and then affects osseointegration, leading to bad results such as loosening and falling off in the late stage of the implant. Besides, these ions can even be distributed in distant tissues and organs. Currently, surface modification techniques are being developed that involve different processing technologies including the introduction of exogenous metal ions with different properties onto the surface of implants to improve performance. However, most metal elements have some level of biological toxicity and can only be used within a safe concentration range to exert the optimum biological effects on recipients. In this paper, we review the adverse effects of metal ions on osseointegration and highlight the emerging applications for metal elements in improving the performance of dental implants.

Cytotoxic effects of submicron- and nano-scale titanium debris released from dental implants: an integrative review

OBJECTIVE

This integrative review aimed to report the toxic effect of submicron and nano-scale commercially pure titanium (cp Ti) debris on cells of peri-implant tissues.

MATERIALS AND METHODS

A systematic search was carried out on the PubMed electronic platform using the following key terms: Ti "OR" titanium "AND" dental implants "AND" nanoparticles "OR" nano-scale debris "OR" nanometric debris "AND" osteoblasts "OR "cytotoxicity" OR "macrophage" OR "mutagenic" OR "peri-implantitis". The inclusion criteria involved articles published in the English language, until December 26, 2020, reporting the effect of nano-scale titanium particles as released from dental implants on the toxicity and damage of osteoblasts.

RESULTS

Of 258 articles identified, 14 articles were selected for this integrative review. Submicron and nano-scale cp Ti particles altered the behavior of cells in culture medium. An inflammatory response was triggered by macrophages, fibroblasts, osteoblasts, mesenchymal cells, and odontoblasts as indicated by the detection of several inflammatory mediators such as IL-6, IL-1β, TNF-α, and PGE2. The formation of a bioactive complex composed of calcium and phosphorus on titanium nanoparticles allowed their binding to proteins leading to the cell internalization phenomenon. The nanoparticles induced mutagenic and carcinogenic effects into the cells.

CONCLUSIONS

The cytotoxic effect of debris released from dental implants depends on the size, concentration, and chemical composition of the particles. A high concentration of particles on nanometric scale intensifies the inflammatory responses with mutagenic potential of the surrounding cells.

CLINICAL RELEVANCE

Titanium ions and debris have been detected in peri-implant tissues with different size, concentration, and forms. The presence of metallic debris at peri-implant tissues also stimulates the migration of immune cells and inflammatory reactions. Cp Ti and TiO₂ micro- and nano-scale particles can reach the bloodstream, accumulating in lungs, liver, spleen, and bone marrow.

Titanium Wear of Dental Implants from Placement, under Loading and Maintenance Protocols

The objective of this review was to analyze the process of wear of implants leading to the shedding of titanium particles into the peri-implant hard and soft tissues. Titanium is considered highly biocompatible with low corrosion and toxicity, but recent studies indicate that this understanding may be misleading as the properties of the material change drastically when titanium nanoparticles (NPs) are shed from implant surfaces. These NPs are immunogenic and are associated with a macrophage-mediated inflammatory response by the host. The literature discussed in this review indicates that titanium NPs may be shed from implant surfaces at the time of implant placement, under loading conditions, and during implant maintenance procedures. We also discuss the significance of the micro-gap at the implant-abutment interface and the effect of size of the titanium particles on their toxicology. These findings are significant as the titanium particles can have adverse effects on local soft and hard tissues surrounding implants, implant health and prognosis, and even the health of systemic tissues and organs.

Ion Release from Dental Implants, Prosthetic Abutments and Crowns under Physiological and Acidic Conditions

Ion release from dental implants and prosthetic restoration can affect osteointegration and implant viability over a long period of time. Therefore, the aim of this study was to study the ion release from implants and crowns, with and without intermediate anodized abutments, in two different media, simulating clinical conditions. The implants, intermediate prosthetic abutments and Cr–Co crowns were divided into two groups depending on the media: Hanks’ solution and 1% lactic acid, simulating body fluids and microbiologically conditioned fluids, respectively. The study followed the ISO 10271:2011 and 10993-15:2000 standards modified to simulate the replacement of fluids in the oral environment. The ions’ release was measured by inductively coupled plasma mass spectroscopy (ICP-EOS), and only aluminum, chromium, cobalt, titanium and vanadium were identified. Ion concentration was higher in lactic acid than in Hanks’ solution at all time points (p < 0.05). Only vanadium showed a very low ion release in lactic acid, with no statistically significant differences from the ion release in Hanks’ solution (p = 0.524). Both anodized abutments and the immersion medium influenced the release of ions and affected the corrosion of these structures. The presence of an intermediate anodized abutment also affected ion release, as the level of ions was lower in groups with this component.

Modulation of immune-inflammatory responses through surface modifications of biomaterials to promote bone healing and regeneration

Control of inflammation is indispensable for optimal oral wound healing and tissue regeneration. Several biomaterials have been used to enhance the regenerative outcomes; however, the biomaterial implantation can ensure an immune-inflammatory response. The interface between the cells and the biomaterial surface plays a critical role in determining the success of soft and hard tissue regeneration. The initial inflammatory response upon biomaterial implantation helps in tissue repair and regeneration, however, persistant inflammation impairs the wound healing response. The cells interact with the biomaterials through extracellular matrix proteins leading to protein adsorption followed by recruitment, attachment, migration, and proliferation of several immune-inflammatory cells. Physical nanotopography of biomaterials, such as surface proteins, roughness, and porosity, is crucial for driving cellular attachment and migration. Similarly, modification of scaffold surface chemistry by adapting hydrophilicity, surface charge, surface coatings, can down-regulate the initiation of pro-inflammatory cascades. Besides, functionalization of scaffold surfaces with active biological molecules can down-regulate pro-inflammatory and pro-resorptive mediators' release as well as actively up-regulate anti-inflammatory markers. This review encompasses various strategies for the optimization of physical, chemical, and biological properties of biomaterial and the underlying mechanisms to modulate the immune-inflammatory response, thereby, promoting the tissue integration and subsequent soft and hard tissue regeneration potential of the administered biomaterial.

Remnant oral biofilm and microorganisms after autoclaving sterilization of retrieved healing abutments

OBJECTIVE

The purpose of this study was to evaluate the sterilization effectiveness against biofilms on retrieved healing abutments used in implant dentistry.

BACKGROUND

A large number of clinicians reuse healing abutments to decrease treatment costs although it can promote infection due to the presence of remnant biofilm biomass.

METHODS

One hundred and eighty-five titanium healing abutments previously used for 3 months in oral cavity were assessed in this study. Abutments were submitted to cleaning, chemical disinfection, and autoclave sterilization according to clinical guidelines. The abutments were aseptically placed into glass tubes containing specific bacterial growth medium and then incubated for 10 days. From glass tubes with bacterial growth, 100 µl medium was transferred to Schaedler's agar for morphological identification and counting of strict anaerobes and to Columbia blood agar for presumptive identification of facultative anaerobes after incubation. Isolated strains were then identified at species level by enzymatic and biochemical tests within API microorganism detection platform. Also, polymerase chain reaction (PCR) was performed for identification of undefined strains.

RESULTS

After the standard cleaning and sterilization procedures, fifty-six (approximately 30%) retrieved abutments showed the presence of remnant biofilm biomass. The bacteria identified into the remnant biofilms covering the abutments were representative of the commensal oral microbiota including Aggregatibacter actinomycetemcomitans, Prevotella intermedia, and Enterococcus faecalis.

CONCLUSION

Although some healing abutments did not reveal the existence of bacteria, organic components from biofilm biomass are still strongly adhered on the retentive micro-regions and surfaces of abutments and therefore that would support the accumulation of biofilm including pathogenic species leading to patients' cross-infections. Further studies should be performed on the assessment of different materials, design, and connections of the healing abutments associated with clinical disinfection procedures in implant dentistry.

Osteoclast-mediated biocorrosion of pure titanium in an inflammatory microenvironment

Titanium (Ti) and alloys thereof are commonly utilized in biomedical settings owing to their desirable mechanical properties and good biocompatibility. However, when exposed to biological systems for extended periods of time, Ti still undergoes corrosion. In the present study, we therefore explore the impact of osteoclasts (OC) on the surface characteristics and corrosion of commercially pure Titanium (cpTi) in the context of lipopolysaccharide (LPS)-induced inflammation. We utilized tartrate resistant acidic phosphatase (TRAP) and fluorescence staining to assess OC properties, while scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), optical profilometer, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization tests, and inductively coupled plasma atomic emission spectrometry (ICP-AES) were used to evaluate metal microstructure, surface composition and roughness, electrochemical corrosion properties, and metal ion release. SEM findings demonstrated that the surface of cpTi exhibited micro-pitting as well as the presence of viable OCs. Correspondingly, cpTi that had been exposed to OCs exhibited reduced levels of Ti, oxygen, and oxides within the corroded regions relative to smooth Ti as measured via EDS and XPS. OC exposure was also associated with significant changes in cpTi surface roughness, a significant decrease in corrosion resistance, and a significant increase in the release of Ti ions into the surrounding medium. In summary, these findings indicate that OC culture on the surface of cpTi can directly corrode titanium and lead to the release of Ti ions.

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.

Immunohistological composition of peri-implantitis affected tissue around ceramic implants-A pilot study

BACKGROUND

Aim of the pilot study was the histologic classification of the inflamed peri-implant soft tissue around ceramic implants (CI) in comparison with titanium implants (TI).

METHODS

Peri-implant tissue were retrieved from 15 patients (aged 34 to 88 years, seven males/eight females) with severe peri-implantitis (eight CI, seven TI). The peri-implant soft tissue samples were retrieved from the sites during scheduled removal of the implant and prepared for immunohistochemical analysis. Monoclonal antibodies (targeting CD3, CD20, CD138, and CD68) were used to identify T- and B-cells, plasma cells and macrophages. Quantitative assessment was performed by one histologically trained investigator. Linear mixed regression models were used.

RESULTS

A similar numerical distribution of the cell population was found in peri-implantitis around CI compared with TI. CD3 (TI, 17% to 85% versus CI, 20% to 70% of total cell number) and CD138 (TI, 1% to 73% versus CI, 12% to 69% of total cell number) were predominantly expressed. Notably, patient-individual differences of numerical cell distribution were detected. Co-localization of B- and T-lymphocytes was observed.

CONCLUSIONS

Peri-implantitis around CI in comparison with TI seems to have a similar histological appearance. Differences in cellular composition of peri-implantitis lesions might also depend on the patient's specific immune status and not only on the material used.