Surface characteristics of dental implants: A review

UV Light-Generated Superhydrophilicity of a Titanium Surface Enhances the Transfer, Diffusion and Adsorption of Osteogenic Factors from a Collagen Sponge

It is a significant challenge for a titanium implant, which is a bio-inert material, to recruit osteogenic factors, such as osteoblasts, proteins and blood effectively when these are contained in a biomaterial. The objective of this study was to examine the effect of ultraviolet (UV)-treatment of titanium on surface wettability and the recruitment of osteogenic factors when they are contained in an atelocollagen sponge. UV treatment of a dental implant made of commercially pure titanium was performed with UV-light for 12 min immediately prior to the experiments. Superhydrophilicity on dental implant surfaces was generated with UV-treatment. The collagen sponge containing blood, osteoblasts, or albumin was directly placed on the dental implant. Untreated implants absorbed only a little blood from the collagen sponge, while the UV-treated implants absorbed blood rapidly and allowed it to spread widely, almost over the entire implant surface. Blood coverage was 3.5 times greater for the UV-treated implants (p < 0.001). Only 6% of the osteoblasts transferred from the collagen sponge to the untreated implants, whereas 16% of the osteoblasts transferred to the UV-treated implants (p < 0.001). In addition, a weight ratio between transferred albumin on the implant and measured albumin adsorbed on the implant was 17.3% in untreated implants and 38.5% in UV-treated implants (p < 0.05). These results indicated that UV treatment converts a titanium surface into a superhydrophilic and bio-active material, which could recruite osteogenic factors even when they were contained in a collagen sponge. The transfer and subsequent diffusion and adsorption efficacy of UV-treated titanium surfaces could be useful for bone formation when titanium surfaces and osteogenic factors are intervened with a biomaterial.

Innovative Surface Modification Procedures to Achieve Micro/Nano-Graded Ti-Based Biomedical Alloys and Implants

Due to the growing aging population of the world, and as a result of the increasing need for dental implants and prostheses, the use of titanium and its alloys as implant materials has spread rapidly. Although titanium and its alloys are considered the best metallic materials for biomedical applications, the need for innovative technologies is necessary due to the sensitivity of medical applications and to eliminate any potentially harmful reactions, enhancing the implant-to-bone integration and preventing infection. In this regard, the implant’s surface as the substrate for any reaction is of crucial importance, and it is accurately addressed in this review paper. For constructing this review paper, an internet search was performed on the web of science with these keywords: surface modification techniques, titanium implant, biomedical applications, surface functionalization, etc. Numerous recent papers about titanium and its alloys were selected and reviewed, except for the section on forthcoming modern implants, in which extended research was performed. This review paper aimed to briefly introduce the necessary surface characteristics for biomedical applications and the numerous surface treatment techniques. Specific emphasis was given to micro/nano-structured topographies, biocompatibility, osteogenesis, and bactericidal effects. Additionally, gradient, multi-scale, and hierarchical surfaces with multifunctional properties were discussed. Finally, special attention was paid to modern implants and forthcoming surface modification strategies such as four-dimensional printing, metamaterials, and metasurfaces. This review paper, including traditional and novel surface modification strategies, will pave the way toward designing the next generation of more efficient implants.

Fabrication of Submicro-Nano Structures on Polyetheretherketone Surface by Femtosecond Laser for Exciting Cellular Responses of MC3T3-E1 Cells/Gingival Epithelial Cells

Purpose

Polyetheretherketone (PEEK) exhibits high mechanical strengths and outstanding biocompatibility but biological inertness that does not excite the cell responses and stimulate bone formation. The objective of this study was to construct submicro-nano structures on PEEK by femtosecond laser (FSL) for exciting the responses of MC3T3-E1 cells and gingival epithelial (GE) cells, which induce regeneration of bone/gingival tissues for long-term stability of dental implants.

Materials and Methods

In this study, submicro-nano structures were created on PEEK surface by FSL with power of 80 mW (80FPK) and 160 mW (160FPK).

Results

Compared with PEEK, both 80FPK and 160FPK with submicro-nano structures exhibited elevated surface performances (hydrophilicity, surface energy, roughness and protein absorption). Furthermore, in comparison with 80FPK, 160FPK further enhanced the surface performances. In addition, compared with PEEK, both 80FPK and 160FPK significantly excited not only the responses (adhesion, proliferation, alkaline phosphatase [ALP] activity and osteogenic gene expression) of MC3T3-E1 cells but also responses (adhesion as well as proliferation) of GE cells of human in vitro. Moreover, in comparison with 80FPK, 160FPK further enhanced the responses of MC3T3-E1 cells/GE cells.

Conclusion

FSL created submicro-nano structures on PEEK with elevated surface performances, which played crucial roles in exciting the responses of MC3T3-E1 cells/GE cells. Consequently, 160FPK with elevated surface performances and outstanding cytocompatibility would have enormous potential as an implant for dental replacement.

Improved response of human gingival fibroblasts to titanium coated with micro-/nano-structured tantalum

OBJECTIVES

This study aims to evaluate the ability of tantalum-coated titanium to improve human gingival fibroblasts' adhesion, viability, proliferation, migration performance, and the potential molecular mechanisms.

MATERIALS AND METHODS

Titanium plates were divided into two groups: (1) no coating (Ti, control), (2) Tantalum-coated titanium (Ta-coated Ti). All samples were characterized by scanning electronic microscopy, surface roughness, and hydrophilicity. Fibroblasts' performance were analyzed by attached cell number at 1 h, 4 h, and 24 h, morphology at 1 h and 4 h, viability at 1 day, 3 days, 5 days, and 7 days, recovery after wounding at 6 h, 12 h, and 24 h. RT-PCR, western blot were applied to detect attachment-related genes' expression and protein synthesis at 4 h and 24 h. Student's t test was used for statistical analysis.

RESULTS

Tantalum-coated titanium demonstrates a layer of homogeneously distributed nano-grains with mean diameter of 25.98 (± 14.75) nm. It was found that after tantalum deposition, human gingival fibroblasts (HGFs) adhesion, viability, proliferation, and migration were promoted in comparison to the control group. An upregulated level of Integrin β1 and FAK signaling was also detected, which might be the underlying mechanism.

CONCLUSION

In the present study, adhesion, viability, proliferation, migration of human gingival fibroblasts are promoted on tantalum-coated titanium, upregulated integrin β1 and FAK might contribute to its superior performance, indicating tantalum coating can be applied in transmucosal part of dental implant.

CLINICAL SIGNIFICANCE

Tantalum deposition on titanium surfaces can promote human gingival fibroblast adhesion, accordingly forming a well-organized soft tissue sealing and may contribute to a successful osseointegration.

A Novel Bone Substitute Based on Recombinant Type I Collagen for Reconstruction of Alveolar Cleft

This study aimed to examine the optimal cross-link density of recombinant peptide (RCP) particles, based on human collagen type I, for bone reconstruction in human alveolar cleft. Low- (group 1), medium- (group 2), and high- (group 3) cross-linked RCP particles were prepared by altering the duration of the heat-dependent dehydration reaction. Rat palatine fissures (n = 45), analogous to human congenital bone defects, were examined to evaluate the potential of bone formation by the three different RCP particles. Microcomputed tomography images were obtained to measure bone volume and bone mineral density at 4, 8, 12, and 16 weeks post grafting. Specimens were obtained for histological analysis at 16 weeks after grafting. Additionally, alkaline phosphatase and tartrate acid phosphatase staining were performed to visualize the presence of osteoblasts and osteoclasts. At 16 weeks, bone volume, bone mineral density, and new bone area measurements in group 2 were significantly higher than in any other group. In addition, the number of osteoblasts and osteoclasts on the new bone surface in group 2 was significantly higher than in any other group. Our results demonstrated that medium cross-linking was more suitable for bone formation—and could be useful in human alveolar cleft repairs as well.

Plant-Derived Nanobiomaterials as a Potential Next Generation Dental Implant Surface Modifier

Dental implants resemble synthetic materials, mainly designed as teeth-mimics to replace the damaged or irregular teeth. Specifically, they are demarcated as a surgical fixture of artificial implant materials, which are placed into the jawbone, and are allowed to be fused with the bone, similar to natural teeth. Dental implants may be categorized into endosteal, subperiosteal, and zygomatic classes, based on the placement of the implant “in the bone” or on top of the jawbone, under the gum tissue. In general, titanium and its alloys have found everyday applications as common, successful dental implant materials. However, these materials may also undergo corrosion and wear, which can lead to degradation into their ionic states, deposition in the surrounding tissues, as well as inflammation. Consequently, nanomaterials are recently introduced as a potential alternative to replace the conventional titanium-based dental implants. However, nanomaterials synthesized via physical and chemical approaches are either costly, non/less biocompatible, or toxic to the bone cells. Hence, biosynthesized nanomaterials, or bionanomaterials, are proposed in recent studies as potential non-toxic dental implant candidates. Further, nanobiomaterials with plant origins, such as nanocelluloses, nanometals, nanopolymers, and nanocarbon materials, are identified to possess enhanced biocompatibility, bioavailability and no/less cytotoxicity with antimicrobial efficacy at low costs and ease of fabrication. In this minireview, we present an outline of recent nanobiomaterials that are extensively investigated for dental implant applications. Additionally, we discuss their action mechanisms, applicability, and significance as dental implants, shortcomings, and future perspectives.

Graphene Oxide: Opportunities and Challenges in Biomedicine

Desirable carbon allotropes such as graphene oxide (GO) have entered the field with several biomedical applications, owing to their exceptional physicochemical and biological features, including extreme strength, found to be 200 times stronger than steel; remarkable light weight; large surface-to-volume ratio; chemical stability; unparalleled thermal and electrical conductivity; and enhanced cell adhesion, proliferation, and differentiation properties. The presence of functional groups on graphene oxide (GO) enhances further interactions with other molecules. Therefore, recent studies have focused on GO-based materials (GOBMs) rather than graphene. The aim of this research was to highlight the physicochemical and biological properties of GOBMs, especially their significance to biomedical applications. The latest studies of GOBMs in biomedical applications are critically reviewed, and in vitro and preclinical studies are assessed. Furthermore, the challenges likely to be faced and prospective future potential are addressed. GOBMs, a high potential emerging material, will dominate the materials of choice in the repair and development of human organs and medical devices. There is already great interest among academics as well as in pharmaceutical and biomedical industries.

The bone anchored prostheses for amputees - Historical development, current status, and future aspects

In the past 50 years, bone anchored prostheses have evolved from a concept for experimental treatment to a rapidly developing area in orthopedics and traumatology. Up to date, there are dozens of centers in the world providing osseointegration amputation reconstructions and more than a thousand patients using the bone anchored prostheses. Compared with conventional socket prostheses, the bone anchored prosthesis by osseointegration avoids the debilitating problems related with soft tissues. It also provides physiological weight bearing, improved range of motion, and sensory feedback, all of which contribute to the improvement on quality of life for amputees. The present article briefly reviews the historical development of osseointegration surgery for amputation reconstruction and the current challenges. The implant design characters and surgical techniques of the two types of implants; the screw-type implant (presented by the OPRA system), and the press-fit implants (presented by EEP and OPL systems) are described. The major complications, infections and mechanical failures, are discussed in detail based on the latest evidence. Future aspects and experimental trials aiming to overcome the current challenges are presented.

Surface modifications to enhance osseointegration-Resulting material properties and biological responses

As life expectancy and the age of the general population increases so does the need for improved implants. A major contributor to the failure of implants is poor osseointegration, which is typically described as the direct connection between bone and implant. This leads to unnecessary complications and an increased burden on the patient population. Modification of the implant surfaces through novel techniques, such as varying topography and/or applying coatings, has become a popular method to enhance the osseointegration capability of implants. Recent research has shown that particular surface features influence how bone cells interact with a material; however, it is unknown which exact features achieve optimal bone integration. In this review, current methods of modifying surfaces will be highlighted, and the resulting surface characteristics and biological responses are discussed. Review of the current strategies of surface modifications found that many coating types are more advantageous when used in combination; however, finding a surface modification that utilizes the mutual beneficial effects of important surface characteristics while still maintaining commercial viability is where future challenges exist.

Towards Clinical Translation: Optimized Fabrication of Controlled Nanostructures on Implant-Relevant Curved Zirconium Surfaces

Anodization enables fabrication of controlled nanotopographies on Ti implants to offer tailorable bioactivity and local therapy. However, anodization of Zr implants to fabricate ZrO₂ nanostructures remains underexplored and are limited to the modification of easy-to-manage flat Zr foils, which do not represent the shape of clinically used implants. In this pioneering study, we report extensive optimization of various nanostructures on implant-relevant micro-rough Zr curved surfaces, bringing this technology closer to clinical translation. Further, we explore the use of sonication to remove the top nanoporous layer to reveal the underlying nanotubes. Nano-engineered Zr surfaces can be applied towards enhancing the bioactivity and therapeutic potential of conventional Zr-based implants.

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

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

Laser surface texturing of zirconia-based ceramics for dental applications: A review

Laser surface texturing is widely explored for modifying the surface topography of various materials and thereby tuning their optical, tribological, biological, and other surface properties. In dentistry, improved osseointegration has been observed with laser textured titanium dental implants in clinical trials. Due to several limitations of titanium materials, dental implants made of zirconia-based ceramics are now considered as one of the best alternatives. Laser surface texturing of zirconia dental implants is therefore attracting increasing attention. However, due to the brittle nature of zirconia, as well as the metastable tetragonal ZrO₂ phase, laser texturing in the case of zirconia is more challenging than in the case of titanium. Understanding these challenges requires different fields of expertise, including laser engineering, materials science, and dentistry. Even though much progress was made within each field of expertise, a comprehensive analysis of all the related factors is still missing. This review paper provides thus an overview of the common challenges and current status on the use of lasers for surface texturing of zirconia-based ceramics for dental applications, including texturing of zirconia implants for improving osseointegration, texturing of zirconia abutments for reducing peri-implant inflammation, and texturing of zirconia restorations for improving restoration retention by bonding.

Surface Roughness of Dental Implant and Osseointegration

INTRODUCTION

Dental implants are a usual treatment for the loss of teeth. The success of this therapy is due to the predictability, safety and longevity of the bone-implant interface. Dental implant surface characteristics like roughness, chemical constitution, and mechanical factors can contribute to the early osseointegration. The aim of the present article is to perform a review of the literature on surface roughness of dental implant and osseointegration.

METHODOLOGY

This work is a narrative review of some aspects of surface roughness of dental implant and osseointegration.

CONCLUSION

Despite technological advancement in the biomaterials field, the ideal surface roughness for osseointegration still remains unclear. In this study about surface nanoroughness of dental implant and osseointegration, the clinical relevance is yet unknown. Innovative findings on nanoroughness are valuable in the fields of dental implantology, maxillofacial or orthopedic implant surfaces and also on cardiovascular implants in permanent contact with patient's blood.

Antibiofilm effects of titanium surfaces modified by laser texturing and hot-pressing sintering with silver

Peri-implant diseases are one of the main causes of dental implant failure. New strategies for dental implants manufacturing have been developed to prevent the accumulation of bacteria and related inflammatory reactions. The main aim of this work was to develop laser-treated titanium surfaces covered with silver that generate a electrical dipole to inhibit the oral bacteria accumulation. Two approaches were developed for that purpose. In one approach a pattern of different titanium dioxide thickness was produced on the titanium surface, using a Q-Switched Nd:YAG laser system operating at 1064 nm. The second approach was to incorporate silver particles on a laser textured titanium surface. The incorporation of the silver was performed by laser sintering and hot-pressing approaches. The anti-biofilm effect of the discs were tested against biofilms involving 14 different bacterial strains growth for 24 and 72 hr. The morphological aspects of the surfaces were evaluated by optical and field emission guns scanning electronical microscopy (FEGSEM) and therefore the wettability and roughness were also assessed. Physicochemical analyses revealed that the test surfaces were hydrophilic and moderately rough. The oxidized titanium surfaces showed no signs of antibacterial effects when compared to polished discs. However, the discs with silver revealed a decrease of accumulation of Porphyromonas gingivalis and Prevotella intermedia strains. Thus, the combination of Nd:YAG laser irradiation and hot-pressing was effective to produce silver-based patterns on titanium surfaces to inhibit the growth of pathogenic bacterial species. The laser parameters can be optimized to achieve different patterns, roughness, and thickness of the modified titanium layer regarding the type and region of the implant.

Physicochemical properties of anodized-hydrothermally treated titanium with a nanotopographic surface structure promote osteogenic differentiation in dental pulp stem cells

PURPOSE

Implants made of anodized-hydrothermally treated commercially pure titanium with a nanotopographic surface structure (SA-treated c.p.Ti) may advantageously promote contact osteogenesis during the early stages of healing. We hypothesized that utilizing SA-treated c.p.Ti with dental pulp stem cells (DPSCs) might improve osteoconduction during the process of osseointegration. This in vitro study investigated the effect of initial adhesion of DPSCs to SA-treated c.p.Ti compared with conventional c.p.Ti and anodic oxide (AO) c.p.Ti.

METHODS

DPSCs were obtained from the mandibular incisors of Sprague-Dawley rats and cultured without osteogenic induction medium on c.p.Ti, AO c.p.Ti, and SA-treated c.p.Ti disks for up to 14 days. The morphology, proliferation, and differentiation of DPSCs were assessed by scanning electron microscopy, an MTT assay, and Alizarin Red S staining, respectively. A real-time quantitative polymerase chain reaction was used to quantify the mRNA expression of osteocalcin, osteopontin, and bone sialoprotein.

RESULTS

On all disks, the DPSCs appeared flattened with the formation of extensions over time. The filopodium-like extensions were closely bound to the SA-treated c.p.Ti surface. The proliferation of DPSCs was not significantly different among the c.p.Ti treatments. However, DPSCs on SA-treated c.p.Ti showed the greatest mRNA levels of osteopontin, osteocalcin, and bone sialoprotein, as well as increased Alizarin Red S staining.

CONCLUSIONS

The results of the present in vitro study demonstrate that the surface properties of SA-treated c.p.Ti disks enhance osteogenic differentiation of DPSCs and may facilitate mineralized matrix formation on SA-treated c.p.Ti implant surfaces, which can enhance early bone regeneration.

Surface characteristics on commercial dental implants differentially activate macrophages in vitro and in vivo

OBJECTIVES

Biomaterial implantation provokes an inflammatory response that controls integrative fate. M2 macrophages regulate the response to implants by resolving the inflammatory phase and recruiting progenitor cells to aid healing. We have previously shown that modified titanium (Ti) disks directly induce M2 macrophage polarization. The aim of this study was to examine macrophage response to commercially available Ti or Ti alloy implants with comparable roughness and varying hydrophilicity.

MATERIAL AND METHODS

Eleven commercially available Ti (A-F) or Ti alloy (G-K) dental implants were examined in this study. Surface topography, chemistry, and hydrophilicity were characterized for each implant. To compare the immune response in vitro, human monocyte-derived macrophages were seeded on implants and secreted pro- and anti-inflammatory proteins measured. To evaluate the inflammatory response in vivo, mice were subcutaneously instrumented with clinical implants, and implant adherent macrophage populations were characterized by flow cytometry.

RESULTS

Macrophages on hydrophobic Implant C produced the highest level of pro-inflammatory proteins in vitro. In contrast, hydrophilic Implant E produced the second-highest pro-inflammatory response. Implants F and K, both hydrophilics, produced the highest anti-inflammatory protein secretions. Likewise, pro-inflammatory CD80hi macrophages predominated in vivo on implants C and E, and M2 CD206 + macrophages predominated on implants F and K.

CONCLUSIONS

These findings show that hydrophilicity alone is insufficient to predict the anti-inflammatory effect on macrophage polarization and that other properties-surface composition or topography-determine immune modulation. This in vivo model may be a useful screening method to compare the immunomodulatory response to clinical implants of disparate geometry or size.

Two- and ten-year follow-up of patients responding and non-responding to the surgical treatment of peri-implantitis: A retrospective evaluation

OBJECTIVES

To report a follow-up of patients following the surgical anti-infective treatment of peri-implantitis and to identify possible risk indicators for the progression of disease during supportive peri-implant therapy.

MATERIAL AND METHODS

Following peri-implant surgery, 41 patients (213 implants) were enrolled in a supportive peri-implant therapy. At the 2-year follow-up, two groups of patients were identified, with or without residual peri-implant pockets (responding and non-responding group). Eighteen patients (85 implants) of the non-responding group were followed for further 8 years.

RESULTS

At the 2-year examination, 73 of the 117 treated implants (62.4%) presented healthy peri-implant condition, while 44 (37.6%) presented persisting peri-implantitis associated with substantial bone loss before treatment. The 10-year examination of the non-responding group revealed that 1) 84% of the implants that regained health following surgery remained healthy during the entire observation period; 2) 66% of the implants with residual pockets following surgery maintained stable peri-implant condition; and 3) 29% of all treated implants showed disease progression, and 11 of those were extracted. Presence of pockets at 3-4 sites of the implants was identified as risk indicator for progression of peri-implantitis.

CONCLUSION

The peri-implant health achieved following therapy was maintained for most of the implants during the follow-up. Residual pockets were a frequent finding at implants with substantial bone loss before treatment. Presence of pockets around the entire circumference of the implants resulted as a risk indicator for further disease progression. The probability of progression of peri-implant disease increased with increased observation time.

Optimizing citric acid protocol to control implant-related infections: An in vitro and in situ study

OBJECTIVE

The present study aimed to establish an optimized protocol for biofilm removal from titanium (Ti) surfaces using citric acid (CA) solutions.

BACKGROUND

Biofilm accumulation is the main factor to trigger peri-implant infections and to increase the risk of treatment failures. Although CA has been suggested as the anti-infective agent with highest potential for biofilm removal on Ti, there is no consensus that CA could improve the anti-infective treatment and its effect.

METHODS

Physical and chemical alterations, electrochemical behavior, cytotoxicity, and antimicrobial effect of CA on Ti discs were evaluated using four concentrations (1, 10, 20, and 40%) and two application methods (immersion and rubbing). Negative control using 0.9% NaCl was used in all experiments. To evaluate whether different application times can have similar response, polymicrobial biofilm (microcosm model) was formed on Ti and treated with CA for 1, 2, 4, and 8 min. An in situ study was conducted to verify whether the established protocol is equally effective in biofilms formed on machined and sandblasted, large-grit, and acid-etched (SLA) Ti surfaces.

RESULTS

CA 40% induced significantly higher surface alterations observed by confocal images and profilometry. In general, rubbing protocol decreased the surface roughness and increased the wettability (p < 0.05), exhibiting better surface cleaning by biofilm removal. CA 10% presented no indirect cytotoxicity and, when applied by rubbing for 8 min, presented proper in vitro antibacterial action and potential corrosion inhibition. When CA 10% was rubbed on Ti surfaces for 4 min, it displayed optimum cleaning ability as 8 min, working equally to remove in situ biofilm on machined and SLA surfaces.

CONCLUSIONS

The application of CA 10% by rubbing for at least 4 min demonstrated to be a promising protocol to eliminate biofilms formed in smooth and rougher surfaces, which could improve implant-related infection therapies.

Nerve growth factor-chondroitin sulfate/hydroxyapatite-coating composite implant induces early osseointegration and nerve regeneration of peri-implant tissues in Beagle dogs

Background

Osseointegration is the premise of the chewing function of dental implant. Nerve growth factor (NGF), as a neurotrophic factor, can induce bone healing. However, the influence of NGF-chondroitin sulfate (CS)/hydroxyapatite (HA)-coating composite implant on the osseointegration and innervations is still not entirely clear.

Materials and methods

NGF-CS/HA-coating composite implants were prepared using the modified biomimetic method. The characteristics of NGF-CS/HA-coating implants were determined using a scanning electron microscope. After NGF-CS/HA-coating implants were placed in the mandible of Beagle dogs, the early osseointegration and innervation in peri-implant tissues were assessed through X-ray, Micro-CT, maximal pull-out force, double fluorescence staining, toluidine blue staining, DiI neural tracer, immunohistochemistry, and RT-qPCR assays.

Results

NGF-CS/HA-coating composite implants were made successfully, which presented porous mesh structures with the main components (Ti and HA). Besides, we revealed that implantation of NGF-CS/HA-coating implants significantly changed the morphology of bone tissues and elevated maximum output, MAR, BIC, and nerve fiber in the mandible of Beagle dogs. Moreover, we proved that the implantation of NGF-CS/HA-coating implants also markedly upregulated the levels of NGF, osteogenesis differentiation, and neurogenic differentiation-related genes in the mandible of Beagle dogs.

Conclusion

Implantation of NGF-CS/HA-coating composite implants has significant induction effects on the early osseointegration and nerve regeneration of peri-implant tissues in the mandible of Beagle dogs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-020-02177-5.

Enhanced Osseointegration by the Hierarchical Micro-Nano Topography on Selective Laser Melting Ti-6Al-4V Dental Implants

Currently, selective laser melting (SLM) has been thriving in implant dentistry for on-demand fabricating dental implants. Based on the coarse microtopography of SLM titanium surfaces, constructing nanostructure to form the hierarchical micro-nano topography is effective in enhancing osseointegration. Given that current nanomodification techniques of SLM implants, such as anodization and hydrothermal treatment, are facing the inadequacy in costly specific apparatus and reagents, there has been no recognized nanomodified SLM dental implants. The present study aimed to construct hierarchical micro-nano topography on self-made SLM dental implants by a simple and safe inorganic chemical oxidation, and to evaluate its contribution on osteoblastic cells bioactivity and osseointegration. The surface chemical and physical parameters were characterized by FE-SEM, EDS, profilometer, AFM, and contact angle meter. The alteration on bioactivity of MG-63 human osteoblastic cells were detected by qRT-PCR. Then the osseointegration was assessed by implanting implants on the femur condyle of New Zealand Rabbits. The hierarchical micro-nano topography was constituted by the microrough surface of SLM implants and nanoneedles (diameter: 20∼50 nm, height: 150∼250 nm), after nanomodifying SLM implants in 30% hydrogen peroxide and 30% hydrochloride acid (volume ratio 1:2.5) at room temperature for 36 h. Low chemical impurities content and high hydrophilicity were observed in the nanomodified group. Cell experiments on the nanomodified group showed higher expression of mitophagy related gene (PINK1, PARKIN, LC3B, and LAMP1) at 5 days and higher expression of osteogenesis related gene (Runx2 and OCN) at 14 days. In the early stage of bone formation, the nanomodified SLM implants demonstrated higher bone-to-implant contact. Intriguingly, the initial bone-to-implant contact of nanomodified SLM implants consisted of more mineralized bone with less immature osteoid. After the cessation of bone formation, the bone-to-implant contact of nanomodified SLM implants was equal to untreated SLM implants and marketable TixOs implants. The overall findings indicated that the inorganic chemical oxidized hierarchical micro-nano topography could enhance the bioactivity of osteoblastic cells, and consequently promote the peri-implant bone formation and mineralization of SLM dental implants. This study sheds some light on improvements in additive manufactured dental implants.

Co-implantation of magnesium and zinc ions into titanium regulates the behaviors of human gingival fibroblasts

Soft tissue sealing around implants acts as a barrier between the alveolar bone and oral environment, protecting implants from the invasion of bacteria or external stimuli. In this work, magnesium (Mg) and zinc (Zn) are introduced into titanium by plasma immersed ion implantation technology, and their effects on the behaviors of human gingival fibroblasts (HGFs) as well as the underlying mechanisms are investigated. Surface characterization confirms Mg and Zn exist on the surface in metallic and oxidized states. Contact angle test suggests that surface wettability of titanium changes after ion implantation and thus influences protein adsorption of surfaces. In vitro studies disclose that HGFs on Mg ion-implanted samples exhibit better adhesion and migration while cells on Zn ion-implanted samples have higher proliferation rate and amounts. The results of immunofluorescence staining and real-time reverse-transcriptase polymerase chain reaction (RT-PCR) suggest that Mg mainly regulates the motility and adhesion of HGFs through activating the MAPK signal pathway whereas Zn influences HGFs proliferation by triggering the TGF-β signal pathway. The synergistic effect of Mg and Zn ions ensure that HGFs cultured on co-implanted samples possessed both high proliferation rate and motility, which are critical to soft tissue sealing of implants.

Implant functionalization with mesoporous silica: A promising antibacterial strategy, but does such an implant osseointegrate?

Objectives

New strategies for implant surface functionalization in the prevention of peri‐implantitis while not compromising osseointegration are currently explored. The aim of this in vivo study was to assess the osseointegration of a titanium‐silica composite implant, previously shown to enable controlled release of therapeutic concentrations of chlorhexidine, in the Göttingen mini‐pig oral model.

Material and Methods

Three implant groups were designed: macroporous titanium implants (Ti‐Porous); macroporous titanium implants infiltrated with mesoporous silica (Ti‐Porous + SiO₂); and conventional titanium implants (Ti‐control). Mandibular last premolar and first molar teeth were extracted bilaterally and implants were installed. After 1 month healing, the bone in contact with the implant and the bone regeneration in the peri‐implant gap was evaluated histomorphometrically.

Results

Bone‐to‐implant contact and peri‐implant bone volume for Ti‐Porous versus Ti‐Porous + SiO₂ implants did not differ significantly, but were significantly higher in the Ti‐Control group compared with Ti‐Porous + SiO₂ implants. Functionalization of titanium implants via infiltration of a SiO₂ phase into the titanium macropores does not seem to inhibit implant osseointegration. Yet, the importance of the implant macro‐design, in particular the screw thread design in a marginal gap implant surgery set‐up, was emphasized by the outstanding results of the Ti‐Control implant.

Conclusions

Next‐generation implants made of macroporous Ti infiltrated with mesoporous SiO₂ do not seem to compromise the osseointegration process. Such implant functionalization may be promising for the prevention and treatment of peri‐implantitis given the evidenced potential of mesoporous SiO₂ for controlled drug release.

Effects of Surface Modification on Adsorption Behavior of Cell and Protein on Titanium Surface by Using Quartz Crystal Microbalance System

Primary stability and osseointegration are major challenges in dental implant treatments, where the material surface properties and wettability are critical in the early formation of hard tissue around the implant. In this study, a quartz crystal microbalance (QCM) was used to measure the nanogram level amount of protein and bone marrow cells adhered to the surfaces of titanium (Ti) surface in real time. The effects of ultraviolet (UV) and atmospheric-pressure plasma treatment to impart surface hydrophilicity to the implant surface were evaluated. The surface treatment methods resulted in a marked decrease in the surface carbon (C) content and increase in the oxygen (O) content, along with super hydrophilicity. The results of QCM measurements showed that adhesion of both adhesive proteins and bone marrow cells was enhanced after surface treatment. Although both methods produced implants with good osseointegration behavior and less reactive oxidative species, the samples treated with atmospheric pressure plasma showed the best overall performance and are recommended for clinical use. It was verified that QCM is an effective method for analyzing the initial adhesion process on dental implants.

Bone and Cartilage Interfaces With Orthopedic Implants: A Literature Review

The interface between a surgical implant and tissue consists of a complex and dynamic environment characterized by mechanical and biological interactions between the implant and surrounding tissue. The implantation process leads to injury which needs to heal over time and the rapidity of this process as well as the property of restored tissue impact directly the strength of the interface. Bleeding is the first and most relevant step of the healing process because blood provides growth factors and cellular material necessary for tissue repair. Integration of the implants placed in poorly vascularized tissue such as articular cartilage is, therefore, more challenging than compared with the implants placed in well-vascularized tissues such as bone. Bleeding is followed by the establishment of a provisional matrix that is gradually transformed into the native tissue. The ultimate goal of implantation is to obtain a complete integration between the implant and tissue resulting in long-term stability. The stability of the implant has been defined as primary (mechanical) and secondary (biological integration) stability. Successful integration of an implant within the tissue depends on both stabilities and is vital for short- and long-term surgical outcomes. Advances in research aim to improve implant integration resulting in enhanced implant and tissue interface. Numerous methods have been employed to improve the process of modifying both stability types. This review provides a comprehensive discussion of current knowledge regarding implant-tissue interfaces within bone and cartilage as well as novel approaches to strengthen the implant-tissue interface. Furthermore, it gives an insight into the current state-of-art biomechanical testing of the stability of the implants. Current knowledge reveals that the design of the implants closely mimicking the native structure is more likely to become well integrated. The literature provides however several other techniques such as coating with a bioactive compound that will stimulate the integration and successful outcome for the patient.

Histological and Nanomechanical Properties of a New Nanometric Hydroxiapatite Implant Surface. An In Vivo Study in Diabetic Rats

Implant therapy is a predictable treatment to replace missing teeth. However, the osseointegration process may be negatively influenced by systemic conditions, such as diabetes mellitus (DM). Microtopography and implant surface developments are strategies associated to better bone repair. This study aimed to evaluate, in healthy and diabetic rats, histomorphometric (bone to implant contact = %BIC; and bone area fraction occupancy = %BAFO) and nanomechanical (elastic modulus = EM; and hardness = H) bone parameters, in response to a nanometric hydroxyapatite implant surface. Mini implants (machined = MAC; double acid etched = DAE, and with addition of nano-hydroxyapatite = NANO) were installed in tibias of healthy and diabetic rats. The animals were euthanized at 7 and 30 days. NANO surface presented higher %BIC and %BAFO when compared to MAC and DAE (data evaluated as a function of implant surface). NANO surface presented higher %BIC and %BAFO, with statistically significant differences (data as a function of time and implant surface). NANO surface depicted higher EM and H values, when compared to machined and DAE surfaces (data as a function of time and implant surface). Nano-hydroxyapatite coated implants presented promising biomechanical results and could be an important tool to compensate impaired bone healing reported in diabetics.

Prevalence and risk indicators of peri-implant diseases in a group of Moroccan patients

BACKGROUND

To report the prevalence of peri-implant diseases in a North African patient population, and to assess the concurrent associations of patient- and implant-level characteristics with probing depth and bone loss around dental implants METHODS: A total of 642 implants in 145 subjects were followed up for a mean 6.4 years. At the last follow-up visit the subjects were examined clinically and radiographically to assess the status of peri-implant tissues and teeth. Data analysis used the generalized linear mixed models RESULTS: The prevalence of peri-implant mucositis and peri-implantitis were 82.1% and 41.4% at the subject level, and 68.4% and 22.7% at the implant level, respectively. Inadequate plaque control, peri-implant inflammation, history of previous implant failures, and pain/discomfort at the implant site were significantly associated with both outcomes (increased probing depth and bone loss). Diabetes mellitus, inadequate implant restoration, single restorations (versus multi-unit), cement-retained restorations, and presence of occlusal wear facets on teeth were significantly associated with one of the two outcomes. Implants placed in the lower anterior jaw region had the most favorable outcome. Smoking, history of periodontitis, and type of implant surface did not show significant associations with higher frequency of peri-implant diseases in the multivariable analysis.

CONCLUSIONS

Peri-implant diseases are prevalent in this North African patient population. Multiple subject- and implant-level variables were associated with peri-implant diseases. Risk assessment of these effects should consist of a concurrent inclusion of these factors in multivariable analyses that also adjust for the complex variance structure of the oral environment.

Hydroxyapatite Formation on Coated Titanium Implants Submerged in Simulated Body Fluid

Titanium implants are commonly used in the field of dentistry for prosthetics such as crowns, bridges, and dentures. For successful therapy, an implant must bind to the surrounding bone in a process known as osseointegration. The objective for this ongoing study is to determine the potential of different implant surface coatings in providing the formation of hydroxyapatite (HA). The coatings include titanium nitride (TiN), silicon dioxide (SiO2), and quaternized titanium nitride (QTiN). The controls were a sodium hydroxide treated group, which functioned as a positive control, and an uncoated titanium group. Each coated disc was submerged in simulated body fluid (SBF), replenished every 48 h, over a period of 28 days. Each coating successfully developed a layer of HA, which was calculated through mass comparisons and observed using scanning electron microscopy (SEM) and energy dispersive analysis x-rays (EDX). Among these coatings, the quaternized titanium nitride coating seemed to have a better yield of HA. Further studies to expand the data concerning this experiment are underway.

Micro/nanostructured calcium phytate coating on titanium fabricated by chemical conversion deposition for biomedical application

A bioactive micro/nanostructured calcium phytate coating was successfully prepared on titanium surfaces by chemical conversion deposition, mainly through hydrothermal treatment of a mixed solution of phytic acid and saturated calcium hydroxide solution. Ultraviolet radiation was carried out to improve the adhesion of the coating to the titanium substrate. Pure titanium with a sandblasted/acid-etched surface was used as the control group. The topography and chemical composition of the modified surfaces were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and static water contact angle measurement. A pull-off test was performed to measure the coating-to-substrate adhesion strength. Bovine serum albumin was used as a model to study the protein adsorption effect. Cells were cultured on titanium surfaces for 7 days in osteogenic differentiation medium, then the osteoblast compatibility in vitro were explored by alkaline phosphatase and alizarin red staining. After 1, 2, 4 and 8 wks of immediate implantation of titanium implants into the mandibles of New Zealand white rabbits, biological effects in vivo were researched by microcomputed tomography analysis and histological evaluation. The results indicated that the roughness and hydrophilicity of the modified surfaces with micro/nanostructure remarkably increased compared to those of the control group. The pull-off test showed the average adhesion strength at the coating-substrate interface to be higher than 13.56 ± 1.71 MPa. In addition, approximately 4.41 mg/L calcium ion was released from the calcium phytate micro/nano coatings to the local environment after 48 h of immersion. More importantly, the micro/nanostructure titanium substrates significantly promoted cellular differentiation in vitro and in vivo. After 8 wks, the bone implant contact ratio (BIC, %) of the modified implants was higher than that of the control group, at 94.09 ± 0.55% and 86.18 ± 1.99% (p < 0.05). Overall, this study provided new insights into the factors promoting early osseointegration of titanium alloys, which had great potential not only for dental implants but also for various other biomaterial applications.

Role of New Hydrophilic Surfaces on Early Success Rate and Implant Stability: 1-Year Post-loading Results of a Multicenter, Split-Mouth, Randomized Controlled Trial

OBJECTIVE

 To compare early implant failure and implant stability of one-stage Hiossen ET III implants with its new hydrophilic (NH) surface, compared with Hiossen ET III implants with the sandblasted and acid-etched (SA) surface at 1-year follow-up.

MATERIALS AND METHODS

 This study was designed as a split-mouth, multicenter randomized controlled trial aimed to compare SA surface implants (SA group) and NH surface, (NH group). Outcomes were implant and prosthetic survival rates, complications, the insertion torque at implant placement, and implant stability quotient (ISQ) values.

RESULTS

 Twenty-nine patients (mean age 59.9 ± 11.3 years) were treated and followed up to 1 year after loading. No patient dropped out. Fifty-eight implants (29 SA group and 29 NH group) were placed. No implants or prostheses failed and no complications were experienced during follow-up. The mean insertion torque was 40.5 ± 3.23 (38.17-41.83) Ncm in the SA group and 40.48 ± 3.49 (38.02-41.98) Ncm in the NH group (p = 0.981). There was a statistically significant difference at the second week (T2) with higher values in the NH group (p = 0.041). Similar results were found in the maxilla (p = 0.045), but not in the mandible (p = 0.362). A positive correlation was found between initial insertion torque and ISQ with higher value in the NH group (0.73 vs. 0.66).

CONCLUSIONS

 NH implants are a viable alternative to SA surface, as they seem to avoid the ISQ drop during the bone remodeling phase.

Does implant surface hydrophilicity influence the maintenance of surface integrity after insertion into low-density artificial bone?

OBJECTIVE

To evaluate the influence of hydrophilicity on the surface integrity of implants after insertion in low-density artificial bone and to determine the distribution of titanium (Ti) particles along the bone bed.

METHODS

Forty-eight dental implants with different designs (Titamax Ex, Facility, Alvim, and Drive) and surface treatments (Neoporos® and Aqua™) were inserted into artificial bone blocks with density compatible with bone type III-IV. Hydrophobic Neoporos® surfaces were obtained by sandblasting and acid etching while hydrophilic Aqua™ surfaces were obtained by sandblasting, acid etching, and storage in an isotonic 0.9% NaCl solution. The surface integrity was evaluated by Scanning Electron Microscope (SEM) and the surface roughness parameters (Sa, Sp, Ssk, Sdr, Spk, Sk, and Svk) and surface area were measured with Laser Scanning Confocal Microscopy before and after installation. Bone beds were inspected with Digital Microscopy and micro X-Ray Fluorescence (μ-XRF) to analyze the metallic element distribution along the bone bed.

RESULTS

Acqua™ implants had higher initial Sa and a pronounced reduction of Sa and Sp during insertion, compared to NeoPoros® implants. After insertion, Sa and Sp of Acqua™ and NeoPoros® implants equalized, differing only between designs of Acqua™ implants. Surface damage was observed after insertion, mainly in the apical region. Facility implants that are made of TiG5 released fewer debris particles, while the highest Ti intensity was detected in the cervical region of the Titamax Ex Acqua™ and Drive Acqua™ implants.

SIGNIFICANCE

Physicochemical modifications to achieve surface hydrophilicity created a rougher surface that was more susceptible to surface alterations, resulting in more Ti particle release into the bone bed during surgical insertion. The higher Ti intensities detected in the cervical region of bone beds may be related to peri-implantitis and marginal bone resorption.

Porous Tantalum VS. Titanium Implants: Enhanced Mineralized Matrix Formation after Stem Cells Proliferation and Differentiation

Titanium dental implants are used routinely, with surgical procedure, to replace missing teeth. Even though they lead to satisfactory results, novel developments with implant materials can still improve implant treatment outcomes. The aim of this study was to investigate the efficiency of porous tantalum (Ta) dental implants for osseointegration, in comparison to classical titanium (Ti). Mesenchymal stem cells from the dental pulp (DPSC) were incubated on Ta, smooth titanium (STi), and rough titanium (RTi) to assess their adhesion, proliferation, osteodifferentiation, and mineralized matrix production. Cell proliferation was measured at 4 h, 24 h, 48 h with MTT test. Early osteogenic differentiation was followed after 4, 8, 12 days by alkaline phosphatase (ALP) quantification. Cells organization and matrix microstructure were studied with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). Collagen production and matrix mineralization were evaluated by immunostaining and histological staining. MTT test showed significantly higher proliferation of DPSC on Ta at 24 h and 48 h. However, APL quantification after 8 and 12 days was significantly lower for Ta, revealing a delayed differentiation, where cells were proliferating the more. After 3 weeks, collagen immunostaining showed an efficient production of collagen on all samples. However, Red Alizarin staining clearly revealed a higher calcification on Ta. The overall results tend to demonstrate that DPSC differentiation is delayed on Ta surface, due to a longer proliferation period until cells cover the 3D porous Ta structure. However, after 3 weeks, a more abundant mineralized matrix is produced on and inside Ta implants. Cell populations on porous Ta proliferate greater and faster, leading to the production of more calcium phosphate deposits than cells on roughened and smooth titanium surfaces, revealing a potential enhanced capacity for osseointegration.

New Ti-Mo-Si materials for bone prosthesis applications

Several newly obtained titanium alloys were characterized in order to evaluate the biocompatibility and their possible application as implants. For improvement of the performances of the TiMo alloys compared to other alloys, silicon was added, targeting good mechanical and technological properties, avoiding the toxic effects for human body. Titanium is very used in medical applications, due to their extremely low toxicity and good chemical stability in different body fluids. Four Ti15MoxSi (where x = 0, 0.5, 0.75, 1.0 wt %), alloys were developed and investigated regarding microstructure, mechanical, chemical and biological behavior (in vitro and in vivo evaluation). By increasing the Si content from 0 to 1% wt., the mechanical properties of the Ti15Mo alloys were significantly improved. By increasing the Si content from 0 to 1% wt., the mechanical properties of the Ti15Mo alloys were significantly improved (about 50%) from 44.50 GPa to 19.81 GPa modulus of elasticity and the hardness values 361.28 to 188.52 HV. The cytocompatibility assessment on human line osteoblasts indicated good cell-material interactions and in vivo tests indicated a successful osseointegration, the surrounding newly bone being formed without any significant inflammatory reaction. Expression of osteopontin in the peri-implant area highlights the presence of osteogenesis and bone mineralization. Metalloproteinase-2 (gelatinase A) and metallopeptidase-9 (gelatinase B) overexpression in osteoblasts, osteoclasts and osteocytes represent the markers of normal bone remodeling. All these results suggest that the TiMoSi alloys are promising materials for orthopedics devices, since mechanical properties and biocompatibility offer conditions for applying them as biomaterial.

Hyaluronic acid as a bioactive component for bone tissue regeneration: Fabrication, modification, properties, and biological functions

Hyaluronic acid (HA) is widely distributed in the human body, and it is heavily involved in many physiological functions such as tissue hydration, wound repair, and cell migration. In recent years, HA and its derivatives have been widely used as advanced bioactive polymers for bone regeneration. Many medical products containing HA have been developed because this natural polymer has been proven to be nontoxic, noninflammatory, biodegradable, and biocompatible. Moreover, HA-based composite scaffolds have shown good potential for promoting osteogenesis and mineralization. Recently, many HA-based biomaterials have been fabricated for bone regeneration by combining with electrospinning and 3D printing technology. In this review, the polymer structures, processing, properties, and applications in bone tissue engineering are summarized. The challenges and prospects of HA polymers are also discussed.

Nanotechnology in dentistry: Present and future perspectives on dental nanomaterials

OBJECTIVES

The number of dental nanomaterials has increased significantly over the past years. A variety of commercial dental nanomaterials are available and researched. Nevertheless, how these nanomaterials work, what makes them special and whether they are superior to traditional dental materials is not always clear to dentists and researchers. The objective of this review paper is, therefore, to give an overview of the principles of nanomaterials and basic research and applications of dental nanomaterials.

METHODS

The fundamentals of materials science of nanomaterials as well as their advantages and disadvantages are elaborated. The most important dental nanomaterials are discussed. This is mainly based on a survey of the literature and a review of the most frequently cited scientific papers in the international peer reviewed journal Dental Materials over the past five years. The developments of commercial dental nanomaterials as well as aspects of their clinical use are considered in this review.

RESULTS

Nanomaterials have unique structures and properties that distinguish them from other materials. The journal Dental Materials is the journal with the highest numbers of articles and citations on the subject of dental nanomaterials. The most frequently reported dental nanomaterials are nanocomposites, nanoparticles, antimicrobial nanomaterials and bio-mineralization systems. Hallmarks of dental nanomaterials include a set of unique properties and challenges in the preparation of these materials.

SIGNIFICANCE

By understanding the physical principles of dental nanomaterials, their strengths, limitations and their specific benefits will be better appreciated. Dental nanomaterials have potential for the future but currently do not always exhibit superior properties, for example in clinical situations.

Different binding mechanisms of Staphylococcus aureus to hydrophobic and hydrophilic surfaces

Bacterial adhesion to surfaces is a crucial step in initial biofilm formation. In a combined experimental and computational approach, we studied the adhesion of the pathogenic bacterium Staphylococcus aureus to hydrophilic and hydrophobic surfaces. We used atomic force microscopy-based single-cell force spectroscopy and Monte Carlo simulations to investigate the similarities and differences of adhesion to hydrophilic and hydrophobic surfaces. Our results reveal that binding to both types of surfaces is mediated by thermally fluctuating cell wall macromolecules that behave differently on each type of substrate: on hydrophobic surfaces, many macromolecules are involved in adhesion, yet only weakly tethered, leading to high variance between individual bacteria, but low variance between repetitions with the same bacterium. On hydrophilic surfaces, however, only few macromolecules tether strongly to the surface. Since during every repetition with the same bacterium different macromolecules bind, we observe a comparable variance between repetitions and different bacteria. We expect these findings to be of importance for the understanding of the adhesion behaviour of many bacterial species as well as other microorganisms and even nanoparticles with soft, macromolecular coatings, used e.g. for biological diagnostics.

Zn- or Cu-containing CaP-Based Coatings Formed by Micro-Arc Oxidation on Titanium and Ti-40Nb Alloy: Part II-Wettability and Biological Performance

This work describes the wettability and biological performance of Zn- and Cu-containing CaP-based coatings prepared by micro-arc oxidation on pure titanium (Ti) and novel Ti-40Nb alloy. Good hydrophilic properties of all the coatings were demonstrated by the low contact angles with liquids, not exceeding 45°. An increase in the applied voltage led to an increase of the coating roughness and porosity, thereby reducing the contact angles to 6° with water and to 17° with glycerol. The free surface energy of 75 ± 3 mJ/m² for all the coatings were determined. Polar component was calculated as the main component of surface energy, caused by the presence of strong polar PO₄³⁻ and OH⁻ bonds. In vitro studies showed that low Cu and Zn amounts (~0.4 at.%) in the coatings promoted high motility of human adipose-derived multipotent mesenchymal stromal cells (hAMMSC) on the implant/cell interface and subsequent cell ability to differentiate into osteoblasts. In vivo study demonstrated 100% ectopic bone formation only on the surface of the CaP coating on Ti. The Zn- and Cu-containing CaP coatings on both substrates and the CaP coating on the Ti-40Nb alloy slightly decreased the incidence of ectopic osteogenesis down to 67%. The MAO coatings showed antibacterial efficacy against Staphylococcus aureus and can be arranged as follows: Zn-CaP/Ti > Cu-CaP/TiNb, Zn-CaP/TiNb > Cu-CaP/Ti.

Mechanical properties and biocompatibility of titanium with a high oxygen concentration for dental implants

In order to improve the strength of commercially pure Ti (CP-Ti) for oral implants, the high oxygen content Ti (HOC-Ti) was prepared via powder metallurgy. Its composition and mechanical properties were then characterized. After surface treatment by sandblasting and acid etching (SLA), the surface morphology, wettability and roughness of the HOC-Ti and CP-Ti sample were examined. In an in vitro test that followed an evaluation of the protein adsorption capacity of HOC-Ti, the mouse preosteoblast cells were inoculated onto the specimens to evaluate their biocompatibility, in comparison with those of CP-Ti. The oxygen concentration of the HOC-Ti increased to 0.62 wt%, which is higher than the 0.26 wt% of the CP-Ti, while their compositions and microstructures were very similar. The tensile and compressive yield strength of the HOC-Ti (800 MPa) was improved significantly in comparison to that of the CP-Ti (530 MPa). After surface treatment, a unique structure of micropores with a diameter of 380 nm was observed on the entire surface of the HOC-Ti that facilitates cell adhesion and proliferation. The wettability of the HOC-Ti was obviously superior (p < 0.05). The in vitro study showed that the MC3T3-E1 cells inoculated on the surface of HOC-Ti exhibited a homogeneous microstructure, and the viability was higher than that of the control group on days 4 and 7 (p < 0.05). In addition, the number and differentiation activity of cells that adhered to the surface of the HOC-Ti increased significantly on day 7 (p < 0.05). The experimental results showed that, in view of its mechanical properties and biocompatibility, HOC-Ti is superior to CP-Ti and is promising for oral implant applications.

The Impact of Bioactive Surfaces in the Early Stages of Osseointegration: An In Vitro Comparative Study Evaluating the HAnano® and SLActive® Super Hydrophilic Surfaces

There is an increased effort on developing novel and active surfaces in order to accelerate their osteointegration, such as nanosized crystalline hydroxyapatite coating (HAnano®). To better understand the biological behavior of osteoblasts grown on HAnano® surface, the set of data was compared with SLActive®, a hydrophilic sandblasted titanium surface. Methodologically, osteoblasts were seeded on both surfaces up to 72 hours, to allow evaluating cell adhesion, viability, and set of genes encoding proteins related with adhesion, proliferation, and differentiation. Our data shows HAnano® displays an interesting substrate to support cell adhesion with typical spread morphologic cells, while SLActive®-adhering cells presented fusiform morphology. Our data shows that the cellular adhesion mechanism was accompanied with upexpression of integrin β1, Fak, and Src, favoring the assembling of focal adhesion platforms and coupling cell cycle progression (upmodulating of Cdk2, Cdk4, and Cdk6 genes) in response to HAnano®. Additionally, both bioactive surfaces promoted osteoblast differentiation stimulus, by activating Runx2, Osterix, and Alp genes. Although both surfaces promoted Rankl gene expression, Opg gene expression was higher in SLActive® and this difference reflected on the Rankl/Opg ratio. Finally, Caspase1 gene was significantly upmodulated in response to HAnano® and it suggests an involvement of the inflammasome complex. Collectively, this study provides enough evidences to support that the nanohydroxyapatite-coated surface provides the necessary microenvironment to drive osteoblast performance on dental implants and these stages of osteogenesis are expected during the early stages of osseointegration.

Tissue Integration and Biological Cellular Response of SLM-Manufactured Titanium Scaffolds

Background: SLM (Selective Laser Melting)–manufactured Titanium (Ti) scaffolds have a significant value for bone reconstructions in the oral and maxillofacial surgery field. While their mechanical properties and biocompatibility have been analysed, there is still no adequate information regarding tissue integration. Therefore, the aim of this study is a comprehensive systematic assessment of the essential parameters (porosity, pore dimension, surface treatment, shape) required to provide the long-term performance of Ti SLM medical implants. Materials and methods: A systematic literature search was conducted via electronic databases PubMed, Medline and Cochrane, using a selection of relevant search MeSH terms. The literature review was conducted using the preferred reporting items for systematic reviews and meta-analysis (PRISMA). Results: Within the total of 11 in vitro design studies, 9 in vivo studies, and 4 that had both in vitro and in vivo designs, the results indicated that SLM-generated Ti scaffolds presented no cytotoxicity, their tissue integration being assured by pore dimensions of 400 to 600 µm, high porosity (75–88%), hydroxyapatite or SiO2–TiO2 coating, and bioactive treatment. The shape of the scaffold did not seem to have significant importance. Conclusions: The SLM technique used to fabricate the implants offers exceptional control over the structure of the base. It is anticipated that with this technique, and a better understanding of the physical interaction between the scaffold and bone tissue, porous bases can be tailored to optimize the graft’s integrative and mechanical properties in order to obtain structures able to sustain osseous tissue on Ti.

Effect of insertion factors on dental implant insertion torque/energy-experimental results

Anchorage of dental implants is quantified with a mechanical engagement to insertion, for example maximum insertion torque (MIT) and insertion energy (IE). Good anchorage of dental implants highly correlates to positive clinical outcomes. However, it is still unclear how bone density, drill protocol, surface finish and cutting flute affect anchorage. In this study, effects of the insertion factors on both MIT and IE were investigated using a full-factorial experiment at two levels: bone surrogate density (0.32 g/cm³ versus 0.48 g/cm³), drill protocol (Ø2.4/2.8 versus Ø2.8/3.2 mm), implant surface finish (machined versus anodized surface) and cutting flute (with versus without). Osteotomies were prepared on rigid polyurethane foam blocks with dimensions of 40 × 40 × 8 mm. Screw shaped dental implants with variable tapered body were consecutively inserted into and removed from the polyurethane foam blocks three times under constant axial displacement and rotational speed. Axial force and torque were recorded synchronously. Insertion energy was calculated from the area under the torque-displacement curve. In this study, we found the main insertion mechanics were thread forming for the first insertion. For the second and third insertions, the main mechanics shifted to thread tightening. Maximum insertion torque (MIT) responded differently to the four insertion factors in comparison to IE. Bone surrogate density, drill protocol and surface finish had the largest main effects for first MIT. For the first IE, drill protocol, surface finish and cutting flute were significant contributors. These results suggest that MIT and IE are influenced by different mechanics: the first MIT and the first IE were sensitive to thread tighten and forming, respectively. Together MIT and IE provide a complete assessment of dental implant anchorage.

A hierarchical nanostructural coating of amorphous silicon nitride on polyetheretherketone with antibacterial activity and promoting responses of rBMSCs for orthopedic applications

Silicon nitride (SN) with good osteoconductivity has been introduced as an implantable biomaterial for joint replacement and interbody fusion devices. In this study, SN was coated on a polyetheretherketone (PEEK) surface by inductively coupled plasma-enhanced chemical vapor deposition (ICPECVD). The results showed that a dense coating (thickness of about 500 nm) of amorphous SN was closely combined with a PEEK substrate (PKSN) with a binding strength of 6.88 N. In addition, the coating surface showed hierarchical nanostructures containing many spherical bulges (sizes about 150 nm), which were composed of many small humps (sizes about 10 nm). Moreover, the roughness, hydrophilicity, surface energy, surface charge and adsorption of bovine serum albumin (BSA) of PKSN were obviously higher than those of PEEK. After immersion into simulated body fluid (SBF), the Si ions were gradually released from PKSN into SBF and a weak alkaline environment was created. Antibacterial experiments showed that PKSN exhibited a greater antibacterial activity than that of PEEK. Moreover, compared with PEEK, PKSN significantly promoted adhesion, proliferation, differentiation and expression of osteogenic related genes of the rat bone marrow stromal cells (rBMSCs). In conclusion, the SN coating of PKSN with hierarchical nanostructures exhibited excellent antibacterial activity and cytocompatibility, which would make it a great candidate for orthopedic applications.

State of the Art on Biomaterials for Soft Tissue Augmentation in the Oral Cavity. Part II: Synthetic Polymers-Based Biomaterials

Most of the polymers used as biomaterials for scaffolds are naturally occurring, synthetic biodegradable, and synthetic non-biodegradable polymers. Since synthetic polymers can be adapted for obtaining singular desired characteristics by applying various fabrication techniques, their use has increased in the biomedical field, in dentistry in particular. The manufacturing methods of these new structures include many processes, such as electrospinning, 3D printing, or the use of computer-aided design/computer-aided manufacturing (CAD/CAM). Synthetic polymers show several drawbacks that can limit their use in clinical applications, such as the lack of cellular recognition, biodegradability, and biocompatibility. Moreover, concerning biodegradable polymers, the time for matrix resorption is not predictable, and non-resorbable matrices are preferred for soft tissue augmentation in the oral cavity. This review aimed to determine a new biomaterial to offset the present shortcomings in the oral environment. Researchers have recently proposed a novel non-resorbable composite membrane manufactured via electrospinning that has allowed obtaining remarkable in vivo outcomes concerning angiogenesis and immunomodulation throughout the polarization of macrophages. A prototype of the protocol for in vitro and in vivo experimentation with hydrogels is explained in order to encourage innovation into the development of promising biomaterials for soft tissue augmentation in the near future.

Controlling osteoblast morphology and proliferation via surface micro-topographies of implant biomaterials

Current research on surface modifications has yielded advanced implant biomaterials. Various implant surface modifications have been shown to be promising in improving bone target cell response, but more comprehensive studies whether certain implant surface modifications can directly target cell behavioural features such as morphogenesis and proliferation are needed. Here, we studied the response of primary alveolar bone cells on various implant surface modifications in terms of osteoblast morphology and proliferation in vitro. Analyses of surface modifications led to surface-related test parameters including the topographical parameters micro-roughness, texture aspect and surface enlargement as well as the physicochemical parameter surface wettability. We compared osteoblast morphology and proliferation towards the above-mentioned parameters and found that texture aspect and surface enlargement but not surface roughness or wettability exhibited significant impact on osteoblast morphology and proliferation. Detailed analysis revealed osteoblast proliferation as a function of cell morphology, substantiated by an osteoblast size- and morphology-dependent increase in mitotic activity. These findings show that implant surface topography controls cell behavioural morphology and subsequently cell proliferation, thereby opening the road for cell instructive biomaterials.

Interactions of Osteoprogenitor Cells with a Novel Zirconia Implant Surface

Background: This study compared the in vitro response of a mouse pre-osteoblast cell line on a novel sandblasted zirconia surface with that of titanium. Material and Methods: The MC3T3-E1 subclone 4 osteoblast precursor cell line was cultured on either sandblasted titanium (SBCpTi) or sandblasted zirconia (SBY-TZP). The surface topography was analysed by three-dimensional laser microscopy and scanning electron microscope. The wettability of the discs was also assessed. The cellular response was quantified by assessing the morphology (day 1), proliferation (day 1, 3, 5, 7, 9), viability (day 1, 9), and migration (0, 6, 24 h) assays. Results: The sandblasting surface treatment in both titanium and zirconia increased the surface roughness by rendering a defined surface topography with titanium showing more apparent nano-topography. The wettability of the two surfaces showed no significant difference. The zirconia surface resulted in improved cellular spreading and a significantly increased rate of migration compared to titanium. However, the cellular proliferation and viability noted in our experiments were not significantly different on the zirconia and titanium surfaces. Conclusions: The novel, roughened zirconia surface elicited cellular responses comparable to, or exceeding that, of titanium. Therefore, this novel zirconia surface may be an acceptable substitute for titanium as a dental implant material.

Bioactive-Enhanced Polyetheretherketone Dental Implant Materials: Mechanical Characterization and Cellular Responses

The aim of this study was to characterize the mechanical properties of a bioactive-modified polyetheretherketone (PEEK) manufacturing approach for dental implants and to compare the in vitro biological behavior with titanium alloy (Ti6Al4V) as the reference. PEEK, PEEK with 5% hydroxyapatite (HA), PEEK with 5% beta-tricalcium phosphate (βTCP), and Ti6Al4V discs were produced using hot pressing technology to create a functionally graded material (FGM). Surface roughness values (Ra, Rz), water contact angle, shear bond strength, and Vickers hardness tests were performed. Human osteoblasts and gingival fibroblasts bioactivity was evaluated by a resazurin-based method, alkaline phosphatase activity (ALP), and confocal laser scanning microscopy (CLSM) images of fluorescent-stained fibroblasts. Morphology and cellular adhesion were confirmed using field emission gun-scanning electron microscopy (FEG-SEM). Group comparisons were tested using analysis of variance (Tukey post hoc test), α = .05. All groups presented similar roughness values (P &gt; .05). Ti6Al4V group was found to have the highest contact angle (P &lt; .05). Shear bond strength and Vickers hardness of different PEEK materials were similar (P &gt; .05); however, the mean values in the Ti6Al4V group were significantly higher when compared with those of the other groups (P &lt; .05). Cell viability and proliferation of osteoblast and fibroblast cells were higher in the PEEK group (P &lt; .05). PEEK-βTCP showed the highest significant ALP activity over time (P &lt; .05 at 14 days of culture). An enhanced bone and soft-tissue cell behavior on pure PEEK was obtained to the gold standard (Ti6Al4V) with equivalent roughness. The results substantiate the potential role of chemical composition rather than physical properties of materials in biological responses. The addition of 5% HA or βTCP by FGM did not enhance PEEK mechanical properties or periodontal cell behavior.

Gingival fibroblasts behavior on bioactive zirconia and titanium dental implant surfaces produced by a functionally graded technique

Adding a biological apatite layer to the implant surface enhances bone healing around the implant.