Structural Characterization and Osseointegrative Properties of Pulsed Laser-Deposited Fluorinated Hydroxyapatite Films on Nano-Zirconia for Implant Applications.

Standard zirconia implants used in restoration still present problems related to inertness and long-term stability. Various physicochemical approaches have been used to modify the implant surfaces to improve early and late bone-to-implant integration; however, no ideal surface modification has been reported. This study used pulsed laser deposition to deposit a fluorinated hydroxyapatite (FHA) film on a zirconia implant to create a biologically active surface. The film prepared was uniform, dense, and crack-free, and exhibited granular surface droplets; it also presented excellent mechanical strength and favorable biological behavior. The FHA-coated implant was implanted on the femur of Sprague-Dawley rats, and various tests and analyses were performed. Results show that the in vitro initial cell activity on the FHA-coated samples was enhanced. In addition, higher alkaline phosphatase activity and cell mineralization were detected in cells cultured on the FHA-coated groups. Further, the newly formed bone volume of the FHA-coated group was higher than that of the bare micro-adjusted composite nano-zirconia (NANOZR) group. Therefore, the FHA film facilitated osseointegration and may improve the long-term survival rates of dental implants, and could become part of a new treatment technology for implant surfaces, promoting further optimization of NANOZR implant materials.

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.

Immunomodulatory Properties and Osteogenic Activity of Polyetheretherketone Coated with Titanate Nanonetwork Structures.

Polyetheretherketone (PEEK) is a potential substitute for conventional metallic biomedical implants owing to its superior mechanical and chemical properties, as well as biocompatibility. However, its inherent bio-inertness and poor osseointegration limit its use in clinical applications. Herein, thin titanium films were deposited on the PEEK substrate by plasma sputtering, and porous nanonetwork structures were incorporated on the PEEK surface by alkali treatment (PEEK-TNS). Changes in the physical and chemical characteristics of the PEEK surface were analyzed to establish the interactions with cell behaviors. The osteoimmunomodulatory properties were evaluated using macrophage cells and osteoblast lineage cells. The functionalized nanostructured surface of PEEK-TNS effectively promoted initial cell adhesion and proliferation, suppressed inflammatory responses, and induced macrophages to anti-inflammatory M2 polarization. Compared with PEEK, PEEK-TNS provided a more beneficial osteoimmune environment, including increased levels of osteogenic, angiogenic, and fibrogenic gene expression, and balanced osteoclast activities. Furthermore, the crosstalk between macrophages and osteoblast cells showed that PEEK-TNS could provide favorable osteoimmunodulatory environment for bone regeneration. PEEK-TNS exhibited high osteogenic activity, as indicated by alkaline phosphatase activity, osteogenic factor production, and the osteogenesis/osteoclastogenesis-related gene expression of osteoblasts. The study establishes that the fabrication of titanate nanonetwork structures on PEEK surfaces could extract an adequate immune response and favorable osteogenesis for functional bone regeneration. Furthermore, it indicates the potential of PEEK-TNS in implant applications.

UV Treatment Improves the Biocompatibility and Antibacterial Properties of Crystallized Nanostructured Titanium Surface.

This study describes the production of a new material composed of pure titanium (Ti) metal with a crystallized nanostructure and investigated whether heat treatment and ultraviolet (UV) irradiation improved its biocompatibility and antibacterial properties. We compared the performance of UV-irradiated and non-irradiated Ti nanosheets (TNS) formed by dark alkaline treatment and heating at 600 °C with that of untreated pure Ti nanostructure (positive control). In vitro and in vivo experiments to assess biocompatibility and effects on cell behavior were performed using human umbilical vein endothelial cells and rat bone marrow cells. The material surface was characterized by X-ray photoelectron spectroscopy (XPS). The antibacterial properties of the irradiated material were evaluated using Staphylococcus aureus, a common pathogenic bacterium. The UV-irradiated TNS exhibited high angiogenic capacity and promoted cell adherence and differentiation relative to the control. Further, surface analysis via XPS revealed a lower C peak for the UV-treated material, indicating a reduced amount of dirt on the material surface. Moreover, UV irradiation decreased the viability of S. aureus on the material surface by stimulating reactive oxygen species production. The biocompatibility and antibacterial properties of the TNS were improved by UV irradiation. Thus, TNS may serve as a useful material for fabrication of dental implants.

Osseointegration of Alkali-Modified NANOZR Implants: An In Vivo Study.

Ingredients and surface modification methods are being continually developed to improve osseointegration of dental implants and reduce healing times. In this study, we demonstrate in vitro that, by applying concentrated alkali treatment to NANOZR with strong bending strength and fracture toughness, a significant improvement in the bone differentiation of rat bone marrow cells can be achieved. We investigated the influence of materials modified with this treatment in vivo, on implanted surrounding tissues using polychrome sequential fluorescent labeling and micro-computer tomography scanning. NANOZR implant screws in the alkali-treated group and the untreated group were evaluated after implantation in the femur of Sprague⁻Dawley male rats, indicating that the amount of new bone in the alkali-modified NANOZR was higher than that of unmodified NANOZR. Alkali-modified NANOZR implants proved to be useful for the creation of new implant materials.

Optimized Surface Characteristics and Enhanced in Vivo Osseointegration of Alkali-Treated Titanium with Nanonetwork Structures.

Alkali-treated titanium (Ti) with a porous, homogeneous, and uniform nanonetwork structure (TNS) that enables establishment of a more rapid and firmer osteointegration than titanium has recently been reported. However, the mechanisms underlying the enhanced osteogenic activity on TNS remains to be elucidated. This study aimed to evaluate the surface physicochemical properties of Ti and TNS, and investigate osteoinduction and osteointegration in vivo. Surface characteristics were evaluated using scanning electron microscopy (SEM), scanning probe microscopy (SPM), and X-ray photoelectron spectrometry (XPS), and the surface electrostatic force of TNS was determined using solid zeta potential. This study also evaluated the adsorption of bovine serum albumin (BSA) and human plasma fibronectin (HFN) on Ti and TNS surfaces using quartz crystal microbalance (QCM) sensors, and apatite formation on Ti and TNS surfaces was examined using a simulated body fluid (SBF) test. Compared with Ti, the newly developed TNS enhanced BSA and HFN absorbance capacity and promoted apatite formation. Furthermore, TNS held less negative charge than Ti. Notably, sequential fluorescence labeling and microcomputed tomography assessment indicated that TNS screws implanted into rat femurs exhibited remarkably enhanced osteointegration compared with Ti screws. These results indicate that alkali-treated titanium implant with a nanonetwork structure has considerable potential for future clinical applications in dentistry and orthopedics.

In Vitro and In Vivo Osteogenic Activity of Titanium Implants Coated by Pulsed Laser Deposition with a Thin Film of Fluoridated Hydroxyapatite.

To enhance biocompatibility, osteogenesis, and osseointegration, we coated titanium implants, by krypton fluoride (KrF) pulsed laser deposition, with a thin film of fluoridated hydroxyapatite (FHA). Coating was confirmed by scanning electron microscopy (SEM) and scanning probe microscopy (SPM), while physicochemical properties were evaluated by attenuated reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Calcium deposition, osteocalcin production, and expression of osteoblast genes were significantly higher in rat bone marrow mesenchymal stem cells seeded on FHA-coated titanium than in cells seeded on uncoated titanium. Implantation into rat femurs also showed that the FHA-coated material had superior osteoinductive and osseointegration activity in comparison with that of traditional implants, as assessed by microcomputed tomography and histology. Thus, titanium coated with FHA holds promise as a dental implant material.

Effect of Amelogenin Coating of a Nano-Modified Titanium Surface on Bioactivity.

The interactions between implants and host tissues depend on several factors. In particular, a growing body of evidence has demonstrated that the surface texture of an implant influences the response of the surrounding cells. The purpose of this study is to develop new implant materials aiming at the regeneration of periodontal tissues as well as hard tissues by coating nano-modified titanium with amelogenin, which is one of the main proteins contained in Emdogain®. We confirmed by quartz crystal microbalance evaluation that amelogenin is easy to adsorb onto the nano-modified titanium surface as a coating. Scanning electron microscopy, scanning probe microscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared spectroscopy analyses confirmed that amelogenin coated the nano-modified titanium surface following alkali-treatment. In vitro evaluation using rat bone marrow and periodontal ligament cells revealed that the initial adhesion of both cell types and the induction of hard tissue differentiation such as cementum were improved by amelogenin coating. Additionally, the formation of new bone in implanted surrounding tissues was observed in in vivo evaluation using rat femurs. Together, these results suggest that this material may serve as a new implant material with the potential to play a major role in the advancement of clinical dentistry.

Bioactivity of NANOZR Induced by Alkali Treatment.

In recent years, zirconia has been a recognized implant material in clinical dentistry. In the present study, we investigated the performance of an alkali-modified ceria-stabilized tetragonal ZrO2 polycrystalline ceramic-based nanostructured zirconia/alumina composite (NANOZR) implant by assessing surface morphology and composition, wettability, bovine serum albumin adsorption rate, rat bone marrow (RBM) cell attachment, and capacity for inducing bone differentiation. NANOZR surfaces without and with alkali treatment served as the control and test groups, respectively. RBM cells were seeded in a microplate with the implant and cultured in osteogenic differentiation medium, and their differentiation was evaluated by measuring alkaline phosphatase (ALP) activity, osteocalcin (OCN) production, calcium deposition, and osteogenic gene expression. The alkali-treated NANOZR surface increased ALP activity, OCN production, calcium deposition, and osteogenesis-related gene expression in attached RBM cells. These data suggest that alkali treatment enhances the osteogenesis-inducing capacity of NANOZR implants and may therefore improve their biointegration into alveolar bone.

Drug-Loadable Calcium Alginate Hydrogel System for Use in Oral Bone Tissue Repair.

This study developed a drug-loadable hydrogel system with high plasticity and favorable biological properties to enhance oral bone tissue regeneration. Hydrogels of different calcium alginate concentrations were prepared. Their swelling ratio, degradation time, and bovine serum albumin (BSA) release rate were measured. Human periodontal ligament cells (hPDLCs) and bone marrow stromal cells (BMSCs) were cultured with both calcium alginate hydrogels and polylactic acid (PLA), and then we examined the proliferation of cells. Inflammatory-related factor gene expressions of hPDLCs and osteogenesis-related gene expressions of BMSCs were observed. Materials were implanted into the subcutaneous tissue of rabbits to determine the biosecurity properties of the materials. The materials were also implanted in mandibular bone defects and then scanned using micro-CT. The calcium alginate hydrogels caused less inflammation than the PLA. The number of mineralized nodules and the expression of osteoblast-related genes were significantly higher in the hydrogel group compared with the control group. When the materials were implanted in subcutaneous tissue, materials showed favorable biocompatibility. The calcium alginate hydrogels had superior osteoinductive bone ability to the PLA. The drug-loadable calcium alginate hydrogel system is a potential bone defect reparation material for clinical dental application.

Effect of denture adhesives on masticatory performance: Multicenter randomized controlled trial.

PURPOSE: The purpose of this study is to investigate the effects of denture adhesives on masticatory performance via a 10-center, parallel, randomized, controlled trial of complete denture wearers in Japan. METHODS: The trial was conducted between September 2013 and October 2016. The inclusion criteria were complete edentulism, willingness to undergo new complete denture treatment, and willingness to return for recall treatment. The exclusion criteria were age 90 years or older, presence of severe systemic illness, inability to understand the questionnaires, wearing metal base complete dentures, denture adhesive user, wearing prosthetics for maxillofacial defects, wearing complete dentures with tissue conditioners, and severe xerostomia. Randomization of the powder-type denture adhesive (powder), cream-type denture adhesive (cream), and control (saline) groups was performed using a sealed envelope system. Masticatory performance was measured using color-changeable chewing gum. Intervention blinding was not feasible. RESULTS: Sixty-seven control, 69 powder, and 64 cream participants are analyzed using the intention-to-treat principle. The participants in all groups show significantly improved masticatory performance at post-intervention (paired t-test with Bonferroni correction P < 0.0001). However, no significant difference in masticatory performance is detected among the three groups (one-way analysis of variance). A significant negative correlation between pre- and post-changes in masticatory performance and intraoral condition scores is observed (Pearson's correlation coefficient, P < 0.0001). CONCLUSIONS: Although denture adhesives improved the masticatory performance of complete denture wearers, their clinical effects are comparable to those of saline solution. The use of denture adhesives is more effective in complete denture wearers with unsatisfactory intraoral conditions.

Effects of denture adhesives on denture retention and occlusal forces in complete denture wearers: A multicenter, randomized controlled trial.

PURPOSE: This study aimed to determine the effects of denture adhesives on denture retention and occlusal force in complete denture wearers in a multicenter, randomized, parallel-group controlled trial. METHODS: Two hundred edentulous patients wearing complete dentures were allocated to three groups: powder-type denture adhesive, cream-type denture adhesive, and control (saline solution). Denture adhesives and saline solution were applied to the dentures for 4 days. The retentive force of the dentures and occlusal force were measured using a force transducer occlusal force meter at baseline and after 4 days of intervention. In addition to between-group comparisons, subgroup analyses of denture retention and occlusal force were performed based on the level of difficulty of the edentulism treatment. The levels were ranked as I (easy), II, III, and IV (difficult). RESULTS: Cream-type denture adhesives significantly improved the retentive force of the dentures (P<0.01) and occlusal force (P<0.05), with no significant differences between baseline and post-intervention forces in the powder-type denture adhesive and control groups. In within-group comparisons, cream-type denture adhesives improved both the retentive and occlusal forces at Level II (P<0.05), and powder-type denture adhesives improved the occlusal force at Level II (P<0.01). CONCLUSIONS: Application of cream-type denture adhesives effectively improves the denture retention and occlusal force in complete denture wearers with a moderate degree of difficulty during edentulism treatment.

Special Issue: Advances in Dental Bio-Nanomaterials.

Recent advances in dental materials involving the development of various biomaterials have been reported. Accordingly, clinicians must incorporate the new dental materials in their practice to respond to the increasing needs of patients. Nanotechnology is defined as a science that deals with nanoscale materials. The use of nanomaterials is gaining popularity in the dental industry for processing and manipulating nanoscale substances in modern dentistry. In this special issue, we invited the submission of several research papers on the development of dental materials. In this general discussion, we briefly explain the relevant research reports with an aim that developments in this field will contribute toward the development of dental care in the future.

Characterization of Hydroxyapatite Film Obtained by Er:YAG Pulsed Laser Deposition on Sandblasted Titanium: An In Vitro Study.

The surface of titanium (Ti) dental implants must be modified to improve their applicability, owing to the biological inertness of Ti. This study aims to use sandblasting as a pretreatment method and prepare a hydroxyapatite (HA) coating on Ti to improve its biocompatibility and induce bone bonding and osteogenesis. In this paper, sandblasted Ti discs were coated with α-tricalcium phosphate (α-TCP) via Er:YAG pulsed laser deposition (Er:YAG-PLD). An HA coating was then obtained via the hydrothermal treatment of the discs at 90 °C for 10 h. The surface characteristics of the samples were evaluated by SEM, SPM, XPS, XRD, FTIR, and tensile tests. Rat bone marrow mesenchymal stem cells were seeded on the HA-coated discs to determine cellular responses in vitro. The surface characterization results indicated the successful transformation of the HA coating with a nanorod-like morphology, and its surface roughness increased. In vitro experiments revealed increased cell attachment on the HA-coated discs, as did the cell morphology of fluorescence staining and SEM analysis; in contrast, there was no increase in cell proliferation. This study confirms that Er:YAG-PLD could be used as an implant surface-modification technique to prepare HA coatings with a nanorod-like morphology on Ti discs.

Characterization of oxidative stress status during diabetic bone healing.

Early events associated with bone healing in patients with type 2 diabetes mellitus appear to be delayed. Hyperglycaemia and an associated increase in oxidative stress are cited as potential factors leading to a change in cellular behaviour. Using an in vivo model monitoring bone formation around implants placed into rat mandibles, we have previously identified that the onset of cell proliferation and osteoblast differentiation are delayed and subsequently prolonged compared with normal bone. This study used the same implant model to characterize oxidative stress biomarkers and primary antioxidant enzyme profiles during diabetic bone healing in vivo. Implants were placed into the sockets of incisors extracted from the mandibles of normal Wistar and diabetic Goto-Kakizaki rats for 3 and 9 weeks after implant insertion. Histochemical analysis confirmed a delay in bone healing around implants in diabetic animals. Immunohistochemical localization of peri-cellular staining for protein carbonyl groups, as a biomarker of oxidized protein content, was slightly higher in diabetic granulation tissue compared with normal tissue. However, no differences were observed in the staining patterns of advanced glycation end products. Minimal differences were observed in the number of cells positive for cytoplasmic superoxide dismutase (SOD)1 or mitochondrial SOD2. Significantly, catalase was absent in diabetic tissues. The results suggest that the oxidative environment in healing bone is differentially affected by hyperglycaemia, particularly in relation to catalase. The significance of these observations for diabetic bone healing is discussed.

Delayed osteoblast differentiation and altered inflammatory response around implants placed in incisor sockets of type 2 diabetic rats.

OBJECTIVE: Central to the process of osseointegration is the recruitment of mesenchymal progenitor cells to the healing site, their proliferation and differentiation to bone synthesising osteoblasts. The process is under the control of pro-inflammatory cytokines and growth factors. The aim of this study was to monitor these key stages of osseointegration and the signalling milieu during bone healing around implants placed in healthy and diabetic bone. METHODS: Implants were placed into the sockets of incisors extracted from the mandibles of normal Wistar and diabetic Goto-Kakizaki rats. Mandibles 1-12 weeks post-insertion of the implant were examined by histochemistry and immunocytochemistry to localise the presence of Stro-1- positive mesenchymal progenitor cells, proliferating cellular nuclear antigen proliferative cells, osteopontin and osteocalcin, macrophages, pro-inflammatory cytokines interleukin (IL)-1ß, IL-6, tumour necrosis factor (TNF)-α and tumour growth factor (TGF)-ß1. Image analysis provided a semi-quantification of positively expressing cells. RESULTS: Histological staining identified a delay in the formation of mineralised bone around implants placed in diabetic animals. Within the diabetic bone, the migration of Stro-1 mesenchymal cells in the healing tissue appeared to be unaffected. However, in the diabetic healing bone, the onset of cell proliferation and osteoblast differentiation were delayed and subsequently prolonged compared with normal bone. Similar patterns of change were observed in diabetic bone for the presence of IL-1ß, TNF-α, macrophages and TGF-ß1. CONCLUSION: The observed alterations in the extracellular presence of pro-inflammatory cytokines, macrophages and growth factors within diabetic tissues that correlate to changes in the signalling milieu, may affect the proliferation and differentiation of mesenchymal progenitor cells in the osseointegration process.

Multivariate analysis reveals oral health-related quality of life of complete denture wearers with denture adhesives: a multicenter randomized controlled trial.

Purpose To investigate the difference in improvement of oral health-related quality of life (OHR-QoL) depending on the oral and denture conditions of a complete denture wearer when using a cream or powder type denture adhesive in a 10-center parallel randomized clinical trial.Methods Two hundred edentulous subjects who wore complete dentures were allocated to each of the three groups according to denture adhesive type: cream, powder, and control (saline solution). The materials were applied to the mucosal surface of the dentures for 4 days, and baseline data and data after the intervention were collected. OHR-QoL was assessed using the Japanese version of the modified Oral Health Impact Profile for Edentulous Patients (OHIP-EDENT-J) scale for outcome. Multivariate analysis was used to investigate improvements in OHR-QoL according to participant characteristics among complete denture wearers using these materials.Results OHIP-EDENT-J scores were significantly decreased in all groups after the intervention (p < 0.05); however, there were no statistically significant differences among the groups. Multiple logistic regression analysis revealed a significant association between the vertical height of the maxillary and mandibular alveolar ridge and OHIP-EDENT-J scores in the cream-type denture adhesive group. In contrast, there were no significant association between participant characteristics and OHIP-EDENT-J scores in the powder-type adhesive and control groups.Conclusions The use of denture adhesives could improve OHR-QoL for complete denture wearers. The cream-type denture adhesives may be expected to improve OHR-QoL in patients with poor residual ridge conditions compared with patients with good residual ridge conditions.

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.

Decontamination of Titanium Surface Using Different Methods: An In Vitro Study.

Contamination of implants is inevitable during different steps of production as well as during the clinical use. We devised a new implant cleaning strategy to restore the bioactivities on dental implant surfaces. We evaluated the efficiency of the Finevo cleaning system, and Ultraviolet and Plasma treatments to decontaminate hydrocarbon-contaminated titanium disks. The surfaces of the contaminated titanium disks cleaned using the Finevo cleaning system were similar to those of the uncontaminated titanium disks in scanning electron microscopy and X-ray photoelectron spectroscopy analysis, but no obvious change in the roughness was observed in the scanning probe microscopy analysis. The rat bone marrow mesenchymal stem cells (rBMMSCs) cultured on the treated titanium disks attached to and covered the surfaces of disks cleaned with the Finevo cleaning system. The alkaline phosphatase activity, calcium deposition, and osteogenesis-related gene expression in rBMMSCs on disks cleaned using the Finevo cleaning system were higher compared to those in the ultraviolet and plasma treatments, displaying better cell functionality. Thus, the Finevo cleaning system can enhance the attachment, differentiation, and mineralization of rBMMSCs on treated titanium disk surfaces. This research provides a new strategy for cleaning the surface of contaminated titanium dental implants and for restoration of their biological functions.

Hierarchical assembly of nanostructured coating for siRNA-based dual therapy of bone regeneration and revascularization.

Advancing bone implant engineering offers the opportunity to overcome crucial medical challenges and improve clinical outcomes. Although the establishment of a functional vascular network is crucial for bone development, its regeneration inside bone tissue has only received limited attention to date. Herein, we utilize siRNA-decorated particles to engineer a hierarchical nanostructured coating on clinically used titanium implants for the synergistic regeneration of skeletal and vascular tissues. Specifically, an siRNA was designed to target the regulation of cathepsin K and conjugated on nanoparticles. The functionalized nanoparticles were assembled onto the bone implant to form a hierarchical nanostructured coating. By regulating mRNA transcription, the coating significantly promotes cell viability and growth factor release related to vascularization. Moreover, microchip-based experiments demonstrate that the nanostructured coating facilitates macrophage-induced synergy in up-regulation of at least seven bone and vascular growth factors. Ovariectomized rat and comprehensive beagle dog models highlight that this siRNA-integrated nanostructured coating possesses all the key traits of a clinically promising candidate to address the myriad of challenges associated with bone regeneration.