Biomaterials, Current Strategies, and Novel Nano-Technological Approaches for Periodontal Regeneration

Role of bioglass in enamel remineralization: Existing strategies and future prospects-A narrative review

Enamel, once formed, loses the ability to regenerate due to the loss of the formative ameloblasts. It is subjected to constant damaging events due to exposure to external agents and oral microbiomes. An enamel remineralization process targets to replenish the lost ionic component of the enamel through a multitude of methods. Enamel remineralization is highly challenging as it has a complex organized hierarchical microstructure. Hydroxyapatite nanocrystals of the enamel vary in size and orientation along alignment planes inside the enamel rod. The inability of the enamel to remodel unlike other mineralized tissues is another substantial deterrent. One of the well-known biomaterials, bioglass (BG) induces apatite formation on the external surface of the enamel in the presence of saliva or other physiological fluids. Calcium, sodium, phosphate, and silicate ions in BG become responsive in the presence of body fluids, leading to the precipitation of calcium phosphate. Studies have also demonstrated the bactericidal potential of BG against Streptococcus mutans biofilms. The anticariogenicity and antibacterial activity were found to be enhanced when BG was doped with inorganic ions such as F, Ag, Mg, Sr, and Zn. Due to the versatility of BG, it has been combined with a variety of agents such as chitosan, triclosan, and amelogenin to biomimic remineralization process. Key strategies that can aid in the development of contemporary enamel remineralization agents are also included in this review.

Isolation and immunohistochemical characterization of periodontal ligament stem cells: A preliminary study

Context:

It is a known fact that periodontal tissue regeneration can be achieved by the use of periodontal ligament stem cells (PDLSCs). Current mainstay of periodontal treatment is focusing on stem cell tissue engineering as an effective therapy, making it important to isolate PDLSCs from periodontal tissues.

Aims:

The present research endeavor was undertaken to elucidate a technique for isolating PDLSCs for in vivo reconstructing the natural PDL tissue.

Settings and Design:

The study design involves In vitro prospective study.

Materials and Methods:

Premolar teeth were extracted from 12 patients who were under orthodontic treatment. PDL cells were scraped from their roots. Using 10 ml of Dulbecco's modified Eagle's medium with pH 7.2, the specimens of the periodontal tissue were transferred to laboratory where cell culture was done. Isolated stem cells were grown on 24-well microtiter plates-containing cover slips. They were incubated overnight at approximately 37°C in 95% air and 5% humidification. Anti-CD 45, CD73, CD90, CD105, and CD146 antibodies were used. After staining, cells were observed under phase-contrast microscopy and in inverted microscope.

Results:

The cells showed a marked growth and 90% confluence at day 6. Cells presented thin and long fibroblastic spindle morphology. Isolated PDLSCs showed colony-forming ability at the 14^th day after seeding. Immunohistochemical staining of PDLSCs showed positive uptake for CD146, CD90, CD73, CD105, and negative uptake for CD45.

Conclusions:

The human PDLSCs can be clearly isolated and characterized by using CD90, CD73, CD146, and CD105 markers of stem cells.

Hyaluronan as a Prominent Biomolecule with Numerous Applications in Medicine

Hyaluronan (HA) is a natural glycosaminoglycan present in many tissues of all vertebrates. HA has various biological functions, which are dependent on its molar mass. High-molar-mass HA has anti-angiogenic, immunosuppressive and anti-inflammatory properties, while low-molar-mass HA has opposite effects. HA has also antioxidative properties, however on the other hand it can be readily degraded by reactive oxygen species. For many years it has been used in treatment of osteoarthritis, cosmetics and in ophthalmology. In the last years there has been a growing interest of HA to also be applied in other fields of medicine such as skin wound healing, tissue engineering, dentistry and gene delivery. In this review we summarize information on modes of HA administration, properties and effects of HA in various fields of medicine including recent progress in the investigation of HA.

Barrier membranes for tissue regeneration in dentistry

Background: In dentistry, barrier membranes are used for guided tissue regeneration (GTR) and guided bone regeneration (GBR). Various membranes are commercially available and extensive research and development of novel membranes have been conducted. In general, membranes are required to provide barrier function, biosafety, biocompatibility and appropriate mechanical properties. In addition, membranes are expected to be bioactive to promote tissue regeneration.

Objectives: This review aims to organize the fundamental characteristics of the barrier membranes that are available and studied for dentistry, based on their components.

Results: The principal components of barrier membranes are divided into nonbiodegradable and biodegradable materials.

Nonbiodegradable membranes are manufactured from synthetic polymers, metals or composites of these materials. The first reported barrier membrane was made from expanded polytetrafluoroethylene (e-PTFE). Titanium has also been applied for dental regenerative therapy and shows favorable barrier function. Biodegradable membranes are mainly made from natural and synthetic polymers. Collagens are popular materials that are processed for clinical use by cross-linking. Aliphatic polyesters and their copolymers have been relatively recently introduced into GTR and GBR treatments. In addition, to improve the tissue regenerative function and mechanical strength of biodegradable membranes, inorganic materials such as calcium phosphate and bioactive glass have been incorporated at the research stage.

Conclusions: Currently, there are still insufficient guidelines for barrier membrane choice in GTR and GBR, therefore dentists are required to understand the characteristics of barrier membranes.

Functionalization with a Polyphenol-Rich Pomace Extract Empowers a Ceramic Bone Filler with In Vitro Antioxidant, Anti-Inflammatory, and Pro-Osteogenic Properties

Oral diseases and periodontitis in particular are a major health burden worldwide, because of their association with various systemic diseases and with conditions such as peri-implantitis. Attempts have been made over the years to reverse bone loss due to the host disproportionate inflammatory response and to prevent failure of dental implants. To this end, the use of biomaterials functionalized with molecules characterized by anti-inflammatory and antioxidant properties could represent a new frontier for regenerating functional periodontal tissues. In this study, a new ceramic granulated biomaterial, named Synergoss Red (SR), functionalized with a polyphenolic mixture extracted from pomace of the Croatina grape variety, is introduced. Following a preliminary in-depth characterization of the extract by HPLC analysis and of the biomaterial surface and composition, we performed evaluations of cytocompatibility and a biological response through in vitro assays. The anti-inflammatory and antioxidant properties of the identified phenolic molecules contained in SR were shown to downregulate inflammation in macrophages, to stimulate in osteoblast-like cells the expression of genes involved in deposition of the early bone matrix, and to mitigate bone remodeling by decreasing the RANKL/OPG ratio. Thanks to its cytocompatibility and assorted beneficial effects on bone regeneration, SR could be considered an innovative regenerative approach in periodontal therapy.

Mimicking the Hierarchical Organization of Natural Collagen: Toward the Development of Ideal Scaffolding Material for Tissue Regeneration

Biological materials found in living organisms, many of which are proteins, feature a complex hierarchical organization. Type I collagen, a fibrous structural protein ubiquitous in the mammalian body, provides a striking example of such a hierarchical material, with peculiar architectural features ranging from the amino acid sequence at the nanoscale (primary structure) up to the assembly of fibrils (quaternary structure) and fibers, with lengths of the order of microns. Collagen plays a dominant role in maintaining the biological and structural integrity of various tissues and organs, such as bone, skin, tendons, blood vessels, and cartilage. Thus, "artificial" collagen-based fibrous assemblies, endowed with appropriate structural properties, represent ideal substrates for the development of devices for tissue engineering applications. In recent years, with the ultimate goal of developing three-dimensional scaffolds with optimal bioactivity able to promote both regeneration and functional recovery of a damaged tissue, numerous studies focused on the capability to finely modulate the scaffold architecture at the microscale and the nanoscale in order to closely mimic the hierarchical features of the extracellular matrix and, in particular, the natural patterning of collagen. All of these studies clearly show that the accurate characterization of the collagen structure at the submolecular and supramolecular levels is pivotal to the understanding of the relationships between the nanostructural/microstructural properties of the fabricated scaffold and its macroscopic performance. Several studies also demonstrate that the selected processing, including any crosslinking and/or sterilization treatments, can strongly affect the architecture of collagen at various length scales. The aim of this review is to highlight the most recent findings on the development of collagen-based scaffolds with optimized properties for tissue engineering. The optimization of the scaffolds is particularly related to the modulation of the collagen architecture, which, in turn, impacts on the achieved bioactivity.

Drug Delivery (Nano)Platforms for Oral and Dental Applications: Tissue Regeneration, Infection Control, and Cancer Management

The oral cavity and oropharynx are complex environments that are susceptible to physical, chemical, and microbiological insults. They are also common sites for pathological and cancerous changes. The effectiveness of conventional locally-administered medications against diseases affecting these oral milieus may be compromised by constant salivary flow. For systemically-administered medications, drug resistance and adverse side-effects are issues that need to be resolved. New strategies for drug delivery have been investigated over the last decade to overcome these obstacles. Synthesis of nanoparticle-containing agents that promote healing represents a quantum leap in ensuring safe, efficient drug delivery to the affected tissues. Micro/nanoencapsulants with unique structures and properties function as more favorable drug-release platforms than conventional treatment approaches. The present review provides an overview of newly-developed nanocarriers and discusses their potential applications and limitations in various fields of dentistry and oral medicine.

Influence of Materials Properties on Bio-Physical Features and Effectiveness of 3D-Scaffolds for Periodontal Regeneration

Periodontal diseases are multifactorial disorders, mainly due to severe infections and inflammation which affect the tissues (i.e., gum and dental bone) that support and surround the teeth. These pathologies are characterized by bleeding gums, pain, bad breath and, in more severe forms, can lead to the detachment of gum from teeth, causing their loss. To date it is estimated that severe periodontal diseases affect around 10% of the population worldwide thus making necessary the development of effective treatments able to both reduce the infections and inflammation in injured sites and improve the regeneration of damaged tissues. In this scenario, the use of 3D scaffolds can play a pivotal role by providing an effective platform for drugs, nanosystems, growth factors, stem cells, etc., improving the effectiveness of therapies and reducing their systemic side effects. The aim of this review is to describe the recent progress in periodontal regeneration, highlighting the influence of materials' properties used to realize three-dimensional (3D)-scaffolds, their bio-physical characteristics and their ability to provide a biocompatible platform able to embed nanosystems.

Biocompatibility of nanomaterials and their immunological properties

Nanomaterials (NMs) have revolutionized multiple aspects of medicine by enabling novel sensing, diagnostic, and therapeutic approaches. Advancements in processing and fabrication have also allowed significant expansion in the applications of the major classes of NMs based on polymer, metal/metal oxide, carbon, liposome, or multi-scale macro-nano bulk materials. Concomitantly, concerns regarding the nanotoxicity and overall biocompatibility of NMs have been raised. These involve putative negative effects on both patients and those subjected to occupational exposure during manufacturing. In this review, we describe the current state of testing of NMs including those that are in clinical use, in clinical trials, or under development. We also discuss the cellular and molecular interactions that dictate their toxicity and biocompatibility. Specifically, we focus on the reciprocal interactions between NMs and host proteins, lipids, and sugars and how these induce responses in immune and other cell types leading to topical and/or systemic effects.

Gum Tragacanth (GT): A Versatile Biocompatible Material beyond Borders

The use of naturally occurring materials in biomedicine has been increasingly attracting the researchers’ interest and, in this regard, gum tragacanth (GT) is recently showing great promise as a therapeutic substance in tissue engineering and regenerative medicine. As a polysaccharide, GT can be easily extracted from the stems and branches of various species of Astragalus. This anionic polymer is known to be a biodegradable, non-allergenic, non-toxic, and non-carcinogenic material. The stability against microbial, heat and acid degradation has made GT an attractive material not only in industrial settings (e.g., food packaging) but also in biomedical approaches (e.g., drug delivery). Over time, GT has been shown to be a useful reagent in the formation and stabilization of metal nanoparticles in the context of green chemistry. With the advent of tissue engineering, GT has also been utilized for the fabrication of three-dimensional (3D) scaffolds applied for both hard and soft tissue healing strategies. However, more research is needed for defining GT applicability in the future of biomedical engineering. On this object, the present review aims to provide a state-of-the-art overview of GT in biomedicine and tries to open new horizons in the field based on its inherent characteristics.

In vitro and in vivo evaluation of a biomimetic scaffold embedding silver nanoparticles for improved treatment of oral lesions

BACKGROUND

New materials are currently designed for efficient treatment of oral tissue lesions by guided tissue regeneration. The aim of this study was to develop a multifunctional 3D hybrid biomaterial consisting of extracellular matrix components, collagen, chondroitin 4-sulfate and fibronectin, functionalised with silver nanoparticles, intended to improve periodontitis treatment protocols.

METHODS

Structural observations were performed by autometallography, scanning and transmission electron microscopy. In vitro tests of 3D constructs of embedded gingival fibroblasts within hybrid biomaterial were performed by MTS and Live/Dead assays. Genotoxicity was assessed by comet assay. In vivo experiments using chick embryo chorioallantoic membrane (CAM) assay analysed the degradation and nanoparticles release, but also angiogenesis, new tissue formation in 3D constructs and the regenerative potential of the hybrid material. Biological activity was investigated in experimental models of inflamed THP-1 macrophages and oral specific bacterial cultures.

RESULTS

Light micrographs showed distribution of silver nanoparticles on collagen fibrils. Scanning electron micrographs revealed a microstructure with interconnected pores, which favoured cell adhesion and infiltration. Cell viability and proliferation were significantly higher within the 3D hybrid biomaterial than in 2D culture conditions, while absence of the hybrid material's genotoxic effect was found. In vivo experiments showed that the hybrid material was colonised by cells and blood vessels, initiating synthesis of new extracellular matrix. Besides the known effect of chondroitin sulfate, incorporated silver nanoparticles increased the anti-inflammatory activity of the hybrid biomaterial. The silver nanoparticles maintained their antibacterial activity even after embedding in the polymeric scaffold and inhibited the growth of F. nucleatum and P. gingivalis.

CONCLUSION

The novel biomimetic scaffold functionalised with silver nanoparticles presented regenerative, anti-inflammatory and antimicrobial potential for oral cavity lesions repair.

Bioactive Materials for Soft Tissue Repair

Over the past decades, age-related pathologies have increased abreast the aging population worldwide. The increased age of the population indicates that new tools, such as biomaterials/scaffolds for damaged tissues, which display high efficiency, effectively and in a limited period of time, for the regeneration of the body's tissue are needed. Indeed, scaffolds can be used as templates for three-dimensional tissue growth in order to promote the tissue healing stimulating the body's own regenerative mechanisms. In tissue engineering, several types of biomaterials are employed, such as bioceramics including calcium phosphates, bioactive glasses, and glass-ceramics. These scaffolds seem to have a high potential as biomaterials in regenerative medicine. In addition, in conjunction with other materials, such as polymers, ceramic scaffolds may be used to manufacture composite scaffolds characterized by high biocompatibility, mechanical efficiency and load-bearing capabilities that render these biomaterials suitable for regenerative medicine applications. Usually, bioceramics have been used to repair hard tissues, such as bone and dental defects. More recently, in the field of soft tissue engineering, this form of scaffold has also shown promising applications. Indeed, soft tissues are continuously exposed to damages, such as burns or mechanical traumas, tumors and degenerative pathology, and, thereby, thousands of people need remedial interventions such as biomaterials-based therapies. It is known that scaffolds can affect the ability to bind, proliferate and differentiate cells similar to those of autologous tissues. Therefore, it is important to investigate the interaction between bioceramics and somatic/stem cells derived from soft tissues in order to promote tissue healing. Biomimetic scaffolds are frequently employed as drug-delivery system using several therapeutic molecules to increase their biological performance, leading to ultimate products with innovative functionalities. This review provides an overview of essential requirements for soft tissue engineering biomaterials. Data on recent progresses of porous bioceramics and composites for tissue repair are also presented.

Synthesis and Characterization of Mesoporous Mg- and Sr-Doped Nanoparticles for Moxifloxacin Drug Delivery in Promising Tissue Engineering Applications

Mesoporous silica-based nanoparticles (MSNs) are considered promising drug carriers because of their ordered pore structure, which permits high drug loading and release capacity. The dissolution of Si and Ca from MSNs can trigger osteogenic differentiation of stem cells towards extracellular matrix calcification, while Mg and Sr constitute key elements of bone biology and metabolism. The aim of this study was the synthesis and characterization of sol-gel-derived MSNs co-doped with Ca, Mg and Sr. Their physico-chemical properties were investigated by X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray fluorescence spectroscopy (XRF), Brunauer Emmett Teller and Brunauer Joyner Halenda (BET/BJH), dynamic light scattering (DLS) and ζ-potential measurements. Moxifloxacin loading and release profiles were assessed with high performance liquid chromatography (HPLC) cell viability on human periodontal ligament fibroblasts and their hemolytic activity in contact with human red blood cells (RBCs) at various concentrations were also investigated. Doped MSNs generally retained their textural characteristics, while different compositions affected particle size, hemolytic activity and moxifloxacin loading/release profiles. All co-doped MSNs revealed the formation of hydroxycarbonate apatite on their surface after immersion in simulated body fluid (SBF) and promoted mitochondrial activity and cell proliferation.

Tissue Engineering and Three-Dimensional Printing in Periodontal Regeneration: A Literature Review

The three-dimensional printing of scaffolds is an interesting alternative to the traditional techniques of periodontal regeneration. This technique uses computer assisted design and manufacturing after CT scan. After 3D modelling, individualized scaffolds are printed by extrusion, selective laser sintering, stereolithography, or powder bed inkjet printing. These scaffolds can be made of one or several materials such as natural polymers, synthetic polymers, or bioceramics. They can be monophasic or multiphasic and tend to recreate the architectural structure of the periodontal tissue. In order to enhance the bioactivity and have a higher regeneration, the scaffolds can be embedded with stem cells and/or growth factors. This new technique could enhance a complete periodontal regeneration. This review summarizes the application of 3D printed scaffolds in periodontal regeneration. The process, the materials and designs, the key advantages and prospects of 3D bioprinting are highlighted, providing new ideas for tissue regeneration.

Physicochemical Characterization of Five Different Bone Graft Substitutes Used in Periodontal Regeneration: An In Vitro Study

Background:

Periodontal regeneration involves using a variety of bone graft substitutes (BGS) of varying origin and manufacturing processes. These include a wide range of biomaterials that are mainly of two types: the xenografts and alloplasts. The efficacy of these BGS depends upon the physical characteristics such as particle size, porous nature, surface morphology, as well as the chemical characteristics like composition, crystallinity and resorption properties.

Aims:

The present study is a descriptive study that focuses on describing the physicochemical characteristics of five selected commercially available BGS that are frequently used in periodontal regeneration procedures. The BGS studied here included two xenografts (colocast and osseograft) and three alloplasts (B-OstIN, biograft HABG active and biograft HT).

Materials and Methods:

The physical properties of the BGS, including particle size, morphology, and surface topography, were analyzed using SEM. The mineral phases and crystallinity of the BGS were analyzed using XRD.

Results:

The results showed that the xenografts (colocast and osseograft) had minimal mineral composition and crystalline structure. The physical properties such as surface roughness and porosity were less compared to alloplastic materials. The alloplasts (B-OstIN, biograft HABG and biograft HT) that had different chemical compositions showed varying physical and crystalline properties. Biograft HT showed a superior porous scaffold architecture among all BGS studied.

Conclusion:

It is important for a clinician to have a thorough understanding about the physicochemical characteristics of BGS they use in periodontal regeneration. The xenografts evaluated here had minimal physical and crystalline properties. Among the alloplasts studied, biograft HT showed superior physicochemical properties, while the presence of bioactive glass in biograft HABG enhanced regeneration.

Copper-containing bioactive glasses and glass-ceramics: From tissue regeneration to cancer therapeutic strategies

Copper is one of the most used therapeutic metallic elements in biomedicine, ranging from antibacterial approaches to cancer theranostics. This element could be easily incorporated into different types of biomaterials; specifically, copper-doped bioactive glasses (BGs) provide great opportunities for biomedical engineers and clinicians as regards their excellent biocompatibility and regenerative potential. Although copper-incorporated BGs are mostly used in bone tissue engineering, accelerated soft tissue healing is achievable, too, with interesting potentials in wound treatment and skin repair. Copper can modulate the physico-chemical properties of BGs (e.g., reactivity with bio-fluids) and improve their therapeutic potential. Improving cell proliferation, promoting angiogenesis, reducing or even prohibiting bacterial growth are counted as prominent biological features of copper-doped BGs. Recent studies have also suggested the suitability of copper-doped BGs in cancer photothermal therapy (PTT). However, more research is needed to determine the extent to which copper-doped BGs are actually applicable for tissue engineering and regenerative medicine strategies in the clinic. Moreover, copper-doped BGs in combination with polymers may be considered in the future to produce relatively soft, pliable composites and printable inks for use in biofabrication.

Weissella cibaria EIR/P2-derived exopolysaccharide: A novel alternative to conventional biomaterials targeting periodontal regeneration

Healing and regeneration of periodontium are considered as a complex physiological process. Therefore, treatments need to be addressed with highly effective components modulating the multiple pathways. In this study, exopolysaccharide (EPS) produced by Weissella cibaria EIR/P2, was partially purified from the culture supernatant and subjected to characterization within the aim of evaluating its potential for periodontal regeneration. High-Performance Liquid Chromatography analysis revealed a single-peak corresponding to the glucose which identified the EPS as dextran. Fourier transform-infrared spectra were also displayed characteristic peaks for polysaccharides. According to the results of gel permeation/size exclusion-chromatography, the molecular mass was determined to be 8 × 10⁶ Da. To clarify its anti-bacterial activity on Streptococcus mutans, effects on viability and biofilm formation was evaluated. At 50 mg/mL, dextran exhibited a bactericidal effect with 70% inhibition on biofilm formation. Besides, dose-dependent antioxidant effects were also detected. The efficacy of dextran in enhancing the viability of human periodontal ligament fibroblast cells (hPDLFCs) was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium-bromide (MTT) assay, and an increase was observed in the viability of hPDLFCs. In conclusion, dextran derived from W. cibaria can be potentially used as a multi-functional bioactive polymer in the design of new therapeutic strategies to promote healing and regeneration of periodontium.

Tooth-Supporting Hard Tissue Regeneration Using Biopolymeric Material Fabrication Strategies

The mineralized tissues (alveolar bone and cementum) are the major components of periodontal tissues and play a critical role to anchor periodontal ligament (PDL) to tooth-root surfaces. The integrated multiple tissues could generate biological or physiological responses to transmitted biomechanical forces by mastication or occlusion. However, due to periodontitis or traumatic injuries, affect destruction or progressive damage of periodontal hard tissues including PDL could be affected and consequently lead to tooth loss. Conventional tissue engineering approaches have been developed to regenerate or repair periodontium but, engineered periodontal tissue formation is still challenging because there are still limitations to control spatial compartmentalization for individual tissues and provide optimal 3D constructs for tooth-supporting tissue regeneration and maturation. Here, we present the recently developed strategies to induce osteogenesis and cementogenesis by the fabrication of 3D architectures or the chemical modifications of biopolymeric materials. These techniques in tooth-supporting hard tissue engineering are highly promising to promote the periodontal regeneration and advance the interfacial tissue formation for tissue integrations of PDL fibrous connective tissue bundles (alveolar bone-to-PDL or PDL-to-cementum) for functioning restorations of the periodontal complex.

Downregulation of miR-184 facilitates osseous differentiation in periodontal ligament stem cells by modulating nuclear factor I-C

Background/purpose

PDLSCs (periodontal ligament stem cells), derived from dental tissues, are candidate cells for regeneration of dental tissues. MiRNAs could regulate osteogenic differentiation and the transformation into osteoblasts. This study was conducted to figure out how miR-184 regulates osteoblastic differentiation in PDLSCs.

Materials and methods

PDLSCs were isolated from premolars, and the osteoblastic differentiation was validated via Alizarin red staining and determination of ALP (alkaline phosphatase) activity. Expression of osteogenic specific genes were evaluated by western blot, and the expression pattern of miR-184 was determined by qRT-PCR. Target gene of miR-184 was then verified by dual luciferase reporter assay.

Results

Osteogenic-induced PDLSCs were successfully established with increased mineral deposition, ALP activity and protein expression of RUNX2 (runt-related transcription factor 2), osterix and BSP (bone sialoprotein). MiR-184 was reduced during osteoblastic differentiation of PDLSCs, and over-expression of miR-184 suppressed osteoblastic differentiation, as evidenced by reduction in mineral deposition, ALP activity and protein expression of RUNX2, osterix and BSP. MiR-184 could target NFI-C (nuclear factor I-C), and inhibit NFI-C expression in PDLSCs. NFI-C was enhanced during osteoblastic differentiation of PDLSCs, suggesting negative correlation with miR-184. Forced NFI-C expression promoted osteoblastic differentiation, and counteracted with the suppressive effects of miR-184 on osteoblastic differentiation.

Conclusion

Downregulation of miR-184 facilitates osteoblastic differentiation in PDLSCs by modulating NFI-C, providing novel therapeutic strategy for regeneration of dental tissues.

Towards 3D Multi-Layer Scaffolds for Periodontal Tissue Engineering Applications: Addressing Manufacturing and Architectural Challenges

Reduced periodontal support, deriving from chronic inflammatory conditions, such as periodontitis, is one of the main causes of tooth loss. The use of dental implants for the replacement of missing teeth has attracted growing interest as a standard procedure in clinical practice. However, adequate bone volume and soft tissue augmentation at the site of the implant are important prerequisites for successful implant positioning as well as proper functional and aesthetic reconstruction of patients. Three-dimensional (3D) scaffolds have greatly contributed to solve most of the challenges that traditional solutions (i.e., autografts, allografts and xenografts) posed. Nevertheless, mimicking the complex architecture and functionality of the periodontal tissue represents still a great challenge. In this study, a porous poly(ε-caprolactone) (PCL) and Sr-doped nano hydroxyapatite (Sr-nHA) with a multi-layer structure was produced via a single-step additive manufacturing (AM) process, as a potential strategy for hard periodontal tissue regeneration. Physicochemical characterization was conducted in order to evaluate the overall scaffold architecture, topography, as well as porosity with respect to the original CAD model. Furthermore, compressive tests were performed to assess the mechanical properties of the resulting multi-layer structure. Finally, in vitro biological performance, in terms of biocompatibility and osteogenic potential, was evaluated by using human osteosarcoma cells. The manufacturing route used in this work revealed a highly versatile method to fabricate 3D multi-layer scaffolds with porosity levels as well as mechanical properties within the range of dentoalveolar bone tissue. Moreover, the single step process allowed the achievement of an excellent integrity among the different layers of the scaffold. In vitro tests suggested the promising role of the ceramic phase within the polymeric matrix towards bone mineralization processes. Overall, the results of this study demonstrate that the approach undertaken may serve as a platform for future advances in 3D multi-layer and patient-specific strategies that may better address complex periodontal tissue defects.

Evaluation of Osteogenic/Cementogenic Modulating Potential of PAI-1 Transfected Media for Stem Cells

AIM OF THE STUDY

In vitro evaluation of the effects of plasminogen activator inhibitor-1 (PAI-1) transfected-conditioned media (P-CM) on the differentiation of human periodontal ligament stem cells (hPDLSCs) and human periapical follicular stem cells (hPAFSCs).

MATERIALS AND METHODS

The hPDLSCs and hPAFSCs received from impacted third molars were treated with P-CM and viability, as well as differentiation of the cells were evaluated. Plasmids were constructed according to standard techniques, and all sequences were validated by proper enzyme digestion and sequencing. Chinese hamster ovarian (CHO) cells were transfected with pcDNA3.1-hPAI-1 plasmid to obtain P-CM, followed by western blotting and PAI-1-specific ELISA kit to evaluate the proteins of P-CM. The cell viability of hPDLSCs and hPAFSCs were analyzed using MTT assay after 48 h of incubation. Alizarin red S staining was performed to evaluate the differentiation of hPDLSCs and hPAFSCs. The reverse transcription-polymerase chain reaction was used to observe the expression levels of osteogenic/cementogenic marker genes. The human cytokine antibody array was applied for further analysis of cytokine expression in P-CM.

RESULTS

P-CM significantly promoted the differentiation of hPDLSCs and hPAFSCs and upregulated the expression of osteogenic/cementogenic marker genes in vitro. Furthermore, rhPAI-1 promoted mineralized nodules formation of hPDLSCs and hPAFSCs, and we identified that other proteins, RANTES and IL-6, were highly expressed in P-CM.

CONCLUSIONS

P-CM promoted the differentiation of hPDLSCs and hPAFSCs by upregulating the expression of RANTES and IL-6, and interaction between PAI-1 and RANTES/IL-6 signaling may be involved in P-CM-induced osteogenic/cementogenic differentiation.

Zinc-/copper-substituted dicalcium silicate cement: advanced biomaterials with enhanced osteogenesis and long-term antibacterial properties

The development of bioactive Ca-silicate-based cements which may simultaneously suppress infection is promising for periapical therapy or alveolar bone defect repair. While these treatments are usually effective in the short term, many of these cements have not been designed to have an affinity with dental tissue in a prolonged anti-infectious manner and are only high alkaline in the early stages. This can lead to less favorable long-term outcomes, such as in bone repair or secondary therapy. Inspired by the strong antibacterial activity of zinc and copper ions, we developed a nonstoichiometric dicalcium silicate (C₂S) substituted by 5% or 10% Zn or Cu to endow it with appropriate multifunctions. It was found that the foreign ion substitution could inhibit free CaO content and increase the pH value in the initial ∼6 h. The C₂S cement only showed antibacterial activity in the early stage (6-72 h), but the C₂S displayed appreciable long-term antibacterial potential against P. aeruginosa, E. faecalis and E. coli (>6 h) and S. aureus (>72 h). Moreover, the enhanced new bone regeneration by Zn substitution in C₂S was confirmed in a maxillofacial bone defect model in rabbits. The increases in new bone formation adjacent to C₂S-10Zn and C₂S after 16 weeks of implantation were 32% and 20%, respectively. And the Tb.N values in the C₂S-10Zn and C₂S-10Cu groups (∼5.7 and 4.9 mm^-1) were over two-fold higher than in the C₂S group (∼2.0 mm^-1). It is considered that Zn- or Cu-substitution in C₂S is promising for applications to infectious bone repair.

Nanotechnology Scaffolds for Alveolar Bone Regeneration

In oral biology, tissue engineering aims at regenerating functional tissues through a series of key events that occur during alveolar/periodontal tissue formation and growth, by means of scaffolds that deliver signaling molecules and cells. Due to their excellent physicochemical properties and biomimetic features, nanomaterials are attractive alternatives offering many advantages for stimulating cell growth and promoting tissue regeneration through tissue engineering. The main aim of this article was to review the currently available literature to provide an overview of the different nano-scale scaffolds as key factors of tissue engineering for alveolar bone regeneration procedures. In this narrative review, PubMed, Medline, Scopus and Cochrane electronic databases were searched using key words like “tissue engineering”, “regenerative medicine”, “alveolar bone defects”, “alveolar bone regeneration”, “nanomaterials”, “scaffolds”, “nanospheres” and “nanofibrous scaffolds”. No limitation regarding language, publication date and study design was set. Hand-searching of the reference list of identified articles was also undertaken. The aim of this article was to give a brief introduction to review the role of different nanoscaffolds for bone regeneration and the main focus was set to underline their role for alveolar bone regeneration procedures.

New Pre-reacted Glass Containing Dental Composites (giomers) with Improved Fluoride Release and Biocompatibility

The aim of the present work was to prepare a series of novel restorative giomers and investigate the morphology, the physico-chemical properties (residual monomer, fluoride release), and the cytotoxicity of the new materials. The experimental giomers were prepared as light-cured pastes by blending different resin matrices comprising aromatic/aliphatic/urethane (di) methacrylates, with hybrid fillers containing pre-reacted glasses (PRGs), a radiopaque glass, and nano fluorhydroxyapatite. Polyalkenoic acids based on acrylic acid/itaconic acid/N-acryloyl -L-leucine modified or not with methacrylic groups, together with a superficially active glass, were used to prepare the PRGs. The fluoride ion release of the experimental giomers was investigated within a period of 60 days of storage in bidistilled water while using a fluoride ion selective electrode. Beautifil II commercial product was used as a reference. Cell cytotoxicity tests were done in vitro, in accordance with ISO 10993-122012 proceedings. Human dermal fibroblasts and umbilical endothelial vein cultures were used. The values that were obtained for cumulative fluoride release for all experimental giomers were higher than for the Beautifil II product, being more than twice the ones that were obtained for the commercial product after 60 days of storage in bidistilled water. The experimental biomaterials showed similar and/or better results when compared to the commercial one; this effect was maintained in all tested conditions.

Alveolar bone repair of rhesus monkeys by using BMP-2 gene and mesenchymal stem cells loaded three-dimensional printed bioglass scaffold

Over the past years, the study about bone tissue engineering in the field of regenerative medicine has been a main research topic. Using three-dimensional (3D) porous degradable scaffold complexed with mesenchymal stem cells (MSCs) and growth factor gene to improve bone tissue repair and regeneration has raised much interest. This study mainly evaluated the osteogenesis of alveolar bone defects of animal in the following experimental groups: sham-operated (SO), 3D printed bioglass (3D-BG), 3D-BG with BMP-2 gene loaded CS (3D-BG + BMP/CS) and 3D-BG with rhesus marrow bone MSCs and BMP/CS (3D-BG + BMP/CS + rBMSCs). Simulated human bone defect with critical size of 10 × 10 × 5 mm were established in quadrumana - rhesus monkeys, and in vivo osteogenesis was characterized by X-ray, micro-Computed Tomography (mCT) and history. Our results revealed that 3D-BG + rBMSCs + BMP/CS scaffold could improve bone healing best by showing its promote osteogenic properties in vivo. Considering the great bone repair capacity of 3D-BG + BMP/CS + rBMSCs in humanoid primate rhesus monkeys, it could be a promising therapeutic strategy for surgery trauma or accidents, especially for alveolar bones defects.

Stem cells in the periodontal ligament differentiated into osteogenic, fibrogenic and cementogenic lineages for the regeneration of the periodontal complex

OBJECTIVE

Human periodontal ligament stem cells (hPDLSCs) are promising for periodontal regeneration. However, to date, there has been no report of hPDLSC differentiation into the fibrogenic lineage. There has been no report demonstrating hPDLSC differentiation into all three (osteogenic, fibrogenic and cementogenic fibrogenic) lineages in the same report. The objectives of this study were to harvest hPDLSCs from the periodontal ligaments (PDL) of the extracted human teeth, and use the same vial of hPDLSCs to differentiate into all three (osteogenic, fibrogenic and cementogenic) lineages for the first time.

METHODS

hPDLSCs were harvested from PDL tissues of the extracted premolars. The ability of hPDLSCs to form bone, cementum and collagen fibers was tested in culture mediums. Gene expressions were analyzed using quantitative real-time polymerase chain reaction (qRT-PCR). Immunofluorescence, alizarin red (ARS), Xylenol orange, picro sirius red staining (PSRS), alcian blue staining (ABS) and alkaline phosphatase (ALP) staining were evaluated.

RESULTS

In osteogenic medium, hPDLSCs had high expressions of osteogenic genes (RUNX2, ALP, OPN and COL1) at 14 and 21 days (15-20 folds of that of control), and produced mineral nodules and ALP activity (5 and 10 folds those of the control). hPDLSCs in fibrogenic medium expressed high levels of PDL fibrogenic genes (COL1, COL3, FSP-1, PLAP-1 and Elastin) at 28 days (20-70 folds of control). They were stained strongly with F-actin and fibronection, and secreted PDL collagen fibers (5 folds of control). hPDLSCs in cementogenic medium showed high expressions of cementum genes (CAP, CEMP1 and BSP) at 21 days (10-15 folds of control) and synthesized mineralized cementum (50 folds via ABS, and 40 folds via ALP staining, compared to those of control).

CONCLUSIONS

hPDLSCs differentiated into bone-, fiber- and cementum-forming cells, with potential for regeneration of periodontium to form the bone-PDL-cementum complex.

Transforming Growth Factor-β3/Chitosan Sponge (TGF-β3/CS) Facilitates Osteogenic Differentiation of Human Periodontal Ligament Stem Cells

Periodontal disease is the main reason for tooth loss in adults. Tissue engineering and regenerative medicine are advanced technologies used to manage soft and hard tissue defects caused by periodontal disease. We developed a transforming growth factor-β3/chitosan sponge (TGF-β3/CS) to repair periodontal soft and hard tissue defects. We investigated the proliferation and osteogenic differentiation behaviors of primary human periodontal ligament stem cells (hPDLSCs) to determine the bioactivity and potential application of TGF-β3 in periodontal disease. We employed calcein-AM/propidium iodide (PI) double labeling or cell membranes (CM)-Dil labeling coupled with fluorescence microscopy to trace the survival and function of cells after implantation in vitro and in vivo. The mineralization of osteogenically differentiated hPDLSCs was confirmed by measuring alkaline phosphatase (ALP) activity and calcium content. The levels of COL I, ALP, TGF-βRI, TGF-βRII, and Pp38/t-p38 were assessed by western blotting to explore the mechanism of bone repair prompted by TGF-β3. When hPDLSCs were implanted with various concentrations of TGF-β3/CS (62.5-500 ng/mL), ALP activity was the highest in the TGF-β3 (250 ng/mL) group after 7 d (p < 0.05 vs. control). The calcium content in each group was increased significantly after 21 and 28 d (p < 0.001 vs. control). The optimal result was achieved by the TGF-β3 (500 ng/mL) group. These results showed that TGF-β3/CS promotes osteogenic differentiation of hPDLSCs, which may involve the p38 mitogen-activated protein kinase (MAPK) signaling pathway. TGF-β3/CS has the potential for application in the repair of incomplete alveolar bone defects.

An enzyme-responsive membrane for antibiotic drug release and local periodontal treatment

Periodontitis is a chronic, destructive inflammatory disease that injures tooth- supporting tissues, eventually leading to tooth loss. Complete eradication of periodontal pathogenic microorganisms is fundamental to allow periodontal healing and commonly precedes periodontal tissue regeneration. To address this challenge, we report a strategy for developing an enzyme-mediated periodontal membrane for targeted antibiotic delivery into infectious periodontal pockets; the unique components of the membrane will also benefit periodontal alveolar bone repair. In this approach, a chitosan membrane containing polyphosphoester and minocycline hydrochloride (PPEM) was prepared. Physical, morphological, and ultrastructural analyses were carried out in order to assess cellular compatibility, drug release and antibacterial activity in vitro. Additionally, the functionality of the PPEM membrane was evaluated in vivo with a periodontal defect model in rats. The results confirm that the PPEM membrane exhibits good physical properties with excellent antibacterial activity and successfully promotes periodontal tissue repair, making it promising for periodontal treatment.

Modifications of Polymeric Membranes Used in Guided Tissue and Bone Regeneration

Guided tissue/bone regeneration (GTR/GBR) is a widely used procedure in contemporary dentistry. To achieve the required results of tissue regeneration, soft tissues that reproduce quickly are separated from the slow-growing bone tissue by membranes. Many types of membranes are currently in use, but none of them fulfil all of the desired features. To address this issue, further research on developing new membranes with better separation characteristics, such as membrane modification, is needed. Many of the current innovative modified materials are still in the phase of in vitro and experimental studies. A collective review on new trends in membrane modification to GTR/GBR is needed due to the widespread use of polymeric membranes and the constant development in the field of dentistry. Therefore, the aim of this review was to present an overview of polymeric membrane modifications to the GTR/GBR reported in the literature. The authors searched databases, including PubMed, SCOPUS, Web of Science, and OVID, for relevant studies that were published during 1999-2019. The following keywords were used: guided tissue regeneration, membranes, coating, and modification. A total of 17 papers were included in this review. Furthermore, the articles were divided into three groups that were based on the type of membrane modification: antibiotic coating, ion-use modifications, and others modifications, thus providing an overview of current existing knowledge in the field and encouraging further research. The results of included studies on modified barrier membranes seem to be promising, both in terms of safety and benefits for patients. However, modifications result in a large spectrum of effects. Further clinical studies are needed on a large group of patients to clearly confirm the effects that were observed in animal and in vitro studies.