Hossein E. Jazayeri

A current overview of materials and strategies for potential use in maxillofacial tissue regeneration.

Tissue regeneration is rapidly evolving to treat anomalies in the entire human body. The production of biodegradable, customizable scaffolds to achieve this clinical aim is dependent on the interdisciplinary collaboration among clinicians, bioengineers and materials scientists. While bone grafts and varying reconstructive procedures have been traditionally used for maxillofacial defects, the goal of this review is to provide insight on all materials involved in the progressing utilization of the tissue engineering approach to yield successful treatment outcomes for both hard and soft tissues. In vitro and in vivo studies that have demonstrated the restoration of bone and cartilage tissue with different scaffold material types, stem cells and growth factors show promise in regenerative treatment interventions for maxillofacial defects. The repair of the temporomandibular joint (TMJ) disc and mandibular bone were discussed extensively in the report, supported by evidence of regeneration of the same tissue types in different medical capacities. Furthermore, in addition to the thorough explanation of polymeric, ceramic, and composite scaffolds, this review includes the application of biodegradable metallic scaffolds for regeneration of hard tissue. The purpose of compiling all the relevant information in this review is to lay the foundation for future investigation in materials used in scaffold synthesis in the realm of oral and maxillofacial surgery.

Development of 3D PCL microsphere/TiO2 nanotube composite scaffolds for bone tissue engineering

In this research, the three dimensional porous scaffolds made of a polycaprolactone (PCL) microsphere/TiO2 nanotube (TNT) composite was fabricated and evaluated for potential bone substitute applications. We used a microsphere sintering method to produce three dimensional PCL microsphere/TNT composite scaffolds. The mechanical properties of composite scaffolds were regulated by varying parameters, such as sintering time, microsphere diameter range size and PCL/TNT ratio. The obtained results ascertained that the PCL/TNT (0.5wt%) scaffold sintered at 60°C for 90min had the most optimal mechanical properties and an appropriate pore structure for bone tissue engineering applications. The average pore size and total porosity percentage increased after increasing the microsphere diameter range for PCL and PCL/TNT (0.5wt%) scaffolds. The degradation rate was relatively high in PCL/TNT (0.5wt%) composites compared to pure PCL when the samples were placed in the simulated body fluid (SBF) for 6weeks. Also, the compressive strength and modulus of PCL and PCL/TNT (0.5wt%) composite scaffolds decreased during the 6weeks of storage in SBF. MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide) assay and alkaline phosphates (ALP) activity results demonstrated that a generally increasing trend in cell viability was observed for PCL/TNT (0.5wt%) scaffold sintered at 60°C for 90min compared to the control group. Eventually, the quantitative RT-PCR data provided the evidence that the PCL scaffold containing TiO2 nanotube constitutes a good substrate for cell differentiation leading to ECM mineralization.

Dental Applications of Natural-Origin Polymers in Hard and Soft Tissue Engineering.

Clinical advances in the treatment of dentoalveolar defects continue to evolve with the introduction of new innovations in regenerative medicine and tissue bioengineering. Recent developments in tissue engineering are aimed at safely and effectively regenerating a damaged or necrotic area by replenishing its cells and increasing surrounding gene expression. Various techniques have successfully given rise to porous scaffolds being used by clinicians to treat the defect and initiate the repair process. Tissue reconstruction using bioengineered scaffolds is advantageous over traditional autografting, since it prevents the instigation of pain and donor site morbidity while ultimately creating both the environment and machinery needed to induce cell proliferation, migration, and reattachment within the affected area. This review article aims to describe and review the available literature regarding the regenerative capacity of natural polymers used for the treatment of dentoalveolar defects. The repair mechanisms, advantages of protein and polysaccharide derivatives, and the potential of stem cell therapy are discussed.

Evaluation of glycated albumin (GA) and GA/HbA1c ratio for diagnosis of diabetes and glycemic control: A comprehensive review

Abstract Diabetes Mellitus (DM) is a group of metabolic diseases characterized by chronic high blood glucose concentrations (hyperglycemia). When it is left untreated or improperly managed, it can lead to acute complications including diabetic ketoacidosis and non-ketotic hyperosmolar coma. In addition, possible long-term complications include impotence, nerve damage, stroke, chronic kidney failure, cardiovascular disease, foot ulcers, and retinopathy. Historically, universal methods to measure glycemic control for the diagnosis of diabetes included fasting plasma glucose level (FPG), 2-h plasma glucose (2HP), and random plasma glucose. However, these measurements did not provide information about glycemic control over a long period of time. To address this problem, there has been a switch in the past decade to diagnosing diabetes and its severity through measurement of blood glycated proteins such as Hemoglobin A1c (HbA1c) and glycated albumin (GA). Diagnosis and evaluation of diabetes using glycated proteins has many advantages including high accuracy of glycemic control over a period of time. Currently, common laboratory methods used to measure glycated proteins are high-performance liquid chromatography (HPLC), immunoassay, and electrophoresis. HbA1c is one of the most important diagnostic factors for diabetes. However, some reports indicate that HbA1c is not a suitable marker to determine glycemic control in all diabetic patients. GA, which is not influenced by changes in the lifespan of erythrocytes, is thought to be a good alternative indicator of glycemic control in diabetic patients. Here, we review the literature that has investigated the suitability of HbA1c, GA and GA:HbA1c as indicators of long-term glycemic control and demonstrate the importance of selecting the appropriate glycated protein based on the patient’s health status in order to provide useful and modern point-of-care monitoring and treatment.

Nanobiomaterials in periodontal tissue engineering

Periodontitis is an inflammatory disease of the gums which spreads and affects the supporting tooth structures possibly leading to the loosening and loss of the tooth. Periodontal tissue engineering is considered a relatively new technique for the stimulation of the periodontal tissue formation using the basics of regenerative medicine. In this method, biodegradable porous scaffolds are employed as a temporary substitution of the injured or lost tissues to facilitate the regeneration process. Scaffolds are usually made of natural or synthetic polymers and ceramics doped with various nanobiomaterials for an intended functionalization. The addition of nanoparticles into the scaffold structure not only enhances the biomineralization potential of the composite scaffolds, but also improves their mechanical properties. Nanosized ceramic particles are of special importance as they mimic the mineral crystal structure of the natural tissues. They have been demonstrated to induce a considerable enhancement in the protein absorption and the cell adhesion compared to their micro-sized counterparts. This chapter reviews different nanobiomaterials employed in periodontal tissue engineering for the effective regeneration of lost tissues and discuss their benefits and drawbacks.

Evaluation of the in vitro biodegradation and biological behavior of poly(lactic-co-glycolic acid)/nano-fluorhydroxyapatite composite microsphere-sintered scaffold for bone tissue engineering

The objective of this research was to study the degradation and biological characteristics of the three-dimensional porous composite scaffold made of poly(lactic-co-glycolic acid)/nano-fluorhydroxyapatite microsphere using sintering method for potential bone tissue engineering. Our previous experimental results demonstrated that poly(lactic-co-glycolic acid)/nano-fluorhydroxyapatite composite scaffold with a ratio of 4:1 sintered at 90ºC for 2 h has the greatest mechanical properties and a proper pore structure for bone repair applications. The weight loss percentage of both poly(lactic-co-glycolic acid)/nano-fluorhydroxyapatite and poly(lactic-co-glycolic acid) scaffolds demonstrated a monotonic trend with increasing degradation time, that is, the incorporation of nano-fluorhydroxyapatite into polymeric scaffold could lead to weight loss in comparison with that of pure poly(lactic-co-glycolic acid). The pH change for composite scaffolds showed that there was a slight decrease until 2 weeks after immersion in simulated body fluid, followed by a significant increase in the pH of simulated body fluid without a scaffold at the end of immersion time. The mechanical properties of composite scaffold were higher than that of poly(lactic-co-glycolic acid) scaffold at total time of incubation in simulated body fluid; however, it should be noted that the incorporation of nano-fluorhydroxyapatite into composite scaffold leads to decline in the relatively significant mechanical strength and modulus during hydrolytic degradation. In addition, MTT assay and alkaline phosphatase activity results defined that a general trend of increasing cell viability was seen for poly(lactic-co-glycolic acid)/nano-fluorhydroxyapatite scaffold sintered by time when compared to control group. Eventually, experimental results exhibited poly(lactic-co-glycolic acid)/nano-fluorhydroxyapatite microsphere-sintered scaffold is a promising scaffold for bone repair.

CHAPTER 8:Smart Biomaterials for Tissue Engineering of Cartilage

Smart materials have made significant changes within the realm of tissue engineering research. Smart biomaterials have the unique ability to respond to their environments, and interact with different biological systems in turn producing specific responses. In this chapter, we focus on the tissue engineering of cartilage with the use of smart materials. Specifically, we will discuss the desired properties of such materials for optimal biological responses and why certain natural and synthetic materials are used. We also examine the use of smart matrices in the context of those that are thermo-responsive, pH-responsive, bioactive agent releasing, and self-assembling matrices. Response to dynamic loading, as well as the use of matrix metalloproteinase and shape-memory systems are explored. Finally, future applications of smart materials within a broad scope are considered.

Oral nerve tissue repair and regeneration

Nerve tissue engineering is a multidisciplinary topic relevant to medicine and dentistry. Repairing nerves with bioengineered scaffolds not only relies on the types of the biomaterials used to produce a mechanically stable and biocompatible environment for regeneration, but also may require the application of stem cells and growth factors to induce differentiation and bioactivity. Multiple techniques have led to development of a number of scaffolds with unique advantages and limitations. Innovations in neural tissue engineering have already yielded positive results in medical capacities, including spinal nerve repair. With the increasing utilization of stem cell therapy and advances in the field of material science, research in neural tissue regeneration in the head and neck region, especially the repair of the trigeminal nerve, has gradually become very prominent. The use of reproducible, rapid, and patient-specific approaches are evolving to treat nerve injuries and reverse sensory and motor deficits, ultimately restoring a functional and healthy patient lifestyle.

Craniofacial surgery, orthodontics, and tissue engineering

Abstract Although bone grafting has been the gold standard for several decades, tissue engineering has been gaining momentum in the fields of craniofacial surgery and orthodontics. In this chapter we highlight the use of state of the art methods and materials, including the use of scaffolds and their ideal properties, as well as the incorporation of stem cells for regeneration of craniofacial structures. Furthermore, we explore the causes of alveolar bone defects, and different methods of repair including the use of guided bone regeneration, use of growth factors and gene therapy. Periodontal ligament tissue engineering is examined throughout this chapter within the scope of orthodontics and dentofacial orthopedics. Finally, we shed light on a relatively novel method that has been discussed in literature known as low-intensity pulsed ultrasound (LIPUS). This approach provides mechanical stimulation to tissues and enhances new blood vessel formation, which is important for the process of integrating newly formed tissues. LIPUS has been shown to reduce root resorption throughout clinical orthodontic treatment as well as increase the efficiency of tooth movement. Limitations along with significant future applications within the realm of craniofacial treatment are discussed.