Bone Grafts and Substitutes in Dentistry: A Review of Current Trends and Developments

After tooth loss, bone resorption is irreversible, leaving the area without adequate bone volume for successful implant treatment. Bone grafting is the only solution to reverse dental bone loss and is a well-accepted procedure required in one in every four dental implants. Research and development in materials, design and fabrication technologies have expanded over the years to achieve successful and long-lasting dental implants for tooth substitution. This review will critically present the various dental bone graft and substitute materials that have been used to achieve a successful dental implant. The article also reviews the properties of dental bone grafts and various dental bone substitutes that have been studied or are currently available commercially. The various classifications of bone grafts and substitutes, including natural and synthetic materials, are critically presented, and available commercial products in each category are discussed. Different bone substitute materials, including metals, ceramics, polymers, or their combinations, and their chemical, physical, and biocompatibility properties are explored. Limitations of the available materials are presented, and areas which require further research and development are highlighted. Tissue engineering hybrid constructions with enhanced bone regeneration ability, such as cell-based or growth factor-based bone substitutes, are discussed as an emerging area of development.     

Preparation of Small‐Diameter Tissue‐Engineered Vascular Grafts Electrospun from Heparin End‐Capped PCL and Evaluation in a Rabbit Carotid Artery Replacement Model

Aiming to construct small diameter (ID <6 mm) off‐the‐shelf tissue‐engineered vascular grafts, the end‐group heparinizd poly(ε‐caprolactone) (PCL) is synthesized by a three‐step process and then electrospun into an inner layer of double‐layer vascular scaffolds (DLVSs) showing a hierarchical double distribution of nano‐ and microfibers. Afterward, PCL without the end‐group heparinization is electrospun into an outer layer. A steady release of grafted heparin and the existence of a glycocalyx structure give the grafts anticoagulation activity and the conjugation of heparin also improves hydrophilicity and accelerates degradation of the scaffolds. The DLVSs are evaluated in six rabbits via a carotid artery interpositional model for a period of three months. All the grafts are patent until explantation, and meanwhile smooth endothelialization and fine revascularization are observed in the grafts. The composition of the outer layer of scaffolds exhibits a significant effect on the aneurysm dilation after implantation. Only one aneurysm dilation is detected at two months and no calcification is formed in the follow‐up term. How to prevent aneurysms remains a challenging topic.     

基于离子交换跃迁模型和实验法对离子液体Walden乘积的研究

提出了关于离子液体的新理论——离子交换跃迁模型,通过理论推导得出1：1型离子液体的Walden乘积仅取决于离子对和离子簇直径的统计平均值,即离子液体的阴阳离子结构不同,Walden乘积不同。为了验证模型的正确性,本文合成8种N-烷基-吡啶二氰胺类和N-烷基-咪唑丝氨酸类离子液体,利用上述离子液体的电导率和动力粘度的实验值及文献数据,计算了33种离子液体的Walden乘积。通过比较发现,不同离子液体的Walden乘积不同,即对于离子液体来说,Walden乘积是它的特征物理量。     

Characterization and Optimization of Polymeric Bispicolamine Chelating Resin: Performance Evaluation via RSM Using Copper in Acid Liquors as a Model Substrate through Ion Exchange Method

Advanced technologies of electronics industries have led to environmental contamination concerns, especially waste print circuit boards containing a very high concentration of copper (II) ions, which can be discharged in wastewater containing many contaminated metals. A low pH is a necessity for treating industrial wastewater containing heavy metals to meet engineering process design. A novel polymeric bispicolamine chelating resin, Dowex-M4195, was applied as an alternative for investigating the behavior of copper (II) in acidic solution via an ion exchange method in a batch experiment system. Characterization of physical and chemical properties before and after ion exchange were also explored through BET, SEM-EDX, FTIR and XRD. Response surface methodology was also applied for optimization of copper (II) removal capacity using design of experiment for selective chelating resin at a low pH. The results indicate that H⁺ Dowex-M4195 chelating resin had a high-carbon content and specific surface area of >64% and 26.5060 m²/g, respectively. It was predominantly macropore porous in nature due to the N₂ gas adsorption isotherm and exhibited type IV with insignificant desorption hysteresis loop of H1-type. It was spherical and cylindrical. After the ion exchange process of copper (II)-loaded H⁺ Dowex-M4195, the specific surface area and total pore volume decreased by about 17.82% and 5.39%, respectively, as compared to H⁺ Dowex-M4195. Hysteresis loop, isotherm and pore size distribution were also similar. Regarding the functional group, the surface morphology and crystalline structures of H⁺ Dowex-M4195 showed copper (II) compound based on the structure of chelating resin that confirmed effective ion exchange behavior. The design of optimization indicated that copper (II) removal capacity of about 31.33 mg/g was achieved, which could be obtained at 6.96 h, pH of 2 (a desirable low pH), dose of 124.13 mg and concentration of 525.15 mg/L. The study indicated that the H⁺ Dowex-M4195 (which is commercially available on the market) can successfully be applied as an alternative precursor through the ion exchange method for further reuse and regeneration of the copper (II) in the electronic waste industries and other wastewater applications needed to respond the policy of biocircular green economy in Thailand.