Abstract:Recently, an increasing amount of research has focused on the biological and mechanical behavior of highly porous structures of metallic biomaterials, as implant materials for dental implants. Particularly, pure titanium and its alloys are typically used due to their outstanding mechanical and biological properties. However, these materials have high stiffness (Young's modulus) in comparison to that of the host bone, which necessitates careful implant design to ensure appropriate distribution of stresses to the adjoining bone, to avoid stress-shielding or overloading, both of which lead to bone resorption. Additionally, many coating and roughening techniques are used to improve cell and bone-bonding to the implant surface. To date, several studies have revealed that porous geometry may be a promising alternative to bulk structures for dental implant applications. This review aims to summarize the evidence in the literature for the importance of porosity in the integration of dental implants with bone tissue and the different fabrication methods currently being investigated. In particular, additive manufacturing shows promise as a technique to control pore size and shape for optimum biological properties. OPEN ACCESSMetals 2015, 5 1903

Dental implants need to support good osseointegration into the surrounding bone for full functionality. Interconnected porous structures have a lower stiffness and larger surface area compared with bulk structures, and therefore are likely to enable better bone-implant fixation. In addition, grading of the porosity may enable large pores for ingrowth on the periphery of an implant and a denser core to maintain mechanical properties. However, given the small diameter of dental implants it is very challenging to achieve gradations in porosity. This paper investigates the use of Selective Laser Melting (SLM) to produce a range of titanium structures with regular and graded porosity using various CAD models. This includes a novel 'Spider Web' design and lattices built on a diamond unit cell. Well-formed interconnecting porous structures were successfully developed in a one-step process. Mechanical testing indicated that the compression stiffness of the samples was within the range for cancellous bone tissue. Characterization by scanning electron microscopy (SEM) and X-ray micro-computed tomography (μCT) indicated the designed porosities were well-replicated. The structures supported bone cell growth and deposition of bone extracellular matrix.Graphical abstract:

Controllable pore size and architecture are essential properties for tissue-engineering scaffolds to support cell ingrowth colonization. To investigate the effect of polyethylene glycol (PEG) addition on porosity and bone-cell behavior, porous polylactic acid (PLA)-PEG scaffolds were developed with varied weight ratios of PLA-PEG (100/0, 90/10, 75/25) using solvent casting and porogen leaching. Sugar 200-300 µm in size was used as a porogen. To assess scaffold suitability for bone tissue engineering, MLO-A5 murine osteoblast cells were cultured and cell metabolic activity, alkaline phosphatase (ALP) activity and bone-matrix production determined using (alizarin red S staining for calcium and direct red 80 staining for collagen). It was found that metabolic activity was significantly higher over time on scaffolds containing PEG, ALP activity and mineralized matrix production were also significantly higher on scaffolds containing 25% PEG. Porous architecture and cell distribution and penetration into the scaffold were analyzed using SEM and confocal microscopy, revealing that inclusion of PEG increased pore interconnectivity and therefore cell ingrowth in comparison to pure PLA scaffolds. The results of this study confirmed that PLA-PEG porous scaffolds support mineralizing osteoblasts better than pure PLA scaffolds, indicating they have a high potential for use in bone tissue engineering applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1334-1340, 2018.

The authors wish to make the following corrections to the citations in the published paper [1].[...]

The successful fabrication of hydroxyapatite-bioactive glass scaffolds using honeycomb extrusion is presented herein. Hydroxyapatite was combined with either 10 wt% stoichiometric Bioglass â (BG1), calcium-excess Bioglass â (BG2) or canasite (CAN). For all composite materials, glass-induced partial phase transformation of the HA into the mechanically weaker b-tricalcium phosphate (TCP) occurred but XRD data demonstrated that BG2 exhibited a lower volume fraction of TCP than BG1. Consequently, the maximum compressive strength observed for BG1 and BG2 were 30.3 AE 3.9 and 56.7 AE 6.9 MPa, respectively, for specimens sintered at 1300°C. CAN scaffolds, in contrast, collapsed when handled when sintered below 1300°C, and thus failed. The microstructure illustrated a morphology similar to that of BG1 sintered at 1200°C, and hence a comparable compressive strength (11.4 AE 3.1 MPa). The results highlight the great potential offered by honeycomb extrusion for fabricating high-strength porous scaffolds. The compressive strengths exceed that of commercial scaffolds, and biological tests revealed an increase in cell viability over 7 days for all hybrid scaffolds. Thus it is expected that the incorporation of 10 wt% bioactive glass will provide the added advantage of enhanced bioactivity in concert with improved mechanical stability. K E Y W O R D SBioglass, canasite, composite, honeycomb extrusion, hydroxyapatite, scaffold

Problem: The commonly used acrylic resins for fabricating denture base suffer from poor mechanical properties. Aim: This study aimed to assess the effect of incorporating Titanium Dioxide (TiO2) nanoparticles (NPs) as a reinforcement agent on the compressive strength of different acrylic denture base materials. Materials and methods: Thirty-two cylindrical specimens (22 mm in height and 12 mm in diameter) were prepared from PMMA resins with and without TiO2 NPs. They were allocated into two main groups according to the materials used such as cold cure and heat cure denture base resins and then divided into two subgroups each containing eight specimens: control (without nanoparticles) and experimental (with 2 wt.% TiO2 NPs). TiO2 NPs were synthesized via a chemical processing route. Particle morphology and size distribution were assessed using SEM and AFM while XRD technique was employed to determine the crystalline structure of the NPs. Compression test was performed on the specimens using a universal Instron testing machine to compare the compressive strength. Results: Size of crystalline TiO2 NPs varied between 40-80 nm. The mean compressive strength for the cold cure acrylic resin (control group) and its nanocomposite (experimental group) were found to be 15.37 MPa and 17.42 MPa while for the heat cure acrylic resin and its nanocomposite were 23.04 MPa and 24.30 MPa. A statistically significant difference was recorded between the compressive strengths of cold cure acrylic resin and its nanocomposite. However, the difference was non-significant in the case of heat cure acrylic resin. Conclusion: The compressive strengths of both cold cure and heat cure acrylic resins increased after the incorporation TiO2 NPs.

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This study aimed to evaluate potential impacts of calcium oxide nanoparticles (CaO-NPs) at different dosages on predentin thickness, number of blood vessels, periodontal ligament thickness, and blood glucose level of Wistar rats. Twelve rats were randomly gathered into four groups, untreated (control) and CaO-NP-treated groups at three concentrations (25, 50, and 100 mg/kg of the body weight) over a period of 60 days. Histological investigation was performed on twenty-four lower incisor teeth extracted from all the tested groups under a light microscope, and an automatic Fujifilm was used to measure the blood glucose level. The results showed that regular nanoparticle treatment significantly increased predentin and periodontal ligament thicknesses, a gradual decrease in vascularization in the pulp tissue, and an increase in the blood glucose level as the dosages of nanoparticles administered to the rats increased. Administration of the CaO-NPs at low dosage (25 mg/kg) could be beneficial for the growth and integrity of teeth and dentinal tissues in rats.