Accelerating skin regeneration and wound healing by controlled ROS from photodynamic treatment.

Cellular metabolisms produce reactive oxygen species (ROS) which are essential for cellular signaling pathways and physiological functions. Nevertheless, ROS act as "double-edged swords" that have an unstable redox balance between ROS production and removal. A little raise of ROS results in cell proliferation enhancement, survival, and soft immune responses, while a high level of ROS could lead to cellular damage consequently protein, nucleic acid, and lipid damages and finally cell death. ROS play an important role in various pathological circumstances. On the contrary, ROS can show selective toxicity which is used against cancer cells and pathogens. Photodynamic therapy (PDT) is based on three important components including a photosensitizer (PS), oxygen, and light. Upon excitation of the PS at a specific wavelength, the PDT process begins which leads to ROS generation. ROS produced during PDT could induce two different pathways. If PDT produces control and low ROS, it can lead to cell proliferation and differentiation. However, excess production of ROS by PDT causes cellular photo damage which is the main mechanism used in cancer treatment. This review summarizes the functions of ROS in living systems and describes role of PDT in production of controllable ROS and finally a special focus on current ROS-generating therapeutic protocols for regeneration and wound healing.

Biomineralization of three calcium silicate-based cements after implantation in rat subcutaneous tissue.

OBJECTIVES: The aim of this study was to evaluate the dystrophic mineralization deposits from 3 calcium silicate-based cements (Micro-Mega mineral trioxide aggregate [MM-MTA], Biodentine [BD], and EndoSequence Root Repair Material [ESRRM] putty) over time after subcutaneous implantation into rats. MATERIALS AND METHODS: Forty-five silicon tubes containing the tested materials and 15 empty tubes (serving as a control group) were subcutaneously implanted into the backs of 15 Wistar rats. At 1, 4, and 8 weeks after implantation, the animals were euthanized (n = 5 animals/group), and the silicon tubes were removed with the surrounding tissues. Histopathological tissue sections were stained with von Kossa stain to assess mineralization. Scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX) were also used to assess the chemical components of the surface precipitates deposited on the implant and the pattern of calcium and phosphorus distribution at the material-tissue interface. The calcium-to-phosphorus ratios were compared using the non-parametric Kruskal-Wallis test at a significance level of 5%. RESULTS: The von Kossa staining showed that both BD and ESRRM putty induced mineralization starting at week 1; this mineralization increased further until the end of the study. In contrast, MM-MTA induced dystrophic calcification later, from 4 weeks onward. SEM/EDX showed no statistically significant differences in the calcium- and phosphorus-rich areas among the 3 materials at any time point (p > 0.05). CONCLUSIONS: After subcutaneous implantation, biomineralization of the 3-calcium silicate-based cements started early and increased over time, and all 3 tested cements generated calcium- and phosphorus-containing surface precipitates.

Challenges in Three-Dimensional Printing of Bone Substitutes.

Hope is that tissue engineering will provide a solution to meet the growing needs for bone substitutes. Among the potential solutions, three-dimensional (3D) printing is a promising method to fabricate functional bone substitutes especially for treatment of complex and critical-sized bone defects. Despite its encouraging achievements, 3D printing of bone substitutes still faces serious challenges including mechanical strength, shape complexity, optimization of pore parameters, and vascularization. The newer approach, that is, 3D bioprinting, is also confronted with challenges, which have prevented the realization of the dream of fabricating functional patient-specific bone substitutes. This article reviews the major challenges toward 3D printing and bioprinting of bone substitutes and recent studies addressing them. Potential solutions for each challenge and future directions are also provided. Impact Statement This review provides a current overview of the challenges in 3D (bio)printing of bone substitutes and summarizes the potential solutions.

Biomaterials Evaluation: Conceptual Refinements and Practical Reforms.

Regarding the widespread and ever-increasing applications of biomaterials in different medical fields, their accurate assessment is of great importance. Hence the safety and efficacy of biomaterials is confirmed only through the evaluation process, the way it is done has direct effects on public health. Although every biomaterial undergoes rigorous premarket evaluation, the regulatory agencies receive a considerable number of complications and adverse event reports annually. The main factors that challenge the process of biomaterials evaluation are dissimilar regulations, asynchrony of biomaterials evaluation and biomaterials development, inherent biases of postmarketing data, and cost and timing issues. Several pieces of evidence indicate that current medical device regulations need to be improved so that they can be used more effectively in the evaluation of biomaterials. This article provides suggested conceptual refinements and practical reforms to increase the efficiency and effectiveness of the existing regulations. The main focus of the article is on strategies for evaluating biomaterials in US, and then in EU.

Using Enamel Matrix Derivative to Improve Treatment Efficacy in Periodontal Furcation Defects.

PURPOSE: Furcations are complicated periodontal defects. Untreated furcations lead to loss of the involved teeth and supporting tissues. It has been demonstrated that regenerative biomaterials are beneficial in reconstruction of the bone surrounding furcation-affected teeth. These biomaterials range from bone grafts and nonresorbable/resorbable barrier membranes to biologics that are able to trigger inactive regenerative processes in periodontal tissues. Selection of appropriate material(s) to treat furcations is challenging. The aim of this article is to provide a comparative outlook on different biomaterials applicable in regeneration of furcations with a focus on enamel matrix derivative (EMD). METHODS: Scientific databases including PubMed/MEDLINE, ScienceDirect, and EMBASE were searched, and 28 articles were found primarily for this specific study. Full texts were studied to identify relevant studies; 17 studies were excluded because of irrelevancy, while 11 main studies were ultimately selected. Other references have been used for general statements. RESULTS: EMD is a protein complex widely used in the regeneration of different periodontal defects. To assess the effects of EMD for treatment of root furcations, clinical studies involving EMD with and without barrier membranes and bone grafts were selected and compared. Briefly, this study reveals that when EMD is combined with open flap debridement (OFD), guided tissue regeneration (GTR), or bone grafting (BG), the amount of class II furcations converted to class I increases significantly. EMD also reduces tissue swelling and patient discomfort after treatment. CONCLUSIONS: This study provides evidence to find the best combination of biomaterials to treat furcation defects. The best results are obtained if EMD is combined with ß-TCP/HA alloplastic bone grafts.