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Title: From scaffolds to endodontic sealers in dentistry: an in vitro and in vivo approach.
Authors: Pereira, Sara Raquel Gemelgo 
Orientador: Santos, Ana Cristina Aguiar
Keywords: Biocompatibility; Cytotoxicity; Tissue engineering; Endodontics; Scaffolds; Endodontic cements
Issue Date: 1-Oct-2015
Serial title, monograph or event: From scaffolds to endodontic sealers in dentistry: an in vitro and in vivo approach.
Place of publication or event: Coimbra
Abstract: Biocompatibility, described as the ability of a material to fulfil an appropriate response in a given application with the minimum of allergic, inflammatory or toxic reactions when in contact with tissues, is one of the most important characteristic of the materials used in tissue engineering and dentistry. Tissue engineering is a scientific area in continuous expansion. The developments achieved in this area, have significantly contributed for many advances in the field of regenerative medicine. This interdisciplinary science combines the knowledge and experience of several different fields, from materials science to biology, in order to develop synthetic substitutes for human tissues. Aiming at this goal, the most common approach used nowadays involves the seeding of tridimensional porous structures (scaffolds), biocompatible/biodegradable, with donor cells to promote tissue regeneration. This process comprises at least three different stages: the production of the 3D structures, sterilization and cell seeding into scaffolds, and finally the cell culture of the set cell-scaffold. On the other hand, dentistry has currently registered an increasing importance, namely in the endodontic field. Consequently, the development of biocompatible endodontic cements has become of high importance, since these materials can be in direct contact with different cell types, mainly if extrusion of the material to the periapical tissues occurs. There are a variety of commercial root canal cements available, based in different formulations, whose biocompatibility has been studied in vitro and in vivo over the years. However, all the endodontic cements commercially available show some degree of cytotoxicity. Thus, new endodontic cements are emerging, allowing the development of new approaches. Throughout this work it was intended to evaluate the cytotoxicity of two different types of materials: scaffolds and endodontic cements, the latter also called filling cements. Thus, the first goal aimed to evaluate the in vitro cytotoxicity of pure PCL scaffolds and PCL-HA composite scaffolds. For this purpose, scaffolds were produced with different percentages of HA (10% and 25% per weight), and also with different types of HA: synthetic and natural HA (HA S and HA N, respectively). Scaffolds were produced by bioextrusion, a technique controlled by a computer, with different architectural characteristics (300 µm of filament thickness, 300 and 600 µm of pore size and geometries of 0/90º e 0/45º). The second goal of this work aimed to assess the in vitro cytotoxicity regarding three different endodontic cements: an epoxy-resin, AH Plus JetTM, and two based-silicone cements, GuttaFlow®2 and an improved version of the latter material, that is not yet on the market, and thus it will be called “improved” Guttaflow® throughout this work. In order to evaluate the in vitro cytotoxicity of these materials, different volumes of material (0.01, 0.02 and 0.03 mL) and different incubation times (72 and 120 hours) were used. The in vivo cytotoxicity of these materials was also evaluated in a subcutaneous implantation model. Thus, the endodontic cements were placed inside tubes with 8 mm of length, obtained by section of 18 GA (1.3 mm  48 mm) abocats, which were implanted into three quadrants of the dorsum of Wistar rats. The possible reactions of the tissues were evaluated 8 and 30 days after implantation. As control, the reactions induced by abocat tubes without any material inside, were compared during the same time periods (first quadrant). The cytotoxicity assay selected for this work, in order to reach both main goals, was the 3-(4,5- dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, which is based upon the ability of the dehydrogenase enzyme (present in metabolically active cells), to cleave the tetrazolium ring of MTT and convert the yellow water-soluble tetrazolium salt into darkblue/purple formazan crystals. In both cases (studies performed with scaffolds and endodontic cements), the MTT assay was done with macrophages, fibroblasts and co-culture of macrophages and fibroblasts. Regarding the evaluated scaffolds, it was concluded that PCL-HA N composite scaffolds are the ones presenting better in vitro biologic behavior (less cytotoxic). The obtained results also indicate that the scaffolds’ architecture has a leading role in cell-scaffold interaction. Scaffolds with pores of 300 µm and geometry 0/45º show less cytotoxicity, which, in the present study, means that they promote a higher cellular adhesion and proliferation. In what concerns the endodontic cements, the performed in vitro studies allow to conclude that the “improved” GuttaFlow® is the least cytotoxic of the three tested materials, therefore it is the one presenting greater biocompatibility.
Description: Dissertação de Mestrado Integrado em Engenharia Biomédica apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra.
Rights: openAccess
Appears in Collections:UC - Dissertações de Mestrado
FCTUC Física - Teses de Mestrado

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