ABSTRACT
The molecular weight of chitosan (CS) may affect its physical properties and its ability to induce an appropriate host response. The biocompatibilities of CS membranes of low (LMWCS) and high (HMWCS) molecular weight were investigated by inserting these materials into the subcutaneous tissue of rats for 1-28 days and evaluating leukocyte infiltration, granulation tissue, fibrosis, arginase-1 immunostaining, as well as nuclear factor-κB (NF-κΒ) and fibroblast growth factor (FGF)-2 expressions. Both CS membranes induced a peak of leukocyte infiltration on the first day of insertion and stimulated granulation and fibrous tissue generation when compared to control. LMWCS induced more collagen deposition a week earlier, when compared to the control and HMWCS membrane. The membranes also increased arginase-1 immunostaining, a M2 macrophage marker. M2 macrophage is recognized as anti-inflammatory and pro-regenerative. NF-κB is an essential biomarker of the inflammatory process and induces the expression of several pro-inflammatory cytokines. The LMWCS membrane reduced inflammation, as indicated by a reduced nucleus/cytoplasm NF-κB ratio in surrounding tissue from days 7 to 14 when compared to control. On the first day, the expression of FGF-2, a biomarker of inflammatory resolution, was increased in the tissue of the LWMCS group, when compared with HMWCS, which was consistent with the type I collagen deposition. Thus, LWMCS was associated with a prior reduction of the inflammatory response and improved wound healing.
Subject(s)
Biocompatible Materials/chemistry , Biocompatible Materials/toxicity , Chitosan/chemistry , Chitosan/toxicity , Inflammation/chemically induced , Animals , Arginase/metabolism , Collagen/metabolism , Cytokines , Fibroblast Growth Factor 2/metabolism , Fibrosis , Granulation Tissue/pathology , Inflammation/pathology , Leukocytes/pathology , Male , Molecular Weight , NF-kappa B/metabolism , Rats , Rats, Wistar , Wound HealingABSTRACT
Chitosan is a naturally occurring polysaccharide obtained from chitin, present in abundance in the exoskeletons of crustaceans and insects. It has aroused great interest as a biomaterial for tissue engineering on account of its biocompatibility and biodegradation and its affinity for biomolecules. A significant number of research groups have investigated the application of chitosan as scaffolds for tissue regeneration. However, there is a wide variability in terms of physicochemical characteristics of chitosan used in some studies and its combinations with other biomaterials, making it difficult to compare results and standardize its properties. The current systematic review of literature on the use of chitosan for tissue regeneration consisted of a study of 478 articles in the PubMed database, which resulted, after applying inclusion criteria, in the selection of 61 catalogued, critically analysed works. The results demonstrated the effectiveness of chitosan-based biomaterials in 93.4% of the studies reviewed, whether or not combined with cells and growth factors, in the regeneration of various types of tissues in animals. However, the absence of clinical studies in humans, the inadequate experimental designs, and the lack of information concerning chitosan's characteristics limit the reproducibility and relevance of studies and the clinical applicability of chitosan.
Subject(s)
Biocompatible Materials/chemistry , Chitosan/chemistry , Regeneration , Tissue Engineering , Tissue Scaffolds , Animals , Humans , Reproducibility of ResultsABSTRACT
The functional and aesthetic restoration of crown-root fractured anterior teeth with biological width involvement represents a challenge to the clinician, because it requires a multidisciplinary approach. The trans-operative fragment reattachment technique is a feasible and advantageous alternative since it makes it possible to reestablish the original aesthetics and function of the fractured tooth in a single appointment. This work presents the fundamentals of this technique, highlighting its advantages, indications and limitations. The applications of the surgical and restorative procedures are demonstrated by way of a case report.
As fraturas dentais representam as lesões de maior incidência nos traumatismos bucais e causam um impacto negativo sobre a mastigação, fonação e estética. A restauração estético-funcional de dentes anteriores com este tipo de fratura associada a um envolvimento do espaço biológico representa um desafio ao clínico, pois exige uma abordagem multidisciplinar. Nestes casos é necessário realizar um diagnóstico cuidadoso e devem ser observados os diversos aspectos que podem direcionar a seleção da técnica restauradora mais adequada. A técnica de colagem trans-cirúrgica do fragmento dental constitui, atualmente, uma alternativa viável e bastante vantajosa, pois representa um tratamento mais conservador, seguro, rápido e, acima de tudo, eficiente em devolver a forma, o contorno, a translucidez, a textura superficial, o perfil de emergência natural do dente e a harmonia do sorriso em uma única sessão clínica. O presente trabalho se propõe a apresentar, através de um relato de caso clínico, os fundamentos da técnica de colagem de fragmento corono-radicular simultânea ao procedimento de cirurgia periodontal, destacando suas indicações, vantagens e limitações.
ABSTRACT
Os estudos in vitro que avaliam as propriedades mecânicas de materiais odontológicos são ferramentas de grande utilidade em Odontologia, pois auxiliam na previsibilidade do comportamento destes materiais em condições bucais e permitem a elaboração de diretrizes para a prática clínica. O ensaio de microtração constitui-se uma metodologia relativamente recente de ensaio mecânico, que consiste basicamente na divisão do espécime a ser avaliado em corpos-de-prova de dimensões menores, com área transversal de interface adesiva diminuta. Assim, obtêm-se uma área mais homogênea, propiciando uma distribuição de estresse mais uniforme, reduzindo a ocorrência de fraturas coesivas e possibilitando uma mensuração mais fidedigna da resistência adesiva real dos substratos que estão sendo testados, em relação aos ensaios convencionais de tração e cisalhamento. O presente estudo apresenta uma revisão da literatura sobre a metodologia do ensaio de microtração, enfatizando seu mecanismo, suas diversas variações e principais características, suas vantagens, desvantagens, limitações e aplicações em Odontologia.
In vitro researches which evaluate mechanical properties of dental materials are valuable tools in Dentistry since they help to make predictions for clinical practice. The microtensile bond test is a relatively recent mechanical method whose essence is the division of the resin-bonded teeth into diminutive slabs that are trimmed in such a manner that tensile force will be concentrated on the bonded interface during testing, allowing a more uniform stress distribution on the surface and reducing the occurrence of cohesive failures. This work presents a review in the literature focusing the major characteristics, advantages, applications and limitations of microtensile testing in Dentistry.
ABSTRACT
The growing demand for aesthetics and advances in adhesive materials have contributed to the massive increase in the use of indirect adhesiverestorations. Despite the advantages of the indirect technique, one of its disadvantages is the need of using a temporary material between visits, since it may contaminate the dental substrate and affect the bond strength of resinous materials to enamel and dentin. Several authors have investigated this issue, but the results were controversial, especially when temporary cements contained eugenol. This review aims to analyze the literature on this issue and clarify whether temporary cements affect the bond strength of bonding systems to tooth substrates.
A evolução dos sistemas adesivos tem contribuído para o aumento da utilização de restaurações estéticas adesivas indiretas. Todavia, a necessidade de se interpor uma restauração provisória sobre o substrato dental que irá receber uma restauração adesiva indireta representa um risco potencial de contaminação da superfície dental com resíduos de materiais provisórios que ficariam retidos nas irregularidades criadas pelaspontas diamantadas e que poderiam interferir na resistência adesiva dessas restaurações. Diversos estudos que abordam este assunto têm obtido resultados conflitantes sobre os efeitos dos cimentos provisórios na resistência adesiva de materiais resinosos, sobretudo quando estes cimentos contêm eugenol em sua composição, pois este parece interferir no processo de polimerização das resinas compostas. O presente trabalho de revisão de literatura tem o objetivo de investigar, à luz dos resultados e conclusões dos principais estudos, a influência dos diversos cimentos provisórios com e sem eugenol sobre a união entre os materiais resinosos e o substrato dental.
