Ceramic materials in dentistry: historical evolution and current practice

Dental ceramics are presented within a simplifying framework allowing for facile understanding of their development, composition and indications. Engineering assessments of clinical function are dealt with and literature is reviewed on the clinical behaviour of all-ceramic systems. Practical aspects are presented regarding the choice and use of dental ceramics to maximize aesthetics and durability, emphasizing what we know and how we know it.

Porous polyethylene for tissue engineering applications in diabetic rats treated with calcitonin: Histomorphometric analysis

Purpose: The purpose of this work was to study the bone tissue reaction after porous polyethylene (Polipore) implantation into surgical defects in the parietal bones of rats with streptozotocin-induced diabetes, treated with salmon calcitonin. Materials and Methods: Porous polyethylene implants were placed in bone defects created in 36 adult female rats. The rats were divided into 3 equal groups: diabetic treated with calcitonin (DCa), diabetic (D), and control (C). The animals of the DCa group received applications of salmon calcitonin on alternating days immediately after the surgery until sacrifice. The rats were sacrificed after 15, 30, 60, and 90 days, and the defects were examined histologically and statistically through histomorphometric analysis. Results: Histomorphometric analysis showed that there was no statistically significant difference in the mean quantity of inflammatory cells among all study groups after 15 and 90 days. At 30 days, a statistically significant difference was observed between the D and C groups and the D and DCa groups. At 60 days, there was no statistically significant difference between the D and DCa groups. Discussion: Porous polyethylene can be considered an option for implant material when there are investigations that prove its biocompatibility and stability in the host tissues. Salmon calcitonin positively aided the bone repair and attenuated the inflammatory response until 30 days after the surgery. Conclusion: Porous polyethylene was tolerated by the host tissues in all groups, and moderate chronic inflammatory reaction was observed up to the 90-day period. Salmon calcitonin attenuated the inflammatory response up until 30 days.

The wood for the civil engineering: A proposal of distance education

The majority of the Brazilian schools of Civil Engineering have taught the subject works with wood in the traditional only by disciplines of Metallic Structures and Wood at a topic in the content of the program on disciplines at the Materials of Civil Construction. To extend of the wood studies is being made possible that all the pupils have a wider understanding of this material and its adapted use is the goal of the proposal, that by the means of the education modality e-learning, disclosing the first one: Module I - Introduction to the Study of the Wood. This methodology tries to use the theoretical beddings in projects that are related to the pupil daily tasks and its practical professional. The article presents the theoretical bases of the conception proposal and its structure, and at the conclusions, the problems found during its application are displayed. Basically, the methodology considers that the professor and the pupil must share the learning, and adopt it as main in the interdisciplinary.

Influence of natural weathering on colour stability of materials used for facial prosthesis

Colour stability of resin and silicone is an important factor for longevity of facial prostheses. The aim of this study was to evaluate the colour stability of resins and silicone for facial prostheses. Three brands of acrylic resin and one of facial silicone were evaluated considering pigment incorporation for the colourless materials. Ten samples of each material were fabricated and submitted to measurements of chromatic alteration initially and after 90 and 180 days of weathering natural through visual analysis and spectrophotometry. Data were evaluated by ANOVA and Tukey test (p < 0.05). Statistically significant colour alteration was observed among some materials regardless of the period. The materials did not present a statistical difference between 90 and 180 days except for the pigmented heat-polymerized resin. The colour difference between pigmented Silastic MDX4-4210 and colourless Silastic was statistically significant (p < 0.01) in both periods as well as between pigmented and colourless heat-polymerized resin, and between the resins Rapidaflex and Lentaflex. The visual method demonstrated colour alteration in all materials evaluated during the first 90 days of ageing. All materials exhibited colour alteration due to exposure to environment. © 2012 Informa UK, Ltd.

A priori reformulations for joint rolling-horizon scheduling of materials processing and lot-sizing problem

In many production processes, a key material is prepared and then transformed into different final products. The lot sizing decisions concern not only the production of final products, but also that of material preparation in order to take account of their sequence-dependent setup costs and times. The amount of research in recent years indicates the relevance of this problem in various industrial settings. In this paper, facility location reformulation and strengthening constraints are newly applied to a previous lot-sizing model in order to improve solution quality and computing time. Three alternative metaheuristics are used to fix the setup variables, resulting in much improved performance over previous research, especially regarding the use of the metaheuristics for larger instances. © 2013 Elsevier Ltd. All rights reserved.

Improvements of plasma immersion ion implantation (PIII) and deposition (PIII&D) processing for materials surface modification

Plasma immersion ion implantation (PIII) process is a three dimensional surface modification method that is quite mature and well known to the surface engineering community nowadays, especially to those working in the field of plasma-materials interaction, aiming at both industrial and academic applications. More recently, deposition methods have been added to PIII, the PIII&D, opening possibilities of broader range of applications of these techniques. So, PIII&D is becoming a routine method of surface modification, with the advantage of pushing up the retained dose levels limited by the sputtering due to ion implantation. Therefore, well adherent, thick, three-dimensional films without stress are possible to be achieved, at relatively low cost, using PIII&D. In this paper, we will discuss about a few PIII and PIII&D experiments that have been performed recently to achieve surface improvements in different materials: 1 - high temperature nitrogen PIII in Ti6Al4V alloy in which a deep nitrogen rich treated layer resulted in surface improvements as increase of hardness, corrosion resistance and resistance to wear of the Ti alloy; 2 - nanostructures in ZnO films, obtained by PIII&D of vaporized & ionized Zn source; 3 - combined implantation and deposition of calcium for biomaterial activity of Ti alloy (PIII&D), allowing the growth of hydroxyapatite in a body solution; 4 - magnetron sputtering deposition of Cr that was enhanced by the glow discharge Ar plasma to allow implantation and deposition of Cr on SAE 1070 steel (PIII&D) resulting in surfaces with high resistance to corrosion; and 5 - implantation of nitrogen by ordinary PIII into this Cr film, which improved resistance to corrosion, while keeping the tribological properties as good as for the SAE 1070 steel surface. © 2012 Elsevier B.V.

Nanostructured materials based on mesoporous silica and mesoporous silica/apatite as osteogenic growth peptide carriers

The aim of this work was the preparation of inorganic mesoporous materials from silica, calcium phosphate and a nonionic surfactant and to evaluate the incorporation and release of different concentrations of osteogenic growth peptide (OGP) for application in bone regeneration. The adsorption and release of the labeled peptide with 5,6-carboxyfluorescein (OGP-CF) from the mesoporous matrix was monitored by fluorescence spectroscopy. The specific surface area was 880 and 484 m2 g- 1 for pure silica (SiO) and silica/apatite (SiCaP), respectively; the area influenced the percentage of incorporation of the peptide. The release of OGP-CF from the materials in simulated body fluid (SBF) was dependent on the composition of the particles, the amount of incorporated peptide and the degradation of the material. The release of 50% of the peptide content occurred at around 4 and 30 h for SiCaP and SiO, respectively. In conclusion, the materials based on SiO and SiCaP showed in vitro bioactivity and degradation; thus, these materials should be considered as alternative biomaterials for bone regeneration. © 2013 Elsevier B.V.

Stress analysis in bone tissue around single implants with different diameters and veneering materials: A 3-D finite element study

The aimof this study was to evaluate the stress distribution on bone tissue with a single prosthesis supported by implants of large and conventional diameter and presenting different veneering materials using the 3-D finite elementmethod. Sixteenmodels were fabricated to reproduce a bone block with implants, using two diameters (3.75 × 10 mmand 5.00 × 10 mm), four different veneering materials (composite resin, acrylic resin, porcelain, and NiCr crown), and two loads (axial (200 N) and oblique (100 N)). For data analysis, the maximum principal stress and vonMises criterion were used. For the axial load, the cortical bone in allmodels did not exhibit significant differences, and the trabecular bone presented higher tensile stresswith reduced implant diameter. For the oblique load, the cortical bone presented a significant increase in tensile stress on the same side as the loading for smaller implant diameters. The trabecular bone showed a similar but more discreet trend. There was no difference in bone tissue with different veneering materials. The veneering material did not influence the stress distribution in the supporting tissues of single implant-supported prostheses. The large-diameter implants improved the transference of occlusal loads to bone tissue and decreased stress mainly under oblique loads.Oblique loading was more detrimental to distribution stresses than axial loading. © 2013 Elsevier B.V. All rights reserved.

Bacterial Cellulose/Chondroitin Sulfate for Dental Materials Scaffolds

Bacterial cellulose (BC) has become established as a remarkably versatile biomaterial and can be used in a wide variety of scientific applications, especially for medical devices. In this work, the bacterial cellulose fermentation process is modified by the addition of chondroitin sulfate (1% w/w) to the culture medium before the bacteria are inoculated. Besides, biomimetic precipitation of calcium phosphate of biological interest from simulated body fluid on bacterial cellulose was studied. Chondroitin sulfate influences in bacterial cellulose were analyzed using transmission infrared spectroscopy (FTIR), XRD (X-ray diffraction) and scanning electron microscopy (SEM). FTIR analysis showed interaction between chondroitin sulfate, bacterial cellulose and calcium phosphate and XRD demonstrated amorphous calcium phosphate and carbonated apatite on bacterial cellulose nanocomposites. SEM images confirmed incorporation of calcium phosphate in bacterial celluloe nanocomposite surface and uniform spherical calcium phosphate particles. Future experiments with cells adhesion and viability are in course.

Surface modification of polymeric materials by cold atmospheric plasma jet

In this work we report the surface modification of different engineering polymers, such as, polyethylene terephthalate (PET), polyethylene (PE) and polypropylene (PP) by an atmospheric pressure plasma jet (APPJ). It was operated with Ar gas using 10 kV, 37 kHz, sine wave as an excitation source. The aim of this study is to determine the optimal treatment conditions and also to compare the polymer surface modification induced by plasma jet with the one obtained by another atmospheric pressure plasma source the dielectric barrier discharge (DBD). The samples were exposed to the plasma jet effluent using a scanning procedure, which allowed achieving a uniform surface modification. The wettability assessments of all polymers reveal that the treatment leads to reduction of more than 40 degrees in the water contact angle (WCA). Changes in surface composition and chemical bonding were analyzed by x-ray photoelectron spectroscopy (XPS) and Fourier-Transformed Infrared spectroscopy (FTIR) that both detected incorporation of oxygen-related functional groups. Surface morphology of polymer samples was investigated by Atomic Force Microscopy (AFM) and an increase of polymer roughness after the APPJ treatment was found. The plasma-treated polymers exhibited hydrophobic recovery expressed in reduction of the O-content of the surface upon rinsing with water. This process was caused by the dissolution of low molecular weight oxidized materials (LMWOMs) formed on the surface as a result of the plasma exposure. (C) 2014 Elsevier B.V. All rights reserved.

The physicochemical characterization and in vivo response of micro/nanoporous bioactive ceramic particulate bone graft materials

In this study, the physicochemical characteristics of calcium phosphate based bioactive ceramics of different compositions and blends presenting similar micro/nanoporosity and micrometer scale surface texture were characterized and evaluated in an in vivo model. Prior to the animal experiment, the porosity, surface area, particle size distribution, phase quantification, and dissolution of the materials tested were evaluated. The bone regenerative properties of the materials were evaluated using a rabbit calvaria model. After 2, 4, and 8 weeks, the animals were sacrificed and all samples were subjected to histologic observation and histomorphometric analysis. The material characterization showed that all materials tested presented variation in particle size, porosity and composition with different degrees of HA/TCP/lower stoichiometry phase ratios. Histologically, the calvarial defects presented temporal bone filling suggesting that all material groups were biocompatible and osteoconductive. Among the different materials tested, there were significant differences found in the amount of bone formation as a function of time. At 8 weeks, the micro/nanoporous material presenting similar to 55,TCP:45%,HA composition ratio presented higher amounts of new bone regeneration relative to other blends and a decrease in the amount of soft tissue infiltration. (C) 2014 Elsevier B.V. All rights reserved.

Bacterial Cellulose Nanobiocomposites for Dental Materials Scaffolds

Bacterial cellulose (BC) has become established as a remarkably versatile biomaterial and can be used in a wide variety of scientific applications, especially for medical devices. In this work, the bacterial cellulose fermentation process is modified by the addition of chondroitin sulfate and hyaluronic acid (1% w/w) to the culture medium before the bacteria is inoculated. Besides, biomimetic precipitation of calcium phosphate of biological interest from simulated body fluid on bacterial cellulose was studied. Chondroitin sulfate and hyaluronic acid effects in bacterial cellulose were analyzed using transmission infrared spectroscopy (FTIR), XRD (X-ray diffraction) and scanning electron microscopy (SEM). FTIR analysis showed interaction between bacterial cellulose nanobiocomposites and calcium phosphate. XRD demonstrated amorphous calcium phosphate, carbonated apatite and calcium chloride on bacterial cellulose nanobiocomposites. Monocalcium phosphate monohydrate phase formation [Ca(H2PO4)(2)center dot H2O] are here attested by FTIR, XRD and Ca/P relation.

Biological effects of soft denture reline materials on L929 cells in vitro

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evaluation of roof slope and exposure with different roofing materials in reduced models of animal production facilities in spring and summer

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Interdisciplinary project applied to engineering education: construction of a miniature ceramic industry

The greatest challenge of undergraduate engineering courses is to encourage creativity, cooperation with other students, teamwork, and motivation in the first years of their courses. While students have little or no contact with advanced disciplines, it is very difficult to attract their interests and encourage them to develop the skills in their undergraduate courses. This work aims to achieve these objectives through a mini-factory project involving the construction of a production line of ceramic tiles on a laboratory scale, from the ceramic processing using raw materials to the shipping of the final product. Having been given an established monthly demand for ceramic tiles, the students determined the construction requirements of the mini-factory, as they have created the layout, including the processing equipment, the dimensioning of equipment, and its operational structure. This article intends to describe the successful creation of the ceramic tile mini-factory, including the objectives, benefits, and inherent difficulties of the process and the receptivity of the exercise by the students involved.