Effects of alternatively used thermal treatments on the mechanical and fracture behavior of dental resin composites with varying filler content

The purpose of this study was two-fold: (i) to investigate whether the thermal treatment of direct dental resin composites (RCs) using microwave or autoclave heating cycles would modify the materials' strength as compared to the protocol without heating (control); and (ii) to compare the mechanical performance of direct and indirect RCs. Three RCs (from 3M ESPE) were tested: one indirect (Sinfony); and two direct materials (microhybrid - Filtek Z250; and nanofilled - Filtek Z350). Specimens from the direct RCs were prepared and randomly allocated into three groups according to the thermal treatment (n = 10): Control - no thermal treatment was performed; Microwave - the wet heating was performed using a microwave oven; and Autoclave - the wet heating was performed in an autoclave oven. The indirect RC was prepared following the instructions of the manufacturer. All materials were tested using flexural strength, elastic modulus, work of fracture (Wf), microhardness, and scanning electron microscopy (SEM) analyses. Data were analyzed with ANOVA and Tukey as well as Weibull analysis (α = 0.05). The thermal treatments tended to produce slight changes in the topography of direct RCs, especially by the autoclave' wet heating. Overall, the physico-mechanical properties changed after thermal treatment, although this effect was dependent on the type of RC and on the heating protocol. Sinfony showed the lowest modulus and hardness of the study, although it was the most compliant system (higher work of fracture). The load-deflection ability was also greater for the indirect RC. Reliability of the tested materials was similar among each other (p > 0.05). In conclusion, the alternative thermal treatments suggested here may significantly influence some aspects of the mechanical behavior of dental resin composites, with negative effects relying on both the chemical composition of the restorative material as well as on the wet heating protocol used. Clinicians should be aware of the possible effects that additional wet heating of direct resin composites using microwave or autoclave thermal protocols as performed here could have on the overall fracture and mechanical responses during loading circumstances.

Development of an antibacterial and anti-metalloproteinase dental adhesive for long-lasting resin composite restorations

Despite all the advances in adhesive dentistry, dental bonds are still fragile due to degradation events that start during application of adhesive agents and the inherent hydrolysis of resin-dentin bonds. Here, we combined two outstanding processing methods (electrospinning and cryomilling) to obtain bioactive (antimicrobial and anti-metalloproteinase) fiber-based fillers containing a potent matrix metalloproteinase (MMP) inhibitor (doxycycline, DOX). Poly(ε)caprolactone solutions containing different DOX amounts (0, 5, 25, and 50 wt%) were processed via electrospinning, resulting in non-toxic submicron fibers with antimicrobial activity against Streptococcus mutans and Lactobacillus. The fibers were embedded in a resin blend, light-cured, and cryomilled for the preparation of fiber-containing fillers, which were investigated with antibacterial and in situ gelatin zymography analyzes. The fillers containing 0, 25, and 50 wt% DOX-releasing fibers were added to aliquots of a two-step, etch-and-rinse dental adhesive system. Mechanical strength, hardness, degree of conversion (DC), water sorption and solubility, bond strength to dentin, and nanoleakage analyses were performed to characterize the physico-mechanical, biological, and bonding properties of the modified adhesives. Statistical analyses (ANOVA; Kruskal-Wallis) were used when appropriate to analyze the data (α = 0.05). DOX-releasing fibers were successfully obtained, showing proper morphological architecture, cytocompatibility, drug release ability, slow degradation profile, and antibacterial activity. Reduced metalloproteinases (MMP-2 and MMP-9) activity was observed only for the DOX-containing fillers, which have also demonstrated antibacterial properties against tested bacteria. Adhesive resins modified with DOX-containing fillers demonstrated greater DC and similar mechanical properties as compared to the fiber-free adhesive (unfilled control). Concerning bonding performance to dentin, the experimental adhesives showed similar immediate bond strengths to the control. After 12 months of water storage, the fiber-modified adhesives (except the group consisting of 50 wt% DOX-loaded fillers) demonstrated stable bonds to dentin. Nanoleakage was similar among all groups investigated. DOX-releasing fibers showed promising application in developing novel dentin adhesives with potential therapeutic properties and MMP inhibition ability; antibacterial activity against relevant oral pathogens, without jeopardizing the physico-mechanical characteristics; and bonding performance of the adhesive.

Biofilms of cellulose and hydroxyapatite composites: Alternative synthesis process

A new biofilm of cellulose coated with hydroxyapatite particles have been prepared using a simple, fast and low temperature process based on a microwave-assisted hydrothermal synthesis. The cellulose used as matrix of the biocomposite was extracted from banana stems residues. The hydroxyapatite coating was performed using calcium nitrate tetrahydrate, phosphoric acid, and 1,2-ethylenediamine dispersed in a cellulose/water solution, with posterior microwave-assisted hydrothermal synthesis, for 5 min at 140°C. The chemical, structural, thermal, and morphological properties of the composites were investigated by X-ray diffraction, infrared spectroscopy, thermogravimetry and field emission scanning electron microscopy. Results showed that the methodology was effective to produce high quality composites, with good thermal stability. Cell viability tests indicated that the cellulose/Hap films were not cytotoxic.

Antibodies against Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae and influenza virus and their relationships with risk factors, clinical signs and lung lesions in pig farms with one-site production systems in Brazil

A study was conducted on 21 pig herds using one-site production system in the southeast region of Brazil to assess the relationships among serological results for primary pathogens involved in respiratory diseases (Actinobacillus pleuropneumoniae, App; Mycoplasma hyopneumoniae, Mhyo; and swine influenza virus, SIV), cough index, pneumonia index, pleuritis and herd characteristics. The prevalence of antibodies against Mhyo and SIV increased throughout the raising phases, with the highest prevalence in slaughtered pigs (> 40%), while pigs in 65% (14/21) of nurseries demonstrated marked seroprevalence of App that decreased until the day of slaughter. Pleuritis and pulmonary consolidations were recorded in 9.0 and 72.4%, respectively, of the 908 evaluated lungs. Histopathological analysis of the lung lesions revealed suppurative bronchopneumonia in almost half of the lungs (48.9%). Regression analyses were conducted to identify risk factors associated with the cough index; pleuritis; pulmonary consolidation; and App, Mhyo and SIV serological results. All-in-all-out management in nursery buildings reduced the seroprevalence of Mhyo in herds. App seroprevalence was associated with pleuritis, and the presence of cough episodes in growing pigs was associated with SIV seropositivity in nursery pigs.

Macroalgae Extracts From Antarctica Have Antimicrobial and Anticancer Potential

Background: Macroalgae are sources of bioactive compounds due to the large number of secondary metabolites they synthesize. The Antarctica region is characterized by extreme weather conditions and abundant aggregations of macroalgae. However, current knowledge on their biodiversity and their potential for bio-prospecting is still fledging. This study evaluates the antimicrobial and cytotoxic activity of different extracts of four macroalgae (Cystosphaera jacquinotii, Iridaea cordata, Himantothallus grandifolius, and Pyropia endiviifolia) from the Antarctic region against cancer and non-cancer cell lines.

Methods: The antimicrobial activity of macroalgae was evaluated by the broth microdilution method. Extracts were assessed against Staphylococcus aureus ATCC 19095, Enterococcus faecalis ATCC 4083, Escherichia coli ATCC29214, Pseudomonas aeruginosa ATCC 9027, Candida albicans ATCC 62342, and the clinical isolates from the human oral cavity, namely, C. albicans (3), C. parapsilosis, C. glabrata, C. lipolytica, and C. famata. Cytotoxicity against human epidermoid carcinoma (A-431) and mouse embryonic fibroblast (NIH/3T3) cell lines was evaluated with MTT colorimetric assay.

Results: An ethyl acetate extract of H. grandifolius showed noticeable antifungal activity against all fungal strains tested, including fluconazole-resistant samples. Cytotoxicity investigation with a cancer cell line revealed that the ethyl acetate extract of I. cordata was highly cytotoxic against A-431 cancer cell line, increasing the inhibitory ratio to 91.1 and 95.6% after 24 and 48 h exposure, respectively, for a concentration of 500 μg mL⁻¹. Most of the algal extracts tested showed little or no cytotoxicity against fibroblasts.

Conclusion: Data suggest that macroalgae extracts from Antarctica may represent a source of therapeutic agents.

HIGHLIGHTS

Different macroalgae samples from Antarctica were collected and the lyophilized biomass of each macroalgae was extracted sequentially with different solvents

The antimicrobial and anticancer potential of macroalgae extracts were evaluated

Ethyl acetate extract of H. grandifolius showed noticeable antifungal activity against all the fungal strains tested, including fluconazole-resistant samples

Ethyl acetate extract of I. cordata was highly cytotoxic against the A-431 cancer cell line

Most of the algal extracts tested showed little or no cytotoxicity against normal cell lines

Histological Evaluation of Bone Repair with Hydroxyapatite: A Systematic Review

The aim of this study was to evaluate the morphological bone response in animal experiments by applying hydroxyapatite grafts in critical and non-critical size bone defects. Current report followed the guidelines established by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Animal experiments were selected by assessing repair of bone defects with hydroxyapatite as bone graft and with blood clot only as control. Eight articles were identified in specialized literature and included in the meta-analysis. Statistical analysis was carried out with a random-effect model (p = 0.05). Subgroup analyses were further performed to investigate bone repair in critical and non-critical bone defects. Comprehensive analysis of bone repair outcome showed a statistically significant difference between hydroxyapatite and blood clot control (p < 0.05). Subgroup analyses showed statistically significant difference for critical bone defects (p < 0.05). No statistically significant difference was reported in non-critical bone defects (p > 0.05). Although animal studies revealed a high risk of bias and results should be interpreted with caution, the literature suggests that non-critical bone defects may heal spontaneously and without the need of a bone graft. Conversely, when critical-size defects are present, the use of hydroxyapatite bone graft improves the bone repair process.

Current trends and future perspectives of dental pulp capping materials: A systematic review

To systematically review the literature to analyze the current trends and future perspectives of dental pulp capping materials through an analysis of scientific and technological data. This study is reported in accordance with the PRISMA Statement. Nine databases were screened: PubMed (MedLine), Lilacs, IBECS, BBO, Web of Science, Scopus, SciELO, Google Scholar, and The Cochrane Library. Additionally, the following patent applications were searched online in Questel Orbit (Paris, France), USPTO, EPO, JPO, INPI, and Patentscope databases. A total of 716 papers and 83 patents were included. Calcium hydroxide was the main type of material studied, especially for direct pulp capping, followed by MTA. Patents related to adhesives or resins increased from 1998 e 2008, while in the last years, a major increase was observed in bioactive materials (containing bioactive proteins), materials derived from MTA (calcium silicate, calcium phosphate and calcium aluminate-based cements) and MTA. It was possible to obtain a scientific and technological overview of pulp capping materials. MTA has shown favorable results in vital pulp therapy that seem to surpass the disadvantages of calcium hydroxide. Recent advances in bioactive materials and those derived from MTA have shown promising results that could improve biomaterials used in vital pulp treatments. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1358-1368, 2018.

Comparative Effectiveness of Dental Anatomy Carving Pedagogy: A Systematic Review

The aim of this study was to review the effectiveness of methods used for teaching dental anatomy carving to dental students in operative dentistry as evaluated in published studies. This systematic review is described in accordance with the PRISMA statement. Two independent reviewers performed a systematic literature search of research published from January 1945 until May 2014. Seven databases were screened: MedLine (PubMed), Lilacs, IBECS, Web of Science, Scopus, SciELO, and The Cochrane Library. After removing duplicates, only studies using dental carving to assess the practical knowledge of anatomy were selected. The tabulated data were organized by title of article, names of authors, number of students assessed, assessment method, material used, groups tested, main results, and conclusions. The methodology quality was assessed according to the Cochrane Handbook for Systematic Reviews of Interventions. Initially, 2,258 studies were identified in all databases. Five articles met the eligibility criteria and were included in this review. According to these studies, the geometric method, teaching step-by-step along with the teacher, and adjuvant methods such as the use of tutors and teaching through digital media with DVDs proved to be effective in improving learning. There is no standard technique that is widely accepted for the teaching of dental carving, nor is there an appropriately validated method of evaluation to verify whether the teaching methods used are effective for the acquisition of skills and expertise in dental anatomy by students.

Aliphatic fatty acids and esters: inhibition of growth and exoenzyme production of Candida, and their cytotoxicity in vitro: anti-Candida effect and cytotoxicity of fatty acids and esters

The secretion of extracellular phospholipases and proteinases of Candida has been described as a relevant virulence factor in human infections. Aliphatic fatty acids have antimicrobial properties, but the mechanism by which they affect the virulence factors of microorganisms, such as Candida, is still unclear, and there are a few reports about their toxicity. The current study investigated the in vitro antifungal activity, exoenzyme production and cytotoxicity of some aliphatic fatty acids and their ester derivatives against the Candida species. The minimum inhibitory concentration and minimum fungicidal concentrations of aliphatic medium-chain fatty acids, methyl and ethyl esters were performed using the CLSI M27-A3 method and the cytotoxicity assay was performed according to ISO 10993-5. The influence of these compounds in the inhibition of the production of hydrolytic enzymes, phospholipases and proteinases by Candida was also investigated. Data analysis was performed using the one-way ANOVA method (p≤0.05). In relation to the MIC against Candida species, the fatty acid with the best result was Lauric acid, although its ester derivatives showed no activity. The inhibition of phospholipase production was more significant than the inhibition of proteinase production by Candida. Tested fatty acids revealed more than 80% cell viability in their MIC concentrations. Additionally, a cell viability of 100% was reported at concentrations of anti-enzymatic effect. Therefore, the potential use of these fatty acids could be the basis for more antimicrobial tests.

Evaluation of Alzheimer's disease by analysis of MR images using multilayer perceptrons and committee machines

Alzheimer's disease is the most common cause of dementia, yet hard to diagnose precisely without invasive techniques, particularly at the onset of the disease. This work approaches image analysis and classification of synthetic multispectral images composed by diffusion-weighted magnetic resonance (MR) cerebral images for the evaluation of cerebrospinal fluid area and its correlation with the advance of Alzheimer's disease. The MR images were acquired from a unique volunteer with Alzheimer's, using an image system based on a clinical 1.5T tomographer. The classification methods are based on multilayer perceptrons and committee machines and the classification results are used to correlate clinical and imaging findings. The classification results are used to improve the usual analysis of the ADC map.