Shrinkage Stress and Temperature Variation in Resin Composites Cured via Different Photoactivation Methods: Insights for Standardisation of the Photopolymerisation.

The literature has shown that there is no consensus regarding the best resin composite photoactivation protocol. This study evaluated the efficiency of the conventional, soft-start, pulse-delay and exponential protocols for photoactivation of resin composites in reducing the shrinkage stress and temperature variation during the photopolymerisation. The photoactivation processes were performed using a photocuring unit and a smartphone app developed to control the irradiance according each photoactivation protocol. These photoactivation methods were evaluated applying photoactivation energies recommended by the resins manufactures. Three brands of resin composites were analysed: Z-250, Charisma and Ultrafill. The cure effectiveness was evaluated through depth of cure experiments. All results were statistically evaluated using one-way and multi-factor analysis of variance (ANOVA). The use of exponential and pulse-delay methods resulted in a significant reduction of the shrinkage stress for all evaluated resins; however, the pulse-delay method required too long a photoactivation time. The increases on the temperature were lower when the exponential photoactivation was applied; however, the temperature variation for all photoactivation protocols was not enough to cause damage in the restoration area. The evaluation of the depth of cure showed that all photoactivation protocols resulted in cured resins with equivalent hardness, indicating that the choice of an alternative photoactivation protocol did not harm the polymerisation. In this way, the results showed the exponential protocol as the best photoactivation technique for practical applications.

Outdoor environment management through air enthalpy analysis.

With the ever-progressing urbanization of human society comes lingering public issues, primarily those related to human health and the need to provide environments where the population can be routinely frequent. Also, the effects of climatic changes tend to aggravate such public health issues, mainly respiratory and cardiac symptoms. As such, analyzing and studying those environments can be crucial for public administrations in the decision-making processes. One such method of analysis involves using an air enthalpy index to profile and provide a picture of stress situations, helping expedite preventive measures and hospital logistics. With that, this study used the enthalpy index as a tool to create a picture of the effect of seasonality on chronic health issues, such as respiratory and cardiac symptoms, for the city of Botucatu, a city with a characteristic tropical altitude climate. It was possible to determine that the air enthalpy profile is consistent throughout the year near the estimated thermal comfort boundaries, with peaks outside in hotter months. The hospitalizations tend to be more numerous during the transition from hot to cold seasons. Simple correlation analysis, along with a t test, provided further insight into the issue, showing strong correlation for pneumonia with the maximum enthalpy variation, which can relate to the heat amount variation in a given location. Also, an agreement was observed between enthalpy and an established thermal sensation index, the heat index, meaning that air enthalpy can be a reliable and simple index for environmental thermal comfort analysis. That being said, further studies are necessary to confirm these findings, considering a longer time frame, more diverse hospitalization data, and other meteorological parameters, like wind speed and precipitation.

Sol-gel based calcium phosphates coatings deposited on binary Ti-Mo alloys modified by laser beam irradiation for biomaterial/clinical applications.

Ti-15Mo alloy samples were irradiated by pulsed Yb: YAG laser beam under air and atmospheric pressure. Calcium phosphate coatings were deposited on the irradiated surfaces by the sol-gel method. The sol was prepared from the precursors Ca (NO3)2.4H2 O and H3 PO4. The modified surfaces were submitted to heat treatment conditions at 350 and 600 °C. The results showed that the two conditions established have a sufficient energy to promote ablation on the laser beam irradiated surfaces. Likewise, it has been demonstrated the processes of fusion and fast solidification from the laser beam irradiation, under ambient atmosphere, inducing the formation of stoichiometric TiO2 and non-stoichiometric titanium oxides, including Ti3O5, TiO, Ti3O and Ti6O with different oxide percentages depending on the fluency used. Besides that, laser modification has allowed a clean and reproducible process, providing no traces of contamination, an important feature for clinical applications. The physico-chemical and morphological properties indicated the formation of a mixture of phases: calcium pyrophosphate, hydroxyapatite and ß-TCP for the procedure (PA: calcination temperature), whereas HA (hydroxyapatite) and ß-TCP (tricalcium phosphate) were obtained by the procedure (PB: calcination temperature). Therefore, it was possible to obtain a Ti-15Mo alloy surface consisted on calcium phosphate ceramics of biological interest using the procedure (PB). Thus, the laser beam irradiation associated to bioactive coatings of calcium phosphates of biological interest have shown to be promising and economically feasible for use in dental and orthopedic implants.

Surface physical chemistry properties in coated bacterial cellulose membranes with calcium phosphate.

Bacterial cellulose has become established as a new biomaterial, and it can be used for medical applications. In addition, it has called attention due to the increasing interest in tissue engineering materials for wound care. In this work, the bacterial cellulose fermentation process was modified by the addition of chondroitin sulfate to the culture medium before the inoculation of the bacteria. The biomimetic process with heterogeneous calcium phosphate precipitation of biological interest was studied for the guided regeneration purposes on bacterial cellulose. FTIR results showed the incorporation of the chondroitin sulfate in the bacterial cellulose, SEM images confirmed the deposition of the calcium phosphate on the bacterial cellulose surface, XPS analysis showed a selective chemical group influences which change calcium phosphate deposition, besides, the calcium phosphate phase with different Ca/P ratios on bacterial cellulose surface influences wettability. XTT results concluded that these materials did not affect significantly in the cell viability, being non-cytotoxic. Thus, it was produced one biomaterial with the surface charge changes for calcium phosphate deposition, besides different wettability which builds new membranes for Guided Tissue Regeneration.

Label-free DNA detection of hepatitis C virus based on modified conducting polypyrrole films at microelectrodes and atomic force microscopy tip-integrated electrodes.

We present a new strategy for the label-free electrochemical detection of DNA hybridization for detecting hepatitis C virus based on electrostatic modulation of the ion-exchange kinetics of a polypyrrole film deposited at microelectrodes. Synthetic single-stranded 18-mer HCV genotype-1-specific probe DNA has been immobilized at a 2,5-bis(2-thienyl)-N-(3-phosphoryl-n-alkyl)pyrrole film established by electropolymerization at the previously formed polypyrrole layer. HCV DNA sequences (244-mer) resulting from the reverse transcriptase-linked polymerase chain reaction amplification of the original viral RNA were monitored by affecting the ion-exchange properties of the polypyrrole film. The performance of this miniaturized DNA sensor system was studied in respect to selectivity, sensitivity, and reproducibility. The limit of detection was determined at 1.82x10(-21) mol L(-1). Control experiments were performed with cDNA from HCV genotypes 2a/c, 2b, and 3 and did not show any unspecific binding. Additionally, the influence of the spacer length of 2,5-bis(2-thienyl)-N-(3-phosphoryl-n-alkyl)pyrrole on the behavior of the DNA sensor was investigated. This biosensing scheme was finally extended to the electrochemical detection of DNA at submicrometer-sized DNA biosensors integrated into bifunctional atomic force scanning electrochemical microscopy probes. The 18-mer DNA target was again monitored by following the ion-exchange properties of the polypyrrole film. Control experiments were performed with 12-base pair mismatched sequences.

Piezoelectric biosensors for real-time monitoring of hybridization and detection of hepatitis C virus.

The piezoelectric quartz crystal resonators modified with oligonucleotide probes were used for detection of hepatitis C virus (HCV) in serum. The gold electrodes on either rough or smooth surface crystals were modified with a self-assembled monolayer of cystamine. After activation with glutaraldehyde, either avidin or streptavidin were immobilized and used for attachment of biotinylated DNA probes (four different sequences). Piezoelectric biosensors were used in a flow-through setup for direct monitoring of DNA resulting from the reverse transcriptase-linked polymerase chain reaction (RT-PCR) amplification of the original viral RNA. The samples of patients with hepatitis C were analyzed and the results were compared with the standard RT-PCR procedure (Amplicor test kit of Roche, microwell format with spectrophotometric evaluation). The piezoelectric hybridization assay was completed in 10 min and the same sensing surface was suitable for repeated use.