Effect of the association between citric acid and EDTA on root surface etching

Objective: This study aims to compare the clot stabilization on root surfaces conditioned with citric acid and ethylenediaminetetraacetic acid (EDTA). Materials and methods: Scaled root samples (n = 100) were set in five groups: group I?control group (saline solution); group II (24% EDTA); group III (25% citric acid); group IV (EDTA + citric acid); group V (citric acid + EDTA). Fifty samples were assessed using the root surface modification index (RSMI). The other 50 received a blood drop after conditioning. Clot formation was assessed using blood elements adhesion index (BEAI). A blind examiner evaluated photomicrographs. Statistical analysis considered p < 0.05. Results: Groups-III and G-V attained the best results for RSMI and BEAI in comparison to control. The worst results for clot stabilization were seen in group-II. EDTA employment before citric acid (group-IV) reduced clot formation in comparison to citric acid use alone (group-III). Conclusion: Root conditioning with citric acid alone and before EDTA had the best results for smear layer removal and clot stabilization. EDTA inhibited clot stabilization on root surface and must have a residual activity once it has diminished clot adhesion to root even after citric acid conditioning. Thus, EDTA can be used to neutralize citric acid effects on periodontal cells without affecting clot stabilization. Clinical significance: To demonstrate that citric acid use on root surfaces previously affected by periodontal disease may favor clot stabilization and may have a beneficial effect on surgical outcomes. Also, EDTA can be used to neutralize citric acid effects on periodontal cells.

Effect of Er:YAG laser and diamond drill on hybrid layer morphology obtained with self-etch adhesive: analysis by SEM and confocal laser scanning microscopy (CLSM)

This study aimed to evaluate the effect of Er:YAG (L) and diamond drills (DD) on: 1) the microshear bond strength (MPa); 2) the adhesive interface of two-step (TS) – Adper Scotchbond Multipurpose and one-step (OS) adhesives – Adper EasyOne, both from 3M ESPE. Material and methods: According to the preparation condition and adhesives, the samples were divided into four groups: DD_TS (control); DD_OS; L_TS and L_OS. 60 bovine incisors were randomly divided into experimental and groups: 40 for microshear bond strength (n = 10) and 20 for the adhesive interface morphology [6 to measure the thickness of the hybrid layer (HL) and length of tags (t) by CLSM (n = 3); 12 to the adhesive interface morphology by SEM (n = 3) and 2 to illustrate the effect of the instruments on dentine by SEM (n = 1)]. To conduct the microshear bond strength test, four cylinders (0.7 mm in diameter and 1 mm in height with area of adhesion of 0.38 mm) were constructed with resin composite (Filtek Z350 XT – 3M ESPE) on each dentin surface treated by either L or DD and after adhesives application. Microshear bond strength was performed in universal testing machine (EMIC 2000) with load cell of 500 kgf and a crosshead speed of 0.5 mm / min. Adhesive interface was characterized by thickness of hybrid layer (HL) and length of tags (t) in nm, with the aid of UTHSCSA ImageTool software. Results: Microshear bond strength values were: L_TS 34.10 ± 19.07, DD_TS 24.26 ± 9.35, L_OS 33.18 ± 12.46, DD_OS 21.24 ± 13.96. Two-way ANOVA resulted in statistically significant differences only for instruments (p = 0.047). Mann-Whitney identified the instruments which determined significant differences for HL thickness and tag length (t). Concerning to the adhesive types, these differences were only observed for (t). Conclusion: It can be concluded that 1) laser Er:YAG results in higher microshear bond strength values regardless of the adhesive system (TS and OS); 2) the tags did not significant affect the microshear bond strength; 3) the adhesive interface was affected by both the instruments for cavity preparation and the type of adhesive system used.

Erosive potencial of energy drinks on the dentine surface

Coordenação de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)

The smear layer created by scaling and root planing is physiologically eliminated in a biphasic process

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Analysis of anticaries potential of pit and fissures sealants containing amorphous calcium phosphate using synchrotron microtomography

The aim of this study was to analyze the anticaries potential of pit and fissure sealants containing amorphous calcium phosphate (ACP) by synchrotron microtomography. Bovine enamel blocks (4x4 mm; n=50) were selected through surface hardness (Knoop) analysis. Slabs were obtained through cross-sections taken 1 mm from the border of the enamel. Five indentations, spaced 100 mu m apart, were made 300 mu m from the border. Ten specimens were prepared for each tested material (Ultraseal XT plus TM, Aegis, Embrace, Vitremer and Experimental Sealant). The materials were randomly attached to the sectioned surfaces of the enamel blocks and fixed with sticky wax. The specimens were submitted to pH cycling. After that, the surface hardness (SH1) was determined, and the blocks were submitted to synchrotron microcomputed tomography analysis to calculate the mineral concentration (Delta g(HAp) cm(-3)) at different areas of the enamel. The comparison between the SH1 and DgHAp cm(-3) showed a correlation for all groups (r=0.840; p<0.001). The fluoride groups presented positive values of DgHAp cm(-3), indicating a mineral gain that was observed mainly in the outer part of the enamel. The ACP showed mineral loss in the outer enamel compared with fluoride groups, although it inhibited the demineralization in the deeper areas of enamel. The combination of two remineralizing agents (fluoride and ACP) was highly effective in preventing demineralization.

Effect of composite surface treatment and aging on the bond strength between a core build-up composite and a luting agent

Objective: The purpose of this study was to assess the influence of conditioning methods and thermocycling on the bond strength between composite core and resin cement. Material and Methods: Eighty blocks (8x8x4 mm) were prepared with core build-up composite. The cementation surface was roughened with 120-grit carbide paper and the blocks were thermocycled (5,000 cycles, between 5 degrees C and 55 degrees C, with a 30 s dwell time in each bath). A layer of temporary luting agent was applied. After 24 h, the layer was removed, and the blocks were divided into five groups, according to surface treatment: (NT) No treatment (control); (SP) Grinding with 120-grit carbide paper; (AC) Etching with 37% phosphoric acid; (SC) Sandblasting with 30 mm SiO2 particles, silane application; (AO) Sandblasting with 50 mu m Al2O3 particles, silane application. Two composite blocks were cemented to each other (n=8) and sectioned into sticks. Half of the specimens from each block were immediately tested for microtensile bond strength (mu TBS), while the other half was subjected to storage for 6 months, thermocycling (12,000 cycles, between 5 degrees C and 55 degrees C, with a dwell time of 30 s in each bath) and mu TBS test in a mechanical testing machine. Bond strength data were analyzed by repeated measures two-way ANOVA and Tukey test (alpha=0.05). Results: The mu TBS was significantly affected by surface treatment (p=0.007) and thermocycling (p=0.000). Before aging, the SP group presented higher bond strength when compared to NT and AC groups, whereas all the other groups were statistically similar. After aging, all the groups were statistically similar. SP submitted to thermocycling showed lower bond strength than SP without thermocycling. Conclusion: Core composites should be roughened with a diamond bur before the luting process. Thermocycling tends to reduce the bond strength between composite and resin cement.

First insight on the impact of an osteoblastic layer on the bio-tribocorrosion performance of Ti6Al4V hip implants

In uncemented Ti6Al4V hip implants, the bone-stem interface is subjected to cyclic loading motion driven by the daily activities of the patients, which may lead to the complete failure of the implant in the long term. It may also compromise the proliferation and differentiation processes of osteoblastic cells (bone-forming cells). The main objective of this work is to approach for the first time the role of these organic materials on the bio-tribocorrosion mechanisms of cultured Ti6Al4V alloys. The colonized materials with MG63 osteoblastic-like cells were characterized through cell viability/proliferation and enzymatic activity. Tribocorrosion tests were performed under a reciprocating sliding configuration and low contact pressure. Electrochemical techniques were used to measure the corrosion kinetics of the system, under free potential conditions. All tests were performed at a controlled atmosphere. The morphology and topography of the wear scar were evaluated. The results showed that the presence of an osteoblastic cell layer on the implant surface significantly influences the tribocorrosion behavior of Ti6Al4V alloy. It was concluded that the cellular material was able to form an extra protective layer that inhibits further wear degradation of the alloy and decreases its corrosion tendency.

Erosive cola-based drinks affect the bonding to enamel surface: an in vitro study

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

Al2O3 obtained through resistive evaporation for use as insulating layer in transparent field effect transistor

Alumina thin films have been obtained by resistive evaporation of Al layer, followed by thermal oxidation achieved by annealing in appropriate atmosphere (air or O-2-rich), with variation of annealing time and temperature. Optical and structural properties of the investigated films reveal that the temperature of 550 degrees C is responsible for fair oxidation. Results of surface electrical resistivity, Raman and infrared spectroscopies are in good agreement with this finding. X-ray and Raman data also suggest the crystallization of Si nuclei at glass substrate-alumina interface, which would come from the soda-lime glass used as substrate. The main goal in this work is the deposition of alumina on top of SnO2 to build a transparent field-effect transistor. Some microscopy results of the assembled SnO2/Al2O3 heterostructure are also shown.

Innovative low temperature plasma approach for deposition of alumina films

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

Optical parameters and crystallization of flash evaporated amorphous gallium antimonide films

Flash-evaporated GaSb films are analysed using a combination of optical, surface and x-ray diffraction techniques. The effects of thermal annealings on nearly stoichiometric GaSb films are studied.

Flashover phenomenon: an analysis with influence of the thickness of the layer pollution of the high voltage polluted insulators

Results of the analysis of dynamic behavior of flashover phenomenon on the high voltage-polluted insulators are presented. These results were taken from a mathematical and an experimental model that introduce the variable thickness influence of the layer pollution deposited on the high-voltage insulator surface. Analysis of the flashover was done by way of introducing a variation in the thickness of the channel of Obenaus' model, simulating a layer pollution of variable thickness. The objective was to obtain a better reproduction of the real layer pollution deposited on the insulator that works in the polluted regions. Two types of thickness variations were used: a sudden variation, using a step; and a soft variation, using a ramp; that were put along the way of the discharge. Comparison between the mathematical and experimental models showed that introduction of a ramp makes Obenaus' model more efficient in analyzing behavior of flashover phenomenon.

Monoamine oxidase B layer-by-layer film fabrication and characterization toward dopamine detection

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

Renewable nanocomposite layer-by-layer assembled catalytic interfaces for biosensing applications

A novel, easily renewable nanocomposite interface based on layer-by-layer (LbL) assembled cationic/anionic layers of carbon nanotubes customized with biopolymers is reported. A simple approach is proposed to fabricate a nanoscale structure composed of alternating layers of oxidized multiwalled carbon nanotubes upon which is immobilized either the cationic enzyme organophosphorus hydrolase (OPH; MWNT−OPH) or the anionic DNA (MWNT−DNA). The presence of carbon nanotubes with large surface area, high aspect ratio and excellent conductivity provides reliable immobilization of enzyme at the interface and promotes better electron transfer rates. The oxidized MWNTs were characterized by thermogravimetric analysis and Raman spectroscopy. Fourier transform infrared spectroscopy showed the surface functionalization of the MWNTs and successful immobilization of OPH on the MWNTs. Scanning electron microscopy images revealed that MWNTs were shortened during sonication and that LbL of the MWNT/biopolymer conjugates resulted in a continuous surface with a layered structure. The catalytic activity of the biopolymer layers was characterized using absorption spectroscopy and electrochemical analysis. Experimental results show that this approach yields an easily fabricated catalytic multilayer with well-defined structures and properties for biosensing applications whose interface can be reactivated via a simple procedure. In addition, this approach results in a biosensor with excellent sensitivity, a reliable calibration profile, and stable electrochemical response.

Al2O3 Obtained through resistive evaporation for use as insulating layer in transparent field effect transistor

Alumina thin films have been obtained by resistive evaporation of Al layer, followed by thermal oxidation achieved by annealing in appropriate atmosphere (air or O2-rich), with variation of annealing time and temperature. Optical and structural properties of the investigated films reveal that the temperature of 550°C is responsible for fair oxidation. Results of surface electrical resistivity, Raman and infrared spectroscopies are in good agreement with this finding. X-ray and Raman data also suggest the crystallization of Si nuclei at glass substrate-alumina interface, which would come from the soda-lime glass used as substrate. The main goal in this work is the deposition of alumina on top of SnO2 to build a transparent field-effect transistor. Some microscopy results of the assembled SnO2/Al2O3 heterostructure are also shown.