Effect of different toothpastes on permeability and roughness of eroded dentin / Efeito de diferentes cremes dentais na permeabilidade e rugosidade da dentina erodida

ABSTRACT Dentin hypersensitivity (DH) is characterized by rapid, acute pain arising from exposed dental tubules. Aim: the aim of this study was to evaluate the roughness, tubule occlusion, and permeability of eroded dentin brushed with different toothpastes. Materials and Method: ninety bovine teeth were cut into blocks. Thirty hemifaces were protected with varnish and the other sixty were submitted to permeability tests. Specimens were divided into groups according to the dentifrices: without fluoride (WF), sodium fluoride (NaF), and stannous fluoride (SnF2). The blocks were subjected to a 5-day erosive-abrasive protocol. Surface roughness and dentinal tubule occlusion (n=10) were assessed for both control and test hemifaces of the same sample along with permeability analysis (n=20). Two-way RM ANOVA and Tukey's post-hoc test were performed (p≤0.05). Results: NaF and SnF2 presented higher roughness than WF. The number of open tubules was higher in WF. Permeability was higher in SnF2, but there was no significant difference between WF and NaF. Conclusions: both fluoride toothpastes occluded dentinal tubules and increased roughness. NaF toothpaste promoted greater decrease in dentin permeability.

RESUMO A hipersensibilidade dentinária (HD) é caracterizada por dor rápida e aguda decorrente de túbulos dentais expostos. Objetivo: este estudo teve como objetivo avaliar a rugosidade, oclusão tubular e permeabilidade da dentina erodida escovada com diferentes dentifrícios. Materiais e Método: noventa dentes bovinos foram seccionados em blocos. Trinta hemifaces foram protegidas com verniz e outras sessenta foram submetidas à permeabilidade. Os espécimes foram divididos em grupos de acordo com os dentifrícios: sem flúor (SF), fluoreto de sódio (NaF) e fluoreto estanoso (SnF2). Em seguida, os blocos foram submetidos a um protocolo erosivo-abrasivo de 5 dias. A rugosidade da superfície e a oclusão do túbulo dentinário (n = 10) foram avaliadas para ambas as hemifaces de controle e teste da mesma amostra, também realizou-se a análise de permeabilidade (n = 20). Two-way RM ANOVA e pós-teste de Tukey foram realizados (p≤0,05). Resultados: NaF e SnF2 apresentaram rugosidade superior ao SF. O número de túbulos abertos foi maior em SF. Não encontramos diferenças significativas entre SF e NaF em relação à permeabilidade; entretanto, SnF2 apresentou maior permeabilidade. Conclusão: ambos os dentifrícios fluoretados foram capazes de ocluir os túbulos dentinários e aumentar a rugosidade. No entanto, o dentifrício NaF promoveu uma maior diminuição da permeabilidade dentinária.

Optimal income crossover for a two-class model using particle swarm optimization.

Personal income distribution may exhibit a two-class structure, such that the lower income class of the population (85-98%) is described by exponential Boltzmann-Gibbs distribution, whereas the upper income class (2-15%) has a Pareto power-law distribution. We propose a method, based on a theoretical and numerical optimization scheme, which allows us to determine the crossover income between the distributions, the temperature of the Boltzmann-Gibbs distribution, and the Pareto index. Using this method, the Brazilian income distribution data provided by the National Household Sample Survey was studied. The data was stratified into two dichotomies (sex/gender and color/race), so the model was tested using different subsets along with accessing the economic differences between these groups. Last, we analyze the temporal evolution of the parameters of our model and the Gini coefficient discussing the implication on the Brazilian income inequality. In this paper, we propose an optimization method to find a continuous two-class income distribution, which is able to delimit the boundaries of the two distributions. It also gives a measure of inequality which is a function that depends only on the Pareto index and the percentage of people in the high-income region. We found a temporal dynamics relation, that may be general, between the Pareto and the percentage of people described by the Pareto tail.

Effect of different toothpastes on permeability and roughness of eroded dentin.

Dentin hypersensitivity (DH) is characterized by rapid, acute pain arising from exposed dental tubules. AIM: the aim of this study was to evaluate the roughness, tubule occlusion, and permeability of eroded dentin brushed with different toothpastes. MATERIALS AND METHOD: ninety bovine teeth were cut into blocks. Thirty hemifaces were protected with varnish and the other sixty were submitted to permeability tests. Specimens were divided into groups according to the dentifrices: without fluoride (WF), sodium fluoride (NaF), and stannous fluoride (SnF2). The blocks were subjected to a 5-day erosive-abrasive protocol. Surface roughness and dentinal tubule occlusion (n=10) were assessed for both control and test hemifaces of the same sample along with permeability analysis (n=20). Two-way RM ANOVA and Tukey's post-hoc test were performed (p≤0.05). RESULTS: NaF and SnF2 presented higher roughness than WF. The number of open tubules was higher in WF. Permeability was higher in SnF2, but there was no significant difference between WF and NaF. CONCLUSIONS: both fluoride toothpastes occluded dentinal tubules and increased roughness. NaF toothpaste promoted greater decrease in dentin permeability.

A hipersensibilidade dentinária (HD) é caracterizada por dor rápida e aguda decorrente de túbulos dentais expostos. Objetivo: este estudo teve como objetivo avaliar a rugosidade, oclusão tubular e permeabilidade da dentina erodida escovada com diferentes dentifrícios. Materiais e Método: noventa dentes bovinos foram seccionados em blocos. Trinta hemifaces foram protegidas com verniz e outras sessenta foram submetidas à permeabilidade. Os espécimes foram divididos em grupos de acordo com os dentifrícios: sem flúor (SF), fluoreto de sódio (NaF) e fluoreto estanoso (SnF2). Em seguida, os blocos foram submetidos a um protocolo erosivo-abrasivo de 5 dias. A rugosidade da superfície e a oclusão do túbulo dentinário (n = 10) foram avaliadas para ambas as hemifaces de controle e teste da mesma amostra, também realizou-se a análise de permeabilidade (n = 20). Two-way RM ANOVA e pós-teste de Tukey foram realizados (p≤0,05). Resultados: NaF e SnF2 apresentaram rugosidade superior ao SF. O número de túbulos abertos foi maior em SF. Não encontramos diferenças significativas entre SF e NaF em relação à permeabilidade; entretanto, SnF2 apresentou maior permeabilidade. Conclusão: ambos os dentifrícios fluoretados foram capazes de ocluir os túbulos dentinários e aumentar a rugosidade. No entanto, o dentifrício NaF promoveu uma maior diminuição da permeabilidade dentinária.

Forecasting COVID-19 Severity by Intelligent Optical Fingerprinting of Blood Samples.

Forecasting COVID-19 disease severity is key to supporting clinical decision making and assisting resource allocation, particularly in intensive care units (ICUs). Here, we investigated the utility of time- and frequency-related features of the backscattered signal of serum patient samples to predict COVID-19 disease severity immediately after diagnosis. ICU admission was the primary outcome used to define disease severity. We developed a stacking ensemble machine learning model including the backscattered signal features (optical fingerprint), patient comorbidities, and age (AUROC = 0.80), which significantly outperformed the predictive value of clinical and laboratory variables available at hospital admission (AUROC = 0.71). The information derived from patient optical fingerprints was not strongly correlated with any clinical/laboratory variable, suggesting that optical fingerprinting brings unique information for COVID-19 severity risk assessment. Optical fingerprinting is a label-free, real-time, and low-cost technology that can be easily integrated as a front-line tool to facilitate the triage and clinical management of COVID-19 patients.

Selection and validation of reference genes by RT-qPCR under photoperiodic induction of flowering in sugarcane (Saccharum spp.).

Although reference genes have previously been used in the expression analysis of genes involved in sugarcane flowering they had not been experimentally validated for stability and consistency of expression between different samples over a wide range of experimental conditions. Here we report the analysis of candidate reference genes in different tissue types, at different temporal time-points, in both short and long day photoperiodic treatments. The stability of the candidate reference genes in all conditions was evaluated with NormFinder, BestKeeper, and RefFinder algorithms that complement each other for a more robust analysis. As the Normfinder algorithm was more appropriate for our experimental conditions, greater emphasis was placed on Normfinder when choosing the most stable genes. UBQ1 and TUB were shown to be the most stable reference genes to use for normalizing RT-qPCR gene expression data during floral induction, whilst 25SrRNA1 and GAPDH were the least stable. Their use as a reference gene pair was validated by analyzing the expression of two differentially expressed target genes (PIL5 and LHP1). The UBQ1/TUB reference genes combination was able to reveal small significant differences in gene expression of the two target genes that were not detectable when using the least stable reference gene combination. These results can be used to inform the choice of reference genes to use in the study of the sugarcane floral induction pathway. Our work also demonstrates that both PIL5 and LHP1 are significantly up-regulated in the initial stages of photoperiodic induction of flowering in sugarcane.

Influence of Light-curing Units on Surface Microhardness and Color Change of Composite Resins after Challenge.

AIM: The aim of this study was to evaluate microhardness and color change (ΔE) of composite resins, light cured with different light emission diodes (LEDs) and submitted to artificial accelerated aging (AAA). MATERIALS AND METHODS: Two composite resins with lucirin- TPO photoinitiator were selected: Tetric N-Ceram (Ivoclar Vivadent, A1) and Vit-l-escence (Ultradent, WO).A resin with the only camphorquinone photoinitiat or was chosen as a negative control: Filtek Z350XT (3M ESPE, WD). Disc-shaped specimens were prepared (5 mm diameter; 1.5 mm thick) and photopolymerized with an LED with one wavelength (Radii-Cal, SDI) or multiple wavelengths (Valo, Ultradent), for each composite resin (n = 10). Surface microhardness and color evaluations were performed immediately after specimen preparation and after AAA. Microhardness results were analyzed using Kruskal-Wallis and Mann-Whitney tests for multiple comparisons. To compare the evaluation of microhardness at different times, the Wilcoxon test was used. Mean values of ΔE, ΔL, Δa, and Δb were evaluated using two-way analysis of variance (ANOVA), and Tukey test for multiple comparisons (a = 0.05). RESULTS: Regarding microhardness, a statistically significant difference between the two LEDs was observed for Vit-lescence after AAA. When comparing composite resins that were light-cured with the same device, FiltekZ350XT obtained the greatest microhardness. All groups presented a statistically significant decrease in microhardness from the initial time to the AAA. Regarding ΔE, no statistically significant difference between the two LEDs was observed. When comparing composite resins, FiltekZ350XT showed the highest ΔE values. CONCLUSION: In general, an LED with multiple wavelengths influenced the microhardness of only one resin containing lucirin-TPO after AAA. The ΔE was more influenced by the composite resin than the LED device. CLINICAL SIGNIFICANCE: The knowledge of composite resin with deficiencies in the polymerization mechanism could contribute to preventing restorations to become more susceptible to color change and reduction of the mechanical strength.

Multiple Wire-Mesh Sensors Applied to the Characterization of Two-Phase Flow inside a Cyclonic Flow Distribution System.

Wire-mesh sensors are used to determine the phase fraction of gas⁻liquid two-phase flow in many industrial applications. In this paper, we report the use of the sensor to study the flow behavior inside an offshore oil and gas industry device for subsea phase separation. The study focused on the behavior of gas⁻liquid slug flow inside a flow distribution device with four outlets, which is part of the subsea phase separator system. The void fraction profile and the flow symmetry across the outlets were investigated using tomographic wire-mesh sensors and a camera. Results showed an ascendant liquid film in the cyclonic chamber with the gas phase at the center of the pipe generating a symmetrical flow. Dispersed bubbles coalesced into a gas vortex due to the centrifugal force inside the cyclonic chamber. The behavior favored the separation of smaller bubbles from the liquid bulk, which was an important parameter for gas-liquid separator sizing. The void fraction analysis of the outlets showed an even flow distribution with less than 10% difference, which was a satisfactorily result that may contribute to a reduction on the subsea gas⁻liquid separators size. From the outcomes of this study, detailed information regarding this type of flow distribution system was extracted. Thereby, wire-mesh sensors were successfully applied to investigate a new type of equipment for the offshore oil and gas industry.

Comparison of different polishing methods on the surface roughness of microhybrid, microfill, and nanofill composite resins.

AIM: The aim of the present study was to evaluate the effect of different polishing methods on the surface roughness of resin-based composites subjected to a thermocycling procedure. METHODS: A total of 192 specimens were divided into 24 groups, according to composite materials (Filtek Z250, Point 4, Renamel Nanofill, Filtek Supreme Plus, Renamel Microfill, and Premise) and finishing and polishing systems (Sof-Lex Pop On, Super Snap, Flexidisc, and Flexidisc+Enamelize). The specimens were subjected to thermocycling (5000 cycles). RESULTS: Filtek Supreme Plus showed the lowest surface roughness values before thermocycling. After thermocycling, Filtek Supreme Plus continued to have the lowest surface roughness, with a statistically-significant difference for the other materials. After thermocycling, there was no statistically-significant difference among all the polishing techniques studied. CONCLUSIONS: The thermocycling was concluded as being able to change composite resins' surface roughness, whereas different finishing and polishing methods did not result in surface roughness changes after thermocycling.

Influence of Mechanical and Chemical Degradation in the Surface Roughness, Gloss, and Color of Microhybrid Composites.

AIM: The aim of this study was to investigate the association of different degradations on the roughness, gloss, and color changes of microhybrid composites. MATERIALS AND METHODS: Ten specimens were prepared for Charisma, Amelogen Plus, Point 4, and Opallis resins. Surfaces were polished and baseline measurements of roughness, gloss, and color were recorded. Specimens were then submitted to chemical and mechanical challenges, and the specimens were reevaluated. Roughness and gloss were analyzed by Kruskal -Wallis and Dunn's test (p < 0.05). Color change (ΔE) was analyzed by one-way analysis of variance and Tukey's tests (p < 0.05). The initial and final data were compared using the Wilcoxon test (p < 0.05). Spearman test checked the correlation between the roughness and gloss (p < 0.05). RESULTS: Regarding surface roughness and gloss, there was no difference between composites before challenges. However, all composites showed a significant increase of roughness after challenges, with highest values for Charisma. The gloss was influenced by challenges, evidencing the best gloss for Point 4. Charisma showed the highest value of color change. There was no correlation between surface roughness and gloss for the initial analysis, and after the challenges. CONCLUSION: Composites were influenced by association of challenges, and Charisma showed the highest changes for roughness, gloss, and color. CLINICAL SIGNIFICANCE: The type of composite resin influenced the properties of materials, which are surface roughness, gloss, and color change. The dentist should be aware of the performance of different brands, to choose the correct required composite resin for each type of patient or region to be restored.

Effect of Shear History on Rheology of Time-Dependent Colloidal Silica Gels.

This paper presents a rheological study describing the effects of shear on the flow curves of colloidal gels prepared with different concentrations of fumed silica (4%, 5%, 6%, and 7%) and a hydrophobic solvent (Hydrocarbon fuel, JP-8). Viscosity measurements as a function of time were carried out at different shear rates (10, 50, 100, 500, and 1000 s-1), and based on this data, a new structural kinetics model was used to describe the system. Previous work has based the analysis of time dependent fluids on the viscosity of the intact material, i.e., before it is sheared, which is a condition very difficult to achieve when weak gels are tested. The simple action of loading the gel in the rheometer affects its structure and rheology, and the reproducibility of the measurements is thus seriously compromised. Changes in viscosity and viscoelastic properties of the sheared material are indicative of microstructural changes in the gel that need to be accounted for. Therefore, a more realistic method is presented in this work. In addition, microscopical images (Cryo-SEM) were obtained to show how the structure of the gel is affected upon application of shear.

Repairability of aged resin composites mediated by different restorative systems.

The aim of this study was to evaluate the shear bond strength of resin composite repairs with and without aging of the surface to be repaired, using different adhesive systems and resin composites. Ninety specimens were prepared: 10 for the Control Group (GC - without repair); 40 for Group I (GI - repairs after 7 days) and 40 for Group II (GII - repairs after 180 days). Groups I and II were divided into 4 subgroups of 10 specimens each, according to the adhesive system and composite resin used: A) Adper Scotch Bond Multipurpose + Filtek Z350 XT; B) Adper Single Bond Plus + Filtek Z350 XT; C) Adper Scotch Bond Multipurpose + Esthet-X; D) Adper Single Bond Plus + Esthet-X. The specimens were tested for shear strength in a universal testing machine. The results were analyzed by two-factor one-way ANOVA and Fisher's post hoc tests (alpha=0.05). The control group had better performance than the other groups. There was no significant difference when comparing different adhesive systems and composite resins. Repairs performed at 7 days were better than those performed at 180 days. The composite repairs decreased the mechanical strength of the restoration. Aging of the resin substrate may decrease repair bond strength over time, regardless of the type of adhesive systems and resin composites used.

Avaliar a resistência de união ao cisalhamento de reparos de resina composta com e sem envelhecimento da superfície a ser reparada, utilizando diferentes sistemas adesivos. Noventa corpos de prova foram confeccionados sendo: 10 para o Grupo Controle (GC - sem reparo); 40 para o Grupo I (GI - reparos após 7 dias) e 40 para o Grupo II (GII ­ reparos após 180 dias). Para os reparos, os grupos GI e GII foram subdivididos em 4 subgrupos com 10 corpos de prova, variando o sistema adesivo e a resina composta: A) Adper Scotch Bond Multipurpose+ Filtek Z350XT; B)Adper Single Bond Plus+ Filtek Z350XT; C)Adper Scotch Bond Multipurpose+ Esthet-X; D) Adper Single Bond Plus+ Esthet-X. Os corpos de prova foram submetidos a uma força de cisalhamento em uma máquina de ensaio universal (EMIC). Os resultados foram analisados pelo teste estatístico Anova dois fatores, seguido pelo teste de Fisher´s. Observou-se melhor comportamento do grupo controle sobre os demais grupos, além disso, os reparos realizados aos 7 dias foram superiores aos dos realizados em 180 dias. Não houve diferença significativaquando se comparou diferentes sistemas adesivos e resinas compostas. Os reparos de resina composta diminuem a resistência mecânica da restauração.O envelheci mento do substrato de resina pode diminuir a resistência ao reparo ao longo do tempo, independentemente do tipo de sistemas adesivos e resinas compostas utilizados.

Repairabilitiy of aged resin composites mediated by different restorative systems / Reparo de resinas compostas envelhecidas e mediadas por diferentes materiais restauradores

The aim of this study was to evaluate the shear bond strengthof resin composite repairs with and without aging of thesurface to be repaired, using different adhesive systems andresin composites. Ninety specimens were prepared: 10 for theControl Group (GC - without repair); 40 for Group I (GI -repairs after 7 days) and 40 for Group II (GII - repairs after180 days). Groups I and II were divided into 4 subgroups of10 specimens each, according to the adhesive system andcomposite resin used: A) Adper Scotch Bond Multipurpose +Filtek Z350 XT; B) Adper Single Bond Plus + Filtek Z350 XT;C) Adper Scotch Bond Multipurpose + Esthet-X; D) AdperSingle Bond Plus + Esthet-X. The specimens were tested forshear strength in a universal testing machine. The resultswere analyzed by two-factor one-way ANOVA and Fisher’spost hoc tests (alpha=0.05). The control group had betterperformance than the other groups. There was no significantdifference when comparing different adhesive systems andcomposite resins. Repairs performed at 7 days were betterthan those performed at 180 days. The composite repairsdecreased the mechanical strength of the restoration. Agingof the resin substrate may decrease repair bond strength overtime, regardless of the type of adhesive systems and resin composites used.

Avaliar a resistência de união ao cisalhamento de reparos deresina composta com e sem envelhecimento da superfície a serreparada, utilizando diferentes sistemas adesivos. Noventacorpos de prova foram confeccionados sendo: 10 para o GrupoControle (GC - sem reparo); 40 para o Grupo I (GI - reparosapós 7 dias) e 40 para o Grupo II (GII – reparos após 180 dias).Para os reparos, os grupos GI e GII foram subdivididos em 4subgrupos com 10 corpos de prova, variando o sistema adesivoe a resina composta: A) Adper Scotch Bond Multipurpose+Filtek Z350XT; B)Adper Single Bond Plus+ Filtek Z350XT;C)Adper Scotch Bond Multipurpose+ Esthet-X; D) AdperSingle Bond Plus+ Esthet-X. Os corpos de prova foramsubmetidos a uma força de cisalhamento em uma máquina deensaio universal (EMIC). Os resultados foram analisados peloteste estatístico Anova dois fatores, seguido pelo teste deFisher ́s. Observou-se melhor comportamento do grupocontrole sobre os demais grupos, além disso, os reparosrealizados aos 7 dias foram superiores aos dos realizados em180 dias. Não houve diferença significativaquando secomparou diferentes sistemas adesivos e resinas compostas.Os reparos de resina composta diminuem a resistênciamecânica da restauração.O envelheci mento do substrato deresina pode diminuir a resistência ao reparo ao longo dotempo, independentemente do tipo de sistemas adesivos eresinas compostas utilizados.

Mechanically modified xanthan gum: Rheology and polydispersity aspects.

Xanthan gum solutions were treated with high-pressure homogenization (HPH) in order to provide alternative treatments to enzymatic and chemical modification of this carbohydrate. Rheological properties of the treated and control samples were investigated in detail to gain an understanding of functional consequences of physical modification. The molecular structural properties were investigated via Size exclusion chromatography (SEC) coupled with Multi-angle laser light scattering (MALLS) and Circular dichroism (CD). Structured network of xanthan gum solutions was lost gradually depending on the severity of the HPH treatment as evidenced by the observed changes in the viscosity and viscoelasticity of the treated solutions. Reduction in molecular weight and a significant increase in polydispersity of the polymer were the expected causes of these rheological changes. Observed increase in hydrodynamic volume upon HPH treatment was not surprising and attributed to the loss of structured networks. Changes in the rheological and structural characteristics of biopolymer were irreversible and significant recovery was not detected over a period of 11 weeks.

Streptococcus mutans-derived extracellular matrix in cariogenic oral biofilms.

Biofilms are highly structured microbial communities that are enmeshed in a self-produced extracellular matrix. Within the complex oral microbiome, Streptococcus mutans is a major producer of extracellular polymeric substances including exopolysaccharides (EPS), eDNA, and lipoteichoic acid (LTA). EPS produced by S. mutans-derived exoenzymes promote local accumulation of microbes on the teeth, while forming a spatially heterogeneous and diffusion-limiting matrix that protects embedded bacteria. The EPS-rich matrix provides mechanical stability/cohesiveness and facilitates the creation of highly acidic microenvironments, which are critical for the pathogenesis of dental caries. In parallel, S. mutans also releases eDNA and LTA, which can contribute with matrix development. eDNA enhances EPS (glucan) synthesis locally, increasing the adhesion of S. mutans to saliva-coated apatitic surfaces and the assembly of highly cohesive biofilms. eDNA and other extracellular substances, acting in concert with EPS, may impact the functional properties of the matrix and the virulence of cariogenic biofilms. Enhanced understanding about the assembly principles of the matrix may lead to efficacious approaches to control biofilm-related diseases.

Quantitative Sensory Testing of the Effect of Desensitizing Treatment After Dental Bleaching.

The aim of this study was to quantify tooth sensitivity during bleaching and after a desensitizing treatment. Sensitivity was measured with a new device, TSA-II, which uses thermal stimuli for Quantitative Sensory Testing (QST). Ten patients underwent bleaching treatment using Whiteness HP Maxx (FGM Produtos Odontológicos Ltda) containing 35% hydrogen peroxide. After the bleaching session, the teeth were cleaned with air/water spray and the product Desensibilize KF 2% (FGM Produtos Odontológicos Ltda) was applied to the upper left teeth. Saline solution at room temperature was applied in the upper right teeth. QST was performed before bleaching, immediately after bleaching, and immediately after desensitizing treatment. In order to standardize tooth analysis, a 100% ethylene copolymer and vinyl acetate tray with circular perforations was used during measurements. Analysis of variance and the Student's t-test were used (a=0.05). Mean temperatures (SD) of cold sensation threshold for the upper right quadrant were: BB-13.898 (4.81), AB- 19.241 (3.68), AD-20.646 (3.72) and for the upper left quadrant they were: BB-14.102 (3.22), AB-19.646 (4.82), AD- 13.835 (3.63). Dental bleaching with highly concentrated peroxides changed dental cold sensation thresholds, but the topical desensitizer changed the immediate cold sensation thresholds produced by the cold stimulus.

O objetivo do presente estudo foi quantificar a sensibilidade dentária durante o tratamento clareador e após a aplicação de um dessensibilizante utilizando um equipamento de análise neurosensorial, o TSA II, que utiliza estímulos térmicos para a realização do Teste Sensorial Quantitativo (QST). Assim, dez pacientes (n=10) receberam o tratamento clareador com Whiteness HP Maxx (FGM Produtos Odontológicos Ltda.) contendo peróxido de hidrogênio a 35%. Após a sessão clareadora, os dentes foram limpos com jatos de ar/água e foi realizada a aplicação do Desensibilize KF 2% (FGM Produtos Odontológicos Ltda.), um dessensibilizante tópico a base de nitrato de potássio a 5% e fluoreto de sódio a 2%, apenas no hemi-arco esquerdo da maxila, utilizando o método da boca dividida. No hemi-arco direito foi aplicada uma solução salina a temperatura ambiente (controle). O QST foi realizado antes do clareamento (AC), imediatamente depois do clareamento (DC) e imediatamente após a aplicação do dessensibilizante (DD). Para padronizar o local do estímulo, uma moldeira de acetato com perfurações circulares foi utilizada durante as mensurações. A análise estatística foi realizada por meio do teste t de Student (α=0,05). As temperaturas médias (DP) do limiar de sensação ao frio para o hemi-arco direito foram: AC- 13,898 (4,81), DC-19,241 (3,68), DD-20,646 (3,72) e para o hemi-arco esquerdo foram: AC-14,102 (3,22), DC-19,646 (4,82), DD-13,835 (3,63). Clareamento dental com peróxidos de alta concentração exacerbaram a sensibilidade dental ao estímulo térmico e o uso do dessensibilizante foi efetivo para reverter esta situação.

Microtensile bond strength of resin cements to caries-affected dentin.

STATEMENT OF PROBLEM: The bonding of resin materials to caries-affected dentin, especially self-adhesive cements, remains a challenge in dentistry. PURPOSE: The purpose of this study was to evaluate the bond strength of different resin cements to sound or caries-affected dentin at 24 hours and 6 months after the bonding procedure. MATERIAL AND METHODS: Thirty-six human molars were used, 18 sound and 18 affected by caries. Indirect composite resin blocks (Tescera) were bonded to dentin by using 3 different resin cements: RelyX ARC, Panavia F, and RelyX Unicem. A universal testing machine was used to measure the microtensile bond strength 24 hours and 6 months after the bonding procedure. Representative specimens were analyzed with a scanning electron microscopy. The results were submitted to 3-way analysis of variance and the Fisher test (α=.05). RESULTS: The highest values of microtensile bond strength were found with RelyX ARC for both tooth conditions (P<.001). There was no difference between RelyX Unicem and Panavia F (P>.05). There was no difference between caries-affected and sound dentin (P=.89). CONCLUSIONS: Caries did not influence the bonding strength of resin cements to dentin.

Correlation between hybrid layer thickness, resin tag length and microtensile bond strength of a self-etching adhesive system.

The purpose of this study was to evaluate the correlation between the hybrid layer thickness, resin tag length and resin bond strength of a self-etching adhesive system to sound dentin tissue "in vivo". After performing restorative procedures and tooth extractions, ten specimens were sectioned in a mesiodistal direction. One dental section was used for light microscope analysis, in which both the resin tag length and hybrid layer thickness were measured, while the other section was analyzed using a microtensile test (0.5 mm/min). The fractured surface of the latter section was characterized using a stereoscopic magnifying glass (40x magnifcation). The results were subject to statistical analysis using the Pearson Correlation Test (a = 0.05). The hybrid layer thickness, resin tag length and resin bond strength mean values were 2.19 microm (0.34), 4.34 microm (0.28) and 9.73 MPa (5,55), respectively. In addition, correlation tests between the resin tag length and the resin bond strength (r=0.014) and also between the hybrid layer thickness and bond strength (r=0.43), showed no statistically significant correlation. The microtensile bond strength of Adper Prompt L Pop self-etching adhesive system does not depend on hybrid layer thickness or resin tag length.

Occurrence of sensitivity during at-home and in-office tooth bleaching therapies with or without use of light sources.

The aim of this study was to evaluate the effect of tooth bleaching with 10% carbamide peroxide (CP) or 35% hydrogen peroxide (HP), with or without quartz-tungsten-halogen light or hybrid source LED/infrared laser exposition on the occurrence duration, intensity and location of tooth sensitivity Forty patients were selected and randomly divided into four groups: GI--home bleaching with CP for 4 hours a day, over the course of 3 weeks; GII--three sessions of HP with three 10-minute applications at each session and no light source; GIII--the same procedure as GII with quartz-tungsten-halogen light irradiation; GIV--the same procedure as GII with LED/laser light irradiation. The evaluation included an appointment with each patient before and after each HP bleaching session or each weekly CP bleaching and 7, 30 and 180 days after the end of treatment. The Kruskal-Wallis test revealed that the duration and intensity of post-treatment sensitivity were significantly higher for HP than for CP (p< 0.05), and symptoms were located predominantly in anterior teeth. All bleaching methods generated sensitivity, which was more frequent in anterior teeth. However, treatment with CP generated lower sensitivity than treatment with HP independently of the light sources.