Manufacture of magnesium-fortified Chihuahua cheese.

The aim of this study was to manufacture magnesium-fortified Chihuahua cheese and to evaluate the effect of magnesium fortification on quality parameters. Addition of magnesium chloride to milk during pasteurization (5.44, 10.80, 16.40, 22.00, and 25.20 g of MgCl2·6H2O/L of milk) resulted in cheese with increased magnesium content, proportional to the amount of magnesium added (up to 2,957.13 mg of Mg/kg of cheese). As magnesium content increased, coagulation time and moisture content also increased, whereas calcium content decreased. Higher levels of magnesium fortification (16.40 g of MgCl2·6H2O/L of milk or more) induced the development of bitter-acid flavors and softer texture. Addition of 10.80 g of MgCl2·6H2O/L to milk resulted in Chihuahua cheese that meets regulatory standards and possesses physicochemical and sensory characteristics similar to those of nonfortified Chihuahua cheese. Under this milk fortification level, the manufactured cheese is able to provide 148.4 mg of magnesium per day (35% of the recommended daily intake of magnesium for adult males and 46% for adult females) assuming 3 portions (28 g each) are consumed.

Chemical interactions among caseins during rennet coagulation of milk.

Rennet milk curds were prepared under 4 different temperature and acidity conditions. The development of different types of inter-protein chemical bonds (disulfide, hydrophobic, electrostatic, hydrogen, and calcium bridges) was monitored for 60 min after curd cutting. Hydrophobic inter-protein interactions originally present in casein micelles in milk were substituted by electrostatic, hydrogen, and calcium bonds throughout the curd curing period. Disulfide bonds were not disturbed by the experimental conditions employed in the study, remaining at a constant level in all studied treatments. Acidification of curds increased the availability of soluble ionic calcium, increasing the relative proportion of calcium bridges at the expense of electrostatic-hydrogen bonds. Although pH defined the nature of the interactions established among proteins in curd, temperature modified the rate at which such bonds were formed.

Efectos de la pandemia en los programas de formación en cirugía: problemas y soluciones / Effects of pandemic on training programs in surgery: problems and solutions

Resumen La pandemia por el virus SARS-CoV-2 ha afectado fuertemente los programas de educación quirúrgica. El Capítulo Chileno del American College of Surgeons realizó un webinar para evaluar y discutir los efectos de la pandemia en la educación quirúrgica. Este evento contó con la asistencia de 450 personas de 17 países, incluyendo la participación de destacados docentes del área quirúrgica. Las principales conclusiones de este webinar fueron que la pandemia alteró considerablemente los programas de educación quirúrgica. Un 26% de los residentes se contagiaron, pero la mayoría no precisó cuidados especiales. Las intervenciones quirúrgicas disminuyeron hasta en un 90% en algunos programas. Los residentes debieron asumir el cuidado de pacientes COVID-19. Se han implementado sistemas de enseñanza virtual, como seminarios en línea o webinars, discusión de casos clínicos, videos y simulación. Dichas actividades teóricas, al igual que la simulación quirúrgica fueron evaluadas, mayoritariamente, vía web. Las sociedades científicas han tenido un importante rol en estas actividades. En el futuro, los programas universitarios enfrentarán escenarios con menos pacientes y una reducción de las oportunidades de enseñanza para residentes. Las actividades en línea y simulación adquirirán mayor relevancia. Es posible superar esta crisis como lo han hecho los países desarrollados, comparados con ellos, carecemos de un plan nacional de emergencia en salud, en el que los estudiantes y personal sanitario tengan un rol definido en áreas específicas, con metas concretas. El retorno a la "nueva normalidad" estará lleno de desafíos.

The SARS-CoV-2 pandemic has had an impact in surgical residency programs. The Chilean chapter of the American College of Surgeons organized a webinar to discuss and address the effects of this pandemic on surgical education. This meeting had a virtual attendance of 450 people from 17 countries, including the participation of surgical educators. Conclusions of this webinar were that COVID-19 has strongly affected surgical education programs. Twenty six per cent of residents were infected. Most of them did not need special care. Surgical opportunities have decreased up to 90% in some programs. Residents have had to be involved in managing COVID-19 patients. Changes in surgical education, led to a virtual instruction which includes seminars, webinars, case discussion, videos and simulation. Assessment has been performed of theoretical activities, via web. Simulation tasks also have been evaluated. Scientific societies had a very important role in these activities. In the near future, university programs will face different scenarios in hospitals and clinical centers, with fewer patients and reduced clinical instruction for residents. Online activities and simulation will increase in relevance in years to come. It is possible to overcome this crisis, as some developed countries have already done, compared to them, we lack a national emergency health plan in which medical students, residents, doctors, and all health care providers have a designated role in specific areas with clear goals. The return to "the new normal" will be filled with challenges.

Structure rearrangement during rennet coagulation of milk modifies curd density.

Milk curds are a semisolid structure resulting from the enzymatic coagulation of milk, consisting mainly of paracasein micelles, fat globules, and whey. This gel undergoes a series of changes in its composition and structure during setting and curing, affecting curd density. The present study investigated the composition and density of inoculated and noninoculated milk curds during a 60-min curing period conducted at 30, 35, and 40°C. The purpose of the study was to determine the density changes occurring in the protein phase of curds during curing under different conditions of temperature and pH to understand the nature of the structural changes happening in the paracasein matrix. Noninoculated curd density values oscillated between 1.0247 and 1.0294 g/cm3 after 60 min of curing, whereas inoculated treatments showed values between 1.0222 and 1.0321 g/cm3. This small difference in density between the studied samples was surprising because the whey content of samples differed greatly. Density of the protein phase reached values of 1.8002 and 1.4388 g/cm3 for noninoculated and inoculated curds, respectively, after 60 min of curing. Two independent mechanisms involved in the development of the protein-based structure of curds were identified upon comparison of the development of protein phase density in inoculated and noninoculated curds. Although the larger increase in protein phase density observed in noninoculated curds was probably due to the concurrent action of calcium-mediated electrostatic bonds and temperature-dependent hydrophobic bonds, inoculated curds showed a lower protein phase density caused by calcium solubilization and by a decrease in the net charge of paracasein micelles induced by pH reduction.

Anti TNF como inductor de lupus cutáneo: caso clínico / Anti TNF as inducer of cutaneous lupus: clinical case

El mayor acceso a las terapias biológicas para el tratamiento de múltiples enfer-medades autoinmune trae consigo el mayor riesgo de padecer eventos adversos relacionados al uso de estos2,4. Presentamos un caso clínico de una paciente con diagnóstico de artritis reumatoide en tratamiento con ANTI TNF

The greater access to biological therapies for the treatment of multiple autoim-mune diseases brings with it the greatest risk of suffering adverse events related to the use of these (2,4). We present a clinical case of a patient diagnosed with rheumatoid arthritis in treatment with ANTI TNF

Hepatectomía en 2 tiempos con técnica de ALPPS (Asociación de bipartición hepática con ligadura portal para hepatectomía en 2 tiempos): experiencia y resultados iniciales del Hospital Regional de Talca / 2 stage hepatectomy with ALPPS technique (Liver splitting association) with ligature portal for hepatectomy in 2 times): experience and initial results of the Regional Hospital of Talca

Resumen Introducción: La insuficiencia hepática posoperatoria (IHP) es una causa importante de morbimortalidad posoperatoria en cirugía hepática. Un remanente hepático futuro (RHF) insuficiente es una de las principales causas IHP La asociación de bipartición hepática con ligadura portal para hepatectomía en 2 tiempos (ALPPS) es una técnica relativamente nueva que induce una rápida hipertrofia parenquimatosa reduciendo el tiempo de espera para lograr un volumen hepático adecuado. Nuestro objetivo es comunicar la experiencia y los resultados iniciales de la hepatectomía en 2 tiempos utilizando la técnica de ALLPS. Material y Método: Se incluyeron todos los pacientes en los que se ha realizado una hepatectomía en 2 tiempos utilizando la técnica de ALPPS entre el 1 de junio de 2014 y el 31 de julio de 2016 en la Unidad de Cirugía Digestiva del Hospital Regional de Talca. Resutados: Durante el periodo de estudio, se realizaron 47 hepatectomías en el Hospital Regional de Talca. En 3 casos (6.3%), se realizó una hepatectomía en 2 tiempos utilizando la técnica de ALPPS, en todos ellos se logró una hipertrofia del remanente hepático futuro (RHF) que permitió completar el segundo tiempo sin IHP clínicamente significativa. Conclusión: En nuestra experiencia inicial, la técnica de ALPPS logró aumentar el RHF permitiendo resecar pacientes que inicialmente tenían un RHF insuficiente para ser sometidos a una hepatectomía mayor.

Introduction: Postoperative liver failure (POLF) is a relevant cause of morbimortality after liver surgery. An insufficient future liver remnant (FLR) is one of the main causes of POLF. The association of hepatic bipartition with portal ligation for 2-stage hepatectomy (ALPPS) is a relatively new technique that induces rapid parenchymal hypertrophy reducing the waiting time to achieve adequate FLR. Our aim is to communicate the experience and the initial results of the hepatectomy in 2-stages using the ALLPS technique. Material and Method: All patients in whom a 2-stage hepatectomy using ALPPS technique between June 1, 2014 and July 31, 2016 in the Digestive Surgery Unit of the Hospital Regional of Talca were included. Results: There were 47 hepatectomies performed at the Hospital Regional of Talca. In 3 cases (6.3%), a 2-stage hepatectomy was performed using the ALPPS technique, in all of which a hypertrophy of the future hepatic remnant (RHF) was achieved, which allowed completing the second stage without POLF clinically significant. Conclusion: In our initial experience, the ALPPS technique successfully allowed increase FLR in patients who initially had insufficient FLR to be submitted a major liver resection.

Production of reuterin in a fermented milk product by Lactobacillus reuteri: Inhibition of pathogens, spoilage microorganisms, and lactic acid bacteria.

We assessed the antimicrobial activity of reuterin produced in vitro in glycerol aqueous solutions in situ by Lactobacillus reuteri ATCC 53608 as part of a fermented milk product against starter (Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus), spoilage (Penicillium expansum), pathogenic (Staphylococcus aureus Salmonella enterica ssp. enterica, and Listeria monocytogenes), and pathogen surrogate (Escherichia coli DH5α) microorganisms. We also assayed the influence of cold storage (28 d at 4°C) and reuterin on the color and rheology of the fermented milk product. We obtained maximum reuterin concentrations of 107.5 and 33.97 mM in glycerol aqueous solution and fermented milk product, respectively. Reuterin was stable throughout its refrigerated shelf life. Gram-positive microorganisms were more resistant to reuterin than gram-negative microorganisms. Penicillium expansum and Lactobacillus reuteri ATCC 53608 survived at concentrations up to 10 and 8.5 mM, respectively. Escherichia coli DH5α was the most sensitive to reuterin (0.9 mM). The presence of reuterin did not cause relevant changes in the quality parameters of the fermented milk product, including pH, acidity, soluble solids, color, and rheological aspects (storage and loss moduli and viscosity). This study demonstrated the viability of using Lactobacillus reuteri ATCC 53608 as a biopreservative in a fermented milk product through reuterin synthesis, without drastically modifying its quality parameters.

Clinical and color Doppler ultrasound evaluation of polyacrylamide injection in HIV patients with severe facial lipoatrophy secondary to antiretroviral therapy.

BACKGROUND/PURPOSE: Facial lipoatrophy in HIV patients, secondary to antiretroviral therapy (ART) with thymidine analogs, has been related to important psychosocial alterations and poor adherence to treatment. Polyacrylamide gel (PAAG) is a filler that has been used for treating facial lipoatrophy in HIV patients. The aim was to assess the clinical and sonographic anatomical changes after injection of PAAG in HIV patients with facial lipoatrophy secondary to ART. METHODS: HIV patients receiving ART and suffering from severe facial lipoatrophy were recruited and underwent clinical and color Doppler ultrasound evaluation prior to PAAG application (AQUAMID® ) and sonographically monitored at 18 months and clinically followed up for 36 months after the procedure. Adverse effects were recorded based on occurrence and complexity. RESULTS: A total of 33 patients were evaluated, 30 men (91%) and 3 women (9%) with an average age of 49.6 years (±8.4). Clinical improvement assessed by a dermatologist had an average score of 5.9 (±0.7) on a scale of 1-7. On color Doppler ultrasound there was a significant increase of the thickness of the subcutaneous tissue (SCT) in both nasofold lines when comparing before and after PAAG injection (P < 0.01) and no signs of inflammation (hypervascularity). User satisfaction was qualified as excellent or good in all cases. Only two patients experienced adverse effects (hematoma and puncture site infection), which was successfully managed without consequences. CONCLUSION: Treatment of facial lipoatrophy with PAAG seems to be effective in HIV patients and no signs of complications were observed in the monitoring at 36 months after injection. Color Doppler ultrasound can identify the filler deposits and the anatomical changes of the SCT non-invasively.

Codon Optimization of the "Bos Taurus Chymosin" Gene for the Production of Recombinant Chymosin in Pichia pastoris.

Codon optimization of the Bos taurus Chymosin gene (CYM) for its expression in Pichia pastoris was performed in this study. A synthetic CYM gene was designed in silico by replacing codons rarely used by P. pastoris with equivalent nucleotide combinations that codify for the same amino acid but that are more frequently encountered in the genome of P. pastoris. A total of 332 nucleotides were modified to optimize 289 codons. The synthetic CYM gene was cloned into the expression vector pPICZαA and transformed into P. pastoris. The transformed strains were grown in artificial media supplemented with glycerol as a carbon source to increase biomass and then cultured in a similar medium replacing glycerol with methanol as a carbon source to initiate gene induction. Raw extracts of the growth media exhibited milk-clotting activity of 146.11 SU/mL. Produced recombinant chymosin showed coagulant activity from 25 to 50 °C, and within a pH range of 5-6.9, having optimum activity at 35-40 °C, and pH 5.0. These results show that codon optimization is a viable strategy to improve CYM gene expression levels in P. pastoris for the production of recombinant chymosin.

Mesenchymal stromal cells overexpressing vascular endothelial growth factor in ovine myocardial infarction.

Mesenchymal stromal cells (MSCs) are cardioprotective in acute myocardial infarction (AMI). Besides, we have shown that intramyocardial injection of plasmid-VEGF(165) (pVEGF) in ovine AMI reduces infarct size and improves left ventricular (LV) function. We thus hypothesized that MSCs overexpressing VEGF(165) (MSCs-pVEGF) would afford greater cardioprotection than non-modified MSCs or pVEGF alone. Sheep underwent an anteroapical AMI and, 1 week later, received intramyocardial MSCs-pVEGF in the infarct border. One month post treatment, infarct size (magnetic resonance) decreased by 31% vs pre-treatment. Of note, myocardial salvage occurred predominantly at the subendocardium, the myocardial region displaying the largest contribution to systolic performance. Consistently, LV ejection fraction recovered to almost its baseline value because of marked decrease in end-systolic volume. None of these effects were observed in sheep receiving non-transfected MSCs or pVEGF. Although myocardial retention of MSCs decreased steeply over time, the treatment induced significant capillary and arteriolar proliferation, which reduced subendocardial fibrosis. We conclude that in ovine AMI, allogeneic VEGF-overexpressing MSCs induce subendocardial myocardium salvage through microvascular proliferation, reducing infarct size and improving LV function more than non-transfected MSCs or the naked plasmid. Importantly, the use of a plasmid rather than a virus allows for repeated treatments, likely needed in ischemic heart disease.

Assessing the yield, microstructure, and texture properties of miniature Chihuahua-type cheese manufactured with a phospholipase A1 and exopolysaccharide-producing bacteria.

Chihuahua cheese or Mennonite cheese is one of the most popular and consumed cheeses in Mexico and by the Hispanic community in the United States. According to local producers the yield of Chihuahua cheese ranges from 9 to 9.5 kg of cheese from 100 kg of milk. Cheese yield is a crucial determinant of profitability in cheese-manufacturing plants; therefore, different methods have been developed to increase it. In this work, a miniature Chihuahua-type cheese model was used to assess the effect of a phospholipase A1 (PL-A1) and exopolysaccharide (EPS)-producing bacteria (separately and in combination) on the yield, microstructure, and texture of cheese. Four different cheeses were manufactured: cheese made with PL-A1, cheese made with EPS-producing bacteria, cheese with both PL-A1 and EPS-producing bacteria, and a cheese control without PL-A1 or EPS-producing bacteria. The compositional analysis of cheese was carried out using methods of AOAC International (Washington, DC). The actual yield and moisture-adjusted yield were calculated for all cheese treatments. Texture profile analyses of cheeses were performed using a texture analyzer. Micrographs were obtained by electron scanning microscopy. Fifty panelists carried out sensorial analysis using ranking tests. Incorporation of EPS-producing bacteria in the manufacture of cheese increased the moisture content and water activity. In contrast, the addition of PL-A1 did not increase fat retention or cheese yield. The use of EPS alone improved the cheese yield by increasing water and fat retention, but also caused a negative effect on the texture and flavor of Chihuahua cheese. The use of EPS-producing bacteria in combination with PL-A1 improved the cheese yield and increased the moisture and fat content. The cheeses with the best flavor and texture were those manufactured with PL-A1 and the cheeses manufactured with the combination of PL-A1 and EPS-producing culture.

Microsomal oxidative stress induced by NADPH is inhibited by nitrofurantoin redox biotranformation.

Nitrofurantoin is used in the antibacterial therapy of the urinary tract. This therapy is associated with various adverse effects whose mechanisms remain unclear. Diverse studies show that the nitro reductive metabolism of nitrofurantoin leads to ROS generation. This reaction can be catalyzed by several reductases, including the cytochrome P450 (CYP450) reductase. Oxidative stress arising from this nitro reductive metabolism has been proposed as the mechanism underlying the adverse effects associated with nitrofurantoin. There is, however, an apparent paradox between these findings and the ability of nitrofurantoin to inhibit lipid peroxidation provoked by NADPH in rat liver microsomes. This work was aimed to show the potential contribution of different enzymatic systems to the metabolism of this drug in rat liver microsomes. Our results show that microsomal lipid peroxidation promoted by NADPH is inhibited by nitrofurantoin in a concentration-dependent manner. This suggests that the consumption of NADPH in microsomes can be competitively promoted by lipid peroxidation and nitrofurantoin metabolism. The incubation of microsomes with NADPH and nitrofurantoin generated 1-aminohidantoin. In addition, the biotransformation of a classical substrate of CYP450 oxidative system was competitively inhibited by nitrofurantoin. These results suggest that nitrofurantoin is metabolized through CYP450 system. Data are discussed in terms of the in vitro redox metabolism of nitrofurantoin.

Oral manifestations and their treatment in Sjögren's syndrome.

Sjögren's syndrome (SS) is a complex, chronic, systemic, autoimmune disease that mainly affects the exocrine glands, especially the salivary and lacrimal glands, leading to dryness of the oral and ocular mucosae. Several factors have been studied that could explain the glandular hypofunction primarily related to water transport. Recent reports have shown alterations in secretory route and trafficking in labial salivary glands, explaining alterations in the saliva quality. The decrease in salivary flow and qualitative alterations in saliva could explain many of the oral manifestations. The exocrine manifestations and systemic involvement significantly impact the patient's perception of health-related quality of life. For this reason and given its systemic nature, the treatment of these patients should be multidisciplinary. This review addresses some particular oral health aspects of SS patients and focuses on relevant topics concerning the treatment and prevention of common oral disorders associated with this disease.

Análisis de la unidad funcional cutánea de tórax anterior para el movimiento de abducción completa de hombro en niños sanos de 7 a 10 años de edad / Anterior thorax cutaneous functional unit analysis of complete shoulder abduction movement in healthy 7 to 10 year old children

Introduction: cutaneous functional units (CFU) are predilected skin areas that determine the skin recruitment necessary for complete range of movement. Finding out the characteristics of CFU in healthy children, would allow for better diagnostics and prevent burn scar contractures. Objective: to determine angular displacement of CFU in anterior thorax (AT), for complete shoulder abduction movement, in healthy children between 7-10 years of age. Methods and material: a descriptive study of 42 healthy children at COANIQUEM, Santiago 2011, was developed. Independent photographs were taken of each child in a neutral position and in maximal abduction range for both shoulders. AT length was measured, and a vertical line was drawn dividing the thorax into two hemibodies with ten symmetric spaces or percentage units (PU). Photographs were analyzed through double exposure with Photoshop CS3 Extended®. AT skin recruitment, elongation and angulation measures were obtained. Results: while in upper extremity abduction, 59.5 percent of the children recruited AT skin up to PU 100 in the right shoulder, and up to 66.7 percent in the left shoulder, a non significant difference. Greatest AT skin displacement was produced at line four, while PU 50 achieved greatest elongation. Greatest angle displacement was observed at PU 10, with a meaningful difference between shoulders. Conclusion: CFU of AT for complete shoulder abduction movement is wider in children than in adults. Skin tension is greater among PU’s from the central portion of the chest.

Introducción: las unidades funcionales cutáneas (UFC), son campos de piel que determinan el reclutamiento de piel necesario para permitir el movimiento recluta completo de hombro. Conocer las características de UFC en niños sanos, permitiría mejorar diagnóstico y prevenir retracciones cicatriciales en secuelados por quemaduras. Objetivo: determinar el desplazamiento angular de UFC en tórax anterior (TA), de niños sanos entre 7-10 años, para el movimiento de abducción completa de hombro. Materiales y métodos: estudio descriptivo de 42 niños/as sanos en COANIQUEM Santiago 2011. A cada niño se tomó una fotografía de TA en posición neutra y otra en rango máximo de abducción de ambos hombros en forma independiente. Se midió longitud del TA y se trazó una línea vertical dividiendo el tronco en dos hemicuerpos con 10 espacios simétricos o unidades porcentuales (UP). Las fotografías se analizaron con doble exposición mediante Photoshop CS3 Extended®; se obtuvieron medidas de reclutamiento de piel, elongación y angulación de piel de TA. Resultados: el 59,5 por ciento de los niños en abducción de extremidad superior, reclutó piel de TA hasta la UP 100 en hombro derecho y el 66,7 por ciento en hombro izquierdo, diferencia no significativa. El mayor desplazamiento de piel del TA, se produjo en línea 4; la UP 50 logró mayor elongación; el mayor ángulo de desplazamiento se produjo en UP 10, con diferencia significativa entre ambos hombros. Conclusión: la UFC de TA para el movimiento de abducción del hombro, es más ancha que en adultos. La tensión de la piel es más alta en unidades porcentuales de la parte central del pecho.

Sjögren's syndrome and the epithelial target: a comprehensive review.

The most difficult component in our understanding of human autoimmunity remains a rigorous dissection of etiological events. Indeed, the vast literature on autoimmune diseases focuses on the inflammatory response, with the hope of developing drugs that reduce inflammation. However, there is increasing recognition that understanding the immunobiology of target tissues will also have direct relevance to disease natural history, including breach of tolerance. Sjögren's syndrome is essentially an epitheliitis and there are major changes to normal architectural salivary organization. We propose that loss of homeostasis is the initial event that precipitates inflammation and that such inflammatory response includes not only the adaptive response, but also an intense innate immune/bystander response. To understand these events this review focuses on the architecture, phenotype, function and epithelial cell organization. We further submit that there are several critical issues that must be defined to fully understand epithelial cell immunobiology in Sjögren's syndrome, including defining epithelial cell polarity, cell-cell and cell to extracellular matrix interactions and a variety of chemical and mechanical signals. We also argue that disruption of tight junctions induces disorganization of the apical pole of salivary acinar cells in Sjögren's syndrome. In addition, there will be a critical role of inflammatory cytokines in the apico-basal relocation of tight junction proteins. Further, the altered disorganization and relocation of proteins that participate in secretory granule formation are also dysregulated in Sjögren's syndrome and will contribute to abnormalities of mucins within the extracellular matrix. Our ability to understand Sjögren's syndrome and develop viable therapeutic options will depend on defining these events of epithelial cell biology.

Effects of light activation, agent concentration, and tooth thickness on dental sensitivity after bleaching.

UNLABELLED: Examining three bleaching systems, this in vivo clinical trial evaluated the relationship among tooth sensitivity, light activation, and agent concentration, and it correlated dental sensitivity with tooth thickness. MATERIALS AND METHODS: Eighty-seven volunteer patients were included. Inclusion criteria were the presence of anterior teeth without restorations as well as the absence of a previous bleaching experience and absence of noncarious cervical lesions or dental pain. Exclusion criteria included pregnancy or breastfeeding, a maximum of TF3 hypoplasia, tetracycline-fluorosis stains, malpositioned teeth, orthodontic treatment, periodontal disease, and/or analgesic/anti-inflammatory intake. Patients were randomly assigned to three bleaching groups: Group A (n=25) was treated with 15% H2O2 and nitrogenous-titanium-dioxide and was light activated (Lase Peroxide Lite, DMC, SaoCarlos, Sao Paulo, Brazil); Group B (n=27) was treated with 35% H2O2 and was light activated (Lase Peroxide Sensy, DMC); and Group C (n=35) was treated with 35% H2O2 (White Gold Office, Dentsply, 38West Clark Ave., Milford, USA) without light activation. Tooth sensitivity (TS) was self-reported by the patients using the visual analog scale (VAS) at baseline (TS0), immediately after treatment (TSI), and at seven days after treatment (TS7). In 46 patients, tooth thickness was determined by computed tomography. TS0, TSI, and TS7 were compared between the A and B groups to determine the effect of concentration and between the B and C groups to determine the effect of light using analysis of covariance. The correlation between tooth thickness and TSI was determined by Spearman Rho test (SPSS 15). RESULTS: Eighty-seven patients were evaluated at baseline, and 61 were evaluated at seven days. Separated by groups, tooth sensitivity, expressed as VAS value at the time points TS0, TSI, and TS7, respectively, were as follows: Group A: 13.76 ± 13.53, 24.40 ± 25.24, and 5.94 ± 5.5; Group B: 15.07 ± 18.14, 42.4 ± 31.78, and 8.68 ± 17.99; and Group C: 10.80 ± 14.83, 31.51 ± 29.34, and 7.24 ± 9.2. Group A showed significantly lower tooth sensitivity than group B at TSI (p=0.032). No differences were observed in the tooth sensitivities between groups B and C. No correlation was encountered between tooth thickness and tooth sensitivity immediately after treatment (Rho=-0.088, p=0.563). The median tooth thickness was 2.78 ± 0.21 mm. CONCLUSIONS: Increases in the concentration of bleaching agents directly affect tooth sensitivity, and LED/laser activation and tooth thickness are not correlated with tooth sensitivity after dental bleaching.