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Introduction. The currently available dosimetry techniques in computed tomography can be inaccurate which overestimate the absorbed dose. Therefore, we aimed to provide an automated and fast methodology to more accurately calculate the SSDE usingDwobtained by using CNN from thorax and abdominal CT study images.Methods. The SSDE was determined from the 200 records files. For that purpose, patients' size was measured in two ways: (a) by developing an algorithm following the AAPM Report No. 204 methodology; and (b) using a CNN according to AAPM Report No. 220.Results. The patient's size measured by the in-house software in the region of thorax and abdomen was 27.63 ± 3.23 cm and 28.66 ± 3.37 cm, while CNN was 18.90 ± 2.6 cm and 21.77 ± 2.45 cm. The SSDE in thorax according to 204 and 220 reports were 17.26 ± 2.81 mGy and 23.70 ± 2.96 mGy for women and 17.08 ± 2.09 mGy and 23.47 ± 2.34 mGy for men. In abdomen was 18.54 ± 2.25 mGy and 23.40 ± 1.88 mGy in women and 18.37 ± 2.31 mGy and 23.84 ± 2.36 mGy in men.Conclusions. Implementing CNN-based automated methodologies can contribute to fast and accurate dose calculations, thereby improving patient-specific radiation safety in clinical practice.

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The development of rHDL-radionuclide theragnostic systems requires evaluation of the absorbed doses that would be produced in healthy tissues and organs at risk. Technetium-99m is the most widely used radionuclide for diagnostic imaging, therefore, the design of theragnostic reconstituted high density-lipoprotein (rHDL) nanosystems labeled with Technetium-99m offers multiple possibilities. OBJECTIVE: To determine the biokinetics, radiopharmacokinetics and estimate the absorbed doses induced in healthy organs by Technetium-99m transported in the core and on the surface of rHDL. METHODS: Biokinetic and radiopharmacokinetic models of rHDL/[99mTc]Tc-HYNIC-DA (Technetium-99m in the core) and [99mTc]Tc-HYNIC-rHDL (Technetium-99m on the surface) were calculated from their ex vivo biodistribution in healthy mice. Absorbed doses were estimated by the MIRD formalism using OLINDA/EXM and LMFIT softwares. RESULTS: rHDL/[99mTc]Tc-HYNIC-DA and [99mTc]Tc-HYNIC-rHDL show instantaneous absorption in kidney, lung, heart and pancreas, with slower absorption in spleen. rHDL/[99mTc]Tc-HYNIC-DA is absorbed more slowly in the intestine, while [99mTc]Tc-HYNIC-rHDL is absorbed more slowly in the liver. The main target organ for rHDL/[99mTc]Tc-HYNIC-DA, which is hydrophobic in nature, is the liver, whereas the kidney is for the more hydrophilic [99mTc]Tc-HYNIC-rHDL. Assuming that 925 MBq (25 mCi) of Technetium-99m, carried in the core or on the surface of rHDL, are administered, the maximum tolerated doses for the organs of greatest accumulation are not exceeded. CONCLUSION: Theragnostic systems based on 99mTc-labeled rHDL are safe from the dosimetric point of view. The dose estimates obtained can be used to adjust the 99mTc-activity to be administered in future clinical trials.

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Although liposomal doxorubicin (LPD) is widely used for cancer treatment, knowledge concerning the toxicity induced by this drug in healthy organs and tissues is limited. LPD-induced toxicity studies relative to free doxorubicin (DOX) have focused on cardiotoxicity in tumor-bearing animals. On the other hand, the results on DOX-induced cardiotoxicity depending on gender are controversial. One of the manifestations of toxicity is tissue inflammation. 67Ga-citrate has been used for decades to assess inflammation in various pathologies. In this work, the ex vivo biodistribution of 67Ga-citrate is used to evaluate induced multi-organ toxicity in healthy 10-week-old male and female CD1 mice treated for 5 weeks with LPD. Toxicity in males, determined by 67Ga-citrate, was evident only in the target organs of liposomes (spleen, liver, kidneys, and lungs); the average weight loss was 11% and mortality was 14%. In female mice, 67Ga-citrate revealed a cytotoxic effect in practically all organs, the average weight loss was 37%, and the mortality after the last dose of LPD was 66%. These results confirm the usefulness of 67Ga-citrate and the importance of stratifying by sex in the toxicological evaluation of drugs.

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Reconstituted high-density lipoprotein (rHDL) nanoparticles are excellent transporters of molecules and very useful for targeted therapy as they specifically recognize the scavenger receptor, class B1 (SR-B1) that is present on the surface of a wide range of tumor cells. However, they have rarely been employed to transport photosensitizers (PS) for photodynamic therapy (PDT). Rhodamine (R) compounds have been dismissed as useful PSs for PDT due to their low 1O2 production, excitation wavelengths with little tissue penetration, and poor selectivity for tumor cells. It was recently demonstrated that when irradiating at 532 nm or with Cerenkov radiation (CR) from a ß-emitting radionuclide, R123, R6G, and RB undergo electron transfer reactions (type I reaction) with folic acid. R6G also produces type I reactions with O2. In this work, the photodynamic effects of the rHDL-R system were evaluated in vitro. rHDL nanoparticles loaded with R123, R6G, and RB were synthesized, and the PS was internalized into T47D tumor cells. When cells were irradiated with a 532-nm laser in the presence of an rHDL-R systems, a cytotoxic photodynamic effect was obtained in the order R6G > R123 > RB. In the presence of CR from a 177Lu source, cytotoxicity showed the order R6G > RB > R123. The higher cytotoxicity induced by R6G in both cases corresponds to higher cellular internalization and larger production of type I and II reactions. Thus, in this work, it is proposed that rHDL-R/177Lu system can be applied in theragnostics as a multimodal radiotherapy-PDT-imaging system (imaging by SPECT or Cerenkov) and in hypoxic solid tumors in which external radiation is not effective and 177Lu-CR acts as light source.

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Recently, it was demonstrated that doxorubicin (Dox.HCl), a chemotherapeutic agent, could be photoactivated by Cerenkov radiation (CR). The objective of the present work was to develop a multimodal chemotherapy-radiotherapy-photodynamic therapeutic system based on reconstituted high-density lipoprotein (rHDL) loaded with Dox.HCl and 177Lu-DOTA. 177Lu acts as a therapeutic radionuclide and CR source. The system can be visualized by nuclear imaging. Fluorescence microscopy showed that rHDL-Dox specifically recognized cancer cells (T47D) that are positive for SR-B1 receptors. Encapsulated Dox.HCl was released into the cells and produced reactive oxygen species when irradiated with a 450-nm laser (photodynamic effect). The same effect occurred when Dox.HCl was irradiated by 177Lu CR. Through in vitro experiments, it was confirmed that the addition of 177Lu-DOTA to the rHDL-Dox nanosystem did not affect the specific recognition of SR-B1 receptors expressed in cells, or the cellular internalization of 177Lu-DOTA. The toxicity induced by the rHDL-Dox/177Lu nanosystem in cell lines with high (T47D and PC3), poor (H9C2) and almost-zero (human fibroblasts (FB)) expression of SR-B1 was evaluated in vitro and confirmed the synergy of the combined chemotherapy-radiotherapy-photodynamic therapeutic effect; this induced toxicity was proportional to the expression of the SR-B1 receptor on the surface of the cells used. The HDL-Dox/177Lu nanosystem experienced uptake by tumor cells and the liver-both tissues with high expression of SR-B1 receptors-but not by the heart. 177Lu CR offered the possibility of imparting photodynamic therapy where laser light could not reach.

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The search for methods that identify early toxicity, induced by chemotherapy, is urgent. Changes in the biodistribution of radiopharmaceuticals could give information on early toxicity. Ten-week-old CD1 male mice were divided into four groups. Two groups were administered a weekly dose of 5 mg/kg of doxorubicin hydrochloride (DOX) for 5 weeks and the control groups were administered saline solution. One week after the end of treatment, the biodistribution of 18F-FDG and 67Ga-citrate were carried out, as was the quantification of plasma enzymes CK, CK-MB, LDH and AST. All enzymes were higher in the treated animals, but only significant (p < 0.05) in the case of CK-MB. 18F-FDG uptake increased in all organs of treated animals except retroperitoneal fat, being significant in spleen, brain, heart, liver, lung, kidney, and inguinal fat. 67Ga-citrate had a more complex pattern. The uptake in the DOX group was higher in spleen, lung, kidney, testes, and gonadal fat, it did not change in brain, heart, and liver, and it was lower in the rest of the organs. It only showed significant differences in lung and pancreas. A thorough discussion of the possible causes that produced the change in biodistributions of both radiopharmaceuticals is included. The pilot study showed that both radiopharmaceuticals could identify early multi-organ toxicity induced by DOX. Although 18F-FDG seems to be better, 67Ga-citrato should not be ruled out a priori. The detection of early toxicity would serve to adopt treatments that prevent its progression, thus improving patient's quality of life.

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AIM: The aim of the present work was to determine if both ovariectomy (OVX) and type 2 diabetes mellitus (T2DM) can change X-ray absorptiometry until reach the osteoporosis condition. RESULTS: The segmentation allowed us to quantitatively determine the X-ray absorption in the femurs of mice subjected to OVX, T2DM and both pathologies together. CONCLUSIONS: The test subjects suffering from the mentioned pathologies separately or together, did not reach the osteoporosis condition when they were 30 weeks old.

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Doxorubicin (DOX), an effective chemotherapeutic agent, has a wide excitation band centred at 480 nm. Cerenkov radiation (CR) is considered an internal light source in photodynamic therapy (PDT). DOX could be photoactivated by CR and thus, enhancing its cytotoxicity. In this work, 18F-FDG was used to evaluate the effect of Cerenkov radiation on DOX, in comparison to irradiation with a 450-nm laser beam, in terms of ROS production. The production of 1O2 and O2⁎- reactive species during DOX irradiation was detected indirectly by ABMA and DCPIP bleaching, respectively. The cytotoxic effect of the DOX / 18F-FDG CR system was evaluated in the T47D breast cancer cell line. The irradiation of DOX produced 1O2 and O2⁎- species using both 18F-FDG CR and a 450-nm laser beam. The majority reactive species produced in both cases was 1O2; a favourable result, given the greater cytotoxicity of this species. The viability of T47D cells in presence of DOX (5 nM), 18F-FDG (37.5 µCi) and DOX (5 nM)/18F-FDG (37.5 µCi) was (86 ± 9)%, (84 ± 8)% and (64 ± 5)%, respectively; these results suggest a synergistic cytotoxic effect derived from the cytotoxic activity of DOX and its photoactivation by 18F-FDG CR. It is worth noting that the system could be optimized in terms of DOX concentration and 18F-FDG activity for better results. Due to the fact that 18F-FDG is widely used in nuclear imaging, the DOX/18F-FDG system also possesses theragnostic characteristics. Thus, in this work, it is demonstrated that DOX can be used in a dual therapy system based on chemotherapy-PDT when 18F-FDG CR is used as a DOX excitation source.

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Introduction: Microleakage has been reported to cause dentin hypersensitivity because of the passage of bacteria and their products through the restoration-tooth interface and is one of the main reasons for replacement of restorations. CO2 laser can be used for treatment of dentin hypersensitivity. Thus, this study aimed to evaluate in vitro the microleakage in composite restorations following surface pretreatment with acid etching and CO2 laser. Methods: Twelve human caries-free primary molars were selected. Class II cavities were prepared on occlusal mesial and occlusal distal surfaces. Specimens were randomly divided into four groups (n=6): Group 1 (G1) - 37% phosphoric acid gel etching + Beautiful-Bulk Restorative - Giomer (Shofu Inc); Group 2 (G2) - 37% phosphoric acid gel etching + SDR Bulk-Fill Flow (Dentsply); Group 3 (G3) - CO2 laser irradiation + Beautiful-Bulk Restorative - Giomer (Shofu Inc); Group 4 (G4) - CO2 laser irradiation + SDR Bulk-Fill Flow (Dentsply). Surfaces were restored with bonding agent (Natural Bond DE, DFL). Specimens were cut longitudinally and immersed in 0.5% methylene blue solution for 4 hours. Microleakage scores were assessed under a magnifying glass at x3,5 and qualitatively analyzed by scanning electron microscope (SEM). Data were analyzed using nonparametric Wilcoxon test (P < 0.05). Results: Scores prevailed between 0 and 2, however, no statistically significant difference was found among the groups (P = 0.05). Conclusion: It could be concluded that all composite resins bulk fill did not show significant difference among them regarding microleakage using either CO2 laser or 37% phosphoric acid etching.

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Cerenkov radiation (CR) is the emission of UV-vis light generated by the de-excitation of the molecules in the medium, after being polarized by an excited particle traveling faster than the speed of light. When ß particles travel through tissue with energies greater than 219 keV, CR occurs. Tissues possess a spectral optical window of 600 to 1100 nm. The CR within this range can be useful for quantitative preclinical studies using optical imaging and for the in-vivo evaluation of Lu177-radiopharmaceuticals (ß-particle emitters). The objective of our research was to determine the experimental emission light spectrum of Lu177-CR and evaluate its transmission properties in tissue as well as the feasibility to applying CR imaging in the preclinical studies of Lu177-radiopharmaceuticals. The theoretical and experimental characterizations of the emission and transmission spectra of Lu177-CR in tissue, in the vis-NIR region (350 to 900 nm), were performed using Monte Carlo simulation and UV-vis spectroscopy. Mice Lu177-CR images were acquired using a charge-coupled detector camera and were quantitatively analyzed. The results demonstrated good agreement between the theoretical and the experimental Lu177-CR emission spectra. Preclinical CR imaging demonstrated that the biokinetics of Lu177-radiopharmaceuticals in the main organs of mice can be acquired.

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The therapeutic potential of 177Lu-iPSMA on hypoxic cancer cells has not been yet demonstrated. The aim of this work was to evaluate the radiation dose effect of 177Lu-iPSMA on viability and DNA damage in U87MG human glioma cells subjected to hypoxia-mimetic conditions. U87MG cells treated with 177Lu-iPSMA were incubated with CoCl2 in order to induce hypoxia-mimetic conditions. The cytotoxic and genotoxic effect was evaluated with an in vitro viability test and a neutral comet assay. 177Lu-iPSMA decreased the cell viability and induced DNA double strand breaks in U87MG human glioma cells under hypoxia-mimetic conditions. 177Lu-iPSMA produced the maximum effect at 48 h, suggesting that this radiopharmaceutical could be used as a strategy for the treatment of human glioma hypoxic cells.

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The aim of this work was to calculate S values for 99mTc, 67Ga, 68Ga, 18F, 223Ra, 166Ho, 90Y, 161Tb 131I and 177Lu, using a mouse phantom (MOBY) standard and considering the anatomic sizes from males and females, the simulation of radiation transport was performed with GATE/Geant4 platform. This indicates that in the internal dosimetry the use of a customized geometry is relevant for each gender and a standard model is not a good choice.

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Glioblastoma contains self-renewing, tumorigenic cancer stem-like cells that contribute to tumor initiation and therapeutic resistance. The aim of this research was to estimate and compare the effectiveness ratio (α/ß) of stem-like cells and differentiated glioma cells derived from the U87MG glioblastoma cell line. Cell survival experiments were obtained in a dose range of 0-20 Gy (13.52 ± 0.09 Gy/h) as a hyperfractionationated accelerated radiotherapy scheme. Biochemical characterization of the post-irradiated cells was performed by flow cytometry analysis and the percentage of stem-like cells that resisted irradiation was determined by the CD133 expression. Results showed that U87MG stem-like cells are highly proliferative and more radioresistant than the U87MG adherent group (with a lesser stem-like character), this in association with the calculated α/ß ratio of 17 and 14.1, respectively.

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The aim of this work was to develop an event-by-event Monte Carlo code for light transport (called MCLTmx) to identify and quantify ballistic, diffuse, and absorbed photons, as well as their interaction coordinates inside the biological tissue. The mean free path length was computed between two interactions for scattering or absorption processes, and if necessary scatter angles were calculated, until the photon disappeared or went out of region of interest. A three-layer array (air-tissue-air) was used, forming a semi-infinite sandwich. The light source was placed at (0,0,0), emitting towards (0,0,1). The input data were: refractive indices, target thickness (0.02, 0.05, 0.1, 0.5, and 1 cm), number of particle histories, and λ from which the code calculated: anisotropy, scattering, and absorption coefficients. Validation presents differences less than 0.1% compared with that reported in the literature. The MCLTmx code discriminates between ballistic and diffuse photons, and inside of biological tissue, it calculates: specular reflection, diffuse reflection, ballistics transmission, diffuse transmission and absorption, and all parameters dependent on wavelength and thickness. The MCLTmx code can be useful for light transport inside any medium by changing the parameters that describe the new medium: anisotropy, dispersion and attenuation coefficients, and refractive indices for specific wavelength.

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The aim of the present study was to determine the iron needs in different organs and tissues using 67Ga as a biosensor in males and females rats subjected to iron deficiency (ID) and voluntary exercise (EX). 67Ga citrate was injected i.p. to female and male Wistar rats (n=5/sex/group). Groups: Control (sedentary conditions), Control+EX, ID and ID+EX. To determine the 67Ga uptake, samples from the following regions of interest (ROIs) were extracted 12h post-injection: blood, liver, gonads, bone marrow, heart, adrenal glands, skeletal muscle, stomach, kidney, eyeball, sciatic nerve, small intestine and peritoneum. The total 67Ga uptake was 412% higher in ID subjects than in control subjects, being 1011% higher in ID-males than ID-females. In ID-females, the ROIs with the greater 67Ga uptake were blood, kidney and bone marrow, while in ID-males they were sciatic nerve, eyeball and adrenals, which demonstrates that the biodistribution differed between sexes in sedentary conditions but when subjected to EX, the biodistribution was similar in each sex group although females had a greater 67Ga uptake. In ID+EX subjects, the ROIs that showed the highest uptake were sciatic nerve, eyeball and adrenal glands. Using 67Ga as a biosensor, it is possible to identify the needs of iron that each organ requires to perform their functions in normal physiological conditions. In addition, a higher or lower 67Ga uptake in a specific organ may indicate its malfunction or show damage.

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En odontopediatría, una de las principales dificultades que se presenta en la remoción del tejido dental cariado, es el manejo del paciente niño debido al miedo y a la ansiedad por el uso de anestesia e instrumentos rotatorios. A fin de resolver este problema, el método químico-mecánico para la eliminación del tejido cariado, es una alternativa conservadora y eficaz ya que evita el uso de anestésicos e instrumental rotatorio. Según estudios, este método es más aceptado por los pacientes comparado con el método tradicional. Este artículo tiene como objetivo presentar un caso clínico del uso del gel a base de papaína (Papacárie ®) para la eliminación químico-mecánica del tejido cariado en dientes permanentes.

anesthesia and rotating instruments. In order to solve this problem, the chemical-mechanical method for the elimination of the carious tissue, is a conservative and effective alternative since it avoids the use of anesthetics and rotary instruments. According to studies, this method is more accepted by patients compared to the traditional method. This paper aims to present a clinical case of the use of papain gel (Papacárie ®) for the chemical-mechanical removal of carious tissue in permanent teeth.

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[Purpose] Problems involving the temporomandibular joint and associated structures can lead to temporomandibular disorder (TMD). The aim of the present study was to evaluate muscle activity in individuals with a diagnosis of TMD before and after treatment with low-level laser therapy (LLLT) through the use of electromyography (EMG). [Subjects and Methods] Male and female individuals aged 14 to 23 years were evaluated. TMD was determined by a clinical examination and the administration of the Research Diagnostic Criteria for Temporomandibular Disorders, followed by the evaluation of sensitivity to palpation of the masseter and anterior temporal muscles as well as the EMG determination of muscle activity. The participants were randomly allocated to an active LLLT group (n=9) and sham group (n=7). Twelve sessions of LLLT were conducted using a wavelength of 780 nm, energy density of 25 J/cm2, power of 50 mW, power density of 1.25 W/cm2 and a 20-second exposure time or sham LLLT. Muscle activity was determined prior to treatment and after the last session. [Results] During the isometric evaluation of the masseter and anterior temporal muscles, an increase in the mean EMG signal was found in the group submitted to active LLLT. When evaluated individually, some participants in the active LLLT group demonstrated a reduction in muscle activity, but no significant differences were found in the mean EMG signal between the initial and final evaluations. [Conclusion] Further studies with a larger sample size are needed to confirm the present findings.

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Abstract: objective: this study evaluated the influence of fiber composition, diameter and post-curing treatments performed at relining on flexural strength and modulus of fiber-posts. Materials and methods: Sixty posts of Reforpost® Glass Fiber [GF]) and Reforpost® Carbon Fiber [CF] (Angelus, Londrina, PR, Brazil) with diameters of 1.0mm and 1.4mm were used. Each group was further subdivided into three subgroups (n=5) according to treatment received: dry-stored control group (C), oven-cured (Ov) or autoclaved (Ac). A universal testing machine measured flexural strength and modulus of all specimens. results: post composition and post-curing treatments had no significant effects on flexural properties of specimens while post diameter had significant effects (p<0.05). The highest flexural strength and modulus (MPa) (1331 +/- 95.8 and 21532 +/- 1550, respectively) were obtained with Ov/GF/1.1, while lowest values (890 +/- 79.4 and 10675 +/- 952, respectively) were for Ac/GF/1.5. Conclusions: 1.1mm diameter posts had better mechanical properties than 1.5mm thick posts. Neither post composition nor post-curing procedures affected the mechanical properties of relined posts.

Resumen: objetivo: este estudio evaluó la influencia de la composición, diámetro y métodos de post-curado usados para reembasado en la resistencia y modulo flexural de postes de fibra de vidrio. Materiales y métodos: sesenta postes de fibra de vidrio [GF]) y de carbono [CF] (Reforpost®, Angelus, PR, Brazil) con diámetros entre 1 y 1,4mm fueron utilizados. Cada grupo fue subdividido en 3 subgrupos (n=5) según el tratamiento recibido: grupo control almacenado en seco (C), post-curado en horno (Ov) o autoclavados (Ac). Las pruebas de medición de resistencia y modulo flexural fueron ejecutados en una maquina de pruebas universal. Resultados: La composición y los métodos de post-curado no tuvieron influencia significante en las propiedades testadas. Por otro lado, el factor diámetro tuvo influencia significante (p< 0,05). Los mayores valores de resistencia flexural y modulo flexural (MPa) (1331 +/- 95,8 y 21532 +/- 1550,0 respectivamente) fueron obtenidos con Ov/GF/1,1, mientras que los valores mas bajos (890 +/- 79,4 y 10675 +/- 952, respectivamente) fueron para Ac/GF/1,5. Conclusiones: Los postes de 1,1mm de diámetro presentan mejores propiedades mecánicas que los de mayor diámetro. La composición de los postes y el método de post-curado no afectaron las propiedades testeadas.

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This in vitro study evaluated the influence of two devices for application of shear load in microshear tests on bond strength and fracture pattern of primary enamel and dentin. Eighty primary molars were selected and flat enamel (40 teeth sectioned mesio-distally) and dentin (40 teeth sectioned transversally) surfaces were obtained. Both surfaces were polished to standardize the smear layer. Two-step etch-and-rinse adhesive systems (Adper Single Bond and XP Bond) were used. Polyethylene tubes was placed over the bonded surfaces and filled with composite resin. The microshear testing was performed after storage in water (24 h/37 °C) using two devices for application of microshear loads: a notched rod (Bisco Shear Bond Tester) or a knife edge (Kratos Industrial Equipment). Failure modes were evaluated using a stereomicroscope. Bond strength data were subjected to ANOVA and chi-square test to compare the failure mode distributions (α=0.05). No significant differences were observed between the groups for dentin and enamel bond strength or fracture patterns (p>0.05). The predominant failure mode was adhesive/mixed. In conclusion, the devices for application of shear loads did not influence the bond strength values, regardless of adhesive system and substrate.

Este estudo in vitro avaliou a influência de dois dispositivos para aplicação de força de cisalhamento em testes de resistência de união ao microcisalhamento e no padrão de fratura em dentina e esmalte de dentes decíduos. Oitenta molares decíduos foram selecionados e superficies planas em esmalte (40 dentes seccionados no sentido mésio-distal) e dentina (40 dentes seccionados transversalmente) foram obtidas. Ambas as superficies foram abrasionadas para padronização da lama dentinária. Dois sistemas adesivos de condicionamento ácido prévio (Adper Single Bond e XP Bond) foram utilizados. Tubos de polietileno foram colocados sobre as superficies, nas quais já haviam sido aplicados os sistemas adesivos, e preenchidos com resina composta. O teste de resistência de união ao microcisalhamento foi realizado após armazenamento dos espécimes em água (24 h/37 °C) utilizando dois dispositivos para a aplicação das forças de cisalhamento: cisalha côncava (Bisco Shear Bond Tester) e cisalha plana (Kratos Industrial Equipment). O padrão de fratura foi avaliado usando estereomicroscópio. Os dados de resistência de união foram submetidos à ANOVA e o teste quiquadrado foi utilizado para comparar a distribuição dos padrões de fratura (α=0,05). Não foram observadas diferenças estatisticamente significantes entre os grupos, tanto para a resistência de união a dentina e esmalte quanto para o padrão de fratura (p>0,05). O modo de falha predominante foi adesiva/mista. Em conclusão, os dispositivos para aplicação de força de cisalhamento não influenciam os valores de resistência de união, independente do sistema adesivo e substrato.

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Objetivo: el objetivo de este estudio fue comparar la resistencia a la compresión de resinas compuestas a base de silorano y a base de metacrilato. Materiales y métodos: treinta muestras con formato de disco, fueron confeccionadas insertando las resinas, de forma incremental, en una matriz de aluminio (10 cm de diámetro x 15 mm de alto). El tiempo de fotoactivación de cada incremento fue de 20 segundos (Filtek P60, 3M ESPE) y 40 segundos (Filtek P90, 3M ESPE), utilizando una lámpara de luz halógena a 500 mW/cm2. LUego de ser almacenadas en agua destilada a 23 +- 2ºC y 50 +-5 por ciento de humedad relativa durante 40 horas, las muestras fueron sometidas al test de resistencia a la compresión, en una máquina de ensayos universal (1,3 mm/min). Los datos (en MPa) fueron analizados estadísticamente mediante ANOVA y prueba de Tukey (alfa=0,05). Resultados: los valores de resistencia a la compresión de P60 fueron estadísticamente superiores a los de P90 (P60=371,91 +- 58,76; P90=264,41+-30,33). Conclusión: las resinas compuestas a base de silorano presentaron los valores más bajos de resistencia a la compresión.

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