Influência da manipulação na elasticidade de siliconas de adição em consistência de massa

The handling of vinyl polysiloxane (addition silicone) impression putties with latex gloves is said to interfere with the setting of these impression materials. The aim of this study is to evaluate the effect of handling techniques on the setting of vinyl polysiloxane impression putties using several types of gloves. The setting of these materials was evaluated by means of an elasticimeter. Four vinyl polysiloxane putty impression materials and five brands of gloves (one made of vinyl, one of synthetic rubber, and three of natural rubber) were studied. Based on the type of glove, they were previously washed or not, and a spatula was used or not for initial mixing (before handmixing). The vinyl, the synthetic and one of the natural rubber gloves did not require the previous washing procedure and/or the use of a spatula for initial mixing. Two other natural rubber gloves - depending on the silicone -, showed satisfactory results only when the initial mixing was performed with a spatula. It was concluded that setting inhibition depends on the kind of vinyl polysiloxane impression material and the kind of gloves used, but when the initial mixing was performed with the spatula this setting inhibition was overcome. The results of this study also showed that it is possible to associate cross-contamination control and satisfactory performance of addition silicone putty materials. When doubts arise from the compatibility between vinyl polysiloxane impression putties and gloves, the initial mixing should be performed with a spatula.A finalidade da presente pesquisa foi avaliar a influência na elasticidade da manipulação de silicones de adição em consistência de massa, por meio de várias técnicas, empregando-se luvas. A polimerização dos materiais foi avaliada por meio de um elasticímetro. Ensaiaram-se quatro silicones, empregando cinco marcas de luvas (uma de vinil, uma de borracha sintética e três de borracha natural). Dependendo do tipo de luva, ela foi lavada ou não e ainda foi utilizada ou não uma espátula para a mistura inicial dos silicones. Os resultados demonstraram que no emprego das luvas de vinil, uma das de borracha sintética e uma das de borracha natural não precisaram ser lavadas, nem a utilização de espátula para a mistura inicial foi necessária. Duas luvas de borracha natural não conduziram a resultados satisfatórios com todos os silicones sem que a mistura inicial fosse feita com a espátula mas, com essa prática, todas as luvas foram compatíveis com todos os silicones. Pode-se concluir que, em caso de dúvida sobre a compatibilidade entre tipo de luva e marca de silicone, o emprego de espátula na mistura inicial contorna o problema

The influence of dispersing additive on the paraffin crystallization in model systems

The work is dedicated to investigation of the influence of dispersing additive on the paraffin crystallization in model systems. A new method to determine the paraffin saturation point of transparent solutions based on the phenomenon of light scattering has been proposed. The linear relationship between the values of critical micelle concentrations of the additive and the quantity of paraffin in solution has been obtained. The influence of the model system composition on the paraffin crystallization has been studied

Probing the Enamel Topography After Acid Erosion by Scanning Electrochemical Microscopy

In this work, we present an investigation on the thickness of the eroded enamel layer in tooth samples after exposure to citric and hydrochloric acid by using Scanning Electrochemical Microscopy (SECM). Approaching curves with typical negative feedback behavior were obtained in enamel samples for evaluation of topographic changes. In a control experiment, SECM images showed no significant difference in the current monitored during the scan, implying that enamel demineralization did not occur in mineral water medium. Topographic SECM images obtained after contact with citric and hydrochloric acid for different periods of time showed a significant increase in the current relative to a previously protected surface, indicating the structural loss of enamel. The thickness of the enamel layer eroded after contact with hydrochloric acid was significantly higher when compared to the one obtained with citric acid. Hence, our results showed that the enamel acid erosion is a relatively fast process, which is strongly dependent on parameters such as pH, time, acid strength and acid concentration.FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)CNPq (Conselho Nacional de Desenvolvimento Cientifico e Tecnologico)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq

Prefabricated resin veneer: A case report of a simplified restorative technique

Background. The aim of this study was to describe the step-by-step procedures of clinical cases using prefabricated composite resin veneers (PCRVs), manufactured with the Brilliant New Generation composite resin (Coltene, Altstätten, Switzerland). Direct composite veneers presented some drawbacks such as the difficulty of execution and color instability of the composite resin over time. The simplified application of the PCRVs has been introduced as an interesting alternative in cases of smile asymmetry, large deficient restorations and discolored teeth. In the present investigation, the PCRV technique is described completely to help the dentist during the planning and execution of treatments with the Componeer system. Conclusion The treatment with Componeer Brilliant NG yielded excellent aesthetic results. PCRV technique is simpler than direct composite veneer technique. The specific characteristics of the system can promote the results with greater aesthetic longevity. It is important to highlight that this procedure does not replace the already established veneer technique with dental ceramics. Clinical implication. PCRVs yielded excellent surface gloss. Their dimensions, based on the golden ratio, facilitates the technique and is an excellent alternative in the aesthetic restorative treatment in the anterior region

Qualitative SEM/EDS analysis of microleakage and apical gap formation of adhesive root-filling materials

Objective: The aim of this study was to compare the correspondence between gap formation and apical microleakage in root canals filled with epoxy resin-based (AH Plus) combined or not with resinous primer or with a dimethacrylate-based root canal sealer (Epiphany). Material and Methods: Thirty-nine lower single-rooted human premolars were filled by the lateral condensation technique (LC) and immersed in a 50-wt% aqueous silver nitrate solution at 37 degrees C (24 h). After longitudinal sectioning, epoxy resin replicas were made from the tooth specimens. Both the replicas and the specimens were prepared for scanning electron microscopy (SEM). The gaps were observed in the replicas. Apical microleakage was detected in the specimens by SEM/energy dispersive spectroscopy (SEM/EDS). The data were analyzed statistically using an Ordinal Logistic Regression model and Analysis of Correspondence (alpha=0.05). Results: Epiphany presented more regions containing gaps between dentin and sealer (p<0.05). There was correspondence between the presence of gaps and microleakage (p<0.05). Microleakage was similar among the root-filling materials (p>0.05). Conclusions: The resinous primer did not improve the sealing ability of AH Plus sealer and the presence of gaps had an effect on apical microleakage for all materials.CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior)/Institutional Qualification Program (PQI) [0090/03-4]CAPES (Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior)/Institutional Qualification Program (PQI

Influence of etching time on bond strength in dentin irradiated with erbium lasers

The purpose of this in vitro study was to evaluate the effect of etching time on the tensile bond strength (TBS) of a conventional adhesive bonded to dentin previously irradiated with erbium:yttrium-aluminum-garnet (Er:YAG) and erbium, chromium:yttrium-scandium-gallium-garnet (Er,Cr:YSGG) lasers. Buccal and lingual surfaces of 45 third molars were flattened until the dentin was exposed and randomly assigned to three groups (n = 30) according to the dentin treatment: control (not irradiated), irradiated with Er:YAG (1 W; 250 mJ; 4 Hz; 80.6 J/cm(2)) laser or Er,Cr:YSGG (4 W; 200 mJ; 20 Hz; 71.4 J/cm(2)) laser, and into three subgroups (n = 10) according to acid etching time (15 s, 30 s or 60 s) for each experimental group. After acid etching, the adhesive was applied, followed by the construction of an inverted cone of composite resin. The samples were immersed in distilled water (37A degrees C for 24 h) and subjected to TBS test [50 kilogram-force (kgf), 0.5 mm/min]. Data were analyzed by analysis of variance (ANOVA) and Tukey statistical tests (P a parts per thousand currency signaEuro parts per thousand 0.05). Control group samples presented significant higher TBS values than those of all lased groups. Both irradiated groups exhibited similar TBS values. Samples subjected to the different etching times in each experimental group presented similar TBS. Based on the conditions of this in vitro study we concluded that Er:YAG and Er,Cr:YSGG laser irradiation of the dentin weakens the bond strength of the adhesive. Moreover, increased etching time is not able to modify the bonding strength of the adhesive to irradiated dentin.FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo)[97/10823-0]FAPESP (Fundacao de Amparo a Pesquisa do Estado de Sao Paulo)[CEPID/CEPOF 98/14270-8