Linear dimensional stability of irreversible hydrocolloid materials over time

El objetivo de este estudio fue evaluar la estabilidad dimensional lineal de diferentes hidrocoloides irreversibles enfunción del tiempo. Se confeccionó una matriz metálica con sus correspondientes cubetas individuales realizadas con láminas termoplásticas (Sabilex, de 0.125 mm de espesor). Sele realizaron perforaciones para la retención del material. Se tomaron cinco impresiones con cada material a esta matriz, utilizando Kromopan 100 (LASCOD) [AlKr], que presentauna estabilidad dimensional de 100 horas, y Phase Plus (ZHERMACK) [AlPh], que tiene una estabilidad dimensional de 48 horas. Luego se tomaron fotografías estandarizadas adiferentes intervalos de tiempo (0, 15, 30, 45, 60, 120 minutos; 12, 24 y 96 horas), usando un dispositivo ad-hoc. Las imágenes se analizaron con software de procesamiento de imágenes(UTHSCSA Image Tool) realizando la medición de la distancia entre las intersecciones de surcos previamente realizados en la porción superior de la matriz. Los resultados obtenidos fueronanalizados mediante Análisis de Varianza para mediciones repetidas. Se detallan los datos iniciales y finales obtenidos (media y DS): AlKr: 16,44 (0,22) y 16,34 (0,11), AlPh: 16,40(0,06) y 16,18 (0,06). El análisis estadístico ha mostrado el efecto significativo para las variables material y tiempo. Bajo las condiciones de este estudio podemos concluir que tiempoafectaría significativamente la estabilidad dimensional lineal de los hidrocoloides irreversibles...

Influence of alginate impression materials and storage time on surface detail reproduction and dimensional accuracy of stone models / Influência dos alginatos e tempo de armazenamento na reprodução de detalhes da superfície e estabilidade dimensional de modelos de gesso

This study compared the surface detail reproduction and dimensional accuracy of stone models obtained from molds prepared using different alginate impression materials (Cavex Color Change, Hydrogum 5, or Jeltrate Plus) and with different storage times (1, 3, and 5 days) to models from molds that were filled immediatel y with no storage time. The molds were prepared over a matrix containing 50-μm line, (ISO 1563 standard) under pressure with a perforated metal tray. The molds were removed2 minutes after loss of sticky consistency and either filled immediately or stored in closed jars at 100% relative humidity and 37°C for 1, 3, or 5 days. The molds were filled with dental plaster (Durone IV). Surface detail reproduction and dimensional accuracy were evaluated using optical microscopy on the 50-μmwide line, which was 25 mm in length, according to ISO 1563 standard. The dimensional accuracy results (%) were subjected to analysis of variance. The 50-μm wide line (ISO 1563 standard)was completely reproduced by all alginate impression materials regardless of the storage time. There was no statistically significant difference in the mean dimensional accuracy values of stone models made from molds composed of different alginate impression materials and with different storage times (p = 0.989).In conclusion, storing the mold for five days prior to filling did not change the surface detail reproduction or dimensional accuracy of the alginates examined in this study.

Este estudo comparou a reprodução de detalhes da superfície e estabilidade dimensional de modelos de gesso obtidos a partir de diferentes alginatos (Cavex Color Change, Hydrogum 5, Jeltrate Plus) e com diferentes tempos de armazenagem (1, 3, e 5 dias)para modelos obtidos de moldes que foram preenchidos imediatamente sem tempo de armazenagem. Os moldes foram preparados sobre matriz contendo linha de 50 μm (norma ISO1563) realizado sob pressão com moldeira de metal perfurada.Os moldes foram removidos 2 minutos após a perda de consistência pegajosa e preenchidos imediatamente ou armazenado sem frascos fechados com temperatura (37°C) e umidade relativa(100%) controladas por 1, 3 ou 5 dias. Os moldes foram preenchidos com gesso dental (Durone IV). A reprodução de detalhes da superfície e a estabilidade dimensional foram avaliadas usando microscopia óptica na linha 50 μm com 25 mm de comprimento, de acordo com a norma ISO 1563. Os resultados de estabilidade dimensional (%) foram submetidos á análise de variância. A linha de 50 μm (norma ISO 1563) foi completamente reproduzida por todos os alginatos, independentemente do tempo de armazenagem. Não houve diferença estatisticamente significa -tiva nos valores médios de estabilidade de modelos de gesso obtidos de moldes de diferentes alginatos com diferentes tempos de armazenagem (p = 0.989). Em conclusão, o armazenamento do molde durante cinco dias antes do preenchimento não alterou a reprodução de detalhes da superfície ou estabilidade dimensional dos alginatos examinadas neste estudo.

Influence of delayed pouring on irreversible hydrocolloid properties

The aim of this study was to evaluate the physical properties of irreversible hydrocolloid materials poured immediately and after different storage periods. Four alginates were tested: Color Change (Cavex); Hydrogum (Zhermack); Hydrogum 5 (Zhermack); and Hydro Print Premium (Coltene). Their physical properties, including the recovery from deformation (n = 3), compressive strength (n = 3), and detail reproduction and gypsum compatibility (n = 3), were analyzed according to ANSI/ADA specification no. 18. Specimens were stored at 23ºC and humidity and were then poured with gypsum immediately and after 1, 2, 3, 4, and 5 days. The data were analyzed by two-way analysis of variance (ANOVA) and Tukey's test at p < 0.05. All of the alginate impression materials tested exhibited detail reproduction and gypsum compatibility at all times. Hydro Print Premium and Hydrogum 5 showed recovery from deformation, as established by ANSI/ADA specification no. 18, after 5 days of storage. As the storage time increased, the compressive strength values also increased. Considering the properties of compounds' recovery from deformation, compressive strength, and detail reproduction and gypsum compatibility, irreversible hydrocolloids should be poured immediately.

Single step approach to make diagnostic impressions of both the arches and face bow transfer: A novel technique.

Context: Mounting the maxillary and mandibular dentulous casts for Diagnostic purpose requires many steps (including making maxillary and mandibular impressions, face-bow transfer, and bite registration) or many appointments. A simple new technique of doing all of this together without compromising on the accuracy can save time over the conventional mounting procedure. Aim: To compare the accuracy of a new technique of a single-step diagnostic mounting procedure with that of the conventional diagnostic mounting procedure. Materials and Methods: Ten dentulous patients with the full complement of teeth and without any history of temporomandibular disorder and orthodontic treatment were selected for this study. A detachable metal triple tray to replace the fork part of the face bow fork that further could be attached to face bow was fabricated. Dual-arch impressions and face-bow transfer were made in these subjects using this modified triple tray. These mountings were compared with the ones done with the conventional mounting procedure. Five linear measurements (using stable reference points on the articulator and the cast) were made and the values obtained by both the methods were compared. Statistical Analysis: The Student's 't' test for statistical analysis was used in this study. Results: The measurement values obtained by the single-step method were almost similar to the ones obtained by the conventional method. The various mean measurements for the single step and conventional methods were 37.7 ± 6.8 and 38.5 ± 6.5 mm; 70.0 ± 4.4 and 70.1 ± 4.2 mm; 57.0 ± 4.9 and 57.3 ± 4.2 mm; 71.3 ± 4.5 and 71.0 ± 4.6 mm; and 58.7 ± 2.5 and 58.3 ± 2.3 mm; respectively. The differences between the values obtained by the conventional and single-step methods were not statistically significant. Conclusion: The single-step procedure of diagnostic mounting can be used as an alternative to the conventional method, without compromising the quality of mounting.

Surface detail reproduction and dimensional accuracy of stone models: influence of disinfectant solutions and alginate impression materials

This study compared the surface detail reproduction and dimensional accuracy of stone models obtained from molds disinfected with 2% sodium hypochlorite, 2% chlorhexidine digluconate or 0.2% peracetic acid to models produced using molds which were not disinfected, with 3 alginate materials (Cavex ColorChange, Hydrogum 5 and Jeltrate Plus). The molds were prepared over matrix containing 20-, 50-, and 75-µm lines, performed under pressure with perforated metal tray. The molds were removed following gelation and either disinfected (using one of the solutions by spraying followed by storage in closed jars for 15 min) or not disinfected. The samples were divided into 12 groups (n=5). Molds were filled with dental gypsum Durone IV and 1 h after the start of the stone mixing the models were separated from the tray. Surface detail reproduction and dimensional accuracy were evaluated using optical microscopy on the 50-µm line with 25 mm in length, in accordance with the ISO 1563 standard. The dimensional accuracy results (%) were subjected to ANOVA. The 50 µm-line was completely reproduced by all alginate impression materials regardless of the disinfection procedure. There was no statistically significant difference in the mean values of dimensional accuracy in combinations between disinfectant procedure and alginate impression material (p=0.2130) or for independent factors. The disinfectant solutions and alginate materials used in this study are no factors of choice regarding the surface detail reproduction and dimensional accuracy of stone models.

Este estudo comparou a reprodução de detalhes da superfície e alteração dimensional de modelos de gesso obtidos a partir de moldes desinfetados com hipoclorito de sódio 2%, digluconato de clorexidina 2%, ou ácido peracético 0,2% a modelos confeccionados utilizando moldes que não foram desinfetados com três alginatos (Cavex ColorChange, Hydrogum 5, Jeltrate Plus). Os moldes foram preparados sobre matriz contendo linhas de 20, 50 e 75 µm realizado sob pressão com moldeira de metal perfurada. Os moldes foram removidos após a geleificação e desinfetados (utilizando uma das soluções por pulverização, armazenados em frascos fechados durante 15 min) ou não desinfetados. Assim, as amostras foram divididas em 12 grupos (n=5). Os moldes foram preenchidos com gesso dental Durone IV e uma hora após a manipulação do gesso os modelos foram separados da moldeira. A reprodução de detalhes da superfície e a precisão dimensional foram avaliadas usando microscopia óptica na linha 50 µm com 25 mm de comprimento, de acordo com a norma ISO 1563. Os resultados de precisão dimensional (%) foram submetidos à ANOVA. A linha de 50 µm foi completamente reproduzida por todos os alginatos, independentemente do processo de desinfecção. Não houve diferença estatisticamente significativa nos valores médios de precisão dimensional nas combinações entre procedimento de desinfecção e alginato (p=0,2130), ou para fatores independentes. Soluções desinfetantes e alginatos utilizados neste estudo não são fatores de escolha em relação à reprodução de detalhes da superfície e alteração dimensional de modelos de gesso.

Efficacy of various spray disinfectants on irreversible hydrocolloid impression materials: An in vitro study.

Background: Most of the materials (casts, impressions, etc.) that are sent to the dental laboratories show the presence of numerous pathogenic microorganisms. All the spray disinfectants are not equally effective against these microorganisms. Aims and Objectives: The aim was to compare the effectiveness of different spray disinfectants on irreversible hydrocolloid impressions and to find out the most effective dilution, contact time, and effect against each microorganism studied. Materials and Methods: The effects of four spray disinfectants, 5.25% sodium hypochlorite, 0.525% sodium hypochlorite, 1:213 (1 part in 213 parts of water) povidone iodine, and 2% glutaraldehyde along with control (distilled water) on irreversible hydrocolloid impressions contaminated with Staphylococcus aureus, Bacillus subtilis and Streptococcus viridans were studied. Results: Sodium hypochlorite, 5.25%, showed 1-min exposure time which was able to effect a 4log10 reduction in bacterial counts against S. aureus and S. viridans followed by 0.525% sodium hypochlorite and 2% glutaraldehyde for 10 min. None were able to effect a 4 log10 reduction against B. subtilis. Conclusion: Sodium hypochlorite with a concentration of 5.25% was the most effective disinfectant and required the shortest contact time (1 min). Not all ADA-approved concentrations of surface disinfectants work equally well on irreversible hydrocolloid impression materials.

Ion-specific thermodynamical properties of aqueous proteins

Ion-specific interactions between two colloidal particles are calculated using a modified Poisson-Boltzmann (PB)equationandMonteCarlo(MC)simulations. PBequationspresentgoodresultsofionicconcentration profiles around a macroion, especially for salt solutions containing monovalent ions. These equations include not only electrostatic interactions, but also dispersion potentials originated from polarizabilities of ions and proteins. This enables us to predict ion-specific properties of colloidal systems. We compared results obtained from the modified PB equation with those from MC simulations and integral equations. Phase diagrams and osmotic second virial coefficients are also presented for different salt solutions at different pH and ionic strengths, in agreement with the experimental results observed Hofmeister effects. In order to include the water structure and hydration effect, we have used an effective interaction obtained from molecular dynamics of each ion and a hydrophobic surface combined with PB equation. The method has been proved to be efficient and suitable for describing phenomena where the water structure close to the interface plays an essential role. Important thermodynamic properties related to protein aggregation, essential in biotechnology and pharmaceutical industries, can be obtained from the method shown here.

Interações íon-específicas (dependentes do tipo de íon presente em solução) entre duas partículas coloidais são calculadas usando a equação de Poisson-Boltzmann (PB) modificada e simulações de Monte Carlo (MC). As equações de PB apresentam bons resultados de perfis de concentração nas proximidades de um macro-íon, principalmente para soluções salinas contendo íons monovalentes. Estas equações incluem não só interações eletrostáticas, mas também potenciais de dispersão, que têm origem nas polarizabilidades de íons e proteínas, permitindo a predição de propriedades íon-específicas de sistemas coloidais. Os resultados obtidos a partir da equação de PB modificada são comparados com outros obtidos por simulação de MC e por equações integrais. Diagramas de fase e o segundo coeficiente de virial são obtidos para diferentes sais e diferentes valores de pH e força iônica, em concordância com efeitos de Hofmeister observados experimentalmente. Interações efetivas obtidas por dinâmica molecular entre cada íon e uma superfície hidrofóbica foram incluídas na equação de PB, a fim de considerar a estrutura da água e efeitos de hidratação. O método mostrou-se eficiente e adequado para descrever fenômenos onde a estrutura da água nas proximidades da interface desempenha papel essencial. Propriedades termodinâmicas importantes, relacionadas com a agregação de proteínas, essenciais em biotecnologia e indústrias farmacêuticas, podem ser obtidas pelo método aqui apresentado.

Análisis de las técnicas de impresión en prótesis parcial removible a extensión distal / Analysis of the impression technique in distal extension removable partial denture

El procedimiento de impresión es una etapa importante en la elaboración de la prótesis parcial removible al reproducir la anatomía dentaria, los rebordes alveolares residuales y las estructuras adyacentes. La impresión funcional se indica para los casos dentomucosoportados para hacer compatible las diferencias en el comportamiento de los dientes pilares y la mucosa del reborde bajo cargas funcionales. Existen distintas técnicas de impresiones funcionales y todas ellas influyen distintamente en el desplazamiento de los tejidos que recubren al reborde y en el comportamiento de las bases protésicas. La técnica de modelo alterado es uno de los procedimientos de impresión más utilizados debido a los resultados que se obtienen, sin embargo, recientemente se ha demostrado efectos similares con otras técnicas.

The impression procedure is an important step in achieving sucess in removable partial denture. The functional impression is used for tooth-mucosa supported removable partial denture and it´s an attempt to accommodate the difference in resiliency between hard and soft tissue support. There are many techniques and all of them displace residual ridge mucosa in different ways. The altered cast impression fulfills the requirements of functional impression, however, other techniques have demonstrated the same effects.

Effect of some anions on the mobility of amino acids in soils by thin layer chromatography.

The mobility rate of some cyclic and aliphatic amino acids in terms of Rf values by using soil-thin layer chromatography shows the following order: glutamic acid > histidine > valine > leucine > serine > alanine. After conducting the studies to determine the effect of some anions, viz. MoO4(2-), B4O7(2-), C2O4(2-),CO3(2-), HCO3- and H2PO4- on the mobility of those amino acids, the mobility of the amino acids was found to increase with the increasing concentration of these anions up to a certain limit and thereafter the mobility rate declined except in case of glutamic acid which shows a fall in its movement throughout the entire range of their application in all cases. The results have been explained on the basis of a reaction mechanism involved in the interaction of these anionic species with soil colloids and amino acids in soil solution.

Clinical evaluation of interocclusal recording materials in bilateral free end cases

Cinco combinações de materiais comumente utilizados para registros intermaxilares em casos de extremidades livres bilaterais foram avaliados: base de resina acrílica + cera; base de resina acrílica + pasta zincoenólica; base de resina acrílica + cera + resina Duralay; silicona de condensação; e placa de resina acrílica + hidrocolóide irreversível. Foi realizada a medida da distância vertical entre pontos referenciais em 6 regiões nas bases dos modelos articulados. As medidas obtidas com a articulação manual dos modelos foram tomadas como padrão de comparação para as medidas obtidas com os materiais testados. Os resultados foram submetidos à análise estatística por meio de análise de variância e teste de Tukey. Houve diferença estatisticamente significante (p<0.05) entre a silicona de condensação e a combinação da base de resina acrílica + cera, porém entre os demais materiais não houve diferença estatisticamente significante. A silicona de condensação apresentou as maiores diferenças em relação às medidas obtidas pela articulação manual dos modelos e a combinação da base de resina acrílica + cera apresentou as menores diferenças. Com base nos achados deste estudo, a seguinte escala de reprodutibilidade pode ser estabelecida, do melhor para o pior: base de resina acrílica + cera; placa de resina acrílica + hidrocolóide irreversível; base de resina acrílica + cera + pasta zincoenólica; base de resina acrílica + cera + resina Duralay; e silicona de condensação.

Characterization and identification of chitinase producing Streptomyces venezuelae P10.

In an attempt to isolate chitinase producers from soil, a streptomycete strain was found potent using natural chitin as the substrate. Chitinolytic activity was tested directly on agar plates, also with crude enzyme. Chitinase assay showed that the isolate could produce 0.8 U/ml of the enzyme. The morphological, cultural, physiological and biochemical characters of the isolate P10 were studied, and identified as Streptomyces venezuelae P10.

Prótesis completa: impresiones (trans) / Complete dentures: impressions

La toma de impresiones al paciente totalmente desdentado tiene como objetivo registrar la anatomía de la cavidad bucal para reproducirla en escayola, y poder confeccionar las prótesis a su medida. Exponemos en este artículo los criterios recomendados para conseguir unas buenas impresiones. Aportamos pequeñas sugerencias que pueden facilitar al profesional la adquisición de la destreza necesaria para obtener unas impresiones correctas

The crystalloid vs colloid controversy in the era os hypertonic/hyperoncotic resuscitations: is the debate over?

The crystalloid vs. colloid controversy has been further complicated by the inclusion of hypertonic levels of sodium chloride (HTS) in both types of regimens. In this paper the recent literature on the controversy is reviewed. Colloids raise the intravascular colloid osmotic pressure and increase the fluid retention in the vessels. Crystalloids however, distribute into the interstitial and intravascular spaces at a ratio of approximately 3 to 1. It is therefore necessary to infuse a large volume of crystalloids in order to complete resuscitation. The advantage of colloids over isotonic crystalloids focuses primarily on the incidence of pulmonary edema. In an analysis of clinical trials, however, colloids were not proven to be superior to crystalloids. The use of HTS decreases the amount of crystalloid required for resuscitation. Pulmonary and systemic vasodilation, an increase in cardiac output and stroke volume, decreased intracranial pressure and an enhanced immunologic response have been noted experimentally, and the clinical evidence seems to corroborate these findings. HTS with dextran (HSD) has been used in an attempt to combine the rapid cellular fluid shift of hypertonicity with the vascular fluid shift of colloids. The experimental evidence is compelling. Whereas HTS has proven itself to be a superior resuscitation regimen, HSD has not yet warranted in a clinical setting the optimism which its experimental studies seem to indicate.