Projection spectrograph as a tool for light polarization classrooms demonstrations

This article describes the use of a projection spectrograph based on an overhead projector for use in classroom demonstrations on light polarization and optical activity. A simple adaptation on a previously developed apparatus allows illustrating several aspects of optical activity, such as circular and linear birefringence, including their wavelength dependence. Specifically, we use the projection spectrograph to demonstrate the optical activity of an aqueous solution of sugar (circular birefringence), of a quartz plate and of an overhead projector transparence film (linear birefringence). A historical survey about the optical activity discovery and the main principles involved is also presented

Effects of adding lauryl-diethylene-glycol-ether sodium sulfate on sodium hypochlorite\'s physical-chemical properties, before and after bovine pulp tissue dissolution: an in vitro analysis.

Estudou-se, in vitro, a dissolução do tecido pulpar bovino, promovida pela solução de hipoclorito de sódio nas concentrações de 0,5; 1,0; 2,5 e 5,0 por cento com e sem lauril dietilenoglicol éter sulfato de sódio analisando-se, também, o potencial hidrogeniônico (pH), a tensão superficial, a condutividade iônica e o teor de cloro, antes e depois da utilização dessas soluções. Secionava-se um fragmento da porção central da polpa de incisivos centrais inferiores de bovinos e sua massa era anotada. Para a realização do teste de dissolução, confeccionou-se um dispositivo conectado a uma bomba peristáltica que promovia a agitação da solução. Colocava-se um fragmento pulpar no interior desse dispositivo e ligava-se a bomba peristáltica. O tempo de dissolução total foi medido com um cronômetro. Usando o tempo de dissolução do fragmento de polpa e a massa deste, calculava-se a velocidade de dissolução do tecido pulpar. Concluiu-se que: a) a velocidade de dissolução dos fragmentos de polpa bovina é diretamente proporcional à concentração da solução de hipoclorito de sódio e maior sem tensoativo; b) a redução do pH, entre o início e o final do processo de dissolução pulpar, é inversamente proporcional à concentração da solução de hipoclorito de sódio, com ou sem tensoativo; c) a redução da condutividade iônica, entre o início e o final do processo de dissolução pulpar, ocorreu da mesma forma nas diferentes concentrações da solução de hipoclorito de sódio, com ou sem tensoativo; d) a variação da tensão superficial, entre o início e o final do processo de dissolução pulpar, é diretamente proporcional à concentração da solução de hipoclorito de sódio e maior nas soluções sem tensoativo. As soluções sem tensoativo apresentaram redução da tensão superficial e as com tensoativo, elevação; e) os menores teores de cloro remanescente ocorreram com a solução de hipoclorito de sódio a 0,5 por cento e, os maiores, com o grupo formado pelas soluções a 1,0 - 2,5 e 5,0 por cento; e f) as soluções de hipoclorito de sódio com tensoativo apresentaram os menores teores de cloro remanescente após o processo de dissolução.The dissolution of bovine pulp tissue by 0.5, 1.0, 2.5 and 5% sodium hypochlorite with and without lauryl-diethylene-glycol-ether sodium sulfate was studied, in vitro. The pH, surface tension, ionic conductivity and chlorine level were also analyzed before and after use of these solutions. A fragment from the central portion of bovine mandibular central incisors was sectioned and its mass was recorded. The pulp fragment was placed in a hydraulic apparatus with a peristaltic pump for agitation of the solution. The time for total dissolution of the pulp segment was recorded with a chronometer. Using the pulp mass and the dissolution time, the velocity of pulp dissolution was calculated. It is concluded that: a) the velocity of dissolution of the bovine pulp fragments is directly proportional to the concentration of the sodium hypochlorite solution and is greater without the surfactant; b) the decrease in pH, from the beginning to the end of pulp dissolution, is inversely proportional to the concentration of the sodium hypochlorite solution and is greater with or without the surfactant; c) the decrease in ionic conductivity, from the beginning to the end of pulp dissolution, is similar with the different concentrations of the sodium hypochlorite solution, with and without the surfactant; d) the variation of surface tension, from the beginning to the end of pulp dissolution, is directly proportional to the concentration of the sodium hypochlorite solution and is greater in the solutions without surfactant. Solutions without surfactant presented a decrease in surface tension and those with surfactant an increase; e) the smallest levels of residual chlorine occurred with the 0.5% sodium hypochlorite solution, and the greatest with the group formed by 1.0, 2.5 and 5.0% sodium hypochlorite solutions; f) the sodium hypochlorite solutions with surfactant presented the lowest levels of residual chlorine after the dissolution process

Chemical analysis of chlorhexidine mixed or not with calcium hydroxide

O sucesso da terapia endodôntica depende da limpeza, anti-sepsia, escultura e obturação hermética dos canais radiculares, no entanto, o preparo biomecânico não gera redução microbiana suficiente na totalidade dos casos. Devido à inconfiabilidade inerente ao tratamento, parte dos casos ainda resulta em insucesso. As pastas de hidróxido de cálcio vêm sendo empregadas com a finalidade de ampliar a eficiência anti-séptica do tratamento dos canais radiculares além de estimular a recuperação dos tecidos afetados pela infecção endodôntica. O digluconato de clorexidina tem sido empregado na endodontia devido ao amplo espectro de ação principalmente contra \"Enterococcus faecalis\" e \"Candida albicans\" e vem sendo adicionado às pastas de hidróxido de cálcio uma vez que as virtudes de um complementam as deficiências do outro. No entanto, devido à estrutura molecular da clorexidina e aos níveis elevados de pH promovidos pelo hidróxido de cálcio, há indícios de risco sistêmico na sua utilização por causa da provável decomposição da clorexidina em radicais livres e para-cloroanilina que está classificada como possível agente carcinogênico em humanos pela IARC. O presente estudo teve como objetivo investigar quimicamente, por meio da Espectrometria de Massas (ESI-TOF-MS) e Cromatografia Líquida (HPLC), a solução de digluconato de clorexidina a 0,2% isolada ou misturada ao hidróxido de cálcio. As análises foram realizadas logo em seguida ao preparo das amostras e após os períodos de 7 e 14 dias de armazenamento à temperatura de 36,5 ºC. Constatou-se que a solução de digluconato de clorexidina isolada foi decomposta em diferentes subprodutos, inclusive em para-cloroanilina oferecendo riscos sistêmicos. Em contato com o hidróxido de cálcio, a decomposição da clorexidina é total com formação de diferentes compostos. Apesar de não ter sido demonstrada a presença de para-cloroanilina na pasta medicamentosa, o elevado número de espécies reativas possui alto potencial de dano sobre o material genético das células do paciente afetadas pela medicação intracanal. É imperativo estabelecer vínculos diagnóstico-terapêuticos precisos por meio do desenvolvimento de protocolos clínicos que restrinjam o uso dessas medicações intracanais a quadros clínicos com infecção endodôntica disseminada e periodontites apicais persistentes. É necessário desenvolver estratégias mais eficientes que utilizem processos biomecânicos de maior eficácia e medicações intracanais efetivas que não ofereçam riscos locais e sistêmicos para que se contemplem os objetivos do tratamento dos canais radiculares com previsibilidade e segurança.The success of endodontic therapy depends upon root canal cleanliness, antisepsis, sculpture, and hermetic obturation. However, biomechanical preparation does not always provide an adequate microbial reduction. Due to the inherent unreliability of the treatment, some cases still are unsuccessful. Calcium hydroxide pastes have been used with the aim to improve antisepsis effectiveness in root canal treatments, in addition to stimulating the recovery of tissues affected by endodontic infection. Chlorhexidine digluconate has been used in endodontics due to its broad action spectrum, mainly against \"Enterococcus faecalis\" and \"Candida albicans\", and has been added to calcium hydroxide pastes so that the advantages of one would compensate for the other\'s deficiencies. However, the structure of the chlorhexidine molecule in addition to the high pH values promoted by calcium hydroxide pose a systemic risk in its use due to the likely decomposition of chlorhexidine into free radicals and para-chloroaniline, which International Agency for Research on Cancer (IARC) has classified as a possible carcinogenic agents in humans. The purpose of the present study was to perform a chemical analysis of chlorhexidine digluconate at 0.2%, isolated or mixed to calcium hydroxide, using Mass Spectrometry and High- Efficiency Liquid Chromatography. The analyses were performed shortly after the samples were prepared, and after 7 and 14 days of storage at 36.5 ºC. It was found that the isolated chlorhexidine digluconate solution formed different byproducts, including para-chloroaniline, posing systemic risks. In contact with calcium hydroxide, chlorhexidine decomposes completely and forms different compounds. Though the study did not demonstrate the presence of para-chloroaniline in the medication paste, the high number of reactive species poses a high risk over the genetic material of the host cells affected by intracanal medication. It is mandatory to establish a precise diagnostic-therapeutic relation by developing clinical protocols that would restrict the use of these intracanal medications to clinical conditions with disseminated endodontic infection and persistent apical periodontitis. There is a need for more efficient strategies that use more effective biomechanical processes and intracanal medications that do not offer any local or systemic risk so root canal treatment goals can be considered with predictability and safety

In vitro evaluation of the thermal alterations on the root surface during preparation with different Ni-Ti rotary instruments

The present study evaluated, in vitro, the temperature alterations on the external root surface during instrumentation with four different rotary systems. A total of 20 extracted human maxillary lateral incisors were instrumented using either the ProFile, MicroMega, Quantec or K³ systems and the thermal alterations on the root surface were recorded by means of three thermocouples attached to the coronal, middle and apical portions of the root. Mean temperature increases no higher than 0.4ºC ± 1.0ºC (ProFile system) were recorded, which indicates that these instruments are safe for the surrounding periodontal tissues

Determination of para-Chloroaniline and Reactive Oxygen Species in Chlorhexidine and Chlorhexidine Associated with Calcium Hydroxide

The aim of this study was to determine whether para-chloroaniline (PCA) and/or reactive oxygen species (ROS) are generated by chlorhexidine (CHX) alone or after CHX is mixed with calcium hydroxide at different time points. Mass spectrometry was performed to detect PCA in samples of 0.2% CHX and Ca(OH)2 mixed with 0.2% CHX. High-performance liquid chromatography was used to confirm the presence of CHX in the mixture with Ca(OH)2. The samples were analyzed immediately after mixing and after 7 and 14 days. During the intervals of the experiment, the samples were maintained at 36.5 degrees C and 95% relative humidity. PCA was detected in the 0.2% CHX solution after 14 days. The mixture of CHX with Ca(CH)2 liberated ROS at all time points, but no traces of CHX were present in the mixture as a result of immediate degradation of the CHX. (J Endod 2008;34:1508-1514