RESUMEN
Using direct infusion electrospray ionization mass and tandem mass spectrometric experiments [ESI-MS(/MS)], we have performed on-line monitoring of some reactions used to form Tröger's bases. Key intermediates, either as cationic species or as protonated forms of neutral species, have been intercepted and characterized. The role of urotropine as the methylene source in these reactions has also been accessed. Reaction pathways shown by ESI-MS(/MS) have been probed by gas-phase ion/molecule reactions, and an expanded mechanism for Tröger's base formation based on the mass spectrometric data has been elaborated.
Asunto(s)
Compuestos de Anilina/química , Azocinas/química , Espectrometría de Masa por Ionización de Electrospray , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Compuestos de Anilina/síntesis química , Azocinas/metabolismo , Cromatografía Liquida , Formaldehído/química , Metenamina/química , Modelos Químicos , Modelos Moleculares , Estructura Molecular , Tromboxano-A Sintasa/antagonistas & inhibidoresRESUMEN
A birdcage coil capable of operating simultaneously and independently in three orthogonal dimensions has been developed. A co-rotational end-ring mode producing an RF field in the longitudinal direction was utilized in addition to the two common transverse orthogonal modes. Two conductor turns were used for each of the coil's windows, increasing its inductance by a factor of four, thereby, making the coil suitable for low-frequency applications. Two or three-frequency detection can be easily carried out with this device. Orthogonality of the coil's channels allows arbitrarily close frequency positioning of each resonant mode, potentially useful in wide-line NQR studies, in which simultaneous excitation/detection of signals from three adjacent regions of a single wide line can be performed. The coil's performance was evaluated using a three-dimensional scheme, in which a circularly polarized experiment was combined with a linearly polarized measurement at another frequency, resulting in SNR improvement by 55%.
Asunto(s)
Espectroscopía de Resonancia Magnética/instrumentación , Diseño de Equipo , Metenamina/química , Nitrito de Sodio/químicaRESUMEN
A simple Q-damper device for active probe recovery time reduction is introduced along with a straightforward technique for the circuit's component value optimization. The device is inductively coupled to a probe through a coupling transformer positioned away from the main coil, which makes the design independent of the coil type being used. The Q-damper is a tuned circuit, which is resonant at the same frequency as the probe and can be actively interrupted. When the circuit is interrupted, it is detuned and, thereby, is uncoupled from the probe, which operates normally. Turning the device on leads to re-coupling of the circuits and causes splitting of the probe's resonance line, which can be observed through its drive port. A resistance of an appropriate value is introduced into the Q-damper circuit, resulting in smoothing of the resonance splitting into one broad line, representing the coupled system's low-Q state, in which the energy stored in the main coil is efficiently dissipated. The circuit's component values are optimized by monitoring the shape of this low-Q state. Probe recovery time reduction by, approximately, an order of magnitude has been obtained with this device. Application of the device during an NQR experiment led to an increase in the signal-to-noise ratio by a factor of 4.9.
Asunto(s)
Imagen por Resonancia Magnética/instrumentación , Espectroscopía de Resonancia Magnética/instrumentación , Calibración , Diseño de Equipo , Matemática , Metenamina/química , Ondas de RadioRESUMEN
The effect of Er:YAG laser application and EDTAC on the adhesion of epoxy resin-based endodontic sealers to human dentin was evaluated in vitro. A total of 99 extracted human maxillary molars with their crowns worn flat were used. The teeth were divided into 3 groups: group 1, the dentin surface received no treatment; group 2, EDTAC was applied to the dentin surface for 5 min; group 3, the dentin surface received Er:YAG laser application (2.25 W potency; 11 mm focal distance; 4 Hz frequency; 200 mJ energy; 62 J total energy; 313 mean impulse). Three teeth from each group were analyzed by scanning electron microscopy for changes in dentin surface. The epoxy resin root canal sealers used were: AH Plus, Topseal, Sealer 26, AH 26, and Sealer Plus. The zinc oxide eugenol-based sealer Fillcanal was used as control. Adhesion was measured with a Universal testing machine. The results showed a statistically significant difference at the level of 1% among the dentin treatments. The dentin treated with Er:YAG laser showed greater adhesion with the sealers than dentin treated with EDTAC which was greater than dentin that received no treatment. The Tukey test showed the formation of 5 groups in decreasing order of adhesion: AH Plus, Topseal and Sealer 26, AH 26, Sealer Plus, and Fillcanal (Grossman cement).
Asunto(s)
Quelantes/uso terapéutico , Recubrimiento Dental Adhesivo , Dentina/ultraestructura , Ácido Edético/análogos & derivados , Ácido Edético/uso terapéutico , Resinas Epoxi/química , Terapia por Láser , Materiales de Obturación del Conducto Radicular/química , Adhesivos/química , Silicatos de Aluminio , Bismuto/química , Hidróxido de Calcio/química , Dentina/efectos de los fármacos , Dentina/efectos de la radiación , Combinación de Medicamentos , Erbio , Humanos , Metenamina/química , Microscopía Electrónica de Rastreo , Plata/química , Titanio/química , Itrio , Cemento de Óxido de Zinc-Eugenol/químicaRESUMEN
OBJECTIVE: The purpose of this study was to evaluate the release of formaldehyde by some root canal filling materials. STUDY DESIGN: Two older endodontic sealers, AH 26 and Endomethasone, and 2 recently available sealers, AH Plus and Top Seal, were analyzed. Infrared and electronic spectroscopy were used to determine formaldehyde content after set of the materials. RESULTS: Analysis showed that the AH 26 and Endomethasone sealers released formaldehyde. Although the AH Plus and Top Seal sealers have similar chemical composition, they released formaldehyde in a minimal concentration. CONCLUSIONS: The AH 26 and Endomethasone sealers released formaldehyde after setting; however, a minimum release was observed for the AH Plus and Top Seal sealers.
Asunto(s)
Administración Tópica , Fijadores/química , Formaldehído/química , Hidrocortisona , Materiales de Obturación del Conducto Radicular/química , Antiinflamatorios/análisis , Antiinflamatorios/química , Bismuto/análisis , Bismuto/química , Fenómenos Químicos , Química Física , Dexametasona/análisis , Dexametasona/química , Combinación de Medicamentos , Resinas Epoxi/análisis , Resinas Epoxi/química , Fijadores/análisis , Formaldehído/análisis , Humanos , Metenamina/análisis , Metenamina/química , Polímeros/análisis , Materiales de Obturación del Conducto Radicular/análisis , Plata/análisis , Plata/química , Espectrofotometría , Espectrofotometría Infrarroja , Espectrofotometría Ultravioleta , Timol/análogos & derivados , Timol/análisis , Timol/química , Titanio/análisis , Titanio/químicaRESUMEN
The aim of this study was to determine the in vitro antimicrobial effect of six endodontic sealers after 2, 20 and 40 days. The sealers studied were Apexit, Endion, AH26, AH-Plus. Procosol and Ketac Endo. The microorganisms used were Candida albicans, Staphylococcus aureus, Streptococcus mutans and Actinomyces israelii. Petri dishes were filled with sterile agar and 0.1-ml wells were prepared and filled with the sealers. The agar plates were stored for 24 h at 37 degrees C. The samples were then removed, immersed in 4.5 ml of culture medium and divided into three groups. The samples in group 1 were stored for 2 days at 37 degrees C whereas the samples of groups 2 and 3 were stored at 4 degrees C for 20 and 40 days respectively. The samples were then removed and discarded, and 0.1 ml of the culture medium was seeded on the agar plates in order to perform colony forming unit counts. Apexit, Endion and AH-Plus produced slight inhibition on Streptococcus mutans at 20 days and on Actinomyces israelii at every time interval. No effect was found on Candida albicans and Staphylococcus aureus. Ketac Endo only produced an antimicrobial effect on Actinomyces israelii at 2 and 40 days. AH26 and Procosol showed antimicrobial effect at 40 days on Candida albicans, at 20 and 40 days on Streptococcus mutans and Staphylococcus aureus, and an effective inhibition on Actinomyces israelii at every time interval. Statistical analysis revealed both sealers and microorganisms to be significant factors affecting results in groups 2 and 3. In conclusion, the sealers evaluated in this study showed different inhibitory effects depending on time span. Overall, sealers containing cugenol and formaldehyde proved to be most effective against the microorganisms at the time intervals studied.
Asunto(s)
Materiales de Obturación del Conducto Radicular/farmacología , Actinomyces/efectos de los fármacos , Análisis de Varianza , Bismuto/química , Bismuto/farmacología , Hidróxido de Calcio/química , Hidróxido de Calcio/farmacología , Candida albicans/efectos de los fármacos , Recuento de Colonia Microbiana , Combinación de Medicamentos , Resinas Epoxi/química , Resinas Epoxi/farmacología , Cementos de Ionómero Vítreo/química , Cementos de Ionómero Vítreo/farmacología , Concentración de Iones de Hidrógeno , Metenamina/química , Metenamina/farmacología , Pruebas de Sensibilidad Microbiana , Resinas Sintéticas/farmacología , Materiales de Obturación del Conducto Radicular/química , Plata/química , Plata/farmacología , Staphylococcus aureus/efectos de los fármacos , Streptococcus mutans/efectos de los fármacos , Titanio/química , Titanio/farmacología , Óxido de Zinc/farmacologíaRESUMEN
The disintegration of three endodontic cements in water was determined quantitatively and qualitatively. The materials studied were Ketac-Endo (KE), Tubli Seal (TS), and AH26 (AH). Specimens were immersed in water for 48 h (GI), 7 (GII) and 45 days (GIII). The solid residue was then determined. For the qualitative analysis three groups of tubes were filled with the materials and stored in water for the same periods. The exposed surface was photographed. Results expressed as percentage of original mass in the quantitative analysis for loss of mass due to dissolution were: GI = KE 2.39 (0.70); TS 3.56 (0.37); AH 4.94 (2.83); GII = KE 2.84 (0.30); TS 2.50 (0.50); AH 0.66 (0.26); GIII = KE 1.60 (0.84); TS 1.03 (0.42); AH 1.22 (0.54). Tukey's least significant difference (0.05) was 2.94. In the qualitative experiment KE disintegration was far more evident than that suffered by other materials. The quantitative results had no correlation with the qualitative observations probably due to the difference in the moment when the materials were immersed.