Examinando por Autor "Neira, Miguel"

Mostrando 1 - 3 de 3
  • Miniatura
    Ítem
    Caries-free subjects have high levels of urease and arginine deiminase activity
    (Faculdade De Odontologia De Bauru - USP, 2014) Reyes, Evelyn; Martin, Javier; Moncada, Gustavo; Neira, Miguel; Palma, Patricia; Gordan, Valeria; Oyarzo, Juan Fernando; Yévenes, Ismael
    Objectives: This study investigated the relationship between urease and arginine deiminase system (ADS) activities and dental caries through a cross-sectional study. Material and Methods: Urease and ADS activities were measured in saliva and plaque samples from 10 caries-free subjects and 13 caries-active. Urease activity was obtained from the ammonia produced by incubation of plaque and saliva samples in urea. ADS activity was obtained from the ammonia generated by the arginine-HCl and Tris-maleate buffer. Specific activity was defined as micromoles of ammonia per minute per milligram of protein. Shapiro-Wilk statistical test was used to analyze the distribution of the data, and Mann-Whitney test was used to determine the significance of the data. Results: The specific urease activity in saliva and plaque was significantly higher in individuals with low DMFT scores. ADS activity in saliva (6.050 vs 1.350, p=0.0154) and plaque (8.830 vs 1.210, p=0.025) was also higher in individuals with low DMFT scores. Conclusions: Caries-free subjects had a higher ammonia generation activity by urease and arginine deiminase system for both saliva and plaque samples than low caries-active subjects. High levels of alkali production in oral environment were related to caries-free subjects.
  • Miniatura
    Ítem
    Efecto del ultrasonido endodóntico sobre clorhexidina al 2% en la formación de paracloroanilina. Estudio in vitro
    (Sociedad de Periodoncia de Chile. Sociedad de Implantología Oral de Chile. Sociedad de Prótesis y Rehabilitación Oral de Chile, 2015) Onetto, Daniela; Correa, Verónica; Araya, Pilar; Yévenes, Ismael; Neira, Miguel
    Resumen Introducción: La clorhexidina (CHX) en solución acuosa se hidroliza generando paracloroanilina (PCA), proceso acelerado por el aumento de temperatura y pH. El uso de ultrasonido endodóntico (USE), basado en fenómenos de oscilación, cavitación, microcorriente acústica, genera calor afectando la CHX. Objetivo: Identificar y cuantificar in vitro cambios fisicoquímicos, temperatura y pH, y la cantidad de PCA formada con el uso de ultrasonido endodóntico sobre soluciones de CHX al 2%. Materiales y métodos: La CHX 2% se activó durante 30, 60, 90 y 120 seg con USE a 24.500 Hz, midiendo antes y después de activación: pH, temperatura y cantidad de PCA, leyendo a 375 nm en curva de calibración de estándares de PCA y formación, registrando el espectro de absorción mediante espectrofotómetro UV-visible. Resultados: El USE aumentó la temperatura en 1 ◦C independiente del tiempo de aplicación y acidificó la solución de CHX 2%, sin variaciones significativas en pH y temperatura. No se observó coloración ni formación de precipitado en muestras activadas por USE a los diferentes tiempos. Las muestras no presentaron valores medibles de PCA a 375 nm. Los espectros de absorción de CHX 2% y activadas por USE por más de 60 seg presentaron curvas espectrales, peaks y valores de absorbancia diferentes.
  • Miniatura
    Ítem
    Water and Physiological Saline to Prevent the Formation of P-Chloroaniline
    (Universidad de La Frontera. Facultad de Medicina, 2015) Riquelme, María José; Correa, Verónica; Araya, Pilar; Neira, Miguel; Yévenes, Ismael
    ABSTRACT: This study determined if p-chloroaniline (PCA) can be minimized by using distilled water and physiological saline solution following sodium hypochlorite but before chlorhexidine. Hypochlorite 5%, 0.5%, 0.05%, 0.005% and 0.0005% dissolved in 0.9% NaCl and in distilled water were mixed with 2% chlorhexidine for the formation of PCA. The PCA was determined using UV-VISIBLE spectrometry, with spectral curve was determined the wavelength of maximum absorption of PCA. Formed PCA absorbance was measured between 0.025%, 0.02%, 0.015%, 0.01%, 0.005% and 0.0025% hypochlorite and 2% chlorhexidine. 2% chlorhexidine and hypochlorite with physiological saline form a white precipitate which prevents the measurement of PCA. Colored PCA is formed with 0.05%, 0.005% hypochlorite aqueous dilutions and 2% chlorhexidine. The lwavelength of maximum absorption obtained was 470 nm and absorbance of PCA showed a linear decrease. 0.005% NaClO produces the least amount of PCA. The best solvent to prevent the formation of PCA during the interaction of sodium hypochlorite with chlorhexidine is distilled water.