Fuentes de luz de uso clínico en el pre grado: 7 años de seguimento / Light curing units in the undergraduate dental clinics: 7 years of follow-up

RESUMEN Objetivo: Realizar, durante siete años ininterrumpidos, un control y seguimiento de las fuentes de luz disponibles en las clínicas odontológicas de pre graado de una Institución de Enseñanza Superior Pública Brasileña. Material y métodos: Durante el período comprendido entre 2011-2017 se evaluó el control de calidad de las fuentes de luz de la Facultad de Odontología de la Universidad Federal de Goiás a través del análisis de su estado de conservación y de su densidad de potencia (mW/cm2). Los datos obtenidos se sometieron a un análisis estadístico descritpivo y a las pruebas de Levene, Shapiro-Wilk, Kruskal-Wallis, Dunn y Chi-cuadrado (P<0,05). Resultados: No se observaron diferencias estadísticas significativas del estado de conservación de las fuentes de luz entre los años 2012, 2016 y 2017 (p>0,05). Sí se observaron diferencias estadísticas significativas entre los valores de densidad de potência entre dichos años (p<0,0001). En las comparaciones por pares, los valores de densidad de potencia para los años 2011 (p<0,01) y 2012 (p<0,05) fueron estadísticamente diferentes de los años 2015, 2016 y 2017. Conclusiones: Comparativamente se observó una mejora sustancial del estado de conservación de las fuentes de luz en los cuatro años iniciales de evaluaciones, con una disminución en el quinto año y una estabilización en los dos últimos años. Durante los siete años de estudio de la densidad de potencia de las fuentes de luz se observó en un aumento gradual de la misma con una estabilización de los resultados a partir del quinto año de control de calidad.

SUMMARY Objetive: To monitor the light curing units available at undergraduate dental clinics of a Brazilian Public Higher Education Institution for seven uninterrupted years. Materials and methods: In the period between 2011-2017, the quality control of light curing units at the Faculty of Dentistry, Federal University of Goiás, was evaluated by analyzing their state of conservation and power density (mW/cm2). Data obtained were subjected to descriptive statistical analysis and Levene, Shapiro-Wilk, Kruskal-Wallis, Dunn and Chi-square tests (P <0.05). Results: Regarding the conservation status of the light curing units, comparatively, there was no statistically significant difference between the years 2012, 2016 and 2017 (p> 0.05). Statistically significant differences were found for power density values between years (p <0.0001). In pairwise comparisons, the power density values for the years 2011 (p <0.01) and 2012 (p <0.05) were statistically different from the years 2015, 2016 and 2017. Conclusions: A significant improvement in the state of conservation of light curing units was observed in the initial four years of evaluations, with a decline in the fifth year and stabilization in the last two years. Regarding the power density of the light curing units, a gradual increase was observed in the seven years of study, with stabilization of the results after the fifth year of quality control.

Influence of pulse-delay curing on sorption and solubility of a composite resin.

The purpose of this study was to evaluate the sorption and solubility of a composite resin (TPH(3); Dentsply) cured with halogen light due to different storage media and curing modes. The methodology was based on the ISO 4049 standard. Two independent groups were established according to the storage time (7 days-G1; 60 days-G2). A stainless steel mould (2 mm x 8 mm Ø) was used. The selected curing modes were: I (Conventional - C): 40s - 600 mW/cm(2); II (Pulse I - PD): 3 s - 200 mW/cm(2) + 2 min (delay) + 39 s - 600 mW/cm(2); III (Pulse II): 10 s - 200 mW/cm(2) + 2 min (delay) + 37 s - 600 mW/cm(2); IV (Pulse III): 3 s- 600 mW/cm(2) + 2 min (delay) + 37 s -600 mW/cm(2). The media used were: distilled water, 75% ethanol and 100% chlorophorm. Five repetitions were made for each group. The specimens were placed in a desiccator at 37 masculineC for 24 h and, after that, at 23 masculineC for 1 h to be weighed until a constant mass (m1) was obtained. The discs were immersed separately into the 3 media for 7 days (G1) and 60 days (G2), and thereafter reweighed (m2). The reconditioning in the desiccator was done until a constant mass (m3) was obtained. Sorption and solubility were calculated and the data of G1 and the sorption data of G2 were subjected to two-way ANOVA and Tukey's tests (p=0.05). The solubility data of G2 were analyzed by Kruskal-Wallis test (p=0.05). For G1 and G2, no statistically significant differences were found in sorption among curing techniques (p>0.05). The solubility values were negative, which means that there was mass gain. Regarding the storage media, in G2 chlorophorm had the highest sorption values. It may be concluded that the curing modes (C and PD I, II and III) did not affect the sorption of the tested composite resin. However, different storage media influenced sorption behavior. The solubility test demonstrated negative data, masking the real solubility.

Removal of the smear layer from flattened canals using different chemical substances.

This study used scanning electron microscopy to evaluate the flattened root canals of human mandibular incisors cleaned with nickel-titanium instruments and different chemical substances. Teeth were selected and divided randomly into five groups (n = 10) according to the chemical substances used in the biomechanical preparation: 5.25% sodium hypochlorite (Group 1), 5.25% sodium hypochlorite plus a final irrigation with 17% EDTAC (Group 2), EDTA gel combined with 5.25% sodium hypochlorite (Group 3), 2% chlorhexidine gel (Group 4), and 5.25% sodium hypochlorite combined with Glyde File Prep gel (Group 5). Data analysis showed a statistically significant difference (p < 0.001) among groups. Groups 1 and 5 were similar statistically (p > 0.001) and displayed a higher amount of smear layer on canal walls. Samples from Groups 2, 3, and 4 revealed root canal walls without smear layer and exposed dentin tubules. Among the associations tested in this study, 5.25% sodium hypochlorite solution combined with 17% EDTAC, 5.25% sodium hypochlorite combined with EDTA gel, and 2% chlorhexidine gel all were effective substances for removing the smear layer from flattened root canals.