Abstract To evaluate the polymerization shrinkage stress and cuspal strain (CS) generated in an artificial (typodont) and in a natural tooth using different resin composites. Twenty artificial and 20 extracted natural molars were selected. Each tooth was prepared with a 4x4 mm MOD cavity. The natural and typodont teeth were divided into four experimental groups (n=10), according to the resin composite used: Filtek Z100 (3M Oral Care) and Beautifil II LS (Shofu Dental). The cavities were filled using two horizontal increments and the CS (µS) was measured by the strain gauge method. Samples were sectioned into stick-shaped specimens and the bond strength (BS) (MPa) was evaluated using a microtensile BS test. Shrinkage stress and CS were analyzed using 3D finite element analysis. No difference was found between the type of teeth for the CS as shown by the pooled averages: Natural tooth: 541.2 A; Typodont model: 591.4 A. Filtek Z100 CS values were higher than those obtained for Beautifil II LS, regardless of the type of teeth. No statistical difference was found for the BS data. Adhesive failures were more prevalent (79.9%). High shrinkage stress values were observed for Filtek Z100 resin, regardless of tooth type. The CS of typodont teeth showed a shrinkage stress effect, generated during restoration, equivalent to that of natural teeth. (CS (typodont composites 2 selected x 4x cavity n=10, n10 n n=10 , 10 (n=10) used Z Z10 3M M Care Shofu Dental. Dental . Dental) µS (µS method stickshaped stick shaped (BS MPa (MPa test D analysis averages 5412 541 541. A model 5914 591 4 591. data 79.9%. 799 79.9% 79 9 (79.9%) effect restoration n1 n=1 1 (n=10 Z1 54 59 79.9 7 (79.9% n= (n=1 5 79. (79.9 (n= (79. (n (79 (7 (

Abstract This study evaluated the optical method for measuring free total shrinkage using a Digital Single Lens Reflex (DSLR) camera. Eight composites were evaluated, conventional, bulk fill and low-shrinkage: Z100 (3M Oral Care), Gradia Direct Anterior (GC corporation), Spectra Smart (Dentsply), Filtek Z350 XT (3M Oral Care), Aura Bulk Fill (SDI), Vittra APS (FGM), Opus Bulk Fill APS (FGM), and Beautifil II LS (Shofu Inc.). The samples (6 mm diameter and 1.5 mm thick, n = 10) were placed on a polyvinylsiloxane impression material. An image of the uncured sample was captured using a DSLR camera with 105 mm macro lens and a ring flash. Samples were light cured with a 700 mW/cm2 LED light-cure unit for 40s. Post-polymerization images were captured at 2, 10 and 60 min. Projected circumferential areas of the specimens were drawn using the ImageJ software. Volumetric total shrinkage was calculated from the ratio of the areas obtained from pre- and post-curing. Results were analyzed using One-way ANOVA (α = 0.05) and Tukey test. Volumetric total shrinkage values were significantly different among the composite materials (p < .001). The volumetric shrinkage (%) mean and results of Tukey test at 60 min were: Z100: 3.45±0.30 (A); Gradia Direct Anterior: 3.00 ± 0.23 (B); Spectra Smart 2.89 ± 0.35 (B); Filtek Z350 XT: 2.65 ± 0.37 (BC); Aura Bulk Fill: 2.42 ± 0.25 (CD); Vittra APS: 2.14 ± 0.35 (DE); Opus Bulk Fill APS: 1.91 ± 0.24 (E); Beautifil II LS: 1.18 ± 0.16 (F). The optical method using a DSLR camera, was suitable for total shrinkage evaluation and will allow assessment of total shrinkage without the need for specialized equipment.

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.

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.