Microhardness and Diametral Compression Strength of Single Fill Composite

ABSTRACT: To evaluate Knoop microhardness and diametral compression strength at different polymerization times. A total of 80 cylindrical samples with Filtek resin™ One Bulk Fill were made to perform the in vitro study, using half of total samples (n=40) for each test and divided equally between groups (n=10). All samples were made according to ISO 4049 using 2 mm thickness Teflon matrix and a central orifice with 4 mm diameter. Four different times of light-curing in Standard mode suggested by the light-unit manufacturer were selected, therefore, group 1 samples (G1) were light-cured for 5 seconds; group 2 (G2) for 10 seconds; group 3 (G3) for 15 seconds, and group 4 (G4) for 20 seconds. A radiant display, which means a power in mW/cm2 by time in seconds was expressed in Joules (J). The samples were stored in a dark container with distilled water at a temperature of 37°C for 48 hours before testing. One-way analysis of variance (ANOVA) with T-Test (LSD) of multiple comparisons of the mean values of Knoop hardness and diametral compression strength was performed, with significance index α=0.05. Regarding the Knoop microhardness test, G1 (35.73 ± 6.2) presented the lowest values, followed by G2, while G3 and G4 did not present statistical differences between them. For the diametral compression test, G1 (1387.76 ± 190.51) obtained the lowest value when compared to the other groups. G2, G3, and G4 did not present significant statistical differences. The different polymerization times influenced the Knoop microhardness and the diametral compression strength of Bulk Fill resin.

RESUMEN: El objetivo de este trabajo fue evaluar la microdureza Knoop y la resistencia a la compresión diametral en diferentes tiempos de polimerización. En el estudio realizado in vitro, se analizó un total de 80 muestras cilíndricas con la resina Filtek™ One Bulk Fill, utilizando la mitad (n=40) para cada prueba realizada y dividida en partes iguales entre los grupos (n=10). Todas las muestras se tomaron de acuerdo con ISO 4049 utilizando matrices de teflón de 2 mm de espesor y orificio central con 4 mm de diámetro. Se seleccionó cuatro veces el fotocurado de manera estándar, sugerido por el fabricante. Por lo tanto, las muestras del grupo 1 (G1) se fotopolimerizaron durante 5 segundos; grupo 2 (G2) durante 10 segundos; grupo 3 (G3) durante 15 segundos y grupo 4 (G4) durante 20 segundos. La exposición radiante, que indica la potencia en mW / cm2 a lo largo del tiempo en segundos, se expresó en julios (J). Las muestras se almacenaron en un recipiente oscuro con agua destilada en una estufa a una temperatura de 37°C durante 48 horas antes del ensayo. Se realizó para comparaciones múltiples de los valores medios, análisis de varianza (ANOVA) de un criterio con la prueba T (LSD) tanto de la dureza de Knoop como de la compresión diametral con un índice de significación α=0.05. Con respecto a la prueba de microdureza de Knoop, G1 (35,73 ± 6,2) tuvo los valores más bajos, seguido de G2, mientras que G3 y G4 no mostraron diferencias estadísticas entre ellos. Para la prueba de compresión diametral, G1 (1387.76 ± 190.51) obtuvo el valor más bajo en comparación con los otros grupos. G2, G3 y G4 no presentaron diferencias estadísticamente significativas. Los diferentes tiempos de polimerización influyeron en la microdureza de Knoop y la resistencia a la compresión diametral de la resina compuesta mono incremental.

Influence of polishing systems on roughness and color change of two dental ceramics.

PURPOSE: To evaluate the polishing effect on roughness and color change of pressed and layering ceramics after immersion in coffee solution. MATERIALS AND METHODS: 88 ceramic discs (1.0 mm × 10.0 mm) were manufactured - 44 nano-fluorapatite layering ceramics (IPS e.max Ceram. Group C) and 44 pressed lithium disilicate ceramic discs (IPS e. max Press - Group P). Each group was divided into 4 subgroups according to surface treatments: (G) Glaze, (S) Shofu polishing system (Shofu Inc.), (E) Edenta AG polishing System, (KG) 30-µm diamond granulation tip. Surface roughness (Ra) and color change (ΔE) measurings after the surface treatments were performed, before and 12 days after the immersion in coffee solution. A samples' qualitative analysis was conducted with a scanning electron microscopy (SEM). Data were statistically-treated with one-way-ANOVA and Duncan's tests, apart from paired t-test and Pearson's correlation test (α=5%). RESULTS: The decrescent order, both for surface roughness (Ra) and ΔE for both ceramics were: KG > E > S > G (P<.05). With exception for PG and CG subgroups, which did not present statistical difference between them, all other pressed ceramics subgroups presented smaller Ra values and greater ΔE values than the layering ceramics subgroups (P<.05). CONCLUSION: Although mechanical polishing systems presented intermediate Ra values, their colors were considered clinically acceptable. There is a strong correlation between the surface roughness and the color change of tested ceramics.