Comparing depth-dependent curing radiant exposure and time of curing of regular and flow bulk-fill composites

Abstract

The effect of restoration depth on the curing time of a conventional and two bulk-fill composite resins by measuring microhardness and the respective radiosity of the bottom surface of the specimen was investigated. 1-, 3-and 5-mm thick washers were filled with Surefil SDR Flow-U (SDR), Tetric EvoCeram Bulk Fill-IVA (TEC) or Esthet-X HD-B1 (EHD), and cured with Bluephase ® G2 for 40s. Additional 1-mm washers were filled with SDR, TEC or EHD, placed above the light sensor of MARC ® , stacked with pre-cured 1-, 3-or 5-mm washer of respective material, and cured for 2.5~60s to mimic 2-, 4-and 6-mm thick composite curing. The sensor measured the radiosity (E B ) at the bottom of specimen stacks. Vickers hardness (VH) was measured immediately at 5 locations with triplicate specimens. Nonlinear regression of VH vs E B by VH=α[1-exp(-E B /β)] with all thickness shows that the values of α, maximum hardness, are 21.6±1.0 kg/mm 2 for SDR, 38.3±0.6 kg/mm 2 for TEC and 45.3±2.6 kg/mm 2 for EHD, and the values of β, rate parameter, are 0.40±0.06 J/cm 2 for SDR, 0.77±0.04 J/cm 2 for TEC and 0.58±0.09 J/cm 2 for EHD. The radiosity of the bottom surface was calculated when the bottom surface of each material attained 80% of α of each material. The curing times for each material are in agreement with manufacturer recommendation for thickness. It is possible to estimate time needed to cure composite resin of known depth adequately by the radiosity and microhardness of the bottom surface.

Evaluation of irradiance and radiant exposure on the polymerization and mechanical properties of a resin composite

“…Literature describes several methods to evaluate the depth of cure, 32,33 making it difficult to compare our results with other studies; however, our data still agreed with the reported literature. 20,32 The results of this study showed a statistically significant difference for group Low 16 J/cm 2 , when compared to other groups (Figure 1).…”

“…11,15 However, this work verified that this value could be overestimated, and a radiant exposure of 8 J/cm 2 was sufficient to achieve adequate properties in terms of depth of cure. However, depth of cure is a material-dependent variable [32][33][34] suggesting that intrinsic factors, such as the resin color and translucency could affect the light scattering during the photoactivation time. 35,36 Irradiance and the duration of exposure a r e i mp or t a nt fac tor s i n r e si n comp o sit e polymerization.…”

Profundidade de cura das resinas bulk fill variando a fonte de luz

“…No intuito de corrigir algumas desvantagens da técnica incremental foram desenvolvidas as resinas bulk fill, elas podem ser inseridas na cavidade em profundidades de 4 a 5 mm (Savadamoorthi et al, 2017). A apresentação destas resinas pode ser em pasta ou fluida, sendo essa última utilizada como base para uma resina bulk-fill pasta ou uma resina convencional, por não apresentar resistência ao desgaste (Savadamoorthi et al 2017;Rodrigues et al 2017;P et al 2020).…”