Impact of Battery Levels of a Cordless LED Curing Unit on Resin Cement under Varied Lithium Disilicate Thicknesses and Translucencies
This study aimed to evaluate the impact of battery levels on the emission of a multi-peak cordless LED light-curing unit (LCU) and the effect on the degree of conversion (DC) and Knoop hardness (KH) of a light-cure resin luting agent activated through varying lithium disilicate (LiS2) ceramic thicknesses and translucencies. High and low translucency LiS2 discs (IPS e.max Press HT and LT, respectively; shade A1) with thickness of 0.5, 1.0, 1.5, and 2.0 mm were fabricated. Resin luting agent specimens (Variolink Esthetic LC) were prepared and cured using a Bluephase G2 LCU at different battery levels (100%, 50%, and 10%) through the LiS2 ceramics. The transmitted irradiance was evaluated using USB4000 MARC, while FTIR and a microhardness tester assessed DC and KH, respectively. After ensuring homoscedasticity, the data wee analyzed using analysis of variance and Tukey HSD test (α=0.05). The study found strong positive correlations between battery levels and irradiance, particularly with no ceramic interposition and through HT ceramics (R2=0.9471), although this correlation diminished with thicker HT (R2=0.7907) and LT ceramics (R2<0.2980). Both battery levels and ceramic thickness significantly influenced transmitted irradiance (p<0.0001), resulting in lower values with decreased battery levels and increased ceramic thicknesses (p<0.0001). LT ceramics showed lower transmittance than HT. DC was significantly affected by both battery levels and ceramic thicknesses, with generally lower DC values except for LT ceramics at a 10% battery level (p<0.0001). No significant differences in DC were observed between HT and LT translucencies (p=0.548). KH was higher in HT than LT ceramics at 100% and 50% battery levels, with thicker ceramics showing lower KH values at 10% battery level (p<0.0001). Conclusion: Reduced battery levels in cordless LED curing units significantly affect the irradiance, degree of conversion, and hardness of light-curable resin luting agents. Maintaining battery levels above 50% is recommended for optimal performance. Thicker and more opaque ceramics significantly impacted incident irradiance. However, preserving radiant energy could potentially mitigate these limitations.SUMMARY
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Schematic illustration of methods used in this study. Ceramic discs (LT and HT) with a diameter of 12.0 mm and four different thicknesses (0.5, 1.0, 1.5, and 2.0 mm). A resin luting agent was placed in a PVS mold and light-activated through the ceramic discs. DC assessed at the top surface; same surface used for KHN. The specimen's colored areas (violet or blue) indicate the placement of LEDs within the LCU, corresponding to the KHN values reported.
Emission spectrum (mW/cm2/nm) of the cordless LED LCU (Bluephase G2) at high mode measured using the cosine corrector (MARC) through the different ceramic thicknesses, translucencies, and battery levels.
Percentage (%) of maximum (control) Knoop Hardness of a resin luting agent, measured at varying battery levels of the Bluephase G2, through different ceramic thicknesses and translucencies. Additionally, each LED region of the multiwave LED is individually identified. Brackets marked with an asterisk denote statistical significance at the following levels: *p<0.05; **p<0.01; ***p<0.001; ****p<0.0001.
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