Effect of radiant heat induced by a diode laser (445 nm) on setting process of glass-ionomer cements monitored by Fourier transform infrared spectroscopy

Abstract

Objectives: The aim of this study was to investigate the effect of thermal energy induced by a diode laser (445 nm) on the setting reactions of conventional glass ionomer cements (GICs) by using Fourier transform infrared spectroscopy (FTIR) and to compare it with that induced by a LED device.

Methods: Four GICs were investigated in this study (GlassIonomer FX Ultra, Ketac Universal Aplicap, Equia Fill, and Riva Self Cure). The experimental groups of the study were as follows (n = 5): Group 1 (control) - the specimens after mixing were left to set without any treatment; Group 2 - the specimens were irradiated for 60 s using a LED (Valo™) at 1400 mW/cm² (fluence ∼ 1.4 J/cm²); Group 3 - the specimens were also irradiated for 60 s using a diode laser (SIROLaser Blue), which emits at 445 ± 5 nm with average output power of 0.7 W (fluence ∼ 1.4 J/cm²). FTIR analysis of the GIC specimens was followed to assess the changes in the COO-/CO ratios of the setting reaction and its progress in time.

Results: Both laser and LED treatments improved the setting reactions of the GICs compared to the control group (p < 0.05). However, this phenomenon was not observed in all materials implying that it may be material dependent.

Significance: Radiant heat treatments using diode laser or LED may be beneficial for the rate and progress of setting reaction of the conventional GICs. The composition and handling of the materials may be crucial for their final properties and the overall clinical behavior.

Keywords: Conventional glass ionomer cements; Diode laser; Fourier transform infrared spectroscopy; Light-emitting diode; Thermo-curing.