Ability of Short Exposures from Laser and Quad-Wave Curing Lights to Photo-Cure Bulk-Fill Resin-Based Composites.

Objective: This study investigated the ability of a laser, and a `quad-wave' LCU, to photocure paste and flowable bulk-fill resin-based composites (RBCs). Methods: Five LCUs and nine exposure conditions were used. The laser LCU (Monet) used for 1 s and 3 s, the quad-wave LCU (PinkWave) used for 3 s in the Boost and 20 s in the Standard modes, the the multi-peak LCU (Valo X) used for 5 s in the Xtra and 20 s in the Standard modes, were compared to the polywave PowerCure used in the 3 s mode and for 20 s in the Standard mode, and to the mono-peak SmartLite Pro used for 20 s. Two paste consistency bulk-fill RBCs: Filtek One Bulk Fill Shade A2 (3M), Tetric PowerFill Shade IVA (Ivoclar Vivadent), and two flowable RBCs: Filtek Bulk Fill Flowable Shade A2 (3M), Tetric PowerFlow Shade IVA (Ivoclar Vivadent) were photo-cured in 4-mm deep x 4-mm diameter metal molds. The light received by these specimens was measured using a spectrometer (Flame-T, Ocean Insight), and the radiant exposure delivered to the top surface of the RBCs was mapped. The immediate degree of conversion (DC) at the bottom, and the 24-hour Vickers Hardness (VH) at the top and bottom of the RBCs were measured and compared. Results: The irradiance received by the 4-mm diameter specimens ranged from 1035 mW/ cm(2) (SmartLite Pro) to 5303 mW/cm(2) (Monet). The radiant exposures between 350 and 500 nm delivered to the top surface of the RBCs ranged from 5.3 J/cm(2) (Monet in 1 s) to 26.4 J/cm(2) (Valo X), although the PinkWave delivered 32.1 J/cm(2) in 20s between 350 to 900 nm. All four RBCs achieved their maximum DC and VH values at the bottom when photo-cured for 20 s. The Monet used for 1 s and the PinkWave used for 3 s on the Boost setting delivered the lowest radiant exposures between 420 and 500 nm (5.3 J/cm(2) and 3.5 J/cm(2) respectively), and they produced the lowest DC and VH values. Conclusions: Despite delivering a high irradiance, the short 1 or 3-s exposures delivered less energy to the RBC than 20-s exposures from LCUs that deliver > 1000 mW/cm(2). There was an excellent linear correlation (r > 0.98) between the DC and the VH at the bottom. There was a logarithmic relationship between the DC and the radiant exposure (Pearson's r = 0.87-0.97) and between the VH and the radiant exposure (Pearson's r = 0.92-0.96) delivered in the 420-500 nm range. (c) 2023 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.