High-Power LED Units Currently Available for Dental Resin-Based Materials—A Review

Abstract

The pursuit of less time-consuming procedures led to the development of high-power light-curing-units (LCU) to light-cure dental-resin-based-materials. This review aims to describe high-power light-emitting-diode (LED)-LCUs, by a bibliometric systematization of in vitro and in vivo studies. The research-question, by PICO model, aimed to assess the current knowledge on dentistry-based high-power LED-LCUs by analyzing to what extent their use can promote adverse events on materials and patients’ oral condition when compared to low-power LED-LCUs, on daily dental practice. PubMed and B-on database search focused on high-power (≥2000 mW/cm2) LED-LCUs outputs. Studies assessing performance of high-power LED-LCUs for light-curing dental-resin-based-materials were included. From 1822 screened articles, 21 fulfilled the inclusion criteria. Thirty-two marketed units with high levels of radiant emittance (≥2000 mW/cm2 up to 6000 mW/cm2) were identified. Most output values vary on 2000–3000 mW/cm2. The highest output found was 6000 mW/cm2, in FlashMax™P3. Reports suggest that light-curing protocols with lower emittance irradiance and longer exposure outperforms all other combination, however in some clinical procedures high-power LED-LCUs are advocated when compared to low-power LED-LCUs. Moreover, long time exposures and over-curing can be dangerous to the biological vital pulp, and other oral tissues. Evidence showing that high-power LCUs are the best clinical option is still very scarce.

Irradiance from 12 LED light curing units measured using 5 brands of dental radiometers

“…11 Consequently, the irradiance values alone are less reliable than power measurements, 36 and a single irradiance value alone cannot fully describe the output of an LCU. 34 This study also agrees with a previous study, where the authors reported no correlation between the cost of the LCU and their irradiance values, but there was a high positive correlation between the cost and the power output and tip diameter. 52 In general, the budget LCUs delivered a lower power.…”

“…Even LCUs that deliver a low irradiance can still photo-cure the top surface of the resin restoration to the extent that it will feel hard to the dental explorer. Consequently, the LCU should ideally be checked daily [34][35][36] to ensure that the LCU is functioning correctly before it is used on patients.…”

“…Some LED LCUs emit a single peak wavelength of light that is usually around 450 nm (mono‐peak). Other brands of LCUs contain several different LED emitters so that they can emit a broader range of wavelengths with multiple wavelength peaks, each corresponding to the LED emitter used in the LCU 34,37 . These are called multi‐peak or polywave™ LCUs.…”

In‐vitro pulpal temperature increases when photo‐curing bulk‐fill resin‐based composites using laser or light‐emitting diode light curing units

“…The first light‐emitting diode (LED) based LCUs were considered to be ‘cool’ because they delivered a lower irradiance (approximately 240 mW/cm 2 ) than the quartz tungsten halogen based LCUs (approximately 450–1200 mW/cm 2 ) 8 . Many LED lights now deliver irradiances greater than 2000 mW/cm 2 , and some manufacturers claim that exposure times shorter than 5 s may be used to reduce photo‐cure RBCs and reduce clinical time 13 . However, such high irradiance values have become a concern due to the potential risk to the soft tissues 14 and the dental pulp 10,15 .…”

“…8 Many LED lights now deliver irradiances greater than 2000 mW/cm 2 , and some manufacturers claim that exposure times shorter than 5 s may be used to reduce photo-cure RBCs and reduce clinical time. 13 However, such high irradiance values have become a concern due to the potential risk to the soft tissues 14 and the dental pulp. 10,15 Using monkeys, Zach and Cohen in 1965 16 reported that an increase in PT of 5.5 C resulted in pulpal necrosis in 15% of the cases, and a temperature rise (ΔT) of 11 C resulted in pulpal necrosis in 60% of the cases.…”