Comparison of Dental Curing Units and Output Modes Regarding Radiant Flux, Tip Diameter, Radiant Emittance, Scattering, and Penetration Depth

Abstract

Objective: To compare radiant flux, radiant emittance, light scattering, and penetration depth of high-power and low-power dental LED curing units (LCUs) and different output modes. Materials and methods: Ten different, brand-new dental LCUs and different output modes were tested by a laboratory-grade spectroradiometer to evaluate radiant flux and spectral emission. Two radiant emittance values were calculated using the radiant flux values for each curing unit/output mode, together with manufacturer's tip diameter or measured internal tip diameter. Light source width, scattering, total penetration depth (TPD), and main penetration depth (MPD) were also assessed through collected light beam images using Rhodamine B solution. Image processing was done using the Photoshop software to measure the distances. The deemed significance was set at < 0.050 for the statistical analyses. Results: Measured internal tip diameters were different than stated diameters for all LCUs except Valo X. Valo X Xtra Power mode delivered the highest radiant flux (2704 +/- 5 mW), followed by Valo Grand Xtra Power mode (2576 +/- 6 mW)(P <.001). The lowest radiant flux was from D Light Pro Low Power mode (449 +/- 9 mW)(P <.001). Calculated radiant emittances based on the manufacturer's stated and measured internal tip diameters were up to 27.6% lower than the stated radiant emittances. A positive correlation was observed for TPD, light source width, and radiant emittance (P <.001). Scattering had negative correlations with TPD (P =.014), radiant emittance (P =.003), and tip diameter (P =.007). Conclusions: The radiant emittance can deviate from the manufacturer's stated values by up to 27.6%. Regular spectroradiometer measurements can be beneficial in this regard to adjust the curing time and thereby calibrate the clinical curing dose. Greater penetration depth can be expected when using LCUs with greater radiant emittance and tip diameter, while the curing mode was considered ineffective on the scattering pattern. Clinical relevance: Effective light-curing is a complicated clinical procedure in dentistry requiring many parameters. There might be some deviations in these features from the manufacturer's stated values. Clinicians should select the LCUs by considering the radiant flux, tip diameter, radiant emittance, light scattering, and penetration depth features to succeed in clinical restorative procedures.