Effect of light-curing distance and curing time on composite microflexural strength

Abstract

This study investigated the influence of curing distance on µ-flexural strength (µ-FS) of a nano-hybrid composite, cured using the manufacturer-recommended curing time (MCT), compared to a consistent radiant exposure (CRE) using three different light-curing units (LCUs). Beams (6×2×1 mm) were cured using the MCT or CRE with a quartz-tungsten-halogen (QTH); a single-emission-peak light-emitting-diode (SLED), or a multiple-emission-peak light-emitting-diode (MLED) LCU. Specimens were cured at 0-, 2-or 8-mm distances (n=10) and the bottom irradiance and CRE were measured using a Managing Accurate Resin Curing-Resin Calibrator spectrometer. µ-FS testing was performed, and data analyzed using two-way ANOVA and Tukey multiple comparison tests (α=0.05). Mean bottom irradiance was (25.4-99.7 mW/cm 2) and CRE (0.31-1.11 J/cm 2). µ-FS was 422.1-516.6 MPa (MCT) and 440.4-490.4 MPa (CRE). Comparing CRE to MCT showed that µ-FS significantly decreased using the CRE at 2-mm (QTH) or the MCT at 2-and 8-mm (SLED). µ-FS may be significantly impacted by the curing protocol.

Effects of aging and light-curing unit type on the volume and internal porosity of bulk-fill resin composite restoration

“…Aspects such as the LCU position, RBC type, and shade were standardized to minimize any confounding factors. The teeth were flattened to allow all restoration areas to receive a similar amount of irradiance ( Alqudaihi et al, 2019 ); one-shot curing was ensured for all the restorations ( Al-Zain et al, 2018 , Al-Zain and Platt, 2020 , Eshmawi et al, 2018 ); the light guide tip was positioned centrally to standardize the delivery of energy ( Al-Zain et al, 2018 , Price et al, 2011 , Shimokawa et al, 2018 ); and a curing distance of 2 mm was used to simulate a clinical setting ( Al-Zain et al, 2018 , Price et al, 2011 ). Thus, we controlled many of the potential important operational aspects that may affect the polymerization of the restorations, thereby enabling the acquisition of accurate data.…”

“…The MLED equipment tested in this study has a nonhomogenous irradiance beam profile, which enables different blue and violet photons and a radiant distribution across the LCU tip ( Shimokawa et al, 2018 ). According to some studies ( Al-Zain et al, 2019a , Al-Zain et al, 2018 , Al-Zain and Platt, 2020 , Eshmawi et al, 2018 ), up to 95% of the radiant exposure/irradiance may be lost from the top to the bottom areas during light transmission through RBCs as thin as 1–2 mm. Similarly, ∼10% of the light emitted by an LCU reaches the bottom areas of a 4-mm bulk-fill RBC ( Shimokawa et al, 2018 ), and a violet spectral emission may no longer be detected at the bottom of 2-mm-deep specimens ( Al-Zain et al, 2018 , Al-Zain et al, 2019b ).…”

Evaluación del tiempo de exposición de una resina Bulk-Fill en preparaciones profundas

“…Los resultados mostraron una disminución del 92-95% en la irradiancia de la superficie superior comparada con la superficie inferior. Esto implica que gran parte de la luz se dispersa en la superficie superior de una muestra (16). Algunos autores consideran que un valor de microdureza que supera los 50 HV es considerado ideal para las resinas compuestas (17).…”

Effect of Battery Discharge on the Output from Budget Light-Curing Units

“…To produce resin-based composites (RBCs) that achieve their intended mechanical, chemical, and physical properties, the light-curing unit (LCU) must deliver sufficient energy at the correct wavelengths to the RBC. 1 2 3 4 5 6 7 8 9 10 In most countries, LCUs are classified as medical devices and should comply with standards set by the regulatory authorities. However, some manufacturers, mainly from China, have introduced budget LCUs claiming that their devices are similar to those from major dental manufacturers, but they cost much less.…”