Effect of LED and halogen light curing on polymerization of resin‐based composites

Abstract

The clinical performance of light polymerized resin-based composites (RBCs) is greatly influenced by the quality of the light curing unit (LCU). A commonly used unit for polymerization of RBC material is the halogen LCUs. However, they have some drawbacks. Development of new blue superbright light emitting diodes (LED LCU) of 470 nm wavelengths with high light irradiance offers an alternative to standard halogen LCU. The aim of this study is compared the effectiveness of LED LCU and halogen LCU on the degree of conversion (DC) of different resin composites [two hybrid (Esthet-X, Filtek Z 250), four packable (Filtek P60, Prodigy Condensable, Surefil, Solitaire), one ormocer-based resin composite (Admira)]. The DC values of RBCs polymerized by LED LCU and halogen LCU ranged approximately from 61.1 +/- 0.4 to 50.6 +/- 0.6% and from 55.6 +/- 0.7 to 47.4 +/- 0.5%, respectively. Significantly higher DC of RBCs except Surefil and Filtek Z 250 was obtained for LED LCU compared with halogen LCU (P < 0.05). Surefil and Filtek Z 250 exhibited no statistically significant difference values between LED LCU and halogen LCU (P > 0.05). As a result, it was observed that the performance of LED LCU used in the study was satisfactory clinically and had sufficient irradiance to polymerize RBCs (hybrid, packable and ormocer based) at 2 mm depth with a curing time of 40 s.

Continuous and gradual photo-activation methods: influence on degree of conversion and crosslink density of composite resins

“…3). Similar results were found by Bala et al [58]. In the samples photo-activated by Elipar Freelight TM LCU, the lowest DC% value was obtained by a microhybrid composite resin Filtek TM Z-250.…”

“…This difference in composite resins based on urethane dimethacrylates is because these materials differ in many other aspects, e.g., amount of filler, initiators, and silanation of the filler particles [58]. This statement may explain the results found in this study.…”

Wavelength of Experimental LEDS: Hardness, Elastic Modulus, Degree of Conversion and Temperature Rise of a Microhybrid Composite

“…When inadequately polymerized, composites can have their biological, physical and mechanical properties compromised 2,3 . As a result, marginal degradation and discoloration 4 , postoperative sensitivity and pulp irritation may occur 1,5 . The efficiency of polymerization depends on several factors, including those related to the material itself in terms of its composition 1,6 , and those related to the light-curing unit (LCU), such as light intensity, spectral distribution, thermal emission and exposure time 7 .…”

“…The efficiency of polymerization depends on several factors, including those related to the material itself in terms of its composition 1,6 , and those related to the light-curing unit (LCU), such as light intensity, spectral distribution, thermal emission and exposure time 7 . LED (Light Emitting Diode) LCUs are gradually replacing halogen LCUs because they have a longer lifetime, and the light flux is not compromised with time 4,8 . A suitable photoactivation process is of great importance to emit radiant energy at a specific wavelength 9,10 .…”

“…Nanoindentation is one of the methods that can be used to determine not only the hardness but also the elastic modulus of the composite through curves of applied load and penetration on the specimen surface 14,15,16 . The efficiency of polymerization can also be evaluated by studying the degree of conversion (DC), 4 which can be reached by Fourier Transform Infrared Spectroscopy (FTIR) 3,4,17,18 . Several studies have been conducted focusing on the relationship between the energy density of LED LCUs and the degree of polymerization of composites 17,19,20 .…”