Depth of cure of dental composites submitted to different light-curing modes

Abstract

Objective:This study evaluated the depth of cure of five dental composites submitted to different light-curing modes.Material and Methods:Canal-shaped cavities with 5mm of length were prepared on the buccal surfaces of extracted third molars, and restored using P-60, A-110, Admira, Z-250 and Supreme resin composites. Materials were light-cured from the top, according to three modes (Group 1- Conventional (C): 500 mW/cm2/ 40 s; Group 2 – Soft-Start (SS):250 mW/cm2/ 20 s + 500 mW/cm2/ 20 s + 500 mW/cm2/ 10 s and Group 3 – LED: 250 mW/cm2/ 40 s). After that, cavity longitudinal surfaces were polished and marked with a millimeter scale of 4mm of length. Depth of cure was evaluated by means of Knoop hardness number (KHN), so that five indentations were performed at each millimeter. Original data were submitted to three-way ANOVA and Fisher's LSD test (α = 0.01).Results:All materials presented a significant reduction on KHN from first to third millimeter. Regarding depth of cure, the results obtained for Conventional and Soft-Start modes were similar, but statistically superiors to those found for group 3 (LED). Conclusion: This performance may be related to the differences among energy densities obtained with different light-curing modes.

Effects of light curing modes and ethanol-wet bonding on dentin bonding properties

“…This is the main reason for the failure of repair materials (Mohammad et al, 2006). High-light intensity can improve the depth of curing and degree of conversion of the resin monomer to enhance mechanical properties of the composite resin (Nalcaci et al, 2005;Alto et al, 2006;Filho et al, 2008). Since curing speed is proportional to the square root of light intensity (Visvanathan et al, 2007), the curing speed of the high-light mode is faster and this can produce a larger polymerization shrinkage and internal stress within the bonding interface.…”

Nanoindentation study on mechanical properties and curing depth of dental resin nanocomposites

“…Besides the mechanical performance, there are also increasing concerns with the quality of curing when light‐cured dental resin composites are used. Attenuation of the light with time and distance may lead to a low degree of conversion and a shallow curing depth, thereby causing unpolymerized or partially polymerized resins of the final restoration . Low conversion of monomers and/or shallow curing depths will further negatively influence the mechanical properties and dimensional stability of the restoration .…”

Characterization of light‐cured, dental‐resin‐based biocomposites

“…Formerly, halogen lamps were used; however, according to their better characteristics (less power, longer life, minimal heat generation, greater efficacy, etc. ), light‐emitting‐diode lamps replaced them . Photopolymerization is a more appropriate solution for curing composites than chemically activated polymerization according to its faster reaction rate; however, it influences the irradiated material properties …”

“…One of the important properties of light‐cured composites is the depth of cure (DOC); this is defined as the depth of which the material is adequately cured after exposition on blue light . This parameter is affected by many factors, including the composition of the material and light absorption, scattering, and refraction in the depth of the material, filler characteristic (particle size, amount, and type of the filler), irradiation time (a longer irradiation provides a greater DOC), light source characteristics (intensity and spectral distribution), composite color, depth of which the light penetrates the cured material, the distance between the light source and the material, and so on . The DOC influences other properties of the polymerized composite, for example, the mechanical properties (Vickers hardness, elastic modulus, etc.)…”

“…Subsequently, the values of these parameters are compared with the DOC, and some correlations are defined. One of the most popular methods in this group is the determination of the hardness at various depths of the material …”