Effect of Light Intensity on Polymerization of Light-cured Composite Resins

Abstract

The depths of cure and the distributions of degree of conversion (DC), polymerization conversion (PC) and percent pendant double bonds (PDB) of light-cured composite resins cured under various intensities of light were investigated. When the total amount of exposure, represented by the product of the light intensity and the irradiation time, was kept constant, each of the depth of cure and the distributions of DC, PC and PDB were the same for each material regardless of the light intensity and irradiation time. The depth of cure could be expressed as a logarithmic function of the total amount of exposure. From regression analysis, the attenuation coefficient and the critical total amount of exposure capable of initiating polymerization of each composite resin could be determined.

Influence of ceramic thickness on mechanical properties and polymer structure of dual-cured resin luting agents

“…For light-cured resin materials, the reduction of energy density of light irradiation can decrease the degree of conversion (DC) and mechanical properties [1][2][3][4], which limits the application of light-cured resin luting agents in the bonding of thicker esthetic restorative materials.…”

Effect of the increase of energy density on knoop hardness of dental composites light-cured by conventional QTH, LED and xenon plasma arc

“…For camphoroquinone, which is the most used photoinitiator system in dental composites, the maximum absorption peak is within the blue spectrum of visible light, about 468 nm (12). When similar energy densities are supplied to the composite resins, similar degrees of conversion and depth of polymerization will be obtained, regardless of the light-curing mode (9,10). Increased degree of conversion can play important roles in the mechanical properties of composites, such as decrease of solubility, improvement of dimensional stability, lesser color alteration and greater biocompatibility (13).…”

“…The energy density required to obtain optimal mechanical properties of the composites can vary depending on the shade, opacity, initiators and composition of the materials. Moreover, the increment volume and cavity configuration have an important role (10,11). The light intensity should be compatible with the absorption wavelength spectrum of the photoinitiator systems.…”

Influence of shade and irradiation time on the hardness of composite resins

“…As the ideal wavelength to excite a-1,2-diketone is about 468 nm (1), thus the white light emitted from this type of curing unit must be filtered at the output to a range of blue light (400-500 nm) (5,6). Despite their popularity, quartz tungsten halogen units present several shortcomings, such as the restricted depth of cure, heat generation and relatively long irradiation time (7,8).…”

“…The irradiance of light emission depends on the power (Watts) of the curing unit as well as the time (seconds) and the surface area (cm 2 ) where the light is spread over (9). The energy density (irradiance x irradiation time) (10) influences the degree and depth of cure and the mechanical properties of light cured resin composite (1,8,10). The degree of polymerization of these materials is basically proportional to the material thickness and irradiation time (1), which depend on some variables, such as type of material, composite shade, distance and quality of light source.…”