A method for improving the light intensity distribution in dental light-curing units

Abstract

A method for improving the uniformity of the radiation light from dental light-curing units (LCUs), and the effect on the polymerization of light-activated composite resin are investigated. Quartz-tungsten halogen, plasma-arc, and light-emitting diode LCUs were used, and additional optical elements such as a mixing tube and diffusing screen were employed to reduce the inhomogeneity of the radiation light. The distribution of the light intensity from the light guide tip was measured across the guide tip, as well as the distribution of the surface hardness of the light-activated resin emitted with the LCUs. Although the additional optical elements caused 13.2-25.9% attenuation of the light intensity, the uniformity of the light intensity of the LCUs was significantly improved in the modified LCUs, and the uniformity of the surface hardness of the resin was also improved. Our results indicate that the addition of optical elements to the LCU may be a simple and effective method for reducing inhomogeneity in radiation light from the LCUs.

Effect of curing distance for cure depth in composite resin

“…A number of variables, such as power density, exposure duration, resin color, filler size, and filler loading, affect how well composite materials cure. Some authors propose an inverse square law, according to which light intensity falls according to the square of the distance between the light source and the outer layer of the beneficial material (DLR) [ 9 - 10 , 11 , 12 ]. The curing duration, dimensions, the spot, and positioning of the light tip, the depth, shading and chemical structure of the substance that is being cured, as well as the wavelength and strength of light output emanating from the curing unit all affect the degree of polymerization [ 13 , 14 ].…”

Comparison of two light guide tips used to photo-polymerize two dental composites. An in-vitro study

“…The LED light guide tip forms part of the LCU and is responsible for the transmission, distribution and dispersion of light energy from the LED source to the surface of the resin based composite restoration. [13][14][15][16][17] The transmission distribution and dispersion across the face (surface) of the light guide tip has a great impact on the polymerization kinetics of resin based composites. 14,15,18,19 These factors can affect the polymerization shrinkage, associated stresses, micro-hardness, depth of cure, degree of conversion and water sorption of water soluble resin based composites, effects that may result in post-operative sensitivity, micro-leakage and restoration failure.…”

“…[13][14][15][16][17] The transmission distribution and dispersion across the face (surface) of the light guide tip has a great impact on the polymerization kinetics of resin based composites. 14,15,18,19 These factors can affect the polymerization shrinkage, associated stresses, micro-hardness, depth of cure, degree of conversion and water sorption of water soluble resin based composites, effects that may result in post-operative sensitivity, micro-leakage and restoration failure. 14,15,[20][21][22][23] It is therefore important that the light guide tip remains undamaged, clean and unobstructed so that it functions at an optimal level.…”

“…[24][25][26][27][28][29][30] These conditions and specifications have to be operating optimally, together with the appropriate light curing techniques, in order for the resin based composite restorations to be successfully cured. 4,14,23,24,[29][30][31][32][33][34][35][36][37] The wavelength of the LCU used in this experiment initiated activation of the photo-initiator in both resin specimens. The radiometer was used to test each light guide tip before each specimen was made, to ensure that the light intensity was sufficient to photo-polymerize each resin specimen.…”

Estudo in vitro do efeito de unidades fotoativadoras com diferentes comprimentos de onda na dureza (por meio de micro e ultramicroendentação) e módulo de elasticidade de uma resina composta nanohíbrida

“…Dentre as propriedades mecânicas, a dureza é utilizada como um método indireto de avaliação do grau de polimerização das resinas compostas (Rode et al, 2009) tendo sido utilizado para este fim em inúmeros trabalhos (Peris et al, 2005;Price et al, 2005;Rode et al, 2007;Hubbezoglu et al, 2007;Gritsch et al, 2008;Machado et al, 2008;Firoozmand et al, 2009;Jeong et al, 2009;Rode et. al., 2009;Arikawa et al, 2011;Juchem et al, 2011;El-Safty et al, 2012 (Craig;Powers, 2004).…”