Influence of Light Source and Photopolymerization Distance On Composite Resin Microhardness - Influence of Light Source and Photopolymerization Distance On Composite Resin Microhardness - Open Access Pub

The present study evaluated in vitro the influence of two light sources in composite resin microhardness in different distances of photopolymerization. Two light sources were used (halogen, LED) to photopolymerize the composite resin (Filtek Z250; Esthet-X) in different distances surface (1,2,3 and 4 mm), totalizing 96 specimens. Microhardness Knoop test’ were made on the specimens top and bottom faces. The data were submitted to ANOVA and Fisher tests (α=5%). It was observed a significant difference (p<0.05) between the resins, in which Z250 presented higher values than Esthet-X (p<0.05). There was difference also between the halogen and LED, where the halogen showed better results with Z250 and the LED with Esthet-X. The top surface presented better value (p<0.05) compared to the bottom surface. It can be concluded that the light source and the photopolymerization distance influenced the composite resin microhardness, which it had lower proprieties with increase of the photopolymerization distance. DOI 10.14302/issn.2473-1005.jdoi-16-1079 The search for excellence in esthetic dentistry and the high demand of esthetical procedures, had proportioned to development of the new studies to evaluate composite resin behavior, besides refining equipments and photopolymerization techniques1 as well as reducing the clinical time spent in restorations by the professional. The availability of resin systems activated by light led to the development of a wide variety of technologies to produce the necessary light to their use, as for example: the quartz-tungsten halogen light (QTH), is mostly used by professionals2, and the light produced by diode (LED)3, was introduced in 1995, have a wave length between 450-490nm, with a peak of 470nm4. In order to obtain an appropriate photopolymerization of a composite resin, it is necessary the right amount of light intensity5, time and adequate wavelenght6. High light intensity promotes temperature increase7 and consequently high values in terms of conversion measurement besides, better physical and mechanical properties from the restoratives materials. Moreover, the increase of temperature shows significant effect on microhardness8. Nevertheless, the decrease on the mechanic properties of hardness is an indicative of a lesser conversion measurement by the presence of residual monomers9. In this aspect, a correlation has been established between the microhardness of the material and the polymerization degree10. From this way, the microhardness tests have been an adequate indicator regarding the conversion degree of monomers in