Aim This study investigated the influence of different composite resin organic matrix (methacrylate – Filtek Z350 XT and silorane – Filtek P90) on light energy transmission through the composite and bottom/top rate. Materials and methods A light-emitting diode (New Blue Phase), light-curing unit was used with different photoactivation protocols (high-continuous mode – HCM, 1400 mW/cm2 for 20 seconds; low-continuous mode – LCM, 700 mW/cm2 for 40 seconds; and soft-start mode – SSM, 140 mW/cm2 for 5s followed by 39 seconds for 700 mW/cm2). Twenty specimens were prepared for each composite. The light energy transmission through the composite was calculated (n=10). The bottom/top rate of the same specimen was calculated (n=10). The data were compared by Tukey's test in different tests (light energy transmission through the composite and bottom/top rate). Results The light energy transmission through the Filtek Z350 XT composite (HCM – 576 mW/cm2, LCM – 238 mW/cm2, SSM – 232 mW/cm2) did not show statistical difference when compared with Filtek P90 composite (HCM – 572 mW/cm2, LCM – 233 mW/cm2, SSM – 230 mW/cm2). The bottom/top rate of the Filtek Z350 XT composite (HCM – 88.98%, LCM – 90.94%, SSM – 89.92%) was statistically higher than that of the Filtek P90 composite (HCM–77.29%, LCM–77.51%, SSM– 77.79%). Conclusion Light energy transmission through the composite was not influenced by the use of different dental composite restoratives. However, the bottom/top rate of the composites was influenced by the use of different dental composite restoratives. Clinical significance Insufficiently polymerized composite resin may present a large number of problems. For this reason, dental composite resins should have the similar deep surface polymerization as the top surface in dental restorations. How to cite this article Guiraldo RD, Consani S, Consani RLX, de Camargo Bataglia MP, Fugolin APP, Berger SB, Lopes MB, Moura SK, Sinhoreti MAC. Evaluation of the Light Energy Transmission and Bottom/Top Rate in Silorane and Methacrylate-based Composites with Different Photoactivation Protocols. J Contemp Dent Pract 2011;12(5):361-367.