Dynamic mechanical properties of poly(methyl methacrylate) (PMMA) reinforced with glass fibers were investigated. The composite used as dental base material contained other additives for different purposes to give the same appearance as natural dentals. The fiber-polymer bonding and orientation of fibers in polymer matrix are very important in the application of the product. To see that, the fibers were treated with silane and compared with untreated fibers. The commercial polymer and monomer used were the heat-cured type. However, in addition to heat curing, gamma-radiation was also used in curing. This gives much improved material in terms of mechanical properties. The voids, which cause mechanical failure in the material, will be minimal in number with irradiation curing. The results showed that the orientation of all fibers were not regular. This could be observed from the micrographs and DMA behaviors of samples. (C) 2002 Wiley Periodicals, Inc.