Silk is beautiful and so expensive in some countries, but it can deteriorate too, if seams are not wide enough. I actually bought a beautiful silk comforter made of saris from India, and it literally fell to pieces before I ever had it dry cleaned. Fortunately I was able to get my money back, but watching it pull into shreds was heartbreaking.
Remember too that old cloth and new cloth should not be put together or the "rend" will be greater. Keep the cloth about the same time period. This might require you to shop at a thrift store to finish your project. Depending on how old your dress is, it should be fairly easy to tell what is new and what is older by the style of the dress.
My best to you,
GramMER[u]