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My tiled shower needs to be repaired only where the walls meet the floor. While preparing for this by taking out the old grout, two small pieces of floor tile came out. Each piece that came loose is a corner piece (triangles - 2" x 2" by 2" - other tiles are 4" x 4"). Do I need to use thinset or can I use the same silicone I'll be using for the rest of the project?