There is a risk for any implant to deflate, but this is very low. Silicone implants generally have a lower rate than saline. All manufacturers have warranties for deflation and contracture.
For silicone implants, there are two detection options: physical exam and MRI. When saline implants deflate, they physically shrink, making them much easy to detect visually. Saline implants will deflate much quicker and are absorbed by your body naturally and safely. Silicone implants can be detected with an MRI. Both types of implants are covered under warranty.