Breast implants can be used to add volume to small breasts, fill up a deflated skin envelope after pregnancy or weight loss, and create a new breast mound after mastectomy for breast cancer. All implants are imperfect devices and will likely need to be replaced at least once in your lifetime. Saline implants are a bit firmer and heavier than silicone ones. If a saline implant deflates, however, it is usually obvious and a short surgery can be done to remove and replace it. Silicone implants can provide a more natural look and feel. However, a rupture is harder to detect, and the surgery to remove and replace it can be more involved.