Tammy,
Brian is right about the risk of osteoradionecrosis. I had all my teeth removed prior to radiation treatments, so I know how your sister is feeling. She will not think so much about having teeth during her treatments. After radiation is over she will need time to heal, and during this period is when it got to me. When I began to feel better I wanted my teeth back. It was one year before they fitted me with a top denture and eighteen months before I got a bottom denture. Of course, no two people are the same and your sister may get them sooner. I just want you and your sister to know that it will happen and things will get better. It took me awhile to go out in public without teeth (fear of people looking at me), but I got over that and she will too. I'll be praying for you and your sister and if I can help in any way let me know. Anita