Why would I need a bone graft before getting dentures because of my sinus? This question was recently asked by one of my patients, and is a somewhat common occurrence with denture wearers. There are a couple reasons why you would need a bone graft before getting dentures because of your sinuses, and I'll go through what the reasons are and give you a general overview of the treatment process. What are your sinuses, and what happens to them as we age? What procedures can your dentist do to bring your sinuses back to their normal positions?