The answer: Bone loss.

A common legend says that an astronaut who returned to Earth after an extended stay on a space station had bones so weak that he broke his arm lifting a tea cup. While this story may be an exaggeration, astronauts do lose bone density at a about ten times the rate of osteoporosis when in space (source) due to the absence of gravity.

What does gravity have to do with your bones? All the bones in your body get built up or broken down (resorbed) based on the amount of stress they're under. For most of the bones in your body, their major stressor is gravity. However, for the bones of your jaw, their stress comes from biting and chewing. But when someone loses their teeth, this stress goes away, which can lead to jawbone being resorbed by the body.

While dentures are an aesthetic and functional replacement for teeth, they apply biting and chewing pressure to your gums, instead of directly to your jawbone like a natural tooth does. Because the roots of natural teeth are embedded in your bone, so when you bite or chew something, that force is transferred through your tooth into the bone of your jaw.

This bone loss explains why you can get a new set of dentures that fit perfectly right after they've been manufactured, but as time goes on, they fit more and more poorly, until they are loose and uncomfortable. The dentures themselves have not changed, but the shape of the bone under your gums has.

For this reason, many believe there is no such thing as truly affordable dentures. Even the best, highest quality dentures will eventually need to be replaced due to the biological reality of bone resorption. However, it's important to note that bone loss in your jaw will happen even more rapidly if you don't replace your teeth with anything at all. If you're missing teeth, dentures can help you speak, eat and look normally again. Any dentures that allow you to get some of the normal function of your mouth back are affordable dentures!

For a permanent solution to bone loss after tooth loss, dental implants are the best option. That's because implants act as an artificial tooth root that transfers biting and chewing force directly into your jawbone, just like a natural tooth. Because your bone is still under stress from the implant, it won't be resorbed by your body.

While dental implants are more of a financial investment at first, they'll never have to be replaced like dentures, so you only have to pay for them once. Plus, they can be maintained just like real teeth, with daily brushing, flossing and semi-annual visits to the dental hygienist.

‍Dental implants have allowed for the invention of a new type of denture: the implant-supported denture. This type combines the affordability of dentures with the bone-stimulating qualities of implants to create a tooth replacement solution that is much more stable than traditional dentures that are held on with adhesives. This makes implant-supported dentures the most affordable dentures there are, both in terms of your wallet and your oral health!