Dental bridges- 3, 4, 5?

On Monday I am supposed to have a procedure done- basically a dental bridge. My dentist told me I would need to have a five-unit bridge done. The teeth that are missing are #6 and #4 on the right side. This decision was made by the dentists, and frankly, insurance came into play. I cannot afford implants, though I have researched extensively and the general consensus is implants, we came to the conclusion that bridge work will be done. My question is- why a 5 unit bridge? Why not 4 or even 3? is there a significant difference, in terms of placement? I haven't had time to discuss this with the dentist, but I'd like to go armed with information. Any help will be greatly appreciated. Professional responses would be awesome. Thanks!
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The best support for a bridge is for it to be balanced on both side by solid teeth/roots. That's why your dentist wants to do a 5 unit bridge and include #7. What you are asking for by not including #7 is a cantilever. This is done in very very limited cases, and even then, not many dentists will do it because of stress risks to th teeth involved. Too much stress on a tooth in the wrong directions can cause a root of a tooth to fracture. So while I understand you don't want to shave a healthy tooth, you would be risking #3 and #5 by not including #7. If you really don't want to shave #7 and think implants may be a possibility for you in the future, consider a partial denture as a temporary solution and save up for implants. Think of support on a bridge over water. It is held by solid ground on both sides. If you have it held by only one side and someone stands on the opposite side, forces are pulling the ground on the side that is holding it up and sideways, that side of the cliff will collapse.
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