This is probably one of those questions only my oral surgeon can
answer, but I'd appreciate any discussion of this, here.

I am in the process of planning for more implant surgery, for #2 and
#4, with a crown bridged in between these 2. They are also saying I
need a sinus lift (lateral , crestal) for these implants.

My questions are:
Do I really need an implant at #2? That's pretty far back, and I was
told before, that for example, #18 is not really necessary in most
cases, because it's so far back. In my case they DID do #18 but I'm
not sure it was necessary.

Is #2 really necessary? I almost feel like, to save money, I could get
by with just doing #4 and not getting #2 or a bridged crown in between
#2 and #4. How much do I really need #2 and #3?

Also, since I need a sinus lift, is it POSSIBLE that maybe if I just
got #4, and not #2 implant, then I might not need a sinus lift at all?

IF I do HAVE to get the sinus lift in order to get any of these teeth
implanted, then I may as well get at least 2 implants there. But if I
could avoid the sinus lift, I think I would be happy to do that and
just get one implant (#4).

Also, are these bridges , where you have 2 implants and just a crown
in between, as "bad" (i.e. hard to keep clean and uncomfortable) as a
regular "bridge"? If so, I am sure I'd much rather get just #4, or
just #3 and #4, and no bridge between 2 and 4...

I will discuss this with my oral surgeon and his professor, but I
would appreciate any feedback, here on my questions. Thanks.