Long story short, my original dentist (Dentist #1) sent me to the endo due to two infected tooth (both root canaled), one in my upper right and one in my lower left (#19). The endo said something about the infection spreading to the bones or something.

Last week, I had a root canal done on my upper right one with that endo. Today, I went to another general dentist (dentist #2) because my insurance annual maxed out with dentist #1.
When I asked dentist #2 them about #19 he said he doesn't see any infection and asked me if it ever hurt and I said no and he concluded that there's no infection there. wtf?

A. Could the endo + dentist#1 trying to pull a scam on me by forcing me to retreat root canals? or could they be mistaken?

B. Could the infection be temporary gone because of the antibiotics I've been taking? Been taking pennicilin after I did my UR root canal (It's been 6 days now I've been on the antibiotics, missed a few doses though)

Here are my xrays taken last thursday 7/2/2015, on the day I went in to do my root canal. I don't know which one is which tooth...
http://imgur.com/a/VdcgZ#0

Here's a pano from dentist #1 from 2 months ago
http://postimg.org/image/trh5pnu87/

The infection is clear in the pano but for some reason it doesnt show up well in the bitewings, why?