So say someone has an open sore in there mouth and there affected by job and you eat off the same spoon as them can you get it?

Usually not. I guess it would depend on what is causing the open sore. In general, diseases are not usually transmitted by sharing spoon with someone who has a sore in the mouth. On the other hand, there are a few infectious diseases which can be transmitted through saliva in the absence of any open sores.