On PubMed, is there a way to see the non-overlap of articles retrieved by two separate searches?
If I am understanding what you need to do correctly, you can accomplish your task on the Advanced Search page using the set numbers for the search statements and the Boolean operator NOT. I always have to talk to myself when I do this search and say: I want to see the items that are in #2 that are not in #1. Here is an example. Let me know if you have questions.
#3 Search #2 NOT #1 9098
#2 Search periodontal disease/diagnosis[mesh] 16525
#1 Search periodontal disease/diagnosis[major] 7427