Digression:
Details of how we did the searches (prior to combining using "OR")

Then we exploded the Subject Heading Temporomandibular Joint Disorders and included all subheadings:

We got these results:

Next we did our second search, for articles about the temporomandibular joint. We typed our term and checked "Map Term to Subject Heading"

This mapped to the Subject Heading Temporomandibular Joint:

We clicked the Subject Heading to see its Tree:

The Tree showed that there was also a more specific Subject Heading, Temporomandibular Joint Disc, below our Subject Heading. We were interested in this too, so we checked EXPLODE and clicked "Continue":

We then decided to include all subheadings:

This retrieved 1,877 results: