I found the command
dbcc proc_cache(free_unused)
and all the space used by tempdb objects dropped...
DBName MemMB c
------------------------------ ----------- -----------
tempdb 135 4740
and we were left with
DBName MemMB c
------------------------------ ----------- -----------
tempdb 5 50
Does this imply unused objects aren't being cleared up ?
We don't close connection from our services very often - would this cause a problem.