Force Time Machine to perform a deep traversal?
Deleting the .fseventsd directory on the backup drive would be one way to do it.

However in my experience there have been a few times where Time Machine did a full traversal, estimated that it would have to back up the entire drive, and then proceeded to 
 check everything but only back up files that were different. For example, this happened after upgrading from 10.7 to 10.8. The size of the new backup was much less than it first estimated.