Most of the people using Ubuntu or Mint will be using Synaptic Package Manager or Ubuntu Software Center to manage the applications installed on their systems (the former because of its light interface and ability to queue a whole lot of actions, the latter because of the user friendly interface). But while the two do an excellent job at installing, neither of them copes perfectly with removing the packages afterwards (USC does improve on that matter, but is still leaves traces in some situations).
The thing to use here is a simple command line utility to remove unneeded dependencies. Open a terminal and enter:
sudo apt-get autoremove
For more information, enter