Performing scans do cause wear on the drives aswell almost everything does, but not as much defragging.
Scanners simply read the data from the drive and usually sequentially.
Defrag is moving the data around and not just in the file allocation table. So it has to read the data, then write the data in a new location, sometimes this is a temporary location at the end of the drive while other data is moved and then it gets read and rewritten again to it final resting place. Unlike scans there are lots of reads and writes and seeks some of which is duplicated.
Karlsnooks' recommendation of Ccleaner (I can see the blue link in his sig) is valid, it's one of the most popular cleaning tools on the net and is more thorough than disk cleanup. For its small install size it will normally free more space than it uses on it's first run. I use it. If you do use it I would avoid the registry scanner/defragger as it's not intelligent and will happily remove things that are needed.
It's not extreme or anything and depending on the TBF destiny of your drive the impact could be negligable.