Is it necessary to take a human's wisdom teeth out?
Only if they are somehow bad, or you mouth hasen't enough room for them.
I feel fine with them but the dentist thinks I should take them out because they are hard to clean. Is that good enough reason to take them out?
You may be interested in reading an earlier biology thread on wisdom teeth.
You may want to ask another dentist for a 2nd opinion.
Must wisdom teeth come out? This reference points to 4 situations where they recommend having them removed:  when impacted,  if you are prone to pericoronitis (infection of the gum near a partially erupted wisdom tooth), if they are coming in the wrong position (making cleaning difficult) and  when they are opposite an already pulled wisdom tooth.
Note that one of these reasons does recommend pulling them when they are difficult to clean. If they cannot sufficiently clean off the plaque (bacteria), you will be more prone to http://www.mayoclinic.com/health/gingivitis/DS00363 [Broken].
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