The third set of molars are often called “wisdom teeth” because they developed around what used to be called “the age of wisdom”, which is around 18. They have absolutely nothing to do with intelligence. In fact, quite the opposite. Most wisdom teeth can’t even figure out how to erupt through the gums crown first!
There have been many theories and myths about why wisdom teeth should be extracted or left in place. Many dentists used to encourage leaving wisdom teeth in place if they erupt fully, even if they come in crooked, as they could make a good support tooth for a bridge of the second molar would be lost for some reason. In reality, though, wisdom teeth make poor abutment teeth because their root structures are weak and unpredictable. One of the theories that was used to justify extraction claimed that wisdom teeth “pushed” teeth forward, causing the front teeth to crowd. Good research has proven time and time again that wisdom tooth impaction and/or eruption has absolutely no effect on the lower front teeth.
So, what do we know? We know that wisdom teeth are so far back in the mouth that they are almost impossible to clean with normal hygiene practices. Therefore, wisdom teeth are very susceptible to dental decay, especially later in life when dexterity may be compromised by arthritis, etc. Impacted wisdom teeth have the potential to cause cysts which can weaken the jaw bone and cause damage to the adjacent second molars. Partially impacted teeth, which poke through the gum, can become infected and cause damage to the gums and bone surrounding the adjacent teeth. Sometimes, severe infections can result.
I personally do not know of any logical reason for not having third molars removed at a young age, unless there is some underlying medical reason that would complicate the extraction surgery. The risks of keeping wisdom teeth usually far outweigh the benefits of taking them out. The younger a person is when the procedure is done, the less risk is involved and better healing potential exists. Once the roots are completely formed, surgery becomes more complicated in many cases.