Dentists, oral surgeons, and patients frequently ask me whether the lower wisdom teeth (third molars) can crowd their lower front teeth. Dental schools have long taught that they can based upon anecdotal evidence, but there is currently no conclusive scientific evidence that this is the case. As far as the scientific literature is concerned, valid reasons to remove the third molars (pericoronitis - inflamed gum tissue around the teeth, root resorption of the second molars, cysts) do not include prevention of crowding of the front teeth.
Which one of the patients below will have more of a tendency for their lower front teeth to crowd based upon the positions of their lower wisdom teeth as seen on the radiographs?
My answer would be, "I don't know." There simply hasn't been the research to conclusively determine if the wisdom teeth can directly cause the front teeth to crowd, even in cases where the third molars are completely horizontal, as in the top image.
For an excellent literature review on this subject, please read the article by Samir Bishara that appeared in the June 1999 American Journal of Orthodontics and Dentofacial Orthopedics.
To view the study "Mesial force from unerupted third molars" by Southard, Southard and Weeda click here. (This requires Adobe Reader). Note that none of the links in the article are active.