Why Wisdom Teeth Cause So Much Trouble

Wisdom teeth generate more extractions than any other tooth. The reason is a mismatch between the size of the modern jaw and the number of teeth it is asked to hold.

They arrive last, into whatever space remains

Third molars erupt in late adolescence or early adulthood, long after every other tooth has established its position.

Whatever space is left at the back of the jaw is what they get, and if it is insufficient the tooth cannot come through into a normal position.

Jaw dimensions have changed over human history, plausibly linked to softer diets requiring less chewing force during growth, while tooth number has not changed with them.

Partial eruption is the actual problem

A tooth fully erupted or fully buried tends to cause little difficulty. The trouble comes from the intermediate state, where part of the crown breaks through and part stays covered.

The flap of gum over a partially erupted tooth creates a space that cannot be cleaned, since neither brush nor saliva flow reaches underneath it.

Bacteria accumulate there and produce recurrent infection of the overlying tissue, which is the most common reason a wisdom tooth becomes symptomatic.

The neighbouring tooth is often the casualty

An impacted third molar frequently sits at an angle, pressing against the second molar in front of it.

The contact point between them is impossible to clean, and decay commonly develops on the back surface of the second molar rather than on the wisdom tooth.

That surface is also difficult to restore, which is why the healthy neighbour is sometimes the reason an asymptomatic wisdom tooth is removed.

Removal is a genuine surgical decision

Lower third molars sit close to a nerve supplying sensation to the lip and chin, and their roots can be intimately related to it.

Imaging is used to assess that relationship beforehand, and where the risk is significant, alternative approaches may be preferred to complete removal.

Upper third molars sit near the sinus, which raises a different set of considerations, so the two are not equivalent procedures despite being discussed together.

Routine removal has fallen out of favour

Extracting all wisdom teeth as a matter of course was once common and has been substantially curtailed on the evidence.

Many impacted teeth never cause a problem, and removing them exposes people to surgical risk for no benefit.

Current practice generally reserves removal for teeth causing symptoms or damage, which makes it a judgement about a specific tooth that only a dentist examining it can make.