Which tooth usually has the longest root of all teeth?

The upper canine, also known as the maxillary canine, is characterized by having a particularly long and strong root compared to other teeth. This extended root length, which can reach up to 25 mm in some adults, provides stability and anchorage in the bone, making it essential for the support of the dental arch and functional effectiveness in biting and tearing food.

Canines in general are designed for holding and tearing, which necessitates a robust root structure. The upper canine's long root allows it to withstand the significant forces experienced during these actions. This anatomical feature distinguishes it from the other teeth listed, which generally have shorter roots or are not as pronounced in length as that of the upper canine.