Elephant and mammoth tusk ivory comes from the two modified upper incisors of extant and extinct members of the order Proboscidea.
Labial frenectomy (of the lip) is very common with patients undergoing denture treatment in order to get the proper fit of dentures or patients who have tissues attached to centre of upper lip and causing recession of gums or gap between the upper front teeth called central incisors.
In elephants, the upper incisors are modified into curved tusks (unlike with Narwhals, where it is a canine that develops into a straight and twisted tusk).