[1] The first permanent tooth usually appears in the mouth at around 5-6 years of age, and the mouth will then be in a transition time with both primary (or deciduous dentition) teeth and permanent teeth during the mixed dentition period until the last primary tooth is lost or shed.

Up to thirteen years of age, 28 of the 32 permanent teeth will appear.

This phenomenon is called hyperdontia and is often erroneously referred to as "a third set of teeth."

These teeth may erupt into the mouth or remain impacted in the bone.

[5] This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)