A 21-year-old patient has tooth #8 (maxillary right central incisor). Which developmental feature would be expected to be ABSENT in an adult tooth?

Mamelons are three rounded enamel prominences found on the incisal edge of newly erupted permanent incisor teeth. They are remnants of the three developmental lobes that form the incisor crown. In adults, mamelons are worn away by normal incisal attrition and occlusal contact, typically within the first few years after eruption. In a 21-year-old, mamelons would only be present if there was an open bite (preventing occlusal wear). Their absence in adults is normal. The lingual fossa, cingulum, and marginal ridges are permanent anatomical features that persist throughout life.