Final answer:
Maxillary first molars generally have four major cusps, but may have a fifth cusp known as the Cusp of Carabelli. The erection timeline for first molars is between 12-16 months.
Step-by-step explanation:
Maxillary first molars typically have three major cusps (mesiobuccal, distobuccal, and palatal) but often present with a fourth cusp, known as the Cusp of Carabelli, which is a variable trait. Including the Cusp of Carabelli, maxillary first molars may have a total of five cusps if we consider the smaller cusp-like structure that can form on the mesiolingual aspect of the tooth. However, in a standard description without variations, they are said to have four major lobes/cusps.
The eruption timeline for first molars, including the maxillary first molars, is between 12-16 months. This occurs well before the wisdom teeth, which emerge in early adulthood and are the third set of molars. If wisdom teeth fail to erupt, which is not uncommon, they are usually removed through orthodontic surgery.