The third molar (wisdom tooth) is the most frequently congenitally absent permanent tooth due to its evolutionary trend of reduction and variability in development. It often fails to develop because of limited space in the jaw and genetic factors influencing tooth agenesis. This absence can impact surgical planning, especially in extractions, implant placement, and orthodontic treatment. Recognizing third molar agenesis early helps avoid unnecessary interventions and informs decisions about space management.

Reference: Oral Pathology, Neville et al., 4th Edition.