Agenesis of maxillary permanent first molars: Literature review and two case reports

Congenital absence of teeth is the most commonly known developmental dental anomaly in humans. Agenesis of the permanent first molars has the least frequency of all the tooth types and when present, usually occurs in association with oligodontia or anodontia. Generally, it is easy to diagnose agenesis of the permanent first molars retrospectively, based on the clinical morphology and x-ray photographic features of the permanent second molars; while it is often debatable when made prospectively. Several hypotheses have been promulgated to explain the etiology of hypodontia with evolutionary and anatomic models. Nevertheless, clinical epidemiology does not completely support these hypotheses and therefore clinicians should be cautious; while speculating the missing tooth type based on these hypotheses. We encompass a comprehensive review of the literature on missing permanent first molars and illustrate two cases of missing maxillary permanent first molars to emphasize the complexity involved in their diagnosis.