Although exfoliation of primary teeth and the subsequent eruption of the permanent successors usually occur in a systematic fashion, there are numerous conditions that can impact this developmental process. These conditions can be broadly grouped into the following categories: The mechanisms through which these conditions affect tooth exfoliation/eruption are diverse, and the diagnosis and management can be quite challenging for the oral healthcare provider. These factors and conditions will be examined and information provided on clinical presentation and treatment options. Finally, where possible, each hereditary condition is identified by its OMIM number so that the reader can easily obtain additional information.