Tooth development involves reciprocal interactions between oral epithelium and mesenchyme, and is achieved through complex regulatory networks. Abnormal spatiotemporal expression of the molecules involved in regulating tooth development may lead to abnormities of tooth development initiation and successional tooth replacement, which in turn affect the number of teeth,resulting in tooth agenesis and hyperplasia. In addition to using traditional mouse models, in recent years, animals such as miniature pigs, monkeys, and ferrets have been increasingly used in tooth development research. Here, we summarize tooth development models and molecular regulatory networks of vertebrate successional teeth to systematically understand the causes of abnormalities of the tooth number in humans.