Taurodontism is caused by a failure of which structure?

Taurodontism is a dental anomaly characterized by an enlarged pulp chamber and a short root system, resulting from the failure of the Hertwig's epithelial root sheath in its proper development. This sheath is crucial in determining the shape and length of roots during tooth development. When it does not function correctly, the roots do not form properly, leading to the characteristic features of taurodontism.

The other structures mentioned do not directly relate to the formation of the roots as the Hertwig's epithelial root sheath does. The dental pulp is found inside the tooth and is responsible for the tooth's sensory function and nourishment. The periodontal ligament serves the function of anchoring the tooth to the surrounding alveolar bone and does not influence root morphology. Ameloblasts are cells responsible for enamel formation and do not impact root structure. Thus, the influence of Hertwig's epithelial root sheath is pivotal in the context of taurodontism development.