The structure of Tomes' granular layer in dog premolar teeth

Microradiographic, polarized light, phase‐contrast and scanning electron microscopic aspects of Tomes' granular layer were studied in undemineralized and demineralized premolar teeth from four dogs. The microradiographic studies show Tomes' layer to consist of a narrow zone of hypomineralized‐hyperorganic dentinal matrix subjacent to the cementum. The zone appears as a series of focal points in cross sections or as an interrupted line in apico‐coronal cuts through the tooth. Polarized light and phase‐contrast microscopy demonstrate a morphological pattern similar to that of the microradiographs. Scanning electron microscopy suggests one component of Tomes' layer to be fibrillar. Tomes' granular layer of dog teeth may be important in protecting the tooth from sudden insults or large occlusal forces transferred to dentine via the periodontal ligament.