Tooth dentine. Coloured scanning electron micrograph SEM of a vertical fracture through the tooth of a domestic cat Felis catus. The bulk of a tooth is formed of dentine green, a mineralised tissue with a similar composition to bone. Within the dentine are channels called dental tubules brown, containing odontoblasts, cells which produce new dentine. The visible part of a tooth the crown consists of enamel_ covered dentine. Exposed dentine is sensitive to heat, cold and touch because it contains nerve endings.