Taurodontism is defined as the enlargement of pulp chambers with the furcation area being displaced toward the apex of the root. It cannot be diagnosed clinically and requires radiographic visualization since the crown of a taurodontic tooth appears normal and its distinguishing features are present below the alveolar margin. Taurodontism can present in deciduous or permanent dentition, unilaterally or bilaterally, but is most common in the permanent molar teeth of humans. The underlying mechanism of taurodontism is the failure or late invagination of Hertwigs epithelial root sheath, which leads an apical shift of the root furcation. Classification
The term was coined by Sir Arthur Keith. It comes from the Latin taurus meaning "bull" and the Greek ὀδούς (odous), genitive singular ὀδόντος (odontos) meaning "tooth", to indicate the similarity of these teeth to those of hoofed/ungulates, or cud-chewing animals.Radiographic characteristics of taurodontism include:

lack of pulp chamber constriction at the cementoenamel junction (CEJ);
an enlarged pulp chamber that appears rectangular in shape; and
displacement of the pulp chamber floor toward the root apex, shortening the roots and root canals.Earlier classification systems considered only the apical displacement of the pulp chamber floor; whereas, later systems additionally consider the position of the pulp chamber in relation to the cemento-enamel junction and alveolar margin. Shaw 1928
One of the first attempts to classify taurodontism was made by C.J.Shaw. He used the apical displacement of the pulp chamber floor to classify taurodontism into four distinct categories: cynodont (normal), hypotaurodont, hypertaurodont, and mesotaurodont.
A median mandibular cyst is a type of cyst that occurs in the midline of the mandible, thought to be created by proliferation and cystic degeneration of resting epithelial tissue that is left trapped within the substance of the bone during embryologic fusion of the two halves of the mandible, along the plane of fusion later termed the symphysis menti. A true median mandibular cyst would therefore be classified as a non-odontogenic, fissural cyst. The existence of this lesion as a unique clinical entity is controversial, and some reported cases may have represented misdiagnosed odontogenic cysts,  which are by far the most common type of intrabony cyst occurring in the jaws. It has also been suggested that the mandible develops as a bilobed proliferation of mesenchyme connected with a central isthmus. Therefore, it is unlikely that epithelial tissue would become trapped as there is no ectoderm separating the lobes in the first instance. == References ==