Re-examination of the morphology of caries susceptible grooves in the premolar and molar.

A period from 1890 to 1930's roughly corresponds to active investigations in the United States into grooves on the occlusal surface of the teeth by such men as BLACK [5], BODECKER [6-9], HYATT [12-20] and DIAMOND[11]. Our concept of the morphology of the occlusal grooves has been developed and fostered by these pioneering workers. The occlusal grooves are usually of twofold : one is what is termed by these scholars as the developmental groove and the other is supplemental groove which branches off from the former. The developmental groove is distributed between the cusps of a tooth or between the cusp and marginal ridge. While the supplemental groove is fairly difficult of the macroscopic observation because of its morphological shallowness, the developmental groove enables us to examine it with relative ease. Embryologically, the genesis of developmental groove is explained that it corresponds to a coalescence between the developmental lobes during the process of enamel formation. When this coalescence is normal, it will result in relatively shallow grooves, whereas an abnormal coalescence of some sort will produce deeply cut ones. The