A scanning electron microscopic study of the odontoblast process in human coronal dentine

It is generally accepted that the odontoblast process occupies the dentinal tubules only in the inner part of the dentine, extending approx 0.7 mm from the pulp in both animals and man. Twenty-three premolars, molars and third molars from subjects aged 11-24 yr, all caries-free or only slightly decayed, were processed immediately after extraction by one of four methods. (I) Teeth were split in liquid nitrogen and then fixed, dehydrated in ascending ethanol, and dried by critical point drying (CPD). (II) Teeth were fractured by use of a mallet and a chisel and then prepared as in Method I. (III) The root was cut off using a diamond disk or a mallet and a chisel and the crown was then fixed, fractured in liquid nitrogen, dehydrated and CPD. (IV) As Method III but following fixation the teeth were freeze-dried. All specimens were examined in the scanning electron microscope (SEM). In specimens prepared by Methods II, III or IV the odontoblast process was limited to the inner third of crown dentine. However in all the specimens prepared by Method I the odontoblast process extended to the dentine-enamel junction.