The organization of microtubules within rat odontoblast processes revealed by perfusion fixation with glutaraldehyde

Abstract

Perfusion fixation of adult rat molar teeth via the ascending aorta with 1 per cent glutaraldehyde in Tyrode's solution produced well preserved odontoblast processes deep within fully mineralized dentine. The processes contained dense granules, mitochondria, an occasional multivesicular body, and a well developed network of microfilaments and microtubules. The microtubules were approximately 27 nm wide and several microns long. Bundles of microtubules coursed parallel to the cell membrane for the whole length of the odontoblast process. Structures interpreted as side arms or cross-bridges were observed between adjacent microtubules and filaments. The possible function of microtubules in odontoblast process elongation, structural support and saltatory transport of granules is discussed. The most distal parts of the dentinal tubules were either empty or occluded by collagen and amorphous material. It is suggested that dentinal tubules are not completely occupied by odontoblast processes but that a normal recession of the processes occur with or without a deposition of occluding substances.