An ultrastructural survey of cat dentinal tubules.

The extent of the odontoblast process, the distribution of intratubular nerve-like structures, and tubule dimensions, have been measured in cat dentine. The odontoblast process varies in extent throughout the tooth. At most levels it is limited to inner dentine, extending further out only in the cervical region. This variation supports the view that the limited extent of the process occurs in vivo and is not an artefact of fixation. No nerve-like processes were found within dentinal tubules in this study, indicating the rarity of such structures. The tubules in the dentine of the cat are more variable in number but narrower than those of man and occupy a relatively smaller proportion of the volume of the tissue. Some factor other than tubule numbers and size must be responsible for the greater access which chemical stimuli seem to have to nerve terminals beneath cat, as opposed to human, dentine.