Numerical density of dentinal tubules at the pulpal wall of human permanent premolars and third molars.

This study provides base line data on the density of dentinal tubules at the pulpal wall of permanent human premolars and third molars. A total of 125 healthy teeth removed for orthodontic (premolars) or other reasons (third molars) were used. After fixation the teeth were divided in the desired planes so as to obtain mesial/distal, vestibular/oral, and occlusal segments. The soft tissue was removed using 5% sodium hypochlorite (NaOCI) solution and the specimens were processed for scanning electron microscopy. Micrographs of standard magnification were taken from nine specific sites from the premolars and five from the third molars. The number of tubules present in an area representing 4000 microm2 was counted from each of the 780 micrographs, based on which the tubule density per mm2 for each tooth site was calculated. For the premolars the coronal dentin showed significantly higher tubule density than the radicular dentin. From the cementoenamel junction to mid-root level the average density of tubules declined by about one third to one half. At the level of the cementoenamel junction, the opposing mesial/distal and vestibular/oral sides showed a similar number of tubules per mm2. However, the number of tubules present on the vestibular/oral walls was significantly higher than those on the mesial/distal walls. The regional differences were less pronounced at the mid-root level of radicular dentin. For both the maxillary and mandibular third molars no significant regional difference in tubule density could be observed among the five sites examined. The mesial, distal, and occlusal walls of the mandibular third molar showed significantly greater tubule density than that of the respective walls of the maxillary third.