[SEM investigations on the human sclerosed dentinal tubules]

Sclerotic changes of dentinal tubules appeared in the dentin beneath the carious, attrition and abrasion lesions and in the transparent root dentin were investigated using the scanning electron microscopy. 1) Shape of crystal-like substances appeared in the dentinal tubules could not be closely related to kinds of dentin destruction. 2) In the dentinal tubules beneath the carious lesions, cuboidal or rhomboid-shaped, short rod-like, long rod-like, plate-like and droplet-like crystals were mainly observed. Combination of cuboidal or rhomboid-shaped and short rod-like crystals or that of long rod-like and plate-like crystals were most frequently observed. 3) In the dentinal tubules beneath attrition and abrasion lesions, cuboidal or rhomboid-shaped, short rod-like and droplet-like crystals were mainly observed, however, the size of cuboidal or rhomboid-shaped crystal was usually smaller than that observed beneath carious lesion and they deposited compactly within the tubules. 4) In the sclerosed dentinal tubules in the transparent root dentin, compact deposition of rhomboid-shaped and irregular sand-like crystals were usually observed. Size of rhomboid-shaped crystal is smaller than that observed beneath carious lesion. The deposit of sand-like crystal in the tubules was easily discriminated from the matrix of peritubular dentin. 5) In any case, the kinds of crystals and pattern of deposition were not necessarily same between the neighboring tubules. However, in a tubule, they were almost same in shape and mode of deposition throughout the entire length of tubule from the outer side to the pulpal side. These facts seem to indicate that mineral deposition within the tubule due to sclerosis is performed under individual condition. 6) Finding showing biological control of mineral deposition within the dentinal tubules by the odontoblasts could not be observed.