Nucleoli of human odontoblasts

Progressive changes in the pulpo-dentinal complex and their clinical consequences

With changes in the age structure and oral health in the population, changes in the pulpo-dentinal complex are becoming more relevant clinically. Age-related changes in the structure of dentine and pulp are reviewed. The influence of these changes on restorative dentistry are considered with particular emphasis on endodontics and the use of adhesive restorative materials.

Quantitative histological analysis of the human coronal dentine in dentinogenesis imperfecta types I and II

The coronal dentine of 3 teeth from dentinogenesis imperfecta (DI) type I, 9 teeth from DI type II and 4 controls were examined by a quantitative histological technique. In each case, two representative demineralized sections, one stained in H + E and the other in Schmorl's picrothionin were used. The relative amount of dentinal tubule, atubular dentine and canals/clefts were assessed using the point-counting method. Three basic patterns of distribution of tubules were observed. Pattern 1 formed the largest group and showed a gradual decrease in tubule count from enamel-dentine junction (EDJ) pulpwards, pattern 2 was characterized by a drop in tubule count approximately midway between EDJ and pulpal border, and pattern 3 exhibited a gradual increase in tubule score as the pulp was approached. At the 5 per cent level, both patterns 1 and 2 were found to be statistically significant. Pattern 3 was statistically insignificant for the test specimens and highly significant for the controls. The variation in the distribution of the tubules in coronal dentine in this study indirectly supports the concept of abnormal dentinogenesis in DI attributable to a diminution or lack of normal functional odontoblasts.

Morphometric analysis of the nucleolus during the life cycle of human odontoblasts

Developing first premolars were used as a model system to obtain information on the nucleolar structure of human odontoblasts at several stages of their life cycle. Four stages were defined by their location within the tooth: a) preodontoblasts were located at the growing tip of the root; b) secretory odontoblasts in the apical region; c) transitional odontoblasts in the middle region; and d) aged odontoblasts in the coronal region. Preodontoblasts have a small nucleolus (0.55 micron 2) with few strands of dense fibrillar material radiating from the fibrillar center. Secretory odontoblasts are characterized by a large (1.24 micron 2), irregular, and reticulated nucleolus. The fibrillogranular material, the largest component in all nucleoli, reaches maximal size at this stage (0.88 micron 2). Fibrillar centers occupy about the same area (0.1 micron 2) throughout the odontoblast's life cycle. As the formation of primary dentin is completed, the nucleolus of transitional odontoblasts is reduced in size (0.54 micron 2). Finally, the aged odontoblasts have a small, compact nucleolus (0.39 micron 2), with segregated components. Morphologic analysis and quantification of size and component areas of nucleoli obtained with an image analyzer indicated that secretory odontoblasts had the most active, and aged odontoblasts the least active, nucleolus.