A Light Microscopic Study of Odontoblastic and Non-odontoblastic Cells Involved in Tertiary Dentinogenesis in Well-defined Cavitated Carious Lesions

This study examines cellular and microradiographic findings in thin, undemineralized sections of 46 cavitated lesions, that were clinically well-defined with respect to lesion activity and estimated lesion age at extraction time. The progressive stages of surface breakdown ranged from enamel cavitation to larger dentine exposures classified as closed and open lesion environments. Measurements of the following parameters were performed using computerized image processing software: (a) the cytoplasm:nucleus ratio of primary odontoblast cells; (b) the cell:dentinal tubule ratio; (c) the adjacent predentine area (mum2), and (d) the cytoplasm: nucleus ratio of non-odontoblastic cells, and secondary odontoblast-like cells, where estimation of these cell types were based on structural criteria. In active enamel cavitated lesions, reduced odontoblast-predentine regions and indistinct subodontoblastic regions were noted. During initial dentine exposures, non-odontoblastic cells along the pulp-dentinal interface were observed as well. The first indication of tertiary dentine was seen in old lesions with exposed dentine. The tertiary dentine appeared more atubular in the closed/active lesions than in the open/slow-progressing lesions. The involved odontoblastic cells in tubular tertiary dentine in small open/slow-progressing lesions were comparable to the primary odontoblast cells, however, new dentinal tubules were also noted presenting a mixture between reactionary and reparative dentinogenesis. In close/active lesions non-primary odontoblastic cells were aligning the atubular tertiary dentine, whereas well-defined signs of secondary odontoblast-like cells were first seen in larger open lesions, producing tubular tertiary dentine. In conclusion, a strong relationship between external lesion environments and corresponding different formations of tertiary dentine was noted in advanced cavitated lesions. It is additionally suggested that the stimulation of tubular tertiary dentine could be a closely related reaction when an active lesion complex changes into a slower progressing lesion environment.