Histomorphometric analysis of primary teeth during the process of resorption and shedding.

The state of pulp tissue and periodontal root surface of 90 non-carious human primary teeth during the process of resorption and shedding was assessed by histomorphometric means. The teeth were classified into preshedding, shedding and delayed-shedding groups according to age of the child at the time of extraction. The root surface length measured from the cementoenamel junction was related to stages of shedding. Inflammatory cells in the pulp tissue were observed in all three groups (p less than 0.005). Odontoclasts in the pulp tissue could be demonstrated in the shedding and delayed-shedding stages (p less than 0.05). Polymorphonuclear leukocytes and odontoclasts were not observed before resorption had occurred approximately 1 mm subjacent to the cementoenamel junction. Active resorption of the periodontal root surface was observed in all stages. Deposition of cementum-like tissue in resorption lacunae on the root surface was most pronounced in the delayed-shedding stage showing repair in 30% of resorbing root surface length. Findings indicate that the process of resorption occurs mainly during the shedding stage and repair tends to accelerate in the delayed-shedding stage. The predentin appears to have more power of resistance than any other part of the tooth and there is no reason to believe that the pulp participates in the process of resorption of human primary teeth under physiologic conditions.