Root resorption of human deciduous teeth with apical periodontitis by cultured osteoclasts

Abstract

Roots of human deciduous teeth with apical periodontitis frequently show abnormal resorption as well as cementum deposition, and features that are different from those of physiological root resorption. The aim of this study was to determine the relationship between the appearance of cultured osteoclasts and the condition of dentin slices of human deciduous teeth. Bone marrow obtained from femora of 3- and 4-week-old male C57BL/6 mice was used for cell culture. The cells used in this study were osteoclasts, bone cells and bone marrow cells. Root dentin slices were prepared from human deciduous teeth with apical periodontitis (group 1) and from sound deciduous teeth (group 2, control group). The dentin surfaces were polished with grindstones. Cell suspension in α-MEM supplemented with 10% fetal bovine serum was seeded on the dentin slices and incubated for 96 hours at 37°C under 5% CO₂ in air. After incubation, specimens were removed and fixed with glutaraldehyde and paraformaldehyde, and then tartrate-resistant acid phosphatase (TRAP) activity, which is considered to be specific to osteoclasts and odontoclasts, was detected. The number of TRAP-positive cells on the dentin were calculated by light microscopic observation. Specimens were then prepared and observed under a scanning electron microscope (SEM). TRAP-positive cells, visible as small red dots, were observed on dentin slices of both groups (n = 50: each group). The densities of TRAP-positive cells in group 1 and group 2 were 2.98 ± 2.57 cells/mm² and 2.90 ± 2.22 cells/mm², respectively. The difference between densities of TRAP-positive cells in group 1 and group 2 was not significant by the Mann-Whitney U-test (P > 0.05). Shallow resorbed lacunae were observed on the specimens by scanning electron microscopy. It was shown that root dentin with apical periodontitis was resorbed by clastic cells such as cultured osteoclasts, suggesting that cell growth on dentin is not affected by apical periodontitis.