Marginal bone level in the normal primary dentition

Abstract The aim of the present study was to establish the normal range for the radiographic distance between the cemento‐enamel junction (CEJ) and the marginal bone level (MBL) in the primary dentition, and to relate this distance to various physiological and pathological factors. 128 children at the ages 7, 8 and 9 years took part in the study. Clinical and radiographic examinations of the mesial and distal surfaces of all primary molars and the distal surface of the primary canines were performed. The clinical examination included measurements of the amounts of plaque, bleeding on probing, probing depth and probing attachment loss. In addition, increased mobility of the primary teeth and stage of eruption of the neighbouring permanent teeth were recorded. The radiographic examination included measurements of the CEJ‐MBL distance and the remaining root length. Also, exfoliating teeth, presence of proximal dentin caries, restorations and calculus were recorded from the radiographs. Associations between various explanatory variables and the CEJ‐MBL distance were tested with both a X 2 test and a variance components analysis. The mean CEJ‐MBL distance for all primary tooth surfaces was 1.0 mm. Individual surfaces displayed distances ranging from 0.0–0.4 mm. Of the variables tested for association with the CEJ‐MBL distance, eruption of neighbouring permanent tooth and exfoliation of neighbouring primary tooth seemed to be associated with large CEJ‐MBL distances. When surfaces with these characteristics were excluded, a CEJ‐MBL range of 0.0–2.0 mm was obtained. Based on these findings, it seems reasonable to consider sites with a distance of > 2 mm to have pathological bone loss, providing the above physiological conditions related to large CEJ‐MBL distances are taken into consideration.