A novel type of developmental dentin defect

We describe a developmental dentin disorder distinct from dentin defects characterized thus far. The proband was a 9-year-old boy who was the only family member known to be affected in five generations. The dental defect was not associated with any general disease or developmental disorder. The teeth appeared normal with the exception of the pink hue seen in some primary teeth. Radiographs showed pathological resorption of primary teeth and abnormally shaped pulp chambers and denticles in permanent teeth. Root canals were wide in developing teeth, but appeared thin in erupted teeth. Histological examination of two primary molars revealed canal-like defects in dentin. In the crown, the canals appeared as clusters, which alternated with columns of normal tubular dentin, and in the virtually atubular root dentin they were haphazardly distributed. Scanning electron microscopic examination confirmed the distribution pattern of the canals. In transmission electron microscopy, the defects were found to contain symmetrically banded, segmental collagenous structures. The canal contents immunostained with antibodies to the N-terminal propeptide of type I procollagen, suggesting retention of the propeptide extension in type I collagen. Whereas type III collagen reactivity was barely detectable in the canal region, staining for type V collagen and the non-fibril-forming type VI collagen was strong. The findings imply that the pathogenesis of the defect could be related to a local failure of odontoblasts to produce normal dentin matrix.