Root malformation associated with a cervical mineralized diaphragm--a distinct form of tooth abnormality?

OBJECTIVE: Deviations in length and shape of tooth roots result from hard tissue resorption or occur as a developmental disorder. The purpose of this report is to present a type of root malformation which seems to have gone unreported so far. STUDY DESIGN: Two patients showing severely dysplastic roots of all permanent first molars were evaluated using radiography, histology as well as scanning and transmission electron microscopy. RESULTS: Medical histories of the patients revealed significant, but diverse events in the first year after birth. Radiographically the pulp cavity floors of the affected molars in large part were occupied by ectopic mineralized plates. Microscopically these plates consisted of hard tissue, densely calcified globules, and a network of canals which contained large blood vessels and were lined by cementum and periodontal ligament. CONCLUSIONS: We propose that the ectopic mineralized plate was derived from the dental follicle, had developed during crown formation around the vascular plexus at the base of the dental papilla, and represented a mechanical obstacle interfering with normal root development.