Unusual forms of collagen in human dentin.

Unusual fibrillar and segmental forms of collagen have been documented in several tissues, including rodent dentin - but not human dentin, which was analyzed here for the presence of such structures. Of six normal human permanent and deciduous teeth examined, cusps of two deciduous molars displayed atypical formations, designated here symmetrical collagen segments (SCSs). They were detected inside of dentinal tubules. It was evident that the 264-nm long, cross-banded SCSs were occasionally arranged vertically and laterally in a staggered manner into thick, irregularly shaped aggregates. Two deciduous incisors from patients with dentinogenesis imperfecta associated with osteogenesis imperfecta were also studied. SCSs were not observed, but fibrous long-spacing-like collagen was rarely found intratubularly in one tooth.