The regulation of fiber arrangement in advanced cellular cementogenesis of human teeth.

This study observed cellular cementum in fully formed human premolars by light and electron microscopy to elucidate how cementoblasts regulate the fiber arrangement in cementum. Cementoblasts had wing-like processes encircling the principal fibers, where Sharpey's fibers were dense. On the cementum-facing side, wing-like processes were segmented into finger-like processes in parallel with the cementum surface. Observations suggested that with the segmentation intrinsic fibers appeared around principal fibers in close association with finger-like processes. Where Sharpey's fibers were few or absent, where intrinsic fibers were the main fibrous element of the cementum, cementoblasts had only few or no wing-like processes, but had finger-like processes not associated with the wing-like processes on the cementum-facing side. On the basis of the origin of the finger-like processes the main results suggest that there are two kinds of cementoblasts: one has finger-like processes associated with wing-like processes and secretes intrinsic fibers from the finger-like processes to incorporate the principal fibers for tooth support. The second type has finger-like processes not associated with wing-like processes, this type secretes intrinsic fibers from the finger-like processes to adjust the cementum thickness.