Comparative study of the initial genesis of acellular and cellular cementum in rat molars

Abstract

The initial genesis of acellular and cellular cementum was examined in rat molars by light and electron microscopy. Before root dentinogenesis, flattened dental follicle cells formed compartments by regularly arranged cellular processes which demarcated collagen fibril bundles oriented in parallel with the root long axis in both of the two kinds of cementum. After this stage, compartments disappeared from the dental follicle cells, which became elongated and polarized, with the cytoplasmic side facing toward the root surface in the acellular cementogenesis. Fibril bundles, oriented in parallel with the root long axis, decreased in number, and principal fibers appeared. Some principal fibers were attached on the first acellular cementum. Observations suggested that the fibril bundles, which had been oriented in parallel with the root long axis, were reoriented to merge into the principal fibers. In cellular cementogenesis, the dental follicle cells continued to hold the fibril bundles in cellular compartments. The regular processes were transformed into randomly oriented, finger-like processes. At the same time, fibers, which may be secreted from the finger-like processes, appeared around the preformed fibril bundles oriented in parallel with the root long axis. The different cellular behavior may result in the different fiber arrangement of acellular and cellular cementum.

Cellular cementogenesis in rat molars: the role of cementoblasts in the deposition of intrinsic matrix fibers of cementum proper

“…The finger-like processes contain microtubules and secretory granules as well as membrane-bound fibrils that are all arranged in parallel with the cementum surface. The initial stage has been described in previous studies (Lester 1969a, b;Yamamoto and Hinrichsen 1993;Yamamoto et al 1994). These findings suggest that cementoblasts are simultaneously secreting collagen fibrils in two different directions.…”

“…Cementocytes appear to secrete additional intrinsic fibers from the finger-like processes shortly after they have been enclosed Schroeder 1990, 1992;Yamamoto and Hinrichsen 1993;Yamamoto et al 1994). Simultaneously with the appearance of the first finger-like processes the arrangement of secretory granules changes to that for intrinsic fiber secretion.…”

Histological review of the human cellular cementum with special reference to an alternating lamellar pattern

“…10,11,[38][39][40][41] The fi rst type (not shown), which is found on the acellular extrinsic fi ber cementum, has plate-or wing-like processes and short fi nger-like processes. The fi nger-like processes extend from the ends of the wing-like processes and are arranged toward the cementum.…”

Molecular and cell biology of cementum

“…In contrast, cells expressing collagen are noted throughout the surrounding soft connective tissue, follicle cells and periodontal ligament fibroblasts (139,142). Bone sialoprotein messenger RNA and protein remain localized to the root surface in the mature tooth, while osteopontin protein is noted within the periodontal ligament region in the mature tooth (136,142,154,253). In addition to these adhesion molecules, laminin has been identified on the dentin surface at the initiation of cementum formation, where it has been speculated that this protein serves a role in attracting appropriate ''cementoblast-like'' cells to the root surface (145,146,235).…”

“…Commonly used animals for regenerative studies include rodents, canines, felines and nonhuman primates (78,122,185,190). Investigations focused on determining regulators of tooth/periodontal development often use rodents and follow molar and/or incisor development (5,29,56,96,135,140,143,187,192,232,236,237,240,253). In vitro models include cell cultures where cells are obtained from animal tissues and cells can be manipulated in various ways to mimic the in vivo environment, such as growing cells on or within selective matrices or using a variety of co-culture models (49, 69,117,132,168).…”