Tomazela-Herndl S A, Arana-Chavez V E
Laboratory of Mineralized Tissue Biology, Department of Histology and Embryology, Institute of Biomedical Sciences, University of São Paulo, 05508-900 São Paulo, Brazil.
Arch Oral Biol. 2001 Apr;46(4):305-11. doi: 10.1016/s0003-9969(00)00131-x.
There is no consensus on whether the first mineralized layer, the hyaline layer, that is juxtaposed to root dentine is a variety of dentine or cementum or even a tissue of epithelial origin. Some suggest that there is no intermediate tissue between the acellular extrinsic fibre cementum (AEFC) and the root dentine. Here, to study hyaline layer formation and mineralization we examined by transmission electron microscopy the early stages of root development in upper molars from 10 to 13 day old Wistar rats. In addition to conventionally processed material, undemineralized and unstained sections were examined, which showed the deposition of fine mineral crystals in contact with the mineralized surface of root dentine. Early mineralization of the hyaline layer occurred in the region of the inner basement membrane, which persisted between the inner cellular layer of Hertwig's epithelial root sheath and the outer mineralized root dentine. When the root sheath began its fragment, collagen fibrils from the developing periodontal ligament began to insert into the mineralising hyaline layer, which was 0.5-0.8 micron wide. As the fragmentation of the root sheath HERS increased, more collagen fibrils appeared intermingled with the mineralising hyaline layer. In more advanced stages, when the hyaline layer had become fully mineralized and the formation of the AEFC began, the hyaline layer could no longer be identified. Thus, the hyaline layer is clearly discernible at early stages of periodontal development. Subsequently, it is masked by intermingling of cementum and dentine and therefore it is not possible to detect it in the formed roots of rat molars.
与牙根牙本质相邻的第一个矿化层即透明层，究竟是牙本质的一种变体、牙骨质，甚至是上皮来源的组织，目前尚无定论。一些人认为，无细胞外源性纤维牙骨质（AEFC）与牙根牙本质之间不存在中间组织。在此，为了研究透明层的形成和矿化，我们通过透射电子显微镜检查了10至13日龄Wistar大鼠上颌磨牙牙根发育的早期阶段。除了常规处理的材料外，还检查了未脱矿和未染色的切片，这些切片显示了与牙根牙本质矿化表面接触的细小矿物晶体的沉积。透明层的早期矿化发生在内基底膜区域，该区域在赫特维希上皮根鞘的内细胞层和外部矿化的牙根牙本质之间持续存在。当根鞘开始断裂时，来自发育中的牙周韧带的胶原纤维开始插入正在矿化的透明层，该透明层宽0.5-0.8微米。随着根鞘HERS的断裂增加，更多的胶原纤维与正在矿化的透明层混合出现。在更晚期阶段，当透明层完全矿化且AEFC开始形成时，透明层就不再能被识别。因此，透明层在牙周发育的早期阶段清晰可辨。随后，它被牙骨质和牙本质的混合所掩盖，因此在大鼠磨牙的已形成牙根中无法检测到它。
