Development and Histopathologic Features of Odontoclastic Resorption on the Internal Dentin Wall after Replantation of Rat Molars

人类牙列牙根吸收的病因、发病机制及预后仍有待进一步研究。目的建立大鼠磨牙模型，结合渗透泵在上颌第一磨牙近中根尖周区域局部输注化学制剂。选用雄性Sprague-Dawley大鼠，6周龄，200g b.w。全麻下手术时，用小牙棒（根尖切除术）除去内侧根的根尖端，在皮质骨上钻出一个直径约0.8mm的孔。泵载200 μL的药剂增溶溶液（或仅为对照）皮下植入剂量区，将套管置入磨牙区钻出的骨孔内（局部灌注）。在资助期内获得的结果证明，大鼠磨牙模型对研究牙本质内部吸收是有用的。再植磨牙的组织学检查显示，在再植后第7天左右，内牙本质壁上出现了更多的吸收腔隙并伴有trap阳性的多核细胞。吸收陷窝分为A型和B型，分别对应外根吸收的表面型和炎症型。牙本质内吸收发生的基本过程是肉芽组织的长入和巨噬细胞和成纤维基质细胞组成的新细胞群的聚集取代原有的牙髓组织。破牙细胞在牙本质壁上的初始附着并不一定需要OPN预处理，似乎是由其他识别机制介导的。本研究结果支持了大鼠磨牙天然牙髓对不良吸收活动具有有效抑制作用的假设，但在牙齿再植后天然牙髓环境受损后，一种新的细胞-基质和细胞-细胞相互作用模式可能共同作用，诱导牙本质内壁发生碎片活动。少

The etiology, pathogenesis and prognosis of internal root resorption in human dentition remain to be better understood. We aimed at establishing rat molar model combining an osmotic pump for local-infusion of chemical agents into the periapical region of the mesial root of upper first molars. Male Sprague-Dawley rats (6-wk-old, 200g b.w.) were used. At the surgical operation under general anesthesia, the apical end of the medial root was removed with the aid of a small dental bar (apicoectomy), leaving a drilled hole (around 0.8mm in diameter) through cortical bone. The pump loading 200 μL of an agent-solubilized solution (or vehicle only as control) was implanted subcutaneously on the dosal area and the cannula was placed into the drilled bony hole in the molar region (local-infusion). The results obtained during the funding period prove that rat molar model is useful for investigation of internal dentin resorption. Histologic examination of the replanted molars showed the occurrence … More of resorption lacunae accompanying TRAP-positive multinuclear cells on the internal dentin wall around day 7 after tooth replantation. Resorption lacunae were classified into A and B types, which appeared to correspond to surface and inflammatory types of external root resorption, respectively. The essential event responsible for the development of internal dentin resorption is the replacement of the innate pulp tissue with the ingrowth of granulation tissue and the assembly of a new cell population comprising macrophages and fibroblastic stromal cells. The initial attachment of odontoclasts to the predentin wall does not necessarily need preconditioning with OPN and appears to be mediated by alternative recognition mechanisms. The overal results support the hypothesis that the innate pulp of rat molars possesses in potency inhibitory functions against undesirable resorption activities, but after impairment of the innate pulp environment after tooth replantation, a new paradigm of cell-matrices and cell-cell interactions may act cooperatively to induce clastic acitivities on the internal predintin/dentin wall. Less