Immediately after replantation, a coagulum is found between the two parts of the severed PDL. The line of separation is most often situated in the middle of the PDL.
Proliferation of connective tissue cells soon occurs, and after 3 to 4 days, the gap in the periodontal ligament is obliterated by young connective tissue. After two weeks the separation line in the periodontal ligament is healed and collagen fibers are seen extending from cemental surface to alveolar bone (Andreasen JO, 1994).
4.2.1 Early events
A day after replantation coronal periodontal ligament and transseptal fiber show severe disruption. (Error! Reference source not found.) There is marked acellularity with exception of a few remaining scattered cells with mitotic nuclei, and a localized collection of polymorhonuclear leukocytes. There is a distinct corono-apical break in the fibril continuity, located approximately 40-90à from the root surface (Proye et al, 1982). The torn periodontal fibers are connected by fibrous blood clot infiltrated by erythrocytes and polymorhonuclear leukocytes (PMN). Epithelial coverage is well adapted to the tooth. In the area of interface that is the contact surface between the replanted tissues and the recipient bed there was no sign of activity on either side. The fibers loose their individuality and show some degree of hyaline degeneration. Bone marrow shows increased activity. But the cementoblasts are absent along the replanted root (Nasjleti et al, 1975). Neutrophils are present through out the wound space this time. Increasing number of neutrophils migrate towards the tooth surface.
Degradation of erythrocytes begins (Wikesjo et al, 1992).
Around the third day areas of cell repopulation appear in the fibers, these repopulation from the connective tissue overlying the crest of the alveolar bone. The area adjacent to the root surface show less cellularity as compared to the transeptal fiber region.
Viable cells are present in clusters adjacent to opening from the marrow spaces or in proximity to blood vessels. Osteoclasts differentiate in the marrow spaces adjacent to the acellular periodontal ligament triggering rear resorption. The distinct break in the continuity between fibers attached to the root surface and those of the transeptal and periodontal ligament are still apparent (Proye et al, 1982). Basal-cell layer of the epithelium shows the greatest activity around the replanted tooth. In the middle third of the periodontal membrane it is possible to differentiate areas with diverse reaction, this reaction being more marked on the side related to the bone. Bone marrow spaces show increased activity of the connective tissue cells but no bone resorption can be seen (Nasjleti et al, 1975). Osteoblasts are
4, Avulsion
present on the ligament surface of the alveolar bone adjacent to the margin of the bone.
Occasional osteocytes are also seen in this location. Cementoblasts are seen adjacent to the cementum (Gould et al, 1980). Inflammatory reaction moves in to its late phase, the neutrophils infiltrate gradually decreases while the influx of macrophages increases.
Macrophages contributes to wound debridement by removing effete blood cells, neutrophils, and residual tissue debris and , in addition , has a conspicuous role including release of growth factors which support fibroblast proliferation and matrix production, smooth muscle cell proliferation, and endothelial cell proliferation and angiogenesis. The macrophage, therefore, plays a key role in the transition (Wikesjo et al, 1992).
4.2.2 Late events
Around seven day post replantation periodontal ligament is characterized by localized areas of acellularity and lack of fiber continuity. Vascular and cellular connective tissue is present in the ligament adjacent to opening from the marrow spaces. Several multinucleated cells are distributed along the break in fiber continuity. Osteoclasts line the marrow spaces and osseous walls of the channels connecting the marrow spaces with the periodontal ligament (Proye et al, 1982). Reorganization of the wounded periodontal ligament is under way. All the three cell types- fibroblast, osteoblast and cementoblasts are seen (Gould et al, 1980). The epithelium is reattached to the reimplanted tooth at the cementoenamel junction and regains normality. The connective tissue cells, fibroblasts and angioblasts, reach its peak. The interface becomes indistinct. Bone marrow shows areas of increased activity. Isolated areas of bone and cemental resorption are seen (Nasjleti et al 1975). The phase of granulation tissue formation gradually enters into the third phase of wound healing in which the newly formed cell-rich tissue undergoes maturation and
Around day two to three weeks after replantation the periodontal ligament is cellular but lacks normal morphology. Fiber continuity and orientation is reestablished in localized area, in other regions fibers ran parallel to the root surface. Root resorption, involving cementum and dentin is evident at this stage. The extent varies, with some areas of the resorbed surface showing deposition of osteoid or presence of multinucleated cells. Marrow spaces appeared larger than those present on 7th day but the osteoclasts are less frequent (Proye et al, 1982). Supracrestal connective tissue fibers are restored and show attachment to root Cementum. Cementoblasts are still absent. Bone marrow shows isolated areas of increased activity mainly localized to spots of cemental and bone resorption or to bone formation that led to ankylosis. No evidence of bone or cemental resorption is seen.
Ankylosis is absent cementoblasts are present along the replanted root after 28 days (Nasjleti et al, 1975).