Occlusal forces promote periodontal healing of transplanted teeth with enhanced nitric oxide synthesis

It has been reported that occlusal forces promote periodontal healing of transplanted teeth and prevent dentoalveolar ankylosis, although its mechanism is still unclear. Nitric oxide (NO) produced by NO synthase (NOS) is considered to be an important factor which is involved in wound healing, and it increases with mechanical stimuli. The objective of this study was to examine the relationship among occlusal stimuli, inducible NOS (iNOS) and PDL healing of transplanted teeth. Five-week-old Sprague-Dawley male rats were used for this study. The right maxillary first molars of rats were replanted and animals were divided into occluded and non-occluded groups. Histologic observations were carried out after one and two weeks. After two weeks, the non-occluded group had clearly detectable ankylosis and obvious PDL stricture. On the other hand, the occluded group showed an enlarged and thickened PDL without ankylosis. The number of iNOS positive cells in the occluded group, samples significantly increased in comparison to that of the non-occluded group. These results suggest that occlusal stimuli enhanced the production of NO in the PDL healing process of transplanted teeth and a favorable result could be obtained.     

Root and Bone Response to the Proximity of a Mini-Implant under Orthodontic Loading

Objective:To determine the histological reaction of the root and bone as a mini-implant approaches the root.Materials and Methods:Two kinds of mini-implants were inserted into the buccal alveolar bone of 4 beagles (2 males and 2 females). The specimens were classified as the near-root group, the PDL contact group, the root contact group, and the root perforation group. Cementum resorption, dentin resorption, cementum repair, cementum growth, ankylosis, root cracking, and root fracture were assessed as the implant neared the root.Results:The incidence of root resorption increased when the mini-implant was less than 0.6 mm from the root in the near-root group and PDL contact group. Root cracking and root fracture occurred in the root contact group and root perforation group. Bone resorption and ankylosis were observed in some specimens. However, some specimens of the PDL contact group and root contact group had cementum growth or little root resorption despite proximity to the root. In the root perforation group, root resorption and ankylosis occurred on the side opposite the insertion.Conclusions:There is a risk of root contact and severe tissue damage from a thick mini-implant and the drilling procedure, either of which can induce root resorption or ankylosis. Use of smaller mini-implants may reduce root contact and tissue damage. However, the small mini-implant may need enhancement of its stability.     

Extraoral endodontic treatment by retrograde insertion of posts: a long-term study on replanted and transplanted teeth

OBJECTIVE: The aim of the study was to investigate the healing results of teeth replanted or transplanted in different indications and treated by extraoral root canal therapy. STUDY DESIGN: Extraoral root canal treatment was performed from a retrograde direction with posts made of ceramics or titanium. Preoperatively, the pulp status was classified as definitely infected (n = 47) or not infected/symptomless (n = 78), and the condition of the periodontal ligament (PDL) was classified as damaged (n = 50) or not damaged (n = 75) according to trauma type and extraoral storage. The healing after replantation or transplantation was diagnosed as functional, ankylosis, or infection depending on clinical and radiographic findings. RESULTS: In total, 125 teeth in 99 patients were replanted or transplanted. Mean observation period was 44.4 months. Teeth with a less damaged PDL in no case exhibited ankylosis/replacement resorption after a mean observation period of 53 months. Teeth without preoperative infection of the pulp in no case showed infection-related complications after a mean observation period of 30 months. Teeth classified as definitely infected before treatment had a high frequency of continuous periradicular bone and root resorption. CONCLUSIONS: The extraoral insertion of posts appeared to inflict no additional damage to the PDL that was clinically relevant. Infection-related complications were prevented. Teeth that were classified as definitely infected at the time of treatment had a low rate of healing and should undergo conventional root canal disinfection before this surgical procedure is applied.     

Healing following devitalization of sites within the periodontal ligament by ultralow temperatures

Healing of specific rat periodontal ligament (PDL) sites following freezing injury was monitored histologically to evaluate repair potentials of this tissue. Buccal alveolar plates supporting the first mandibular molar in 15 adult rats were surgically exposed. The coronal 3 mm of plate covering the buccal surface of the mesiobuccal root and underlying periodontal ligament and cementum were subjected to ultralow temperature using a gas expansion micro/cryoprobe, diameter 2 mm, cooled to -81 degrees C for 5 seconds. Tissues were repositioned and sutured in layers. Animals were sacrificed at 1, 24 and 72 hours and at 2, 5 and 7 weeks following surgery and mandibles removed for histologic analysis. Microscopic evaluation of 24-hour specimens showed loss of cellular vitality in the PDL, adjacent bone and cementum at experimental sites. Cellularity of the gingiva coronal to the crest, and of the PDL apical to the experimental zone, appeared to be within normal limits. Transition between experimental and nonexperimental sites was abrupt. After 72 hours cells from the PDL and gingiva appeared to migrate into and repopulate the noncellular PDL. Few capillaries surrounded by mesenchymal cells and limited polymorphonuclear neutrophil infiltration were observed within the injured PDL site. Marginal gingival inflammation was minimal. At 14 days, collagen lysis, resorption of alveolar bone and root resorption were evident. In the PDL space, nonfunctionally oriented, cellular connective tissue elements were abundant. At 5 and 7 weeks, root resorption was marked. At this time interval, osteogenesis at seams of nonvital bone, repair cementum at sites of root resorption, and at times, ankylosis, were noted.(ABSTRACT TRUNCATED AT 250 WORDS)     

Regeneration of periodontal tissues by basic fibroblast growth factor

Several growth factors (or cytokines) have recently received attention because of their ability to actively regulate various cellular functions of periodontal ligament (PDL) cells and the effects of topical application of such factor(s) on periodontal tissue regeneration has been evaluated. In this study, we examined the role of basic fibroblast growth factor (bFGF) in the wound healing and regeneration of periodontal tissues. Alveolar bone defects (such as 2-wall, 3-wall and furcation class II bone defects) were created surgically in beagle dogs and primates. Recombinant bFGF was topically applied to the artificial bony defects. Six or 8 wk after application, the periodontal regeneration was morphologically and histomorphometrically analyzed. In all sites where bFGF was applied, significant periodontal ligament formation with new cementum deposits and new bone formation was observed in amounts greater than in the control sites. We found it noteworthy that no instances of epithelial down growth, ankylosis or root resorption were observed in the bFGF sites. In vitro studies demonstrated that bFGF enhances the proliferative responses of human PDL cells, which express FGF receptor-1 and -2, but inhibits the induction of alkaline phosphatase activity and mineralized nodule formation by PDL cells. Interestingly, we observed that the mRNA level of laminin in PDL cells, which plays an important role in angiogenesis, was specifically upregulated by bFGF stimulation, but that of type I collagen was downregulated. The present study demonstrates that bFGF can be applied as one of the therapeutic modalities which actively induce periodontal tissue regeneration. The results of in vitro studies suggest that by suppressing the cytodifferentiation of PDL cells into mineralized tissue forming cells, bFGF may play important roles in wound healing by promoting angiogenesis and inducing the growth of immature PDL cells, and may in turn accelerate periodontal regeneration.     

Dynamics of dentoalveolar ankylosis and associated root resorption

Abstract The present experimental studies in monkeys were undertaken to study the initiation and progression of dentoalveolar ankylosis of replanted teeth and associated root resorption. Maxillary and mandibular lateral incisors were extracted and replanted after an extraoral period of 15 min or 1 h. Teeth with an extraoral period of 1 h were endodontically treated. Half the number of monkeys were given antibiotics at the time of replantation. The observation periods varied from 2 days to 40 weeks. Irrespective of the length of the extraoral period, initial root resorption and minor areas of ankylosis were found 1 week after replantation. The initial ankylosis was not preceded by root resorption. In teeth replanted after an extraoral period of 15 min the ankylotic area did not increase with increasing time after replantation. Instead the periodontal membrane was re-established, separating the root surface from the alveolar bone. In teeth replanted after an extraoral period of 1 h, the initial ankylotic area increased with increasing time after replantation. Eight weeks and more after replantation, most of the periodontal membrane was replaced by bone covered by osteoblasts and occasional osteoblasts that were in continuity with the endosteal cells outlining the marrow spaces of the alveolar bone. The cementum and dentin were then gradually resorbed with increasing time after replantation. Antibiotics given at the time of replantation reduced the initial inflammation in the periodontal membrane and the inflammatory root resorption after all observation periods and it also seemed to some extent to prevent bacteria from entering the necrotic pulp tissue. Based on the present results it is suggested that root resorption associated with dentoalveolar ankylosis is initiated by endosteal osteoblasts and is thus a hormonally regulated process. This is in contrast to inflammatory root resorption, which seems to be triggered by inflammatory cells.     

A long-term study of 370 autotransplanted premolars. Part III. Periodontal healing subsequent to transplantation

The purpose of the present investigation was to determine the long-term prognosis of autotransplanted premolars with respect to periodontal healing. The subjects consisted of 195 patients aged 7 to 35 years, with a total of 370 autotransplanted all operated and followed with a standard technique. The observation period ranged from 1 to 13 years. Periodontal healing as demonstrated radiographically was complete in most cases after 8 weeks. Root resorption occurring after transplantation was divided into surface-, inflammatory- and replacement resorption (ankylosis). Root resorption occurred in 52 of the transplanted teeth and was usually diagnosed within 6 months. Root resorption was found to be significantly related to increasing stage of root development and the stage of eruption at the time of transplantation. Subsequent orthodontic movement of teeth with completed root formation at the time of transplantation resulted in a slight increase in the frequency of both surface and inflammatory resorption. The present study indicates that trauma to the PDL of the transplant is the explanatory factor for the development of root resorption.     

Dynamics of dentoalveolar ankylosis and associated root resorption

The present experimental studies in monkeys were undertaken to study the initiation and progression of dentoalveolar ankylosis of replanted teeth and associated root resorption. Maxillary and mandibular lateral incisors were extracted and replanted after an extraoral period of 15 min or 1 h. Teeth with an extraoral period of 1 h were endodontically treated. Half the number of monkeys were given antibiotics at the time of replantation. The observation periods varied from 2 days to 40 weeks. Irrespective of the length of the extraoral period, initial root resorption and minor areas of ankylosis were found 1 week after replantation. The initial ankylosis was not preceded by root resorption. In teeth replanted after an extraoral period of 15 min the ankylotic area did not increase with increasing time after replantation. Instead the periodontal membrane was re-established, separating the root surface from the alveolar bone. In teeth replanted after an extraoral period of 1 h, the initial ankylotic area increased with increasing time after replantation. Eight weeks and more after replantation, most of the periodontal membrane was replaced by bone covered by osteoblasts and occasional osteoblasts that were in continuity with the endosteal cells outlining the marrow spaces of the alveolar bone. The cementum and dentin were then gradually resorbed with increasing time after replantation. Antibiotics given at the time of replantation reduced the initial inflammation in the periodontal membrane and the inflammatory root resorption after all observation periods and it also seemed to some extent to prevent bacteria from entering the necrotic pulp tissue. Based on the present results it is suggested that root resorption associated with dentoalveolar ankylosis is initiated by endosteal osteoblasts and is thus a hormonally regulated process. This is in contrast to inflammatory root resorption, which seems to be triggered by inflammatory cells.     

Immediate replantation of maxillary incisors in rats: effects of tooth immersion in sodium fluoride and subsequent removal of the periodontal ligament

The advantages and disadvantages of maintaining the periodontal ligament (PDL) in immediate replantation as well as chemical treatment of the root surface have been a matter of discussion because the vitality of such tissue in surgery is always questioned. This study evaluated the effects of conserving the tooth in sodium fluoride and the removal of the PDL before replantation of incisors in rats. There was more cementum-dentin resorption in the group with the PDL. The group without the PDL showed more discreet resorption, repair occurred through the newly formed bone tissue in the PDL space and ankylosis was more extensive than in the group with the PDL.     

Replantation of 400 avulsed permanent incisors. 4. Factors related to periodontal ligament healing

Abstract 400 avulsed and replanted permanent teeth were examined for periodontal ligament (PDL) healing, using standardized radiographic and clinical examination procedures (i.e. percussion test and mobility test). The effect of various clinical factors was examined, such as age and sex of the patient, type of tooth replanted, presence of crown fracture or bone fracture, stage of root development (including apical diameter and length of the pulp), type and length of extra-alveolar storage, clinical contamination of the root surface, type of root surface cleansing procedure, type and length of splinting period and antibiotic therapy. Surface resorption was generally diagnosed after 12 months; while inflammatory resorption and replacement resorption (ankylosis) were usually observed after 1 month and 12 months respectively. Most resorptive processes were diagnosed within the first 2–3 years. However, although rarely, even after 5 and 10 years new resorptive processes could be diagnosed. A univariate statistical analysis of 272 teeth revealed 9 factors significantly related to PDL healing. A subsequent multivariate analysis revealed that the following 4 factors had the strongest impact upon PDL healing, in descending order of significance: Stage of root development; length of the dry extra-alveolar storage period; immediate replantation and length of the wet period (saliva or saline storage). Nonphysiological storage, such as homemade saline and sterilizing solutions (chloramine and alcohol) always led to root resorption. Storage in tap water for more than 20 minutes usually led to root resorption. The common denominator for all these factors related to PDL healing appears to be survival of the PDL cells along the root surface. Based on these findings, immediate replantation is recommended irrespective of stage of root development.     

Epithelial cells in PDL are critical in resuming the integral relation between tooth root and supporting bone after trauma--a transplantation experiment

OBJECTIVE: The aim of this study was to determine the response of the residual epithelial network following traumatic breakdown of the periodontal ligament (PDL). METHODS: Mandibular incisor sections with PDL (experimental) and sections denuded of PDL (control) from 4- to 6-week-old Wistar-Furth rats were transplanted into the defects created in the frontal bone of the recipient syngeneic rats. At intervals, the defects with implanted teeth roots were collected and processed for histological and biochemical examination. Immunolocalization of epithelial cells was performed to monitor their phenotypic changes during transplantation healing period. RESULTS: (1) Histological observation of the experimental sample revealed the sequence of cellular response characterized by an initial degeneration of PDL followed by a proliferation of granulation tissue. There was also a marked odontoblastic reaction with extensive deposition of regular dentine within the pulp chambers. In the control group, initial signs of bony fusion with dentine led to an extensive ankylosis and bone replacement between roots and defects. (2) Immunostaining indicated that, in experimental groups, the pattern of regularly spaced epithelial cells lying in close approximation to the root surface was distinct 10 days post-transplantation but became diminished afterwards. The immunoreaction against epithelial cells was negative in the control. CONCLUSION: Residual PDL is essential to prevent ankylosis after trauma and epithelial cells may facilitate the re-establishment of root-PDL-bone complex by transforming into mesenchymal cells.     

The Problem Of Dentoalveolar Ankylosis And Subsequent Replacement Resorption In The Growing Patient

Dentoalveolar ankylosis is a serious complication following injuries of the periodontal membrane in severe dental trauma such as avulsion and intrusion. The condition is a fusion of the alveolar bone with the tooth. The consequences of this condition are progressive resorption of the root with replacement by bone (replacement resorption) and arrested growth of the alveolar process in the growing patient. This article will present an overview of dentoalveolar ankylosis and replacement resorption and its problems, treatment options and prognosis. especially focusing on the growing patient.     

Patterns of healing on replanted baboon incisors coated with an allogeneic fibrin-fibronecftin protein concentrate

This study investigated the use of an allogeneic fibrin-fibronectin protein concentrate (AFFP) in preventing ankylosis and root resorption on replanted teeth during healing. In 2 adult male baboons (Papio ursinus) after extraction of the mandibular incisors, the coronal two-thirds of the exposed roots were planed to remove the remnant of the periodontal ligament and the cementum. The exposed dentinal surfaces were demineralized with citric acid at pH 1 for 3 min and notched at the junction between the planed and non-planed surfaces. Before replantation, the experimental roots and alveoli were coated with the AFFP prepared from pooled fresh-frozen baboon plasma. The animals were killed 55 days after operation and histometrical analysis was performed on serial sections cut in the buccolingual direction parallel to the long axis of the recovered specimens. An analysis of variance demonstrated significant differences between the two treatments with regard to the magnitude of ankylosis (greater for citric acid-demineralized plus AFFP-treated surfaces). There were variations in the magnitude of the different patterns of healing both between and within the experimental and control surfaces. Within the limits of the study, in this primate replantation model, the biochemical treatment of surgically exposed and demineralized root surfaces with AFFP did not enhance connective tissue attachment regeneration nor prevent dentoalveolar ankylosis and root resorption.     

Effect of platelet-derived growth factor-BB on root resorption after reimplantation of partially denuded tooth in dog

Abstract – The prognosis for a reimplanted tooth depends largely on the condition of the root. Platelet‐derived growth factor (PDGF)‐BB has been shown to regenerate periodontal tissue in animal and human clinical studies. However, information regarding the effect of PDGF‐BB on tooth reimplantation is limited. The objective of this study was to investigate the effect of PDGF‐BB on root resorption after reimplantation of a partially denuded tooth in dog. A total of 15 healthy female beagle dogs were used. Mandibular third and fourth premolars were endodontically treated and then extracted as atraumatically as possible. The coronal portion of each root was carefully scaled and planed. The roots on the right side of the mandible were treated with PDGF‐BB and reimplanted, while the roots on the left side served as controls. After 2, 4, or 8 weeks, specimens were collected and processed for histopathological examination. By the 4th week after reimplantation, new periodontal ligament (PDL)‐like tissue had formed around the PDGF‐BB‐treated root surfaces and new bone. By the 8th week, healing of the PDGF‐BB‐treated roots was characterized by newly formed PDL with inserting attachment formation. In contrast, control roots showed multiple areas of replacement resorption. Immunohistochemical staining of proliferating cell nuclear antigen (PCNA) performed at 2 weeks after reimplantation showed that the number of PCNA‐positive cells in the connective tissue area was statistically significantly greater in the PDGF‐BB‐treated group than in the control group (P < 0.001). The application of PDGF‐BB resulted in a significantly lower occurrence and extent of root resorption and ankylosis. These results suggest that the use of PDGF‐BB reduces occurrence of ankylosis and root resorption in tooth reimplantation.     

A histopathological study of the role of periodontal ligament tissue in root resorption in the rat

Whether periodontal ligament (PDL) tissue is capable of inducing root resorption was examined. The distal root of the rat molar was sectioned at the furcation and the PDL tissue removed from the root (non-PDL group, n=40). The distal root with the PDL intact was also prepared (PDL-intact group, n=40). The roots were transplanted into the dorsal skin of the rat. On the 1st, 3rd, 5th, 7th, 10th, 14th, 21st or 28th day after transplantation, the roots were removed together with surrounding dorsal subcutaneous tissue and were fixed, demineralized and embedded in paraffin. Serial sections from each block were stained with haematoxylin and eosin or by the tartrate-resistant acid phosphatase (TRAP) method to observe root-resorbing cell formation. Cyclo-oxygenase-2 (COX2) was also detected immunohistologically to examine prostaglandin E(2) production. On the 7th day after transplantation, multinucleated root-resorbing cells with TRAP were observed in the PDL-intact group. The number of TRAP-positive cells peaked on the 10th day after transplantation. COX2-positive cells were observed in PDL during the early experimental stages. No root resorption was seen in the non-PDL group. These results suggest that PDL tissue is involved in the formation of root-resorbing cells and root resorption.     

Bone Morphogenic Protein‐2 Induces Apoptosis and Cytotoxicity in Periodontal Ligament Cells

Background: Periodontal ligament (PDL) expresses endogenous growth factors, such as bone morphogenic proteins (BMPs), which facilitate maintenance of tissue homeostasis. Inflammatory conditions, such as chronic periodontitis, could disrupt this homeostasis, and physiologic levels of growth factors may be insufficient to maintain tissue homeostasis. BMPs facilitate periodontal bone regeneration but also are implicated in causing tooth ankylosis and root resorption. The underlying mechanism of tooth ankylosis is unclear. However, there is evidence that BMPs induce apoptosis in progenitor cells. Little is known about BMP‐induced cytotoxicity in PDL cells, which contain a population of progenitor cells. The aim of this study is to determine BMP2‐induced osteogenic mediators and cytotoxic effects in PDL cells and compare these cells to osteoblasts. Methods: Human PDL cells and primary osteoblasts were stimulated with doses of 1 to 200 ng/mL BMP2. Expression of alkaline phosphatase (ALP), in vitro mineralization along with osteonectin expression, induction of apoptosis, and cytotoxicity assays were performed. Results: PDL cells and osteoblasts upregulated ALP and in vitro mineralization in a dose‐dependent manner with BMP2 stimulation. However, at BMP2 concentrations >10 ng/mL, ALP, in vitro mineralization, and osteonectin were downregulated in PDL cells. Relative to osteoblasts, PDL cells were susceptible to apoptosis and cytotoxicity with 10 times lower concentration of BMP2. Conclusions: Relative to osteoblasts, PDL cells are susceptible to BMP2‐induced cytotoxicity. BMP‐induced tooth ankylosis is controversial and is poorly understood. Disruption of PDL homeostasis by BMP‐induced apoptosis could play a role in tooth ankylosis.     

Effect of masticatory stimulation on dentoalveolar ankylosis after experimental tooth replantation

Abstract Dentoalveolar ankylosis (replacement resorption) is a serious complication after replantation of avulsed teeth. The purpose of the present study was to investigate the influence of masticatory stimulation on dentoalveolar ankylosis after replantation of avulsed teeth. Monkey upper incisors were extracted, air-dried for 1 h, endodontically treated and replanted. No splinting was used. One group of monkeys was given hard pelleted food, while another group was given soft diet during a healing period of 8 wk. The periodontal conditions were evaluated histologically with a morphometrical method. The replanted teeth of the monkeys given the hard pelleted food had significantly less ankylosis and a larger area of the root surrounded by a normal periodontal membrane than the teeth from the monkeys given a soft diet. In conclusion, development of ankylosis seemed to be partially prevented or reduced by masticatory stimulation.     

Experimentally induced dentoalveolar ankylosis in rats

Dentoaiveoiar ankylosis is a common complication after replantation of teeth with injured periodontal ligaments. This is a serious complication for the tooth since it leads to progressive root resorption. In young individuals it may also cause infra-occlusion and reduced develop-ment of the alveolar process. The purpose of this study was to develop a method applicable to rats in order to follow the effect of systemic and local factors on the development of ankylosis and their possible effect on the length of the functional period of the ankylosed tooth before exfoliation. The maxillary first molars in adult rats were extracted. The periodontal ligaments were devitalized or removed before replantation of the teeth. Dentoalveolar ankylosis was clinically established 2 weeks after replantation. Induction was most reproducible after devitaiization or removal of the PDL cells with Dakin's solution and after keeping the rats on a liquid diet up to 3 weeks after replantation. Exfoliation of the teeth usually occurred 6 weeks after replantation. Histological examination showed that the PDL was replaced by bone. The ankylosed teeth showed root resorption to a varying degree. The resorption was in some cases occasionally located in the supra-crestal part of the tooth. A bone-like tissue in the root canal was a rather common finding. In one of the ankylosed teeth cartilage formation was found adjacent to the cementum.     

Delayed replantation after submucosal storage in order to prevent root resorption after replantation. An experimental study in monkeys

The purpose of this study was to determine the root resorption pattern of teeth autotransplanted to a submucosal site and to determine whether root resorption after replantation could be prevented by delayed replantation of teeth after submucosal storage in order to regenerate damaged periodontal ligament. Permanent teeth were extracted in green Vervet monkeys. One group of teeth was transplanted to a submucosal site and examined histologically in situ. Another group of teeth was autotransplanted to submucosal sites, recovered and replanted either 2 or 6 weeks later. The animals were sacrificed 8 week after replantation and examined histometrically. The following histologic parameters were registered: surface resorption, inflammatory resorption, replacement resorption (ankylosis), periapical inflammatory changes and downgrowth of pocket epithelium. Teeth autotransplanted to submucosal sites developed surface and inflammatory resorption. In half of the cases where teeth were transplanted with a vital periodontal ligaments new formation of bone took place adjacent to the transplant. Delayed replantation after submucosal burial was not found to inhibit the development of ankylosis, but changed the resorption type from direct apposition of bone upon the root surface to apposition of bone after initial resorption.     

Periodontal attachment responses to surgical injury in the cat. Removal of buccal bone with and without placement of foreign body at ligament periphery

Recently, PDL progenitor cells were claimed essential for the establishment of new connective tissue attachment to root surface. To further test new periodontal attachment after surgical injury, portions of the buccal alveolar plate were removed from the canines of 4 cats. Removal of bone was carried out with or without removal of the underlying PDL, and in half of the experimental sites, dental amalgam was placed at ligament periphery. Tissue blocks were prepared for routine histologic evaluation (H & E) and specific collagen stains (Mallory Trichrome and Mallory PATH). Exfoliation of amalgam was noted in 6 experimental sites during the healing period. At all sites, plaque accumulation and marginal gingivitis were observed before sacrifice. Histologic observation demonstrated limited new connective tissue attachment to root surfaces at PDL periphery where bone, PDL and cementum had been removed. Where PDL was retained, connective tissue attachment was present which appeared to be the result of fiber interdigitation between root-inserted fiber ends and gingival wound edge fibers. "Blockage" of PDL cell migration by amalgam could not be well controlled. However, the placement of amalgam seems to have interfered with new connective tissue attachment and/or cementogenesis. In 5 specimens, root resorption had progressed into dentin. At these sites, collagen tufts appeared to arise from dentin. These tufts were in intimate contact with zones of dense inflammatory cellular infiltrate and connective tissue elements. We suggest that this observation may be a further tissue response to injury, namely: root resorption with the unmasking of dentinal collagen, which may finally lead to fiber interdigitation.