Periodontal regeneration of transplanted rat molars after cryopreservation

The effects of cryopreservation on periodontal regeneration of transplanted rat molars were investigated histologically and histochemically in rats. Bilateral first and second maxillary molars of 4-week-old Wistar rats were gently extracted and transplanted into the abdominal subcutaneous connective tissue immediately or after cryopreservation in liquid nitrogen overnight. Donor teeth were slowly frozen by a rate-controlling freezer (program freezer) using 5% dimethylsulfoxide (DMSO) and 6% hydroxyethyl starch (HES) as cryoprotectants. One-four weeks after transplantation, they were carefully excised with the surrounding tissues. Regeneration of acellular cementum, periodontal ligament, and alveolar bone were observed 2 weeks after immediate transplantation. The pulp was repaired by the ingrowth of granulation tissue from the root apex followed by the formation of calcified tissue. The regenerated periodontal ligament was positive for alkaline phosphatase (ALP). Small or mononuclear tartrate resistant acid phosphatase (TRAP) positive cells were scattered on the newly formed alveolar bone and on the hard tissue in the pulp, but there was no external or internal progressive root resorption at 4 weeks. Cryopreserved teeth had acellular cementum with a rough surface at 1 week, but with the increase of cementoblasts and the appearance of periodontal ligament and alveolar bone, the surface became smooth at 3 weeks. Epithelial rests of Malassez (ERM) also revived. After regeneration of the periodontal tissues at 4 weeks, there was no evidence of root resorption. Although the process proceeded slowly, the cryopreserved teeth showed the periodontal regeneration substantially similar to that of the immediately transplanted teeth without progressive root resorption, indicating that they could be applicable for clinical use.     

Periodontal regeneration of transplanted rat teeth subcutaneously after cryopreservation

The periodontal regeneration of transplanted teeth after cryopreservation in liquid nitrogen overnight was previously examined using an animal model. The results showed that overnight cryopreservation did not have any severe adverse effects on periodontal healing. For clinical application, it is necessary to make the period of storage longer than in the preliminary study. In this study, the regeneration of periodontal tissues after cryopreservation for 4 weeks was examined. The maxillary molars of 4-week-old Wistar rats were extracted and transplanted into the abdominal subcutaneous tissue either immediately or after cryopreservation in a deep freezer at -80 degrees C. The donor teeth were frozen in a rate-controlling freezer. At 1, 2 and 4 weeks after transplantation, they were excised and observed under light microscopy. The cryopreserved teeth had acellular cementum with a rough surface at 1 week. With an increase in cementoblasts and the appearance of periodontal ligament and alveolar bone, the surface had become smooth at 2 weeks. There was no progressive root resorption. Although the process took somewhat more time, the teeth cryopreserved for 4 weeks showed regeneration that was similar to that of the immediately transplanted teeth.     

Autologous tooth transplantation to replace molars lost in patients with juvenile periodontitis

A method is described to replace perodontally destroyed first molars in patients with juvenile periodontitis by auto-transplantation of third molars. Fifteen molars which had been extracted due to periodontal destruction were replaced by autologous third molars with incomplete root formation. The patients were then observed for a period up to 7 years. In all cases complete regeneration of the alveolar bone took place and radiographically a normal periodontal membrane was extablished. All of the transplanted teeth continued their root formation and there was no radiographic evidence for root resorption, ankylosis or necrosis of the pulp. None of the transplanted teeth displayed pocket depths over 3 mm and no abnormal mobility was detectable.     

引导牙周组织再生在伴牙槽骨缺损牙再植术中应用的回顾性研究

目的 :回顾分析配合引导性组织再生术 (guidedtissueregeneration ,GTR)治疗对伴牙槽骨缺损的脱位再植牙的临床疗效的影响 ,为引导牙周组织再生的进一步研究提供经验。方法 :收集 1996年～ 2 0 0 3年间伴牙槽骨缺损、再植术中配合了GTR术治疗的完整病历资料 ,对其临床治疗情况及近远期疗效作回顾性研究分析。结果 :共收集到 2 3份符合条件的病历 (6 4颗再植牙 ) ,疗效分析结果表明 ,患牙术后 12个月探诊深度均显著减少 ,附着水平均显著获得 ;无论脱位时间长短 ,术后牙松动、牙根吸收和失牙的发生率均较高。伤后 6h内就诊脱位牙直接再植后 ,牙髓坏死率 77.5 % ,牙根吸收和失牙率与伤后就诊超过 6h组有显著性差异 (P <0 .0 1)。结论 :伤后就诊时间影响再植牙治疗效果 ,配合单纯GTR治疗 ,伴牙槽骨缺损的脱位再植牙的远期疗效仍然较差 ,利用GTR技术促进牙周组织再生特别是促进牙周缺损的再生需要进一步的基础与临床研究。     

Presence of an enamel matrix protein derivative on human teeth following periodontal surgery

An enamel matrix protein derivative (EMD) has been successfully employed to restore fully functional periodontal ligament, cementum, and alveolar bone in patients with severe attachment loss. When applied to denuded root surfaces, EMD is believed to assemble into a matrix that locally stimulates regenerative responses in the surrounding tissues. Since wound healing and induction of regeneration are biological processes typically running from weeks to months after treatment, the EMD matrix must be present on the root surface over a biologically significant time period to be effective. So far, no studies have been done in humans on the persistence of EMD on the treated root surface. The aim of the present study was to investigate the persistence of the EMD-based matrix on periodontally involved human teeth treated surgically with EMD. Sixteen patients with one intrabony defect each around teeth scheduled for extraction due to advanced periodontitis were treated by means of access flap surgery with and without application of EMD. At 1, 2, 3, and 4 weeks postsurgery, the teeth were removed and processed for histology and immunohistochemistry. The slides were stained using a rabbit anti-enamel-matrix-derivative (anti-EMD) antibody and goat-antirabbit secondary antibodies labeled with horseradish peroxidase (HRP). Immunohistochemical evaluation demonstrated the presence of EMD on all test root surfaces during the entire observation period of 4 weeks. No EMD was detected on any of the control roots. The results demonstrate for the first time in humans that EMD is present on treated root surfaces for up to 4 weeks following periodontal surgery.     

对过大牙槽窝行自体牙移植的动物实验研究

目的研究对受区过大牙槽窝行自体牙移植的方法。方法3只Beagle犬的18颗切牙作为供体牙,分为3组,分别植入到前磨牙区已预备好,近远中向比牙根宽2mm的牙槽窝中。再生组提前7d预备受区,利用再生组织充填;骨材料组使用瑞安生骨替代物充填;对照组不做处理。术后3月大体观察、拍X片和组织学检测比较3组的预后。结果所有移植牙均健康存活,无松动脱落。再生组示牙周膜再生,牙骨质和牙槽骨表面无吸收。骨材料组牙根发生炎症性吸收,有新骨生成。对照组牙根发生表面吸收。结论再生组织可以促进牙周再生,并减少牙根表面吸收;瑞安生骨替代物的使用有助于移植牙的稳定和存活,但其对牙周再生的作用尚待进一步研究。     

Attachment formation after transplantation of teeth cultured with enamel matrix derivative in dogs

Background: Implantation of cultured cells may be applied for periodontal regeneration in the future. However, a donor is essential in each case and tooth extraction is required to obtain the periodontal ligament–derived cell. We developed a novel regenerative technique combining tissue culture and transplantation of teeth. The purpose of this study is to evaluate the effect of enamel matrix derivative (EMD) on periodontal healing using this technique in dogs. Methods: A total of 32 incisors from seven beagle dogs were used. The periodontal ligament and cementum 5 mm from the coronal part of the roots were removed, whereas those in the apical part were preserved. Teeth were transplanted after the following treatments: 1) culture with application of EMD to the root surface for 6 weeks (n = 11); 2) culture without application of EMD for 6 weeks (n = 11); and 3) immediately transplanted without culture as control (n = 10). Eight weeks after transplantation, periodontal healing was analyzed. Results: The downgrowth of junctional epithelium on the roots of the EMD and culture groups was significantly smaller than that in the control group (P <0.01). Most of the root‐planed surfaces in the EMD group were covered with new cementum (72.2% ± 8.6%). This was significantly greater than that in the culture (29.1% ± 22.9%) and control groups (0.3% ± 1.1%). Conclusions: Transplantation of tissue‐cultured teeth decreased epithelial downgrowth and increased connective tissue attachment on the root‐planed surface. Furthermore, EMD could remarkably increase the new connective tissue attachment in this periodontal regenerative technique.     

Potential of Periodontal Ligament Cells to Regenerate Alveolar Bone

Regeneration of periodontal tissues, lost as a result of periodontal disease, is a key objective of periodontal treatment. Although several periodontal regeneration therapies have been devised, the origin of the undifferentiated cells that regenerate periodontal tissues remains unknown. Therefore, in the present study, to clarify the existence of osteoblast progenitor cells in the periodontal ligament, as well as to investigate the mechanism of alveolar bone regeneration without any effects from the original bone, we evaluated osteoblast differentiation induced by transplantation of GFP-transgenic rat molars into the subcutaneous tissues of wild-type rats. Ten days after transplantation, initial alveolar bone was formed apart from the cementum in the bifurcation region. After 20 days, this bone tissue had expanded to almost all of the bifurcation. GFP localization showed that the osteoblasts were derived from the transplant. Alpha-SMA- and BMP4-positive cells were observed near the root surface at 5 days after transplantation. With the progress of alveolar bone regeneration, osteoblasts expressing Runx2 and Osterix appeared in the bone-forming region. These results indicate that periodontal ligament tissue remaining on the root surface after a tooth extraction contains undifferentiated cells that have the ability to regenerate alveolar bone. The process of osteoblast differentiation in this model might be similar to that for normal alveolar bone formation. Thus, periodontal ligament cells might be useful for the regeneration of alveolar bone in tissue engineering applications.     

Periodontal repair in dogs: effect of root surface treatment with stannous fluoride or citric acid on root resorption

This study evaluated healing, with emphasis on root resorption, following root surface treatment with 1% aqueous stannous fluoride (SnF2), saturated citric acid (CA), or saline control (C) in conjunction with periodontal flap surgery. Supraalveolar periodontal defects were surgically created and immediately treated in the mandibular premolars in 6 beagle dogs. The defect height approximated 5 to 6 mm from the reduced alveolar bone to the cemento-enamel junction. Root treatments were rotated between experimental teeth within jaw quadrants and duplicated in left and right quadrants in the dogs. Flaps were raised to cover most of the crowns of the teeth and sutured. The dogs were sacrificed 12 weeks after surgery and tissue blocks with teeth and adjacent structures were processed for histometric analysis. SnF2-treated teeth healed with significantly longer junctional epithelium, less connective tissue repair to the root surface, and less bone regeneration than CA and C-treated teeth. New cementum formation was limited in all treatment groups. Root resorption was observed in almost all teeth exhibiting connective tissue repair, however to a lesser amount and not as frequent in SnF2 treated teeth due to limited connective tissue repair. No differences were found in amount and frequency of root resorption in CA and C-treated teeth. An inhibitory effect on root resorption of SnF2 could not be disclosed in this experiment, however, it may be concluded that CA treatment of the root surface in conjunction with reconstructive periodontal flap surgery does not seem to enhance root resorption.     

A Prospective,Case‐Controlled Study Evaluating the Use of Enamel Matrix Derivative on Human Buccal Recession Defects: A Human Histologic Examination

Background: Connective tissue grafts (CTGs) and coronally advanced flaps (CAFs) do not regenerate periodontal attachment apparatus when used to treat gingival recessions (GRs). Instead of generating new bone, cementum, and inserting periodontal ligament fibers, CTG+CAF repairs through a long epithelial junction and connective tissue attachment. Enamel matrix derivatives (EMDs) have demonstrated proof‐of‐principle that periodontal regeneration can be achieved, although data are limited. Methods: Three patients, each requiring extraction of four premolars before orthodontic treatment, were enrolled in a randomized, open‐label study. Two months after induction of Miller Class I and II GR, each patient received EMD+CAF for three teeth and CTG+CAF for one tooth for root coverage. Nine months after root coverage, all four premolars from each of the three patients were surgically extracted en bloc for histologic and microcomputed tomography (micro‐CT) analysis, looking for evidence of periodontal regeneration. Standard clinical measurements, radiographs, and intraoral photographs were taken over prescribed time points. Results: Seven of the nine teeth treated with EMD+CAF demonstrated varying degrees of periodontal regeneration, detailed through histology with new bone, cementum, and inserting fibers. Micro‐CT corroborated these findings. None of the three teeth treated with CTG+CAF showed periodontal regeneration. Clinical measurements were comparable for both treatments. One instance of root resorption and ankylosis was noted with EMD+CAF. Conclusions: EMD+CAF continues to show histologic evidence of periodontal regeneration via human histology, this being the largest study (nine teeth) examining its effect when treating GR. The mechanism of action, ideal patient profile, and criteria leading to predictable regeneration are in need of further exploration.     

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.     

Disuse atrophy of the periodontium in mice

Right, first and second maxillary molars of albino mice were extracted at 25 days of age to observe the long-term effect of early loss of function on teeth without antagonists. Four experimental and three intact controls were sacrificed every 50 days thereafter. Molars were studied grossly as well as microscopically. Macroscopic observations showed marked gingival recession and root exposure on teeth without function. Little cuspal wear occurred on these molars, and there was an intense blackening and discoloration of the enamel. Histologic sections revealed that loss of function alone, without any apparent infection, caused a remarkable and progressive atrophy of the periodontium, leading to its almost total disappearance by 900 days. Alveolar bone was extensively resorbed, particularly interdental bone. There was an apical proliferation of the epithelial attachment, a disorientation and detachment of fibres of the periodontal ligament and a considerable resorption of cementum. Only traces of periodontal tissues remained in the interdental region at 900 days and, in some instances, fusion of root tips of adjacent molars had taken place. There was a pronounced narrowing of the interdental space, but the direction of tooth movement could not be evaluated due to extensive loss of familiar periodontal landmarks. No cemental hyperplasia or supraeruption was apparent. These severe changes, which apparently are initiated at the alveolar crest, were interpreted as being due to the almost complete lack of stimulation of the periodontal tissues by occlusal contact.     

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.     

Healing after root reimplantation in the monkey

The aim of the present investigation was to evaluate the regenerative potential of the periodontal tissues following tooth reimplantation using a model which excluded the dentogingival epithelium from the process of healing. Maxillary and mandibular incisors, premolars and molars of 5 monkeys were used. Following root filling of all experimental teeth, the teeth were divided into 3 experimental groups. In 1 group, the teeth were extracted following the elevation of full thickness flaps. The crowns were separated from the roots at the level of the buccal cemento-enamel junction and the roots immediately reimplanted into their sockets. The flaps were replaced and sutured to accomplish complete coverage of the roots. In a 2nd group, the teeth were subjected to the same experimental procedure, but in addition, the buccal alveolar bone was removed to about half its original height prior to root reimplantation. The teeth of the 3rd group were subjected to identical experimental procedures as for group II with the addition that the buccal root surfaces were planed to the level of the surgically created bone crest. The animals were sacrificed after 6 months of healing. The jaws were removed and histological specimens prepared for microscopic examination. The results showed that a complete fibrous re-attachment formed onto roots on which the original periodontal ligament tissue was preserved. This occurred irrespective of whether the roots were reimplanted into sockets with normal (group I) or reduced (group II) bone height. When the original periodontal ligament tissue was removed by root planing before reimplantation (group III), healing resulted in a significant amount of new connective tissue attachment. However, coronal to the newly formed fibrous attachment, the root surface frequently showed signs of resorption and particularly so in those roots which remained covered by the soft tissue during the entire course of healing. In the majority of the roots which perforated the covering soft tissue during the early phase of healing, the dentogingival epithelium had migrated apically into contact with the coronally generated fibrous attachment. In these cases, root resorption was never discernible. New bone formation occurred to a variable extent in the roots of groups II-III. No relationship was found, however, between the amount of connective tissue reattachment or new attachment and newly formed alveolar bone, which in turn indicates that bone tissue regrowth and periodontal ligament regeneration are unrelated phenomena.     

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.     

Application of enamel matrix derivative in autotransplantation of an impacted maxillary premolar: a case report

BACKGROUND: The success of tooth transplantation or replantation depends on the viability of periodontal ligament in the planted tooth. Mechanical injury to periodontal tissues frequently results in dental root resorption and dental ankylosis, which leads to the failure of transplantation or replantation. Enamel matrix derivative (EMD) has been recently used to induce periodontal regeneration. In this report, we show a clinical case of EMD application in the transplantation of an inversely impacted and immature tooth. METHODS: An impacted second premolar was found in the right maxilla of a 16 year-old girl. The tooth was inversely impacted and the dental root was incomplete. When transplantation was carried out, EMD was applied to the periodontal tissues of the extracted premolar. The tooth was fixed at the correct position and the clinical condition was followed for evaluation for 6 months. RESULTS: Radiographs after 3 months exhibited new bone formation surrounding the transplanted tooth. After 6 months, considerable growth of dental root was evident, periodontal ligament-like radiolucency appeared, the vital reaction of the planted tooth was detected, and there were no signs of root resorption or ankylosis. CONCLUSION: Short-term results from this case indicate that EMD application was effective in the transplantation of an inversely impacted and immature tooth and that EMD might contribute to the growth of dental root and to the prevention of ankylosis.     

A clinical and radiographic study of 76 autotransplanted third molars

Abstract— The present investigation is a clinical and radiographic study of 76 auto-transplantations of third molars. The observation period ranged from less than one up to six years (average 3.7 years). In 58 cases the teeth were transplanted after extraoral root filling whereas 18 teeth were transplanted without endodontic intervention. At re-examination of the transplanted molars the marginal and the periapical conditions were examined clinically and radiographically. Third molars transplanted without root filling showed significantly less progressive root resorption and less increase in pocket depth as compared to teeth transplanted after extraoral root filling. A multivariate analysis was applied to examine the relationship between 17 clinical factors and the dependent variables - progressive root resorption, pocket depth, and periapical radiolucency - in 56 teeth transplanted after extraoral root filling. Progressive root resorption was found in 44 cases (79%), and this complication was found significantly related to the variables approximal grinding of donor tooth, extraoral period, and observation period. Increased pocket depth around the transplant was registered in 30 cases (52 %) and found significantly related to the period of splinting. Periapical radiolucency was found in 16 cases and was significantly related to the variable extraoral period.     

Interrelation between alveolar bone and periodontal ligament repair after replantation of mature permanent incisors in monkeys

Interrelation between alveolar bone and periodontal ligament repair was studied in green Vervet monkeys. Maxillary central incisors were extracted. The storage medium for the extracted teeth was saline in an 18 min. extra-alveolar group and dry storage in a 120 min. extra-alveolar group. In the experimental groups, the labial bone plate was removed surgically and the teeth replanted. In the control groups, teeth with similar extra-alveolar periods were replanted into sockets with intact labial bone, The animals were sacrificed 8 weeks after replantation and the replanted teeth examined histometrically. Root resorplion and the position of the labial bone in relation to the cemento-enamel junction were registered for each tooth. A significant relationship was found between the extent of labial bone repair and the extra-alveolar period. Thus, teeth with I8 min. extra-alveolar period showed almost complete repair of the labial bone plate, whereas teeth with an extra-alveolar period of 120 min. showed a mean position of labial bone 3.7 mm from the pocket epithelium. The extent of root resorption was influenced by the extra-alveolar period alone and not by the presence or absence of alveolar bone. It is concluded that a vital periodontal ligament upon replanted mature teeth is able to induce the formation of new alveolar bone.     

Periodontal repair in dogs Healing patterns in large circumferential periodontal defects

This report describes the healing patterns of large circumferential periodontal defects in the beagle dog. Approximately 5 mm large periodontal defects were created around the mandibular premolars (P2, P3 and P4) in 13 animals. The root surfaces were then instrumented to remove all cementum and the wounds immediately closed by replacing and suturing the flaps just coronal to the cemento-enamel junction. Block biopsies were harvested after 4 weeks. Most of the surgically denuded root surface healed with connective tissue repair. Cementum formation and regeneration of alveolar bone was limited and averaged approximately 30% and 20%, respectively, of the defect height. Almost all teeth exhibited root resorption. Ankylosis was observed in 1/3 of the teeth. There was no difference in the healing response between the 3 premolars or their buccal and lingual surfaces. The range of healing responses indicates that a biological potential exists which makes this model useful for testing the effect of various root and wound conditioners in (1) enhancing cementum formation on the root surface, (2) increasing regeneration of alveolar bone and (3) preventing aberrant healing events such as root resorption and ankylosis. Conversely, whether such agents may compromise wound healing and result in reduced connective tissue repair may concomitantly be tested.     

Study of regeneration in periodontal tissue after implantation of bone ceramic and collagen gel compound materials. Evaluation of histopathological finding and autoradiography

The aim of this study is to determine the process of periodontal tissue regeneration and the metabolic activity of osteoblasts after implantation of bone ceramic and collagen gel compound materials (BC). Bone defects were artificially prepared in the alveolar septa of the bilateral upper first and second molars of Wistar rats. Subsequently, BC were implanted into the defective sites on the left side, and the gingival flaps were closed. At the defective sites on the right side, as a control, gingival flaps were closed without implantation. Rats were sacrificed 1, 3, 5, 7 or 14 weeks after implantation, and prepared tissue sections were observed both pathologically and autoradiographically using 3H-Proline. The results obtained were as follows: Pathological Findings One week after BC implantation, inflammatory cellular infiltration of the surrounding gingival connective tissue was relatively mild. Three weeks after implantation, BC were present in fibrous connective tissues, and some directly bound to the marices of regenerated bone. Observation 5 weeks after implantation revealed that BC had become embedded in the regenerated bone matrices and that there was giant cell reaction to foreign bodies at the margin of BC located in connective tissue. BC were directly bound to the regenerated bone matrices without intermediary fibrous tissues 7 and 14 weeks after implantation. Connective tissues showed high grade regeneration of collagen fiber bundles, in an arrangement that tended to be fixed in mesial and distal directions. Autoradiographic Findings There was no uptake of 3H-Proline into the regenerated bone matrices or the gingival connective tissue surrounding BC, while uptake of 3H-Proline into the entire area around the root apex and in the vicinity of the alveolar septum was observed with time (weeks) after BC implantation. These results suggest that BC provide nuclei for bone regeneration through inclusion in newly-generated periodontal bone tissue, although it is difficult to produce definite induction of bone tissue by BC alone. It is also apparent that these are useful bone implantation materials for restoration of the physiological morphology of alveolar bone in periodontal surgical treatment.