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.     

Effects and distribution of the enamel matrix derivative Emdogain® in the periodontal tissues of rat molars transplanted to the abdominal wall

Abstract – The enamel matrix derivative Emdogain^® (EMD) has been found to promote regeneration of lost periodontal tissues. We have studied the effects and distribution of EMD in the periodontal tissues of maxillary rat molars transplanted to a subcutaneous position in the abdominal wall. The molars were transplanted with or without EMD either immediately after extraction or after drying for 30 min. After 2 days, 1, 2 or 4 weeks the rats were killed and the teeth were examined by means of light microscopy and immunohistochemistry with anti-amelogenin antibodies. Teeth transplanted immediately after extraction showed formation of alveolar bone separated from the dental roots by a periodontal space, regardless of the use of EMD. Among the teeth that were transplanted with EMD after drying for 30 min, new alveolar bone was formed in five out of eight teeth after 2 and 4 weeks. None of the teeth that were dried for 30 min and transplanted without EMD showed alveolar bone formation. Only one tooth transplanted with EMD showed root resorption after drying, while resorption was noted in all teeth transplanted without EMD. All teeth that were transplanted with EMD and none of the teeth that were transplanted without EMD showed an immunohistochemical reaction for amelogenin. After 2 days, amelogenin was precipitated on all surfaces exposed at the transplantation procedure. Later, the immunoreactive material was redistributed to cells at the root surface, where it was still demonstrable after 4 weeks. In conclusion, EMD is accumulated in cells at the root surface and promotes regeneration of the periodontal tissues of the transplanted teeth. It also seems to promote healing of root resorption.     

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.     

Dental regenerative therapy targeting sphingosine-1-phosphate (S1P) signaling pathway in endodontics

The establishment of regenerative therapy in endodontics targeting the dentin-pulp complex, cementum, periodontal ligament tissue, and alveolar bone will provide valuable information to preserve teeth. It is well known that the application of stem cells such as induced pluripotent stem cells, embryonic stem cells, and somatic stem cells is effective in regenerative medicine. There are many somatic stem cells in teeth and periodontal tissues including dental pulp stem cells (DPSCs), stem cells from the apical papilla, and periodontal ligament stem cells. Particularly, several studies have reported the regeneration of clinical pulp tissue and alveolar bone by DPSCs transplantation. However, further scientific issues for practical implementation remain to be addressed. Sphingosine-1-phosphate (S1P) acts as a bioactive signaling molecule that has multiple biological functions including cellular differentiation, and has been shown to be responsible for bone resorption and formation. Here we discuss a strategy for bone regeneration and a possibility for regenerative endodontics targeting S1P signaling pathway as one of approaches for induction of regeneration by improving the regenerative capacity of endogenous cells.Scientific field of dental scienceEndodontology     

Experimental study of periodontal tissue regeneration. Changes in the periodontium after tooth implantation with and without periodontal ligament

The role of the periodontal ligament in periodontal tissue regeneration was evaluated. The materials included bilateral upper 1st premolars and lower 2nd, 3rd, and 4th premolars of 11 adult Beagle dogs, aged from 3 to 6 years. Before implantation, the right teeth were extracted and kept for a period of more than 3 months in "a solution for reserving teeth". The left teeth on the other hand, were extracted and soon implanted thus retaining the periodontal ligament into the newly created bone cavities prepared in the right edentulous areas. At the same time, the right reserved teeth were implanted into the left tooth sockets. Implanted teeth were periodically observed macroscopically, radiographically, and histologically for a 6-month period. Macroscopical observation showed good clinical repair in the bilateral sides of the tooth implantation with and without a periodontal ligament. After a 6-week experimental period, radiographic observations of the implanted lower right teeth having a periodontal ligament revealed lamina dura-like findings. Histopathological investigation revealed ankylosis and root resorption on the left side, where the reserved teeth without a periodontal ligament were implanted. But regeneration of the periodontal tissue complex, which consisted of the gingiva, alveolar bone, cementum, and periodontal ligament, was generally observed in the implanted right teeth having a periodontal ligament. These results suggest that the periodontal ligament cells play a significant role in periodontal tissue regeneration.     

Periodontal regeneration via selective cell repopulation

The purpose of this investigation was to determine the histogenesis of periodontal regeneration using the principle of selective and guided cell repopulation of the root surface. A fenestration model, developed in the squirrel monkey, made it possible to exclude gingival epithelium and connective tissue and promote cell repopulation of the denuded root surface from the periodontal ligament and alveolar bone. Experimental and sham-operated control sites were compared histometrically after 3, 7, 14 and 35 days of healing. The results indicated that new cementum, bone and periodontal ligament formation occurred by the 14th day and that regeneration of the fenestration wound was almost complete by Day 35. Root resorption and ankylosis were observed in both experimental and sham-operated controls. There was significantly more periodontal regeneration in the experimental sites, which favored cell repopulation of the root surface from the periodontal ligament and alveolar bone.     

Ankylosis of the mouse molar after systemic administration of 1-hydroxyethylidene-1,1-bisphosphonate (HEBP)

Abstract The proposed homeostasis between fibroblasts in the periodontal ligament and bone cells lining the inner aspect of the alveolar wall is thought to be responsible for maintaining the width of the periodontal ligament space. In the present study, we attempted to interfere with this cellular balance by systemic administration of 1-hydroxyethylidene-1, 1-bisphosphonate (HEBP). The maxillary left molars of mice were extracted. They then received a daily subcutaneous injection of HEBP (10 mg P/kg b.w.) for periods of 10, 30 or 50 days. A 2nd group of animals received HEBP without molar extraction. Control groups were injected with Ringer's solution. The animals were sacrificed after the last injection and the mandibles processed for light and electron microscopy. HEBP treatment caused a significant decrease of the width of the periodontal ligament space which was influenced by time. Ankylosis started to occur after 30 days, predominantly in the interradicular areas and was more common around unopposed teeth. At 50 days, signs of resorption were seen along the acellular cementum layer. During HEBP-administration, extensive deposition of newly formed cementum matrix was observed along the cellular cementum but this activity was not seen along the acellular cementum. It is concluded that HEBP interferes with the mechanisms that mediate preservation of the periodontal ligament width.     

Bone regeneration after surgical repositioning of impacted mandibular second molars: a case report

Abstract  – A case is presented where the mesially impacted mandibular second molar teeth were surgically uprighted in an 11-year-old female patient. Bone regeneration is shown in the areas occupied by the impacted second molars with maturation of bone and cortication of the crest of the alveolar bone. The probing depths are also normal with no residual bony defects. This healing was achieved with no bone grafting procedure, emphasizing two important factors: to prevent/minimize any trauma to the tissues at the site of elevation and uprighting of the tooth (i.e. maintaining viable periodontal ligament cells and minimal cementum damage); and to obtain primary closure whilst allowing the tissue in the mesial defect to reorganize against the scaffold of bone. However, the procedure on the one side was complicated with necrosis and infection of the pulp space with external inflammatory root resorption. Endodontic therapy of this tooth proved to be successful with periradicular healing radiographically and re-establishment of the lamina dura. At the 3-year follow-up, the endodontically treated tooth showed no clinical and radiographic signs of pathology. The left second mandibular molar had no pulpal or periodontal postsurgical complications, which may be attributed to apparently more open apices allowing for pulp revascularization after manipulation at the time of surgery. This report illustrates unassisted wound healing that occurs in the area of uprighting with complete reconstitution of periodontal anatomy without additional regenerative procedures to augment 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.     

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.     

Treatment of root surface in delayed tooth replantation: a review of literature

Abstract –  The time elapsed between a trauma and tooth replantation usually ranges from 1 to 4 h. The chances of root surface damage are higher when tooth replantation is not performed immediately or if the avulsed tooth is not stored in an adequate medium. This invariably leads to necrosis of pulp tissue, periodontal ligament cells and cementum, thus increasing the possibility of root resorption, which is the main cause of loss of replanted teeth. This paper presents a comprehensive review of literature on root surface treatments performed in cases of delayed tooth replantation with necrotic cemental periodontal ligament. Journal articles retrieved from PubMed/MedLine, Bireme and Scielo databases were reviewed. It was observed that, when there are no periodontal ligament remnants and contamination is under control, replacement resorption and ankylosis are the best results and that, although these events will end up leading to tooth loss, this will happen slowly with no loss of the alveolar ridge height, which is important for future prosthesis planning.     

完全脱位牙即刻与延迟再植根吸收的动态观察

目的：动态观察实验大鼠再植牙牙根吸收及愈合过程,辅助临床治疗及预防再植牙牙根吸收。方法：30只6周龄SPF级Wistar雄性大鼠,分为6组,每组5只,其中一组为空白对照组。实验组大鼠双侧上颌第一磨牙脱位后再植,每只大鼠随机选取一侧脱位牙齿即刻再植,对侧同名牙则于体外干燥保存30min后再植回牙槽窝。分别于术后1、3、7、14、21d处死,分离上颌骨,拍摄x线片,应用IPP软件测量上颌第一磨牙近中根根周透影面积。标本脱钙后制作切片、HE染色,进行组织学观察。结果：再植牙根尖周透影面积随时间延长而增大,干燥组表现尤其明显;组织学上表现为初期炎症反应较明显,随着炎症发展,牙根表面吸收陷窝逐渐增多、增大,后期即刻组牙髓及牙周膜修复反应明显,干燥组牙槽骨修复反应强烈,牙根、牙周膜逐渐被类骨质样组织替代。结论：再植牙初期以炎症反应为主,后期主要表现为修复反应,即刻与延迟再植导致牙周膜细胞活性不同决定了再植牙根吸收的进展。     

Repair of periodontal tissues In vivo and in vitro

Repair of experimental cavities in dental roots and of periodontal wounds was studied in vivo and in vitro. Incisors from monkeys were extracted and experimental cavities were made in the roots. The teeth were either replanted immediately or cultured for 1-12 weeks in tissue culture medium. After 8 weeks the tissue reaction around the replanted teeth was evaluated on demineralized histological sections and undecalcified freeze-sections incubated for histochemical demonstration of certain enzymes. The cultured teeth were evaluated on decalcified histological sections. In the experimental cavities of the replanted teeth reparative cementum was found. It was frequently separated from the denuded dentin while a firm attachment was always established to the intermediate cementum and dental cementum at the periphery of the cavities. The reparative cementum was also firmly attached to some small areas on the exposed dentin surface where resorption had taken place. The activity of alkaline and acid phosphatase was lower in the connective tissue in the experimental cavities than in the surrounding PDM, suggesting an incomplete regeneration of the periodontal membrane in these areas. A loose connective tissue devoid of demonstrable collagen fibers was found in the cavities in vitro. The reparative cementum did not fill the experimental cavities in the replanted teeth. The alveolar bone extended into the experimental cavities and made the width of the PDM normal also in the experimental cavities. Epithelial and endothelial cells were numerous in the connective tissue separating the reparative cementum from the alveolar bone in the experimental cavities. It is possible that they contribute to the integrity of the PDM and prevent resorption of the dental root.     

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.     

Local delivery of prostaglandin E1 induces periodontal regeneration in adult dogs

Formation of cementum, alveolar bone and periodontal ligament was produced in 18 sites on buccal surfaces of mandibular premolars and molars of 11 adult dogs near to sites of local delivery of prostaglandin E₁ (PGE) for three weeks. Mineralizing bone and cementum were labelled with fluorescent dyes and polarizing microscopy showed periodontal ligament fibers between these new mineralized tissues. These observations extend recent demonstrations that local application of PGE causes formation of new bone on the mandible and suggest the potential for predictable, site-directed periodontal regeneration.     

Histologic evaluation of new attachment apparatus formation in humans. Part II

There is conflicting evidence regarding the value of graft materials in enhancing the formation of new bone, cementum, and periodontal ligament (new attachment apparatus). Part II of this study compared the healing of intrabony defects with and without the placement of decalcified freeze-dried bone allograft (DFDBA) in a submerged environment. The most apical level of calculus on the root served as a histologic reference point to measure regeneration on root surfaces exposed to the oral environment. Biopsies were obtained at 6-months and evaluated histometrically by two investigators unaware of the treatment performed. Data from 9 patients with 30 grafted defects and 13 nongrafted defects were submitted for statistical analysis. Results indicate that in a submerged environment significantly more new attachment apparatus (P less than .05) and new bone (P less than .05) formed in grafted than nongrafted sites. Significantly greater loss of alveolar crest height occurred in nongrafted than grafted defects (P less than .05); regeneration of new attachment apparatus, new bone, and new cementum occurred more frequently in grafted than nongrafted defects. There was a greater chance for the regeneration of a connective tissue attachment in nongrafted intrabony defects than in grafted defects; new cellular cementum formed equally well on old cementum, dentin, or both old cementum and dentin in the same defect. The periodontal ligament was oriented parallel, perpendicular, or both parallel and perpendicular in the same defect; and, no extensive root resorption, ankylosis, or pulp death was observed in grafted or nongrafted defects.     

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。     

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。     

Periodontal new attachment therapy]

The ultimate goal of periodontal therapy includes not only the arrest of progressive periodontal disease, but also the restitution of those parts of the supporting apparatus which were destroyed by the disease. Regeneration of periodontal structures dissolved because of periodontal disease is the goal of reconstructive periodontal treatment procedures. The achievement of this goal requires the formation of new cementum with inserting collagen fibers of previously periodontitis involved root surfaces possibly with a concomitant regeneration of supporting alveolar bone. Healing, after periodontal therapy, leads to the formation of long junctional epithelium, root resorption, ankylosis, etc. These are repair process and not one of regeneration. But guided tissue regeneration seems to lead to regeneration with active periodontal ligament cells.     

Reprint of: Relationship Between Surface and Inflammatory Resorption and Changes in the Pulp After Replantation of Permanent Incisors in Monkeys

The etiology of surface and inflammatory root resorption after the replantation of incisors was examined in green vervet monkeys. The teeth were examined histologically and histobacteriologically for pulpal healing and root resorption 2 and 8 weeks after replantation. In contrast to surface resorption, inflammatory resorption was related to infected necrotic tissue or an infected leukocyte zone in the root canal. The following theory for surface and inflammatory resorption is presented. Damaged periodontal ligament areas and damaged parts of the root surface are attacked by a resorption process whereby resorption of cementum and dentin may occur. Inflammatory resorption or surface resorption will then occur depending on the pulpal status and the depth of the resorption cavity. If the resorption cavity penetrates the intermediate layer of cementum and contacts dentinal tubules that are in communication with infected necrotic pulp tissue or an infected leukocyte zone, then inflammatory resorption will take place as a result of the diffusion of toxic elements from the pulp canal to the resorption cavity. However, if the resorption cavity is shallow and does not penetrate the intermediate layer of cementum, a tooth that displays similar pulpal changes will elicit only surface resorption because the intermediate layer of cementum will tend to arrest the diffusion of toxic elements. Finally, if the pulp contains vital, inflamed, or noninflamed tissue or if root canal treatment has been performed, surface resorption will occur regardless of the depth of the cavity.