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.     

The effect of apicoectomy before replantation on periodontal and pulpal healing in teeth in monkeys

The effect of resection of the apical part of the root before replantation upon periodontal and pulpal healing was studied in 7 green Vervet monkeys (Cercopithecus aethiops) using teeth with incomplete and complete root formation. Maxillary central incisors, mandibular lateral incisors and first and second mandibular molars were used in this experiment. On one side, the tooth was extracted and replanted with an intact root while the contralateral tooth had 2 mm of the apex resected for the purpose of facilitating pulpal repair and eliminating resorption in the resorption-prone region of the root. The replanted teeth were examined histologically 8 weeks after replantation. The histometric analysis revealed no significant difference in periodontal healing between teeth with or without apical resection. With regard to pulpal healing, apical resection was found to lead to significantly less vital pulp tissue in teeth with immature root formation. A similar, but not significant difference was found for mature teeth. Based on these findings, it could not be recommended that apices be resected prior to replantation in order to improve pulpal repair.     

In vitro proliferation of periodontal ligament-like tissue on extracted teeth

ObjectiveTransplantation of autologous teeth is a routine component of orthodontic treatment. The aim of this study was to develop a method for the regeneration of damaged periodontal ligament (PDL) on extracted teeth using a three-dimensional culture system.DesignWe used the maxillary first premolars or third molars extracted from patients for orthodontic treatment. The extracted teeth were stained with toluidine blue to measure the residual PDL area. After confirming damage of the periodontal tissue on the root surface of the extracted teeth, we tried to regenerate the periodontal tissue. Other extracted teeth were inserted into a cell strainer filled with cellulose-based carrier materials to regenerate the periodontal tissue. The strainer was then placed in a 90-mm culture dish filled with culture medium and incubated at 37 °C and 5% CO2 for about 1 month. The cultured teeth were observed under a stereomicroscope and examined by scanning electron microscopy (SEM), and were stained to detect alkaline phosphatase (ALP) activity.ResultToluidine blue staining revealed that the residual periodontal membrane covered an average of 50.4% of the root surface area of each tooth. After culturing extracted teeth with our culture system, globular structures were found on the entire tooth root surface by stereomicroscopy, and PDL-like filamentous tissue was also detected by SEM. The entire tooth root surfaces of the cultured teeth were positive for ALP activity.ConclusionsWe have developed a useful culture method to stimulate the proliferation of cells in PDL-like tissue on the roots of extracted teeth.     

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。     

Periodontal healing of replanted monkey teeth prevented from drying

Root resorption of replanted teeth is dependent on the duration of the extra-alveolar period and on the storage environment. In the present investigation the significance of preserving the humidity of the periodontal ligament (PDL) during the extra-alveolar period was tested on isolated PDL cells and on replanted monkey teeth. The isolated PDL cells were tested with respect to cell viability (trypan blue exclusion test) and to cell recovery (number of cells after additional cultivation). About 70% of the cells were viable and 44% recovered after 1 h in a humid atmosphere. Practically no cells were viable or recovered after 1 h of drying. Replanted teeth that had been wrapped in plastic foil for 1 h before replantation showed no more resorption than immediately replanted teeth. This is in contrast to teeth dried in air for 1 h before replantation. They showed extensive root resorption on almost all root surfaces. Thus, prevention of evaporation of tissue fluid from the PDL must be considered a primary goal if the tooth cannot be replanted immediately.     

Complete replacement resorption after replantation of maxillary incisors: report of case.

This article describes the treatment of a 17-year-old patient with complete root resorption of the maxillary permanent central and lateral incisors following avulsion and replantation seven years ago. The most important factor influencing the prognosis of replanted teeth is the status of the periodontal ligament (PDL). As a result of replantation, the PDL cells necrosed and tooth replacement resorption occurred. The main factors, which affected the resorption after replantation and survival of PDL cells, could be summarize as; dry extraoral time greater than 30 minutes, the kept tooth in a dry environment, touching the cementum surface, and splint treatment for a prolonged time. Since complete root resorption was found in our case, these factors probably also occurred.     

Occlusal forces promote periodontal healing of transplanted teeth and prevent dentoalveolar ankylosis: an experimental study in rats

The process of healing periodontal ligaments (PDL) after transplantation has been widely examined, but the mechanism for preventing dentoalveolar ankylosis is still unclear. In this study, we focused on the role of mechanical stimuli in preventing ankylosis using an animal model of tooth transplantation assessed by histologic observation and evaluation of proliferating PDL cells. Five-week-old Sprague-Dawley male rats were divided into occluded and nonoccluded groups. The right maxillary first molars were replanted in both groups, and histologic observations were carried out after one or two weeks. The proliferative activity of PDL cells was also examined by assessing the distribution of 5-bromo-2'-deoxyuridine (BrdU). After two weeks in the nonoccluded group, ankylosis was clearly detected and PDL stricture was obvious, whereas no severe bone or root resorption was observed. On the other hand, the occluded group showed an enlarged and thickened PDL with extensive root resorption, but no ankylosis. Based on these findings, the replanted teeth were given a one-week healing period and then occlusion recovery was assessed, which resulted in decreased ankylosis and root resorption. The proliferative activity of PDL cells in the occluded group was generally higher than in the nonoccluded group. The activity of PDL cells in the recovery group was also higher than that of the nonoccluded group. These results suggest that occlusal stimuli promoted the regeneration of the PDL and prevented dentoalveolar ankylosis, whereas excessive initial force might cause severe root and bone resorption.     

Influence of conventional forceps extraction and extraction with an extrusion instrument on cementoblast loss and external root resorption of replanted monkey incisors

Cementoblast loss and root resorption on the root surface was registered histologically after removal and immediate replantation of maxillary central incisors in monkeys ( Cecropithecus aethiops ). Incisors were removed with either a conventional extraction technique using forceps or with a special designed extrusion instrument and in both cases teeth were immediately replanted. Altogether 18 monkeys were used for the experiments in which 9 monkeys were sacrificed after 3 d and 9 animals after 8 wk. Histological analysis was made in horizontal sections perpendicular to the long axis of the tooth using either 24 measuring points or 12 sections. Histometric analysis showed extensive cementoblast loss in the periodontal ligament (PDL) and with a maximum of damage occurring on the corner surfaces of the root. Extracted teeth showed significantly more extensive cementoblast loss than extruded teeth. Root resorption was also found in the corner locations and was significantly more frequent in extracted than in extruded teeth. There was a similarity in the distribution of cementoblast loss and root resorption indicating that root resorption develops in the same areas where cementoblast loss takes place, i.e. locations that are more compressed during removal of the tooth and must have caused by mechanical damage to the PDL exerted on the root surface during tooth removal.     

偏侧咀嚼对正畸牙移动影响的实验研究

目的通过建立偏侧咀嚼大鼠模型,探讨偏侧咀嚼对正畸牙移动过程的影响。方法选择30只6～8周龄,（250±10）g,雄性SD大鼠,随机分为实验组与对照组,每组各15只。通过拔除实验组大鼠右下颌所有磨牙使右上颌第一磨牙丧失咬合接触建立大鼠偏侧咀嚼动物模型,同时,在两组大鼠双侧上颌切牙和第一磨牙间放置镍钛拉簧,初始力值为50g,近中移动磨牙。分别于第0、3、7、10、14天测量大鼠上颌第一磨牙近中移动的距离并通过HE染色观察大鼠上颌第一磨牙牙周组织形态学变化。结果各时间点代偿性咀嚼增强侧牙移动速率均小于对照组（P〈0.05）,牙周组织变化与对照组相似;失咬合侧牙移动速率大于对照组（P〈0.05）,牙周组织出现退行性改变;但三种咬合状态下牙齿移动速率曲线均表现为瞬时运动、迟滞期及后期移动三个阶段。结论动物实验证实偏侧咀嚼引起正畸牙牙周组织发生相应改变最终影响牙移动速率,但无论牙移动速率快慢,牙移动均符合正畸性牙移动的一般规律。     

Proliferation,migration and apoptosis of periodontal ligament cells after tooth replantation

Oral Diseases (2010) 16 , 263–268 Objective: The aim of this study was to investigate the proliferation, migration and death of periodontal ligament (PDL) cells after tooth replantation. Materials and methods: Maxillary first molars were extracted from 4‐week‐old male (n = 28) Sprague–Dawley rats and immediately replanted, after which, proliferation, migration and death of PDL cells were investigated. Results: At 3 days after tooth replantation, many proliferative cell nuclear antigen (PCNA)‐positive PDL cells were observed on the alveolar bone side, but fewer on the root side. However, while a gradual decrease was observed in number of PCNA‐positive PDL cells on the alveolar bone side until 7 days, an increase was seen on the root side. At 3 weeks, cells labeled with PKH26 (fluorescent dye into plasma membrane) were located in the middle of the PDL space. However, these PKH26‐labeled cells did not spread to the surface of the cementum or the alveolar bone. TUNEL‐positive cells were observed on both the bone and root sides at 3 days. Number of apoptotic cells increased until 7 days on the bone sides, but decreased on root sides. Conclusion: These results suggest that both cell proliferation and apoptosis occur in different patterns and at different times to maintain regular spacing of the PDL after tooth replantation.     

Short-term vs long-term calcium hydroxide therapy after immediate tooth replantation: a histomorphometric study in monkey's teeth

Abstract – Endodontic treatment is an important step of tooth replantation protocols, but the ideal moment for definitive obturation of replanted teeth has not yet been established. In this study, a histomorphometric analysis was undertaken to evaluate the repair process on immediate replantation of monkey’s teeth after calcium hydroxide (CH) therapy for 1 and 6 months followed by root canal filling with a CH‐based sealer (Sealapex^®). The maxillary and mandibular lateral incisors of five female Cebus apella monkeys were extracted, kept in sterile saline for 15 min, replanted and splinted with stainless steel orthodontic wire and composite resin for 10 days. In Group I (control), definitive root canal filling was performed before tooth extraction. In Groups II and III, CH therapy started after removal of splint, and definitive root canal filling was performed 1 and 6 months later, respectively. The animals were euthanized 9 months after replantation, and specimens were processed for histomorphometric analysis. In all groups, epithelial attachment occurred at the cementoenamel junction or very close to this region; the areas of resorption on root surface had small extension and depth and were repaired by newly formed cementum; and the periodontal ligament was organized. Statistical analysis of the scores obtained for the histomorphometric parameters did not show any statistically significant difference (P = 0.1221) among the groups. The results suggests that when endodontic treatment is initiated 10 days after immediate replantation and an antibiotic regimen is associated, definitive root canal filling can be performed after a short‐term CH therapy.     

Histological and immunohistochemical analyses of the chronology of healing process after immediate tooth replantation in incisor rat teeth

Abstract – Dental tissues have special characteristics, and its regenerative capacity is noteworthy. However, understanding the circumstances that lead to regeneration is challenging. In this study, the chronology of the healing process after immediate replantation of rat incisor teeth was examined by histological and immunohistochemical analyses within a 60‐day period. Thirty‐six male Wistar rats had their maxillary right incisors extracted and replanted after 15 min in saline storage. The rats were sacrificed immediately 3, 7, 15, 28, and 60 days after replantation. The histological analysis showed rupture of the periodontal ligament and formation of a blood clot, which started being replaced by a connective tissue after 3 days. At 7 days, the gingival mucosa epithelium was reinserted and areas of root resorption could be seen. At 15 days, the periodontal ligament was repaired. At 3 days, the pulp presented an absence of the odontoblast layer, which started being replaced by a connective tissue. This tissue suffered gradual calcification, filling the root canal at 28 and 60 days. The root ends were closed. The immunohistochemical analysis revealed greater expression of OP, OPG, and RANK proteins in the initial periods (0 and 3 days), while TRAP expression predominated at 28 and 60 days (P < 0.05). In conclusion, in delayed tooth replantation, there is great new bone formation activity in the earlier periods of the repair process, while a predominance of bone resorption and remodeling is observed in the more advanced periods.     

Periodontal response to experimental tooth movement by interrupted orthodontic force in rats

The upper first molars of Wistar rat were moved experimentally using an expansion screw in order to clarify whether an interrupted orthodontic force that maintains the blood circulation in compressed periodontal ligament (PDL) can cause efficient tooth movement without pathological damage.In the 30-μm group with moving distance of one-third of PDL width, degenerating tissue with toluidine blue staining and appreciable root resorption were not seen during the experimental period. On the other hand, in the 60-μm group with moving distance of two-third of PDL width degenerating tissue and severe root resorption appeared. On observation of bone formation using Villanueva fluorescent staining, a thick labeling line was observed on the tension side in both experimental groups.In statistical analysis about the ratio between mesial and distal PDL areas, expressing expansion rate of mesial PDL, there was no significant difference between 30-μm and control groups, except an experimental period of day 11. In contrast, significant differences were seen between 60-μm and control groups in 23–31 days after tooth movement.From these results, it is evident that the interrupted force that induces tooth movement within a distance of approximately one-third of PDL width enables tooth movement without toluidine blue-stained degenerating tissue, regarded as pathological damage, and promotes bone formation on the tension side.     

Microscopic evaluation of induced tooth movement in traumatized teeth: an experimental study in rats

Abstract – The clinical management of orthodontic patients with dental trauma before or during the treatment is mainly founded on clinical experience, expert opinions, and individual case reports. It is proposed in the literature that teeth sustaining mild trauma with minor damage to the periodontium (e.g. subluxation) should be followed for a period of time before being subjected to orthodontic forces. A minimum period of 3 months has been proposed. In this study, we used an animal model to investigate whether shorter observation periods could be established in case of mild trauma. The periradicular region of rat molars was examined microscopically to determine the biological events of tooth movement started 15 and 30 days after intentional subluxation using an experimental method to induce dentoalveolar trauma. Thirty adult male Wistar rats were assigned to 6 groups (n = 5): Group 1 (control – no trauma/orthodontic movement); Group 2: the animals received an orthodontic device and were sacrificed after 7 days; Groups 3 and 4: dentoalveolar trauma (subluxation) was experimentally induced by the application of an axial force of 900 cN on the occlusal surface of the maxillary right first molar, and the animals were sacrificed after 22 and 37 days, respectively; and Groups 5 and 6: 15 and 30 days, respectively, after force application, an orthodontic device was installed and the rats were sacrificed 7 days later. In G5 and G6, the periodontal ligament and pulp tissue were rich in cellular elements and blood vessels, the alveolar bone was preserved, and the root surface presented only very small areas of surface resorption (cementum), maintaining the characteristics of normality. In conclusion, the microscopic alterations in the gingival and periodontal tissues in response to an experimentally induced mild dentoalveolar trauma simulating subluxation were not sufficient to contraindicate starting the orthodontic movement 15 and 30 days after trauma.     

Root resorption in deciduous teeth after applying orthodontic forces

The relation between orthodontic forces applied to deciduous teeth and the occurrence of root resorption, as a possible outcome of these forces, has not been studied to date. The aim of this work was to study root resorption in deciduous teeth of patients receiving orthodontic treatment. Twenty-four deciduous molars extracted for therapeutic purposes were studied: nineteen molars treated with light orthodontic forces and five untreated molars that served as control. Histological and histomorphome tric studies were performed to determine the magnitude of root resorption. Location of root resorption in treated deciduous teeth was different from that of physiological root resorption. Extent and volume of root resorption were more extensive and deeper in treated than in untreated teeth. These results suggest that radiographic follow-up of deciduous teeth subjected to orthodontic forces would be useful to prevent root fractures.     

Replantation of teeth and antibiotic treatment

Abstract Administration of antibiotics is usually recommended when a traumatically avulsed tooth is replanted, in order to prevent bacterial contamination. In the present study, permanent lateral incisors of monkeys were extracted, allowed to dry for 1 h and then replanted. Some teeth had their pulp chambers opened labially and left open for 3 wk after replantation. The monkeys were treated with antibiotics (i.m.) either at the lime of replantation or 3 wk after replantation. In some monkeys, antibiotics were placed in the pulpal cavity. Comparisons were made of the effect of endodontic treatment on periodontal healing and root resorption. The monkeys were killed 8 wk after replantation. It was found that after systemic antibiotic treatment at the time of replantation there was no inflammatory root resorption. Also, endodontic treatment at the time of replantation prevented inflammatory root resorption. When systemic antibiotic treatment was instituted 3 wk after (he replantation, there was no reduction of the inflammatory root resorption as compared with teeth without antibiotic treatment. Application of antibiotics in the pulp 3 wk after replantation almost completely eliminated the inflammatory resorption. In all the treatment groups where administration of antibiotics or endodontic treatment had prevented, reduced or eliminated inflammatory root resorption, 30–45% of the root surface area was ankylotic 8 wk after replantation.     

Orthodontic rehabilitation for anterior teeth lost due to trauma with crowding malocclusion

Abstract – Herein, we describe orthodontic management for an adolescent girl with traumatic loss of the upper central incisors and maxillary protrusion. The central incisors were immediately replaced and fixed with application of a semi‐rigid splint for 12 days, then endodontically treated. Severe root resorption and degeneration of periodontal tissue were noted after 4 years and the teeth were extracted, while the patient had also developed maxillary protrusion with severe crowding in the lower arch. The treatment objectives were to close the spaces by mesial movement of the buccal segment in the upper arch and eliminate crowding by extraction of the lower bicuspids. Favorable occlusion was achieved as was substitution with the lateral incisors for the lost central teeth.     

Delayed replantation of rat teeth after use of reconstituted powdered milk as a storage medium

Abstract – Minimal extraoral dry storage period and moist storage for the avulsed tooth are identified as key steps for the treatment protocol of tooth replantation. Among the possible moist storage media, bovine milk has stood out because of its capacity of preserving the integrity of the periodontal ligament (PDL) fibers. This condition has attracted the attention to investigate the use of powdered milk, which is one of the presentation forms of bovine milk, as a feasible storage medium in cases of delayed tooth replantation. The aim of this study was to evaluate the healing process after delayed replantation of rat teeth stored in reconstituted powdered milk and long shelf‐life (ultra high temperature) whole milk. Forty maxillary right rat incisors were assigned to four groups (n = 10): group I – the teeth were extracted and immediately replanted into theirs sockets; group II – the teeth were stored for 60 min in 200 ml of freshly reconstituted powdered milk; group III – the teeth were stored for 60 min in 200 ml of long shelf‐life whole milk; group IV – the teeth were kept dry for the same time. All procedures were performed at room temperature. Next, the root canals of teeth in groups II, III, and IV were instrumented, filled with a calcium hydroxide‐based paste, and replanted into their sockets. All animals received systemic antibiotic therapy and were killed by anesthetic overdose 60 days after replantation. The pieces containing the replanted teeth were removed, fixed, decalcified, and paraffin‐embedded. Semi‐serial 6‐μm‐thick sections were obtained and stained with hematoxylin and eosin for histomorphological analysis. There was statistically significant difference (P < 0.05) between groups I and IV regarding the presence of replacement resorption and PDL remnants on root surface. The powdered milk and long shelf‐life whole milk presented similar results to each other and may be indicated as storage media for avulsed teeth.     

The effects of topical application of bisphosphonates on replanted rat molars

Abstract – The purpose of this study was to evaluate the potential usefulness of two bisphosphonates (BPs) (etidronate and zoledronate), compared with that of alendronate, which is a well‐known drug for delayed replantation, in decreasing or preventing inflammatory root resorption and replacement root resorption in replanted teeth. Eighty‐four Sprague Dawley rat maxillary first molars were extracted, dried for 60 min and then replanted after root treatment. The rats were divided into four groups (control, alendronate, etidronate, zoledronate) as following treatments of avulsed root before replantation. At 7, 14, and 28 days postreplantation, the animals were sacrificed and the samples obtained and process for microscopic analysis. The data were statistically analyzed with the SPSS procedure, anova test and each test was complemented by the Tukey’s post hoc test. The result indicated that topical application of alendronate and zoledronate, both nitrogen containing BPs, prevented inflammatory root resorption and inflammatory cell response in the delayed replantation model. Both drugs were demonstrated similar effects in the delayed tooth replantation model (P = 0.9). Etidronate did not prevent inflammatory root resorption and inflammation in the delayed replantation (P < 0.05). No significant differences in replacement root resorption were observed among all drugs. These results suggest that when teeth are dried and not replanted immediately, zoledronate, like alendronate, may prevent root resorption and facilitates the regeneration of periodontal tissues after replantation.     

Root resorption after local injection of prostaglandin E2 during experimental tooth movement.

The purpose of this study was to investigate the occurrence of orthodontic root resorption in connection with local injection of prostaglandin E2 (PGE2). The material consisted of 25 male Wistar rats. The control group comprised six animals where no force was applied. In five animals 0.1 ml of 0.1 micrograms/microliter PGE2 was injected in the gingival area of the upper right first molar. In one animal no PGE2 was injected. The animals were killed after 3 days. The experimental tooth movement groups consisted of 19 animals. Duration of experiments was 3 days, 7 days, and 10 days. The maxillary first molars on both sides were each moved mesially by means of a coil spring. On the right side 0.1 ml of PGE2 0.1 micrograms/microliters was injected in the gingiva on the buccal side of the upper first molar on days 0, 3, 5, and 7. On the left side no injection of PGE2 was performed. In three animals in the 7-day group the vehicle (Waymouth medium) was injected. There was no significant difference in root resorption between the experimentally moved teeth with and without local injection of PGE2, but a trend towards more root resorption was registered on the teeth where such injections had been performed.