Histometric study of root resorption on human premolars following experimental replantation

A histometric method was applied for evaluation of root resorption in 57 experimentally replanted teeth and 22 controls. Representative axiobuccolingual sections were selected for measurement of resorptions at a magnification of x 40. The frequency of root resorption in the control teeth was low. In replanted teeth marked resorptive activity elicited by the trauma appeared after 2 wk. The extent of active resorptions increased until the third postoperative week. On an average 14% of the root periphery was affected at this stage. After the sixth postoperative week progressive cement deposition took place in the resorption lacunae. Incidental ankylosis of the periodontal membrane also occurred from this observation time but there was no increase among the long-term groups.     

Progression of root resorption following replantation of human teeth after extended extraoral storage

Abstract Avulsed human permanent teeth subjected to a minimum of 1 h dry extraoral storage before replantation were followed radiographically for an average of 4.8 years. The depth of root resorption cavities was assessed using a radiographic index, and the rate of root resorption was defined as the index change over time. The frequency of inflammatory and replacement resorption was determined at each observation time. Replacement resorption increased in frequency with time in all patients. In teeth endodontically treated within 3 weeks of replantation, minimal inflammatory resorption was found regardless of the age of the patients. In teeth where endodontic treatment was performed more than 3 weeks after replantation, the frequency of inflammatory resorption was significantly higher in young patients but not in older patients, up to more than 3 years after replantation. The rate of root resorption was found to be related to age. In patients 8–16 years old at the time of avulsion the rate of root resorption was significantly higher compared with patients 17–39 years old. Age had a higher impact on the rate of root resorption compared with the delay in endodontic treatment after replantation. It was concluded that a tooth replanted with a necrotic periodontal membrane will become ankylosed and resorbed within 3–7 years in young patients, whereas a tooth replanted under similar conditions in older patients may remain in function for a considerably longer time.     

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。     

Emdogain® does not prevent progressive root resorption after replantation of avulsed teeth: a clinical study

Abstract –  Emdogain^® has been shown in clinical and experimental studies to promote regeneration of all periodontal tissues: cementum with anchoring fibres, a functional, periodontal ligament and alveolar bone in connection with treatment of marginal periodontitis.
The intention of this study was to analyse whether this regenerative capacity upon the periodontal ligament also worked in a trauma situation where a significant number of PDL cells have been eliminated because of unphysiologic storage or actual damage during avulsion or replantation. Furthermore if ankylosis sites already established because of earlier replantation after avulsion could be surgical removed and application of Emdogain^® could revert the ankylosis stage to a normal PDL situation. The first treatment situation was tested in seven patients with a total of 16 avulsed teeth with varying time of extra oral storage. The teeth were extra-orally endodontically treated and the root and socket covered with Emdogain^® before replantation. All teeth demonstrated subsequent ankylosis, primarily diagnosed by a percussion test. The second treatment situation where an ankylosis was already established constituted of seven patients with a total of 11 teeth because of previous replantation after avulsion. These teeth were all extracted, the ankylosis sites removed and the root and socket treated with Emdogain^®. After 6 months all teeth showed recurrence of ankylosis. It is concluded that Emdogain^® was not able to prevent or cure ankylosis.     

The effect of intracanal Ledermix on root resorption of delayed-replanted monkey teeth

Abstract – Progressive root resorption is one of the common sequelae in replanted teeth, which is detrimental to their long‐term prognosis. Ledermix paste, with its composition of triamcinolone acetonide and demethylclortetracycline, has been shown to inhibit inflammation and the associated hard tissue resorption. This study evaluated the effect of immediate intracanal Ledermix on root resorption of delayed‐replanted monkey teeth. A total of 36 roots were root canal treated. For the experimental group, intracanal Ledermix was placed prior to extraction and replantation after 1‐h bench dry. The positive control group was root filled and replanted after 1 h while the negative control group was root filled and replanted immediately. The monkeys were sacrificed after 12 weeks. The H&E histological tissue specimens were prepared and evaluated using a method modified from that of Andreasen's morphometric analysis, as favorable or complete healing and unfavorable healing, comprising inflammatory root resorption and replacement resorption. The results were analyzed using Kruskal–Wallis and Mann–Whitney U‐tests as well as Wilcoxon signed ranks test. The negative control group produced highly significant favorable healing and unfavorable healing as compared to the Ledermix group (P = 0.000). The Ledermix group only showed significantly higher occurrence of complete healing (35.46%) compared to the positive control group (16.58%) (P = 0.037) but there were no significant differences in the inflammatory root resorption and replacement resorption. Nevertheless, when the latter two unfavorable healing patterns were combined, there was a significantly lower overall unfavorable healing in the Ledermix group (64.54%) when compared to the positive control group (83.43%) (P = 0.037). This unfavorable healing outcome in the Ledermix group, however, was not significantly different from the favorable healing outcome with the same treatment modality (P = 0.110).     

人牙周膜成纤维细胞来源外泌体对大鼠延期牙再植术后牙根吸收的调控作用

目的: 探讨健康的人牙周膜成纤维细胞（hPDLFs）来源外泌体对大鼠延期牙再植术后牙根吸收的作用及其可能机制。方法: 分离提取hPDLFs来源的外泌体并鉴定。选择30只6周龄雄性SD大鼠,随机分为对照组和外泌体组,建立上颌第一磨牙延期牙再植术模型,牙脱位30 min后植回牙槽窝。对照组牙周膜局部注射40 μL汉克斯平衡盐溶液（HBSS）,实验组牙周膜局部注射40 μL含外泌体的HBSS。术后1、2、4周收样,苏木精-伊红（H-E）染色观察牙根表面吸收陷窝,抗酒石酸酸性磷酸酶（TRAP）染色观察破骨细胞数量,免疫组织化学染色观察牙周膜内骨保护素（OPG）的表达。采用SPSS 17.0软件包对数据进行统计学处理。结果: 鉴定表明提取的细胞外囊泡为外泌体。与对照组相比,hPDLFs来源的外泌体减少了延期牙再植术后牙根吸收陷窝的数量,降低TRAP阳性破骨细胞的表达（P<0.05）,促进牙周膜内OPG的表达（P<0.05）。结论: 延期牙再植术后,hPDLFs来源的外泌体减少了破骨细胞的数量,促进牙周膜内OPG表达,减少了再植术后的牙根吸收。     

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.     

Evaluation of statistics and desirable experimental design of a histomorphometrical method for studies of root resorption

Abstract This study characterizes how the accuracy and precision of estimates of the true extent of root resorption are influenced when measuring serial-sectioned individual teeth; different types of teeth with different degrees of resorption, sampling different numbers of sections and registration points. Maxillary and mandibular central and lateral incisors can be used for studies of root resorption with this method. Eight points of registration were required for every section when smaller differences in the means of root resorption between experimental groups were expected. When comparing groups with extensive differences, 4 points of registration were enough. The points should be labial, lingual, mesial and distal. Ten to 17 sections per tooth seemed to be sufficient in most instances. The number of experimental animals needed depended on the statistical procedures and expected outcome of the experiment.     

新型无磨料牙膏对聚甲基丙烯酸甲酯树脂表面性能影响的研究

 目的　研制新型无磨料牙膏，并评估其对聚甲基丙烯酸甲酯（polymethyl methacrylat，PMMA）树脂表面性能的影响。方法　在新型牙膏中去除磨料并调整表面活性剂和湿润剂的比例，对10种新型牙膏的性状进行评估；选择较佳性状的2种新型牙膏（新型牙膏A组和新型牙膏B组）与市面牙膏（市面牙膏A组和市面牙膏B组）、市面泡腾片（市面泡腾片组）及蒸馏水（对照组）对PMMA树脂片进行清洁处理，比较各组清洁前后PMMA树脂片表面光密度（OD）值及粗糙度（Ra）值，评估各类清洁剂对PMMA树脂表面清洁效果及磨损水平。结果　10种新型牙膏中2号（新型牙膏A组）和6号（新型牙膏B组）具有较佳的性状，其pH值分别为7.18和7.22，并用于后续研究。（1）清洁效果：对照组清洁处理前后PMMA树脂片菌斑红染及OD值基本无明显变化，差异无统计学意义（P > 0.05），其余各组清洁处理后的PMMA树脂片菌斑红染程度较清洁处理前明显降低，OD值也显著下降，差异有统计学意义（均P < 0.05），尤其以市面泡腾片组、新型牙膏A组和新型牙膏B组清洁效果最为显著。（2）磨损水平：体视显微镜观察发现，清洁处理后，对照组PMMA树脂片表面光滑无划痕；市面牙膏A组和市面牙膏B组PMMA树脂片表面划痕较深且划痕数量较多，Ra值也明显增大，差异均有统计学意义（均P < 0.05）；市面泡腾片组、新型牙膏A组和新型牙膏B组PMMA树脂片表面仅出现轻微细小浅划痕，Ra值略微升高，但其差异均无统计学意义（均P > 0.05）。结论　新型无磨料牙膏在有效清除菌斑软垢的同时可减少PMMA树脂表面划痕，可成为临床义齿清洁牙膏。     

Timing of calcium hydroxide therapy in the treatment of root resorption in replanted teeth in dogs

Abstract The effect of time of the onset of calcium hydroxide (CH) pulpectomy on root resorption of 31 permanent dog incisors was investigated. CH pulpectomy was delayed 4, 9, 14 and 18 days after the teeth were extracted and replanted. Control teeth were replanted 1) without pulpectomy, 2) with a pulpectomy only or 31. with a pulpectomy and CH filling. All teeth were prepared for histologic evaluation 8 weeks after the teeth were replanted. Cross section were examined using a computer microscope and linear (jam) and/or square areas (μm²) of surface (SRR), inflammatory (IRR), and replacement (RRR) root resorption were calculated. From this data the percentage of linear and area resorption was averaged for each group. Duncan multiple range t-test (P<0.05) revealed that teeth in which a pulpectomy with CH filling was done extraorally had significantly greater SRR than the rest of the groups; teeth in which a pulpectomy without CH filling was done extra orally had significantly greater RRR than teeth in which CH pulpectomy was delayed for 18 days; there was no significant difference in SRR. IRR or RRR when CH placement was delayed 4, 9, 14 or 18 days after replantation. Although it was not significant the overall resorption was least when CH pulpectomy was delayed 18 days.     

Effect of bisphosphonates and gallium on dentin resorption in vitro

Abstract Replacement resorption may follow the replantation of an avulsed tooth. Currently there is no effective treatment for replacement resorption. The purpose of this study was to investigate the effect of bisphosphonates and gallium nitrate, which have been shown to reduce bone resorption, on cells which resorb dentin. Osteoclast-like cells were obtained by culturing cells from prenatal chick tibeas. These cells were seeded onto slices of human dentin which had been soaked in either saline (control), or solutions of 10^–5 M 1-hydroxyethylidene-1, 1-bisphosphonic acid (EHBP), 10^–6 M dichloromethylene bisphosphonic acid (Cl₂MBP), or 10^–6 M gallium nitrate. Resorption was measured by counting the number of resorptive lacunae produced by the cells. Results indicated that the experimental groups did not differ significantly from each other, but each exhibited significantly reduced resorption compared with saline controls (p<0.01). These results suggested that the experimental treatment reduced dentinal resorption by the osteoclast-like cells, and that these agents might be useful to prevent or at least postpone replacement resorption in avulsed teeth.     

Incidence and severity of root resorption in orthodontically moved premolars in dogs

OBJECTIVES: To study treatment-related factors for external root resorption during orthodontic tooth movement. DESIGN: An experimental animal study. SETTING AND SAMPLE POPULATION: Department of Orthodontics and Oral Biology, University Medical Centre Nijmegen, The Netherlands. Twenty-four young adult beagle dogs. EXPERIMENTAL VARIABLE: Mandibular premolars were bodily moved with continuous or intermittent controlled orthodontic forces of 10, 25, 50, 100, or 200 cN according to standardized protocols. At different points in time histomorphometry was performed to determine the severity of root resorption. OUTCOME MEASURE: Prevalence of root resorptions, defined as microscopically visible resorption lacunae in the dentin. Severity of resorption was defined by the length, relative length, depth, and surface area of each resorption area. RESULTS: The incidence of root resorption increased with the duration of force application. After 14-17 weeks of force application root resorption was found at 94% of the root surfaces at pressure sides. The effect of force magnitude on the severity of root resorption was not statistically significant. The severity of root resorption was highly related to the force regimen. Continuous forces caused significantly more severe root resorption than intermittent forces. A strong correlation (0.60 < r < 0.68) was found between the amount of tooth movement and the severity of root resorption. CONCLUSIONS: Root resorption increases with the duration of force application. The more teeth are displaced, the more root resorption will occur. Intermittent forces cause less severe root resorption than continuous forces, and force magnitude is probably not decisive for root resorption.     

A case of progressive external root resorption

Abstract This case report describes a radiographical, histological and histochemical study of an extracted mandibular tooth with progressive external root resorption. The cells which appeared to be responsible for the hard tissue resorption showed an intense acid phosphatase activity, similar to that of bone-resorbing cells. Some aspects on the etiology and pathogenesis of resorptive process that occurred in the present case are discussed.     

Cervical external root resorption in vital teeth

External resorptions associated with inflammation in marginal tissues present a difficult clinical situation. Many times, lesions are misdiagnosed and confused with caries and internal resorptions. As a result inappropriate treatment is often initiated. This paper provides three-dimensional representations of cervical external resorption, based on X-ray microfocus-tomographical scanning of a case, which will aid the dental practitioner in recognizing characteristic features during clinical inspection. In addition, histopathological examination reveals the cellular morphology of the adjacent tissues.     

多西环素对大鼠正畸移动牙根吸收影响的研究

目的：建立正畸牙根吸收动物模型,研究多西环素（DOXY）对根吸收组织的影响。方法：选用SD大鼠36只建立正畸牙移动根吸收动物模型,随机分为空白对照组（A组）、注射DOXY对照组（B组）、正常牙加力组（C组）、注射DOXY加力组（D组）。在加力的0、7、10、14 d分别处死各组大鼠。并取相应时段的标本制作组织切片,进行HE染色和TRAP染色,检测多西环素对根吸收组织的影响。用计算机图像分析技术定量比较上述实验结果。结果：①在所有实验周期内（除第14 d）,D组根吸收明显少于C组（P＜0．05）。 D组根吸收的平均值缓慢增加,而C组14 d时显示减少。②C组、D组牙根面的TRAP阳性细胞数均在第10 d到达峰值,第14 d开始下降。然而D组在受力10 d后根面的TRAP阳性细胞数明显少于C组（P＜0．05）。结论：多西环素可能对正畸牙根吸收及破骨细胞的募集有抑制作用。     

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.     

Use of hydroxyapatite in tooth replantation radiographically followed up for 14 years: a case report

Abstract –  A lateral incisor was replanted 4 h after trauma. The tooth subsequently developed external root resorption treated with calcium hydroxide initially and with a hydroxyapatite root filling subsequently. Radiographs of the replanted tooth were obtained to follow up the patient for 14 years.