Epithelial Rests Of Malassez Research Articles

Developmental relationship between junctional epithelium and epithelial rests of Malassez.

Keratin 17 (K17) is thought to be a candidate target gene for regulation by Lymphoid Enhancer Factor-1 (Lef-1). K17 is a marker that distinguishes junctional epithelium (JE) from epithelial rests of Malassez (ERM). However, the relationship of Lef-1 to K17 is not clear in this context. Moreover, the expression of other keratins such as K5, K6, K7 and K16 is not reported. Therefore, the aim of our study was to assay the expression of K5, K6, K7, K14, K16, K17 and Lef-1 in postnatal developing teeth, and clarify the corresponding immunophenotypes of the JE and ERM. Upper jaws of Wistar rats aged from postnatal (PN) day 3.5 to PN21 were used and processed for immunohistochemistry. K5 and K14 were intensely expressed in inner enamel epithelium (IEE), reduced enamel epithelium (REE), ERM and JE. There was no staining for K16 in the tissue, except for strong staining in the oral epithelium. Specifically, at PN3.5 and PN7, K17 was initially strongly expressed and then negative in the IEE. At PN16 and PN21, both REE and ERM were strongly stained for K17, whereas K17 was negative in the JE. In addition, K6, K7 and Lef-1 were not detected in any tissue investigated. REE and ERM have an identical keratin expression pattern before eruption, while JE differs from ERM in the expression of K17 after eruption. The expression of K17 does not coincide with that of Lef-1. These data indicate that JE has a unique phenotype different from ERM, which is of odontogenic origin.

MANAGEMENT OF AN INFECTED RADICULAR CYST OF THE MANDIBLE: A CASE REPORT

Among all odontogenic cysts, Radicular cyst is the most common inflammatory odontogenic cyst. They develop from epithelial rests of malassez in the PDL, as a result of inflammation. It is a true cyst that occurs in association with the root of the non-vital tooth. An inflammatory response occurs in the periapical tissue, leading to resorption of bone and formation of granulation tissue which are infiltrated by inflammatory cells. Though treatment of choice for smaller cystic lesions involves endodontic therapy, massive cystic lesions don't heal completely with non-surgical endodontic treatment. Massive cystic lesions need Endodontic treatment followed by surgical decompression treatment. In this case report, we present the diagnosis and surgical management of an infected radicular cyst of the mandible.

Semaphorin-RhoA signaling regulates HERS maintenance by acting against TGF-β-induced EMT.

Hertwig's epithelial root sheath (HERS) plays a role in root dentin formation. It produces the epithelial rests of Malassez (ERM) for the induction of periodontal tissue development during root formation. Although ERM is thought to be caused by epithelial-mesenchymal transition (EMT), the mechanism by which HERS is maintained as epithelium is unknown. Here, we aimed to elucidate the molecular mechanisms regulating the relationship between HERS maintenance and ERM development. To understand the relationship between HERS and ERM development during root formation, we observed the developing molar root using cytokeratin14 (CK14) Cre/tdTomato mice via stereomicroscopy. The relationship between semaphorin and transforming growth factor (TGF) signaling in the maintenance of HERS and ERM development was examined using CK14cre/R26-tdTomato mice and a HERS cell line. tdTomato-positive cells were observed on HERS and the migrating cells from HERS. The migrating cells showed reduced E-cadherin expression. In contrast, HERS cells expressed semaphorin receptors and active RhoA. Semaphorin signaling was associated with RhoA activation and cell-cell adhesion, while TGF-β induced decreased E-cadherin and active RhoA expression, and consequently enhanced cell migration. HERS induces root formation by controlling epithelial maintenance and EMT through the opposing effects of semaphorin and TGF-β signaling.

Unicystic Ameloblastoma - Case Report

Ameloblastoma is a slow-growing locally aggressive, benign odontogenic epithelium with a greater tendency for recurrence and involves aggressive bone loss and teeth. It is believed to be derived from cell rests of the enamel organ, either remnants of dental lamina or Hertwig's sheath, the epithelial rest of Malassez. The most common site of preference is the mandibular molar and ramus area than the anterior and premolar region. The article presents two case series of unicystic ameloblastoma of a 25 year female who had a localized swelling in the left side of the mandible which resembled a keratocystic odontogenic tumor clinically and radiographically. Based on histopathological examination the final diagnosis was unicystic ameloblastoma with the mural pattern. The second case report presented a 32-year female with a diffuse swelling in the left lower jaw which histopathologically revealed ameloblastoma with the plexiform variant. The case series presented certain unique features of female predilection and a multilocular variant with mural and plexiform pattern unicystic ameloblastoma. Both the patient was surgically managed more conservatively with enucleation and cauterization as cystic types are found to be less aggressive compared to solid variants of ameloblastoma. They were on a regular follow period postoperatively.

Nanoindentation and Atomic Force Microscopy Derived Mechanical and Microgeometrical Properties of Tooth Root Cementum

In the present research, nanoindentation, atomic-force microscopy and optical microscopy were used to study the mechanical and microgeometrical parameters of tooth tissues. A nanoindentation test unit equipped with Berkovich indenter was used to determine the values of the reduced Young’s modulus and indentation hardness and both nanoindentation and atomic force microscopy using a diamond probe on a silicon cantilever were used to study microgeometrical parameters of human tooth root cementum. Three areas of cementum were studied: the cervical region near the dentine–enamel junction, the second third of the tooth root, and the apex of the tooth root. The interpretation of the results was carried out using the Oliver–Pharr method. It was established, that the mechanical properties of cementum increase from the cervical region to the central part of the root, then decrease again towards the apex of the tooth root. On the contrary, the microgeometrical characteristics of cementum practically do not demonstrate any change in the same direction. A decrease in the roughness parameters in the direction from cellular cementum to dentine was observed. Additionally, a decrease in the reduced Young’s modulus and indentation hardness of dentine in the cervical area compared to dentine in the crown part of the tooth was found using nanoindentation. The investigation of the dentine–cementum junction with high resolution revealed the interspaced collagen fiber bridges and epithelial rests of Malassez, whose sizes were studied. The parameters of the topographic features of the cementum in the vicinity of the lacunae of cementocytes were also established.

PERIAPICAL CYST IN DENTAL HOSPITAL FACULTY OF DENTISTRY UNIVERSITAS INDONESIA 2018-2019 PERIOD

A periapical cyst is a lesion often found in dental practice. It is an odontogenic cyst of inflammatory origin with an epithelial wall originating from the epithelial rests of Malassez found in the periodontal ligament. Its high prevalence compared to other types of the odontogenic cyst and the absence of recent study of its distribution and frequency based on age, gender, tooth element, position, condition of the involved tooth, and its treatment render the need for further study. A retrospective descriptive study was done using the secondary data found in the patient's medical record. The study showed some patients with periapical cysts were at the Oral and Maxillofacial Surgery Department in the 2018-2019 period. The frequency and distribution of periapical cyst are primarily found in the third decade of life (39.1%). It found more in female patients (69.6%), more often involved maxillary lateral incisive (33.3%), mostly found at the apical of involved teeth (77.8%), involved teeth condition were more often pulp necrosis (63.0%), and endodontic treatment was the more chosen treatment (22.2%).

Constitutive Hedgehog/GLI2 signaling drives extracutaneous basaloid squamous cell carcinoma development and bone remodeling.

Uncontrolled activation of the Hedgehog (Hh) signaling pathway, operating through GLI transcription factors, plays a central role in the pathogenesis of cutaneous basal cell carcinoma and contributes to the development of several malignancies arising in extracutaneous sites. We now report that K5-tTA;tetO-Gli2 bitransgenic mice develop distinctive epithelial tumors within their jaws. These tumors consist of large masses of highly proliferative, monomorphous, basaloid cells with scattered foci of keratinization and central necrosis, mimicking human basaloid squamous cell carcinoma (BSCC), an aggressive upper aerodigestive tract tumor. Like human BSCC, these tumors express epidermal basal keratins and differentiation-specific keratins within squamous foci. Mouse BSCCs express high levels of Gli2 and Hh target genes, including Gli1 and Ptch1, which we show are also upregulated in a subset of human BSCCs. Mouse BSCCs appear to arise from distinct epithelial sites, including the gingival junctional epithelium and epithelial rests of Malassez, a proposed stem cell compartment. Although Gli2 transgene expression is restricted to epithelial cells, we also detect striking alterations in bone adjacent to BSCCs, with activated osteoblasts, osteoclasts and osteal macrophages, indicative of active bone remodeling. Gli2 transgene inactivation resulted in rapid BSCC regression and reversal of the bone remodeling phenotype. This first-reported mouse model of BSCC supports the concept that uncontrolled Hh signaling plays a central role in the pathogenesis of a subset of human BSCCs, points to Hh/GLI2 signaling as a potential therapeutic target and provides a powerful new tool for probing the mechanistic underpinnings of tumor-associated bone remodeling.

Epithelial rests of Malassez in experimental animals at different ages.

Epithelial rests of Malassez (ERMs) are fragments of Hertwig's sheath in the periodontal ligament. There is extensive knowledge of their role in the etiology ofpathological processes and current evidence links them to maintenance of periodontal homeostasis. The aim of this study was to assess the behavior of ERMs with relation to the changes in periodontal tissues during growth in an experimental model with Wistar rats. Mesiodistal sections were made of the first lower molars from Wistar rats aged 1 month (n=7), 3 months (n=7) and 5 months (n=6). Sections were stained with H&E to evaluate number of ERMs/ mm, size/area of ERMs (pm2), height of periodontal ligament (PL.h) (pm), area of cement in the furcation zone (C.Ar) (pm2) and bone area related to the ERM zone (BAr/TAr)(%). Posthoc Bonferroni and ANOVA were applied for statistical analysis of results. Number of ERMs/mm declined significantly with age (1m: 4.34±1.51, 3m: 1.48±0.89, 5m: 0.27± 0.50, p<0.05), and there was great variability in size. There was significant increase in C.Ar (1m: 3418.96 ± 905.88, 3m: 19365.76 ± 5500.52, 5m: 32182.76 ± 7114.51, p< 0.05) and interradicular (BAr/TAr) (1m: 25.26 ± 2.37, 3m: 44.70 ± 3.95, 5m: 46.81 ± 7.80, p< 0.05: 1 vs 3, 1 vs 5). There was significant decline in PLh at 5 months (1m: 141.42 ± 29.25, 3m: 162.06 ± 28.21, 5m: 124.72 ± 18.67, p< 0.05: 1 vs. 3, 3 vs. 5). The decline in number of ERMs as animal age increases may be related to the significant increase in C.Ar and reduction in PL.h. It remains to ascertain its relationship with the increase observed in BAr/ TAr. Further studies are needed to learn more about the role of ERMs and their relationship with periodontal tissues when confronted with different normal and pathological stimuli.

The two extremes of physiological tooth resorption in primary tooth with or without the permanent successor tooth

ABSTRACTIntroduction: Assessment of two radiographic images reveals two distinct, extreme situations of physiological tooth resorption, characteristic of primary teeth with or without permanent successor, due to partial anodontia. Discussion: In all primary teeth, rhizolysis begins after the completion of formation, thanks to the apoptosis of their cells. When apoptosis induced by cementoblasts has denuded the root of these cells, the process of rhizolysis inevitably begins: This will be accelerated by mediators arising from the pericoronal follicle. When there is no permanent successor due to partial anodontia, rhizolysis occurs extremely slowly, and months later, without the epithelial rests of Malassez that were dead due to apoptosis, alveolodental ankylosis becomes established, and the tooth will gradually be replaced by bone, still within a physiological context. Conclusion: Rhizolysis and physiological tooth resorption may occur rapidly or slowly, early or late, and this depends on the presence of the permanent tooth, or its absence due to partial anodontia.

Dental Roots: Formation, Lengthening and Malformations of Roots

The Hertwig’s Epithelial Root Sheath (HERS) includes two layers: the Outer Enamel Epithelial Root Sheath and the Inner Enamel Epithelium Epithelium (IEE and OEE). They contribute both to the root formation. The inner columnar epithelial cells (IEE) of the dental papilla are formed by cells located near the dental papilla. They are at the origin of odontoblasts expressing FGF-4, -8 and -9 and at later stages BMP-2 and BMP7. The Outer Epithelial cells (OEE) express SHH, Msx2, enamel matrix proteins, paxillin, and Pax-6. When the cells of the HERS dissociate, intercellular spaces enlarge. Cells migrate from the epithelial sac, and underwent phenotypic inter conversion into cementoblasts and later cementocytes. The Hertwigs enamel epithelium contributes to cementum formation. Epithelial rest of Malassez is remnants of the Hertwig’s root sheath. They are implicated in cementogenesis. Root lengthening and dentin thickening are involved in root elongation and dentin thickening to the detriment of the pulp chamber that is gradually reduced in volume. Apexogenesis and apexification contribute to root formation. Defects and abnormal root formation implicate missing teeth(hypodontia), orteeth in excess (supernumary teeth or hyperdontia) or mis-shapped structures. Genetic defects (Nfic, Ptc, Dkk1, Osx, Smad4, and Wls) have been identified. Premature arrests of root formation are due to apical infection, radiation, chemotherapy, as well as genes alterations. Roots malformations include root dilacerations which are abnormal curvature of the root and sharp bend of the crown or root axis. Taurodontism and other misshaped root structures are also frequently seen in man. Two main forms have been recognized: 1) the CLCN7 encoding a chloride channel, and 2) the second related to a defective PLG gene (encoding plasminogen). Altogether, theses defects contribute to major endodontic difficulties.

Primary Intraosseous Carcinoma of the Mandible: A Case Report

ABSTRACT&#x0D; Objective: To present a rare case of primary intraosseous carcinoma arising from the mandible and to discuss the ensuing course and the management of the patient.&#x0D; Methods: &#x0D; Design: Case Report&#x0D; Setting: General Tertiary Government Training Hospital&#x0D; Patient: One&#x0D; Result: A 56-year-old man consulted for a right mandibular mass of 4 months that started as a small bony swelling which gradually increased to its present size of 8 x 6 cm. Incisional biopsy revealed invasive squamous cell carcinoma and the patient underwent segmental mandibulectomy and bilateral selective neck dissection (levels 1 to 3). Final histopathologic findings revealed squamous cell carcinoma.&#x0D; Conclusion: Primary intraosseous carcinoma of the mandible was diagnosed since there was no overlying mucosal ulceration, other types of odontogenic carcinoma were ruled out, and no other distant primary tumor was noted from the time of examination until six months post-treatment.&#x0D; Keywords: primary intraosseous carcinoma; squamous cell carcinoma; odontogenic tumor; epithelial rest of Malassez; dental lamina

Techniques in the Safe Use of Polycaprolactone in Structural Rhinoplasty

ABSTRACT&#x0D; &#x0D; Objective: To present a rare case of primary intraosseous carcinoma arising from the mandible and to discuss the ensuing course and the management of the patient.&#x0D; &#x0D; Methods:&#x0D; Design: Case Report&#x0D; Setting: General Tertiary Government Training Hospital&#x0D; Patient: One&#x0D; &#x0D; Result: A 56-year-old man consulted for a right mandibular mass of 4 months that started&#x0D; as a small bony swelling which gradually increased to its present size of 8 x 6 cm. Incisional&#x0D; biopsy revealed invasive squamous cell carcinoma and the patient underwent segmental&#x0D; mandibulectomy and bilateral selective neck dissection (levels 1 to 3). Final histopathologic&#x0D; findings revealed squamous cell carcinoma.&#x0D; &#x0D; Conclusion: Primary intraosseous carcinoma of the mandible was diagnosed since there was no overlying mucosal ulceration, other types of odontogenic carcinoma were ruled out, and no other distant primary tumor was noted from the time of examination until six months post-treatment.&#x0D; &#x0D; Keywords: primary intraosseous carcinoma; squamous cell carcinoma; odontogenic tumor;&#x0D; epithelial rest of Malassez; dental lamina

Transcriptome analysis of ankylosed primary molars with infraocclusion

Primary molar ankylosis with infraocclusion can retard dental arch development and cause dental asymmetry. Despite its widespread prevalence, little is known about its molecular etiology and pathogenesis. To address this, RNA sequencing was used to generate transcriptomes of furcal bone from infraoccluded (n = 7) and non-infraoccluded (n = 9) primary second molars, all without succeeding biscuspids. Of the 18 529 expressed genes, 432 (2.3%) genes were differentially expressed between the two groups (false discovery rate < 0.05). Hierarchical clustering and principal component analysis showed clear separation in gene expression between infraoccluded and non-infraoccluded samples. Pathway analyses indicated that molar ankylosis is associated with the expression of genes consistent with the cellular inflammatory response and epithelial cell turnover. Independent validation using six expressed genes by immunohistochemical analysis demonstrated that the corresponding proteins are strongly expressed in the developing molar tooth germ, in particular the dental follicle and inner enamel epithelium. The descendants of these structures include the periodontal ligament, cementum, bone and epithelial rests of Malassez; tissues that are central to the ankylotic process. We therefore propose that ankylosis involves an increased inflammatory response associated with disruptions to the developmental remnants of the dental follicle and epithelial rests of Malassez.

Mandibular squamous odontogenic tumour misdiagnosed as squamous cell carcinoma: a case report and review of literature

Squamous odontogenic tumor (SOT) is an unusual, benign odontogenic tumor presented in close physical relationship to the dentition and originating from the epithelial rests of Malassez in the periodontal ligament or gingival epithelium. It was first described in 1975 by Pullon et al. and there are few cases reported in the literature. The main characteristic of this lesion is a tendency to arise in the molar region of the mandible and in the premolar-canine region of the maxilla with a simultaneously asymptomatic swelling in the alveolar. SOTs are incidental discoveries on routine dental radiographs or panoramic x-rays in many cases. We report a case of a 60-year-old Caucasian woman with SOT of the mandible in the area of the right premolars.

SURGICAL TREATMENT OF EXTENSIVE RESIDUAL CYST IN MANDIBLE: CASE REPORT

The residual cyst is the result of Malassez's epithelial rests stimulation due to an inflammatory process of pulp necrosis of a tooth already removed. The aim of this work is to report an extensive residual cyst enucleation in the mandible. A 62-year-old female patient presented with pain in the right side of the mandible. Extraoral examination showed a growth caused by the extensive bulging of the buccal cortex in the edentulous region corresponding from the canine to the right molars area. The image obtained by concomitant computed tomography showed unilocular, hypodense, and well-defined limits, with expansion and thinning of the buccal bone plate of the corresponding region. An aspiration was performed followed by incisional biopsy, whose histopathologically analyzed tissue corresponded to the conclusive diagnosis of residual cyst. After 8 months of enucleation, no signs of relapse were observed, and the prognosis is good. The residual cyst is the result of Malassez's epithelial rests stimulation due to an inflammatory process of pulp necrosis of a tooth already removed. The aim of this work is to report an extensive residual cyst enucleation in the mandible. A 62-year-old female patient presented with pain in the right side of the mandible. Extraoral examination showed a growth caused by the extensive bulging of the buccal cortex in the edentulous region corresponding from the canine to the right molars area. The image obtained by concomitant computed tomography showed unilocular, hypodense, and well-defined limits, with expansion and thinning of the buccal bone plate of the corresponding region. An aspiration was performed followed by incisional biopsy, whose histopathologically analyzed tissue corresponded to the conclusive diagnosis of residual cyst. After 8 months of enucleation, no signs of relapse were observed, and the prognosis is good.

THE ORIGINS OF ODONTOGENIC KERATOCYST BASED ON THE DISTRIBUTION OF MELANOCYTES

Objectives Melanocytes are pigmented-producing cells and derived from the neural crest. Melanin pigmentation is widely distributed in the skin and often in oral mucosa, but normally not existing in bone tissue. However, melanin pigmentation is detected on rare occasions with odontogenic lesions in the jaw bones, especially odontogenic keratocysts (OKC). Moreover, development of the tooth germ is originated from the neural crest, but elimination or expression of neural crest cells with odontogenic lesions is not obvious. The present study aimed to consider the origins of OKC based on the distribution of melanocytes in OKC. Findings One hundred and ten OKC were used. Eighty-eight cases showed sporadic type (SPO), and 22 cases involved basal cell nevus syndrome (BCNS). All samples were divided into 54 cases of juvenile group (0-29 years old) and 56 cases of advanced group (30-70 years old). Melanocytes were detected using Melan-A and HMB45 immunohistochemical stainings, and melanin pigmentation was detected using Schmorl's method. The positive rate of Schmorl's reaction, Melan-A and HMB45 staining were significantly higher in juvenile group than advanced group. These rates were also higher in BCNS than SPO. Conclusions Compare to juvenile and advanced groups, Melan-A and HMB45 positive rates were high in juvenile group. It is evident from these findings that the origin of OKC in juvenile group was different from advanced one. It means that the cyst epithelium in juvenile group originated from neural crest cell with melanocytes, and advanced one arose from odontogenic epithelium without melanocyte, for examples epithelial rest of Malassez.

A RECENT UPDATE ON HISTOGENESIS OF ADENOMATOID ODONTOGENIC TUMOR: A REVIEW

Adenomatoid odontogenic tumor (AOT) is a relatively rare benign, epithelial tumor of odontogenic origin. There is varying class of thoughts contemplating this lesion to be a hamartoma or neoplastic growth of odontogenic epithelium. Controversy regarding the histogenesis of the lesion is plentiful in earlier literature. The recent advent of immunohistochemical and ultrastructural studies has aided in throwing light on the tissue of origin of this tumor. This review aims at understanding the evolving concepts of histogenesis of AOT to better understand the biological behavior of the lesion. The review of AOT was carried out using PubMed and Google Scholar databases and 39 articles from the year 2001 to 2016 which contributed to the histogenesis of AOT were included for review. Since the origin of the cystic lining is similar to a reduced enamel epithelium and not the dental lamina, we propose the former to be the progenitor of AOT. Furthermore, we consider extra-follicular, as well as peripheral AOTs, originate from the remnants of Hertwig’s epithelial root sheath (epithelial rests of Malassez), which complies with the common histology for all these variants.

Isolation and characterization of cells derived from human epithelial rests of Malassez

The epithelial rests of Malassez (ERMs) might represent a valuable source of oral epithelial cells with stem cell properties. The purpose of this study was to isolate and characterize cells derived from human ERM, and compare them with cells derived from matched normal oral mucosa (NOM). Matched tissue specimens of the periodontal ligament of extracted tooth and NOM were collected. Cells were isolated in culture, then characterized by immunohistochemistry and flow cytometry for expression of pancytokeratin, ESA, PDGFRB, CD31 and CD44. 3D organotypic cultures were constructed by growing epithelial cells on top of fibroblast-populated collagen gels. Both ERM and NOM-isolated cells expressed the markers of epithelial lineage (ESA and pancytokeratin), and to some extent PDGFR, an indicator of a more mesenchymal phenotype, but not the endothelial cell marker CD31. Cells with epithelial morphology were isolated from periodontium of cervical, middle and apical parts of the root, but contained a significantly lower percentage of ESA and pancytokeratin-positive cells than when isolating cells from NOM (p < 0.001). ERM cells expressed a significantly higher percentage of the stem cell-related molecule CD44 (cervical 92.93 ± 0.25%, middle 93.8 ± 0.26%, apical 94.36 ± 0.41%) than cells isolated from NOM (27.8 ± 1.47%, p < 0.001). When grown in 3D organotypic cultures and in collagen gels, ERM cells formed a less differentiated epithelium than NOM cells, but expressing pancytokeratin and vimentin. In conclusion, epithelial cells could be isolated from human periodontium and grown in culture; their in vitro characterization indicates that they have a less differentiated phenotype compared with cells derived from normal oral epithelium.

Osteoprotegerin deficiency causes morphological and quantitative damage in epithelial rests of Malassez.

Epithelial rests of Malassez (ERM), the only odontogenic epithelial structures in periodontal tissue, are proposed to correlate with root resorption, but the detailed mechanism remains unclear. Osteoprotegerin (OPG), the main inhibitor of osteoclastogenesis, plays a pivotal role in inhibiting root resorption, and ERM cells express OPG mRNA in vitro. Thus, in this study, we aimed to clarify OPG expression in ERM in vivo and to explore the role of OPG in ERM to determine whether ERM are associated with root resorption via OPG. We established Opg-knockout (Opg-KO) mice and detected the OPG expression in ERM by immunohistochemical staining in 4-, 6-, 10-, 26- and 52-week-old mice. The ERM of wild-type (WT) mice and Opg-KO mice were evaluated histologically at 4, 10 and 26 weeks of age. Orthodontic root resorption models were established, maxillae were collected after 4weeks, and ERM were analysed by histomorphometric analysis. In our study, OPG displayed sustained expression in ERM, and OPG deficiency caused the destruction of ERM, characterized by irregular morphology and reduced numbers. Moreover, after orthodontic treatment, the loss of OPG severely damaged ERM, aggravating root resorption. Together, our results demonstrated that ERM expressed the OPG protein in vivo and that OPG deficiency resulted in morphological and quantitative damage to ERM. Furthermore, ERM may be associated with root resorption via OPG, thus helping to explain the mechanism underlying root resorption.

Epithelial rests of Malassez: from latent cells to active participation in orthodontic movement.

ABSTRACTIntroduction: The epithelial rests of Malassez (ERM) represent a group of cells in the periodontal ligament classically consisting of latent or quiescent structures associated with pathological processes. However, recent evidence shows that these structures cannot be considered only as cellular debris. The ERM is a major tissue structure, with functions in maintaining the homeostasis of periodontal tissue, including the maintenance of orthodontic movement. Objective:The present literature review aims at presenting the potential functions of ERM, with emphasis on orthodontic movement and the functional structure of the periodontium. Conclusion: ERM cells have a functional activity in modulation of orthodontic movement, trough their potential for differentiation, maintenance functions and the capacity of repairing periodontium.