Academic literature on the topic 'Epithelial cell rests of malassez'

The aim of this study is to present a classification with a clinical application for root resorption, so that diagnosis will be more objective and immediately linked to the source of the problem, leading the clinician to automatically develop the likely treatment plan with a precise prognosis. With this purpose, we suggest putting together all diagnosed dental resorptions into one of these four criteria: 1) Root resorption caused by cementoblast cell death, with preservation of the Malassez epithelial rests. 2) Root resorption by cementoblasts and Malassez epithelial rests death. 3) Dental resorption by odontoblasts cell death with preservation of pulp vitality. 4) Dental resorption by direct exposure of dentin to gingival connective tissue at the cementoenamel junction gaps.

Bibliography: leaves 107-117. Describes research which set out to study the distribution of the epithelial rests of Malassez (ERM) and blood vessels in the peridontal ligament (PDL) of the first molar root in developing rat teeth. ERM were originally thought to be fuctionless but are now believed to not only play a role in dental cyst formation, but may also protect against root resorption.

The role of the epithelial cell rests of Malassez in the periodontal ligament has not yet been clarified. The epithelial cell rests have been suggested to have a role, amongst other possible suggestions, in the prevention of ankylosis and the maintenance of the periodontal space. (LOE and WAERHAUG 1961; LINDSKOG et al. 1988B). The presence of the epithelial cell rests in association with resorption as a result of orthodontic treatment was first demonstrated by BRICE (1988), and BRICE et al. (1991). The presence of rests in association with the repair of experimental root resorption in Macaca fascicularis has also been demonstrated (LEEDHAM 1990). These recent studies required the use of the transmission electron microscope to positively identify the tonofilaments and desmosomes that are characteristic of epithelial cells. The present study has sought to develop and apply light microscope methods in association with immunohistochemical techniques to label epithelial cells of the human periodontal ligament. An initial study used premolar teeth from patients undergoing orthodontic treatment that were collected and fixed according to several fixation schedules and decalcified in EDTA. After embedding in parafin with celloidin, sections were stained using polyclonal antibodies to cytokeratin. The primary antibodies were visualized using anti-rabbit secondary antibodies, and the strept-avidin-biotin method and diaminobenzidine. The sections were dehydrated, counter-stained with haematoxylin, coverslipped, and viewed in the light microscope. This preliminary study demonstrated that fixation in 4o/o formalin for 6 hours and decalcification by EDTA, in a cacodylate buffer, was sufficient to enable positive identification of epithelial cells. The method was able to show epithelial cell rests of Malassez along both resorbed and non-resorbed surfaces of the teeth studied. Some examples of epithelial cells within the body of larger resorptive defects were also seen. The second part of the study used the above methods, except for the substitution of a monoclonal antibody (AE1/3) in place of the polyclonal antibody used in the preliminary study, in an histomorphometric study using adolescent human premolar teeth' The study aimed to quantify the extent of root resorption, and the relationship to epithelial cells as a result of rapid maxillary expansion. Using the previously developed methods, extracted premolar teeth that had been used as anchor teeth in RME patients were collected. These teeth were fixed and decalcified as described. Each tooth root was completely divided into 5um sections, and sections were selected at 10 equidistant levels (level 0 to level 10) from the cemento-enamel junction to apex. Each of these levels was then stained according to the immunohistochemical protocols, and counter-stained with haemotoxylin. Using histomorphometric methods adapted from ANDERSSON et al' (1987) and ANDREASEN (1987), a section from each level was selected, viewed using an octant system, data collected about resorption, epithelial cell rests, blood vessels, and amount of tissue remaining, and the information entered into a spreadsheet, and analysed by the University of Adelaide Vax computer. The results in this part of the study confirmed the reliability of the immunohistochemical staining methods. The cell rests were clearly visible, although there was considerable variation in their shape and morphology, even in the control teeth. Both control and experimental teeth suffered from the loss of considerable amounts of tissue, limiting the analysis. The analysis did quantify the large amounts of buccal root resorption as a result of the treatment, and the continued presence of epithelial cell rests on all root surfaces a"fter treatment. The cell rests were more numerous in the cervical region, decreasing to the middle levels, and increasing again as the apex was approached. Other parameters could not be statistically examined due to the lack of tissue. Only a few examples of epithelial tissue in the areas of repairing resorption were seen. This may have been as a result of the timing of the extractions which took place well after the RME therapy and repair was well advanced. The small sample size also restricts the interpretation. The loss of soft tissue from areas of resorption means that many areas of potential interest were lost from examination. In conclusion, alveolar bone needs to be collected as part of the experimental procedure in order to more completely describe the events occuring as a result of orthodontic resorption. The timing of the repair events appears to be crucial with epithelial cells perhaps an early indicator of repair. Further studies using an animal model may offer more scope for investigating this aspect as well as the potential to build up three dimensional pictures of the periodontal ligament. The immunohistochemical techniques developed can also be adapted to identify and locate other components of the periodontal ligament.<br>Thesis (M.D.S.)--University of Adelaide, Dept. of Dentistry, 1994

Stem cells represent promising candidates for tissue engineering due to their capacity for self-renewal and their potential for differentiating into multiple cell lineages. The periodontal tissues are composed of various cell types, such as periodontal ligament fibroblasts, osteoblasts, cementoblasts, endothelial cells, the Epithelial Cell Rests of Malassez (ERM). Studies have previously identified periodontal ligament stem cells (PDLSC) within these tissues, which have the capacity to form periodontal ligament, cementum and bone. Another potential source of progenitor cells described in periodontal tissues are ERM, which are the only odontogenic epithelial cells in the adult periodontium. The present study identified that ERM contained a unique multipotential stem cell population with similar properties as described for PDLSC. Furthermore, the present proposal investigated the cell surface protein expression of PDLSC to identify unique markers for the isolation and purification of PDLSC. The present study demonstrated that ovine Epithelial Cell Rests of Malassez contain a subpopulation of stem cells that could undergo epithelial-mesenchymal transition into mesenchymal stem-like cells with multi lineage potential. Ex vivo-expanded ERM expressed both epithelial (cytokeratin-8, E-cadherin and Epithelial Membrane Protein-1) and bone marrow stromal/stem cell markers (CD44, CD29, Heat Shock Protein-90β). Integrin α₆/CD49f could be used for the enrichment of clonogenic cell clusters (colony-forming units-epithelial cells [CFU-Epi]) which was weakly expressed by PDLSC. Importantly, ERM demonstrated a capacity to differentiation into bone, fat, cartilage and neural cells in vitro, and form bone, cementum-like and Sharpey’s fibre-like structures when transplanted into immunocompromised mice. Additionally, gene expression studies showed that osteogenic induction of ERM triggered an epithelial-mesenchymal transition. The present study also examined the cell surface protein expression of human PDLSC using CyDye cell surface labelling and two-dimensional electrophoresis coupled with liquid chromatography--electrospray-ionization tandem mass spectrometry. In addition to the expression of well known mesenchymal stem cell associated cell surface antigens such as CD73 (ecto-5'-nucleotidase) and CD90 (Thy-1), PDLSC were also found to express two novel cell surface proteins, Annexin A2 and sphingosine kinase 1. Interestingly, previous studies have implicated CD73, CD90, Annexin A2 and sphingosine kinase 1 expression in the maintenance of various stem cell populations. Comparative analyses investigated the expression of CD73, CD90, Annexin A2 and sphingosine kinase-1 in human gingival fibroblasts, human keratinocytes, ovine PDLSC and ovine ERM cells. Importantly, this study found that human skin epithelial cells lacked any cell surface expression for CD73, CD90 and Annexin A2. In summary, ERM and PDLSC are both important stem cell sources that could play a pivotal role in periodontal homeostasis and regeneration following insult or disease. As periodontal regeneration is essentially a re-enactment of the periodontal tissue development process, it is plausible to suggest that the combination of ERM and PDLSC would hold greater potential for periodontal regeneration compared to established bone marrow-derived mesenchymal stem cells.<br>Thesis (Ph.D.) -- University of Adelaide, School of Dentistry, 2012

The current study investigated the distribution of periodontal epithelial cells and nerve fibres within the furcations of rat maxillary molar teeth subjected to hypothermic injury. The upper right first molars of 30 Sprague-Dawley rats were subjected to a single 20 minute application of dry ice in order to produce aseptic necrosis within the periodontal ligament, while the contralateral first molar served as an untreated control. Five animals were each sacrificed via cardiac perfusion after 7, 10, 14, 18, 21 and 28 days respectively and the maxillae were dissected out. After fixation in paraformaldehyde and processing, the tissues were embedded in paraffin wax and cut into 7µm serial coronal sections through the furcation region. Consecutive sections were then stained with H&E, cytokeratin AE1/AE3 and PGP 9.5 immunostains. Light microscopic examination of the H&E stained sections revealed that ankylosis had not developed in all of the experimental teeth, and in some of the observation groups fewer teeth were ankylosed than unaffected. The morphology of the ankylotic areas appeared to change with time, initially consisting of fine bony trabeculae, then progressing to solid bone occupying the entire furcation before becoming less solid again by the latest observation periods. Root resorption was often seen adjacent to areas of ankylosis, but the cementum of the tooth root at the point of ankylotic union was usually intact and free of resorption. Changes within the pulp chambers of the experimental teeth were also noted, with reduction in cellularity and tissue disorganisation initially, then increasing cellularity and formation of a cementum-like material on the chamber walls later. Cytokeratin AE1/AE3 immunostaining successfully identified epithelial cells within the periodontal ligament and their distribution around control teeth was similar to previous reports. Counting of these cells revealed lower numbers around experimental teeth, with the lowest counts around experimental teeth which had developed ankylosis. No change in the epithelial cell counts was detected over time, and these cells did not appear to regenerate after necrosis regardless of whether or not ankylosis developed. Statistical analysis indicated that the probability of ankylosis decreased as the number of epithelial cells increased. The PGP 9.5 immunostain identified periodontal nerve fibres, but the use of this stain was quite technique sensitive. The furcations of the molar teeth were noted to have relatively sparse innervation, with most of the visible nerve fibres being closely associated with blood vessels and located in the outer two-thirds of the ligament. Counting of the nerve fibres revealed fewer fibres around experimental teeth compared to control teeth, especially in the part of the ligament closest to the tooth root. There was no relationship detected between nerve count and time or between nerve and epithelial cell counts. Resorption was found to be more prevalent in experimental teeth, and the probability of resorption in a given tooth decreased as the epithelial cell count increased. The findings of this study suggest that the epithelial cells within the periodontal ligament have a protective function in the prevention of dentoalveolar ankylosis and resorption. Evidence of an intimate interrelationship between periodontal nerve fibre and epithelial cell numbers could not be confirmed. The null hypothesis that epithelial cell rests of Malassez do not provide a protective function against ankylosis and external root resorption was rejected, and the null hypothesis that nerve fibres and epithelial cells are not inter-dependent was retained.<br>http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297409<br>Thesis (D.Clin.Dent.) -- School of Dentistry, 2007

Uncertainty as to the role of the epithelial remnants from cementogenesis has been discussed in the literature since these cells were first described over one hundred years ago. Among the possible functions suggested has been a role in healing of root resorption. This study has been undertaken to establish an economical technique for producing useful three dimensional reconstructions of human periodontal ligament and attempts to determine the relationship of epithelial rests of Malassez with orthodontic root resorption to clarify any potential function. Root resorption was produced on the buccal surfaces of human premolars following rapid maxillary expansion therapy. These teeth were extracted and processed for both electron and light microscopy. The work of Brice (1988) found conclusively that epithelial cells are found in repairing resorption lacunae from his ultrastrutural investigations. This work added credence to the belief that epithelial cells may play a role in protecting the tooth from, or at least limiting the progress of root resorption by initiating cementogenesis. The present study involved reconstructing 1 micron serial sections of human periodontal ligament with 3-D computer programmes. These reconstructions enabled a protocol for the production of serial sections of human periodontal ligament to be established. Digitized sections were processed on two independant IBM based reconstruction programmes to determine the most visually useful image system for interpretation. The electron micrographs and three dimensional images produced confirmed the presence of epithelial cells in the proximity of regions of active and repairing resorption. The continuity of these cells was confirmed, and their relationship to blood vessels and tooth described in regions with different degrees of resorptive activity. The possibility of epithelial cells in limiting the degree of root resorption is discussed. Technical difficulties in producing computer generated three dimensional images were discussed and future directions outlined.<br>Thesis (MDS) -- University of Adelaide, Dept. of Dentistry, 1991

Describes research which set out to study the distribution of the epithelial rests of Malassez (ERM) and blood vessels in the peridontal ligament (PDL) of the first molar root in developing rat teeth. ERM were originally thought to be fuctionless but are now believed to not only play a role in dental cyst formation, but may also protect against root resorption.<br>Thesis (M.D.S.) -- University of Adelaide, Dental School, 2001.

Odontogenic cysts and tumours arise from inclusion of tooth-forming epithelium and mesenchyme in the jaw bones during development. Cysts also arise from non-odontogenic epithelium trapped during fusions or from vestigial structures. In addition, bone cysts that can arise at other skeletal sites may also occur in the jaws. Odontogenic cysts and tumours may be classified according to their putative developmental origins and biology. The classification of jaw cysts is shown in Fig. 6.1. Odontomes are hamartomatous develop­mental lesions of the tooth-forming tissues. Odontogenic tumours are uncommon and are usually benign. Ameloblastoma is the most com­mon odontogenic tumour and is described in detail. The other odon­togenic tumours are rare and only the principal features are presented. Very rare congenital lesions of possible odontogenic origin are men­tioned in the final section. A cyst may be defined as pathological cavity lined by epithelium with fluid or semi-fluid contents. However, clinically, the term encompasses a broader range of benign fluid-filled lesions, some of which do not possess an epithelial lining. The preferred definition is, therefore, ‘a pathological cavity having fluid or semi-fluid contents that has not been created by the accumulation of pus’. Cysts are commonly encountered in clinical dentistry and are generally detected on radiographs or as expansions of the jaws. Most cysts have a radiolucent appearance and are well circumscribed, often with a corticated outline. At least 90% of jaw cysts are of odontogenic origin. The clinico-pathological features of jaw cysts are summarized in Table 6.1. The incidence of the four most common jaw cysts are provided in Table 6.2. The epithelial lining of odontogenic cysts originates from residues of the tooth-forming organ. • Epithelial rests of Serres are remnants of the dental lamina and are thought to give rise to the odontogenic keratocyst, lateral periodon­tal, and gingival cysts. • Reduced enamel epithelium is derived from the enamel organ and covers the fully formed crown of the unerupted tooth. The dentiger­ous (follicular) and eruption cysts originate from this tissue, as do the mandibular buccal and paradental cysts. • Epithelial rests of Malassez form by fragmentation of Hertwig’s epi­thelial root sheath that maps out the developing tooth root. Radicular cysts originate from these residues.