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Type: Thesis
Title: An immunohistochemical study of epithelial cell rests of malassez, incident to root resorption and repair
Author: Leedham, Mark David
Issue Date: 1992
School/Discipline: Department of Dentistry
Abstract: 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.
Advisor: Sampson, W. J.
Sims, M. R.
Dissertation Note: Thesis (M.D.S.)--University of Adelaide, Dept. of Dentistry, 1994
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