Proliferation of epithelial rests of Malassez following auto-transplantation of third molars: a case report

A Narrative and Case-Illustrated Review on Dental Autotransplantation Identifying Current Gaps in Knowledge

Background: Permanently replacing missing teeth in the younger population is a clinical challenge. However, dental autotransplantation offers a viable treatment option in this demographic. To be performed predictably, it requires proper diagnoses, planning, and adherence to established guidelines in a multidisciplinary approach. Such guidelines should use evidence-based dentistry to anticipate and limit complications. The aim of this study is to evaluate the current literature on dental autotransplantation, discuss an evidence-based protocol, highlight steps for minimizing complications, and present a case report on two autotransplantations conducted at the Graduate Periodontology clinic at the University of North Carolina at Chapel Hill, Adams School of Dentistry, in the context of representative cases. Methods: A literature search using PubMed was conducted with the goal of constructing a comparative table on both survival and success rates of autotransplantation, providing a comparison of protocols and clinical studies and informing this narrative review. This review is illustrated by cases with the intention to highlight critical steps, limitations, and strengths of this mode of treatment. Results and Conclusions: Given the information presented, it is concluded that autotransplantation is a valuable treatment option provided established guidelines are followed. It is particularly useful for the younger population where implants or other options are not appropriate or feasible. This study also highlights some of the gaps in knowledge in autotransplantation which present opportunity for further studies to be developed.

The ameliorating role of epithelial cell rests of Malassez in the alleviation of experimentally-induced periodontitis in rats

OBJECTIVE

The present study aimed to investigate the effect of experimentally-induced periodontitis on epithelial cell rests of Malassez (ERM) distribution and its subsequent role in regenerating periodontal ligament (PDL).

DESIGN

The study included 60 rats, aged seven months, randomly and equally divided into two groups: Group I, the control group, and Group II, the experimental group, in which ligature-periodontitis was induced. Ten rats from each group were euthanized at 1, 2, and 4 weeks. For ERM detection, specimens were processed for histological and immunohistochemical examination of cytokeratin-14. Additionally, specimens were prepared for the transmission electron microscope.

RESULTS

Group I demonstrated well-organized PDL fibers with few ERM clumps close to the cervical root portion. In contrast, one week after periodontitis induction, Group II showed marked degeneration, a damaged cluster of ERM cells, narrowing of the PDL space, and early signs of PDL hyalinization. After two weeks, a disorganized PDL was observed with the detection of small ERM clumps enclosing very few cells. After four weeks, PDL fibers were reorganized, and ERM clusters increased significantly. Notably, ERM cells were positive for CK14 in all groups.

CONCLUSION

Early-stage ERM may be affected by periodontitis. However, ERM is capable of recovering its putative role in PDL maintenance.

Cystic epithelial lining seen around a dental implant: A case report of a rare finding

Dental implants have been successfully used for over 30 years, with a low complication rate. Peri-implant pathologies have recently seen an increase in incidence. This case report elucidates a rare case implant failure that occurred shortly after prosthetic loading, where the clinical signs mimicked peri-implant disease and attending bone loss, but the final histological report confirmed presence of a cystic lining around the implant. The manuscript also emphasizes the possible causes and management of such complications. To the best of our knowledge, this represents one of the first publication of an evident peri-implant cystic lining in a case exhibiting no radiographic evidence of the same.

Autotransplantation of a Mandibular Third Molar: A Case Report with 5 Years of Follow-up

This paper describes the autologous transplantation of a mandibular right third molar to replace the residual roots of the second molar in the same quadrant, preserving function and aesthetics. A 5-year clinical and radiographic follow-up was undertaken. After transplantation, the donor tooth received endodontic treatment and placement of calcium hydroxide, which was periodically replaced every 3 months until the filling of the root canals, totalizing a period of 1-year, when apical closure was confirmed. The tooth was in perfect functional and aesthetic conditions 5 years after beginning of treatment. Autotransplantation is a feasible option for replacing missing teeth when a donor tooth is available. The autotransplantation of a right mandibular third molar with compromised function and aesthetics to replace the residual roots resulting from coronal destruction due to extensive carious lesion of the second molar in the same quadrant was a viable treatment alternative.

Epithelial cell rests of Malassez contain unique stem cell populations capable of undergoing epithelial-mesenchymal transition

The epithelial cell rests of Malassez (ERM) are odontogenic epithelial cells located within the periodontal ligament matrix. While their function is unknown, they may support tissue homeostasis and maintain periodontal ligament space or even contribute to periodontal regeneration. We investigated the notion that ERM contain a subpopulation of stem cells that could undergo epithelial-mesenchymal transition and differentiate into mesenchymal stem-like cells with multilineage potential. For this purpose, ERM collected from ovine incisors were subjected to different inductive conditions in vitro, previously developed for the characterization of bone marrow mesenchymal stromal/stem cells (BMSC). We found that ex vivo-expanded ERM expressed both epithelial (cytokeratin-8, E-cadherin, and epithelial membrane protein-1) and BMSC markers (CD44, CD29, and heat shock protein-90β). Integrin α6/CD49f could be used for the enrichment of clonogenic cell clusters [colony-forming units-epithelial cells (CFU-Epi)]. Integrin α6/CD49f-positive-selected epithelial cells demonstrated over 50- and 7-fold greater CFU-Epi than integrin α(6)/CD49f-negative cells and unfractionated cells, respectively. Importantly, ERM demonstrated stem cell-like properties in their differentiation capacity to form bone, fat, cartilage, and neural cells in vitro. When transplanted into immunocompromised mice, ERM generated bone, cementum-like and Sharpey's fiber-like structures. Additionally, gene expression studies showed that osteogenic induction of ERM triggered an epithelial-mesenchymal transition. In conclusion, ERM are unusual cells that display the morphological and phenotypic characteristics of ectoderm-derived epithelial cells; however, they also have the capacity to differentiate into a mesenchymal phenotype and thus represent a unique stem cell population within the periodontal ligament.

Histomorphological study of myelinated nerve fibres in the periodontal ligament of human canine

OBJECTIVE

This study aims to describe the human periodontal ligament (PDL) using serial sections, with a focus on mechanoreceptor distribution and morphology.

MATERIALS AND METHODS

One permanent lower canine with surrounding PDL and alveolar bone tissues was retrieved from a human cadaver. After being embedded into paraffin block, the canine was horizontally cut in 6 μm thick serial sections. At root levels of 0.3, 1.5, 3, 4.5 and 6 mm from the apex, five slices each level were evaluated. Immunocytochemisty was performed on the same serial sections, enabling a more reliable description of neural structures.

RESULTS

The distribution of myelinated fibres varied from apical to coronal level, with a total number of 38 at 0.3 mm from the apex, 25 at 1.5 mm, 25 at 3 mm, 31 at 4.5 mm and 32 at 6 mm. At all times, mesial and buccal regions were typically more densely innervated (p < 0.01) except at the 3 mm level. The average density of myelinated nerve fibres increased by arriving closer to the apex. However, the average diameter did not show any significant differences amongst quadrants or root levels (p > 0.05). The average diameter of myelinated fibres varied between 5.3-7.8 μm. Grouped myelinated axons were twice as common as isolated ones, with the innervation being rather close to the alveolar bone. Isolated myelinated axons showed a tendency to group around large blood vessels.

CONCLUSION

The present results add to the understanding of human PDL innervation, indicating dense innervations by myelinated nerve fibres in close proximity to collagen fibres and alveolar bone. It also reveals that apical as well as mesial and buccal sites of the human canine are more densely innervated.