Struys et al. Journal of Medical Case Reports 2010, 4:328 http://www.jmedicalcasereports.com/content/4/1/328 Page 3 of 5 Figure 2 Light microscopic images of epithelial rests of Malassez (ERM). (a-b) ERM of a normal human periodontal ligament with an average of 10 cells to 1 ERM. (c-d) ERM of a transplanted human periodontal ligament with an average of 20 cells to 1 ERM. osteoclasts which stimulate bone breakdown and bone remodelling [11]. Figure 3 Light microscopic image of the compartmentalization of collagen fibers that occurs after autotransplantation (arrow). In auto-transplantation, the alveolar bone around the implantation-site normally has to be remodeled to pro- vide a good fit for the implanted tooth. Bone breakdown is a process involved in this remodeling and it can be stimulated by increased prostaglandin E2 secretion by the ERM. This could explain why the ERM in the PDL of transplanted teeth are enlarged. It is also possible that the ERM in PDL of transplanted teeth remain enlarged when the remodeling process has finished. This implies that transplanted teeth will always have more mobility in the jaw than normal teeth because of the increased prostaglandin E2 secretion. In addition to the expected bone remodeling, the PDL also needs to be remodeled. The compartmentalization of the collagen bundles can be seen as a consequence of this process. Furthermore, following auto-transplantation, the need for re-innervation of the PDL is of significant value. As ERM play an important role in the distribution of the fibrous and neural elements in the PDL[12], the enlarge- ment of ERM detected after auto-transplantation could be