Research progress on in vivo models for stem cell-based pulp regeneration

Basic research on pulp regeneration requires in vivo experiments. The PubMed database was searched for in vivo models of stem cell-based pulp regeneration using the following keywords: "pulp regeneration", "stem cell" and"animal model". The retrieved models were classified into ectopic, semiorthotopic and orthotopic regeneration models and their characteristics and clinical values were reviewed. This literature review indicated that the ectopic regeneration model is the most widely used model for the simple steps. However, this model does not accurately capture clinical situations. The semiorthotopic regeneration model, which is an improvement of the ectopic regeneration model, can create a more realistic regeneration environment. The orthotopic regeneration model can simulate clinical procedures that more closely resemble application, but it is less commonly used for difficult operations and long experimental periods. The applicability of the above three animal models depend on the stage of the animal experiment: the ectopic regeneration model is suitable to test the regenerative effect and biocompatibility of the implant complex; the semiorthotopic regeneration model is suitable to more persuasively evaluate the regeneration effect of the implant complex; and the orthotopic regeneration model is suitable to confirm the regeneration effect and practicability of the regenerative implant complex prior to clinical study.