Primary root resorption is a physiologic process that is followed by the exfoliation of the primary tooth to free the eruption pathway for the emergence of the successor tooth. The process of root resorption occurs with the help of odontoclasts which demineralize the hydroxyapatite crystals. During the exfoliation process, the pulp tissue of primary teeth undergoes several changes in terms of immune cell quantities and innervation. The periodontal ligaments of exfoliating primary teeth also show several changes including the fewer ECRM clusters and the reduced expression of OPG compared to healthy permanent teeth. This concludes that primary teeth show fewer protective factors against resorption which explains why primary teeth can undergo physiologic resorption while permanent teeth cannot.