Orthodontically induced apical root shortening: a multilevel analysis of anatomical vulnerabilities, cellular crosstalk, and molecular regulation

Orthodontically induced apical root shortening (OI-ARS) poses a significant clinical challenge, characterized by asymptomatic yet progressive resorption of apical hard and soft tissues, ultimately leading to irreversible root structure loss. Despite its clinical prevalence, the mechanistic underlying of OI-ARS remains poorly understood, with current research predominantly focused on the extensive resorption of dental tissues by osteoclasts rather than apical-specific pathobiology. Additionally, several terminologies have emerged to characterize OI-ARS. However, conceptual ambiguities persist, particularly in distinguishing between reversible cemental remodeling and irreversible apical root shortening. This review systematically examines OI-ARS through an integrative anatomical-cellular-molecular framework, emphasizing how the unique vulnerability of the apical microenvironment arises from its histological and biology, developmental remnants of the dental lamina epithelium, and characteristic of the periapical root region. Furthermore, this review draws parallels between OI-ARS and similarly resorption patterns observed in deciduous teeth and adjacent teeth of impacted teeth, proposing shared regulatory mechanisms involving spatiotemporal control of osteoclastogenesis. Finally, this review identifies critical research directions for elucidating the mechanisms of OI-ARS, aiming to provide novel insights for the prevention and clinical management of this complication.