The Karrar Paradigm of Physiological Tooth Movement and Lamina Dura Adaptation: A Conceptual Mechanobiological Framework

This paper proposes the Karrar Equilibrium Model, a conceptual mechanobiological framework for explaining physiological tooth movement and lamina dura adaptation through dynamic force balance within the dental arch. The model suggests that tooth stability is maintained by a state of mechanical equilibrium generated through the interaction of periodontal ligament (PDL) tension, surrounding alveolar bone response, and opposing arch forces. Within this framework, the lamina dura is interpreted as a load-adaptive structure influenced by continuous functional mechanical stimulation rather than a purely static anatomical entity. Disruption of this equilibrium, such as following tooth extraction or loss of occlusal opposition, may result in the emergence of a net directional force that activates biologically regulated bone remodeling through mechanotransduction pathways. This process may contribute to clinically observed phenomena including mesial drift, distal drift, and over-eruption. The proposed model integrates established biomechanical and biological principles into a unified theoretical framework that may assist in understanding tooth stability, orthodontic movement, and post-extraction structural changes.