Theories to end

• There are four theories on the mechanism of tooth movement: Bone Remodeling Theory, Root Growth Theory, Vascular Pressure Theory, and Periodontal Ligament Traction Theory.
• Tooth movement/ eruption is a multi-faceted phenomenon, including contraction of the PDL cells, root development, bone formation, and changes in the vascular pressure.
• Bone Remodeling Theory suggests that the growth of the alveolar bone by selective bone formation and resorption will pull the tooth into the oral cavity.
• The alveolar bone where the teeth are housed is responsible for the tooth movement that makes teeth erupt according to Bone Remodeling Theory.
• Dental follicles initiate eruption according to Bone Remodeling Theory.
• The inherent growth pattern in the maxilla and mandible which moves teeth by Selective deposition and resorption of the bone is a part of Bone Remodeling Theory.
• The changes in the alveolar bone propels the teeth into eruption according to Bone Remodeling Theory.
• This theory states that the tooth is pushed coronally (upward into occlusion) by the growth of bone around the tooth.
• Changes in the alveolar bone (remodeling of the bone, selective deposition and resorption) lead to tooth movement that leads to teeth eruption according to Bone Remodeling Theory.
• During tooth eruption, changes occur in the periodontal ligament (PDL) as the fibers become more prominent and detach and re-attach themselves to stabilize their connection with the teeth.
• The contraction of the PDL facilitates the eruption of teeth.
• Fibroblast and myofibroblast bring about the eruption of teeth.
• Force moving tooth is likely generated by the contractile property of PDL fibroblasts but eruption process needs other conditions such as root growth and bone collagen remodeling.
• Tooth movement/ eruption is a multi-faceted phenomenon which means you need the contraction of the PDL cells, root development, bone formation, and changes in the vascular pressure to bring about the eruption.
• Odontoclasts are very important cells involved in the shedding and resorption process of primary teeth.
• Odontoclasts are multi-nucleated cells that are responsible for root resorption during shedding of primary teeth and resorption of remaining root.
• Odontoclasts originate from blood monocytes and undifferentiated Mesenchymal cells.
• Odontoclasts have ruffled border and a sealing zone.
• Anti-Bone Remodeling Theory claims that bone remodeling theory is not accepted as bone deposition & resorption are both seen as a result or effect of eruptive forces applied by the tooth over bone.
• Experimental studies using Bone Markers (Tetracycline) show that bone apposition at the bottom of a bony crypt housing an erupting tooth is the result of the occlusal movement of the tooth and not a cause for eruption.
• Odontoclasts and osteoclasts are structurally similar, being multi-nucleated.
• Odontoclasts differ from osteoclasts by having a ruffled border and containing vacuoles filled with acid phosphates that initiate resorption of primary teeth.
• Odontoclasts have a clear attachment zone adjacent to the ruffle border, providing a mechanism of attachment to the teeth.
• The life cycle of odontoclasts begins with activation, where they resorb the root and cease function.
• When root resorption is almost complete, the odontoclast cells degenerate, and mononuclear cells emerge from the pulp vessels and migrate to the predentin surface.
• Less is known about the soft tissues as the primary tooth sheds.
• Just before exfoliation, resorption ceases as the odontoclasts (in their apoptotic state) migrate away from the dentin surface.
• The tooth sheds with some pulpal tissues intact.
• Odontoclasts are located within the houghship’s lacuna which approximates the root, allowing them to resorb the tooth significantly.
• A ligament at the apex of the tooth provides a strong base for the apical growth of root to grow against and propel the tooth occlusally.
• Tetracycline is an antibiotic used as a bone marker in the experimental studies of those who are anti-bone remodeling theory.
• Unlike the osteoclasts, odontoclasts are mononucleated.
• Odontoclasts are multi-nucleated cells that are responsible for root shedding.
• Odontoclasts do not have the ability to resorb pre-dentin.
• The theory states that teeth are pushed coronally due to the changes in the alveolar bone.
• Type of deposition and resorption that happens in the bone according to the theory in no.7.
• The cells in the PDL that causes tooth eruption according to the PDL Traction theory are the cells responsible for the tractional force, since without the cells no force is generated for eruption.
• Tooth movement/eruption is ONLY due to the contractile property of PDL fibroblasts.
• Anti-Vascular Pressure Theory is debatable because root and vascular excision does not prevent tooth eruption.
• Root resection in Rats by Berkovitz & Thomas (1969) involved the removal of the growth center of incisor (apical part of root) in rats, resulting in the absence of tissue fluid.