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Questions and Answers
What primarily modifies during physiological tooth movement?
What primarily modifies during physiological tooth movement?
What triggers orthodontic tooth movement?
What triggers orthodontic tooth movement?
Which area of the periodontal ligament is more active during tooth migration?
Which area of the periodontal ligament is more active during tooth migration?
What effect does the applied force during orthodontic treatment have on the tissues around a tooth?
What effect does the applied force during orthodontic treatment have on the tissues around a tooth?
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What is a protective function of acellular cementum during physiological migration?
What is a protective function of acellular cementum during physiological migration?
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What is the primary function of the periodontal ligament?
What is the primary function of the periodontal ligament?
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Which cell type is NOT found in the periodontal ligament?
Which cell type is NOT found in the periodontal ligament?
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What is generated in the alveolar bone in response to bending during function?
What is generated in the alveolar bone in response to bending during function?
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Which structure surrounds the tooth and connects it to the alveolar bone?
Which structure surrounds the tooth and connects it to the alveolar bone?
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What happens to the periodontal ligament when pressure is maintained against a tooth?
What happens to the periodontal ligament when pressure is maintained against a tooth?
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Which type of bone is specifically referred to as bundle bone?
Which type of bone is specifically referred to as bundle bone?
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Which of the following is NOT a fiber type found in the periodontal ligament?
Which of the following is NOT a fiber type found in the periodontal ligament?
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What role do osteoclasts play in alveolar bone management?
What role do osteoclasts play in alveolar bone management?
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What characterizes the orthodontic forces compared to natural forces?
What characterizes the orthodontic forces compared to natural forces?
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Which theory states that changes in bone metabolism are controlled by electric signals?
Which theory states that changes in bone metabolism are controlled by electric signals?
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What happens to the fibers of the periodontal ligament (PDL) during the application of force to the tooth?
What happens to the fibers of the periodontal ligament (PDL) during the application of force to the tooth?
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What does sustained pressure do to the tooth within the periodontal ligament space?
What does sustained pressure do to the tooth within the periodontal ligament space?
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What phenomenon occurs due to the deformation of crystalline structures under force?
What phenomenon occurs due to the deformation of crystalline structures under force?
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What is the primary mechanism highlighted in Pressure-Tension Theory for tooth movement?
What is the primary mechanism highlighted in Pressure-Tension Theory for tooth movement?
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What is the primary biological structure involved in tooth movement during orthodontic treatment?
What is the primary biological structure involved in tooth movement during orthodontic treatment?
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What percentage of connective tissue in the gingiva is made up of collagen fibers?
What percentage of connective tissue in the gingiva is made up of collagen fibers?
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How does bending of the alveolar bone during mastication contribute to orthodontic treatment?
How does bending of the alveolar bone during mastication contribute to orthodontic treatment?
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What maintains the width of the periodontal ligament space during orthodontic treatment?
What maintains the width of the periodontal ligament space during orthodontic treatment?
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Which type of fiber extends from the cementum to the attached gingiva?
Which type of fiber extends from the cementum to the attached gingiva?
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What is the primary composition of cellular cementum formed after tooth eruption?
What is the primary composition of cellular cementum formed after tooth eruption?
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What is the role of gingival fibers?
What is the role of gingival fibers?
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Which of the following best describes acellular cementum?
Which of the following best describes acellular cementum?
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What primarily facilitates the remodeling of surrounding bone during tooth movement?
What primarily facilitates the remodeling of surrounding bone during tooth movement?
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The structure responsible for tooth attachment to the alveolar bone is primarily made up of what?
The structure responsible for tooth attachment to the alveolar bone is primarily made up of what?
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What happens to blood flow in the compression areas of the periodontal ligament (PDL)?
What happens to blood flow in the compression areas of the periodontal ligament (PDL)?
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What is the first stage of tooth movement according to the Pressure-Tension Theory?
What is the first stage of tooth movement according to the Pressure-Tension Theory?
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Which chemical agents are involved in the second stage of tooth movement?
Which chemical agents are involved in the second stage of tooth movement?
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How does the magnitude of sustained pressure affect blood flow in the PDL?
How does the magnitude of sustained pressure affect blood flow in the PDL?
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What occurs during direct (frontal) bone resorption?
What occurs during direct (frontal) bone resorption?
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What is the immediate effect of applying light but prolonged force to a tooth?
What is the immediate effect of applying light but prolonged force to a tooth?
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Which of the following statements is true regarding the two mechanisms of tooth movement?
Which of the following statements is true regarding the two mechanisms of tooth movement?
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What is the consequence when vessels in the PDL are totally collapsed due to sustained heavy pressure?
What is the consequence when vessels in the PDL are totally collapsed due to sustained heavy pressure?
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What is the time frame for osteoclasts to appear and initiate orthodontic tooth movement under normal conditions?
What is the time frame for osteoclasts to appear and initiate orthodontic tooth movement under normal conditions?
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What occurs to blood vessels in the compression area under light pressure?
What occurs to blood vessels in the compression area under light pressure?
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What characterizes indirect (undermining) bone resorption?
What characterizes indirect (undermining) bone resorption?
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How long does it take for osteoclasts to migrate to an area under undermining resorption before tooth movement can start?
How long does it take for osteoclasts to migrate to an area under undermining resorption before tooth movement can start?
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What type of tissue forms in the periodontal ligament (PDL) during undermining resorption?
What type of tissue forms in the periodontal ligament (PDL) during undermining resorption?
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Which factor is not a reason for the delay in tooth movement during indirect bone resorption?
Which factor is not a reason for the delay in tooth movement during indirect bone resorption?
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What is the relationship between force applied and the type of bone resorption that occurs?
What is the relationship between force applied and the type of bone resorption that occurs?
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What happens to blood supply during heavy pressure applied in the compression area?
What happens to blood supply during heavy pressure applied in the compression area?
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Study Notes
Orthodontic Tooth Movement: Histology and Biomechanics
- Orthodontic treatment applies prolonged pressure to teeth. This leads to tooth movement as the surrounding bone remodels.
- Tooth movement is primarily a periodontal ligament phenomenon.
- The periodontal ligament is a soft, vascular, and cellular connective tissue that surrounds tooth roots and links the root cementum with the lamina dura.
- It has specific nutritional requirements: vessels extending from the alveolar bone to the periodontal ligament space, and vascularization in the apical and gingival regions.
- Cellular elements include undifferentiated mesenchymal cells, fibroblasts, and osteoblasts.
- Ground substance includes proteoglycan, glucoseaminoglycans, and other proteins.
- The main periodontal ligament fibers include alveolar crest, oblique, horizontal, apical, and interradicular fibers.
Periodontium (Tooth Supporting Structures)
- The periodontium includes the gingiva, cementum, periodontal ligament, and alveolar bone.
- Gingiva is connective tissue consisting of collagen fibers (60%), fibroblasts (5%), and extracellular matrix, nerves, and vessels (35%).
- Gingival fibers (circumferential, dentogingival, dentoperiosteal, and transeptal) maintain the form and integrity of the attachment between the teeth and the gingiva.
- Cementum is the non-vascularized, non-innervated layer covering tooth roots.
- During tooth formation, primary cementum is acellular. Following eruption, secondary cementum is cellular, responding to tooth needs.
- The alveolar bone surrounds the tooth, one millimeter apical to the cementoenamel junction.
- The portion of the alveolar bone incorporating principal PDL fibers is called bundle bone
- Osteoclasts and osteoblasts are responsible for alveolar bone remodeling.
Physiological Tooth Movement
- Tooth eruption and mesial/distal migration are examples of physiological tooth movement.
- Occlusal force alterations (e.g., loss of neighboring/antagonist teeth) can change tooth movement patterns.
- During tooth migration, the periodontal ligament (PDL) and alveolar bone undergo remodeling.
- The turnover rate of the PDL isn't uniform along the ligament. Cells on the bony side are more actively involved in remodeling than those on the root side.
- Acellular cementum protects the root surface from resorption during physiological migration.
PDL Response to Normal Function
- During mastication, teeth and periodontal structures are subjected to brief, intermittent, heavy forces.
- The incompressible tissue fluid in the PDL transmits force to the alveolar bone, causing it to bend.
- Bone bending generates piezoelectric currents, stimulating skeletal regeneration and repair.
- If pressure is maintained, fluid is expressed, the tooth displaces, compressing the PDL against adjacent bone, and pain can be felt.
Physiologic Response to Heavy Pressure Against a Tooth
- Pressure less than one second causes alveolar bone bending and piezoelectric signals.
- Pressure for one to two seconds causes fluid expression and PDL displacement.
- Pressure lasting three to five seconds leads to fluid expulsion and tissue compression.
PDL Response to Light Orthodontic Forces
- Physiologically, light forces cause direct frontal bone resorption, typically in the first hours or days
- Osteoclasts appear in the area of the alveolar bone facing the PDL, causing frontal resorption
- Light continual forces are needed for these and blood vessels are not obstructed
Response to Sustained Heavy Pressure
- The force produces a delay of several days with hyalinization and undermining resorption
- The delay is due to both the delay in stimulating the differentiation of cells within the marrow spaces and the considerable thickness of bone that requires removal prior to any tooth movement.
- Undermining pressure results in blood vessel occlusion and decreased blood supply, leading to undermining resorption
- Areas requiring resorption are separated in small spaces with vessels cut off and areas filled in with hyaline tissue
Biological Control of Tooth Movement
- Biological control mechanisms are involved in orthodontic tooth movement from the time of sustained force application.
Theories of Orthodontic Tooth Movement
- Two main theories describe mechanisms for orthodontic tooth movement- Piezoelectricity and Pressure Tension.
Piezoelectricity Theory
- Tooth movement is affected by the distortion of crystal structures (hydroxyapatite and collagen) that produce electric currents as a response. Displacing electrons from one section of the crystal lattice to another results in an electric current flow that affects the alveolar bone in a pressure environment
- The bending of alveolar bone in mastication generates piezoelectric signals responsible for bone remodeling and PDL space maintenance
Pressure-Tension Theory
- Chemical messengers (cAMP, cGMP, and interleukins) regulate cellular changes, thus controlling orthodontic tooth movement, rather than the electric signals generated by piezoelectricity.
- Application of pressure in the PDL space compresses the ligaments in one area while stretching them elsewhere.
- Compressing blood vessels leads to decreased blood flow in that area and increases blood flow in stretched areas of the PDL space.
- Tooth movement involves three stages: altering blood flow, producing/releasing chemical agents, and cellular activation.
Effects of Force Magnitude
- Light forces, while prolongued, lead to light frontal resorption of bone.
- Heavier sustained force leads to a greater reduction in blood flow within the compressed areas of the periodontal ligament (PDL).
Factors Enhancing Hyalinized Tissue Formation
- Heavy forces
- Forces concentrating in narrow areas (e.g., intrusion)
- Sudden or continuous forces
- Anatomy of the alveolar bone (increased cortical bone)
- Root anatomy
- The aim of orthodontic treatment is to promote tooth movement via frontal resorption while preventing unnecessary PDL necrosis and undermining.
Contemporary Perspective
- Contemporary perspective suggests that both piezoelectricity and pressure-tension mechanisms are involved in regulating biological tooth movement.
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Description
Test your knowledge on the physiological aspects of orthodontic tooth movement. This quiz covers the modifications in the periodontal ligament, the role of forces during treatment, and the cellular responses involved in tooth migration. It is ideal for students and professionals in orthodontics and dentistry.
