Orthodontics: Bone Resorption and Tooth Movement

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What does the term 'frontal' indicate in the context of bone resorption?

Bone resorption occurring in front of the root. (correct)

Bone resorption occurring to the side of the root.

Bone resorption occurring behind the root.

Bone resorption occurring in the apex of the root.

What happens to the periodontal ligament when subjected to heavy forces exceeding capillary pressure?

It experiences a period of rapid bone growth.

It results in sterile necrosis of the affected area. (correct)

It leads to increased blood flow to the area.

It causes the ligament to become inflamed but remains functional.

What is the initial effect of necrosis on orthodontic tooth movement?

Immediate movement

Immediate bone resorption

Delayed movement (correct)

Accelerated movement

In dental contexts, what is the primary implication of 'frontal' in relation to tooth structures?

It specifies that bone loss occurs in front of the root. Signup and view all the answers

Where does bone resorption begin following necrosis during orthodontic tooth movement?

Beneath the area of necrosis Signup and view all the answers

Capillary pressure is exceeded by heavy forces which can then cause:

Sterile necrosis in the periodontal ligament. Signup and view all the answers

What is the state of the periodontal ligament in the area if the force exceeds capillary pressure?

It has undergone sterile necrosis. Signup and view all the answers

Approximately how soon after necrosis does bone resorption typically start?

Within a few days Signup and view all the answers

Which of the following best describes the timeline of events related to necrosis and tooth movement?

Necrosis, then resorption, then movement delay Signup and view all the answers

The delay in orthodontic tooth movement caused by necrosis is primarily due to what process?

Localized bone resorption Signup and view all the answers

What is the defining characteristic of undermining (indirect) resorption?

The cellular response occurs in the tiny spaces beneath the necrotic area. Signup and view all the answers

In the context of undermining resorption, where do the cells initiate their action?

From the narrow spaces beneath the necrotic area. Signup and view all the answers

Why is the term 'undermining' used to describe this type of resorption?

Because the cellular action starts from an area beneath the affected site. Signup and view all the answers

What is another term used to describe undermining resorption?

Indirect resorption Signup and view all the answers

What is the primary function of cementoclasts in the context of necrotic tissue resorption?

To facilitate the removal of root surface cementum adjacent to necrotic areas. Signup and view all the answers

What makes the cellular action in undermining resorption unique?

It is a reaction that starts in confined spaces. Signup and view all the answers

Besides necrotic tissue, what other dental material can cementoclasts resorb?

Cementum. Signup and view all the answers

What dental procedure is most commonly associated with root resorption due to cementoclast activity?

Orthodontic treatment. Signup and view all the answers

What mechanism links cementoclast activity to root resorption?

The action of cementoclasts on the cementum covering the root leading to resorption. Signup and view all the answers

The resorption of root surface cementum by cementoclasts occurs adjacent to which area of tissue?

Necrotic tissue. Signup and view all the answers

The magnitude of a moment of force is calculated by multiplying the applied force by what?

The perpendicular distance between the point of application and the centre of resistance. Signup and view all the answers

In orthodontics, why is a moment of force created when applying force to a tooth?

Because the force is applied to the crown, not the centre of resistance. Signup and view all the answers

Where is the centre of resistance of a tooth generally located?

Along the root of the tooth. Signup and view all the answers

If you apply the same amount of force but double the perpendicular distance to the center of resistance, what happens to the resulting moment of force?

The moment is doubled. Signup and view all the answers

Why is understanding the moment of force important in orthodontics?

It is useful for achieving specific tooth movements. Signup and view all the answers

How is the magnitude of a couple calculated?

The magnitude of one of the forces multiplied by the distance between them. Signup and view all the answers

In orthodontic treatment with fixed appliances, how are couples usually generated?

By the interaction between an archwire and bracket slot. Signup and view all the answers

What is a primary application of couples in orthodontics?

To alter the inclination of teeth or produce bodily tooth movement Signup and view all the answers

When a couple is used to produce bodily tooth movement, what must it counteract?

The moment from an applied force. Signup and view all the answers

If a larger couple is needed, what could be changed, based on its components?

Increase the magnitude of the applied force or increase the distance between forces. Signup and view all the answers

Study Notes

Tooth Movement Biology and Biomechanics

Tooth movement is a complex biological process involving alveolar bone remodeling, periodontal ligament reorganization, and tooth movement.
Orthodontic tooth movement involves multiple cell types and chemical mediators coordinating their activity.
Applying continuous force to a tooth surface results in compression and tension areas within the periodontal ligament.

Effects of Force on Periodontal Ligament

The force applied to a tooth affects the periodontal ligament, leading to areas of compression and tension, influencing tooth movement.
The magnitude of the force significantly affects the tissue response.
Ideal orthodontic forces shouldn't exceed capillary pressure. Exceeding this pressure causes ischemia and tissue necrosis.

Optimal Force for Tooth Movement

Optimal force for tooth movement depends on the root surface area of the tooth.
Teeth with smaller roots require less force for movement compared to teeth with larger roots.

Different Types of Tooth Movement

Tipping: This involves greater crown movement than root movement, resulting in a diagonal change in tooth position. Compressive forces act at the alveolar crest and root apex.
Bodily Movement: Equal movement of crown and root in the same direction. Requires even compressive forces along one side.

Tooth Movement Rate

Ideally, orthodontic forces are applied 24 hours a day to maximize efficient tooth movement.
At least 6 hours of force delivery per day is clinically sufficient for minimal movement.
Ideal tooth movement rate under optimal conditions is approximately 1mm per month, but individual variation exists.
Adults experience slower tooth movement due to reduced cellularity and vascularity of the periodontal ligament and higher density alveolar bone.

Mechanisms Linking Force Application and Tooth Movement

Pressure-tension theory: Pressure and tension changes within the periodontal ligament alter blood flow, triggering chemical messenger release and cellular responses for movement.
Bioelectric theory: Bending of alveolar bone triggers electrical current generation, which in turn promotes desired cellular events for movement.

Biomechanics of Tooth Movement

Forces: Forces (vectors) are described by magnitude and direction. Their components influence tooth movement.
Moments: Moments of force (rotational effects) are calculated considering the force magnitude and perpendicular distance from the force application to the center of resistance.
Couples: Moments from two equal and opposite forces that tend to cause rotation, commonly used in fixed appliance treatment.
Torque: "Torque" refers to differential movement of tooth parts while restraining others - usually achieving root torque by applying force couples to the crown.

Types of Tooth Movement

Tipping: The crown moves more than the root in a given direction, typically caused by moments from applied forces.
Bodily Movement: Crown and root move together in the same direction, often accomplished by couples in fixed appliances.

Understanding Centre of Resistance

Centre of resistance: The point in a tooth where resistance to tooth movement occurs. Single rooted teeth have a center halfway down the root. Multi rooted teeth have center of resistance in root furcation area. Maxilla's center of resistance commonly located in premolar area.

Factors influencing the rate of tooth movement

Orthodontic forces: should be applied for 24 hours/day optimally for most efficient movement (at least 6 hours a day for minimal). -Capillary pressure: Excessive force creates tissue necrosis resulting in delayed or altered tooth movement.
Time for tissue repair and remodelling: At least 4-6 weeks between successive appliance reactivations is needed for repair and remodelling of damaged tissues.

Cellular Responses to Orthodontic Forces

Cellular responses within periodontal ligament are evident within hours of orthodontic force initiation.
Chemical mediators like prostaglandin E, cytokines, and nitric oxide are detected within tissue after force application.
Osteoclasts and osteoblasts actively remodel alveolar bone responding to force application.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the intricate relationships between bone resorption and orthodontic tooth movement. This quiz covers the effects of forces on the periodontal ligament and the implications of necrosis in dental contexts. Test your knowledge on the dynamics of these processes!