Bio mechanical principle in orthodontic treatment
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Bio-mechanical Principle in Orthodontic Treatment. Xi'an Jiaotong University Stomatology hospital Orthodontic Department Zou Min. Appliance. Force. Displacement. tooth 、 Alveolar 、 bone. Ⅰ Biological characteristics of Periodontal tissue.

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Bio-mechanical Principle in Orthodontic Treatment

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Bio mechanical principle in orthodontic treatment

Bio-mechanical Principle in Orthodontic Treatment

Xi'an Jiaotong University Stomatology hospital

Orthodontic Department Zou Min


Bio mechanical principle in orthodontic treatment

Appliance

Force

Displacement

tooth、Alveolar 、bone


Biological characteristics of periodontal tissue

Ⅰ Biological characteristics of Periodontal tissue


Biological characteristics of periodontal tissue1

Ⅰ Biological characteristics of Periodontal tissue

(一)Stability of Periodontal ligament Environment

Periodontal ligament(PDL)

is made up of Fibrous connective

tissue,mostly connect teeth to alveolar,so that teeth fixed in the alveolar.


Biological characteristics of periodontal tissue2

Ⅰ Biological characteristics of Periodontal tissue

(一)Stability of Periodontal ligament Environment

Cell

Periodontal ligament hasthree cells (Three components):

1 compound cell

2 Absorption cell

3 Undifferentiated cells


Biological characteristics of periodontal tissue3

Ⅰ Biological characteristics of Periodontal tissue

(一)Stability of Periodontal ligament Environment

Tissue fluid : Periodontal ligamentis full oftissue fluid, which isto absorb external force.As the liquid is incompressible, the force gave to teeth is quickly spread to the alveolar .


Biological characteristics of periodontal tissue4

Ⅰ Biological characteristics of Periodontal tissue

(二)Plasticity of alveolar

Bone especially alveolar has the general robustness of bone tissue and highly Plasticity.In the physiological state, constantly updated and translated,through the conversion and absorption to achieve a new balance .


Biological characteristics of periodontal tissue5

Ⅰ Biological characteristics of Periodontal tissue

(三) Resistance to stress of the cementum

Root surface is covered with a thin layer of cementum ,it fights against external forces ,protect cementum not to be absorbed.


Biological theory of teeth movement

Ⅱ Biological theory of teeth movement

1. Piezoelectric theory

Piezoelectric effect is the phenomenon by crystal material deformation produced by charge . Negatively charged concave, convex positively charged


Bio mechanical principle in orthodontic treatment

Ⅱ Biological theory of teeth movement

  • Piezoelectric theory

  • Piezoelectric effect has two characteristics:

  • 1 The loss of speed is very quickly. If the force continues, it dose not continue to produce electrical signals.

  • 2 The disappearing of force brings the same amount but the opposite direction of the signal .


Bio mechanical principle in orthodontic treatment

ⅡBiological theory of teeth movement

1. Piezoelectric theory

Have a positive effect on the normal alveolar bone metabolism.The effect about the continuing orthodontic force is not clear.

Results show: Electrical changes in the environment can affect the permeability of cell membrane, causing cell activation.


Bio mechanical principle in orthodontic treatment

Ⅱ Biological theory of teeth movement

  • 2. Mechanical - chemical theory of bone:

  • external force teeth blood change of PDL Chemical environment of PDL(the level of oxygen and other relative levels of metabolites ,for example  Concentration of Central - phosphate )  Cell differentiationBone formation and absorption


Bio mechanical principle in orthodontic treatment

Ⅱ Biological theory of teeth

movement

  • 2. Mechanical - chemical theory of bone:

  • Tension side:

  • The amount of blood increase blood oxygen content of the blood increase

  • Osteoblast differentiation

  • bone formation


Bio mechanical principle in orthodontic treatment

  • Pressure side:

  • Decreased blood flow Decreased blood oxygen content

  • Osteoclast differentiation

  • Bone resorption


Organizational change in the process of orthodontic treatment

Ⅲ Organizational change in the process of orthodontic treatment

(一) The response ofalveolar and periodontal ligament to orthodontic force

1. Pressure side

Periodontal ligament narrowed

Reduce blood flow

Degradation and absorbtion

of collagen fibers

Alveolar bending deformation

Osteoclast differentiation

Alveolar resorption


Bio mechanical principle in orthodontic treatment

Movement of teeth

Multinuclear osteoclasts


Organizational change in the process of orthodontic treatment1

Ⅲ Organizational change in the process of orthodontic treatment

(一) Response to orthodontic force byalveolar and periodontal ligament

Large treatment force——Local vascular hemorrhage,Periodontal tissue degeneration transparent,Transgender organizationswas absorbed by Phagocyte ,Newborn fibroblasts 、

Vascular invasive ,repair them

——

Indirect absorption happens on the

pressure of the alveolar ,

indirect absorption also known as

“Absorption of prowling ”.

root tip is the mostly area of the root of

teeth.


Bio mechanical principle in orthodontic treatment

Ⅲ Organizational change in the process of orthodontic treatment

Tension side:

Periodontal fiber elongation stretch Blood flow increased Fibroblast proliferation , Alveolar bone bending deformation Osteoblast differentiation

The surface of bone trabeculae to form new Trabecular bone Osteogenic


Bio mechanical principle in orthodontic treatment

(1)the response of alveolar and periodontal ligament to orthodontic force

In the process of tooth movement,Cells generally appear within 36 hours after the burner.


Organizational change in the process of orthodontic treatment2

Ⅲ Organizational change in the process of orthodontic treatment

(2)Other

1. Dental tissue

  • Changes in cementum

  • Changes in root

  • Changes in pulp tissue

  • 2. Impaction of deciduous tooth movement to constant tooth germ

    3. Changes in suture

    4. Impact on the adjacent teeth


Bio mechanical principle in orthodontic treatment

Ⅲ Organizational change in the process of orthodontic treatment

(3)Periodontal tissue alterations and recovery after teeth movement

Periodontal tissue alterations usually takes four weeks to complete, which is one-month clinical follow-up visits the patient basis on the biological for the physiological movement of teeth.


Bio mechanical principle in orthodontic treatment

Ⅲ Organizational change in the process of orthodontic treatment(三)Periodontal tissue alterations and recoveries after teeth movement

Periodontal ligament fibers to keep nine months is still anomaly.

New bone to maintain 9 months is not mature .

normal combination of periodontal ligament and alveolar need 3 months.

Root absorption and recovery are more than 3 months.

Therefore, after treatment it needs to keep more than 1 year .


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of strength of

orthodontic force

Strength of different organizations have different power levels of impaction. If the force is too small, itcan not cause periodontal tissue changes in the chemical environment, the teeth will not move. Excessive force can cause some periodontal tissue degeneration and necrosis, degeneration and necrosis of these organizations need to remove and repair a longer period of time, tooth movement will be slowed down, even not to move.


The effect of strength of orthodontic force the size of forces

Ⅳ The effect of Strength of orthodontic force(一)The size of forces

Ⅰ level :too small to cause teeth moving

Ⅱ level :moderate and long-lasting ,and can cause organizations response in 5~6 hours generally

Ⅲ level :so large that local periodontal fiber denaturize and necrosis

Ⅳ level:Periodontal ligament compression,and cementum and alveolar adhesion


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force

(二) the best strength of treatmentIn theory , it should be moderate and long-lasting, and the strength can not exceed the pressure ofperiodontal ligament capillary, so that the capillaries is in a semi-closed state, generally around 75-100g.


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force

1.Indications of determine the appropriate corrective force in clinic

No significant pain consciously

No significant response to percussion

Forced teeth has no obvious loosening ?( < II )

Obvious teeth movement

There is no pathological changes of roots and periodontal tissue on X-ray


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force

2.Appropriate orthodongtic force observed by Histological

The pressure side vessel is compressed, but not closed

The cells have the greatest response

Organization is in a activity, but not nonecrosis

Direct absorption of alveolar more than the indirect absorption


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force

(三)The type of tooth movement and the distribution of power

1Conception

Center of Resistance

It is the simplify center of the resistance movement of objects ,also known as resistance, the center of objects. It is inherent, and not impacted by outside force.


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force

(三)The type of tooth movement and the distribution of power

1Conception

Center of Rotation

Refers to objects in the external force by the next rotation around the point center of rotation with the external force and torque changes.


The effect of strength of orthodontic force

Ⅳ The effect of Strength of orthodontic force

(三) The type of tooth movement and the distribution of power

1Conception

Force: size, direction, point


Bio mechanical principle in orthodontic treatment

moment=force×arm(Resistance force from the center line of the vertical distance) 。Moment has two variables:Force and distance. The direction of moment consistent with the direction and force ofresistance centers +is Anti-clockwise rotation,-is clockwise rotation.


Bio mechanical principle in orthodontic treatment

couple:Two forces with equal size but opposite direction operated on the same odjects. They are parallelled but not in a line. Couple of teeth can cause a simple rotation.

Couple moment:one of the force×arm


Bio mechanical principle in orthodontic treatment

  • Orthopedic Force:Large and discontinuous, causing the power to change the bone morphogenetic.

  • Orthodontic force:Smaller sustained, causing the power to change the tooth and dental arch .


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force

2. The type of tooth movement

(2)Incline movement:

Crown and root movement are in opposite direction with a fulcrum which is in the border between the 1/3 of root and 1/3 of middle of root by a single horizontal force.The periodontal tissues of root apiex and alveolar was afforded the largest power which is about 50g .


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force

2. The type of tooth movement

(2)Bodily movement:

Crown and root movement are in one direction at the same time. On the one side of the periodontal tissues is compressed, the other side is tracted.The power distribution can support greater forces which is generally believed that 100 - 150g or so.


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force

2 The type of tooth movement

(3)Vertical movement:

Teeth instrusion:In this movement , there is only a small amount  periodontal ligament of apical squeezed. If the force is too large, the obstacles to the blood circulation will be easier to caused in the root zone, resulting in group symptoms of necrosis and pulp texture. Therefore the power to suppress should be very modest. generally power: 15 - 25g


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force

2. The type of tooth movement

(3)Vertical movement:

Teeth extrusion:In the movement, the periodontal fibers was force to extrusion,and new alveolar bone was formated in Alveolar fossa which make the alveolar increased with the teeth extrusion. As Periodontal ligament supporting a large of forces , extrusion movement can endure a larger elongation force. Force value of 50 - 100g


Bio mechanical principle in orthodontic treatment

rotation


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force

2. The type of tooth movement

(4)Rotation movement :

A couple of forces can made the crown and root rotate along the tooth axis. Most of periodontal fiber was forced by the horizontal direction level of traction, and flat tooth root formation will make two pressure zone and one tension zone. The role of the force is between extrusion and intrusion


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force

2. The type of tooth movement

(5)Torque

Torque movement is also known as root-controlled movement, which can cause the root to move without the moving of the crown .Alveolar resorption occurred in the 1 / 3 of the roots first, and apical has the largest movement. Periodontal ligament has larger force area which is similar to the bodily movement.


Bio mechanical principle in orthodontic treatment

Ⅴ Factors that affect the tooth movement

1. Force faction

strength of force

bodily:150

tipping:50

extrusion:25

instrusion:100

rotation:100

torque:150

large:>350g

medium:60~350g

weak:<60g


Type of force mechanical force biological force and orthodontic force orthopedic force and so on

Type of forceMechanical force, biological force, and orthodontic force, orthopedic force ,and so on


Bio mechanical principle in orthodontic treatment

Forcing time

(Continuous force, intermittent force)


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force

  • 2. Body condition

    • Age   Health status   Partial anatomical factors: Root length, alveolar height


Bio mechanical principle in orthodontic treatment

Ⅳ The effect of Strength of orthodontic force 3. External factors

  • Hormones: parathyroid hormone, etc. Drug: prostaglandins, such as Salvia Physical stimulation: electrical

  • stimulation, magnetic, etc.


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