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Terms in Orthodontics

Dr.Omar S.M.J.Ali

PhD Orthodontic

• Terms in Orthodontics

Over jet :

Overbite

Open bite:

Deep bite:

Cross bite

Scissor bite

Prognathism:

Retrognathism:

Midline shifting

Diastema

Inclination

Torque: a torsion force applied to a tooth to produce or maintain crown or root movement

Tooth Movement

Introduction
Orthodontic tooth movements are based on the ability of bone to react to mechanical stresses with the apposition and resorption of alveolar bone.

What is needed !!!

1- Tooth
2- Health PDL


3- Bone
4- Applied Force

A- Fibers transmitted force applied to the tooth.

B- Damping.
C- Cells within PDL.

Mechanical Principles in Orthodontic

1-Center of Resistance: A-point at which resistance to the movement can be concentrated for mathematical analysis.

Location of Cres:

Cres


The Roots Attachment
Root length
Root morphology
Number of Roots
alveolar bone height

Center of Rotation:

The point around which rotation actually occurs when an object is being to move.

• Extrusion:

• A translational type of tooth movement parallel to the long axis of the tooth in the direction of the occlusal plane.

Occlusal plane

Types Of Tooth Movement


• Intrusion:
• A translational type of tooth movement parallel to the long axis of the tooth in the direction of the apical level.

Apical Level

• Pure Root Movement:

• The type of tooth movement for which the center of rotation is at the incisal edge.

Incisal edge

Center of Rotation

• Controlled Tipping:

• A type of tooth movement consisting of rotation about the apex of the tooth.

Apex

Center of Rotation

• Uncontrolled Tipping:

• Movement of the crown and the apex of the tooth in opposite direction.

Apex

Occlusal Plane
Center of Rotation

• Translation (Bodily movement):

• All points on a tooth move in the same direction by the same amount.

Apex

Occlusal Plane

• 7. Rotation Movement:

• Movement of the tooth around its long axis by two forces equal in magnitude and opposite in direction.
LONG AXIS

Force 1

Force 2

Occlusal View

Uncontrolled Tipping

Controlled Tipping
Intrusion
Extrusion
Pure root Movement
Bodily


CRot=
Cres=

When to Use—What Appliance !!

Fixed

Tipping

Rotation

Extrusion

Intrusion
Bodily

When to Use—What Appliance !!

Removable

Tipping

Rotation

Extrusion

Intrusion
Bodily

Optimal orthodontic force:

The lightest force that will move the tooth to a desirable position in shortest possible time with no iatrogenic effect.
• Force (gm)
• Type of Movement
• 35-60
• Tipping
• 70-120
• Bodily Movement (Translation)
• 50-100
• Root uprighting
• 35-60
• Rotation
• 35-60
• Extrusion
• 10-20
• Intrusion

Force Measurement

Classification of Force by the Rate of Decay

• Continuous---Force maintained at the same appreciable fraction of the original from one patient visit to the next.
• Interrupted---Force levels decline to zero between activations.
• Both 1 & 2 forces can be produced by fixed appliances that are constantly present.
• 3.Intermittent---Force level decline to zero intermittent,(e.g. when the removable appliance is taken out, only to resume when the appliance is reinserted into mouth. These forces also decay as tooth movement occurs.

The Criteria of Ideal Delivery Force

1. Provide optimal tooth-moving forces that elicit the desired effects.
2. Be comfortable and hygienic for the patient.
3. Require minimal operator manipulation and chair- time.
4. Require minimal patient co-operation.
5. Be economical.

Factors Affecting Rate of Tooth Movement

1-The Force Applied
2- Age
3- Individual Variations
4-Tooth


a- The surface area of the roots.
b- The types of tooth movement
c- Other factors such as intercuspation of the teeth

Orthodontics Adverse Affects

1- Pulp

2-Root

3- PDL
4-Bone

*Transient Inflammatory Response.

*Loss of Vitality.





Orthodontics Adverse Affects

1- Pulp

2-Root

3- PDL

4-Bone

Root Resorption.

At Risk: a-Distorted apices
b-Thin Roots
(1-2) mm Root Length

3-D dental models are used to stimulate 3-D movement of teeth including rotations, and tipping during orthodontic treatment. The proposing techniques are a part of the development diagnosis system designed to replace manual measurement method. The initial result showed that maximum stresses are produced on the outside layers. It had also shown that during tipping movement, the greater stresses occurred at alveolar crest and not at apex. Rotational forces in general produced the least stresses at all point on root surface.





Dentin
Cementum
Computer and Tooth Movement