biologic basis tooth movement-ortho / orthodontic courses by indian dental academy
TRANSCRIPT
www.indiandentalacademy.com
INDIAN DENTAL ACADEMYLeader in continuing dental education
www.indiandentalacademy.com
Biologic basis of Orthodontic Treatment
Biologic basis of Orthodontic Treatment State of equilibrium Classification of Orthodontic Forces Theories of Tooth Movement Types of Orthodontic tooth movement Orthopedic effects of Forces Iatrogenic effects of Orthodontic forces
www.indiandentalacademy.com
Why do teeth not move under normal circumstances?
--- Equilibrium theory, which states that the forces from the extraoral and the intraoral areas balance each other, aided additionally by the periodontium.
www.indiandentalacademy.com
www.indiandentalacademy.com
THE BASIS OF ORTHODONTIC TOOTH MOVEMENT
ORTHODONTIC TREATMENT IS BASED ON THE PRINCIPLETHAT IF PROLONGED PRESSURE IS APPLIED TO A TOOTH,
TOOTH MOVEMENT WILL OCCUR AS THE BONE REMODELS.
BONE IS SELECTIVELY REMOVED IN SOME AREAS AND ADDED IN OTHERS.
www.indiandentalacademy.com
THE TOOTH MOVES THROUGH THE BONE CARRYING ITS ATTACHMENT APPARATUS WITH IT,AS THE SOCKET OF THE TOOTH MIGRATES.
THIS BONY RESPONSE IS MEDIATED BY THE
PERIODONTAL LIGAMENT, TOOTH MOVEMENT IS
PRIMARILY A PERIODONTAL PHENOMENON.
www.indiandentalacademy.com
Forces applied to the teeth can also affect the pattern of bone apposition and resorption at sites distant from the teeth, viz sutures of the maxilla and bony surfaces of the TMJ
Thus, the biologic response to orthodontic treatment includes not only the response of the PDL, but also the growing areas distant from the dentition.
www.indiandentalacademy.com
Theories of tooth movement
Pressure-tension theory Piezo-electric theory
www.indiandentalacademy.com
Theories of tooth movement
Pressure-tension theory: This is the most accepted theory. According to this theory, whenever pressure and tension zones exist, chemical messengers are released which will bring about recruitment of osteoblasts and osteoclasts
www.indiandentalacademy.com
Theories of tooth movement
Pressure-tension theory: Can be divided into three overlapping stages which include –
a) Alterations in Blood flow associated with pressure
b) Formation and /or release of chemical mediatorsc) Activation of cells
www.indiandentalacademy.com
Theories of tooth movement
Alterations in Blood flow associated with pressurea) Increasing pressure on the tooth results in
reduction of blood flow.If the force application continues, a zone of sterile
necrosis results – Zone of Hyalinization
www.indiandentalacademy.com
www.indiandentalacademy.com
Theories of tooth movement
The second stage involves the release of chemical messengers
--- Primary messengers: Cytokines, Prostaglandins
---- Secondary messengers: Cyclic AMP
Prostaglandin E2 has the property of stimulating both osteoblastic as well as osteoclastic activity
www.indiandentalacademy.com
After a delay of several days, cellular elementsfrom adjacent undamaged areas of PDL begin toinvade the necrosed area.Osteoclasts appear within adjacent bone marrow
Spaces & begin an attack on the underside of theBone immediately adjacent to PDL—underminingResorption, since the attack is from the underside
Of lamina dura.
www.indiandentalacademy.com
These osteoclasts arrive in two waves
-First wave-derived from local cell population-Larger second wave-are brought in from distantAreas via blood flow. These cells attack the adjacent lamina dura removing bone in the process ofFrontal resorption.Tooth movement begins thereafter.At the sametime,osteoblasts recruited from PDL form bone on the tension side & begin remodeling activity.
www.indiandentalacademy.com
www.indiandentalacademy.com
Pressure-tension theory Two types of resorption patterns are seen
whenever forces are applied to move teeth.a) Frontal Resorptionb) Undermining resorption
www.indiandentalacademy.com
Pressure-tension theorya) Frontal Resorption: This is a favourable resorption
pattern which depends on: -- Magnitude of force -- Duration of forceIn this type of resorption, Howship lacunae are seen
adjacent to the PDL in the frontal aspect of the lamina dura.
www.indiandentalacademy.com
Pressure-tension theoryb) Undermining resorption : This is a resorption
pattern seen whenever heavy forces are applied, which compress the PDL beyond half its original size.
Due to obstruction of the blood flow, osteoclasts cannot be recruited onto the frontal aspect of the lamina dura.
www.indiandentalacademy.com
Pressure-tension theoryb) Undermining resorption : Instead, a resorption wave is initiated from the
underside of the Lamina dura – known as ‘Undermining resorption’
Responsible for ‘jumpy’ pattern of tooth movement, often seen with fixed appliances
www.indiandentalacademy.com
www.indiandentalacademy.com
The Piezo-electric theory According to this theory, whenever stresses are
applied to bone, it deforms and bends. Charges are produced on the inside and outside,
which stimulate either deposition or resorption
www.indiandentalacademy.com
www.indiandentalacademy.com
The Piezo-electric theory Limitations: a) Does not explain how the chemical mediators actb) Piezo-electricity exists only for a short period.
www.indiandentalacademy.com
Classification of Orthodontic forces According to Schwarz :a) First degree of efficiency:These are forces lower
than the threshold of stimulation to activate Orthodontic tooth movement.
---Short duration and low force balanced by the compensatory mechanisms
www.indiandentalacademy.com
Classification of Orthodontic forces According to Schwarz :c) Third degree of Efficiency: The forces in
this category tend to interrupt circulation in the PDL (20-50 gm/sq.cm)
www.indiandentalacademy.com
Classification of Orthodontic forces According to Schwarz :b) Second degree of efficiency:This refers to force
levels most effective in achieving Orthodontic tooth movement. (Optimum Orhtodontic force). Characterised by low but continuous forces (roughly 15-20 gm/sq.cm over the compressed PDL)
www.indiandentalacademy.com
Classification of Orthodontic forces According to Schwarz :d) Fourth degree of Efficiency: The force levels in
this group are so excessive that they crush the PDL between the tooth and the alveolar bone in the areas of pressure. If continuous, they can cause extensive, irreparable damage.
www.indiandentalacademy.com
Classification of Orthodontic forces According to Proffitt :a) Continuous Forcesb) Interrupted forcesc) Intermittent forces
www.indiandentalacademy.com
Factors affecting tooth movement
a) Age of the patient and in turn, the viability of supporting structures
b) Magnitude, duration and type of forces appliedc) Chemical agents – action of certain drugs
www.indiandentalacademy.com
THE ORTHODONTIC FORCE DURATION IS CLASSIFIED-
1) CONTINUOUS –
2 ) INTERRUPTED-
3 ) INTERMITTENT-
Continuous and interrupted forces are produced by Fixed appliances, while the intermittent forces are produced by removable appliances
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
Factors affecting tooth movement
a) Age of the patient and in turn, the viability of supporting structures
b) Magnitude, duration and type of forces appliedc) Chemical agents
www.indiandentalacademy.com
Types of Orthodontic tooth movement
a) Tippingb) Translation (Sagittal)c) Intrusiond) Extrusione) Rotation
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
EFFECTS OF FORCE MAGNITUDE
THE HEAVIER THE SUSTAINED PRESSURE,GREATER SHOULD BE THE REDUCTION IN BLOOD FLOW THROUGH COMPRESSED AREAS OF PDL,VESSELS ARE TOTALLYCOLLAPSED NO FURTHER BLOOD FLOWS.
WHEN LIGHT BUT PROLONGED FORCE IS APPLIED-•Blood flow decreases•Partially compressed PDL•Tooth moves in the socket
www.indiandentalacademy.com
Harmful effects of Orthodontic ForcesHeavy forces often result in extensive damage to the PDL
as well as root surfaces.
a) Crushing of the PDL – causing pain as well as mobilityb) Reversible resorption of bone c) Apical Root Resorption
www.indiandentalacademy.com
Orthopedic forces and their effectsa) On the maxilla – Maxillary growth stimulation or restraint is facilitated because of the presence of suturesin the naso-maxillary complex.
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.com
www.indiandentalacademy.comLeader in continuing dental education