Optimal orthodontic force /certified fixed orthodontic courses by Indian dental academy

OPTIMAL ORTHODONTIC FORCE

INDIAN DENTAL ACADEMY

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• Optimal orthodontics is a mode of treatment where by malocclusions are corrected efficiently, producing excellent results without causing any tissue damage.

• The amalgamated technique, introduced by DeAnglis in 1976, is based upon avoidance of potentially harmful tooth movement.


Several factors have been implicated in this irreversible change

• length of time in rectangular arch wires that fully engage the Edgewise bracket slot

• “jiggling” and round tripping of teeth in the saggital, vertical and transversal planes,


• uncontrolled tipping with the resultant excessive compression of the periodontal ligament and alveolus, and

• Incisor root contact with the palatal cortical plate.


• Proponents of the SWA, who assert that they do not fully fill the bracket slot to lessen or even eliminate the adverse sequelae, must understand the following:


1. Unless the rectangular arch wire engages the bracket slot to some degree, the pre-adjusted torque inherent in the appliance is ineffective.


2. To the extent that the rectangular arch wire does engage the bracket wings, Newtons third law applies to the other dental units in the arch and

3. Wonder Wires, super elastic NITI wires and the like, are equally as efficient in producing untoward adverse tissue reactions as they are in producing rapid, desirable movements.


• Thurow concluded that an important consideration in torque action is the use of under sized wires, and that wires which fit the bracket slot closely should never be used to torque individual teeth.


• When a rectangular wire with torque action is seated in a bracket ,twist of the wire will torque the adjacent teeth in the opposite direction.

• Teeth will not be moved permanently if the arch wire is left in place long enough to become completely passive.


• But in the course of movement the teeth will have been subjected to unnecessary back and forth action.


• SWA pre adjusted bracket, which are based on 3-D tooth positions of subjects with normal occlusion and class I apical bases


• Transformation of a class II malocclusion, particularly with skeletal class II characteristics, to a class I skeletal and dental occlusion with PEA appliance, leads to unyielding incisor palatal root torque and proximation of max incisor root apices against the palatal cortical plate of bone as retraction occurs.


• To avoid these unwanted movements, wires adjusted to torque individual teeth should be sufficiently undersized to allow the adjusted wire to rotate in the slot of the adjacent tooth with no torque action on the tooth.

• This precaution is more easily observed with a .022” slot than with a .018” slot


CLASSIFICATION OF ORTHODONTIC FORCES

I] Schwarz: force magnitude and tissue response: First degree of efficiency:

• Below threshold to stimulate tooth movement and also of too short duration.

• But if duration increased – tooth movement. Example Frankel‟s application.


Second degree of efficiency:• most favorable for continuous tooth

movement without root resorption.

• Resorption of bone at same rate as apposition.

• Weaker than block pressure in capillary block vessels – 15 to 20 gm/cm2 – duration.


Third degree of efficiency:

• Interrupt the blood circulation in periodontal membrane.

• Medium strength – 20-50gm/cm2.

• Tissue not yet crushed.

• If interrupted – bone remodeling continuous

• Necrosis of periodontal membrane most common cause of root resorption.


Fourth degree of efficiency:

• Forces of this magnitude crushes primary ligament irresponsible damage to the affected tissues necrosis of alveolar bone and root resorption.


II] Profitt:

• Continuous: Force maintained at some appreciable fraction of the original from one patient visit to the next.

• Interrupted: force levels decline to zero between activation.

• Intermittent: force levels decline abruptly to zero, intermittently, when appliance is removed or when fixed appointed is temporarily deactivated. www.indiandentalacademy.com

• Brief history


• Oppenheim in 1911 had said that only light forces should be applied to teeth for optimal exploitation of the cellular remodeling of the bone.

• Much later Martin Schwarz in 1932coined the term optimal force in orthodontics and concluded from his histologic studies of tooth movement in dogs that orthodontic forces should not exceed capillary blood pressure ( 20 g/cm2 for tipping and 40-50 g/cm2 for bodily movement)


• He defined optimal continuous force as „„the force leading to a change in tissue pressure that approximated the capillary vessels‟ blood pressure, thus preventing their occlusion in the compressed periodontal ligament.‟‟


Storey and Smith in 1952 found in their experiments that heavy forces ( 400-600gms) caused the anchor teeth to move mesially until the force declined to 200-300gms after which the anchor teeth stopped moving and the canines started moving distally.

• Some tissue damage is unavoidable and is actually beneficial because it evokes inflammation


• BURSTONE Pointed out, in most cases the force distribution in the PDL is uneven, resulting in areas of great strain, as well as areas of little, if any, strain.

• REITAN AND RYGH (1994) suggested interrupted force for orthodontic tooth movement.


• In (1998) BLECHMAN Proposed that static magnets generate Electromagnetic fields which stimulate bone formation in PDL tension sites, thereby reducing tooth mobility, pain and discomfort.

• Combined orthodontic force/Electric stimulation supported Blechman proposition that exogenous electric signals increase the amount of new bone formation in PDL tension sites.

• These observation suggests that an optimal orthodontic force is one accompanied by an additional signal, such as an electric current, which accelerate the rate of alveolar bone formation.


• Searching the orthodontic literature revealed that no publications are available that elucidate the fundamental clinical question about the optimal force.

(Angle Orthod 2003;73:86–92.)


Minimal forces in tooth movements

• Ackerman, cohen (1966)found that forces of 33 to 548 GM/cm2

were sufficient to cause bone resorption.

• Muscle forces of low values as 1.68 Gm above the resting force, if acting over a sufficient, are capable of moving teeth Weinstein (1967)


Four main problems were encountered throughout the literature

1. The first difficulty is the inability to precisely calculate the distribution of stresses and strains at the level of the periodontal ligament.


2) The second problem is that many of the experiments cited failed to control the type of tooth movement. In most experiments, tipping tooth movement has been performed, which means that an uneven distribution of stresses and strains is invoked within the periodontal ligament.


3) The third consideration that contributes to confusion on the relationship between force and rate of tooth movement is that orthodontic tooth movement can be divided into several phases that were categorized by Burstone as initial phase, lag phase, and post lag phase.


Later studies on beagle dogs proposed four phases: initial phase, phase of arrest, phase of start, and linear phase.

4) Finally, a large inter individual variation is recognized in both human research and animal experiments.


To summarize the features of an optimal force:

(According to Ze‟ev Davidovitch)• It should strain Para dental tissues.• It should cause minimal tissue damage.• Its distribution in the PDL and the

alveolar bone is not uniform.• Its distribution depends on anatomical

constraints and type of tooth movement.


• In adults , initially it should be light , to promote It is intermittent and interrupted.

• cellular proliferation.

• Its magnitude should not exceed levels where cell death might occur.


CONCLUSION

It may be concluded that an optimal orthodontic force is one that is applied with full attention to the anatomical constraints and peculiarities of every individual patient.

Issues such as force magnitude, duration, and direction, must be considered individually for each patient, with the clear understanding that anatomical constraints should not be violated or ignored during the correction of a malocclusion.


When potentially damaging movements of dental roots, such as round tripping, uncontrolled tipping, and moving roots into or through labial, buccal, or palatal compact bone plates are avoided, orthodontic forces maybe considered biologically and clinically optimal.


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Optimal orthodontic force /certified fixed orthodontic courses by Indian dental academy