Bio Mechanical Considerations In
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Transcript of Bio Mechanical Considerations In
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Biomechanical Considerations in
Treatment with Miniscrew
Anchorage
Part 1- Sagittal plane
Part 2-Horizontal & Transeverse
planes
MIN-HO JUNG, DDS, MSD, PHDTAE-WOO KIM, DDS, MSD, PHD
J Clin Orthod 2008
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Introduction
Anchorage control is one of the most important aspect oforthodontic treatment.
Traditionally extraoral anchorage has been used to reinforceintraoral anchorage.
But, the disadvantage is the patient co-operation
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Introduction
The use of miniscrews for reinforcement of orthodontic
anchorage has become increasingly popular in recent years .
Especially in adult patients who do not want to wear extraoralappliances
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4
Structure of an ImplantStructure of an Implant
Implant
Head Body
(Serves as)
Abutment in prostheticrehabilitation
Attachment source forelastics & coil springs inorthodontic treatment
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5
The portion that is embedded in the bone is termed as Body.
The Body is divided into 2 types
a) Screw type
b) Plate type
TheportionthatisembeddedintheboneistheBODY
Itisof2types
1.Screwtype
2.Platetype
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Introduction
Property Prosthodontic implant Orthodontic implant
Composition Titanium Titanium
Duration of use Permanent Temporary
Type of load Axial Non axial
Diameter Large Small
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Miniscrews are
convenient,
save time, and
produce good treatment results with no need for patient cooperation.
In some patients treated with miniscrews, however, mechanicalfactors can produce unusual changes or side effects.
The present article explains these mechanical variations andprovides tips for solving the problems
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The sagittal plane
Anchorage reinforcement is most commonly needed in patientswith severe protrusion.
In conventional retraction with sliding mechanics after first
premolar extractions, the molars typically move forward 3.6-3.8mm.
Anterior retraction with sliding mechanics
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What happens when miniscrews are
used for anchorage reinforcement?
ROTATIO
NOF
ENTIRE
ARCH
AROUND COResistance
ROTATIO
NOF
ANTERI
OR
SEGMENT
AROUND COResistance
EITHER OR
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Miniscrews in cases of severe protrusion
DEEP
OVERBITE
POSTERIOR
OPEN BITE
The use of precurved archwires will result in an even stronger intrusive
force on the posterior segment
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Redirecting the Retraction Force
To pass through center ofresistance of the anteriorsegment
Which is located between thelateral incisor and canine roots,
6.76mm above the cervicalarea
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Redirecting the Retraction Force
Limitations :1. Higher line of force
promotes irritation of softtissue by elastomeric chain or
coil springs because ofarchwire curvature
2. Limited width of gingivaltissue precludes highplacement of miniscrew
3. Insertion in the mobilemucosa increases the risk ofinflammation around theminiscrew and may lead to
failure
Optimum position
of the miniscrew
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Posterior Intermaxillary Elastics
Light 3/16" intermaxillaryelastics, worn only at night,can prevent posterior openbite
Not recommended for
patients with vertical skeletalpatterns
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Vertical Retraction Forces
Apically positioned miniscrews andocclusally oriented hooks producemore vertical retraction force
INDICATIONS:
In patients with gummy smiles orother factors favoring intrusion of anentire arch
To control overbite during retractionin cases of deep overbite.
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Anterior Biteplanes
Occlusal plane rotation due to forces ofocclusion can be prevented by bondinganterior bite planes to the lingual surfacesof the anterior teeth at the beginning ofretraction
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Additional Anterior Miniscrews
Additional anterior miniscrewscreate vertical force to counteractocclusal plane rotation and maintaintorque.
In a patient with a gummy smile or
over -erupted upper incisors
Anterior miniscrews positioned between
roots of lateral incisors and canines
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The Horizontal Plane
Center of resistance of anterior and posterior segment ofthe upper arch in horizontal plane
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If the anterior teeth are retracted en masse, each segment movesaround its center of resistance
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If miniscrews are used for anterior retraction, the right and left quadrants rotate around each center of resistance, and
the molars tend to tip palatally
To counteract these effectsTPA and lingual stabilizing arch arenecessary
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Patient with midlinedeviation and occlusal
plane canting
Upper midline shifted to
left of facial midline
Lower midline are shifted
to right of facial midline
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Use of anterior midline elastics increases canting of
occlusal plane.
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Anchorage from upper left and lower right miniscrews used to
correct midline deviation and occlusal plane canting
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Patient with occlusal plane canting and deviation of
upper and lower midlines to right of facial midline.
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Conventional use of miniscrew
anchorage
Increases canting of
occlusal plan
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Miniscrew added in upper anterior region for vertical
correction of occlusal plane canting
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Age / Sex: 32yr/ F
C/O: PROTRUSIVEprofile
H /o: mandibular first
molar extracted in herteenage
class II div 1malocclusion
Overjet : 13mm
Deep overbite
Lower midline deviatedto right
Occlusal plane cant
Upper left quadrant
Lower arch
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Miniscrew anchorage used to retract anterior teeth and
correct occlusal plane canting.
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Long hooks soldered to archwire for bodily movement of maxillary
anterior teeth
Additional miniscrews in the anterior region
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Lower arch
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Age : 26yr/ F
C/o: right TMJ
discomfort andmandibular anterior
crowding
Severe class III molar
relation
Lower midline shifted to
left
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Slight rotation of mandibular occlusal plane and development of overbite
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Conclusion
If the clinician keeps in mind these probable sideeffects which can be caused in the sagittal , horizontaland transeverse planes by the use of miniscrews and
takes proper measures to counteract them , best resultscan be achieved.
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