DEFINITION
Anchorage in orthodontics as the nature and degree of resistance to displacement offered by an anatomic unit for the purpose of tooth movement. (GRABER)
Anchorage is the site of delivary from which force is exerted(White and Gardnier)
CLASSIFICATION(MOYERS)
ACCORDING TO MANNER OF FORCE APPLICATION
SIMPLE STATIONARY RECIPROCAL
ACCORDING TO JAWS INVOLVED
INTER MAXILLARY INTRA MAXILLARY
ACCORDING TO SITE
INTRA 0RAL EXRAORAL MUSCULAR
INTRA ORAL;-TEETH,ALVEOLAR BONE,BASAL BONE
EXTRA ORAL;-CERVICAL,OCCIPITAL,CRANIAL,FACIAL
MUSCULAR
According to number of anchorage units;-single or primary,compound,multiple or reinforced
CLASSIFICATION cntd….
INTRA ORAL ANCHORAGES
1) teeth
2)alveolar bone
3)basal bone
4)musculature
TEETH
WHEN ONE TEETH MOVES THE OTHERS CAN ACT AS ANCHORAGE UNITS,IT DEPENDS ON
-ROOT FORM
-ROOT SIZE
-NO OF ROOTS
-ROOT LENGTH
-ROOT INCLINATION
ROOT FORM
FLAT-RESIST MOVEMENTS IN MESIO-DISTAL DIRECTION,BUT LITTLE RESISTANCE BUCCOLINGUALLY
EG;-MANDIBULAR INCISORS AND MOLARS,BUCCAL ROOT OF MAXILLARY MOLARS
ROUND:-RESIST HORIZONTALLY DIRECTED FORCE IN ANY DIRECTION
EG;-BICUSPID,PALATAL ROOT OF UPPER MOLARS
TRIANGULAR;-MAXIMUM ANCHORAGE
EG;-CUSPIDS,MAXILLARY CENTRALS AND LATERALS
SIZE AND NUMBER OF ROOTS
MULTIROOTED TEETH HAVING THE MAXIMUM SIZE HAVE MAX. ANCHORAGE
ROOT LENGTH ;- DIRECTLY PROPOTIONAL TO ANCHORAGE
AXIAL INCLINATION ;-ANCHORAGE IS MORE WHEN FORCE EXERTED IS OPPOSITE TO THAT OF AXIS OF INCLINATION OF TEETH
ANKYLOSED TEETH ;-NO PDL, SO NO MOVEMENT-EXCELLENT ANCHORAGE
ALVEOLAR BONE
ALVEOLAR BONE RESIST TOOTH MOVEMENT UP TO ITS LIMIT,BEYOND THAT IT ALLOW TOOTH MOVEMENT BY REMODELLING
HEALTHY ALVEOLAR BONE-MORE ANCHORAGE
BASAL BONE
CERTAIN AREAS ACT AS RESISTANCE AREAS-PROVIDE GOOD ANCHORAGE-HARD PALATE,LINGUAL SURFACE OF MANDIBLE
MUSCULATURE
HYPERTONIC LABIAL MUSCULATURE USED FOR ANCHORAGE IN LIP BUMPER
EXTRA ORAL
1)CRANIUM(OCCIPITAL OR PARIETAL ANCHORAGE:-ANCHORAGE OBTAINED FROM OCCPITAL OR PARIETAL BONE
EG:-HEAD GEAR TO RESTRICT MAXILLARY GROWTH
2)CERVICAL:-ANCHORAGE FROM CERVICAL OR NECK REGION
EG:-CERVICAL HEAD GEAR
3)FACIAL BONES:- FACE MASK USED TO PROTRACT MAXILLA TAKE ANCHORAGE FROM MANDIBULAR SYMPHYSIS
REVERSE HEAD GEARS TAKE ANCHORAGE FROM FOR HEAD AND CHIN
head gear cervical head gear face mask
SIMPLE ANCHORAGE
IS THE DENTAL ANCHORAGE SUCH THAT MANNER AND APPLICATION OF FORCE IS SUCH THAT IT TENDS TO CHANGE THE AXIAL INCLINATION OF THE TEETH
THE RESISTANCE OF ANCHORAGE UNITS TO TIPPING IS USED TO MOVE OTHER TEETH
THE COMBINED ROOT SURFACE AREA OF THE ANCHORAGE UNIT MUST BE DOUBLE TO THAT OF TEETH TO BE MOVED
EG:-PALATALY PLACED PREMOLAR IS PUSHED IN TO THE ARCH BY REST OF THE TEETH AS ANCHOR UNITS
simple anchorage
STATIONARY ANCHORAGE
MANNER AND APPLICATION OF FORCE TEND TO DISPLACE THE ANCHORAGE UNIT
RESISTANCE PROVIDED BY THE ANCHORAGE UNITS IS AGAINST BODILY MOVEMENTS(DISPLACEMENT)
RECIPROCAL ANCHORAGE
RESISTANCE OFFERED BY TWO MALPOSED UNITS WHEN THE APPLICATION OF TWO EQUAL AND OPPOSITE FORCES TEND TO MOVE EACH UNIT TO A MORE NORMAL POSITION
EG:-CLOSURE OF MIDLINE DIASTEMA
CROSS BITE ELASTICS,EXPANSION APPLIANCES
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