This document discusses face bows, which are dental instruments used to record the spatial relationship between the maxillary arch and anatomical reference points. This relationship is then transferred to an articulator to orient dental casts. There are two main types of face bows - arbitrary and kinematic. Arbitrary face bows approximately locate the hinge axis within 5mm, while kinematic face bows aim to precisely locate the true hinge axis by observing condyle movement. Face bows allow for a more accurate occlusion on articulators when fabricating fixed prosthetics like crowns.

1. FACE BOWFACE BOW
INDIAN DENTAL ACADEMY
Leader in continuing dental education
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2. DEFINITIONSDEFINITIONS
AA face bowface bow is defined as a caliper likeis defined as a caliper like
instrument used to record the spatialinstrument used to record the spatial
relationship of the maxillary arch to somerelationship of the maxillary arch to some
anatomic reference point or points and thenanatomic reference point or points and then
transfer this relationship to an articulator.transfer this relationship to an articulator.
It orients the dental cast in the sameIt orients the dental cast in the same
relationship to the opening axis of therelationship to the opening axis of the
articulator.articulator.
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3. Orientation Jaw relationOrientation Jaw relation
TheThe orientation jaw relationsorientation jaw relations areare
those that orient the mandible to the craniumthose that orient the mandible to the cranium
in such a way that, when the mandible is keptin such a way that, when the mandible is kept
in its most posterior position, the mandiblein its most posterior position, the mandible
can rotate in the sagittal plane around ancan rotate in the sagittal plane around an
imaginary transverse axis (hinge axis) passingimaginary transverse axis (hinge axis) passing
through or near the condyles.through or near the condyles.
This axis can be located or approximatedThis axis can be located or approximated
by the use of a face bow.by the use of a face bow.
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4. Hinge axisHinge axis
It is an imaginary line passing through theIt is an imaginary line passing through the
centre of the condyles when the mandiblecentre of the condyles when the mandible
rotates in the sagittal plane.rotates in the sagittal plane.
This rotation is within 5 to 12This rotation is within 5 to 12ºº. There can be. There can be
multiple axes of rotation. The axis of rotationmultiple axes of rotation. The axis of rotation
that coincides with the centric relation isthat coincides with the centric relation is
called thecalled the True hinge axisTrue hinge axis (THA).(THA).
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5. THATHA should be accurately determined duringshould be accurately determined during
treament with fixed prosthesis. this is nottreament with fixed prosthesis. this is not
required for complete dentures because they arerequired for complete dentures because they are
placed on displaceable tissues (realeff effect).placed on displaceable tissues (realeff effect).
Minor errors in hinge axis rotation duringMinor errors in hinge axis rotation during
fabrication of complete dentures are overcomefabrication of complete dentures are overcome
by this effect. Hence, arbitary face bows areby this effect. Hence, arbitary face bows are
sufficient to record orientation jaw relation forsufficient to record orientation jaw relation for
complete denture patients.complete denture patients.
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6. The components of a face bowThe components of a face bow
are:are:
 U-shaped frameU-shaped frame
 Condylar rods or earpiece.Condylar rods or earpiece.
 Bite forkBite fork
 Locking deviceLocking device
 Third reference point.Third reference point.
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7. U-shapedU-shaped
frameframe
It forms the mainIt forms the main
frame of the faceframe of the face
bow. All otherbow. All other
components arecomponents are
attached to thisattached to this
frame. It extendsframe. It extends
from the region offrom the region of
TMJ on one side toTMJ on one side to
the other sidethe other side
without contactingwithout contacting
the face.the face. www.indiandentalacademy.comwww.indiandentalacademy.com

8. Condylar rodsCondylar rods
Two small metallic rodsTwo small metallic rods
on either side of theon either side of the
free end of the Ufree end of the U
shaped frame thatshaped frame that
contact the skin overcontact the skin over
the TMJ. They arethe TMJ. They are
used to locate the hingeused to locate the hinge
axis and transfer it toaxis and transfer it to
the articulator.the articulator.
Some face bows haveSome face bows have
ear piece that fit into theear piece that fit into the
external auditoryexternal auditory
meatus instead ofmeatus instead of
condylar rods.condylar rods.
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9. Bite forkBite fork
““U” shaped plate,U” shaped plate,
which is attached towhich is attached to
the occlusal rims,the occlusal rims,
while recording thewhile recording the
orientation relation. Itorientation relation. It
is attached to theis attached to the
frame with the help offrame with the help of
a rod called the stem.a rod called the stem.
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10. Locking device.Locking device.
This part of the faceThis part of the face
bow helps to fix the bitebow helps to fix the bite
fork to the U-shapedfork to the U-shaped
frame firmly afterframe firmly after
recording the orientationrecording the orientation
jaw relation.jaw relation.
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11. Third referenceThird reference
pointpoint
It is used to orient theIt is used to orient the
face bow assembly to aface bow assembly to a
anatomical referenceanatomical reference
point on the face alongpoint on the face along
with the two condylarwith the two condylar
reference points. It variesreference points. It varies
in the different facein the different face
bows, example orbitalbows, example orbital
pointer-orbitale, Nosepointer-orbitale, Nose
piece – Nasion etcpiece – Nasion etc..
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12. Classification of face bowsClassification of face bows
1.1. ArbitaryArbitary
a. Fascia Type.a. Fascia Type.
b. Ear piece typeb. Ear piece type
2.2. KinematicKinematic
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13. Arbitary face bowArbitary face bow
 The hinge axis is approximately located in this typeThe hinge axis is approximately located in this type
of face bow.of face bow.
 It is commonly used for complete dentureIt is commonly used for complete denture
construction.construction.
 This type of face bows generally locate the trueThis type of face bows generally locate the true
Hinge axis within a range of 5 mm.Hinge axis within a range of 5 mm.
 As the located hinge axis is arbitary, occclusalAs the located hinge axis is arbitary, occclusal
discrepancies produced in the dentures should bediscrepancies produced in the dentures should be
corrected by minor occlusal adjustments duringcorrected by minor occlusal adjustments during
insertioninsertion.. www.indiandentalacademy.comwww.indiandentalacademy.com

14.  In the Fascia type, the hinge axis is located 13In the Fascia type, the hinge axis is located 13
mm anterior to the external auditory meatus onmm anterior to the external auditory meatus on
the cantho-tragal line.the cantho-tragal line.
 In the Ear piece type, the posterior referenceIn the Ear piece type, the posterior reference
points are the external auditory meatus itself.points are the external auditory meatus itself.
The discrepancies of distance between theThe discrepancies of distance between the
external auditory meatus and the hinge axis isexternal auditory meatus and the hinge axis is
compensated in the articulator by thecompensated in the articulator by the
manufacturer.manufacturer.
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15. Kinematic face bowKinematic face bow
It is used to locate the true terminal hinge axisIt is used to locate the true terminal hinge axis
of the TMJ and transfer this record to theof the TMJ and transfer this record to the
articulator when mounting the maxillary cast.articulator when mounting the maxillary cast.
The fork of the kinematic face bow is attachedThe fork of the kinematic face bow is attached
to the mandibular occlusal rim. Then as theto the mandibular occlusal rim. Then as the
patient retrudes the mandible and opens andpatient retrudes the mandible and opens and
closes the jaws, the dentist observes thecloses the jaws, the dentist observes the
movement of the sharp points of the condyle rods.movement of the sharp points of the condyle rods.
When the points of the condyle rods rotate onlyWhen the points of the condyle rods rotate only
and do not translate, it is located as the terminaland do not translate, it is located as the terminal
hinge axis.hinge axis.
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16. Value of the face bowValue of the face bow
Failure to use a face bow can lead toFailure to use a face bow can lead to
errors in occlusion of the dentures if cusperrors in occlusion of the dentures if cusp
teeth are used.teeth are used.
The face bow allows a more accurate arcThe face bow allows a more accurate arc
of closure on the articulator.of closure on the articulator.
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17. Facebow recordFacebow record
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18. Facebow transferFacebow transfer
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19. Thank you
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