Facebow in orthodontics /certified fixed orthodontic courses by Indian dental academy
INDIAN DENTAL ACADEMY
Leader in continuing dental education
A face bow is defined as a caliper like
instrument used to record the spatial
relationship of the maxillary arch to some
anatomic reference point or points and then
transfer this relationship to an articulator.
It orients the dental cast in the same
relationship to the opening axis of the
Orientation Jaw relation
The orientation jaw relations are
those that orient the mandible to the cranium
in such a way that, when the mandible is kept
in its most posterior position, the mandible
can rotate in the sagittal plane around an
imaginary transverse axis (hinge axis) passing
through or near the condyles.
This axis can be located or approximated
by the use of a face bow.
It is an imaginary line passing through the
centre of the condyles when the mandible
rotates in the sagittal plane.
This rotation is within 5 to 12º. There can be
multiple axes of rotation. The axis of rotation
that coincides with the centric relation is
called the True hinge axis (THA).
THA should be accurately determined during
treament with fixed prosthesis. this is not
required for complete dentures because they are
placed on displaceable tissues (realeff effect).
Minor errors in hinge axis rotation during
fabrication of complete dentures are overcome
by this effect. Hence, arbitary face bows are
sufficient to record orientation jaw relation for
complete denture patients.
The components of a face bow
Condylar rods or earpiece.
Third reference point.
It forms the main
frame of the face
bow. All other
attached to this
frame. It extends
from the region of
TMJ on one side to
the other side
Two small metallic rods
on either side of the
free end of the U
shaped frame that
contact the skin over
the TMJ. They are
used to locate the hinge
axis and transfer it to
Some face bows have
ear piece that fit into the
meatus instead of
“U” shaped plate,
which is attached to
the occlusal rims,
while recording the
orientation relation. It
is attached to the
frame with the help of
a rod called the stem.
This part of the face
bow helps to fix the bite
fork to the U-shaped
frame firmly after
recording the orientation
It is used to orient the
face bow assembly to a
point on the face along
with the two condylar
reference points. It varies
in the different face
bows, example orbital
piece – Nasion etc.
Classification of face bows
a. Fascia Type.
b. Ear piece type
Arbitary face bow
The hinge axis is approximately located in this type
of face bow.
It is commonly used for complete denture
This type of face bows generally locate the true
Hinge axis within a range of 5 mm.
As the located hinge axis is arbitary, occclusal
discrepancies produced in the dentures should be
corrected by minor occlusal adjustments during
In the Fascia type, the hinge axis is located 13
mm anterior to the external auditory meatus on
the cantho-tragal line.
In the Ear piece type, the posterior reference
points are the external auditory meatus itself.
The discrepancies of distance between the
external auditory meatus and the hinge axis is
compensated in the articulator by the
Kinematic face bow
It is used to locate the true terminal hinge axis
of the TMJ and transfer this record to the
articulator when mounting the maxillary cast.
The fork of the kinematic face bow is attached
to the mandibular occlusal rim. Then as the
patient retrudes the mandible and opens and
closes the jaws, the dentist observes the
movement of the sharp points of the condyle rods.
When the points of the condyle rods rotate only
and do not translate, it is located as the terminal
Value of the face bow
Failure to use a face bow can lead to
errors in occlusion of the dentures if cusp
teeth are used.
The face bow allows a more accurate arc
of closure on the articulator.