This document discusses jaw relation and provides details about orientation jaw relation, vertical jaw relation, and facebow use. It defines the different types of jaw relations and explains how to record orientation and vertical jaw relations. Orientation jaw relation establishes the maxillary plane and is recorded first using a facebow to transfer the maxillomandibular relationship to an articulator. Vertical jaw relation can be recorded at rest or occlusion and determines jaw separation. Physiologic and mechanical methods are described to establish the vertical dimension.

1. JAW
RELATION
Prepared by:Parvathy Krishnan,
3rd BDS,Roll No -39

2. Contents
Jaw Relation
Orientation jaw relation
Face bow
Vertical jaw relation
Reference

3. Jaw Relation
Jaw relation is defined as, “any relation of the mandible to
the maxilla”
-GPT
● There are three different types of jaw relations they
are listed in order of the procedure:
○ Orientation jaw relation
○ Vertical jaw relation
○ Horizontal jaw relation

4. Orientatio
n jaw
relation
● It is defined as “the jaw relation when the
mandible is kept in its most posterior position, it
can rotate in the sagittal plane around an
imaginary transverse axis passing though or near
the condyles”
- GPT
● This record gives the angulation of the maxilla in
relation to the base of the skull.It is necessary to
carry out orientation jaw relation before other jaw
relations.

5. -To record the
inclination of
maxilla, a plane
should be formed
with two
posterior (centre
of both condyles
A and B) and one
anterior
point – here
infraorbital notch
C is used as
anterior reference
point.

6. -Facebow is used to
determine the inclination
of maxilla by forming a
plane (a–c) using the
centre of the two condyles
(a and c) as posterior
references and infraorbital
notch (b) as anterior
reference.
-The centre of condylar
rotation is also determined
and the same is transferred
to the articulator.
- Once the maxilla is
oriented, the mandible is
oriented with the maxilla
using centric and eccentric

7. Face-bow
● It is defined as “ A caliper like device which is used to record
the relationship of the jaws to the temporomandibular joints
and to orient the casts on the articulator to the relationship of
the opening axis of the temporomandibular joint”
-GPT
● The parts of a face-bow are
○ U-shaped frame
○ Condylar rods
○ Bite fork
○ Locking device
○ Orbital pointer with clamp

8. Types of face-bows
Face-bow can be classified as
Arbitrary face-bow
• Facia type
• Earpiece type
• Hanau face-bow (Spring bow)
• Slidematic (Denar)
• Twirl bow
• Whipmix
Kinematic or hinge bow

9. ARBITARY FACE BOW
-Also called ‘Average axis facebow’
-Hinge axis approximately located,It
positions the rods within 5 mm of
true centre of rotation of condyle.
-Commonly used and preferred for
fabrication of complete denture.

10. FASICA TYPE
In this type of face bow the posterior reference point is 13 mm
anterior to the external auditory meatus and the anterior
reference point is the orbitale.Face bow has a pointer that can
be positioned to the posterior reference point.
EARPIECE TYPE
● In this type the external auditory meatus is considered as
referral point to determine the centre of condylar rotation.
● Anterior reference point is orbitale and earpiece engage in
posterior reference point.

11. KINEMATIC FACEBOW
-With the adjustable caliper end that locates the true
centre of condylar rotation
-Used for full mouth reconstruction and requires fully
adjustable articulator.
-Like facia type condylar rods are 13mm anterior to
external auditory meatus on canthotragal line.

12. PARTS OF FACE-BOW
1. U-shaped frame
• It is a U-shaped metallic frame, to
which all the other components of
the facebow are attached .
• It extends from the TMJ of one side to
the TMJ of the other side, at
least 2–3 inches anterior to the face to
avoid contact.
2. Condylar rods
• These are two calibrated metal
extensions fitted on either side of the
free end of the U-shaped frame that are
placed on the determined
centre of condyle.
• The calibrations on either side are
equalized (to centre the facebow)
and then locked.

13. • It is a U-shaped rod which is attached to the maxillary
occlusal rim
while recording the orientation jaw relation.
• It is attached to the frame with the help of a metal rod called
the
‘stem’.
• The bite fork should be inserted about 3 mm above the
occlusal
surface into the occlusal rim.
• Sometimes the bite fork is attached to the occlusal surface of
the
occlusal rim with the help of impression compound. This is
done in
order to preserve the occlusal rim.

14. Locking Device
○ This part of the face-bow that
helps attach the bite fork to the
U-shaped frame.
○ There is locking clamp for bite
fork,locking clamp for orbital
pointer pin and locking screw for
condylar rods.

15. Orbital Pointer:
○ It is designed to mark the anterior reference point
(infraorbital notch) and can be locked in position with a
clamp.
○ It is present only in the arbitrary face-bow

16. Face-bow Transfer
• Facebow record
• Facebow mounting
Clinical procedure for recording orientation jaw relation (using
facia type)
• The maxillary occlusal rim is inserted into the patient’s mouth and
contoured
• A point 13 mm from tragus of the ear on the canthotragal line is
marked on both sides .
• The bite fork is flamed and attached anteriorly to the maxillary
occlusal rim, 3 mm above the incisal plane and parallel to the
occlusal plane .The maxillary rim with the attached bite
fork is inserted into the patient’s mouth. The parallelism and
centring of the attached bite fork are verified.
• The U-frame is supported by two fingers and gently rotated and
inserted into the stem of the bite fork in the patient’s mouth .
• The condylar rods are unlocked and the condylar heads are then
placed in the patient’s right and left condylar centres on the
previously marked points.
.

17. • The third point of reference (infraorbital notch) is palpated and the
orbital pointer is set to the third point of reference .
• The condylar rod readings are equalized on both sides and the
locking screws are tightened. Following this, the orbital pointer is
also tightened in position.
• Once the entire apparatus is in position, the condylar rods, orbital
pin and the bite fork are verified for any movement, alignment and
parallelism.
• The contoured mandibular occlusal rim may be used during the
transfer to stabilize the maxillary rim. The facebow record is
removed from the patient by loosening only the condylar screws
. The record is now ready to be mounted on the
articulator. This completes the facebow transfer and then it is
transferred to the articulator.

20. Mounting on the articulator
• The articulator is programmed first (zeroing of articulator): The
incisal guide pin is set to correct jaw separation and the anterior
stop screws are tightened first. Next the horizontal condylar
inclination is set at 40° and the Bennett angle at 20° .
•The condylar rods are attached to the auditory pins. The bite fork
is
stabilized on the tilting support bar provided and the orbital pin is
made to coincide with the orbital axis plane indicator.
• The incisal pin is locked with its lock screw at zero on calibration
and the incisal table is set horizontally.
• The upper member of the articulator is swung open, plaster is
mixed
and placed on the cast and the upper member is closed slowly,
until
the incisal pin fully touches the incisal table and upper mounting
plate is covered with plaster.
• Excess plaster is trimmed once the plaster is set. Facebow
is now removed by loosening all the locking devices.

22. Vertical Jaw Relation
● It is defined as, “The length of the face as determined by
the amount of separation of the jaws under specified
conditions”. - GPT
● If the vertical dimension is altered there will be severe
discomfort in both the TMJ and the muscles of mastication.

23. ● Vertical Jaw Relation can be Recorded in Two Positions
○ Vertical dimension at rest position
○ Vertical dimension at occlusion
● In a normal dentulous patient, the teeth do not maintain contact
at rest.
● The space between the teeth at rest is called the ‘free-way
space’ which is around 2-4 mm.

24. Vertical Dimension at Rest
● It is defined as, “The length of the face when the mandible is in rest
position” -GPT.
● This is the position of the mandible in relation to the maxilla when
the maxillofacial musculature are in a state of tonic equilibrium.
● This position is influenced by the muscles of mastication, muscles
involved in speech, deglutition and breathing.
● It can be calculated by
VD at rest = VD at occlusion + free-way space.
(VD—Vertical dimension)

25. Facial measurements
The vertical dimension at rest is calculated by making
facial
measurements.
Two marks are commonly placed, one on the tip of the
nose and other on the chin directly below the nose
marking. The markings can be made with an indelible
marker or pieces of adhesive tape

26. The following methods are
used to make the patient
assume the
postural rest position:
(i) Swallowing: The
patient is instructed to drop
the shoulders, wipe
his/her lips with tongue,
swallow and close the
mouth. This makes the
mandible assume the rest
position, which is
immediately measured.

27. (ii) Tactile sense: The patient is instructed to open the
mouth wide
until strain is felt in the muscles (may be for 1–2 min).
They are then asked to close the mouth slowly until
they feel comfortable and relaxed. Measurement is
made in this position.
(iii) Phonetics: The patient is instructed to repeatedly
say words that contain the letter ‘m’. The lips meet
when this is pronounced and the patient is instructed to
stop all jaw movements when this happens.
Measurement is made between the two points of
reference.

28. (iv)Facial expression: The following indicates rest position:
○ Lips are even anteroposteriorly with slight contact.
○ Skin around the eyes and chin is relaxed.
○ Relaxation around the nostrils with unobstructed
breathing.

29. Measurement of anatomical landmarks
Distance from pupil of eye to rims
oris (B) should be equal to distance
from anterior nasal spine to lower
Border of mandible (A) when
mandible is at rest position,This is
known as Wills Guide.

30. Vertical Dimension at Occlusion
1. It is defined as, “The length of the face when the
teeth (occlusal rims, central-bearing points, or any
other stop) are in contact and the mandible is in
centric relation or the teeth are in centric relation” –
GPT.
2. Vertical dimension at occlusion can be recorded
using the following methods:
-Physiologic
-Mechanical

31. Physiologic Methods
(i)Niswonger’s Method
-Niswonger stated that:
VD at Occlusion = VD at rest – freeway space (2–4 mm)
-Hence, the physiologic rest position is first determined. The
contoured maxillary occlusal rim is placed in the patient’s mouth and
the vertical dimension at rest is determined using facial measurements
-The mandibular occlusal rim is then inserted
and it is trimmed and contoured until it meets the maxillary rim
evenly. The lower rim is adjusted till the facial measurement in
occlusion is 2–4 mm less than that in rest position.

32. -This will provide for the necessary interocclusal space or freeway
space.
-The same can be verified by asking the patient to part the lips
without
moving the jaws at rest position, with the occlusal rims inserted.

33. (ii) Swallowing threshold
The concept that maxillary and mandibular teeth come into light
contact at the beginning of the swallowing cycle is used as a
guide to determine occlusal vertical dimension.
The procedure involves building a cone of soft wax on the lower
denture base in such a way that it contacts the upper occlusion
rim when the jaws are open.
Flow of saliva is stimulated by a piece of chocolate. The lower
wax cone is softened and the patient is asked to repeat the
action of swallowing.
This will gradually reduce the height of the wax cone until it just
touches the upper rim while swallowing. However, this method
has not proven to be consistent.

34. (iii)Phonetics
Closest speaking space.
Position of the anterior teeth govern the vertical separation between
them
during pronunciation of ‘ch’, ‘s’ and ‘j’.
Incorrect positioning will result in obliteration or opening of this space
(closest
speaking space) which will result in altered pronunciation of
these words. This is known as Silverman’s Closest Speaking Space.

35. (iv) Neuromuscular perception
• Central bearing device (tactile sense): This utilizes the tactile
sense
of the individual to establish the vertical dimension.
• Power point (maximum biting force): Boos (1940)
demonstrated
that the maximum biting force in an individual is registered at
vertical dimension at rest

36. (v) Aesthetics
The vertical dimension also affects aesthetics. When the
vertical
dimension is increased, the skin of the lips appears stretched
compared to the skin over other parts of the face . The skin
appears more flaccid with a decreased vertical dimension.
The
contour of the lips is also distorted with a change in vertical
Dimension.

37. Mechanical Methods
(i) Ridge relations
• Incisive papilla to mandibular incisors: The incisive papilla
is a stable landmark whose position changes very little with
resorption of the alveolar ridge. The distance of the papilla
from the incisal edges of the mandibular anterior teeth should
be on an average, approximately 4 mm in CO .
• Ridge parallelism: Parallelism of the maxillary and
mandibular ridges with a 5° opening in the posterior region
provides a guide of appropriate vertical dimension.

38. (ii) Pre-extraction records
These records can be prepared prior to the extraction of teeth and
can be used as a guide to verify the vertical dimension of occlusion
during the fabrication of complete dentures.
• Profile photographs
• Profile silhouettes
• Radiographs
• Articulated cast
• Facial measurements
(iii) Measurement of former dentures
The old dentures are placed in the mouth and using facial
measurements the vertical distance is measured. This can be done
during the jaw relation appointment for the new dentures.

39. Effects of increase or decrease of
vertical jaw relation

40. Reference
● Textbook of Prosthodontics- Deepak Nallaswamy
● Textbook of Prosthodontics -V Rangarajan

41. THANK YOU