Prosthetic

1. Face-Bow
and
Articulators

2. Face-bow
• Definitions
• Purpose
• Types
• Uses

3. Definition
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

4. Purpose of the Face-bow
Orient the maxillary cast to the rotational
axis in three planes

5. Using a face-bow will result in the path of
opening and closure (arch of closing) being
the same on articulator as in the mouth.

6. Face-bow
• If a face-bow transfer has been performed, a
change (increase or decrease) of the OVD can be
performed on an articulator

7. Transverse Horizontal Axis
(or “Terminal Hinge Axis”)
Imaginary axis which passes through
each of the mandibular condyles.
It is around this axis that pure rotational
movement of the mandible occurs.
This axis is about 8 mm under the soft
tissues in front of the tragus (on each
side of the face).

8. Types of Face-Bow
Kinematic: Locates the true transverse
horizontal axis of rotation.
Arbitrary: locates the axis by using
anatomical landmarks (utilizes average
measurements to approximately locate
the axis of rotation)

9. Kinematic Face-bow
This facebow is the most accurate.
Requires more elaborate equipment and more time.

11. Arbitrary Face-Bow
• Locates an arbitrary hinge axis by using
anatomical landmarks.
• Is less accurate
• Requires less complicated equipment
and less time.

12. Arbitrary Hinge Axis
Dr. Snow developed a Face-bow which used
arbitrary landmarks on the side of the face to
orient the side rods of the bow.

13. Arbitrary Hinge Axis Location
• Beyron point: a point 13 mm anterior to the
posterior margin of the tragus on the tragus-
canthus line
• Gysi point: a point 13 mm anterior to the anterior
margin of the external auditory meatus on the line
from the upper margin of the external auditory
meatus to the lateral canthus of the eye
• Bergstrom point: a point 10 mm anterior to the
center of a spherical insert in the external auditory
meatus and 7 mm below the Frankfort horizontal
plane.

15. Facia-bow Ear-bow
Indexes to external
auditory meatus and
registers the relation of
the max arch to these and
a horizontal reference
plane.

16. Accuracy of a Face-bow
In 95% of subjects: the arbitrary axis of
rotation lies within a radius of 5 mm from
the true hinge axis.
Weinberg showed that if the location of the
hinge axis is inaccurate by 5 mm, the
occlusion will be affected by 0.2 mm in the
most distal molars.

17. 3rd Point of Reference
• The face-bow orients the maxillary cast to a
reference plane.
• The reference plane requires 3 (three) points
(two on each side of the face and one on the
anterior face).
• The anterior reference point (also known as
3rd point of reference) should be repeatable,
and reproducible

18. 3rd Point of Reference
• Orbitale: the lowest point on the infra-
orbital rim (Spring Bow)
• Nasion (Whip Mix)
• Maxillary incisor incisal edge (Denar)
• Lower edge of the nostril (older Hanau
models)
• Parallel to upper and lower arms of the
articulator

22. Hanau Face-bow

23. When to use a face-bow?
• Cusp teeth are present
• Interocclusal records are made at an
increased occlusal vertical dimension
• The occlusal vertical dimension is subject to
change and alteration in occlusal surfaces
are necessary.

25. “The face-bow remains controversial
because it is not an absolute essential
to good prosthodontics, as the matrix
band is essential to good class II
restoration.”
R. Christensen

26. Articulators
Definition: A mechanical instrument that represents
the temporomandibular joints and jaws, to which
maxillary and mandibular casts may be attached to
simulate some or all mandibular movements.

27. Ideally an articulator replicates what the
patient has:
– Jaw positions and movements
– Angulations (Bennett, Condylar-
protrusive and Lateral)
– Pathways - curved, straight, etc
– Timing of movements
– Orients casts exactly as jaws/arched are
oriented in patients skull
– Same distance between all elements

28. Articulators should be:
– Easy to use
– Accurately reproduces positions and
movements
– Sturdy and reliable
– Suitable for use in a wide variety of areas
- assessment, treatment planning,
fabricate restorations
– Not too expensive

29. Uses of the articulator
– Diagnosis
– Treatment planning
– Communicate with patients/patient
education
– Fabrication of prostheses/restorations

30. Components
– Upper member
– Lower member
– Anterior or Incisal pin
– Condylar Mechanisms
– Intercondylar distance adjustment
– Anterior Guidance Mechanism
– Mounting Ring - guide and retention system

31. Classification of
Articulators
(based on adjustability)
• Class I: non-adjustable
• Class II: semi-adjustable
• Class III: fully adjustable

32. Articulators
Classification based on adjustability
• Non-adjustable also known as plain hinge

33. Articulators
Classification based on adjustability (cont.)
 Semi-adjustable articulators
 can be adjusted to represent
the beginning and end points
of the movement, not the entire path
 arbitrary face-bow
 some accommodation for sideshift
 protrusive and lateral records to program
 Fully adjustable

34. Fully-adjustable Articulator
• better replication of mandibular movements
• records entire movement pathway
• usually uses a kinematic facebow
• accommodates sideshift (lateral translation)

35. Classification of Articulators
• Arcon: the condylar elements are located on the lower
member
• Non-Arcon: the condylar elements are located on the
upper member