صناعة

Face bow: definition and types

صناعة اسنان / د . هند (م 9)
ثاني اسنان موصل

The vertical length of the maxillary occlusion rim

Anteriorly extend 2mm below relaxed lip& oriented to be parallel to inter pupillary line.
Posteriorly the vertical length and occlusal plane are made to be coincide with (Camper's line).
(Camper's line, ala-tragus line) line passing from the lowest point of the ala of the nose to the center of the tragus of the ear.


Face bow:
Definition: is 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.
• The anatomic references are the mandibular condyles, transverse horizontal axis & one other selected anterior point.

Objectives of face bow:

• 1. To record the relationship of the jaws to the opening axis of the jaws and to orient the casts in this same relationship to the opening axis of the articulator.
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• 2. To support the maxillary cast while it is being mounted on the articulator.
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Types of face bow:

• Arbitrary face bows
• Fascia type
• Example:
• - Hanau fascia type face bow.
•
B. Ear piece type
Example:
Hanau ear piece type face bow Hanau spring bow.

• Kinematic face bow or hinge bow

• Example:
• Hanau kinematic face bow.

Arbitrary face-bows

A device used to arbitrarily relate the maxillary cast to the condylar elements of an articulator.


They are based on the average location of the hinge axis, has an error of 2mm of the true center of the true center of the opening axis of the jaws.

The arbitrary rotational center is located over measured points on the face or by some types of earpiece.
The arbitrary type is considered adequate for complete dentures.

Arbitrary face-bows

It is placed on the face, with the graduated condylar rods located in a line extending from the outer canthus of the eye to the top of the tragus of the ear & approximately 13mm in front of the external auditory meatus.

Earpiece face-bow (ear-bow)

An instrument similar to a face-bow that indexes to the external auditory meatus & registers the relation of the maxillary dental arch to the external auditory meatus & a horizontal reference point.

Earpiece face-bow (ear-bow)

Advantages:
• It is a simple instrument to use
• Does not require measurements or marks on the face
• Consumes less time for its use
• It is accurate


Both the face-bow & the ear-bow may use the infraorbital notch ( infraorbital pointer)or the incisal plane as the anterior reference point( or the nasion).
The anterior reference point along with the two posterior reference points form the axis orbital plane, which is transferred to the articulator along with the maxillary cast.

Kinematic face-bow

A face-bow with adjustable calliper ends used to locate the transverse horizontal axis of the mandible.
It is mostly used with fixed prosthodontic procedures.
The patient hinge axis must be located accurately.
When the hinge axis has been determined, it is marked on the skin with an indelible pencil.

Parts of face bow

U-shaped frame or assembly

 Graduated Condyle rods and ear pieces

Bite fork

• 
•
• • They are positioned on the patient at the approximate or absolute location of the hinge axis or opening axis of jaws.
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•

Locking device

• • Locking device helps in attaching bite fork to the face bow.
•
• • It also serves to support the face bow, the maxillary occlusion rim and the maxillary cast while the casts are being attached to the articulator.
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•

Orbital pointer Nasion relator assembly

• 
• • It marks the anterior reference point

Inter condylar scale

• It indicates the inter condylar distance as small, medium and large (S, M, L).