Face-bow

Dental instrument used in prosthodontics

A face-bow is a dental instrument used in prosthodontics to record the spatial relationship of the maxillary arch to some anatomic reference point or points and then transfer this relationship to an articulator.

Purpose

The primary purpose of a face-bow is to orient the dental casts in the same relationship to the opening axis of the articulator as the maxillae relate to the opening axis of the temporomandibular joint (TMJ) in the patient. This is crucial for the accurate fabrication of dental prostheses such as dentures, crowns, and bridges.

Components

A typical face-bow consists of several key components:

• Bite fork: This is inserted into the patient's mouth and is used to record the maxillary arch.
• U-shaped frame: This frame is positioned around the patient's face and is used to stabilize the bite fork.
• Transfer jig: This component is used to transfer the recorded relationship to the articulator.

Types

There are two main types of face-bows:

• Arbitrary face-bow: This type uses average anatomical landmarks to approximate the position of the maxilla relative to the TMJ.
• Kinematic face-bow: This type is more precise and locates the true hinge axis of the mandible.

Procedure

The procedure for using a face-bow involves several steps:

1. Preparation: The patient is seated comfortably, and the bite fork is prepared with an impression material. 2. Recording: The bite fork is inserted into the patient's mouth to record the maxillary arch. 3. Positioning: The U-shaped frame is positioned around the patient's face, and the bite fork is attached to it. 4. Transfer: The recorded relationship is transferred to the articulator using the transfer jig.

Clinical Significance

Using a face-bow ensures that the dental prosthesis will function properly in the patient's mouth by accurately replicating the patient's jaw movements. This is essential for the comfort and functionality of the prosthesis.

Limitations

While face-bows are valuable tools, they have limitations. The arbitrary face-bow may not always accurately represent the true hinge axis, leading to potential discrepancies in the final prosthesis.

Related pages

• Articulator
• Dental prosthesis
• Temporomandibular joint

A face-bow used in dental practice