Orientation jaw relation/ dentistry jobs

TODC-B'LORE.2005-06

Orientation Jaw Relation

TODC-B'LORE.2005-06

Topics of Discussion

IntroductionDefinitions Review of literature Classification Parts of facebowDiscussionConclusionBibliography

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Introduction

The maxillary arch has a definite 3-dimensional relationship to all condylar motions of the mandible.

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Jaw relations can be classified as

1.Orientation jaw relation

2. Vertical jaw relation

3. Horizontal jaw relation

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Orientation jaw relation

Orientation jaw relations establishes the references in the cranium.

The mandible rotates in the sagittal plane around an imaginary transverse axis passing through or near the condyles.

This axis can be located by means of an instrument called FACEBOW

Orientation Jaw Relations are those relations that orient the mandible to the cranium in such a way that when the mandible is kept in its most retruded position with the maxilla, the mandible moves in sagittal plane around an imaginary transverse axis passing through the centre or near the condyles

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Facebow transfer is the first step in recording the relationship of the maxillary arch to the condylar paths on the articulator.

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Maxillomandibular relationship: any spatial relationship of the maxillae to the mandible; any one of the infinite relationships of the mandible to the maxillae [Gpt-99].

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Transverse horizontal axis: an imaginary line around which the mandible may rotate within the sagittal plane [Gpt-99].

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Retruded contact position: that guided occlusal relationship occurring at the most retruded position of the condyles in the joint cavities. A position that may be more retruded than the centric relation position [Gpt-99].

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Face-bow: 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 articulator. Customarily, the anatomic references are the mandibular condyles transverse horizontal axis and one other selected anterior point; called also hingebow [Gpt-99].

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Review of literature

In 1860 according to Bonwill, the distance from the centre of each condyle to the median incisal point of the lower teeth is 10 cm.

He used this standard for mounting his casts in the articulator.

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In 1866 Balkwill designed an apparatus called “bite- frame”.

In 1880 Hayes used tong like device which he called it “articulating caliper”.

In 1894 George k Bagby devised an apparatus called “bagby jaw gage”.

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Walker invented FACIAL CLINOMETER to determine mandibular movements in 1896.

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A little later, at about the turn of century ALFERED GYSI developed an instrument similar to face bow primarily to record the path of the condyle.

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SNOW introduced face bow in 1899 and majority of the face bow used today are modifications of Snow's face bow.

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CLASSIFICATION OF FACE BOW

Arbitrary Fascia Type

Earpiece TypeTwirl bow

Spring bow

Slidematic

Kinematic

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ARBITRARY FACEBOW

a device used to arbitrarily relate the maxillary cast to the condylar elements of an articulator. The position of the transverse horizontal axis is estimated on the face before using this device [Gpt-99].

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TYPES OF ARBITRARY FACEBOWS

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Fascia Type

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Earpiece Type

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Spring bow

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EAR PLUGS

ANTERIORREFERENCE POINTER

Slidematic

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KINEMATIC FACE BOW

a face-bow with adjustable caliper ends used to locate the transverse horizontal axis of the mandible [Gpt-99].

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Arbitrary vs. Kinematic

Land marks

Chair side time

Facebow fork attachment

Method

Use

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BASIC PARTS OF A FACEBOW

U shaped frame work.Condylar rods. Bite fork.Locking deviceOrbital pointer with clamp (optional). Additional features & parts vary according to types & brands.

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Spring bow

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U shaped frame

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Bite fork

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Bite fork assembly

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Transfer jig assembly

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INDICATIONS OF FACEBOW Balanced occlusion is desired.

Cusp form teeth are used.

Interocclusal check records are used.

Full mouth rehabilitation

Diagnosis & treatment planning.

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Complete maxillary denture opposes a natural dentition

Remounting of dentures

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Is facebow transfer essential in all cd cases?

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It is not required whenMonoplane teeth are used

No alterations to occlusal surface of teeth are done

Articulators that do not accept facebow transfer

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ADVANTAGES OF FACEBOW

Reduce errors in occlusion.

More accurate programming of articulator.

Supports the cast while mounting on the articulator.

Assist in correctly locating the incisal plane

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SOME COMMONLY USED ANTERIOR REFERENCE POINT

Orbitale

Orbital minus 7mm

Nasion minus 23mm

Ala of the nose

43 mm superior from lower border of upper lip (Denar reference plane locator).

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SOME COMMONLY USED POSTERIOR REFERENCE POINT

Bregstrom point

Beyron point

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COMMONLY USED PLANES OF ORIENTATION DURING FACEBOW TRANSFERS

Axis – orbitale plane.

Frankfort plane.

Camper’s plane.

Axis – Nasion plane.

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Pre-requisites for facebow transfer Check for

Lip support Plane of occlusion Reference lines

Midline High lip line Canine line

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Techniques to record face bow A separate transfer record base is

recommended for transferring maxillary cast to articulator

If same record base is used for centric record

transfer record can be made prior to centric record

transfer record can be made after centric record

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PROCEDURE FOR FACE BOW TRANSFER USING ARBITRARY FACEBOW

Posterior reference point is measured and marked. Condylar rod or earpiece is positioned on posterior reference point The locking nuts are then secured.

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The Bite fork is attached to the maxillary occlusal Rim.

Occlusal rim are inserted into patient mouth.

The midline of bite fork should coincide with the midline of the maxillary occlusal rim.

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PROCEDURE FOR FACEBOW TRANSFER USING KINEMATIC FACEBOW

Facebow is attached to the lower jaw by means of clutch. Graph of Grid paper is placed near temperomandibular joint region detects the stylus movement.

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Patient is asked to open and close the mandible at centric. Initial movement of the stylus may be arc shaped. The stylus is adjusted until the tip rotates instead of arcing. This point identified as the hinge axis is tattooed on the skin.

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ERRORS IN RECORDING HINGE AXIS

Movement of the skin over the condyle during registration.

Tipping of Base will invalidate the eventual recording.

The angle of opening movement is small about 10-12 degrees and thus the arc of movement of the stylus is small.

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The bite fork shaft should be at the left of patient’s midline

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Bite fork assembly

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The bite fork clamp is slid onto the shaft

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Open the bow by pulling outward on the arms and then swing it down into position, placing an earpiece gently into each external auditory meatus.

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Have the patient adjust the facebow into a comfortable position.

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The infra orbital notch is located and marked.

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The pointer is rotated toward the reference mark

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The bow is secured with one hand while the thumbscrews on the assembly with the other hand.

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The thumbscrews are tightened in order: 1, 2, 3. from left to right.

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Rotate the orbital pointer away from the eye.

Have the patient remove the earpieces from the auditory meati

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Preparing the articulator for Mounting

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Horizontal condylar inclination

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Lateral condylar inclination

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Centric locks

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Attach the mounting guide / platform to the lower member of the articulator

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Place the vertical transfer rod of the facebow assembly into the hole at the front of the mounting guide and secure it by a screw

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Carefully seat the maxillary cast on the bite fork.

Mounting of the maxillary cast is done.

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CONCLUSION

Though blind orientation of maxillary cast may result in an error so slight that a facebow appears unnecessary, however since the procedure is not complicated, not time consuming, the chances of incorporating an error should not be taken.

Any error that can be eliminated in denture construction will make physiologic acceptance of denture easier.

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BIBLIOGRAPHY Prosthodontic treatment for edentulousProsthodontic treatment for edentulous

patient-(8patient-(8th,th, 11 11thth, 12, 12thth,) ,)

BoucherBoucher Syllabus of Complete Denture- Syllabus of Complete Denture-

Hartwell Hartwell

Essentials of complete denture- Essentials of complete denture-

WinklerWinkler Complete Denture Prosthodontics

John J SharryJohn J Sharry

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The Glossary of Prosthodontic Terms JPD-1953,VOL.3 JPD-1979,VOL.41,NO.5 JPD-2000,VOL.9,NO.3