ORIENTATION JAW RELATION

CONTENTS

• Introduction• Orientation jaw relation• School of thoughts• Face bow record• Conclusion • References

JAW RELATIONThree dimensional spatial relationship of maxilla to the mandible.

According to Boucher , jaw relation can be classified as:A. ORIENTATION JAW RELATION :

Establish reference in the cranium.

B. VERTICAL JAW RELATION:Establish the amount of jaw separation allowable for the denture.

C. HORIZONTAL JAW RELATION:Establish front to back and side to side relation of one jaw to other.

ORIENTATION JAW RELATION• Are those that orient the

mandible to the cranium in such a way, that, when mandible is kept in its most anterior and superior position, the mandible can rotate in sagittal plane around an imaginary transverse axis passing through or near the condyles.

– Boucher 12th Ed.

HINGE AXIS• An imaginary line around which the

mandible may rotate within the sagittal plane. – TRANSVERSE AXIS

– GPT-8

• Any vertical plane or section parallel to the median plane of the body, that divides a body into right and left portions.

GPT -8

TERMINAL HINGE POSITION

• Also called the Retruded contact position, it is that guided occlusal relationship, occurring at the most retruded position of the condyles in joint cavities. GPT -8.

• Maximum range of terminal hinge rotation- about 12˚

• Inter incisal opening: 18-25 mm

FACE BOW

FACE BOW

• A calliper like instrument used to record the spatial relationship of the maxillary arch to some anatomic reference points, and then transfer this relationship to an articulator. (GPT-8)

• It orients the dental cast in same relationship to the opening axis of articulator.

• Customarily the anatomic references are the mandibular condyles transverse horizontal axis and one other selected anterior point.

• Also called Hinge bow, Earbow, Kinematic facebow. (GPT-8)

TYPES OF FACEBOW

• Two basic types– KinematicAnd- Arbitrary

- Facia type - Earpiece type.

PARTS OF A FACE BOW

• U SHAPE FRAME

• CONDYLAR

RODS

• LOCKING

DEVICE

• BITE FORK

• ORBITAL

POINTER

U- SHAPED FRAME

• It is large enough to extent from the region of one TMJ around the front of the face(5 to 7.5 cm in front) to the other TMJ and wide enough to avoid contacts with the sides of the face.

CONDYLAR RODS

• It is the part that contacts the skin near the TMJ.

BITE FORK

• It is that part that attaches to the occlusal rims.

LOCKING DEVICE

• The fork attaches to the face bow by means of a locking device, which also serves to support the face bow, the maxillary occlusal rim and the maxillary cast while the cast are being attached to the articulator.

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 in the arbitrary face-bow.

The spatial plane formed by joining the anterior and posterior reference points.

The horizontal plane is established on the face of the patient by 1 anterior & 2 posterior points, from which measurements of the posterior anatomic determinants of occlusion and mandibular motion are made”.

PLANE OF ORIENTATION

REFERENCE POINT

1. Orbitale (B) Located by Hanau facebow with help of orbital pointer.

2. Orbitale minus 7 mm. (C) This plane represents Frankfort plane.

3. Nasion (A) Used with quick mount facebow (Whip mix)

4. Ala of nose (D) This plane represents campers plane

5. 43 mm superior from lower border of upper lip (Denar reference plane locator – Denar facebow uses this reference point)

ANTERIOR REFERENCE POINTS

ORBITALE

• Lowest Point on the infraorbital rim, palpated through tissue and skin.

• One orbit and two posterior points determine the Axis-Orbital plane. • It is used because of ease of location and the concept is easy to teach and understand.

ORBITALE MINUS 7MM• The F-H plane passes through both porion and orbital point.

• Because porion is a fixed point on the skull it is considered as a posterior landmark on the patient.

• Most articulator do not have reference point of this landmark .

NASION MINUS 23MM

• According to Sicher, another skull landmark Nasion is located in the head as the deepest part of the midline depression just below the level of the eyebrow.

• The nasion guide is designed to be used with whipmix articulator, which fits in the depression.

ALAE OF THE NOSE

• The tentative occlusal plane should be parallel to horizontal plane.

• This can be achieved in 2 ways- The line from the alae of the nose

to centre of the auditory meatus - Camper’s line.

1. Pointer on right or left alae 2. Occlusal rim parallel to camper line ,transfer with face bow .

ADVANTAGES OF ANTERIOR REFERENCE POINT

• Determines which plane in the head will become the plane of reference.

• Determines the level at which the casts are mounted

• To establish a baseline for comparative studies between patient.

• Can visualize anterior teeth & occlusion in the articulator in the same frame of reference.

Posterior reference points

• Posterior reference points

A. Beyron point – 13 mm anterior to

posterior margin of tragus of outer

canthus of eye

B. Gysi – 13mm anterior to anterior

margin of EOM

C. Snow – 11 -13 mm ant to tragus

D. Denar’s – 12 mm ant to post border

of tragus and 5 mm inferior to line

from EOM and outer canthus

POSTERIOR REFERENCE POINTS???

The position of the terminal hinge axis on either side of the face is generally taken as the posterior reference points.

TAKING A FACE BOW RECORD

SEATING THE PATIENT

The Patient is seated in a comfortable position with his head upright and supported by a headrest.

MARKING THE POINTS FOR CONDYLAR POSITION

A point is marked 13 mm in front of the auditory meatus on a line running from the outer canthus to the superior border of tragus.

A notch index about 2mm deep is made in first molar region. This helps to position of facebow.

The maxillary and mandibular occlusal rims are inserted in patient’s mouth.

PREPARATION OF OCCLUSAL RIMS

PREPARATION OF BITE FORK

Aluwax is softened and shaped to the form of a horseshoe. The bite fork is embedded into this soft wax. The thickness of the bite fork and the wax together should not be more than 6mm.

The bite fork with wax is inserted into the patient’s mouth. The midline of the bitefork should coincide with the mid line of the maxillary occlusal rims. The stem of the bite fork should be parallel to the sagital plane.

With bite fork in position face bow is guided onto the stem of the bite fork .

Thumbscrews tightened to maintain the spatial relationships between face bow and bite fork.

PLACING THE FRAME OF FACE BOW

FORK IS TIGHTENED TO FRAME

Face bow assembly along with bite fork is removed from the mouth and positioned in the articulator

KINEMATIC FACEBOW• The kinematic face bow

allows for the precise determination of the patient's hinge axis (terminal hinge axis).

KINEMATIC METHOD OF LOCATING HINGE AXIS

• Fabrication of the clutch. • Attach clutch tray to lower teeth.• Assemble the hinge axis locator.• Attach the side arms to the cross bar in mounting column.• Attach the assembled hinge axis locator to the Stem of the

clutch tray.• Mark approximate center of condyle on the subject`s face.

• Adjust the hinge axis locator.• Place the graph paper .• Location of the hinge axis points.

FACIA TYPE FACE BOW

This face bow takes its name from the fact that it rests upon the face, like the kinematic bow.

EAR PIECE TYPE

• This type of face bows uses the external auditory meatus as an arbitrary reference point which is aligned with ear pieces.

Today there are more advanced techniques that make use of ultrasonic arcs, connected to computers with graphical representations and parameter calculations for programming the articulator.

NEWER ADVANCEMENTS

• A definite cusp fossa or cusp tip to tip incline relation is desired.

• When interocclusal check records are used for verification of jaw positions.

• When the occlusal vertical dimension is subjected to change, and alterations of tooth occlusal surfaces are necessary to accommodate the change.

• To diagnose existing occlusion in patients mouth

INDICATIONS FOR USE OF FACEBOW

SITUATIONS WHERE FACE BOW IS NOT REQUIRED

• Monoplane teeth are arranged in balance occlusion and mandible in most retruded position at acceptable VD.

• No intended change in VDO.

• Articulator doesn't accept the transfer.

CONCLUSION • Failure to use the face bow leads to error in occlusion.

• Hinge axis is a component of every masticatory movement of the mandible and therefore cannot be disregarded and this hinge axis should be accurately captured and transferred to the articulator. So it becomes a fine representative of the patient and biologically acceptable restoration is possible.

• Whatever may be controversy reasoned by in the use of face bow but it should form a integral part of one prosthodontic treatment.

REFERENCE

• Boucher's Prosthodontic treatment for edentulous patient 10th edition.

• Essentials of complete Denture Prosthodontics by Sheldon Winkler-2nd edition.

• Syllabus of complete dentures by Charles M. Heartwell 4th edition 5th edition.

THANK

YOU