orientation jaw relations & face bow

Orientation Jaw Relations & Face-Bow

Dr Rohan Bhoil

Contents

• Introduction• Orientation relation• Facebow record• Review of literature• References• Conclusion

Introduction – Orientation Relations

Jaw Relation Orientation Relation

Vertical Jaw Relation

Horizontal Jaw Relation

Definition

• Jaw Relation:

Any one of the infinite spatial relationship of the maxilla to the mandible.

• Jaw relation record

A registration of any positional relationship of the mandible relative to the maxillae. These records may be made at any vertical horizontal or lateral orientation.(GPT-8)

Orientation relations

• Are those that orient the mandible to the cranium in such a way, that, when mandible is kept in its most posterior position, the mandible can rotate in sagittal plane around an imaginary transverse axis passing through or near the condyles.

– Boucher 10th Ed.

• This axis can be located by means of a Kinematic Facebow or hinge bow, or it can be approximated by the use of an arbitrary type of facebow.

Transverse hinge axis

• An imaginary line around which the mandible may rotate within the sagittal plane.

– GPT-8

Sagittal plane

• 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

Facebow

• A caliper 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)

Facebow (definition contd..)

• 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)

Parts of a facebow

Parts of face-bow• U shape frame

31 Jul 06

Condylar Rods\ Earpiece

Bite Fork

Locking device

Orbital pointer

Planes and facebow

• Planes are the flat section defined by atleast three points in space.

• Facebow captures the relationship between occlusal plane and the horizontal reference.

Plane of orientationThe 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”.

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)

VARIOUS 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.

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Posterior reference points

• Posterior reference points

– A---Beyron point – 13 mm ant to

post margin of tragus of outer

canthus of eye

– B---Gysi – 13mm ant to ant 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

Facebow record

• Accurate mounting - three points

• Criteria for selection of points

– Ease of location

– Convenience

– Reproducibility

Taking a face bow record

• Seating the patient

• Marking the points for condylar position

• Attach fork to occlusal rims

• Placing the frame of face bow

• Reading on condylar rod scales are made equivalent

• Anterior reference point is recorded

• Fork is tightened to frame

• Face bow is removed and record transferred to articulator

PROCEDURE TO RECORD ARBITRARY HINGE AXIS

1. BITE FORK PREPARATION Dentulous

Edentulous patient

2. Bow preparation

3. PATIENT APPLICATION

TO RECORD ARBITRARY HINGE AXIS

uuuuUse of kinematic bow for edentulous patients

MOUNTING ON ARTICULATOR

Direct mounting

Indirect mounting

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Errors in face bow recording

• Movement of the skin

• Unstable edentulous ridges

• Angle of opening is small – 10º--12º

• Inter-observer error

Types of facebow

• Two basic types– KinematicAnd- Arbitrary

- Facia type - Earpiece type.

Kinematic facebow• The kinematic face bow

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

Arbitrary face bow

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• Uses arbitrary or approximate points on the face as the posterior points and condylar rods are positioned on these points.

• They are a widely used type of face bow and are sufficient for fabrication of most complete denture, fixed partial and removable partial denture.

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Facia type face bow

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

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Ear piece type

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

• Articulators whose programming make use of arbitrary Ear bow type face bows feature an artificial correction whereby the position of the bow, which should be placed behind the actual hinge axis, is moved forward by about 11-13 mm, or rather by the average distance between the acoustic meatus and the terminal hinge axis.

Spring bow (Hanau’s face bow)• It is an earpiece face bow made of spring steel

and simply springs open and close to various head widths.

• Most commonly used face bow.

• This instrument is designed to orient the occlusal plane to the Frankfort horizontal plane by means for a third point of reference

• The one piece design of bow eliminates the moving parts and maintenance problems encountered with other models.

• Easy and efficient to use.

• Sterilazable parts.

• Direct/indirect mounting capability.

• However, the inter condylar distance cannot be measured with this.

Twirl bow

• It is an earpiece type of face bow

• Allows the maxillary arch to be transferred to the articulator without physically attaching the face-bow to the articulator

• Relates the maxillary arch to FH plane

Slidematic face bow• Type of ear piece Face bow.

• Used with Denar articulator.• It has an electronic device that gives reading

denoting one half of the inter condylar distance.

Whip mix face bow

• Ear piece type of face bow• It has a built in hinge axis locator.• Automatically locates the hinge axis when the

ear pieces are placed in the external auditory meatus

• Has a nasion relator assembly with a plastic nose piece

Newer advancements 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.

• 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

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Advantages of using face bow

“Lazzari”

• It aids in securing the antero-posterior cast position with relation to condyles of the mandible.

• It acts as an aid in the vertical positioning of the cast on the articulator.

• It assists in correctly transferring the inclination of the occlusal plane to the articulator.

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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

Concepts &Review of literature

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Need for Orientation Relations

Recording the transverse hinge axis•Mandibular hinging movement around the transverse hinge axis is repeatable

•It is a starting point of lateral movements

•Opening and closing movements of the mandible are reproduced in the articulator .

Controversies regarding hinge axis

• Controversies have arisen over the presence of a single axis,

• the methods used to locate the axis, • the method and validity of recording the

positions on the skin for future reference,• and the relation of the terminal hinge

position to the position of centric relation.

Four main schools of thoughts

• Group 1 --- Absolute location of hinge axis. -----McCollum(1939)

• Group 2 --- Arbitrary location of hinge axis ------Craddock

& Simmons(1952) • Group 3 -- Non believers in transverse hinge axis location.

------Beck(1959) • Group 4 -- Split axis rotation -----Slavens(1961)

Accuracy in locating a true hinge axis

- Kurth and Feinstein said within 2 mm when restricting opening to ¾ inch at the incisal pin.

- Borgh and Posselt said within 1.5 mm when a 10 degree arc was used and within 1.0 mm when a 15 degree arc was used.

- Lauritzen and Wolford were able to achieve an accuracy of 0.2 mm when using a 10 degree arc of movement.

A method to locate true hinge axis

• Observing the motion of a stylus on a kinematic bow, as created by jaw movements, in relation to a flag fixed over the patients axis area. When the stylus no longer translates but rotates then the point is accepted.

Accuracy of an arbitrarily selected axis• Scallhorn found that 95% of the axis points

located 13 mm anterior to the posterior margin of the tragus on the tragus-canthus line to be within a 5 mm radius of the kinematically located axis.

• Beyron found that approximately 87% of the located points were within a 5 mm radius of the arbitrary points.

• Lauritizen and Bodner found only 33% of the true axis points to be located with in a 5 mm radius of the arbitrary points. Teteruck and Lundeen found similar results.

• Walker found that 20% of the true axis points were located within 5 mm from the arbitrarily selected point.

• Palik, Nelson, and White found that the earpiece face-bow related the maxillary cast to the hinge axis only 50% of the time. 92% of the time the arbitrary axis was located anterior to the terminal hinge axis.

• Preston, J. D ---- A single transverse horizontal axis can usually appear to be located. (within the limits of accuracy of operators, equipment and patients.)- When a kinematic axis is located, this is a worthwhile clinical procedure to transfer the arc of rotation in the sagittal plane from patient to the articulator

• Preston, J. D. A reassessment of the mandibular transverse horizontal axis theory. J Prosthet Dent 41: 605-613, 1979.-

• Granger, E. R. - The hinge axis determines the arc of closure in every contacting position of the teeth. The path of closure is different from each open position of the mandible to tooth contact. This path results from the closing rotation combined with a gliding path of the axis.

• Granger, E. R. Clinical Significance of the Hinge Axis Mounting. DCNA, Mar 1959:205-213.

History of the face bow

• In 1860 Bonwill concluded that the distance from the center of

the condyle to the median incisal point of the lower teeth is

10 cm, but, he did not mention at what level below the

condylar mechanism the occlusal plane should be situated.

• In 1866 Balkwill demonstrated an apparatus to measure the

angle formed by the occlusal plane of lower teeth & the plane

passing through the condyles & incisal plane of lower teeth.

In 1880 Hayes constructed

an apparatus called Caliper

with median incisal point

localized in relation to the

two condyles.

In 1890 Walker invented

Clinometer used to

obtain the relative

position of the lower cast

in relation to the condylar

mechanism

Gysi constructed an instrument for registering the condylar path & used as face bow also.

Snow , 1899 , constructed simple instrument which has become prototype for all the face bows constructed in present days.

Facebow

Stansberry (1928) was dubious aboutthe value of facebow and adjustablearticulators. He thought that since an openingmovement about the hinge axis tookthe teeth out of contact the use of theseinstruments was ineffective except for thearrangement of the teeth in centric occlusion.

Mclean (1937) stated that the hingeportion of the joint is the great equalizerfor disharmonies between thegnathodynamic factors of occlusion. Whenocclusion is synthesized on articulator withoutaccurate hinge axis orientation, theremay be minor cuspal conflicts, which mustbe removed by selective spot grinding.

Kurth LE, Feinstein IK (1951) with aid of articulator and working model, demonstrated

that more than one point may serve as a hinge axis and concluded that an infinite number of points exist which may serve as hinge points.

Craddock and Symmons (1952) consideredthat the accurate determination ofthe hinge axis was only of academic interestsince it would never be found to bemore than a few millimeters distance formthe assumed center in the condyle itself.

Sloane(1952) stated “the mandibularaxis is not a theoretical assumption, but adefinite demonstrable biomechanical fact.It is an axis upon which the mandible rotatesin an opening and closing functionwhen comfortably, not forcibly retruded.

Bandrup-Morgsen (1953) ,discussedthe theory and history of face bows. Hequoted the work of Beyron who had demonstratedthat the axis of movement ofthe mandible did not always pass throughthe centers of the condyles. They concludedthat complicated forms of registration wererarely necessary for practical work.

Lazarri (1955) gave application of Hanau model ”c” facebow.

Sicher (1956) stated “the hinge position or terminal hinge position is that position of

the mandible from which or in which pure hinge movement of a variable wide range is possible”

Robert.G.Schallhorn (1957), (studying the arbitrary center and kinematic center of the mandibular condyle for face bow mountings. He concluded that using the arbitrary axis for face bow mountings on a semiadjustable articulator is justified. He said that, in over 95% of the subjects the kinematic center lies within a radius of 5 mm from the arbitrary center.

Brekke (1959) in reference to a single intercondylar transverse axis stated “unfortunately this optimum condition does not prevail in mandibular apparatus, which is symmetric in shape and size, and has its condyloid process joined at the symphysis, with no connection directly at the condyles. The assumption of a single intercondylar transverse axis is, therefore open to serious question”.

Christiansen RL (1959) studied the rationale of facebow in maxillary cast mounting and concluded that it is advantageous to simulate on the articulator the anatomic relationship of the residual ridges to the condyles for more harmoniously occluding complete dentures.

Weinberg (1961) evaluated the facebow mounting and stated that a deviations from the hinge axis of 5mm will result in an anteroposterior displacement error of 0.2 mm at the second molar.

Lucia VO (1964) described the technique for recording centric relation with help of

anterior programming device.

Teteruck and Lundeen (1966) ,evaluated the accuracy of the earpiece face bow and concluded that only 33% of the conventional axis locations were within 6 mm of true hinge axis as compared to 56.4% located by ear face-bow. They also recommended the use of earpiece bow for its accuracy, speed of handling, and simplicity of orienting the maxillary cast.

Trapazazano, Lazzari (1967) concluded that, since multiple condylar hinge axis points were located, the high degree of infallibility attributed to hinge axis points may be seriously questioned.

Thorp, Smith, and Nicholis (1978), evaluated the use of face bow in complete denture occlusion. Their study revealed very small differences between a hinge axis face bow Hanau 132-sm face bow, and whip mix ear-bow.

Neol D.Wilkie (1979) analyzed and discussed five commonly used anterior points of reference for a face bow transfer. He said that not utilizing a third point of reference may result in an unnatural appearance in the final prosthesis and even damage to the supporting tissue. He suggests the use of the axis–oribitale plane because of the ease of making and locating orbitale and therefore the concept is easy to teach and understand.

REFERENCES• Boucher’S Prosthodontic Rx for edentulous patient 10th edition.• Essentials of complete Denture Prosthodontics by Sheldon

Winkler-2nd edition.• Fundamentals of fixed Prosthodontics by Shillingburg 3rd edition.• Evaluation, diagnosis, and treatment of occlusal Problems, Peter E

Dawson • Prosthodontic treatment for edentulous patients by Zarb

Bolender 12th edition.• Recording & Transferring the mandibular axis by Robert B.

Sloane J.P.D. 1952:173• Clinical evaluation of methods used in locating the mandibular

hinge axis by Mahmoud Khamics Abdel Razek J.P.D: 1981:369• Accuracy of predetermined transverse horizontal mandibular axis

point. William W.Nagy, Thomas J.Smithy,Carl G.Wirth J.P.d :2002:387

Thank you…..