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FACE BOW HISTORY : If

we wish to know something about face bow,

how

this

instrument is used and the significance of its application a short historical survey of the ideas connected with these problems, and the working 'methods and instruments that they have given rise to, will give us clear picture of the features to be remembered in this aspect. About mid 18th century it began to be realised that in fabrications of complete dentures it was important to mount the casts inthe articulator in a given positional relation to the

condylar elements.

According to

Bonwill, 1860 the distance from he center of each condyle to the median incisal point of the lower teeth is 10 cm and he advocated this measurement to be followed while mounting but he did not mention however at what level (vertically) the occlusal plane be paced in relation to condyal mechanism. It appears that he advised the casts to be mounted midway between the upper and lower parts of the articulator. In 1866 an English dentist by name Balkwill devised methods that were improvement on those proposed by Bonwill. Balkwill demonstrated on apparatus with which he could measure the angle formed by occlusal plane and the line joining condylar

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centers to the incisal point of the lower teeth and the angle varied from, 22째 to 30째. An other method for localizing the casts in the articulator was constructed by Hayes in 1880 and the apparatus was called caliper. However again there was no proper orientation possible. Then

in 1890 walker invented Clinometer with which

possible to obtain a good position of the cast in articulator. mainly this instrument

as

instrument

it was

He used

for condylar inclination

measurement device. A little later Gysi about the turn of the century developed an instrument similar to a facebow primarily to record position of the condyles however, it could be used to mount casts. But the credit goes to Snow for inventing a Actual Facebow on which most of the present day facebows are based. Snow introduced the facebow in 1899 and patented it in 1907. In 1914 Dalbey introduced the use of ear type of facebow but it was not until late 60's the ear type did gain popularity. We are justified in staling that snow's facebow inspite of its very simple construction was Epoch making in prosthetic dentistry. Since the introduction of Snow's apparatus, no fundamental

changes have been

made in the face bow design. Because snow determined the position of the casts in the articulator not only in regard to distance of the mid incisal 2


point from the condyles but also the other points of the occlusal plane were given the correct relationship in relation to condyles. PRINCIPLE OF FACE BOW USE : The movements of the teeth are results of the rotation and slidings made by the condyles. The better the casts on the articulator duplicate the distances to the rotational condylar centres, the less the potential errors produced by difference in the arcs of closure of the mandible and the articulator. The use of facebow is an integral part in procedures in analyzing and studying occlusion, developing the occlusion for complete dentures and other restoration. The occlusal plane is related by making it parallel to a horizontal plane so that it easier to relate it the articulator. Snow recommended that the occlusal plane be made parallel with a plane extending from the bottom of the glenoid fossa and passing through the anterior nasal spine.

This plane cannot be determined

directly on a living persons but it approximately, corresponds With a line drawn from the upper parts the Tragus to the lower edge of the Nostil or Alatragal line. This plane in European literature is referred as camper's plane, in Americal literature it is referred so as Bromell's plane. Gysi and kohler used a plane called as prosthetic plane which extends fro, the 3


lower part of the tragus to the Ala of the nose. Wads-worth employed a different plane which from the condyle area and runs at right angles to a line that connects the most prominent points of the chin and forehead. Over recent years, there has been a growing tendency to employ a plane (i.e.) the Frankfort horizontal plane which is usually parallel to the floor when an individual is in a upright position. Cephaornetrically the Frankfort's plane is described a horizontal plane that passes through the right and left portion (the mid point on the upper margin of external auditory meatas) and the orbitale (the lowest point on interorbital rim). The Horizontal plane forms a plane which is called as the AxisORBITAL plane. This plane formed by the two posterior points of reference and the one anterior point of reference which is usually the infraorbital notch indicated by the pointer fixed on the face 'bow and the posterior points of reference are those where the condylar rods are placed thus when utilizing the two posterior (points) and anterior points the occlusal plane is related to the face bow and through the face bow franfered on to the articulator. In the articulator there is a condylar plane estab lished by the condylar spheres and a indicator for the anterior point of reference the condular rods approximating the condyles through it the hinge axis are attached to the centre at the condylar spheres of the articulator.

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Principle face bow use : The prosthesis or indirect restorations that

are planned and

fabricated with help of articulators should have the same relationship as they have with articulator’s axis of opening as well as the patients mandibular arc of movement. Since

it is practically difficult to orient the

mandible to the

articulator, the maxillary cast is related to the articulator with same relationship with the condyles of

TMJ

existing which

relationship

between maxillary

and

is center of mandibular movements, the

mandibular cast is related to maxillary cast which in turn is oriented in the articulator. To accomplish this act of orientation the device face bow is utilized. Before we (study) know more about the facebow and its use a brief description about the terminal hinge Axis will help us in better understanding of the face bow. The terminal hinge axis is an imaginary axis around which the condyle can rotate without translation and this axis is assumed from which all the mandibular movements of opening and closing take place. The THA is the most retruded hinge position and is significant because it learnable, repeatable and recordable that coincides with the centric

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relation. The limits of the hinge movement in this position is about 12째15째 at condyles or 19-21 mm in the incisal region. The condyles are in a definite position in the fossa during the rotation. Snow recognised the importance of this axis and to transfer this axis to the articulator led to development of facebow and in 1921 McCollum, Stuart and others reported the first method of transferring this axis. Since then many have put forward views that are very diverse from each other. Sloane stated "The mandibular axis is not a theoretical assumption but difinitely demonstrable biomechanical fact. It is the axis which on the mandible rotates in an opening and closing function when comfortably but not forcibly retruded." "The hinge position or terminal hinge position is that position of mandible from which or in which hinge movements of a variable wide range is possible. But contrary to them Brekke, Trapozzano and Lazzari and Lucia questioned existence of the single hinge like axis of rotation for mandible since the ideal mechanical set up is never found in living tissues. Controversy arises as to the presence of single relationship of TH position to entire portion.

There are differences in concepts and 6


interpretations of the findings.

These differences in findings are

understandable and these seems to be general agreement that when the mandible is in centric relation the mandible is in its most posterior unstrained position from which a trained individual can voluntarily open and close the mandible in hinge movement. Since it is a repeatable and recordable position it is a point of return. Therefore we strive to capture this imaginary axis and transfer this to the articulator and depending upon how accurately the face bow capture and transfer this to articulator led to the coining of words like Kinematic face bow and Arbitrary face bows. The occlusal plane or the wax rim is related to the TMJ by using a horizontal plane and this relationship is transferred to the articulator using a facebow register the GLENO MAXILLARY. Relationship in three plane of: o Anterio-posterior sagital plane o Transvers or frontal o Vertically The maxilla is related to a horizontal plane usually formed by 3 points of references. Two posterior points of reference One anterior point of reference

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If the inaxillary cast is positioned without the correct maxilla hinge axis relationship arcs of movement in the articulator will occur which are different from those of patient. Occlusion that is restored to an incorrect arc of closure will have interceptive and deflective tooth contacts. Such contacts are undersirable and contribute to: o Periodontal problem o Muscle spasm o TMJ pain o Loss of supporting bone Location of hinge axis was discussed by Campion first time told that axis of opening should coincide with the articulator axis. Theoretically unless the extra THA is located and transferred the inter occlusal space used for recording in jaw relations will induce errors in casts mounted on articulators. The error produced may not have serious consequence in removable prosthesis with non-rigid attachments in such conditions the intended tolerances and mobility of the supporting tissues make the precise location of THA a

exercise with

no great

advantages. On the other hand fixed and removable prosthesis of rigid attachments demand close tolerances in cusp path ways. 8


Facebow Transfer: Use of kinematic face bow : The technique for locating the axis for dentulous and edentulous patients is same except for the mode of attachment of the clutch to the mandible. The clutch directly cemented on the teeth and in case of edentulous condition clutch is attached to mandibular wax rim and the

chin clamp is used to stabilize the

mandibular denture base because of the instability and soft tissue mobility, inaccuracy creep in which defeat the purpose of axis location. The patient is trained to make a limited opening and closing movements of about 1920mm in insial region within the rotational movement of the condyles. These points are directly marked on the skin or flag or grid with graph paper placed on it and this distance is measured from the tragus and is used as the posterior reference point and the facebow transfer is done in usual means. In case of Arbitrary type facebow the posterior points are selected on a anatomical average of l3mm anterior to the tragus on a line from tragus to the outer cantus of the eye and the fork is attached to the maxillary teeth or wax rim. The fork is either inserted in the rim or a index is used. The condylars (elements) rods are adjusted till the fork is centered and the pointer for third point of reference of orbital pointer or the nasion relator is adjusted and once all the locknuts or secured the

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facebow should

support

condylar lock nuts

by itself

without any movement than the

are released and the face bow transferred to the

articulator with the condylar rods approximating the condylar spheres of the articulator and the pointer pointing to the built in orbital indicator and the cast is placed in the record base and mounted. Thus the plane of occlusion when viewed on the articulator will be similar to that of the patient in an upright position and the occlusion plane is placed in a similar, relation in the articulator as that exists in the patient's mouth. Description of Facebow : The facebow consists of 'U' shaped frame or assembly i.e. large enough to extend from the region of the TMJ to a position 2-3 inches in front of the face and wide enough to avoid contact with sides of the face. In the condular region there are condylar rods with graduation extending from the main assembly which are placed over the posterior reference points, the reading the condylar rods help us to center the facebow.

Once the

facebow is adjusted there are locknuts that are tightened. The part of the assembly that is attached to wax rim is called bite plane or fork through the stem or yolk. The fork is attached to the main frame and there are pointer for the third point of reference like orbital pointer or nasion relator.

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The facebow or hinge bow for kinematic is also construction except that instead of the fork attached

similar in

to maxilla it is

attached to the mandible and there are attachments where the flages or grids with graph paper are attached to frame which either attached to the maxi, teeth or held by head straps or worn as spectacles. The clutch or the fork on the mandible in case of edentulous patiet is stabilized using a chin clamp. The arbitrary axis of rotation as set forth by Snow, Gilmer, Hanau, Gysi and others of 13mm anterior to the tragus on the tragus-canthus line very close to an average determined axis. The procedures locating hinge axis calls for rather lengthy and difficult procedure, which require use of a large and bulky apparatus, which pose problems of attaching the apparatus to the mobile mandible securely and this problem is more compounded in edentulous jaws where the soft tissues and mandibular denture bases are unstable. This lead Craddok and Symmons in 1952 to state that "search for the axis in addition to being trounlesome is of no more that academic interest for it will never be found to lie more than few milimeters distant from the assumed

center of

the condule itself.

palpation 10-13mm anterior to tragus.

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This can be done


The T.H.A. is not only difficult to locate but also difficult to relocate the same point of axis.

Kenneth and Fein-Stein attempted to

locate the axis and were successful only in relocating it within a radius of 2mm. Borjh and Posselt could relocate it within 1.5mm. USE OF F.B. AND RELATION TO THE ARTICULATORS REFERENCE POINTS One recommended method of positioning, the maxillary cast vertically in Hanan articulator is to relate the maxillary cast with the F.B. still attached to the articulator till the maxillary central incisors .edges or the maxwax rim are aligned to the level of Incisal Reference Notch. 30mm below the Horizontal condylar plane described by the centers of the condyles and the infra-orbital indicator, unfortunately there is no Anatomic relationship between the anterior reference point of orbital and I. R. Notch in other words the 30mm is not the correct distance between orbitals and maxi incisal edges.

There are other incisal reference notches placed 37, 54

and 47mm below the condylae place. But according to Gonzalers and kingery the centre of the condyle is 7mm below the porion which forms the frankforth horizontal plane and therefore the axis-orbital plane should be placed

7mm below

to set a proper parallelism and therefore

infraorbital foramina should be used as anterior points of reference.

12

the


POSTERIOR POINTS OF REFERENCE Often the posterior points are located by measuring prescribed distances from skin surface landmarks.

Some of the commonly used

posterior points were shown by beck to be clinically near the hinge axis. He concluded that pergstorm point followed by beyron point were most frequently close to hinge axis. It is known that balanced occlusion is necessary for the stability of the dentures and for the health of the oral tissues. An accurate place of orientation does appear to be essential step in C.D. fabrication. An error of this size may not have serious removable

prosthesis with non

rigid

consequence in

(connectory) attachments, in

such conditions the intended tolerances and mobility of the supporting tissues make the precise location of the Hinge axis a en... with no great advantage on the other hand fixed and removable prosthesis with rigid attachment demand close tolerances in cusp path ways. Verifications of the mandibular cast portioning by use of inter occlusal records made at increased vertical dimensions of occlusion will be difficult if not impossible when the interocclusal records are made at same thickness. Changes in vertical dimensions of occlusion. Bergstorm point : 10mm anterior to the centre of spherical insert for the auditory meantus and 7mm below the 13

Frankforth H. plane.


Beyron point 13mm anterior to the posterior margin of the tragus of the ear on a line from the centre of the margins to the corner of the eye. The selection of the (anterior) points of reference is useful so that different maxillary casts of the same patient can be positioned in the articulator in the same relative position. The points give the procedure the value

of

constant

determination

and also reduce time

with

complicated time consuming recording techniques such as pantographic tracings to repeat the records each time the technique calls for a new casts. For this reason it is important to identify the mark permanently or be able to repeatively measure a anterior reference, point as well as the posterior points of reference. Selection of Anterior Point of Reference 1.

Obritale

:

In the skull orbitate is the lowest point on the

infraorbital rim. On a patient it can be palpated through overlying skin and orbitate and the the posterior points that determine the horizontal axis is defined as the axis - orbital plane. Practically the axis orbitory plane is used because of the ease of locating and points easy to understand. This plane can be transferred to articulator with the help of the orbital pointer and indicator on the articulator.

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2.

Orbitale minus 7Tnm : The frankfort ' s horizontal plane passes through the poria and one orbitale because these points are (skull) bony landmarks.

Sicher recommends

using the mid point of the

external auditory meatus as the posterior cranial landmark.

Most

articulators do not have reference point for these posterior land marks lies 7mm superior to the axis and recommends composition by making anterior point of reference 7mm below the orbitale or positioning the orbitale pointer 7mm above in the articulator to the orbitale indicator. 3.

Nasion minus 23mm : Again according to Sicher another skull landmark the Nasion can be used as the anterior reference point. The nasian guide or positioner which relates to the deepest part of the midline depression just below the level of eyebrows, as used in whipmix and SAM quick mount face bow is designed so that it moves in and out but not up and down from its attachments to the cross bar. The cross bar is located approximately 23mm below the nasion. When the face bow is positioned the cross bar will at the level of the orbitale. The disadvantages of using this kind of face is that this technique depends upon the large nasion guide the morphologic characteristics of

the Nasion

notch

and

the variance of the Nasion orbitale

measurements from 23mm in the patient. 4.

Incisal edge plus anterior midpoint to articulator axis

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Horizontal plane distance. Guichet - Emphasized that a logical position of casts in the articulator would be one which would position the plane of occlusion near the mid horizontal plane or articulator.

The the mid horizontal distance to the

axis condyler plane is measured, this measured distance measured onto the patients from the existing incisal edges or planned occlusal plane and then transfer is done. 5.

Alae of the Nose :

The occlusal plane actually parallels the

horizontal plane which was concluded by Angsbreber in review of literature that the occlusal plane parallels the campu's line with minor variations knowing this we can transfer camper plane from the patient to the articulator by using either right or Ala as the anterior reference point. Importance of selection of anterior reference point 1.

A planned choice of anterior reference point will allow the dentist and auxiliaries to visualize and anterior

teeth and

occlusion in the articulator in the same frame of reference that would in patient i.e. as if patient standing in normal postural position with eyes looking straight ahead. 2.

The act of affixing a maxillary cast with its determined hinge axis

to an articulator with its 16

axis

in

the condyler


determinants achieves greater importance by the use of the three points of easy reference where are constant

and

repeatable. To use or not use : The value of the face bow has been the topic of considerable discussion and contraversy in prosthesis dentistry for many years. Logan considered indispensable Craddock and Symmons considered it as futile exercise. While Stansberry described a technique of positioned records and told that use of face bow was useless. Lazzari set forth the advantages of using a facebow. 1. It permits a more accurate use of lateral rotational points for arrangement of teeth. 2. It aids in securing anterioposterior positioning of the cast in relation to the condyles. 3. A

correct horizontal plane is established.

Therefore the

incisor plane is also properly established. 4. It helps in vertical positioning of the cast in articulators. •

Face bow transfer is not required in following conditions.

The articulators developed not to receive face bow transfer.

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Some

theories

of occlusion specially

the

Monson's

When monoplane teeth are arranged in a

occlusal

spherical theory of occlusion. • balance. •

No

alteration of occluding surfaces of the teeth

that

necessitates the changes in verticle dimension. •

No inter occlusion check reports that would be of different thickness. But when we analyse the above said facts it is very clear that by

simply stating that the articulator is not designed to accept the face bow, we cannot forget the step of facebow transfer and incorporate the errors due to blind orientation of the casts on the articulator and we cannot have single predetermined scheme of occlusal for all patients and we cannot use mono plane teeth for all cases in fact when we are cusped form of teeth facebow transfer becomes a must to achieve balance in entire positions. Changes do occur in vertical dimensions in complete dentures due to processing and dimension if to be retorations requires a facebow transfer and in case any remound is desired any change is there in occlusal records needs a facebow transfer. Vertical

dimension desired and planned on

articulator require

facebow transfer. When use the following figures it becomes very clear 18


that now varied the

cuspal

inclination when the casts are placed at

different levels in articulators of course the changes may not be so great in positions but changes do occur. Average mountings do not serve the diagnostic

imposes in

distrubances that occur to positions teeth face transfer in not only useful from prosthesis recontractive view that also diagnostic (tool in) procedure in gnathological studies. The overall opinion to which majority of the prosthodontics agree in put forward by the academy of denture prosthodontics favouring the use facebow and concluded that "A FACEBOW SHOULD BE USED FOR MOUNTING THE UPPER CAST ON ANY ARTICULATOR THAT HAS A FIXED AXIS OF OPENING". The correct orientation of the occlusal plane is a important step and the inclination of the plane that we develop had effect on the masticatory performance. Kapoor and Soman showed that the masticatory performance was influenced by the plane of orientation and Hideaki, Okene and others who further carried out the research found that maximum clenching force was greatest when the occlusal plane parallel to the camper's plane and the force decreased when there was 5째 tilt either anterior and posterior. Modification of face bows and different types of face bows : 1.

Accuracy

- Kinematic - Arbitrary

- Eartype

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- Fascia Eartype

- Manual lenthing eg. HANAO - Self centering or quick mount eg. whip-mix, Bregstorm, SAM

Even though the Snow type FBS are mechanically simple they are in convient to assembly on patient - to locate - to adjust the FB. On the posterior points of reference directly on the skin. Therefore in 1914 Dalbeg introduced the use of ear type of facebow where the posterior ends were modified and may fit in the car but it was not until late 60's the ear type gained populatiry. Now there are so many articulatory available that each articulator had to use with special type of FB. Then Kelseg came out with adapter which permits one type of face bow to be used 'with different articulatory. Then there came the self centering type or quick mount type of the F.B. With a built in gear mechanism where only one mechanism help to center the fork. - Slidematic facebow - Quick mount or whipmix

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Bregstorm

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Springbow : Further simplication of the arbitory lead to development of spring bow which eliminate the wrencnes and screws and moving parts. It is one piece low maintenance and lower cost. Modifications : Disadvantages of conventional face bow fork : 1.

Heatedfork when inserted into the wax rims distorts the carefully developed contours.

2.

The width is fixed and sometimes difficult to be used with larger or smaller arches.

3.

When the face bow transfer is to done after the centric occlusion interocclusion record, the possibility of the rim distortion is introduced.

4.

In treating the patients

(for)

immediate

maxillary denture the face bow transfer may be complicate by remaining natural teeth. Advantages of modified facebow fork : 1. Does not distort facial contours the wax rim. 2. Provides adjustability and can be used with any size ofarch.

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3. Minimum or no distortion when facebow transfer is made after inter occlusal registration. 4. Can be used for immediate denture treatment with the natural teeth. It is attached to the palatal portions of the (denture) record base. A new face bow design was introduced that further simplifies the arbitory face bow technique. Advantages include 1. Ease and efficiency of use 2. Steriligable parts 3. One piece low maintenance design 4. Adaptability to many articulators 5. Lower cost than other car piece types Made up of spring steel and simply springs open and closes to various head width. CONCLUSION Failure to use the facebow 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

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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 facebow but it should form a integral part of one prosthodontic treatment.

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