Introduction• An accurate determination ,recording andtransfer of jaw relation records frompatients to the articulator is essentialfor the restoration of• function,• facial appearance• and maintenance of patients oral health.
Unsatisfactory maxillo mandibularrelationship will eventually lead to• failure of complete dentures andnecessitate• time consuming and costly repairs.
• Maxilla is a part of the cranium andis a fixed entity.• When the teeth of both jaws come incontact, maxilla becomes related tothe mandible so that entirecraniomaxillary complex is articulatedwith a moving bone, which is themandible.
• The upper jaw in the human skull ispositioned uniquely to the lower jaw. Thisposition is different for every person.• The relationship of the maxilla to thetemporomandibular joint is not the same inall persons i.e., the anatomy of maxillaand the temporomandibular joint variesfrom persons to persons.• This is the logic behind recordingorientation jaw relationship
• The opening movement to bring the jawfrom occlusal to rest position is almost apure hinge movement.• Here the mandible moves on an arc of acircle with a definite radius from thetemporomandibular joint. This path of thecondyle is determined by the curvature ofthe condylar head and the curvature ofglenoid fossa.
Since the radius is not constant for allthe patients, it has to be determined forevery individual patient, i.e., the relationof maxilla to the opening and closing axishas to be determined.
Orientation Jaw Relation• They are those that orient themandible to the cranium in such a waythat, when the mandible is kept in itsmost posterior unstrained position,the mandible can rotate in a sagittalplane around an imaginary transverseaxis passing through or near thecondyles. GPT -8• The axis can be located when themandible is in its most posteriorunstrained position by means of a
The relationship of the maxilla to thecranium in three planes viz:anteroposterior, lateral and vertical iscalled the orientation jaw relation.
According to BoucherThis is a relationship between thejaws and the axis of movement,not an anatomic relationship betweenjaws and TMJ,except to the extent that the axisof movement might happen to be nearTMJ.
Hinge axis• GPT defines hinge axis as animaginary line passing through thetwo mandibular condyles around whichthe mandible rotates withouttranslatory movement.• Gnathological society defines it asimaginary line connecting the center
Terminal hinge axis• When the condyles are in their mostsuperior position in the articular fossaand the mouth is purely rotated open, the axis around which movementoccurs is called as Terminal hingeaxis.
• Hinge axis is a horizontal axis aroundwhich the condyles rotate duringopening and closing movement up to arange of• Posselt (1952) 19-25 mm• Ulrich (1896) about 20mm• Campion (1905)10-20 mm• Fischer (1935)20mm and
• Pure rotation of condyles takes placein the first 10-13 degree arc ofmandibular opening and closing orduring the initial mouth opening of15-20 mm.• Later the condyles and disc translatesalong slopes of articular fossa. Thismovement is a combination of rotationand translation.
• Graphic records of mandibularmovements and radiographicinvestigations of the TMJ haverepeatedly shown that this assumptionis well founded, and that in normalsubjects and for small openingmovements the horizontal axis ofrotation does in fact pass through thecondyles.
• It is true that in wider openingmovements – the axis becomesprogressively displaced downwards.This is of anatomic interest ratherthan prosthetic interest.• In restorative and prosthetictreatment we are concerned withrelations between teeth only whenthey are in occlusion or at mostslightly separated.
Clinical Use Of Terminal HingeAxis• The location of the transverse hinge axisserves only to orientate the maxilla and torecord the static starting point forfunctional mandibular movements. It doesnot record centric relation or condylarmovements.• Allows the transfer of the opening axis ofjaws to the articulator so that occlusionwould be on the same arc of closure as in
• The hinge axis recording is requiredto check the accuracy of two centricrecords.• Helps in proper positioning of thecasts in relation to inter condylarshaft.• Vertical dimension of occlusion can bealtered on the articulator.
Like centric relation ,hinge axis is• Stable• Learnable• Recordable• Reproducible and• RepeatableTherefore it is used as an importantreference in mounting casts in thearticulator, so that the opening axis of thearticulator coincides with the terminal hingeaxis of the patient.
ControversyThere has been a considerable debateabout whether:• A hinge axis exists• Hinge axis can be accurately located• There is only one hinge axis• Is it clinically useful to locate theaxis• An arbitrary point can besatisfactorily substituted for akinematic axis
Study conducted by L. E.Kurth & I. K. Feinstein (1951)With the aid of an articulator &working model , they demonstrated thatmore than one point may serve as hingeaxis.They concluded that infinite number ofpoints exist which may serve as hingepoints. It is unlikely to locate thehinge axis accurately .
Study conducted by Robert GScholl Horn (1957)He recorded the arbitrary center & truehinge axis in 70 dental students.He concluded that arbitrary axis of rotationwhich is 13mm ant. to the posterior marginof the tragus on tragal canthus line liesclose to an average determined axis.In 95% of subjects Kinematic center lieswithin 5mm radius , which is considered tobe within normal limits.So determining kinematic center is notnecessary.
Study was conducted byRichard L Christiansen (1959)He mounted the maxillary casts arbitrarily& with face bow records & studied theerrors in occlusion.He concluded that it is advantageous tosimulate on the articulator the anatomicrelationships of residual ridges to thecondyles for more harmoniously occluding
Study conducted by T. DFoster in 1959He stated that permanent study castswould be of more value if they aremounted in correct relationship to theFH plane particularly in facialdeformity involving the jaws.
Study was conducted by ArneLauritzen & George H. Bodner in1961.They marked true hinge axis &arbitrary hinge axis by 3 methods.They concluded that in 67% ofcases the true hinge axis was 5 to 13mm away from the arbitrarily locatedhinge axis points.
Study was conducted by Vincent R.Trappazzan , Jhon B.Lazzari in1961.They conducted the study on 14subjects .They concluded that in 57.2% of thesubjects, more than one hinge axispoint was located on either one orboth sides.42.8% of the subjects showed singlehinge axis point on left & right side
Study was conducted by ArthurF. Aull in 1963.• He concluded that the horizontal axisis a hypothetical line.• Terminal hinge position is mostposterior position.• Arbitrary location fails to satisfy therequirements.• Do not support the split axis theory.• No evidence found to believe thatthere is more than one hinge location.
Study was conducted by Vincent R.Trapazzano & John B. Lazzari in1967.• They concluded that the patientshould be relaxed & two operators arerequired for location.• Because of the presence of multiplehinge axis points, increasing ordecreasing of the vertical dimensionon the articulator needs new interocclusal record.
Study was conducted by VirgilloFerrario, Chairello Sforza,Graziano Serrao & Johannes H.Schmitz in 2002• They assessed reliability of the face bowby comparing the values with thoseobtained by computerized non invasiveinstrument.• They concluded that face bow reliablyreproduced the spatial orientation of theocclusal plane relative to the true
Four main schools of thoughtregarding Hinge axis
Group 1Absolute location of hinge axisMcCollum(1939)There is a definite transverseaxis & should be located accurately.
Group 2Arbitrary location of hinge axis• Craddock & Simmons(1952)• Believe that arbitrary location of hingeaxis is reliable, even though accuratelocation is valuable.Craddock & Symons stated that – Thesearch for the axis is troublesome ,more of academic interest as it willnever be found more than fewmillimeters distant from the true centerof the condylar rotations .
Group 3Non believers in transverse hinge axislocation.• Beck(1959)• It is impossible to locate hinge axiswith accuracy.• More theoretical than practical.• Cannot be reproduced by anarticulator simulating one axistherefore, an arbitrary axis
Group 4 Split axis rotation• Slavens(1961)• Believe that the condyles rotateindependent of each other.This group believes there are two axisof rotation (one in each condyle) andthey parallel each other.JPD 9, 936, 1959
Face bowThe face bow is a caliper like devicethat is used to record the relationshipof the jaws to the temporomandibularjoints or the opening axis of the jawsand to orient the casts in the samerelationship to the opening axis of thearticulator.Boucher 11th edition
Face bow is a caliper like deviceused to record the relationship ofmaxilla to the temporomandibularjoint.Heartwell
Caliper like instrument used to recordthe spatial relationship of themaxillary arch to some anatomicreference point or points and thentransfer this relationship to anarticulator; it orients the dental castin the same relationship to theopening axis of the articulator.GPT-8
Bonwill, (1860) determined the distancefrom the center of each condyle to themedian incisal point and the lower teeth as10cm. He used this standard for mountinghis casts in the articulator.DisadvantageHe did not mention at what level below
• Balkwill (1866) demonstrated anapparatus with which he could measure theangle formed by the occlusal plane of theteeth and a plane passing through the linesextending from the condyles to the incisalline of the lower teeth. This angle variedfrom 22-30°.• He devised methods that wereimprovement on those proposed by
• Hayes (1880) introduced first exampleof functional face bow like deviceintended for locating the position of thecasts correctly in the articulator. Henamed the device as articulatingcaliper
• According to Prothero , Thomas L.Gilmer was the first to suggest theprinciple of a face bow in a paperpresented at a meeting of the IllinoisState Dental Society in 1882.
• Walker (1890) invented the clinometera new type of instrument used fordetermining position of the lower castin relation to the condylar mechanism,better than with all the previousapparatus.DisadvantageBulky exceedingly complicated
• In 1894 George K Bagby fabricateda device that determined the distancefrom the midline of the anteriorocclusal rims to one of the condyles.
Gysi (1895) constructed an instrument forregistering the condyle path.
• George B. Snow (1899)Invented a device which becameprototype for modern face bow.
Since the introduction of Snowsapparatus, no fundamental changeshave been made in the face bowdesign.Snow determined the position ofthe casts in the articulator notonly in regard to distance of themid incisal point from the condylesbut also the other points of theocclusal plane were given the
• The term, “face bow,” probably evolvedfrom a statement by A.D. Grit man, whodescribed the “implement devised byProf. Snow. . .as a bow of metal (that)reaches around the face. . .”• It first appeared in the literature in adescription for its use by Grit man andSnow in the American Textbook ofProsthetic Dentistry (edition 2),1900.
Dalbey (1914)Introduced the use of ear type offace bow but it was not until late60s the ear type did gainpopularity.
Uses of face bowFace bow record is used….• Balanced occlusion in CD• Class I & II cases– Open anterior bite or end to endrelationship– Single restoration on II molar not forpremolar and I molar– Segmental restoration– Anterior restoration – primary guidancefactor in excursive movement– Restoration of entire quadrant• Diagnostic purposes and Treatment planning
Articulators that do not offerpossibility to use facebows are morelike model holders
Parts of face bow• U-shaped frame• Condylar rods or earpiece.• Bite fork• Locking device• Third reference point.
U-shaped frameIt forms the main frame of the facebow.All other components are attached tothis frame.It extends from the region of TMJ onone side to the other side withoutcontacting the face.
Condylar RodsTwo small metallic rods on either sideof the free end of the U shapedframe that contact the skin over theTMJ.They are used to locate the hingeaxis and transfer it to thearticulator.Some face bows have ear piece thatfit into the external auditory meatus
Bite fork“U” shaped plate, which is attached to theocclusal rims, while recording the orientationrelation. It is attached to the frame with thehelp of a rod called the stem.
Locking device.This part of the face bow helps tofix the bite fork to the U-shapedframe firmly after recording theorientation jaw relation.
Third reference pointIt is used to orient the face bowassembly to a anatomical referencepoint on the face along with the twocondylar reference points. It varies inthe different face bows, exampleorbital pointer-orbitale, Nose piece –Nasion etc.
ClassificationFace bowArbitrary KinematicFascia type Ear piece typeWith orbital indicatorWith nasal relator
Arbitrary Face bow• The hinge axis is approximately located inthis type of face bow.• It is commonly used for complete dentureconstruction.• This type of face bows generally locatethe true Hinge axis within a range of 5mm.
• Uses arbitrary or approximate pointson the face as the posterior pointsand condylar rods are positioned onthese point.• As the located hinge axis isarbitrary, occlusal discrepanciesproduced in the dentures should becorrected by minor occlusaladjustments during insertion.
Fascia type• The fascia type of face bowutilizes approximate points onthe skin over thetemporomandibular region asthe posterior reference points.• These points are located bymeasuring from certainanatomical landmarks on theface.
DisadvantageAs the face bow is placed on theskin which is movable there is atendency for the condylar rods todisplace .Also requires an assistant to holdthe face bow in place.
Ear piece type• It uses the external auditory meatusas an arbitrary reference point whichis aligned with ear pieces similar tothose on a stethoscope.• Accurate relationship for mostdiagnostic and restorative procedures.
Advantage• Simple to use.• Do not require measurements on face• As accurate as other face bows.• It provides an average anatomicdimension between the externalauditory meatus and horizontal axis ofmandible
Disadvantage• Regardless of which arbitrary positionis chosen an error of 0.2 mm fromthe axis can be expected.• When coupled with the use of a thickinter occlusal record made at anincreased vertical dimension. Thisfactor can lead to considerableinaccuracy .
Spring bow (Hanau’s face bow)• It is an earpiece face bow made ofspring steel and simply springs openand close to various head widths.• Most commonly used face bow.• This instrument is designed to orientthe occlusal plane to the Frankforthorizontal plane by means for a thirdpoint of reference
Advantages :• The one piece design of boweliminates the moving parts andmaintenance problems encounteredwith other models.• Easy and efficient to use.• Sterilazable parts.• Direct/indirect mounting capability.Disadvantage :
Twirl bow• It is an earpiece type of face bow• Allows the maxillary arch to betransferred to the articulator withoutphysically attaching the face-bow tothe articulator• Relates the maxillary arch to FHplane
Slidematic face bow• Type of ear piece Face bow.• Used with Denar articulator.• It has an electronic device that givesreading denoting one half of the intercondylar distance.
Whip mix face bow• Ear piece type of face bow• It has a built in hinge axis locator.• Automatically locates the hinge axiswhen the ear pieces are placed in theexternal auditory meatus• Has a nasion relator assembly with aplastic nose piece
KINEMATIC FACE BOW:ACTUAL VALUE/ HINGE AXIS• It is used to determine and locate theexact hinge axis points.• Hinge axis of the mandible can bedetermined by a clutch i.e., asegmented impression tray like deviceattached onto the mandibular teethwith a suitable rigid material such asimpression plaster.
Indication :• When it is critical to preciselyreproduce the exact opening andclosing movement of the patient tothe articulator.Draw backs :• Extensive chair side.• Expensive• Rarely indicated for routinearticulators with prosthodonticprocedures.
The Plane of orientation• The maxillary cast in the articulator isthe baseline from which all occlusalrelationships start.• Therefore it should be positioned inspace by identifying three points• Two points are located posterior to themaxillae and one point located anteriorto it.• The posterior points are referred to asthe posterior points of reference andthe anterior one is known as the anterior
The spatial plane formed byjoining the anterior and posteriorreference points is called plane oforientation.
Prior to aligning the face bow onthe face, the posterior referencepoints and the anterior referencepoint must be located and marked.
Posterior reference pointsThe position of the terminal hingeaxis on either side of the face isgenerally taken as the posteriorreference points.
Beyron point13mm anterior to the posteriormargin of the tragus of the ear on aline from the center of tragusextending to the corner of the eye.
Bergstrom point:10mm anterior to the center of thespherical insert for the externalauditory meatus and 7mm below theFrankfort horizontal plane.
Bergstrom point is found to bemost frequently closest to thehinge axis.Beyron point is the next mostaccurate posterior point ofreference.
Gysi point• 13mm in front of the most upper partof the external auditory meatus on aline passing to the outer canthus ofthe eye.• This method was proposed by Gysi,Hanau, Snow and Gilmer and is themost common point used today.
Other posterior referencepoints• 13 mm in front of anterior margin ofmeatus : 40 % accuracy• 13 mm from foot of tragus to canthuswith 33% accuracy• Ear axis 75.5% accurate
Why Anterior Point ofReference?• Anterior point of the triangular spatialplane determines which plane in the headwill become the plane of reference whenthe prosthesis is being fabricated.• When three points are used the positioncan be repeated• To visualize the anterior teeth and theirocclusion in the articulator in same frameof reference that would be used when
Orbitale• In the skull, orbitale is the lowestpoint of the infra orbital rim.• On a patient it can be palpatedthrough the overlying tissue and theskin.• One orbitale and the two posteriorpoints that determine the horizontalaxis of rotation will define the axisorbital plane.
Advantage• It is easy to locate and mark .• The concept is easy to teach andunderstand.Disadvantage• Relating the maxillae to the axis orbitalplane will slightly lower the maxillary castanteriorly from the position that wouldbe established if the Frankfort horizontalplane were used.
Nasion minus 23mm• Deepest part of the midline depressionjust below the level of the eyebrows.SICHER• The nasion guide, or positioner, of theface bow fits into this depression,designed to be used with whip mixarticulator• This guide can be moved in and out, butnot up and down, from its attachment.
• The cross bar (u-shaped frame) islocated 23mm below the midpoint ofnasion pointer.• When the face bow is positionedanteriorly by the nasion guide, the crossbar will be in the approximate region oforbitale.• The face bow cross bar and not thenasion guide is the actual anteriorreference point locator
Ala of the nose• The right or left ala is marked onthe patient and the anteriorreference pointer of the face-bow is set.• This method uses the CampersPlane as the plane of orientation
Orbitale minus 7mmThis plane represents FrankfortHorizontal plane
43 mm superior from lowerborder of upper lip• This plane represents Denar referenceplane• Denar face bow uses this referencepoint
Face bow transfer• Face bows that can be utilized with HanauarticulatorFasciaEar pieceTwirl bowSpring bowKinematic• Face bows that can be utilized with Whip mixarticulatorQuick mount ear pieceKinematic• Face bows that can be utilized with DenararticulatorFasciaEar piece
Thumbscrews tightened tomaintain the spatialrelationships between face bowand bite fork
Face bow assembly along withbite fork is removed from themouth and positioned in thearticulator
How to take a face bow recordusing arbitrary face bow5 min Video
KINEMATIC METHOD OFLOCATING HINGE AXISFabrication of the clutch.Attach clutch tray to lower teeth.Assemble the hinge axis locator.Attach the side arms to the cross bar inmounting column.Attach the assembled hinge axis locator to theStem of the clutch tray.Mark approximate center of condyle on thesubject`s face.Adjust the hinge axis locator.Place the graph paper .Location of the hinge axis points.
OTHER METHODS OF RECORDINGHINGE AXIS• Pantograph– two face bows, one holdssix recording tables attached to themandible & other with 6 stylusesattached to the maxillae.• Transograph.• Stereograph• Computerized Axiograph
Conclusion• Failure to use the face bow leads to errorin occlusion.• Hinge axis is a component of everymasticatory movement of the mandible andtherefore cannot be disregarded and thishinge axis should be accurately capturedand transferred to the articulator. So itbecomes a fine representative of thepatient and biologically acceptablerestoration is possible.• Whatever may be controversy reasoned byin the use of face bow but it should form
References• Boucher’S Prosthodontic Rx for edentulouspatient 9th edition.• Syllabus of complete dentures by Charles M.Heartwell 4th edition 5th edition.• Essentials of complete DentureProsthodontics by Sheldon Winkler-2ndedition.• Fundamentals of fixed Prosthodontics bySchillingburg 3rd edition.• Management of TemporomandibularDisorders & Occlusion 5th edition. Jeffrey.P.Okeson.• Evaluation, diagnosis, and treatment ofocclusal Problems, Peter E Dawson• Prosthodontic Rx for edentulous patients byZarb Bolender 12th edition.• Hobo|Eiji Ichida |Lily .T .Garcia-
The hinge axis of the mandible Kurth & Feinstein J.P.D:1951:327Recording & Transferring the mandibular axis byRobert B. Sloane J.P.D. 1952:173.Evaluation of face bow by Craddock & SymmonsJ.P.D:1952:633.The face bow,it’s Significance & Application by ThureBrandrup-Wognsen J.P.D.:1953:618.A study of the arbitrary center &the kinematic center ofrotation for face bow mounting by R.G. SchallhornJ.P.D:1957.Hinge axis registration on articulators Borgh & PosseltJ.P.D 1958Rationale of face bow is maxillary east mounting byRichard L. Christiansen J.P.D:1959:388.A clinical evaluation of the Arcon concept of articulatorHeinz O.Beck J.P.D 1959The use of face bow is making permanent study casts byT.D.Foster J.D.P : 1959 :717Hinge axis location on an experimental basis Lauritzen &
The anterior point of reference by Noel.D.Wilkie J.D.P1979:41:5:488A study of transverse axis Arthur F. Aull J.P.D;1963:469The physiology of the terminal rotational position of the condyles inthe TMJ J.P.D: 1967:122The need to use an arbitrary face bow when remounting completedentures with Intercellular records by Keki.R.Kotwal in J.D.P.1979:224Discrepancies between arbitrary & true hinge axis by F.M. Walker aJ.D.P:1980:43:279.Studies on validity of terminal hinge axis C.C.Beard, J.A.ClaytonJ.P.D: 1981:185Clinical evaluation of methods used in locating the mandibular hingeaxis by Mahmoud Khamics Abdel Razek J.P.D: 1981:369The hinge axis evaluation of current arbitrary determinationmethods & proposal for new recording method J.P.D :1989Re-evaluation of axis-orbital plane & the use of orbitale in a facebow transfer record by Jhon H.Pitchford J.P.D.:1991:66:347.Three dimensional assessment of the reliability of a postural facebow transfer by Virgillo Ferrario,Chairello Sforza,GrazianoSerrao,& Johannes H. schmitz J.P.D.2002:87:210.