The hinge axis is an imaginary line around which the mandible rotates in the sagittal plane. There are various theories on the location and nature of the hinge axis. Methods to locate it include arbitrary, kinematic, and modified techniques. Locating the hinge axis clinically is important for correctly recording centric relation and transferring jaw movements to an articulator. However, there are many patient and recording system variables that can affect the accuracy of hinge axis location.

1. Hinge axis

2. Contents
1) Introduction
2) Definitions
3) Mandibular movements
4) History
5) Theories of hinge axis
6) Method of locating hinge axis
7) Clinical value of hinge axis
8) Summary
9) Reference

3. Definition
• “Imaginary line between mandibular condyles around which the mandible
can rotate within the sagittal plane” GPT—8
Terminal hinge axis = Transverse axis = Transverse horizontal axis = Transverse
hinge axis
• Pure rotation of condyles prior to translation

6. Mandibular Movements

7. • Rotation - the movement of a rigid body in which the parts move in circular paths
with their centers on a fixed line called the axis of rotation.
• Translation - that motion of a rigid body in which a straight line passing through any
two points always remains parallel to its initial position.
• Hinge axis point = posterior reference points - two points, located one on each side
of the face in the area of the transverse horizontal axis, which together with an
anterior reference point, establish the horizontal reference plane.

8. Rotational movement can occur in all the three reference planes:
Frontal
Horizontal
Sagittal
• In each plane occurs around a point called the axis

9. Frontal (Vertical) Axis of Rotation

10. Horizontal axis of rotation

11. Sagittal Axis of Rotation

12. Sagittal view Frontal view
Horizontal view
Posselt`s border movements

13. Posselt’s Figure
MP
MO
ICP
RCP
HA
MP = Maximal protrusion
ICP = Intercuspal position
RCP= Retruded Contact position
HA = Hinge axis
MO = Maximum opening

14. History
• Campion ( 1902-1905 ) – No axis, but movement is complex one.
Consisting first of rotation and secondly of a forward and downward movement
• Bennett ( 1908 ) - no single fixed rotation, since center of rotation constantly shifted for
movements in sagittal plane,
mandible was capable of two independent movements
1. Angular rotation
2. Translation movement

15. • Gysi ( 1920 ) – Natural condyles are not considered as true rotation points, but
as fixed guides of the mandible
"The mandible opens/closes and rotates on another
rotational center which has no influence in the setting up of the teeth on
articulators. Therefore, need not be considered in the construction of an
articulator.”
• Needles ( 1923 ) - agrees with Bennett: Hinge Joint + Sliding Joint.
No center of rotation in temporomandibular joint itself.
Instant and constantly shifting centers

16. • Wadsworth (1925) –
Anatomist's conclusion
1st movement around transverse axis passing through condyles which remain
seated in fossae.
2nd movement on articular eminence
• Hall ( 1929 ) – concluded that “condyle is not center of rotation”
`

17. McCollum ( 1939 )
• Leading advocate of the hinge-axis theory
• Definite opening and closing axis by using facebow
• External landmarks are of little use.
• Rotation occurs during 0.5 inch at incisors for most people, some can
open 1 inch.

18. Stuart ( 1939 )
• Completed work of McCollum
• Pioneers of gnathology
• Movements were reproduced on articulator to duplicate the jaw movements
McLean ( 1944 )
" The diagnosis of pathological occlusion depended on the fact that the final
phase of jaw closure was pure hinge movement.“

19. Lauritzen ( 1951 )
• He thought articulation would be understood more easily if the joint
were regarded as two separate joints
• The only movement which could take place in the 'menisco-condylar'
part of the joint while opening and closing - a purely rotational
movement.
• In all patients, the anterior teeth could be separated by at least 12
mm in the rotational hinge relation.

20. Posselt (1952)
• Hinge opening is obtained if patient is in passive, or trained active motion.
• He could not prove this movement was habitual.
• Hinge-axis opening = 19.2mm 1.9mm.
Kornfield & Granger ( 1955 )
• The only position at which it was possible to locate & reproduce the hinge axis
was at centric relation

21. Trapozzano ( 1955 )
• Hinge-axis represented a border movement that could be recorded
repeatedly with unfailing accuracy

22. • It was essential to use trained
mandibular hinge movement
• Recording was static starting point
• Much of concept was based on
asymmetry of condyles
• Off-Centre opening and closing
movements were perpendicular to
hinge axis
• Movement in one direction in the plane
could have only one axis of rotation
Weinberg
( 1959 )

23. Theories Of Hinge axis

24. The absolute
location of
hinge axis
school
The
arbitrary
axis school
The non-
believers
The split
hinge axis
school
Aull ( 1963 )
Four
schools of
thought

25. •The hinge axis is a component of every masticatory movement and can not
be disregarded.
•If the hinge axis of the articulator is not the same as the hinge axis of the
patient then the mechanical reproduction of jaw motions are impossible.
•Believe that there is a definitive transvers axis and should be located
Absolute location of the axis

26. •The value of actually locating the exact hinge axis is not
worth the effort. This group fails to recognize that if the
hinge axis of the articulator does not coincide with the
hinge axis of the patient, the paths of closure will not be the
same.
Arbitrary location of axis

27. • This group does not believe the hinge axis can be accurately
located or believes other movements are involved and can not be
reproduced by an articulator simulating one axis
Non-Believers in the transverse axis location

28. • This group believes there are two axis of rotation ( one in each condyle) and they parallel
each other.
1. The horizontal axis is a hypothetical line connecting the two horizontal rotation centers of
the two condyles of the mandible.
2. There is one hinge location!
Split axis theory

29. METHOODS OF LOCATING HINGE AXIS

30. Arbitrary methods
Kinematic methods
Modified methods
1. loma-linda hinge axis device and method
2. Buhnergraph intraoral method
3. Technique using geometric principle to locate hinge axis
4. Abdal-Hadi’s method for locating arbitrary hinge axis

31. • Beryon point: 13mm anterior to posterior border of
center of tragus on a line joining outer canthus of eye
• Bergstrom point : 10mm anterior to center of spherical
insert for external auditory meatus and 7mm below FH
plane
• Gysi point: This was on a line from the upper margin of
the external auditory meatus to the outer canthus of
the eye, 13 mm in front of the anterior margin of the
meatus
• Commonly used today
Arbitrary Method

32. Dejoyuex point : 10-11 mm anterior to ear on line to canthus and 5mm
below it
Dawson palpatory method
Lauritzen boundner axis: 12mm anteroir and 2mm below portion of
FH plane

33. Two theorems of geometry are used in this technique
• 1. A line drawn through the center of a circle perpendicular to chord
meets it at its midpoint
• 2. The line joining the center of a circle to the mid point of a chord is
perpendicular to the chord.
Kinematic methods

34. Instruments
• Buhnerberg instrument
• Pantograph
• Transograph
• Electronic mathematical method
• Stereognathography
• Axitron-computerised axiograph
• Digital recording system

35. Step wise method of recording
1. Recording hinge axis points
2. Transfer to the articulator
3. Mounting of upper casts and
4. Mounting of lower casts with centric record

36. • T.M.J instrument
• Hinge axis locator
Hinge axis bow

37. • Attach the clutch to lower teeth
• The clutch is a device, which relates the face-bow
to the mandibular residual alveolar ridge. It is
nothing but an occlusal rim made of impression
compound with a bite fork attached to it
• the clutch resembles a cap splint with a bite fork
attached to it. It is usually fabricated and cast in
aluminum.
Axis location

40. Attach cross bar to clutch and side arms with stylus to cross
bar
Guide mandible to terminal hinge closure
Observe the movements of stylus. When stylus rotates
without arching movements indicates hinge axis point
At terminal hinge closure stylus should make contact on
skin to transfer ink mark.
The two marks are hinge axis points

44. Low fusing
compound to
bite fork of
facebow
Slight
indentations
of maxillary
teeth is
obtained
Now position
styli on either
sides on
posterior
reference
points
Position
orbital
reference
point
Lock face
bow and
remove it to
clamp it on
transfer
board
Axis jig is
placed and
adjusted to
support the
styli
Axis transfer

45. Loma-linda hinge axis recording device and method
• The opponents of use of a kinematic hinge-axis location for
edentulous patients point to its unreliability because of the resiliency
of the oral mucosa.
• the added weight of the recording clutch which tends to shift the
denture base
Modified method

46. • Dentist called Buhnergraph
• Buhnergraph instrument consists of a U-shaped piece of aluminum
• Attached to the underside of the lower member of a Whip Mix
articulator. On each side is attached an adjustable arm containing a
pointed shaft which moves in and out.
Buhnergraph intraoral method

47. • New arbitrary method
• Y = 9.5 c 0.95 (X)
Y = width profile of the face measured from the ectocanthion
to the center of the external auditory meatus
X = anterioposterior position
Abdal-Hadi's technique

48. Clinical value of Hinge Axis

49. • Allows for correct recording of centric relation and its transfer to the
articulator
• Starting point of lateral movements
• Permits a change in vertical dimension
• If transferred to articulator—teeth contact each other in the articulator
exactly as they do in the mouth
• Helps in diagnosis and treatment planning

50. Variables affecting hinge axis location

51. Patient variables affecting the T.H.A.
• locations Condyle
• Asymmetry
• Inability to locate a true hinge axis
• Myospasm or joint pathosis
• Emotional conditions of patient
Factors of the recording system affecting THA
• Right angle non-right angle system of the bow
• Length of stylus arms and sharpness of styli

52. • A minimal error of 5 mm can be expected no matter what arbitrary
position might be chosen.
• Placement of the tragus-canthus line at the superior border of the
tragus of the ear will contribute to greater inaccuracy in most
patients.
• The largest percentage of true axis locations will be inferior to the
tragus-canthus line at the superior border of the tragus of the ear
summary

53. •In the final analysis, the true value of our
individual work can be measured only by the
degree of fineness with which we practice the
art of dentistry rather than by the particular
school of thought to which we adhere.
conclusion

54. • Jeffery P. Okeson. Management of temporomandibular disorders and
occlusion, 5th edition
• Zarb bolender-prosthodontic treatment for edentulous patients-12th
edition
• Shillingberg
• Heartwell
• Terminal hinge movement of the mandible J Prosthet Dent
1957;7:787-97.
• Winstanley, R. B. The hinge-axis: A review of the literature. J Oral
Rehabil 12:135-159, 1985.
• Hinge axis overview ; ashu sharma int journal of clinical dentistry
• Vol 5, no, 3 : 2012
reference

55. Thank you