significance of centric relation in complete denture

in detail explanation of centric relation

1. Guided by
Dr. K. Murugesan (prof)
Dr. M. Vasantha kumar
(Principal & HOD)
Presented by
Dr. Siva Senthil

2. Introduction
When constructing complete dentures, there are only
approximate guides available to determine where to place
the teeth; two of the most important of these are the vertical
and horizontal relationship of the mandible to the maxillae.

3. The mandible, though, exhibits a consistent movement
vertically only when it undergoes pure rotation around a
horizontal axis, and this can be used to obtain a reproducible
mandibular position at a determined vertical dimension. At
this occlusal height, the teeth are placed so that the most
stable tooth contacts occur in maximum intercuspation.

4. Therefore a definition of centric relation for complete
denture construction needs to take into account the ability
of the mandible to obtain a consistent horizontal
relationship at which the teeth can occlude in a stable
manner once the vertical height of occlusion has been
determined. Nearly all concepts of dental occlusion have
embraced the practice of mandibular centricity

5. Centric relation
The most retruded relation of the mandible to the maxillae when
the condyles are in the most posterior unstrained position in the
glenoid fossae from which lateral movement can be made at any
given degree of jaw separation (GPT-1)
The most retruded physiologic relation of the mandible to the
maxillae to and from which the individual can make lateral
movements. It is a condition that can exist at various degrees of
jaw separation. It occurs around the terminal hinge axis. (GPT-3)

6. The maxillomandibular relationship in which the condyles articulate
with the thinnest avascular portion of their respective disks with the
complex in the anterior-superior position against the shapes of the
articular eminencies. This position is independent of tooth contact.
This positionis clinically discernible when the mandible is directed
superior and anteriorly. It is restricted to a purely rotary movement
about the transverse horizontal axis.
GPT - 5

7. The most posterior relation of the lower to the upper jaw
from which lateral movements can be made at a given
vertical dimension (Boucher).
A maxilla to mandible relationship in which the condyles
and disks are thought to be in the midmost, uppermost
position. The position has been difficult to define
anatomically but is determined clinically by assessing when
the jaw can hinge on a fixed terminal axis (up to 25 mm). It
is a clinically determined relationship of the mandible to the
maxilla when the condyle disk assemblies are positioned in
their most superior position in the mandibular fossae and
against the distal slope of the articular eminence (Ash).

8. A clinically determined position of the mandible placing
both condyles into their anterior uppermost position. This
can be determined in patients without pain or
dearrangement in the TMJ (Ramsfjord)
CENTRIC OCCLUSION
The occlusion of opposing teeth when the mandible is in
centric relation. This may or may not coincide with maximal
intercuspal position.(GPT-7)

9. CENTRIC RELATION RECORD
A registration of the relationship of the maxilla to the mandible
when the mandible is in centric relation. The registration may be
obtained intraorally or extraorally. (GPT-7)
TERMINAL HINGE AXIS
Terminal hinge axis is the most retruded hinge position. Terminal
hinge position is significant because this position is learnable,
repeatable and recordable which coincides with the position of
centric relation. Since the rotation of condyles occurs when the
mandible is in its terminal retruded centric relation position, it was
known as terminal hinge axis.(GPT-7)

10. CENTRAL BEARING TRACINGCENTRAL BEARING TRACING
The pattern obtained on the horizontal plate using with a
central bearing tracing device (GPT-7).

11. CHANGING DEFINITIONS OF CENTRIC CHANGING DEFINITIONS OF CENTRIC
RELATIONRELATION
McCollum (1920) – Rear most condylar position.
He showed that the condyle had a pure rotational movement
when the operator guided the mandible to position the condyles
in the most retruded position in the glenoid fossa. He was the
first to name this position as centric relation.
Granger (1962) – up most rear most position.
A second component for bracing namely a most superior
position was considered necessary since the condyle was
unstable when it was only in the most posterior position.

12. Stuart (1969) – Rearmost uppermost midmost condylar
position (RUM) in the glenoid fossa.
A medial component was added for the stable condylar
position (3 dimensional positions). It was considered a
physiological condylar position harmonious with centric
occlusion.
Celenza (1978) – Condyle disk assembly brazed superiorly
and anteriorly against the posterior slope of eminentia.
Today this is widely accepted for condylar position.

13. THE OBJECTIVE OF RECORDS OF CENTRIC
RELATION IS TO RELATE THE MANDIBLE TO
THE MAXILLA IN SUCH A AWAY THAT THERE
CAN BE NO FULCRUM ON THE TEETH, BUT
ONLY IN THE TEMPORO MANDIBULAR JOINT
When the ravages of pathosis are present, the fulcrum
must be in the temporomandibular joint if the
destruction by the pathosis is to be minimized .
This is mechanical necessity which has biologic
soundness.
Victor O. Lucia J Prosthet Dent 1964:14:3:492

14. Hypothesis underlying the determination of
centric relation
The hypothesis underlying these techniques can be
derived from one of the following three theoretical
positions of the condyles in the glenoid fossa.
1.Hinge axis theory.
2.The rest position theory.
3.The most retruded unstrained position
Mohamed A. El-Aramany J Prosthet Dent 1965:15:6:1043
Shillingburg. Fundamentals of FPD. P-35

15. HINGE AXIS THEORY:
Supported by large number of writers.
By determining the posterior terminal hinge position the centric
relation is established in all dimension.
REST POSITION THEORY:
Suggested by Thompson .
Craddock postulated that when the mandible assumes the position of
rest it is in centric relation.
Mohamed A. El-Aramany J Prosthet Dent 1965:15:6:1043

16. The most retruded unstrained position of the mandible
Very difficult to determine, when the position is
strained or unstrained , since depends up on the
subjective judgment of patient and dentist.

Mohamed A. El-Aramany J Prosthet Dent 1965:15:6:1043

17. The time factor called “ circadian periodicity” or “circadian
rhythmicity”has been introduced as an additional variable in the
maxillomandibular relationship.

Grasso and sharry found that time was a significant variable
affecting the apex position of the needle point tracings.
Diural variance of centric relation
position
Iraj Shafagh et al J Prosthet Dent. 1975:34:5:574

18. On the basis of analysis of data collected, they say that
Sequential registration of centric position was exactly
repeatable in a few patients , but for most , a dispersion
pattern resulted which varied among individuals .
The greatest variability registered at the level of condyles
was mostly superoinferior, with little mediolateral variability.
Iraj Shafagh et al J Prosthet Dent. 1975:34:5:574

19. In many subjects , records obtained in the morning showed
the most anteroinferior position of the condyles and those
made at night showed the most postero superior position of
the condyles.
This indicates that centric relation follows a diurnal rhythm
which might be due to varying shapes and varying fluid
content of the temporo mandibular joint.
If the most retruded and superior position of the condyles
is desired , the evening seems to be a better time for making
centric relation records.
Iraj Shafagh et al J Prosthet Dent. 1975:34:5:574

20. Factors influencing centric relation
record
The resiliency of supporting tissues
The stability of the recording bases.
The temporomandibular joint and its associated
neuromuscular mechanisms.
The character of pressure applied in making the recording.
The techniques used in making the recording and the
associated recording devices used.
The skill of the dentist
A.Albert yurktas J Prosthet Dent 1964;14;6;1054

21. The health and cooperation of the patient
The posture of the patient
The character or size of the residual alveolar arch.
The amount and character of saliva
The size and position of tongue.

22. SIGNIFICANCE OF CENTRIC
RELATION

23. Hinge Position is Repeatable
It is a repeatable, recordable position and a physiologically
acceptable position for mastication & deglutition.
The maxillo-mandibular musculature is so arranged that it is
simple to move the mandible into centric relation.
Boucher`s prosthodontic treatment for edentulous patients.9thedition,p-
281

24. BUFFER SPACE FOR THE
CONDYLE
In centric relation 0.2 – 0.3mm space exists between the
condyle and fossa.
This space is essential to healthy maintenance of TMJ.
When heavy pressure are transfer to the condyle during
function, the space allows condyle mobility and prevents
direct pressure to the fossa.

25. CONDUCIVE TO HEALTH
Relatively Symmetrical Position
Brill et al - pain & loss of occlusal sense when not in CR
Less chance of muscle strain which might occur in non-
centered positions
Functional movements like chewing and swallowing are
performed in this position, because it is the most
unstrained position.
Boucher`s prosthodontic treatment for edentulous patients.9thedition,p-281

26. STABILITY OF DENTURE
Stability of denture bases is jeopardized.
Stability of natural teeth is jeopardized when mandible is
deflected away.
Patients cannot close their teeth into centric occlusion if it is
off centered.
Errors can go undetected when centric relation is not used
as a horizontal reference relation.
Boucher`s prosthodontic treatment for edentulous patients.9thedition,p-281

27. Reasons to construct a complete
denture in CR are:
1. Mounting the casts in CR eliminates the problem of determining how far
anteriorly to this most retruded position centric occlusion should be
established. 
2. CR must be recorded to permit accurate adjustment of the condylar guidance
of the articulator for eccentric movements. 
3. Opposing artificial teeth will likely contact in CR whenthe proprioception of
the natural teeth is absent. 
4. An accurate CR record orients the lower cast in the correct relationship to
the opening axis of the articulator.
Hicky .J.A. DCNA Nov 1964:587-600.

28. THE BIOMECHANICS OF
FUNCTIONAL OCCLUSAL CONTACTS
Balanced articulation is achieved by.
The use of cusped artificial teeth; modifications of these
arrangements and centric relation.
It is assumed that the teeth start by having cusp to fossa
relationships and that they are set in maximum inter
cuspation to maintain these relationships.
C.P.Owen.occlusion in complete denture.1-24.

29. As soon as the mandible moves out of centric
relation position, other factors come into play.
The incisal guidance angle and the sagittal condylar
guidance angle.
C.P.Owen.occlusion in complete denture.1-24.

30. The incisal guidance angle is formed by the amount of vertical overlap
or overbite between the teeth when viewed in the sagittal plane.

31. The sagittal condylar guidance angle is the average path taken by the condyle
during a forward movement from centric relation position, when viewed in
the sagitall plane.

32. Any forward movement of the mandible is also a
downward movement: if record blocks are placed
midway between the incisors and condyles on a flat
plane, they will separate if the mandible moves
forwards.
Similarly, if teeth are placed in place of flat record
blocks, again on a flat plane, they will also separate,
unless they can be given cusps with inclines.
C.P.Owen.occluasion in complete denture.1-24.

33. The so-called “Christensen Phenomenon” in which the mandibular path in a forward
direction produces a downward displacement of the mandible. This means that record
blocks, for instance, set on a flat plane will separate when the mandible moves
forwards.

34. The incisal guidance angle is 10
0
and the sagittal condylar guidance angle is
30
0.
teeth have been placed on a plane, and have 20
0
cusp angles, as
illustrated by the distal

cusp of the upper first molar.

35. The cusp angle of these teeth is 20
0
when the teeth are positioned upright
against a flatplane.
C.P.Owen.occlusion in complete denture.1-24.

36. The mandible’s path is an arc which is steeper posteriorly than anteriorly. The only teeth that
will remain in contact are those mid-way between the 30
0
movement posteriorly and 10
0

movement.

37. The teeth are tipped five degrees, making the effective cusp angle of the distal
slopes 25
0
, and reducing the mesial slopes to 15
0
C.P.Owen.occlusion in complete denture.1-24.

38. The teeth are tilted to increase the effective cusp angles to compensate for
the arc of the path of the mandible in protrusion.
If all the cusp tips are connected, it will be found that they now no longer
lie on a straight plane, but on a curve: this curve will be in harmony with
the arc of movement of the mandible, as it will have compensated for that
arc, determined by the incisal and condylar guidance angles.

39. Requirements for Making Centric
Relation Records

To record the correct horizontal relationship of the
mandible to the maxilla.
To exert equalized vertical pressure.
To retain the record in an undistorted condition until the
cast has been accurately mounted on the articulator.
R.H.Kingery.J prosthet dent.1952;2;3;307.

40. PROBLEMS OF ERROR ASSOCIATED
WITH CENTRIC RELATION
Errors
Positional error
Technical error
R.H.Kingery.j prosthet Dent .1952;2;3;307

41. Position error
1.Failure of operator to register correct
horizontal relationship.
2.Failure of operator to record equalized vertical
contact.
3.Application of excessive closure pressure
during recording.
4.Changes in the supporting area.
R.H.Kingery.J prosthet dent.1952;2;3;307

42. TECHNICAL ERROR
Ill-fitting occlusion rims.
Indiscriminate opening or closing of articulator.
The slight shifting of teeth in final arrangement
in the wax.
R.H.Kingery.J prosthet dent.1952;2;3;307

43. SYMPTOMS OF UNEQULIZED
VERTICAL CONTACT
Loss of retention.
Irritation on the crest of the lower ridge in the area
of premature contact.
One or several teeth seem to be long to the patient.
Premature contact anterior or posterior.

44. SYMPTOMS OF AN ERROR IN
HORIZONTAL RELATIONSHIP
Horizontal relationship error may occur either
anterior or posterior to centric relation.
Anterior error
Symptoms
1.Looseness in the mandibular denture.
2.Denture consciousness.
3.Irritation under anterior lingual flange of
mandibular denture.
R.H.Kingery.J prosthet dent.1952;2;3;307

45. POSTERIOR ERROR
This is extremely rare error may occur as a result of
excess closure of articulator.
1.Losseness of maxillary denture.
2.Irritation under the anterior labial flange of the
mandibular denture.

R.H.Kingery.J prosthet dent.1952;2;3;307

46. Methods Of Recording Centric Relation
Physiological / tactile / interocclusal check
record method.
Functional/ chew in method.
-Patterson technique
-Needle house technique
Graphic method.
-Intra oral tracing
-Extra oral tracing

47. DIRECT CHECK BITE
INTEROCCLUSAL RECORD
Oldest type of centric relation record .
Phillip Pfaff , the dentist of fedrick the great of germany , was
the first to describe this technique of”taking a bite” In 1756.
Non precision jaw record obtained by placing a thermoplastic
material- wax or compound ,between the edentulous ridges and
having the patient close into the material .
This was known as the “mush”, “biscuit” , or “squash “ bite
Michael L. Myers J Prosthet Dent:1982:47:141-145

48. Christensen used- “impression wax “ for “bite” records In 1905.

Greene - mushbite made from modeling compound in which he used
a plaster wash to achieve a more accurate record -1910.
One early method was to adjust the occlusion rims to the chosen
vertical dimension of occlusion, have the patient close in the retruded
position, and attach the rims together for mounting on an articulator.
This was usually done with staples or by sealing the rims with a hot
instrument.
Michael L. Myers J Prosthet Dent:1982:47:141-145

49. One practice was to soften one of the occlusal rims and have the
patient close to a vertical dimension determined by the dentist .

Brown recommended repeated closures into softened wax rims -
1954.
Greene had his patients hold their jaws apart for 10 seconds to
fatigue the muscles and then had them snap the rims together.
He then made lines in the rims to orient them after removel from
the mouth
Michael L. Myers J Prosthet Dent:1982:47:141-145

50. Hanau was one of the first individual to be concerned about
equalization of pressure when recording the bite .
He coined the word “realeff” which is formed by the beginning
letters of the words “resilient and like effect”
Michael L. Myers J Prosthet Dent:1982:47:141-145

51. Wright (1939) described the four
factors which affected the accuracy
of records-
1.Resiliency of tissues.
2.Saliva film,
3.Fit of bases
4.Pressure applied

52. Physiological / Tactile / Interocclusal
Check Record Method:
It is particularly indicated in situation of
Abnormally related jaws
Supporting tissues that are excessively displaceable
Large tongue.
Uncontrollable or abnormal mandibular movements
To check the occlusion of the teeth in try-in dentures

53. The technique for this record is divided into two
steps-
1.Tentative records using occlusion rims attached to
accurate stable bases.
2.Inter occlusal check records with teeth arranged for
try-in.

54.  In this method the vertical dimension is
established first .
A tentative centric relation is recorded, occlusal
rims are articulated using tentative records and
artificial teeth are arranged.
Now the try-in dentures are ready for making the
inter-occlusal check record.

55. The try-in dentures are inserted into patient
mouth ,recording material is loaded onto the
occlusal surface of posterior teeth in the mandibular
occlusal rim and patient is asked to slowly retrude the
mandible and close, make sure there’s no tooth to
tooth contact.
The horizontal Condylar guide locks in the articulator
are unlocked and the try-in dentures are placed on
their articulated casts.

56. Recording material on the buccal aspect of mandibular
teeth is scraped off and the articulated casts are adjusted
to fit into the check record.
If the tentative record is accurate and is same as the
check record then both Condylar elements will contact
against the centric stops.
If any one of the Condylar elements are not touching,
then one or the other record is inaccurate.

57. FUNCTIONAL RECORDING
Functional records were described in dental literature as early as
1910.
Greene used a pumice and plaster mixture in one of the rims
and instructed the patient to grind the rims together.
Needles mounted three studs on maxillary rims which cut
arrow tracing into mandibular compound rims.
Patterson cut a trough in the upper and lower rims.
These were filled with a carborundum and plaster mixture. The
patient would move his jaws and grind the rims until the proper
curvature has been established.
Michael L. Myers J Prosthet Dent:1982:47:141-145

58. The functional technique developed by meyer used soft wax
occlusion rims.
BOOS used the gnathodynamometer to deteremine the vertical
and horizontal position at which a maximum biting force could be
produced.
Shanahan in his physiologic technique placed cones of soft wax
on mandibular rim and had the patient swallow several times.
Michael L. Myers J Prosthet Dent:1982:47:141-145

59. Functional/chew in Method ::
Needles-house technique:

Compound occlusal rims with 4 metal styli placed in
the maxillary rim.
When the mandible moves with the styli contacting
the mandibular rim, the styli cuts 4 diamond shaped
tracings.

60. The pathways cut into the modeling compound
indicating both the centric position and the
eccentric mandibular excursions.
The records are placed on a suitable articulator to
receive and duplicate the records.

62. The Patterson method:
Uses wax occlusal rims.
A trench is made in the mandibular rim and a
mixture of half plaster and half carborundum or
pumice paste is placed in the trench.

63. When the plaster & pumice are reduced to the pre
determined height the patient is asked to retrude
the mandible and the occlusion rims are joined
with metal staple pins.`

64. Plaster pumice rims tends to be rather messy an
alternative is modelling wax mixed with a little
carding wax to render it displaceable, the rims are
covered with the tin foil to prevent them sticking
together while the patient squeezes them into his
own individual occlusal curves.

66. Disadvantages
1.The displaceable basal tissues, the resistance of the
recording medium and the lack of control of equalized
pressure in the eccentric relation contribute to
inaccuracies.
2.Patients should have a good neuromuscular co-
ordination and should be capable of following
instructions.

67. The earliest graphic recording were based on
studies of mandibular movements by Blakwill
-1866.
The intersection of arcs produced by the right
and left condyles formed the apex of what is
known as the Gothic arch tracing.
The first known “Needle point tracing” was
by Hesse - 1897 and the technique was
improved and popularized by Gysi around
1910.
GRAPHIC RECORDING
Michael L. Myers J Prosthet Dent:1982:47:141-145

68. Stansbery introduced a technique which incorporated a curved
plate with a 4inch radius(corresponding to monsoon`s curve)
mounted on the upper rim - 1929.
Robinson designed the equilibrator a tracing device with a hydraulic
system and four bearing pistons, one each in the bicuspid and
molar region

Michael L. Myers J Prosthet Dent:1982:47:141-145

69. Phillips(1927) recognized that any lateral movement of
the jaw would cause interference of the rims resulting
in a distorted record.
He developed a plate for the upper rim under tripoded
ball bearing mounted on a jacks screw for the lower
rim. The innovation was named the “Central bearing
point”, which was supposed to produce the
equalization of pressure on the edentulous ridges.

70. Stansbery (1929) introduced a technique which
incorporated a curved plate corresponding to monson’s curve.
He mounted this on the upper ring and a central
bearing screw was attached to a lower plate
corresponding to the reverse monsoon curve. After the
tracing was made , a biconcave centric registration was
obtained using plaster.

71. Later gothic recording methods used the central
bearing point to produce gothic arch tracing.
Various tracing devices were designed by Flight,
Phillips, Terrell, Sears, House, Messerman and
others

72. The graphic recording like the check bites records
received much praise and criticism. Critics of Gothic
arch tracing stated that equalization of pressure did not
occur, prognathic and retrognathic patients could not be
used, flabby tissues and large tongues could cause
shifting of the bases and finally too much of patient
cooperation was needed.

73. Graphic Methods:
Graphic methods are of two types:
Arrow point tracing.
- Extra oral tracing.
- Intra oral tracing.

74. Extra Oral Tracing Assembly
It has a central bearing device consisting of a central
bearing point & a plate
 It has a tracing device consisting of a stylus & a
recording plate

75. Technique for Gothic Arch Tracing:
 Make accurate stable maxillary and mandibular
record bases.
Contour the wax occlusal rims.
Establish the vertical jaw relation
Make a face bow transfer and mount the maxillary
cast .

76. With soft wax make a tentative centric relation
record.
 Adjust the articulator with the condylar elements
secured against the centric stops.

77. Relate the maxillary occlusion rims in the soft wax
record and attach the mandibular cast to the
articulator with plaster.
 Reduce the mandibular occlusal rim to provide 2 mm
while maintaining the occlusal plane

78. Central bearing device is attached to the occlusal rims
taking care to centre them laterally &
anteroposteriorly.
Mount the tracing device, be sure to attach the devices
securely to the occlusion rims.The stylus is attached to
the maxillary rim and the recording plate on the
mandibular.

79. Seat the recording bases with the attached recording
devices ,make sure that there is no interference
between the occlusion rims when the mandible is
moved in any direction.
Retract the stylus and conduct training exercises
with the patient.

80.  When the patient is proficient in
executing the mandibular
movements prepare the tracing
plate to record the tracing by
coating with thin coat of
precipitated chalk in denatured
alcohol.
Develop an acceptable tracing by
dropping the stylus to the
record plate.

81. When a definite arrow point tracing
with a sharp apex is made, have the
patient retrude the mandible to the
centric relation.
Inject quick setting dental plaster
between the occlusion rims.
Remove the assembly and mount the
mandibular cast with the new record.

82. CONCLUSION
Centric relation position is a repeatable and recordable
constant position of the condyle in the glenoid fossa which
should be recorded with utmost care for the fabrication of
complete dentures.
The accurate determination, recording & transfer of jaw
relation records from the edentulous patient to the
articulator and development of balanced articulation is
essential for the restoration of function, facial appearance
and the maintenance of patient health. This will render a
good service of the denture.