Centric relation is the most posterior position of the mandible in relation to the maxilla, from which lateral movements can be made. It is a reproducible position that serves as a reliable guide for developing occlusion in complete dentures. There are various methods for recording centric relation, including functional methods like the needle house method and excursive methods using intraoral or extraoral tracings. Establishing accurate centric relation is important for proper functioning, aesthetics, and comfort of complete dentures.

1. Submitted by
Anto Antony
2006 Batch

2. Definition

 1. Centric relation is the most posterior relation of
the mandible to the maxilla when the condyles are in
the most posterior unstrained position in the glenoid
fossa from which lateral movements can be made at
any given degree of jaw separation (GPT-4)
 2. The maxillomandibular relationship in which the
condyles articulate with the thinnest avascular
portion of their respective discs with the complex in
the anterior superior position against the slopes of
the articular eminence (GPT-5)

3. Significance of Centric
Relation

 1. It is a reproducible and recordable position, which
can be repeatedly arrived at and thus serves as a
reliable guide to develop centric occlusion in
complete dentures.
 2.Centric relation become starting point to plan and
execute the occlusion.
 3. Centric relation is related to terminal hinge axis. In
centric relation, condyles exhibit pure rotation
without any translation.

4. 
 4. This position is more definite than the vertical
relation and is independent of the presence or
absence of teeth.
 5. The final act of masticatory stroke ends in centric
relation.
 6. It is a border position and the posterior limit of the
envelope of motion

5. METHODS OF ASSISTING THE PATIENT TO
MOVE THE MANDIBLE TO THE CENTRIC
RELATION

 1. The patient is instructed to let his or her jaw relax,
pull it back and close slowly on the back teeth.
 2. The patient is instructed to get the feeling of
pushing his upper jaw out and then close the mouth
with back teeth in contact.
 3. Assist the patient to protrude and retrude the
mandible repeatedly with the operator holding the
finger lightly against the chin.

6. 
 4. Boo's series of stretch exercises: The patient is
instructed to open the mouth wide and relax, to move
the jaws to left and relax, to move the jaw to the right
and relax and to move the jaw forward and relax in
series of movements. The results to be expected are for
the patient to be able to follow the dentist's directions in
moving the jaw to centric relation and to the desired
eccentric positions

7. 
 5. The patient can be instructed to turn the tongue
towards the posterior border of the upper denture base
and close the rims together until they meet. The
disadvantage with this method is the likelihood of
displacing the mandibular record base by the action of the
tongue.
 6. The patient is told to swallow and conclude the act
with the occlusal rims in contact. However, the person
can swallow when the mandible is not completely
retruded. This method must be verified by other
techniques.

8. DIFFICULTIES IN GUIDING MANDIBLE TO
CENTRIC RELATION POSITION

 Biologic: It may arise due to lack of coordination of
opposing muscles. When the patient is requested to
close the jaws in the retruded position, the lack of
synchronization between the protruding and
retruding muscles may be caused by habitual
eccentric jaw positions adopted by patients to
accommodate to malocclusion..

9. 
 Psychological: The more the operator becomes
irritated over the apparent lack of ability of the
patient to retrude the mandible.Then dentist must be
prepared to calmly spend adequate time in securing
the centric relation records.

10. 
 Mechanical: It is essential that the denture bases on
which the occlusal rims is made fit perfectly and do
not interfere with each other. Failure of adaptation of
denture base to the tissue surface may result in
unevenly distributed pressure on the underlying
resilient tissue leading to discrepancy in jaw relation
recording.

11. VARIOUS METHODS OF RECORDING
CENTRIC RELATION

 Functional (Chew-in) methods
 Needle house method,
 Patterson's method.
 Meyer's method.
 Excursive methods (Graphic method)
 Intraoral tracing. [Intraoral balancer (Hanau co.), S-A gothic
arch tracer (Tokyo shikasha)]
 Extra-oral tracing. [Height Tracer (Hanau co.)
 Tactile or interocclusal check records.
 Terminal hinge axis method

12. 
 Other methods.
 Heating the surface of one of the rims.
 Softened wax placed over the occlusal surfaces of the
occlusal rim.
 Soft cones of wax placed on the lower denture trial bases

13. FUNCTIONAL METHODS

Needle house method:
 Most commonly used method
 Occlusal rims are fabricated in impression compound
 Four metal beads are embedded in the max. premolar
& molar areas of occlusal rims
 They are inserted into patient’s mouth and close the
occlusal rim & make protrusive , retrusive , right & left
lateral movements
 Diamond shaped markings on the mandibular
occlusal rim
 The tracings incorporate the movement in three planes
and records are placed on a suitable articulator to
receive and duplicate the record.

14. 

15. Patterson's method
 A trench is to be made in
 Wax occlusion rims are used.
the mandibular rim and a
mixture of half plaster and half carborundum paste
should be placed in the trench.
 The mandibular movements generate compensating
curves in the plaster and carborundum paste.
 When the paste is reduced to the predetermined vertical
height of occlusion, the patient is instructed to retrude
the mandible and the occlusal rims are joined together
with metal staples

16. 

17. Meyer's method

 Meyer's used soft wax on the occlusal rims to
establish a generated path.
 Tin foil was placed over the wax and lubricated.
 The patient performed the functional movements to
produce a wax path.
 The plaster index was made of the wax path and the
teeth were set to the plaster index

18. EXCURSIVE METHODS

 The most common of the excursive recording is the
gothic arch tracing.
 This can be employed intraorally or extra orally.
 This tracing is shaped like a gothic arch and so is
referred to as Gothic arch tracing.
 It is also known as arrow point tracing.

19.  Intra oral

 Central bearing devices are used(Central bearing
point + Central bearing plate)
 Central bearing point attached to the max. occlusal
rim & Central bearing plate to the mandibular
occlusal rim
 Both are inserted to the patient’s mouth and asked to
perform mandibular movements
 Arrow point with sharp apex is found on the central
bearing plate

20. 
 Disadvantage:
 tracing is small, difficult to determine the apex

21. 
 Extra oral
 Central bearing point & plate is projected outside the
mouth & arrow point tracing is made at the
predetermined VD extra orally
 Advantage: - easy identification

22. 

23. 
The tracing is not acceptable unless a pointed apex is
developed.
 A blunted apex usually indicates an acquired
functional relationship. A sharp apex indicates the
position of centric relation.
 Double tracing indicates lack of coordinated
movements

24. INTEROCCLUSAL CHECK RECORDS

 It is particularly indicated in situation of:
 Abnormally related jaws.
 Excessively displaceable supporting tissues.
 Large awkward tongue.
 Uncontrollable or abnormal mandibular movements.
 To check the occlusion of teeth in trial dentures.

25. 
 Nick & notch to index the OR
 Upto 3mm wax is removed on either side of the
mandibular occlusal rim
 one or two notches are cut on the maxillary
occlusalrim, V shaped valley running totally across
the width of the max. occlusal rim.
 1 nick is cut anterior to the notch
 (nick prevents lateral movement & notch prevents
anteroposterior movements)
 4.5mm ZnOE is placed over the mandibular occlusal
rim(so 1.5mm of ZnOE projects above the occlusal
rim)

26. 
 The mand. Occlusal rim is softened & inserted into
patient’s mouth & ask to close his mouth in centric
relation
 ZnOE projecting above the trough of the mand. Rim
flows into the nick & notches
 occlusal rims are placed in a cold water bath &
excess is trimmed

27. 

28. TERMINAL HINGE AXIS:

 As in the determination of the physiologic
transverse hinge axis, the mandible is in its most
posterior relation to the maxilla when the centric
relation is recorded.
 Therefore, if the upper cast is correctly oriented to
the hinge axis of the articulator by an accurate face
bow transfer, the lower cast will also be correctly
oriented to the opening axis of the instruments when
it is transferred to the articulate with the accurate
centric relation record.

29. Other methods
 Strips of celluloid

 After adjusting the rim a strip of celluloid is placed
between the rims and pulled. If it pulls out easily it
indicates uneven contact . The rim is readjusted.
 Disadv : unequal pressure error may still be present.

30. 
 Softened wax is placed on the mandibular posterior
teeth and maxillary teeth are closed into it.
 Adv: smaller surface contact instead of large flat wax
surface
 Disadv: record has to be made at an increased
vertical relation to avoid contact of teeth.
 Swallowing technique using soft cones of wax
establish vertical as well as centric relation.
 Disadv: results are not consistent.

31. Eccentric jaw relation

 Eccentric jaw relation to be recorded are protrusive and
lateral.
 The graphic method of making maxillomandibular
relation records is performed at same sitting position.
 After mandibular cast has been mounted in eccentric
relation, the recording device is replaced in patients
mouth.
 A distance of 5-6mm is measured from the apex of the
arrow point tracing and the protrusive tracing is marked
 The patient is instructed to protrude until the point of
stylus rests the mark.

32. 
 Quick setting dental stone is injected to seal the rims.
 Horizontal condylar guidance elements on
articulator are released by turning the locknuts.
 Incisal guidance pin is raised to about one half from
the top of the guide table.
 The record bases are seated on the cast and locknuts
are manipulated on one side and then on the other
side.

33. Lateral relation records.

 Lateral relation can be recorded & used to establish
lateral guidance on certain adjustable articulators,
but they cannot be used like semi adjustable
articulators.
 Graphic methods are used in the same manner as
protrusive relation recorded except that records
required are one of right laterals and one of left
laterals.

34. 
 Hanau recommended a formula to arrive at an
acceptable lateral inclination
 L = (H/8) + 12
 Where L = lateral condylar inclination in degrees
 H = horizontal condylar inclination in degrees
as established by protrusive relation records

35.  Summary


Once the occlusal rims are individualized, the
jaw relations are established& finally recorded.
Establishing the jaw relation is an important step in
the fabrication of complete dentures. Orienting the
upper & lower denture in the correct horizontal &
vertical relation to each other is important for the
esthetics, health & comfort of the patient as well as
proper functioning of the dentures. In final analysis
it is the experience & judgment of the operator & to
some extend the patient himself, which helps in
determining what is right for the patient.

36. Referances

 Essential of Complete denture prosthodontics :
Sheldon Winkler
 Prosthodontic treatment for edentulous patient :
Boucher
 Text book of Complete denture prosthodontics :
Sarandha D.L.
 Complete denture prosthodontics : John Joy
Manappallil
 Textbook of prosthodontics – Deepak Nallaswamy.

37. 
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