Horizantal jaw relations/ dental crown & bridge courses

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 Introduction
 Definition
 Significance of centric relation
 Retruding the mandible to centric relation
 Methods of recording centric relation
 Factors influencing centric relation record
 Interocclusal records

 Eccentric relation records
 Recording of eccentric jaw relations
 Review of Articles.
 Conclusion
 Bibliography.

INTRODUCTION
Horizontal relation are those that are established
anterio posteriorly & mediolaterally,
It is classified as
1, Centric relation
2, Eccentric relation- which includes
-Protrusive
-Left & Right lateral movements

 The principles of good occlusion apply to both
dentulous & edentulous patients.
 Different requirements are necessary in the
occlusion for the complete dentures because
artificial teeth are not attached to the bone as in
natural teeth.

 To maintain stability of complete dentures, the
opposing teeth must meet evenly on both sides of
the dental arch when the teeth contact anywhere
within the normal functional range of mandibular
movements.

 An occlusion for complete dentures that provides
these even contacts can only be developed with
centric occlusion in harmony with centric relation &
smooth gliding contact from this position to any
eccentric position with in the normal range of
mandibular movements.

DEFINITION
“The maxillo mandibular 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 shapes of the articular
eminences”
This position is independent of tooth contact and is
clinically discernible when the mandible is directed
superiorly and anteriorly. It is restricted to a purely rotary
movement about the transverse horizontal axis -
GPT

Boucher defined as “The most posterior relation of
the lower jaw to upper jaw from which lateral
movements can be made at a given vertical
dimension”
Ramsfjord defined as “a clinically determined
position of mandible placing both condyles into
their anterior uppermost position. This can be
determined in patients without pain or
derangement in TMJ”

TWO DIMENSIONS OF CENTRIC RELATION-
DUAL CENTRIC
Centric relation should be understood as a
complex term with a condylar and mandibular
dimension. the condylar centeric position should
be differentiated from mandibular centric position.
1.condylar centric position - condyle disc fossa /
eminentia relationship
2. mandibular centric position – maxillomandibular
position
both these components of centric relation coexist
collectively known as centric relation

Significance of Centric Relation:
 It is a definite learned position which is independent
of the presence or absence of teeth.
 It is reproducible ,repeatable and
recordable position.

 If the occlusion of artificial teeth do not coincide, there is
instability of the dentures leading to pain & discomfort

RELATING CENTRIC RELATION TO THE HINGE
AXIS
During mandibular opening movement the
condyles rotate initially in a hinge and later in a
translatory motion.A pure hinge movement of the
condyle occurs only when the condyle is in its
centric position.

 Combinations of translation and hinge movement
take place when the condyle moves anterior to
centric relation.
Hence ,centric relation is known as the Terminal
hinge relation.

CHARACTER OF OCCLUSION IN CENTRIC
RELATION:
There are two concepts:
Point centric :
Long centric/ Freedom in centric / Area centric:

Point centric :
This happens when centric occlusion and centric
relation coincide. It is a precise location of centric
occlusion in centric relation. It is a maximum
intercuspation seen or given in centric relation.

Long centric/ Freedom in centric / Area centric:
When centric relation and centric occlusion do not
coincide, a freedom is given to close the
mandible either into centric relation or slightly
anterior to it in centric occlusion with a smooth
gliding, without effecting and change in vertical
dimension of occlusion.

1) Minimal Closing Pressure :
 Minimal displacement of the tissue
 Opposing teeth to touch uniformly and
simultaneously at their first contact.
CONCEPTS AND OBJECTIVES IN RECORDING
CENTRIC RELATION:

ADVANTAGES
 Uniform contact will not stimulate the patient to
clench the teeth
 Relaxes the closing muscles.

2) Heavy Closing Pressure:
 Tissues under bases is displaced while
the record is made
 Produce same displacement of the
soft tissues as would exist when heavy
closing pressure are applied on the
dentures.

DISADVANTAGES
 Uneven contacts which tends to clench the
teeth
 Thus causing soreness under the denture bases
& changes in the residual ridges

RELATING CENTRIC RELATION TO CENTRIC
OCCLUSION:
 Centric relation is a bone to bone relation
 Centric occlusion is a relationship of upper and
lower teeth to each other.
 Centric relation must be accurately recorded so
that centric occlusion can be built to coincide with
it.

When natural teeth are removed,many
receptors that initiate impulses resulting in
positioning of mandible away from deflective occlusal
contacts into centric occlusion are lost or destroyed.
Therefore edentulous patients cannot control
mandibular movements or avoid deflective occlusal
contacts in centric relation as in dentulous patients.

These deflective occlusal contacts in centric
relation causes movement of the denture bases or
direct the mandible away from the centric relation.
Thus centric relation must be recorded for
edentulous patients so that centric occlusion can be
established in harmony with this position.

Retruding the mandible to centric relation:
Difficulties seen are
 Biological
 Psychological
 Mechanical

Methods of assisting the patient to retrude the
mandible:
Instructing the patient to:
 Relax the jaw ,pull it back and close slowly and easily
on back teeth.[ never ask the patient to bite]
 Get the feeling of pushing your upper jaw out and
close your back teeth together.

 Protrude and retrude the
mandible repeatedly as the
patient holds the fingers lightly
against the chin.
 Turn the tongue backwards
towards the posterior border
of the upper denture.
 Ask the patient to swallow &
conclude the act with the
blocks in contact.

 Assist the patient to
retrude the mandible by
placing the index fingers
on the buccal flanges on
the premolar regions
with the thumbs under
the patients chin.

Factors Influencing Centric Relation Records
 The resiliency of the supporting tissue.
 The stability of the recording bases.
 The TMJ and its associated neuromuscular
mechanism.
 The nature of pressure applied in making the
recording.

 The technique in making the recording & the
associated recording devices used
 The skill of the dentist.
 The health & the co-operation of the patient.
 The maxillomandibular relationship

Primary 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.

 Methods of recording the centric jaw relation
 Physiological methods
 Tactile or inter-occlusal check record method
 Pressure less method
 Pressure method
 Functional method
 Needle house method
 Patterson method
 Graphic method
 Intraoral
 Extraoral

Physiological / tactile / interocclusal check record
method:
History
 In 1756,Philip pfaff, the dentist of Frederick the great
of Germany, was the first to describe this technique.
 The direct interocclusal record during that period was
a non-precision jaw record obtained with a
thermoplastic material, usually wax or compound.
 This was known as “mush” “biscuit” or “squash bite.

 Hanau[1929] was 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”.
 This became a major factor in “check bite”
techniques.

 Schuyler[1932] preferred modelling compound to
wax for the occlusal records
 Wright (1939) described the four factors which
affected the accuracy of records-
1. Resiliency of tissues.
2. TMJ & neuromuscular control
3. Fit of bases
4. Pressure applied

 Payne[1955] & Hickey[1964] stated a
preference for plaster
 Trappzzano[1955] stated that wax check
bite method was the technique of
preference
 Boos[1959] stated that it was important to
avoid torsion when recording centric relation
& felt that plaster & zinc oxide eugenol
paste was more accurate

 Scyhyler, Payne and Trapozzano advocated the
use of light pressure
 The problem of pressure in any record was
recognized by Boucher (1960) who wrote,
“In addition to technical errors are the errors
which occur as a result of failure to control jaw
activities and pressure at the time of registration”.

Interocclusal records
1. Impression compound
2. Wax
3. Zinc oxide eugenol paste
4. Impression plaster
5. Bite registration paste

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

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.

Nick and notch method:
 Nick and notch are cut
on the maxillary occlusal
rim and a trough on the
mandibular rim.
 Interocclusal record
material is placed on
the troughs created on
mandibular occlusal rim.

 Patients is asked to close in centric
relation.After the material is set,occlusal rims
are removed and articulated.
 In this method, the final centric relation is
recorded after establishing a proper vertical jaw
relation.

Verification of Centric Relation
Wax check bite record
Palpating the temporalis and the masseter
muscles.
Use of guide lines on the occlusion rims

Functional/chew in Method :
HISTORY
 Functional recordings were described as early as
1910 by Greene where he used a pumices and
plaster mixture in one of the rims and instructed the
patient to grind the rims together. The teeth were
set to the generated paths.

 Boos (1959) felt that it was essential that all
registrations be made under the biting force so that
the displacement of the soft tissues which occur in
function would occur during bite registration

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.

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

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.

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

 When the pumice and carborundum 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.`

NEEDLE POINT TRACING:
HISTORY
 The earliest graphic recording Were based on
mandibular movements by Blackwill in 1866. The
intersections of the 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 in 1897, and the technique was improved
and popularized by Gysi around 1910”

 Gysi’s tracer was an Extraoral incisal tracer in
which the plate was attached to the mandibular
rim & spring loaded pin was mounted on the
maxillary rim.

 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 jack 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.

 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.

 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

 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.

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

Intra-oral Extra-oral
. Tracing not visible when being made
Tracings are small as they are located close to the centre of
rotation. Therefore difficult to locate the apex.
More accurate than extra oral as it is made closer to the center of
rotation of the condyle
.
Plate and styles not hindered by the position of lips and cheeks.
Lips and cheeks in passive relation
.
Accuracy of the record cannot be assessed as the record bases may
shift during the recording
.
Example:
Seidal tracer
Ballard tracer
Messermar tracer
Cobble tracer
Visible when the tracing is being made
Larger tracings easier to locate the apex
.
Less accurate than intra oral as made further away from the center
of rotation.
The lips and cheek interfere with the position of the plate and the
styles.
Does not keep the lips and cheek in passive relation.
Accuracy can be assessed virtually.
Example:
Hight tracing device
Stansberry tracers
Philips extra-oral tracer
Sears trivet

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

Hight extra oral tracer assembly Sears extra oral tracer assembly
Swissdent ball bearing bite recorder Microtracer for intra oral use

 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.

 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.

ADVANTAGES
 Tracing point is much larger because they are
made farther from the centers of rotation & the apex
is more discernible
 Extra oral tracings are visible when the tracings are
made, therefore patients can be guided & directed
more intelligently

 The stylus can be observed in the apex of the
tracing during the process of injecting plaster
between the occlusal rims & no hole is required.

Classical, pointed form
The symmetry indicates an
undisturbed movement sequence in
the joints and uniform muscle
guidance.
Evaluation of Gothic Arch Tracings:
Classical flat form
Indicates distinct lateral movements
of the condyles in the fossa.

Weak Gothic arch tracing
Indicates a lax and negligent performance
of the movements. The registration must be
repeated: Stronger movements must be
demanded from the patient.
Asymmetrical form
The tracing indicates a distinct inhibition of
the forward movement on one side of joint.

Miniature Gothic arch tracing
This tracing points restricted
mandibular movements.
•Due to badly fitting and pain-
causing record bases or
•Long standing edentulous state with
inhibited movement in the joints.

Double arrow point
Interupted gothic arch
Atypical form - bruxism

Intra-oral tracing devices
 It is a combination of a central – bearing
point and plate with a needle point tracing
made inside the mouth.
 The bearing point is sharp which makes a
tracing on the opposing central bearing plate .

A hole may be drilled at the apex of the
tracing to ensure that the patients jaw is in the
most retruded position while the registration is
being recorded.
A plastic piece with a hole in the center can
also be placed at the apex.

DISADVANTAGES
 Tracings are small, hence its difficult to find the
apex.
 The tracer must be seated in the hole at the point
of the apex to assure accuracy when injecting
plaster between the occlusion rims.
 If the patient moves the rims before they are
secured, the records shift on their basal seat which
destroys the accuracy.

Williamson,Bowley and Randy :
Mandibular denture base
stability has been reported to be increased by
using an central bearing intra oral gothic arch
tracing device,as it provides equalization of
occlusal pressure.

Digital Gothic Arch Tracing:

Other methods of recording centric relation:
 Strips of celluloid placed between the rims
 Heating the surface of one of the rims
 Softened wax placed over the occlusal surface of
the mandibular posterior teeth
 Soft cones of wax placed on the lower denture
bases

 Pantographic tracing
 It is defined as, “A graphic record of
mandibular movement in three planes
as registered by the styli on the
recording tables of a pantograph;
tracings of mandibular movements
recorded on plates in the horizontal and
sagittal planes” – GPT.

 It is a three-dimensional graphic tracer.
It is the most accurate method available
to record centric jaw relation.
 Even eccentric jaw relation can be
recorded using these instruments.
 These equipments are very
sophisticated and are generally not used
in the fabrication of complete dentures

 The instrument used to do a
pantographic tracing is called a
pantographic tracer.
 A pantographic tracer is defined as, “An
instrument used to graphically record
one or more planes paths of the
mandibular movement and to provide
information for the programming of the
articulator” – GPT

 A pantographic tracer has six flags:
 Two flags located perpendicular to one
another near the condyles.
 Totally there are four flags adjacent to
the right and left condylar guidance's.
They locate the actual (true) hinge axis.
 Two flags are placed in the anterior
region. They record the antero-posterior
movements.

Consequences of recording incorrect centric relation
1. Denture instability
2. TMJ dysfunction
3. Mucosal ulceration and irritation
4. Spasm of muscles
5. Resorption of bone

Eccentric relation records
 An eccentric maxillo-mandibular relation is any
relationship of the mandible to the maxillae other
than the centric relation.
 It is recorded to adjust the lateral and horizontal
condylar inclinations.

 The adjustment permits the condylar elements to
travel to and from the centric and eccentric
positions and make it possible to arrange the teeth
for complete dentures in balanced occlusion.
 The eccentric positions to be recorded are the
protrusive and the right & left lateral.

Tactile or Inter Occlusal Check Record
 The preferred time to make the record is during the
try-in procedure
 The trial dentures are inserted & the patient is
instructed to protrude his lower jaw to
approximately 5-6 mm
 Midline of maxillary & mandibular incisors should
coincide

 Once the patient has learned this position, 3 layers
of wax is placed over the mandibular teeth, seal the
wax on the lingual & buccal surface of the teeth.
 The wax is softened over the controlled water bath.

 Try-in dentures are re-inserted & the lower jaw is
protruded until the upper teeth contact the wax.
 The wax is allowed to harden and transferred to
the articulator to record the horizontal inclination.

Recording of eccentric jaw relations:
Gothic arch tracing :
(protrusive relation records)
 Measure a distance of 5 to 6 mm from the apex of
the arrow point tracing on the protrusive tracing and
mark this point
 Instruct the patient to protrude until the point of the
stylus rests in the marked point

 Inject quick setting dental plaster between the
occlusal rims.
 Free the horizontal condylar adjustment on the
articulator.
 Raise the incisal pin about one half inch from the
top of the guide table.
 Carefully seat the record bases on the cast.

 Using the locknuts as handles manipulate
one side ,then the other.
 An accurate seating of both record bases
must be secured without forcing so that the
protrusive record is not destroyed.
 Secure the lock nuts.

Lateral relation records :
Gothic arch tracing:
 Two records are required – one of right lateral and
one of left lateral
 The articulator is adjusted as each record is made.
 However with complete dentures, it is more difficult
to secure accurate & reproducible records.

 Hanau recommended a formula to arrive an
acceptable lateral inclination
L =H/8+12
L- Lateral condylar guidance
H- Horizontal condylar inclination in degrees
as established by the protrusive record
 The value of this formula is neither proved or
disproved

Atwood, D.A. A critique of research of the posterior limit of the mandibular position. J Prosthet Dent 20:21-36, 1968.
Review of literature
Atwood, D.A. Acritique of research of the posterior limit of the mandibular position. J Prosthet Dent 20:21-36, 1968.
Posterior limit of the mandible at VDO is established by structures anterior and lateral to the condyles rather than posterior to them.(lateral pterygoid
and temporomandibular ligament) The temporomandibular ligaments contain proprioceptive nerve endings susceptible to stretching leading to inhibition
of the retrusive muscles(temporalis and digastrics), and stimulation of the protrusive antagonist muscles (lateral pterygoids).

1. In biomechanical terms the centric relation is a nonfunctional position.
2. Over relatively long periods of time, the morphology of all functional surfaces of the TMJ is capable of significant adaptive alterations. These are normal
compensatory responses of skeletal units to the prior alterations of functional matrices.
3. In much shorter time periods, the dynamically fluctuant state of the neuromuscular apparatus makes it reasonably certain that intra-individual variation in
condylar positions can exist.
A functional cranial analysis of centric relation.
DCNA 19:431-442, 1975.

 Shafagh I, Yoder JL, Thayer KE. Diurnal variance of centric relation position. J Prosthet Dent 34:574-582, 1975.
 1. Centric relation was repeatable for a fewpatients but in most there was variation. The greatest variation was in the superoinferior direction.
2. In many patients the condyles were in their most anteroinferior position in the morning and in their most superoposterior position in the evening. This
may indicate that there is a diurnal pattern in the position of centric relation possibly related to fluid content in the joint.

3. Depending on one's definition of centric relation, one time of day may be favored over another due to diurnal bias. If the most retruded and superior
position of the condyles is desired, the evening seems to be a better time for making CR records.
4. Freedom to move to some degree around a clinically determined centric relation position may have merit as a treatment philosophy.

Serrano, P.T. and Nicholls, J.I. Centric Relation Change During Therapywith Occlusal Prostheses. J Prosthet Dent 51:97-105, 1984.
1. Corrective occlusion prosthesis therapy did not improve the reproducibility of centric relation in asymptomatic patients.
2. Centric relation is not one position but is a range of positions.
3. The range of CR variation is greater laterally than antero-posteriorly

The accurate determination,recording & transfer of
jaw relation records from the edentulous patient to
the articulator is essential for the restoration of
function,facial appearance and the maintenance of
patient health.

 Therefore it is emphasized that irrespective of
the method used, subsequent clinical
checking and rechecking must be done
throughout the entire denture construction
phases.
 The skill of the dentist & the co-operation of
the patient being most important factor.

References
1.Complete denture prosthetics- john p sharry
2.Essentials of complete denture- sheldon winkler
3.Syallabus for complete dentures – charles heartwell
4.Treatment planning for completely edentulous –
boucher
5. Fundamentals of occlusion and temporomandibular disorders- Jeffery P.Okeson
6.A critique of research of the posterior limit of the mandibular position. J Prosthet Dent 20:21-36, 1968.

8. Clinical implications of mandibular repositioning and the concept of an alterable centric relation. DCNA 19:543-570, 1975.
9. A reviewof some problems associated with centric relation. J Prosthet Dent 2:307-319, 1952.
10. Diurnal variance of centric relation position. J Prosthet Dent 34:574-582, 1975.
11. Centric Relation Change During Therapy with Occlusal Prostheses. J Prosthet Dent 51:97-105, 1984.
12. centric relation records review. J prosthet dent 1982 feb; 47; 141.
13. factors influencing centric relation records in edentulous mouths.
J prosthet dent 2005;93;305

Horizantal jaw relations/ dental crown & bridge courses

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