Tmj instrumentation /certified fixed orthodontic courses by Indian dental academy

TMJ
INSTRUMENTATION
INDIAN DENTAL ACADEMY
Leader in continuing dental education
www.indiandentalacademy.com


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1. INTRODUCTION
2.NEED FOR RECORDING CR-CO DISCREPANCY
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1. CR DEFINITION
2. CO DEFINITION
3. CRITERIA FOR OPTIMAL FUNCTIONAL OCCLUSION
4. SIGNS & SYMPTOMS OF CR-CO DISCREPANCY
5. MOUNTED VS HANDHELD CASTS

3.METHODS OF RECORDING MM RELATIONS
4.RECORDING CONDYLAR POSITION
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a. FACEBOW
b. ARTICULATORS
c. MPI
d. ELECTRONIC MPI
d. AXIOGRAPHY
e. COMPUTERISED AXIOGRAPHY

INTRODUCTION


SYNOVIAL JOINT

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MOVEMENTS can be
1. In upper joint space - hinge
2. In lower joint space – hinge + gliding

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Goals of orthodontic treatment harmony between occlusal function and
TMJ.
Occlusion and its role on TMJ health –
DEBATABLE
Ideal occlusal relationship should
coincide with www.indiandentalacademy.com
ideal condyle-fossa

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RETRUDED AXIS POSITION –
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condyles articulate with the thinnest avascular
portion of their respective disks
anterior-superior position
discernible when the mandible is directed
superiorly and anteriorly and restricted to a purely
rotary movement about a transverse horizontal
axis.

CENTRIC OCCLUSION




The occlusion of opposing teeth when the
mandible is in centric relation.
This may or may not coincide with the maximum
intercuspation www.indiandentalacademy.com
position.

•

RETRUDED CONTACT POSITION - occlusal
position when the first tooth contact occurs on the
path of closure in the retruded axis position.

•

BENNETT ANGLE – angle at which the orbiting
condyle moves inward during laterotrusive
movement and is measured in relation to the
horizontal plane.

•

OCCLUSAL INTERFERENCE – It is any tooth
contact that inhibits the remaining occluding
surfaces from achieving stable and harmonious
contacts.

OPTIMAL FUNCTIONAL OCCLUSION
1.
2.
3.
4.
5.
6.

7.
8.

Musculoskeletally stable position.
Ideal condyle-fossa- disc relationship.
Bilateral occlusal contacts in RCP.
RCP =ICP or a slide of < than 1 mm
Working side contact during laterotrusion.
No contact on balancing side during
laterotrusion.
Full extent of jaw movement has to be recorded.
check the end-of-therapy occlusion using
mounted models.

NORMAL CONDYLE-DISC- FOSSA
RELATIONSHIP

ROTH- acceptable difference between CR and
CO -1.00 mm AP, 1.00 mm in vertical plane
and 0.5 mm in transverse plane.

SIGNS OF CR-CO DISCREPANCY
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Occlusal wear.
Excessive tooth mobility.
Temporomandibular joint sounds.
Limitation of opening or movement.
Myofascial pain.
Contracture of mandibular musculature,
making manipulation difficult or impossible.
Some types of tongue-thrust swallow.

MOUNTED VS HANDHELD CASTS
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CLINICAL

1.Patients will not willingly bite in CR if that is not
where the teeth fit best.
2. An accurate clinical assessment of occlusal
interfacing, even in CR, is suspect if tooth mobility
is present.
3. Border movements can be recorded.
4. Joint sounds can be heard.
5. Lingual perspective of teeth cannot be seen.

HAND-HELD CASTS
1.

2.

3.

When unmounted casts are set on their trimmed distal
borders, only the facial perspective of the static
occlusion can be seen. If the casts are held in the
hands without the wax bite, what is seen cannot be
relied on because all three vertical restraints are
exclusively dental.
How the teeth interrelate when functioning cannot be
assessed with hand-held casts.
Lingual perspective can be seen.

MOUNTED MODELS
Vs
HAND HELD CASTS


MOUNTED MODELS
1.

2.

3.

4.

Tooth mobility avoided by making impressions with
soft materials to prevent deflection.
once casts are mounted - uncompromised picture of the
occlusal conditions can be observed.
Mounted casts lead to better diagnosis, better results,
and to fewer retention problems.
How teeth interface in centric relation (CR) and when
functioning can be seen facially and lingually without
patient's avoidance mechanism (proprioception).


METHODS OF RECORDING
MAXILLOMANDIBULAR RELATIONS
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Thielmann (1939) – spiegelkinometer
Sears (1952) – condyle migrator.
Posselt (1957) – gnathothesiometer
Buhner – Buhnergraph – for locating centric relation and
verification of terminal hinge axis location.
Long (1973) – leaf gauge – shims made of acetate or
plastic
Williamson (1980) – vericheck
SLAVICEK (1988)- SAM articulator and MPI

VERICHECK by WILLIAMSON

The Vericheck instrument will measure the variation from
centric relation in three planes of space.

RECORDING CONDYLAR POSITION
Facebow
 Articulators
 Mandibular Position Indicator(MPI)
 Electronic MPI
 Axiography
 Computerised Axiography
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FACEBOW
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First introduced by RICHMOND HAYES- articulating
caliper
Later modified by SNOW
Serves to transfer 3-D relationship between Mx. Dental
arch and starting point of mand. movement.
Transverse hinge axis- passes thru both condyles and
associated with rotation of mand in vertical direction –
clinical relevance- orientation of the maxillary cast.
 Types
Arbitrary
 kinematic
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Primary use- mount maxillary cast accurately on
the articulator
Reference points1. Posterior- hinge axis
 2. Anterior- arbitrary
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Most semiadjustable articulators- rely on arbitrary
hinge axis.
If a discrepancy exists between the hinge axis and
the articulator axis - premature contact will occur
on the path of closure on the articulated model, not
present clinically

Arbitrary facebow transfer
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Anatomic average values used based on the work of
SNOW
Semiadjustable articulators rely on arbitrary hinge axis
location.
Line from tragus to outer canthus of eye
11-13 mm from the tragus of ear- arbitrary location.

Kinematic face bow transfer
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Required for fully adjustable articulators.
Recorded by using a special bow attached to the mandible
and is cemented to the teeth.

Facebow – SAM 2

ARTICULATORS
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First described by MITCHELL & WILKIE in 1958
Articulator- instrument that represents the TMJ and jaws
to which the maxillary and mandibular casts are
attached. means of reproducing occlusal relationships
outside the mouth.
must be able to simulate an individual’s jaw movement
mandibular movements are influenced by many soft
tissue factors, hence impossible for jaw movements to be
precisely reprodued.




semiadjustable articulators provide an adequate
representation of the true occlusion for orthodontic
diagnosis.

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Roth and Cordray - it is impossible to believe the
clinical finding as a true representation of occlusion
- occlusal interferences.

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only by articulator mounting can the true occlusion
be studied.

CLASSIFICATION OF ARTICULATORS
SEMI-ADJUSTABLE

NON-ADJUSTABLE

five records

all three records

1 or 2 records

Face bow record

Face bow record

FULLY ADJUSTABLE

Face bow record

Centric relation record Centric relation record Centric relation record
Protrusive record

Protrusive record

Lateral records
Intercondylar distance
record

Protrusive record

Non adjustable articulators
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average values are used to represent the inclination
of the glenoid fossa and condyle fossa relationship.

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cannot accurately reproduce an individual’s
mandibular excursive movements.

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only accurate position that can be used on a
nonadjustable articulator is one specific oclusal
contact position.

Advantages:
1.
2.
3.

Inexpensive.
Less time required to mount the casts.
No procedures are required to mount casts.

Disadvantages:
1.
2.

Restorations cannot be properly planned.
Additional time is required to adjust the
restorations intraorally.


Semi adjustable articulators
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can be modified by adjustments made in the
condyle fossa portion of the instrument

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Allows more variability in duplicating
condylar movements.

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It usually has 3 types of adjustments
1.
2.
3.

Condylar inclination.
Lateral translation movement or Bennett angle.
Intercondylar distance.

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condylar inclination: angle at which the
condyle descends. can be altered

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Bennett angle: angle described by the orbiting
condyle during laterotrusive movements.
semiadjustable articulators allow for a Bennett
angle movement only in a straight line.

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Intercondylar distance: The distance between
the rotational centers of the condyles.Three
general settings - small, medium and large.

Records required
1.
2.
3.

Facebow transfer.
Centric relation interocclusal record.
Eccentric interocclusal records

Advantages:
1.
2.

The adaptability to patient’s specific condylar movement.
Accurately fitting restorations can be fabricated.

Disadvantages:
1.
2.
3.

Initially more time is required.
More expensive than nonadjustable type.
condylar path is in straight line, unlike the true condylar
path, which follows a curved path.

Fully adjustable articulators
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have a large range of adjustability in all three
dimensions
most complex types of articulators
most sophisticated type for recording
mandibular movements.
adjustments that can be made are
Condylar inclination.
2. Bennett angle.
3. Rotating condylar movement.
4. Intercondylar distance.
1.


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Condylar inclination:Angle during protrusive and
laterotrusive movements can be adjusted. capable of
recording curvature of patients condylar movements.

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Bennett angle: both bennett angle and bennett shift
can be recorded.

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Rotating condylar movement:pathway of the
rotating condyle duplicates that of the patient.

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Intercondylar distance: can be adjusted in a fully
adjustable articulator to match that in the patient more
precisely.

Records required:
1.
2.
3.

An exact hinge axis location.
A pantographic recording.
A centric relation interocclusal record.

Advantages:
1.
2.

Ability to duplicate mandibular movements precisely.
Stable and anatomic interocclusal relatioship can be
obtained.

Disadvantages:
1.
2.

Considerable amount of time is required.
Highly expensive. www.indiandentalacademy.com

INDICATIONS FOR ARTICULATOR
MOUNTED MODELS
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When a significant discrepancy exists between
RCP & ICP (> 2mm).
Orthodontic cases with multiple missing teeth.
Cases undergoing orthognathic procedures.
Mounting of study models pre orthodontic
treatment and pre debond in individuals with
TMD is recommended.


USES OF ARTICULATORS IN
ORTHODONTICS
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For diagnosis and treatment planning.
For finishing.
In orthognathic surgical cases.


IN DIAGNOSIS AND TREATMENT PLANNING
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Diagnosis carried out with teeth in ICP- misleading inappropriate treatment plan.
small proportion of patients have a large discrepancy
between RCP and ICP.
Such large discrepancies are not easy to diagnose
clinically.
may be necessary to deprogram the neuromusculature.
Articulated models reveal the AP relationship of
maxilla and mandible more accurately.
ease with the visualisation of static and functional
interrelationships of the teeth.

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can be used to aid the clinician whether selective
grinding can be undertaken.

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sectioning of the teeth and repositioning them in
wax - final results of orthodontics can be visualised.

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orthodontic setup provides valuable information for
treatment planning.

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Patients with hypodontia and multiple missing teeth
may not have a reproducible ICP. only reproducible
relationship that can be recorded is RCP-requires
articulator mounted models.

ARTICULATORS FOR FINISHING

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Non working side contacts are harmful to the
dentition - trigger bruxism, TMJ disorders or
instability of tooth position. Hence these
interferences have to be eliminated.


ARTICULATORS FOR
ORTHOGNATHIC PLANNING
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essential part of presurgical preparation

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ramus osteotomies - seperation of tooth bearing parts
of mandible from the condyle. no benefit in
maintaining condyle tooth relationship during model
surgery and hence an arbitrary mounting is sufficient.

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maxillary surgery, autorotation of the mandible will
be necessary - the condyle tooth relationship should
be recorded as precisely as possible.

MANDIBULAR POSITION INDICATOR
Dynamic and static positions of mandible
determined by:
1.
2.
3.
4.

5.

6.

neuromuscular system and proprioceptivity.
morphology of hard and soft structures of the TMJ.
The morphology of the occlusal surfaces of the teeth.
Compromises necessitated by various skeletal
patterns.
Head posture and its relationship to the cervical
spine.
The limits of motion established by ligaments
attached to the mandible.

MANDIBULAR POSITION INDICATOR
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The M.P.I. quantifies differences between RCP &
ICP.

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used to perceive whether a clinically determined
symptom or sign can be related to differences
between the patient's RCP and ICP, if early signs of
discopathy are present, and if a treatment plan to
move the teeth will result in an occlusion in which
RCP and ICP are compatible.

MOUNTING OF CASTS

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Accurate impressions

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Stone casts


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Base of casts –
Split cast former


Anatomic facebow oriented to soft tissue porion and orbitale.

Face bow record transferred to articulator


Recording centric relation

Mandible guided into retral
position by the
operator(guided by the
thumb and forefinger at
gnathion)


Roth power centric


Anterior segment- 3
thickness wax. Caninecanine.

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Posterior segement – 2
thickness wax. Molar
region.

Roth power centric technique


M.P.I PROCEDURE
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Adhesive grid paper- on
incisal table
Upper member lowered to
first contact
Incisal pin lowered
Grid mark – red marking
Vertical height of pin
noted.

maxillary cast is transferred
to the M.P.I.
M.P.I and upper part of the
SAM 2 articulator are
identical, except condylar
housing are replaced with
sliding blocks in the M.P.I




Mounted maxillary
cast is interdigitated
with mandibular cast



Adhesive grids with
X, Z coordinates are
placed on the lateral
sliding blocks of the
M.P.I.

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Adhesive grid on black
cubes of MPI

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Mark position of
condylar spheres with
black articulating paper
(hinge axis position)


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Incisal pin vertical reading –
Delta H

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Horizontal difference between
RCP &ICP read at incisal
table - Delta L

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Dial gauge reading – Delta Y

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Cubes slid medially to
perforate grid.



Point of perforation
indicates hinge axis.


Results
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Delta H = vertical increase or decrease read from
the incisal pin.
Delta L = protrusive or retrusive movement
measured from tne incisal table (grid)
Delta X = protrusive or retrusive. Indicates
differences in horizontal condylar position.
Delta Z = compression or distraction. Indicates
differences in vertical condylar position.
Delta Y = right or left transverse movement.
Indicates differences in transverse condylar
position.

ICP (black dot) below
RCP (red dot)
indicates distraction.

ICP (black dot) above
RCP (red dot) indicates
compression.


ELECTRONIC MPI


displays data that are the same as those taken
manually with the M.P.I. Standard records are
designated numerically as the differences between:
1. RCP and the intercuspal position (ICP)
2. RCP and bilateral joint resilience (RES)
3. RCP and estimated therapeutic position (ETP)
4. RCP and ideal vertical position (IVP)
5. RCP and forced bite position (FBP)
6. ICP and a new ICP after full-mouth opening

AXIOGRAPHY
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Axiograph - diagnostic instrument- simulates
condylar movement pathways.
The procedure is called AXIOGRAPHY. The
graphic output is called AXIOGRAM.
Records movements in all 3 planes of space.
Early detection of subclinical discopathies.




Reference planehinge axis.



Normal joint

The axiograph
simultaneously
records hinge-axis
movements in all 3
planes.

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Facebow of
axiograph
attached to
cranium.

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Hinge-axis bow
anchored to the
mandible with
functional
occlusion clutch.

Tracing of hinge axis movement

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Three dimensional recording as
stylus is replaced by dial gauge.



Deranged joint- location and repeatability of a
reference position is impossible.



Difficulty to locate hinge axis may be due to
1.
2.
3.
4.
5.
6.

Flattened condylar head.
Inflammation
Internal derangement.
Loose ligaments.
Structural asymmetries
Muscle imbalance.

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Movements traced are
1.
2.
3.

4.

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protrusion-retrusion,
opening-closing,
unguided mediotrusion-medioretrusion, right
and then left;
guided mediotrusion-medioretrusion, right and
then left.

Joint sounds – crepitation and clicking should
be recorded.

Bennett movement




Mediolateral movement of
the mandible measured
along the Y axis.
Bennett value altered by
1.
Medially displaced
meniscus
2.
Luxation
3.
Subluxation.
4.
Reduction.

Resiliency test


Determines the ability to move the hinge-axis position
superiorly anteriorly to a loaded position



Children -1mm of resiliency, young adult .5mm, and
middle-aged or elderly patients .3mm.



No joint resiliency- results in deroundation - flattening
of the condyle head. Resiliency below normal requires
treatment with splints.


Joint resiliency test
Upward pressure
 Condyle displaced
superiorly &
anteriorly



Interpretation of Axiograpic
Tracings
Sagittal movements


Coincide for first 1012mm



Bilaterally symmetrical



No Bennett movement.
(0.2-0.3 mm acceptable)


Sagittal movements
When movements do
not coincide
1.
2.

3.

Muscle limitation
Differentiate between
muscular and
ligamentous limtation.
Correlate with clinical
findings.


Protrusion – retrusion tracings

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

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

Normally coincide in pattern and timing
Position altered by loose ligaments.
Asymmetry in timing seen due to in coordination
of medial and lateral pterygoids.
Limited movement seen in class II div II
No transverse deviation of bennett movement –
deviation indicates incipient discopathy.


Mediotrusion – Medioretrusion






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principally a unilateral translation, with minimal
vertical movement.
The condyle head rotates minimally within the
inferior concavity of meniscus.
If tracings do not coincide - indicative of loose
ligaments, subluxation, luxation, or reduction.
Medially displaced meniscus restricts
movement.

Opening/closing movements
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




Opening movement involves the rotational
component of the mandible - is extremely
important in diagnosing morphological changes
in the head of the condyle.
Comparisons between rotational and translatory
movements are paramount to a proper diagnosis.
Rotational movements- lower joint abnormalities
Translatory movements- upper joint
abnormalities.

Overrotation of mandible


Deroundation of condyle


Muscle distraction


Highly active temporalis


Loose joint


Functional distraction


COMPUTER AIDED AXIOGRAPHY




enhances the tracking of hinge-axis
movements in all 3 planes along with timing of
movement and accuracy.
computer displays the condylar movement in
real time.


Locating hinge axis







Located by having the patient rotate open,
without translation, for at least 10mm- If the
stilus is not on the hinge-axis position it will
scribe an arc.
uses this arc to form a circle and then calculates
its center, which is the site of pure rotation— the
true hinge-axis.
Accuracy of location- 0.01mm
Accuracy of manual method – 0.2 mm

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Tmj instrumentation /certified fixed orthodontic courses by Indian dental academy

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