The document provides an introduction to occlusion, discussing important concepts like centric relation, temporomandibular joints, occlusion musculature, static and dynamic occlusion, and ideal occlusion. It emphasizes that the masticatory system, including teeth, periodontal tissues, and occlusion, form a interconnected system. Achieving and verifying centric relation is critical, as it provides the stable reference position for the occlusion. Multiple methods for determining and recording centric relation are described, highlighting the importance of bilateral manipulation and load testing to confirm the temporomandibular joints are fully seated and comfortable.

1. Introduction to Occlusion
Abdel Rahman M.A.
Demonstrator, Fixed prosthodontic department, Faculty of dental medicine, Al-Azhar
University, Cairo, Egypt.
Part 1

2. Content
• Analysis of Occlusion
• TMJ
• Occlusion Musculature
• Static Occlusion
• Dynamic Occlusion
• Ideal Occlusion
• Vertical Dimension

3. Why occlusion Is important in dental practice ?

4. • The masticatory system in general consists of three main
component: Teeth, periodontal tissues and occlusion or
articulatory system.
• When we say, “masticatory system," does this mean that this
system is a “true system”?
• is a “true system”? By going to the definition of 'system', we found
that it means ‘An assemblage that is connected or
interdependent, in order to form complicated unity ‘
PRINCIPLE
The ultimate goal for every patient should be maintainable health for the total
masticatory system.

5. • In other words, any system should have interrelated components,
which can’t act individually but with the aid of the other
components
• Back to the masticatory system we found that the changes in one
component necessarily affect the other components. Therefore,
the masticatory system: teeth, occlusion and periodontal tissues
are considered as a true system.

6. Goals of studying occlusion system
• Therefore, the first goal of studying occlusion system is to achieve the concept of
complete dentistry
• GOALS FOR COMPLETE DENTISTRY:
• Freedom from disease in all masticatory system structures
• Maintainable healthy periodontium
• Stable TMJs
• Stable occlusion
• Maintainable healthy teeth
• Comfortable function
• Optimum esthetics
PRINCIPLE
Whether general practitioner or specialist, practicing without a comprehensive understanding
of occlusal principles exacts a costly penalty in missed diagnoses, unpredictable treatment
results, and lost production time

7. Design of the masticatory system
PRINCIPLE
The design of the masticatory system requires balanced equilibrium
of all its parts.

9. Temporomandibular Joint
Peter E. Dawson
Principle
All occlusal analysis starts at the temporo mandibular
joints (TMJs).

10. TMJ Anatomy

11. The Articulating Surfaces

12. UNDERSTANDING CONDYLE DISK ALIGNMENT
• Medial and lateral distal ligaments • Posterior ligament

13. • Superior elastic stratum • Superior lateral pterygoid
muscle

14. HOW MUSCLE CONTROLS DISK ALIGNMENT
• Opening • Maximum opening

15. • Closing • Closed

16. THE TEMPOROMANDIBULAR LIGAMENT

17. THE ARTERIOVENOUS SHUNT.

18. • If the TMJs are not stable, the occlusion will not be stable, so it is
a risky proposition to undertake occlusal changes without knowing
the condition of the TMJs.

19. Neuro-muscular control
Principle
When bone and muscle war, muscle never loses.
“Harry Sicher”

20. Masticatory Musculature
• Muscles of mastication
• Masseter muscle
• Temporalis muscle
• Medial pterygoid muscle
• Lateral Pterygoid muscle.
• Supra hyoid muscles.
• Digastric muscle
• Mylohyoid muscle
• Geniohyoid muscle.

21. Coordinated muscle function during jaw
opening

22. Coordinated muscle function during jaw closure

23. Coordinated muscle function at maximum
intercuspation

24. Disharmony between the occlusion and the
TMJs

25. Incoordinated muscle function

26. Muscle Response to Occlusal Interference

27. Muscle Response to Posterior Disclusion
• At the moment of separation of the posterior
teeth, almost all of the elevator muscles shut
off. This has three beneficial effects:
 It greatly reduces the horizontal forces
against the anterior teeth, which are the
only teeth in contact during
excursions.
 It reduces the compressive loading forces on
the TMJs.
 It makes it impossible to overload or wear
the posterior teeth, even if the patient
bruxes.

28. Muscle Incoordination as a
Causative Factor in Disk Derangements
The ligament must be
stretched
The ligament must be
torn
The attachment of the
ligament must migrate.

29. Analysis of occlusion

30. Static occlusion
• Static occlusion refers to the position of teeth while the
mandible is static in position
whether teeth are present “centric occlusion”
or absent “centric relation”

31. Centric Occlusion
• Centric occlusion can be defined as the relation between
maxillary and mandibular teeth while the teeth are
contacting each other in maximum intercuspation, it’s
also called the inter cuspation position (ICP) or the
habitual bite.

32. Centric relation
• Centric relation is the relationship of the mandible to the
maxilla when the properly aligned condyle-disk assemblies are in
the most superior position against the eminentiae irrespective of
vertical dimension or tooth position.
“Peter E.Dawson”
• For better understanding Centric relation can be described in
three levels:
• Anatomically
• Conceptually
• Mechanically

33. • Anatomically
Centric relation describes the
relation of the mandible to the
maxilla when the disc
in its normal position, and the
condyle is in the most superior
‘upmost’ and most
anterior ’foremost’ position in
the glenoid fossa as stated by
Okeson’s AAOP
guidelines.

34. • Conceptually
it’s the position of the mandible in the
neutral zone between the elevator and
depressor muscles of the mandible.
The importance of this concept coming
from it gives an introduction to the
ideal occlusion at one level.
Peter E.Dawson

35. • Mechanically
Centric relation describes the part of mandibular movements around a
fixed axis.

36. What is the importance of centric relation ?

37. Does centric relation is the only relation that is
dependable in occlusion ?

38. • Centric relation is the accepted term for defining the condylar
axis position of intact, completely seated, properly aligned
condyle-disk assemblies. A TMJ that is structurally deformed
with a misaligned or displaced disk cannot be described as in
centric relation because it does not fulfill the critical
requirement of a properly aligned disk.

39. • Adapted centric posture is the manageably stable relationship
of the mandible to the maxilla that is achieved when deformed
TMJs have adapted to a degree that they can comfortably
accept firm loading when completely seated at the most
superior position against the eminentiae.

40. • The mandible is in adapted centric posture if five criteria are fulfilled:
1. The condyles are comfortably seated at the highest point against the
eminentiae.
2. The medial pole of each condyle is braced by bone. (The disk may be
partially interposed.)
3. The inferior lateral pterygoid muscles have released contraction and
are passive.
4. The condyle-to-fossa relationship is manageably stable.
5. Load testing produces no sign of tension or tenderness in either TMJ.

41. So
Where is the difference between the two positions?

42. • There is no difference in the procedure for determining either
centric relation or adapted centric posture. Both should be
confirmed by load testing to verify that the joint is completely
seated and the lateral pterygoid muscle is released.
• What is different is that a deformed joint that has adapted to a
comfortable capacity to accept loading is not as stable as an
intact TMJ. So patients should always be advised in advance of
any occlusal treatment that there will be a need for periodic
occlusal correction to maintain harmony with the changing
joint position.

43. Centric Freedom

44. Dynamic Occlusion.
• Dynamic occlusion is a term refer to any contacts between teeth
while the mandible is moving.
• The mandible has two guidance systems controlling its movement,
the posterior guidance
the anterior guidance.

45. Posterior guidance
• Posterior guidance is the controlled by the condylar system.
• The posterior guidance is not influenced by the presence or
absence of teeth. It’s affected only by the joint compartments.

46. • Working side.
• Non-Working side .
• Condylar path.
• Condylar angle.
• Bennit angle.
• Bennit movement.
• Working Condyle.
• Non- Working condyle.

47. Impact of posterior determinant on the
occlusal form of restorations
Posterior Determinant Variable Effect on restorations
Inclination of the articular
eminence
Steeper Posterior cusps must be taller
Flatter Posterior cusps must be
shorter
Medial wall of the glenoid
fossa
Allow more lateral translation Posterior cusp must be shorter
Allow less lateral translation Posterior cusp may be taller

48. Anterior guidance
• Wherever the mandibular movements are associated with occlusal
interference this is called “Anterior guidance”.
• No matter how far posteriorly the tooth is, it’s located anterior to
the condyle.
• anterior guidance became more ideally when occurring at the
most anterior teeth as far as possible anteriorly from the TMJ.

49. • Bilateral balanced occlusion .
• Group functional occlusion.
• Canine guidance or
canine protected occlusion.
• Working side interferences.
• Non-Working side interferences.

50. Ideal Occlusion

51. Ideal occlusion
• When defining the ideal occlusion we must consider the ideality at
variable levels. Ideal occlusion is defined for:
the tooth level,
the articulatory system level and
the patient level.

52. • The tooth level:
Multiple harmonious contacts
Simultaneous centric stop
 No cusp to cusp or cuspal incline contacts.
 Occlusal contacts directed toward the long axis of the teeth.
Smooth shallow guidance.

53. • The articulatory system level:
Centric occlusion occurs in centric relation.
Centric freedom.
No posterior interferences in protrusive and lateral movements.

54. • The patient level:
The ideal occlusion should fall within the neuromuscular tolerance
for the patient throughout life.

56. Introduction to Occlusion
Abdel Rahman M.A.
Demonstrator, Fixed prosthodontic department, Faculty of dental medicine, Al-Azhar
University, Cairo, Egypt.
Part 2

57. Content
• Some clarification about the centric relation.
• Vertical Dimension.
• Determining Centric Relation or Adapted centric posture.
• Verification of Centric Relation.
• Recording Centric Relation.

58. Some Clarification about Centric Relation
Principle
If a single concept must be learned about occlusion, that will be the
concept of centric relation.

59. 1
3
2
4
6
5

60. 1
2
3
4 5
7
6

61. Maximum intercuspation Centric relation

62. Remember that
• Centric Relation is a bony Not muscle braced position.
• Centric relation is a repeatable and reproducible. Why ?
• TMJ is a load bearing joint.
• In centric relation medial pole rotate while lateral pole translate.
• The inferior belly of the lateral pterygoid muscle is almost always
completely in active during clenching in the retrusive position.

63. Question:
Why the condyle doesn’t fit into concave disk as a perfect ball in
socket?

66. Determining centric relation or adapted
centric posture
Principle
determining centric relation is the single most
important procedure a dentist should learn.
Peter E.Dawson

67. • Although centric relation is a routinely used physiologic position,
it’s a mistake to use unguided closure to determine the correct
centric relation.
• This because in an unguided closure the patient has a tendency to
close toward the maximal inter cuspation position.
• That is the reason why the mandible should be manipulated to
close in centric relation.

68. Methods for determining centric relation:
• Bilateral manipulation
• Anterior bite stops
Directly fabricated Anterior deprogramming device
The panky jig
The best-bite appliance
The lucia jig.
NTI ( Nociceptive Trigeminal Inhibition)
Leaf Gauge

69. • Bilateral manipulation:
• Why use bilateral manipulation?
Kantor ME, Silverman SI, Garfinkel L. Centric-relation recording techniques--a comparative
investigation. J Prosthet Dent. 1972 Dec;28(6):593-600.

70. McKee JR. Comparing condylar position repeatability for standardized versus
nonstandardized methods of achieving centric relation. J Prosthet Dent. 1997
Mar;77(3):280-4.

71. • Bimanual manipulation is the most consistently accurate method
and the most repeatable as proved by studies.
• Bilateral manipulation is fast , uncomplicated.
• Bilateral manipulation provides a quick verification of:
1. The correctness of the position.
2. The alignment of the condyle-disk assembly.
3. The integrity of the articular surfaces.

72. Gilboe DB. Centric relation as the treatment position. J Prosthet Dent. 1983 Nov;50(5):685-9.

73. Procedure:
Step one: Recline the patient
all the way back Step two: Stabilize the head.

74. Step three: After the head is
stabilized, lift the patient’s chin
again to slightly stretch the neck.
Step four: Gently position the
four fingers of each hand on the
lower border of the mandible.

75. Step five: Bring the thumbs together to form a C
with each hand.

76. Ensure that the fingers are
properly positioned.
Step six: With a very gentle
touch, manipulate the jaw so it
slowly hinges open and closed.

77. OTHER METHODS FOR DETERMINING CENTRIC
RELATION OR ADAPTED CENTRIC POSTURE
• Anterior Bite Stops
• The value of anterior bite stops is primarily in their usefulness as muscle
deprogrammers. They do this by separating the posterior teeth so deflective
posterior interferences cannot influence the musculature to displace the
condyles.
• All of these appliances require a bite material for the posterior teeth after
centric relation has been achieved.

78. Types of Anterior Bite Stops
Directly Fabricated Anterior
Deprogramming Device
The Pankey Jig

79. The Best-bite Appliance The Lucia Jig

80. Leaf guage

81. • Disadvantages of anterior bite stop:
• Am improperly made anterior stop can displace the condyle distally.

83. Verification of Centric relation
Principle
If the temporomandibular joints (TMJs) are not completely
comfortable when firmly loaded, they are not in centric
relation.
Peter E.Dawson

84. • One of the most significant procedures in the diagnostic process is
the verification of centric relation through load testing of the TMJ.
WHY?

85. • Load testing is not only an essential step in the verification of
centric relation, it is a critical step in the differential diagnosis of
intracapsular TMJ disorders.
• One of the most practical uses for load testing is that it is a fast,
simple, and safe procedure for determining whether an
intracapsular structural disorder is or is not a source of orofacial
pain.

86. • To understand this concept we should re mention that: If the TMJs
are in centric relation, all forces go through avascular non
innervated structures, and the inferior lateral pterygoid muscles
have completely released their contraction.
--

87. • Orofacial pain can be the result of either:
• Occluso-muscle dysfunction.
• Intracapsular disorder.

88. Procedure:
• PROPER LOAD TESTING MUST BE DONE IN INCREMENTS.
Gentle Loading Moderate Loading Firm Loading

89. • Response to Gentle Loading can be a sign of:
• TMD.
• Muscle spasm.
Tip
Use the anterior deprogrammer to
differentiate between occluso muscle pain
and intra capsular disorder.

90. • Response to Moderate Loading in usually described in “tension” or
“ tenderness” and in most instanced is an indication of muscle
bracing rather than intra capsular disorder.
• Response to firm loading is most likely is a response to muscle
bracing.

91. Common Mistakes
• Applying too much pressure soon.
• Not applying enough upward loading forces

93. Recording Centric Relation
Principle
The price for inaccurate bite records is wasted time,
compromised results, and a lack of predictability.
Peter E.Dawson

94. • CRITERIA FOR ACCURACY:
The bite record must not cause any movement of teeth of displacement or
soft tissue.
It must be possible to verify the accuracy of the interocclusal record in the
mouth.
The bite record must fit the casts as accurately as it fits the mouth
It must be possible to verify the accuracy of the bite record on the cast
The bite record must not distort during storage or transportation to the lab.

95. • Causes of error in recording centric relation:
• Improper manipulation of the mandible.
• No verification of centric relation.
• Use of rubber material for recording the centric relation.
• Too deep indentation in the bite record.
• Use of soft waxes.
• Too shallow indentation.
• Use of unstable bite recording material.

96. Wax bite technique:

97. Anterior stop technique

98. Relating casts to the condylar axis
• There is very little, if any, value in studying unmounted casts,
because the primary purpose of analyzing diagnostic casts is to
observe tooth-to-tooth relationships in centric relation at the
correct vertical dimension.
• A correct axis allows changes in vertical dimension of occlusion
(VDO) up or down without displacement from centric relation.

99. • Since it would create a considerable error to open the jaw on one
hinge axis (for a bite record) and then close the casts on another
hinge axis (on the articulator), the condylar axis must be located
on the patient and transferred to the articulator. The facebow is
used for this purpose.

100. Face bow transfer

103. Vertical dimension
Principle
The repetitive contracted length of the elevator
muscles determines the vertical dimension of
occlusion.
“Peter E.Dawson”

104. UNDERSTANDING VERTICAL
DIMENSION
• There are four misconceptions about vertical dimension. You need to
know:
1. We determine vertical dimension based on whether the patient is
comfortable.
2. Measuring the freeway space is an accurate way to determine the
correct vertical dimension of occlusion (VDO).
3. Determining the rest position of the mandible is a key to
determining vertical dimension.
4. Lost vertical dimension is a cause of temporomandibular disorders
(TMDs).

105. If altering the VDO does not cause discomfort and does not cause
TMDs, why should we even be concerned about the VDO ?

106. • Answer: We should be concerned because failure to understand
the physiology and biomechanics of vertical dimension has led to
inappropriate overtreatment and has resulted in iatrogenic
damage to dentitions and missed diagnosis of TMD, and because
failure to understand the true nature of vertical dimension affects
a major amount of the decisions every dentist must make in
practice.

107. The key point to understand vertical
dimension
• The Key point to understand the concept of vertical dimension is to
understand that teeth continue to erupt through out life by the force of
passive eruption.
• This eruptive force continue until it meet resistance
• Usually this resistance coming from contacting the opposing dentition.
• The space through which the eruptive force cause the teeth and the
supporting alveolar bone to move with in it is gained and maintained by
the contracted length of the elevator muscle fibers.

108. Vertical dimension of occlusion (VDO)
• Is the vertical position of the mandible in relation to the maxilla
when the upper and lower teeth are intercuspated at the most
closed position.
• Even though the VDO occurs when the teeth are fully articulated,
the teeth are not the determinants of vertical dimension. Rather,
their position is determined by the vertical dimension of the space
available between the fixed maxilla and the muscle-positioned
mandible

109. • the vertical position of each tooth is adaptable to the space
provided, not vice versa, and that the capacity of the teeth to
erupt or intrude is present throughout life.
• even severe abrasion of teeth does not cause a loss of vertical
dimension.

110. Vertical dimension at rest (RVD)
• When a muscle is neither hypotonic nor hypertonic, it is said to be
“at rest.”
Fact:
The rest position is not consistent even in the same patient.
• Attempts to determine a consistent rest position have been
pursued using transcutaneous electrical nerve stimulation (TENS).

111. • However, The muscle contracted position is unrelated to any consistent
comparison with the resting musculature, regardless of how resting
length is determined.
• The practical approach is to concentrate on accurately recording the
VDO and allowing the dimensions of the freeway space to be the natural
result of the difference between the optimum length of contracted
muscles and the length of the muscles at rest.

112. Increase or not increase the Vertical dimension ?

113. • Any disharmony in the system provokes adaptive responses
designed to return the system to equilibrium. There is always
some price to pay for adaptation, and even though the adaptive
process may be beneficial, it is not always predictable.
• Adaptive responses to increased vertical dimension may simply
cause the lengthened teeth to intrude into the alveolar bone to
regain the original jaw-to jaw relationship, or there may be an
attempt to wear away the increased dimension by bruxing.

114. • and if the added compression of the supporting tissues exceeds their
capacity to remodel acceptably, we will see hypermobility of the teeth
and a lowered resistance in the periodontal structures.
• if it is not necessary, it is not advisable to disturb the equilibrium in the
first place.
• The goal of occlusal therapy is to minimize the requirements for
adaptation.
• Unnecessary increases in vertical dimension do the opposite. They
increase the requirements for adaptation, and once the adaptive process
is in accelerated activity, it is not always completely predictable.

115. WHEN THE VERTICAL DIMENSION
MUST BE CHANGED.
• There are some problems of occlusion that would be very difficult
to solve without increasing the vertical dimension.
Extremely worn occlusion ( Increase VD Vs perform multiple pulp
extirpation)
In some aesthetic cases ( increase VD Vs CLS ).
Some orthodontic treatment can’t be performed without temporarily
increase the VD

116. Do all changes in vertical dimension lead to eventual
problems in the dentition or its supporting structures?

117. • showed that adult orthodontic patients whose vertical dimension
had been increased up to 8 mm had reverted to their
pretreatment vertical dimension within one year. He also observed
that decreases in vertical dimension of up to 7 mm regained the
lost vertical dimension within one year!
McAndrews I: Presentation to Florida Prosthodontic Seminar, Miami, Florida 1984. Also
personal communication, 2001.

118. • There is more interesting findings regarding McAndrews
observations:
the change back to the original vertical dimension did not adversely affect
the corrected arch alignments or the intercuspal relationships.
changes in vertical dimension were the result of alveolar bone remodeling
was the observation that the cementoenamel junction of the teeth retained
the same relationship to the crest of bone.
• Of great significance in the McAndrews study is the attention paid
to achieving holding contacts for all teeth in centric relation.

119. Conclusion:
• What this study seem to indicate is that it is permissible to alter the
vertical dimension when necessary for achieving an improved occlusal
relationship as long as all teeth are properly intercuspated at a correct
centric relation.

120. Precaution:
• Before increasing any vertical dimension, one should evaluate the
alveolar bone. Dense sclerotic bone with numerous exostoses does
not have the same capacity to remodel as alveolar bone with
normal trabeculae. Increasing vertical dimension in such
unchangeable bone is contraindicated.