The document discusses occlusion in prosthodontics, detailing key concepts such as centric occlusion, centric relation, and mandibular movements related to dental function. It explains the anatomical and physiological relationships between maxilla and mandible, including movements during mastication and speech. Additionally, it outlines the roles of occlusal surfaces and muscle guidance in achieving harmonized dental function and addresses the implications for prosthodontic treatments.

1. Occlusion in prosthodontics
Dr. Razan Al Mghawich

2. Mandible to Maxilla relationships and
terminologies
 Centric occlusion (maximum intercuspation):
It is the most closed complete interdigitating of mandibular and maxillary
teeth (purely teeth guided) irrespective of condylar position or centricity.
 Centric relation (terminal hinge position)
maxillo-mandibular relationship in which the condyles articulate with the
thinnest avascular portion of the disk and being in the most anterior-superior
position against the articular eminencies, (its purely ligament guided
position).
 Rest position :
Purely Muscle-guided position when the mandible is at physiologic rest
without any tooth contacts, there will be a 1-3 mm space the freeway space
 Maximum opening : maximum separation between arches about 40-50 mm

3. Centric Relation of TMJ
• Its repetitive reproducible and recordable position
• Independent of presence and absence of teeth
• The final act of masticatory stroke ends in centric relation
• It is a border position and the posterior limit of the envelope of motion
• Can resist maximum loading by muscles with no sign of discomfort
• Note: maximum intercuspation may or may not coincide with centric occlusion
• if MI occurs with the condyles out of centricity, then both positions would not
coincide, the MI in this case, called habitual closure, and is considered as an
eccentric position

4. Vertical dimensions:
 Vertical dimension of occlusion (VDO): at maximum
intercuspation
 Vertical dimension of rest (VDR): at rest with freeway space
Plane of occlusion :
 refers to an imaginary surface that theoretically touches the
incisal edges of the incisors and the tips of the occluding
surfaces of the posterior teeth

5. Curves of occlusion:
 Two areas constitute the occlusal plane and should be addressed
separately.
 1- the anterior teeth, Their position is determined by:
 Esthetics
 demand for anterior guidance
 phonetic considerations.
 2- Posterior teeth, position is determined by two curves.
 curve of Spee
 curve of Wilson.

6. Curve of Spee
 The anterior/posterior curve of maxillary and mandibular
occlusal surfaces
 It is designed so that the posterior teeth can be separated in
protrusion, by the affects of condylar guidance and anterior
guidance. This phenomenon reduces posterior interference

7. Curve of Wilson
 “It is the mediolateral curve that contacts the buccal and
lingual cusp tips on each side of the arch
 it is always related to the lower arch
 Allows for the lingual cusps (working cusps) of maxillary teeth
to function with the lower occlusal scheme without
interference.

8. Mandibular
movements
TMJ and
articular
eminence
(posterior
guidance)
Occlusion curves
Teeth shapes &surfaces
Cusp heights
Central fossa
Marginal ridges
occlusal table
-Wilson
-Spee
Neuro-musculature
-masticatory muscles
--ligaments
PDL and perioception
occlusion
Teeth (anterior)
guidance:
-Anterior teeth
guidance
-Canine guidance
-Group function
Occlusal interrelationship
Mandible to maxilla
relation in 3 planes
mainly horizontal and
vertical

9. Mandibular movement :
 Mandibular movements are complex in nature.
 The mandible moves in relation to maxilla to perform many different
functional and parafunctional movements, they can be classified as
masticatory and non masticatory.
 The masticatory movements are necessary for introduction, grasping,
crushing, grinding of food, and swallowing.
 The non masticatory movements include the movements used in
speech, wetting the lips, mouth breathing as well as, habitual or
abnormal movements such as bruxing, clenching or tapping of teeth
together. The time spent each day for the non masticatory movements
exceeds the time used in masticatory movements
 the dentist must understand the factors that regulate motion of the jaws.
 These include contact of the opposing teeth, the anatomy and
physiology of the TMJ, the axes around which the mandible rotates the
action of the muscles, ligaments, and the neuromuscular integration of
all these factors.
 The dentist must relate an understanding of mandibular movements to
their clinical application in the treatment of patients, particularly the
edentulous.
 Any prosthodontic work should aim to restore this functions probably
with maximum imitation of the natural one

10. Mandibular movements
 Mandibular movements are usually classified
according to the main direction of movement. The
starting position is the maximum intercuspal position.
From this position the mandible can perform:
 Opening and closing
 Protrusive (forward )and retrusive ( backward)
movements
 Lateral movement (sideways-left & right)
 The mandible during its function moves in all the
three planes of space (horizontal, frontal, and
sagittal).
 Mandibular movement is controlled by the
Neuromuscular system with perioceptive receptors
 Influenced by two hard tissues that guide this
movement, they are referred to as guidance systems:
 Temporomandibular joints (the posterior guidance
system)
 Occlusal surfaces of teeth (the anterior guidance
system)

12. The guidance systems
 There are two systems that provide hard guidance during
mandibular movements; they are interrelated and part of one
system.
 Posterior guidance
 The temporomandibular joint ; made up of the head of the
condyle, articular eminence, the intra-articular disc and the
glenoid fossa
 The anterior guidance system
 is provided by which ever teeth naturally touch during
function to guide the mandible movements; happens during
dynamic occlusion or functional occlusion, and any other
contact that happens prematurely, or inhibits harmony is
referred to as Occlusal interference

13. Tempromandibular joint complex
 It is a synovial joint but differs from
most synovial joints in that the
articular surfaces of the bony
components are covered with
dense fibrous connective tissue,
instead of hyaline cartilage. In
addition, the TMJ has a fibrous
articular disc, to which muscle
fibers are attached. This disc
divides the joint into two
compartments, upper and lower,
thereby giving the mandible a wide
range of movement.

14. Muscles of Mastication
(Receive motor innervation for cranial nerve V-trigeminal SVE)
Derived from components of 1st branchial arch
MUSCLE ORIGIN INSERTION FUNCTION Excursive
movement
Masseter Zygomatic arch
Lateral surface of
ascending ramus
Elevates mandible
+ retrusion
ipsilateral
Temporalis Temporal bone
Coronoid process &
anterior border of
ascending ramus
Anterior fibers.-elevates
mandible
Posterior fibers-retrudes
mandible
ipsilateral
Medial Pterygoid
(Internal)
Medial surface of
lateral pterygoid
plate
Medial surface of
ascending ramus
Elevates mandible
Protrusion
contralateral
Lateral Pterygoid
(external)
Superior head
Greater wing of
sphenoid bone
Articular disc of TMJ
and neck of
mandibular condyle
Stabilizes mandible contralateral
Lateral Pterygoid
(external)
Inferior head
Lateral surface of
lateral pterygoid
plate
Anterior surface of
condylar neck
Depresses and protrudes
mandible
contralateral

15. Medial and lateral pterygoids

16. Temporalis &
Masseter

17. Mandibular ligaments

19. Mandibular movements:
 1. Opening and closing (depression and elevation
of the mandible):
 This movement starts from Intercuspal position to
the maximum opening position.
 At the beginning of the opening movement, rotation
in the lower compartment of the TMJ occurs for the
first 20- 25 millimeters of opening, can be
considered as a hinge movement. This movement is
mainly produced by gravity and the contraction of
the anterior belly of the digastric muscle.
 with further opening >25mm a gliding (translation)
movement occurs in the upper compartment. The
condyles usually start to translate immediately when
the teeth are separated from the intercuspal position
 For the closing movement, the mandible moves
from the maximum opening position with a reverse
movement back to the intercuspal position

20. Protrusive movement components
and guidance
 Its the anterior movement of the mandible
 Muscles: both left and lateral pterygoids contract simultaneously
 Condyle and posterior guidance : both left and right condyle heads rotate
openly initially, then translate forward and downward along the articular
eminence
-Depends on eminence steep
 incisors and anterior guidance : molars start to disarticulate with the lower
incisal edge of anterior teeth sliding along the lingual concavity of the upper
incisors, molar disarticulation reaches a maximum point at which the anterior
teeth are edge-to-edge
-Depend on :
-anterior teeth guidance and canines
-horizontal overjet
-vertical overbite
-cusp length of posterior teeth

23. Occlusal interrelationship
 Steeper eminence -- taller cusps
 Increased overbite--- taller cusps
 Increased overjet– shorter cusps
 Curve of Spee relation to this
 more curved shorter cusps Its curvature can be described in
terms of the length of the radius
 short radius the curve is more acute that with a longer radius

24. Lateral excursion movement:
 The working side : the side which the mandible moves towards
 The non-working side: the side which the mandible moves away from
 Muscles :contraction of
one lateral pterygoid on
the contralateral
(nonworking side)

25. Posterior guidance (condyles):
 The condyle at the side which the mandible is moving towards is called
the working condyle , it rotates forward and translates slightly lateral
 The slight lateral movement is immediate, non progressive and
described as ‘immediate side shift’, or ‘Bennet movement’.
 Its described in 86% of lateral movement and is about 0.5 to 3 mm
 The condyles at the side which the condyle is moving away from is called
the non working condyle, it rotates and translates along the eminence
forward, downward and medially
 The angle of the downward movement, known as the ‘condylar angle’
 The angle of the medial movement is known as the ‘Bennet angle’.
Bennet
angle
Bennet
shift
Direction of
movement
Working
Non-working

26.  Anterior guidance (teeth)for the lateral movement:
 The lateral movement has 2 types of guidance :
 Canine guidance : the sliding action contact between cusps of the
opposing canines on the working side disarticulate the teeth on the
non-working side
 If any other premature contact between any other teeth happens on
working and/or non-working side , is an interference
 Or Group function :
 The sliding contact between cusps of the opposing canines,
premolars, and molars on the working side; disarticulate all teeth on
the non-working side
 If any other contact on the non-working side only happens is an
interference

27. Intercondylar distance:
 Intercondylar distance or length of the back axis.
 It is the factor which has less significance in the lateral
movements
 because the variation in the width of the face among the
different patients is small (Dawson, 1991) and the difference
in the route of the cusps is not really important.

28. Relationship between anterior and
posterior controlling factors

29. Relationship between anterior and
posterior controlling factors

30. Posselt’s envelop of motion
 It is a diagram illustrates a combination of border movements of the
mandible in all 3 planes: Sagittal, Horizontal and Frontal
 Following a movement of a point on the condyle or a tooth
sagittal
horizontal
frontal

31. Chewing stroke
Anterior opening
border
Sagittal view

32. Horizontal view
 A: retruded contact
 B: maximum intercuspation
 C: edge-to-edge position
 D: maximum protrusion
 E: right lateral contact position
 F: left lateral contact position
F

33. Mutually Protected Occlusion
An occlusal scheme in which the anterior teeth protect the posterior teeth, and
vice versa.
 The anterior teeth protect the posterior teeth by providing guidance during
excursions
 thus allowing the cusps of the posterior teeth to disoclude rather than strike
one another during lateral or protrusive movements from centric relation;
 Because posterior crowns are so much wider and possess cuspal projections
in various configurations, they have an opportunity to bang into each other
during chewing, speech or simply meeting together when one bites down.
 To prevent this from happening, the anterior teeth of each arch will, ideally, be
situated so as to come into contact before the cusps of the posterior teeth do,
thus preventing wear on the posterior teeth. This requires less force because
the anterior teeth are further from the joint (analogous to stopping a door
further from its hinge).
 The posterior teeth protect the anterior teeth by providing a stable vertical
dimension of occlusion. While anterior teeth may retain their natural position
even after loss of posterior teeth, the masticatory forces will eventually cause
the single-rooted anterior to splay, thus leading to a collapsed bite

34. Balanced occlusion
 It’s a type of occlusion used in dentures and artificial teeth
 For lateral movement of the mandible
 When the mandible moves laterally all posterior teeth with
the canine on both sides ;the working and non-working
;contact, unlike functional guidance where contact on the
non-working side doesn’t happen
 Compensating curves:
 When artificial teeth have balanced occlusion the curvetures
of the teeth occlusal surfaces said to have compensation
curves; instead of curve of Spee and curve of Wilson

35. Reflexes and neural pathways
 The mandible is controlled not only as a result of voluntary movement, but also
by reflexes
 The jaw-closing reflex: protects the mandible and associated structures during
violent whole body movement; it can result in damage to the teeth, especially if
the occlusal contacts are not in the long axis of the root.
 The jaw opening reflex is to protect the teeth during sudden mastication of a hard
object and to protect the lips, cheeks and tongue during mastication.
 These voluntary and involuntary movements are controlled by the central and
autonomic nervous systems via sensory and motor nerves.
 specific proprioceptors are situated in deep muscle, and in the PDL
 As a consequence there is the potential for any change in patient’s occlusion, by
routine dentistry, to ‘be sensed’ by the patient’s nervous system. It is because of
this consideration that dentists cannot ignore the effect of changing the occlusion
when providing routine care.

36. Centric relation interocclusal
record
 Bimanual manipulation technique by dawson 2007

37. Anterior deprogramming devices
 Devices that can manipulate the mandible to seat the condyles in the
centric relation by deprogramming the perioceptive reflexes of the
muscles
 -leaf gauge
 -Lucia jig :acrylic resin jig with acu-flow material on it that sets on
45s

38. Materials used for inetrocclusal records
 Thermoplastic impression waxes and natural resins, ex: Aluwax®:
contains powdered aluminum; to increase the integrity of the
compound and provide the heat retention properties needed for
efficient modeling
 Fast setting elastomeric impression materials (polyether, polyvinyl
siloxane):
-Elastomer: is a polymer with viscoelasticity ,having both viscosity and
elasticity:( the tendency of solid materials to return to their original
shape after being deformed)