01- Occlusion in prosthodontics introduction -5th year

Dr. Amal Fathy Kaddah
Prof. of Prosthodontic,
Faculty of Dentistry,
Cairo University

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1. The stomatognathic system
2. What 'occlusion' is and why occlusion is important
3. Definitions.
4. The significance of 'ideal occlusion‘
5. Difference between natural and artificial Occ.
6. Mandibular Movements.
7. Articulators and Facebows.
8. Balanced Occlusion and Factors affecting Balanced O.
9. Concepts of occlusion (Balanced and Non balanced Occlusion).
10. Recording of Occlusion for removable prosthodontics.
11. Occlusal correction for Removable Prosthesis.
12. Occlusion and implant restorations (Loading protocols)
Occlusion Outline

It is an important factor for maintaining
the stability of complete dentures, with
the least amount of trauma to the
supporting tissues.

 Enhancement of denture stability,
retention and support.
 Preservation of the remaining tissues.
 Proper masticatory efficiency.
 Enhancement of phonetics and esthetics.
Objectives

Philosophies of Denture Occlusion
• Many philosophies of arranging
denture occlusion
• No definitive scientific studies
prove one occlusal scheme clearly
superior.

Stomagnathic System
• The movement of the jaw is orchestrated OR
organized by a very complex set of muscles,
which are in turn controlled by the body's
local and central nervous system
Stoma= mouth
Gnathion = jaws

The stomatognathic system
= the masticatory
system =
• Teeth
• Periodontium
• Jaws
• TMJ
• Associated muscles +
tongue & ms of the soft
palate
• Investing tissues
• Neural control

Muscles of Mastication:
Neuro Muscular System
Masseter
Temporalis
Lateral Pterygoid
Medial Pterygoid
Tempromandibular
Sphenomandibular
Stylomandibular
TMJ Capsule
Associated Ligaments

 Elevation of mandible (closes the jaw)
to close the mouth, Forceful jaw closing.
Masseter
Temporalis
 Elevation of the mandible (closes the jaw)
 Assist in Retrusion of mandible
 No activity when mandible is elevated very slowly.
 Assist in protrusion of mandible
• Elevation of the mandible (closes the jaw)
• Minor contribution to protrusion of the mandible
• Right medial pterygoid with left lateral pterygoid turn the chin to left side
Medial Pterygoid
Wikipedia

• Protrusion of the mandible: The primary function of the
lateral pterygoid muscle is to pull the head of the condyle out of
the mandibular fossa along the articular eminence to protrude the
mandible.
• Jaw opening (Depresses the mandible) it is assisted by
the digastric, mylohyoid and geniohyoid muscles..
• SIDE TO SIDE movements GRINDING MOVEMENT
• Unilateral action of a lateral pterygoid produces contralateral excursion (a
form of mastication), usually performed in concert with the medial
pterygoids.
Lateral Pterygoid
Wikipedia

The combined efforts of the Digastrics and Lateral
Pterygoids provide for natural jaw opening
Digastric muscles is not a muscle of
mastication but it play an important role in
mandibular function

In the edentulous patients, use the posterior border
position at the accepted VD
(Centric occluding relation)

Centric Occlusion made to coincide
with CR

To occlude means to “close”.
•Occlusion is the act or process of closure

The static relationship between the incising or
masticating surfaces of the maxillary and mandibular
teeth, after jaw movement has stopped and tooth
contacts are identified.

The contact relationship
between the occlusal surfaces
of teeth during function.
It is the DYNAMIC contacts relationship of the
teeth as the mandible moved to and from
eccentric relation.

EXCURSIVE MOVEMENT
Movement occurring when mandible moves
away from maximum intercuspation
OCCLUSAL INTERFERENCES
Undesirable contacts occurring
during lateral movements

Working side
Non working (balancing) side
That side of the mandible that
moves toward the median line in
a lateral excursion.
The side toward which the
mandible moves in a lateral
excursion

The most retruded relation of the mandible to the maxillae when
the condyles are in the most posterior unstrained position in the
glenoid fossae from which lateral movement can be made,
(within hinge movement).

The relation of the mandible to
the maxilla with the mandible in
its most retruded position.
(GPT) 2005

Dawson has defined this position as the
rearmost, uppermost, midmost (RUM)
position of the condyle in the fossa at
which the medial pole of the condyle disc
assembly is braced against the bony wall
of the eminentia.

Whatever is the definition of centric relation it is reproducible,
stable and functional position.
The rearmost, uppermost, midmost (RUM)
position of the condyle in the fossa
the most posterior unstrained position in
the glenoid fossae
in the uppermost and rearmost
position in the glenoid fossae
in the anterior-superior position
against the articular eminences

Is the only constant repeatable
position within the functional limit to
start constructing a stable occlusion

The complete intercuspation
of the opposing teeth
independent
of condylar position
GPT8

Maximum Intercuspation:
It is the most closed complete interdigitation of
mandibular and maxillary teeth irrespective of condylar
centricity.

The occlusion of opposing teeth
when the mandible is in centric
relation, This may or may not
coincide with the centric
relation in natural dentition
GPT 9

• In 90% of individuals with full complement
of natural teeth, centric occlusion
(maximum intercuspation), does not
coincide with centric relation of the jaws.
• In most patients centric occlusion is
located anterior to the centric relation by
0.5-1.5 mm measured in the horizontal
plane.

An occlusion other than centric occlusion
Protrusive occlusion
Lateral occlusion

Protrusive occlusion Lateral occlusion
the occlusal contact
relationship that exists
when the mandible is
moved forward
the occlusal contact
relationship that exists when
the mandible is carried
laterally

Centric occlusion with teeth
present is a tooth to tooth relation
whereas centric relation, is a
bone to bone relation
(Static positions)

In complete denture prosthodontics the
relation of the mandible to the maxilla
should be recorded in the most retruded
position (C.R) with the position of the
maximum planned intercuspation of
teeth (centric occlusion) established to
coincide with it.

It is a term used describe an occlusal design that
permits free non interfering gliding of the mandible
from centric relation to centric occlusion.

VERTICAL DIMENSION OF OCCLUSION
• The distance measured between two selected anatomic or
marked points (usually one on the tip of the nose and the
other one on the chin) when occluding members are in
maximal intercuspation. GPT 9

The degree of separation between the
maxillae and the mandible when the
teeth are in centric occlusion.
VERTICAL DIMENSION OF OCCLUSION

Inter-alveolar distance
inter-ridge distance
• The vertical distance between
specified positions on the
maxillary and mandibular
alveolar ridges at the occlusal
vertical dimension.
• Checked on mounting diagnostic casts

The vertical dimension of the face when the mandible
is in rest position.
VERTICAL DIMENSION OF REST

Interocclusal distance
(Free way space)
• The space between the
maxillary and mandibular
occlusal surfaces when the
mandible is in the rest position.
it ranges from 2-4 mm.

V D R
V D O
V D R - F W S = V D O
2 to 4 mm.

This relation exists when the
jaws are in centric relation and
the teeth are in centric occlusion

Three - dimensional record,
Vertical relation,
Antero - posterior relation
and lateral relation,
i.e. to obtain a centric relation record
it is necessary to determine the
vertical dimension of occlusion.

In the edentulous patients, use the
posterior border position (centric
relation) which is repeatable,
reproducible and within the
functional range of movements

For this reason, the relation of the
mandible to the maxilla should be
recorded in the most retruded
position (C.R) and centric
occlusion made to coincide with it

In the edentulous patients, use the
posterior border position (c. relation)

Centric Occlusion made to
coincide with CR

Long centric or Freedom in centric
The occlusal surface of the teeth could be
altered to allow freedom of tooth movement in
harmony with the rotation of condyle. (from
hinge position to habitual intercuspal position).

Anterior Contacts in “old” MI and
CRO after Correction
long centric or Freedom in centric

= Balance + Occlusion
• BALANCE = When forces act on a body in
such a way that no motion results, there is
balance or equilibrium.
• OCCLUSION = Relationship between the
occlusal surface of the maxillary and
mandibular teeth when they are in contact.

State of equilibrium of the
denture bases in relation to their
supporting structure
when the opposing teeth contact.

The simultaneous contacting of the maxillary and
mandibular teeth on the right and left side and in
the posterior and anterior occlusal areas in
centric and eccentric positions, developed to limit
tipping of the denture bases in relation to the
supporting structures”- (GPT 5)

• The dynamic movements
of the teeth in relation to
each other
Articulation:

Stable simultaneous contact of the
opposing upper and lower teeth in centric
relation position with a continuous smooth
bilateral gliding from this position to any
eccentric position within the normal range
of mandibular function

Balanced
Occlusion/Articulation
•The Bilateral simultaneous contact
of the anterior and posterior teeth
in excursive movements. (GPT 9)

•There should be no interferences during
movement from centric position to
eccentric positions.
•The movements should be in harmony
with TMJ & neuromuscular control

• The natural Teeth are retained by
periodontal tissues, which are uniquely
innervated and structured. When the
natural teeth are lost, not only the
occlusion is lost but also the attachments.
• In complete artificial occlusion, all
the teeth are on two bases seated on
slippery tissues.
Differences between natural and artificial occlusion
Regarding retention and stability

In the natural teeth, proprioception gives guidance
to the neuromuscular control during function.

With artificial occlusion, no such signal
system is present, and the mandible
returns at the end of the chewing stroke to
its optimum power position which, is
centric relation. If cusps interfere or if
there are premature occlusal contacts, the
bases shift to accommodate them.

 The natural teeth move
independently and can
immigrate slowly to unfavorable
occluding positions.
• The artificial teeth move as a unit and are
instantly displaced by dislodging forces.
Regarding retention and stability

In Natural Occlusion In Artificial Occlusion
Tooth contact on one side of the
arch does not directly affect
retention and stability of teeth on
the other side of the arch as each
tooth is anchored independently to
its bony alveolus.
Tooth contact on one side of the
arch affects retention and stability of
teeth on the other side of the arch as
each artificial teeth are attached to
the same denture base that rests on
compressible mucosa.

Incising in the anterior
region of natural teeth
does not affect the
posterior teeth but it does so in
artificial dentitions.
Regarding eccentric balance

Christensen’s phenomenon
• A gap occurring in the natural
dentition or between the opposing
posterior flat occlusal rims when the
mandible is protruded.
• It can lead to instability in full
dentures unless compensating
curves are incorporated into the
dentures.

• This occlusion could cause
tipping of the denture in the
posterior region.
• Thus simultaneous anterior
& posterior contacts are
required when mandible is
protruded.

Means that when the patient produce a protrusion
with well adapted occlusal rims, there will be a v-
shaped gap between the rims in the molar region.
Sagittal Christensen phenomenon

Means that when the patient
produce a lateral excursion with
well adapted occlusal rims, there
will be a v- shaped gap between
the rims in the molar region on the
balance side. On the working side
there will be contact between the
upper and the lower rims.
The Transversal Christensen phenomenon

*Differences between
condylar and Incisal Angles
are usually well tolerated.
*Incisal angle should be
less or equal to condylar
angle to avoid interference
of teeth during mandibular
excursions.
In Natural Occlusion In Artificial Occlusion

In natural teeth, there is rarely,
bilateral balance during
nonfunctional excursions,
whereas in artificial teeth, it is
necessary to stabilize the bases.
Regarding bilateral balance

Bilateral balance in artificial teeth,
is necessary to stabilize the bases.

. A malocclusion of natural teeth may
be uneventful for several years and if
symptoms do occur, they are usually
localized to the involved tooth or
teeth.
• A malocclusion of artificial Teeth
creates an immediate response and
usually involves a large area of the
supporting tissues.
Regarding bilateral balance

Mastication in the second
molar region in the artificial
occlusion shifts the base if it
is on an inclined foundation,
• whereas, in natural teeth, it
is one of the power points of
mastication.

Types of posterior teeth
1- Anatomic teeth
2- Modified or semi-anatomic
tooth
3- Non-anatomic tooth

Denture Occlusion Options
Anatomic
Semi-anatomic
Lingualized
(lingual contact)
Non-anatomic
(balancing ramp)
Non-
anatomic

1- Anatomic teeth
• Simulate the natural tooth form.
• It has cusp height of varying degrees of
inclination that will intercuspate with an
opposing tooth of anatomic form.
• The standard anatomic tooth has inclines
of approximately 33o .

It is measured by the
angle formed by the
mesiobuccal cuspal
incline to the horizontal
plan when the long axis
of the tooth is vertical to
the plane
Cusp Angle

The palatal cusps of
the maxillary
posterior teeth and the
buccal cusps of the
mandibular
SUPPORTING CUSPS
Centric Cusps – (Stamp Cusps)
posterior teeth.

Non-Centric Cusps
The buccal cusps of the
maxillary posterior teeth
and the lingual cusps of the
mandibular posterior teeth.
Help to determine the path of the supporting cusps
during lateral and protrusive movements.
Non-centric Cusps – (Guiding Cusps)

Problems with anatomic teeth
1- The presence of cusp inclines can cause
trauma, discomfort and instability to the
bases because of the horizontal
component of force that produced
during function.

2- The use of adjustable articulator is mandatory
3- Various eccentric records must be made for
articulator adjustments
4- Harmonious balanced occlusion is lost when
settling occurs
5- The bases need prompt and frequent relining to
keep the occlusion stable and balanced.

6- Mesiodistal interlocking will not permit
settling of the base without horizontal
force developing. That acting on thin
delicate mucosa and the underlying bone
creates shearing that are not well
tolerated

Sharp cusped teeth exert less vertical force for
penetration but produce more lateral force owing to the
inclined plane effect (horizontal component of force).
Flat teeth exert more vertical force but produce less
lateral force components

Problems with non-anatomic tooth
1- Do not function efficiently unless the
occlusal surface provides cutting ridges and
spillways
2- They can not be corrected by occlusal
grinding without impairing their efficiency.
3- Appear dull and unnatural.

Selection of tooth forms is based on
1- The capacity of the ridges
2- Interridge distance
3- The ridge relationship

4. Esthetics.
5. Patient's age and neuromuscular
coordination.
6. Previous denture-wearing experience.

Strong well-formed
resist horizontal force
1- The capacity of the ridges

A large interridge distance creates a long
lever arm through which horizontal forces
created by the inclines of cusps can act.
Therefore, this force can be controlled by
using flat teeth as the interridge distance
increases.
2- Interridge distance

Non-anatomic posterior teeth used
effectively to control the forces of
occlusion and to stabilize the denture
base supported by compromised weak
ridge in either class II or class III
ridge relationship
3- The ridge relationship

I- Concepts Of Occlusion In Centric
Position
a. Concepts of balanced occlusion
II- Concepts Of Occlusion In Eccentric
Position:
b. Concepts of non-balanced occlusion

•The Bilateral simultaneous
contact of the anterior and
posterior teeth in excursive
movements. (GPT 9)
Balanced

State of equilibrium of the denture bases
in relation to their supporting structure
when the opposing teeth contact and
there is a resultant force.
Balanced

•There should be no interferences
during movement from centric
position to eccentric positions.
•The movements should be in harmony
with TMJ & neuromuscular control

Balanced Occlusion is important to:
Prevent the denture movement during chewing,
produce efficient mastication and in turn help in
stabilizing the denture

Types of Balance as Related
to Complete Denture
1) Lever balance
2) Occlusal balance

1- Lever balance
Dependent on
tooth position as
related to its base

Greater the lever balance by
favorable tooth denture
relationship Greater the
stability of the base during
mastication until the teeth
contact.

Lever balance and the greater
the stability of the base.
1. The larger ridge.
2. The closer the teeth to ridge.
3. The more lingualized occlusion.
4. The more centered the force of occlusion
antero- posteriorly

The better the Lever
balance the greater the
stability of the denture
base during mastication
until teeth contact.
1- Favorable tooth- to -ridge crest position
Inter bolus exit balance is compensated by lever
balance

Equilibrium of the base on its supporting
structures when a bolus of food is interposed
between the teeth on one side and a space
exist between the teeth on the opposite side

a- The height of occlusal plane should be 1-2 mm. below the lip line.
Aesthetic base.
Leverage action
Functional base
2- Determination of the height
of the occlusal plane

b- The occlusal surface of the teeth should be below the
greatest convexity of the tongue. This also improves the
stability of lower denture.

Convenient and at a
level familiar to the
tongue to perform its
action easily and stop
food escaping to the
floor of the mouth.
The height of occlusal plane should be

The tongue brings the food onto the occlusal plane, then
it holds the food between the upper and lower teeth by
cooperating with the buccinator muscle so that the
food can easily crushed. The food is held between the
bucc. (its middle fibres) and the tongue, and crushed.
Chewing

C- Leverage action: The nearer the occlusal
plane to the basal bone of the jaws, the less
the leverage action and the better the
stability.

Unilateral lever balance
Equilibrium of the base on its
supporting structures when a bolus of
food is interposed between the teeth
on one side and a space exist between
the teeth on the opposite side

1. Placing the teeth over the ridge.
2. Denture base area covers as wide area
on the ridge as possible.
3. Placing the teeth as close to the ridge
as other factors will permit.
4. Using as narrow a buccolingual width
occlusal food table.
To achieve the unilateral lever balance

2- Occlusal balance
It depends on
teeth contact

2- Occlusal balance
1) Unilateral occlusal balance (Group function) This is
not followed for balanced occlusion of complete denture It is
more pertained to fixed partial dentures
2) Bilateral occlusal balance
3) Protrusive occlusal balance
4) Mutually protected occlusion
(Canine protected) This is not followed for complete denture

The group function concept
.
It requires teeth on the
working side to be in
contact in lateral excursion
simultaneously with a
smooth, uninterrupted glide
and teeth on the non-
working side are free of any
contact.
1- Unilateral occlusal balance
This is not followed during
complete denture
construction. It is more
pertained to fixed partial d.

Bilateral simultaneous occlusal contact of teeth,
anteriorly and posteriorly, in both centric and
eccentric positions.
Gliding of the teeth across each other during their
movement from one position to another, without
any interferences.
2- Bilateral occlusal balance

The objective of occlusal balance is to
create bilateral contacts from the centric
position to all eccentric position, that are
free from interference, smooth, uniform and
in harmony with movement of the mandible

Bilateral balance in artificial teeth, is
necessary to stabilize the bases.
Centric occlusion
Balanced
eccentric
occlusion

3- Protrusive occlusal balance
• This type of balanced occlusion is present when
mandible moves in a forward direction and the occlusal
contacts are smooth and simultaneous anteriorly and
posteriorly.

 There should be at least 3 points
of contact on the occlusal plane
Two located posteriorly and one
anteriorly.
 The more the number of contacts
the better will be the balance.
 Absent in natural dentition.
3- Protrusive occlusal balance

4- Mutually Protected Occlusion
• Also called canine protected occlusion
• Anterior teeth overlap prevents the posterior teeth from
making any contact on either the working or the nonworking
sides during mandibular excursions.
• Anterior teeth bear all the load and the posterior teeth are
dis-occluded during excursions. Protecting the posterior teeth
• In CO, posterior teeth direct forces through their long axis
and anterior teeth are slightly in or out of contact. Protecting
the anterior teeth.

When the patient moves to the side during chewing, there are only
one or two tooth contacts, and then the denture bases will tip up
and be very difficult to control. If they do not tip because the ridges
and/or the patient’s muscle control prevent this, they will create
pain, discomfort, and ulceration.

1- Provide maximum denture stability during
functional and parafunctional movements of the
mandible
2- Help in distribution of the masticatory pressure
over the supporting tissues and reduce trauma to
the underlying tissues
3- Increased efficiency of mastication
4- Psychologically it is more comfortable to the
patients when eccentric balance is present

01- Occlusion in prosthodontics introduction -5th year

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01- Occlusion in prosthodontics introduction -5th year