Occlusion seminar

Presented by-
Dr Anisha Sinha(PG II)
(BASIC CONCEPT)

• INTRODUCTION
• BASIC TERMINOLOGIES
 Centric relation
 Maximum Intercuspation
 Anterior Guidance
• TYPES OF OCCLUSION
 Dawson’s Classification
 Canine protected Occlusion
 Group Function Occlusion
 Balanced Occlusion
• GENERAL DESCRIPTION
 Tooth alignment and dental arches
 Anterior-posterior inter arch relationship
 Inter arch tooth relationship
2

• GENERAL DESCRIPTION
 Posterior cusp characteristics
 Supporting and non supporting cusp
 Types and directions of mandibular movements
 Posselt’s envelope of motion
 Mechanism of mandibular motion
 Bennett Movement
• CLINICAL CONSIDERATIONS
 Role of contact, contours and marginal ridges
 Occlusal interferences
 Occlusal examination
 Treatment Planning
• CONCLUSION
• REFERENCES
3

DEFINITION:
• Occlusion literally means “closing”;
• Def - The contact of teeth in opposing dental arches when the jaws are closed (static occlusal relationships) and
during various jaw movements (dynamic occlusal relationships).
- Sturdevant’s,7th edition
• Repeated attempts have been made to describe an ideal occlusal scheme, but these descriptions are so
restrictive that few individuals can be found to it the criteria.
• Carlsson et al, concluded that “in final analysis, optimal function & the absence of disease is the principal
characteristic of a good occlusion”
4

6
Centric relation –
Centric relation is defined as a
maxillomandibular relationship independent of
tooth contact, in which the condyles articulate
in the anteriorsuperior position against the
posterior slopes of the articular eminences;
In this position the mandible is restricted to a
purely rotary movement; from this unstrained,
physiologic, maxillomandibular relationship, the
patient can make vertical, lateral or protrusive
movements; it is a clinically useful, repeatable
reference position GPT-9 (2017)

• It is the universally accepted jaw position because it is physiologically and
biomechanically correct and is the only jaw position that permits an
interference-free occlusion.
• Because the position of the condyle-disk assemblies determines the
maxillary-mandibular relationship during jaw closure, any variation in condylar
position will change the closing arc of the mandible teeth against the maxillary
teeth.
• The mandible is in centric relation if five criterias are fulfilled:
1. The disk is properly aligned on both condyles.
2. The condyle-disk assemblies are at the highest point possible against the
posterior slopes of the eminence.
3. The medial pole of each condyle-disk assembly is braced by bone.
4. The inferior lateral pterygoid muscles have released contraction and are passive.
5. The TMJs can accept firm compressive loading with no signs of tenderness or
tension.
Journal of Interdisciplinary Dentistry / May-Aug 2012 / Vol-2 / Issue-2
7

PROCEDURE- BILATERAL MANIPULATION
1. Recline the patient all the
way back
8
Bimanual manipulation, as made most notable by Dr. Peter Dawson, can
be quite frustrating for many clinicians because it takes time to learn how to
perform properly. This technique requires you as the clinician to seat the
condyles in the fossa by stretching the lateral pterygoid

2.Head stabilisation
9
3. Stretch the neck by lifting the patient’s chin.

5.Bring the thumbs together to form ‘C’ with each hand
10
4. Place the four fingers on the lower border of the
mandible

7. After the mandible feels like it is hinging freely and
condyles seem to be fully seated in their fossas,most
experienced clinicians assume that mandible is in centric
relation.
11
6.With the very gentle touch ,manipulatethe jaw ,so it
slowly hinges open and closed:
• As it hinges,the mandible will usually slips up into
centric relation ,if no pressure is applied.

Criterias for accuracy in making an interocclusal bite record
12
 The bite record must not cause any movement of teeth or displacement of 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 casts.
 he bite record must not distort during storage or transportation to the laboratory.
It should be possible to fulfill all five requirements for accuracy by proper
selection of one of the techniques described below.

Wax bite record:
13
 Most popular
 Wax used-(Delar wax) Thick at front.

Sturdevant’s 7th edition
15
 Maximum intercuspation (MI) refers to the position
of the mandible when teeth are brought into full
interdigitation with the maximal number of teeth
contacting.
 Synonyms for MI include intercuspal contact,
maximum closure, and maximum habitual
intercuspation (MHI).
 Earlier, this position was called as centric
occlusion. The MIP might not coincide with the
centric relation and that is why the terminology
centric occlusion is obsolete.

16
• According to Dawson, anterior guidance is the
dynamic relationship of the lower anterior teeth
against the upper anterior teeth through all the ranges
of function.
• In simple words Anterior guidance is a feature
where the front teeth ensure that the back teeth don't
contact when the jaw is slid forward.
• It plays a very important role in protecting the
posterior teeth from protrusive and lateral stresses by
discluding effect.
• An unfavourable anterior guidance contributes to
anterior alveolar bone loss and teeth mobility when
there are susceptible periodontal tissues and
excessive forces

18
Dawson's classification:
 In the analysis of any occlusion in relation to the TMJs, the condition and position of the
TMJs must be determined before the occlusion can be analyzed.
 Type I: Maximal intercuspation is in harmony with centric relation.
 Type IA: Maximal intercuspation occurs in harmony with adapted centric posture.
 Type II: Condyles must displace from a verifiable centric relation for maximum
intercuspation to occur.
 Type II-A: Condyles must displace from an adapted centric posture for maximum
intercuspation to occur.
 Type III: Centric relation cannot be verified.
 Type IV: The occlusal relationship is in active stage of progressive disorder because of
pathologically unstable TMJs.

Implications for Type I
• Centric relation is verifiable with the teeth separated.
• There is no discomfort in the TMJ region even when
firmly loaded.
• Treatment for TMD is not needed.
• The jaw can close to maximal intercuspation without
premature tooth contacts or deflections.
• Occlusal equilibration is not needed except for possible
excursive interferences.
• The patient can clench with no sign of discomfort.
• Use of an occlusal splint is not indicated.
• Type I occlusion can occur with any Angle's classification. 19
Type-1(

A signifies adapted condition.
Implications for Type IA
• Intracapsular structures have deformation but have
adapted.
• TMJs can accept loading with no discomfort.
• Treatment for TMD is not needed.
• Occlusal correction is not needed because there is no
TMJ/occlusion disharmony.
20
Type-1A(

21
Type-2
• The source of pain will be in muscle or in
interfering tooth .
• The occlusal therapy goal is to achieve
Type I or IA .

Treatment may be reversible with use of an
occlusal splint, or it may be direct using
equilibration, orthodontics, or restoration to
correct the TMJ/occlusion disharmony.
22
Type-2A

23
• TMJ‟s cannot accept loading without
tenderness
• Focus should be on correcting the TMD
before occlusal treatment can be finalised.
• The occlusal therapy goal is to achieve
Type I or IA
Type-3

24
Type-4
• Actively progressive disorder of the TMJ’s
Signs :
• progressive anterior open bite progressive
asymmetry progressive mandibular
retrusion.
• The goal is to stop the progression of the
TMJ’s deformation.

25
• Group function occlusion:
 Group function is defined as multiple contact relations
between the maxillary and mandibular teeth in lateral
movements on the working side whereby simultaneous
contact on several teeth acts as a group to distribute
occlusal forces.
• The group function occlusion can be seen in patients whose
canines were worn away or are missing, thus allowing the
posterior teeth to come in contact during lateral movements
of the mandible.
• The advantage of group function occlusion is that the
occlusal forces are shared among several teeth.

26
• Canine protected occlusion:
 The Glossary of Prosthodontic Terms5 defines canine guidance as
a form of mutually protected occlusion in which the vertical and
horizontal overlap of the canine teeth disengage the posterior teeth
in the excursive movements of the mandible.
 Accordingly, when the mandible moves to one side, the overlap of
canines results in separation (disclusion) of posterior teeth on the
working side.
 Canine guidance is more commonly seen in young patients whose
canines are not worn.
 It also be created by adding restorative material (such as
composite ) when a posterior fixed prosthesis or implant-retained
fixed prosthesis is planned in order to protect it

27
• Balanced occlusion:
• It indicates simultaneous occlusal contacts of the
upper and lower teeth on the right and left side
of the jaw, in the anterior and posterior regions
when the mandible is in MIP, and during
excursive movements.
 It is a prosthetic term used to stabilise the
denture during function.
 It is not applicable for normal dentitions and
therefore should be avoided..

• On the left side of the arches, an
imaginary arc connecting the row of
facial cusps in the mandibular arch have
been drawn and labeled facial occlusal
line.
• Above that, an imaginary line
connecting the maxillary central fossae
is labeled central fossa occlusal line.
• The mandibular facial occlusal line and
the maxillary central fossa occlusal line
coincide exactly when the mandibular
arch is fully closed into the maxillary
arch
29
Sturdevant’s, 7th edition

The cusp interdigitation pattern of the first molar teeth is used to classify anteroposterior arch
relationships using a system developed by Angle.
30

31
• In normal Class I occlusion, the mandibular
facial cusp contacts the maxillary premolar
mesial marginal ridge and the maxillary
premolar lingual cusp contacts the mandibular
distal marginal ridge. Because only one
antagonist is contacted, this is termed tooth-
to-tooth relationship.
• The most stable relationship results from the
contact of the supporting cusp tips against the
two marginal ridges, termed a tooth-to-two-
tooth contact.
• In Class II occlusion, each supporting cusp tip
will occlude in a stable relationship with the
opposing mesial or distal fossa; this
relationship is a cusp fossa contact.

ADD A FOOTER 32
 The outer incline of a cusp faces
the facial (or the lingual) surface
of the tooth and is named for its
respective surface.
 The facial cusp ridge of the facial
cusp is indicated by the line that
points to the outer incline of the
cusp.
 The inner inclines of the posterior
cusps face the central fossa or
the central groove of the tooth.

33
 The inner incline cusp ridges are
widest at the base and become
narrower as they approach the cusp
tip.
 For this reason, they are termed
triangular ridges.
 Mesial and distal cusp ridges extend
from the cusp tip mesially and distally
and are named for their directions.

34

Functional cusp features:
1. Contact opposing tooth in MI
2. Support vertical dimension
3. Nearer faciolingual center of tooth
than nonsupporting cusps
4. Outer incline has potential for
contact
5. More rounded than nonsupporting
cusps
35

Non functional cusp features:
1. Do not contact opposing tooth in
MI
2. Keep soft tissue of tongue or
cheek off occlusal table
3. Farther from faciolingual center of
tooth than supporting cusps
4. Outer incline has no potential for
contact
5. Have sharper cusp ridges than
supporting cusps
36

37

ADD A FOOTER 38

ADD A FOOTER 39
Lateral movement(Left) is forward translation of
right condyle &rotation of left condyle
Translation(> 25mm) is the bodily movement of
an object from one place to another.
Simultaneous, direct anterior movement of both
condyles, or mandibular forward thrusting, is
termed protrusion
Complex motion combines rotation and
translation in a single movement. Most
mandibular movement during speech, chewing,
and swallowing consists of both rotation and
translation

 Posselt's envelope is first described by Dr Ulf Posselt in 1952.
 He gave combination of border movements in all the three plane.
 Posselt postulated that in the first 20mm of opening and closing,
the mandible only rotates and does not simultaneously move
downward and forward
42

46
• It is defined as “the bodily lateral movement/
lateral shift of mandible resulting from
movements of condyles along lateral inclines
of mandibular fossa during lateral jaw
movement” Dr Norman Bennett
• the angle formed between the sagittal plane
and the average path of advancing condyle
as viewed in the horizontal plane during
lateral mandibular movements.

47
 The Bennett movement, or lateral shift of the mandible, is of paramount importance in
operative and restorative dentistry, as it is this movement that determines the position and
form of the cusps.
 Since it is the movement which causes the teeth to glide laterally across each other, its
influence can be very destructive.
 If the teeth are flat, the greater the Bennett movement, the greater the friction as the flat
surfaces glide over each other, with resulting lateral stresses on supporting structures.
 If the teeth have cusps, they must have correct position and form to harmonize with this
lateral shift, otherwise the cusps will bump instead of gliding around each other as they
should.

51
• Role of contact areas
• A break in continuity of the line of contact areas throws additional
responsibility on the PDL & alveolar bone.
• Creating a contact that is too broad, bucco-lingually or occluso-gingivally in
addition to changing the tooth anatomy will change the anatomy of the inter
dental col.
• The broadened contact produces an inter-dental area that the patient is less
able to clean i.e. increases the area susceptible to future decay.
• Creating a contact that is too narrow bucco-lingually or occluso-gingivally
leads to greater susceptibility for microbial plaque accumulation &
predisposes to the periodontal and caries problems.

52
• Role of contour:
• All tooth crowns exhibit contours in the form of convexities and concavities
which should be reproduced in a restoration.
• The concavities occlusal to the height of contour, whether they occur on
anterior or posterior teeth are involved in the occlusal static and dynamic
relations as they determine the pathways for mandibular teeth into and out of
centric occlusion.
• Deficient or mislocated concavities will lead to premature contacts during
mandibular movements, which could inhibit the physiologic capabilities of
these movements.
• Excessive concavities can invite extrusion, rotation or tilting of occluding
cuspal elements into non-physiologic relations with opposing teeth.

53
• Role of Marginal ridges:
• A marginal ridge should always be formed in two planes buccolingually,
meeting at a very obtuse angle.
• This feature is essential when an opposing functional cusp occludes with
the marginal ridge.
• A marginal ridge with these specifications is essential for;
1. The balance of the teeth in the arch.
2. Prevention of food impaction proximally.
3. Protection of the periodontium.
4. Prevention of recurrent and contact decay.
5. For helping in efficient mastication.

• Interferences are undesirable occlusal contacts that may produce mandibular
deviation during closure to maximum intercuspation or may hinder smooth passage
to and from the intercuspal position.
• As for example ,a non-working side occlusal contact may be present during lateral
mandibular guiding excursion,but it is not necessarily denoted as an interference;
therefore it’s correction is not mandatory.
• However,it is important to avoid incorporation of occlusal interferences as a result
of new restorationby a careful clinical and laboratory examination, before and after
cementation of restoration.
54

 Centric interferences
 Working interferences
 Non-working interferences
 Protrusive interferences 55
Types of interferences

 Indicates the first tooth contact on the arc
of rotation on envelope of mandibular
movement when MIP does not coincide
with the Centric relation.
 It can be differentiated into two types:
• Interferences in the arc of closure
• Interferences in the line of closure 56
Centric relation interferences

• As the condyles rotate on their terminal hinge axis, each lower tooth follow an arc of
closure.
• Primary interferences that deviate the condyle forward produce the “anterior slide”.
• May trigger bruxism
57
Interference To The Arc Of Closure

• It refers to those interferences that cause the mandible to deviate to the left or
right from the first point of contact to the most closed position
58
Interference To The Line Of Closure

59
Why to adjust interferences in CR first??
By adjusting the
centric interferences
first, you have the
option of improving
cusp-tip position
Occlusal grinding is
more evenly
distributed to both
arches
Eccentric interferences
can be eliminated with
speed and simplicity

• This occurs on the side towards which the mandible is
moving.
• When such contact occurs, it hinders smooth
harmonised mandibular movements and separates the
other teeth of the working side
• As an example, this type of occlusal interference may
occur between the outer inclines of the maxillary
supporting cusps and the inner inclines of the
mandibular guiding cusps 60
Working-side interferences

• Non-working side interference is an undesirable
contact of the opposing occlusal surfaces on the non-
working side.
• It usually occurs between the inner incline of the
supporting cusps of opposing teeth and discludes
other teeth
61
Non-working side interferences

• Protrusive interference occurs between the
mesial inclines of the mandibular posterior teeth
and the distal inclines of the maxillary posterior
teeth during mandibular protrusive movement.
• It causes separation (disclusion)of the anterior
teeth during this movement. It may also cause
locking of the mandible
• The rule for eliminating protrusive interferences
is DUML grind the distal inclines of the upper or
the mesial inclines of the lower. 62
Protrusive interferences

• If the interference incline causes deviation towards the cheek, grind the
buccal incline of the upper or lingual incline of the lower or both. (BULL)
• If the interfering incline causes deviation towards tongue, grind the lingual
incline of the upper or buccal incline of the lower, or both the inclines.
(LUBL)
63
Selective Grinding

• Rule 1: Narrow stamp cusps before reshaping fossae
• Rule 2: Don’t shorten a stamp cusp.
• Rule 3: Adjust Centric Interferences first
• Rule 4: Eliminate all posterior inclined contacts, preserve cusp tips only
64
Grinding Rules

• Stable stops on all teeth when the condyles are in centric relation.
• Anterior guidance in harmony with the border movement of the envelope of
function.
• Disocclusion of all posterior teeth in protrusive movements.
• Disocclusion of all posterior teeth in nonworking side Non-interference of all
posterior teeth on working side, with either the lateral anterior guidance or the
border movements of the condyle.
• In lateral movements, supporting cusps preferably should have slight freedom in
centric and occlude in a valley like space on opposing teeth (in grooves or
embrasures), to facilitate non interfering passage of cusps. During protrusive
movements, there should not be any tooth contact posteriorly.
65
Requirements For Occlusal Stability:

• Reduction of all contacting tooth surfaces that interfere with the
completely seated condylar position i.e., centric relation .
• Selective reduction of tooth structure that interferes with lateral excursions
• Elimination of the posterior tooth structure that interferes with protrusive
excursions.
• Harmonization of the anterior guidance
66
Occlusal equiliberation:

• Clench test : Clenching the tooth together & squeezing firmly.
• Reasons for discomfort : incomplete elimination of occlusal
interferences on the posterior teeth
67
Verification Of Completion

68
Computer Assisted Dynamic Occlusal Analysis:
T-SCAN
• Developed by Maness.
• Sensor Unit that records
occlusal contacts on a thin
mylar film and relays the
information to a computer.

Assessment tool used to evaluate the occlusion of a patient
69

• Wafer-thin, with the ability to
withstand 15-25 closures
• High resolution Sensels™ for
precise data
• Reusable on a single patient
(Cold sterilize between visits)
70

Occlusal force distribution using T-Scan III, Software
version 8.0.1. Three-dimensional images of a healthy
participant
71

Customizable arch for accurate representation of the patient's specific arches saves
time and allows dentist to easier correlate the data to the mouth 72

 Before initiating treatment the clinician must decide whether to
provide restorations. within the existing occlusal scheme or to
change it.
 Confirmative approach is defined as the provision of
restorations in harmony with the existing jaw relationships.
 It is the principle of providing a new restoration that does not
alter the patients occlusion.
 Majority of restorations follow this principle. 73
Confirmatory approach:

 When considering the provision of simple restorative dentistry to the
conformative approach, no matter what type of occlusal restoration is being
provided the sequence is always the same –
 THE ‘EDEC PRINCIPLE’
.
 The EDEC Principle is useful in relation to:
- Direct restorations
- Indirect restorations
74
E-EXAMINE
D-DESIGN
E-EXECUTE
C-CHECK

75
The ‘EDEC’ Principle For Direct Restorations:
1.Examine:
 Examine static and dynamic occlusion.
 Mark them preoperatively.
 Malpositioned opposing supporting cusps, ridges or fossae may be
recountoured in order to achieve optimal occlusal contacts.
 Plunger cusps and over erupted teeth are to be reduced.
 In anterior restorations, the scheme of incisal guidance must be
examined properly.
 Assessment of periodontal condition must be made.

76
2. Design:
 Visualize the design of cavity
 Existing occlusal marks will either be preserved by being
avoided in the preparation, or they will be involved in the
design, but never end preparation margins at these points.

77
3.Execution:
 Controlled interproximal cutting and care in restoring axial tooth contour to avoid
overcontouring is essential.
 Carving of restoration must be harmonious to occlusion and should not produce
premature contacts.
4. Check :
 Check the occlusion by either reversing the color of paper or foils used pre-
operatively and using the preoperative marks as a refrence

78
The ‘EDEC’ Principle For Indirect Restorations:
 The dentist not only has to examine the occlusion in Indirect
restorations but the results of that examination have to be
accurately recorded and that record has to be transferred to the
technician.

79
1.Examine:
 The examination of the patient‟s pre-existing occlusion is carried out in exactly the
same way as described for the direct restoration.
 There is a need for this information to be transferred accurately to the laboratory
technician; hence a record must be made.
 The methods of recording interocclusal records include:
 Two dimensional bite records – Intra oral photographs, written records, and/or
Occlusal Sketching
 Three dimensional bite records – Bite registration materials such as hard wax, acrylic
resin, elastomers etc
 A combination of both.

80
2.Design:
 Clinically the cavity preparation is designed in exactly the same way
as for a direct restoration.
 The fundamental difference is that , the technician is going to make
the restoration. .

81
3.Execute:
 From an occlusal point of view one of the most significant
considerations is the provision of a temporary restoration which
duplicates the patient's occlusion and is going to maintain it for the
duration of the laboratory phase.
 For this the temporary restoration should: be a good fit, so that it is
not going to move on the tooth; provide the correct occlusion, so that
the prepared tooth maintains its relationships; be in the same spatial
relationship with adjacent and opposing teeth. .

82
4.Check:
 The occlusion of the restoration should be as ideal as possible
(preferably not on an incline) and should not prevent all the other
teeth from touching in exactly the same way as they did before.
 This needs to be checked before and after cementation

 Occlusion is fundamental to the practice of dentistry, in providing a
biologically functional restoration and for comprehensive patient
care.
 A dental restoration after being attached to the tooth becomes one
of the essential components of the stomatognathic system.
 Hence, any restoration (from intracoronal direct restoration to
complex crown and bridge work) must be planned to conform to the
existing occlusal pattern and not to disturb it 83

 WHEELER‟S Dental Anatomy, Physiology & Occlusion 7th edition
 PETER E. DAWSON Functional Occlusion
 STURDEVANT’S Art & Science of Operative Dentistry 5th edition
 M.A. MARZOUK Operative Dentistry modern theory and practice
 S J Davies et.al - Occlusion: Good occlusal practice in simple restorative dentistry.
British Dental Journal (2001) 191, 365 - 381
84

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