3. Complete denture occlusion Flashcards
Occlusion is
a dynamic concept describing
the integrated action of the components of
the masticatory system that control tooth
contact during function and dysfunction
The components of the masticatory system are:Teeth + periodontal ligament
TMJ + ligaments
Muscles of mastication
The components of the masticatory system are:
Teeth + periodontal ligament
TMJ + ligaments
Muscles of mastication
Parameters of jaw movement
(i.e. limit jaw movements)
- Muscles of mastication
- TMJ
- Teeth
Total range of mandibular movement can be represented by an maximum envelope of movement which is limited
by border positions and described by Posselt (1952)
Described commonly by trace of lower mid-incisal point
saggital plane movements -
ICP –
RCP –
RAC –
O –
P –
FWS –
RP –
ICP – intercuspal position
RCP – retruded contact position
RAC – retruded arc of closure
O – maximum opening
P – maximum protrusion
FWS – freeway space / IOD / IOS
RP – rest position
Mastication
an intermittent rhythmic act in which the tongue, facial
and jaw muscles act in coordination to position the food between the teeth,
cut it and prepare it for swallowing
Parafunctional activities:
clenching / grinding / lip+
cheek biting / thumb sucking /nail or object biting
Jaw movements in general
▪Mandible suspended from skull by muscles, ligaments
(TMJ/sphenomandibular/stylomandibular), vessels,
nerves, soft tissue
▪Moves in 3-D space: limited by muscles, TMJ, teeth
▪Basic movements vertical plane: open, close
lateral plane: right-side, left-side
antero-posterior plane: protrusion,
retrusion
▪Functional movement almost always a combination of
translation and rotation but may be purely rotational
Jaw movement in general
▪Mastication - an intermittent rhythmic act in which the tongue, facial
and jaw muscles act in coordination to position the food between the teeth,
cut it and prepare it for swallowing
▪Speech
▪Swallowing
▪Respiration
▪Emotional expression
▪Parafunctional activities: clenching / grinding / lip+
cheek biting / thumb sucking /nail or object biting
Natural dentition
… movement and retained by…
Fine neuromuscular control by proprioception from …
Independent movement and retained by periodontal ligament
p.lig. + TMJ,
MoM, tongue
Anterior incising involves
separation of the posterior teeth
Lateral excursions produce
working side contacts on canines or
premolars (or both) with separation of teeth on the non-working side
Most so-called ‘malocclusions’ of natural teeth i.e. posterior contact
during incision or non-working side contact
are of no pathological
consequence – but may cause problems if you produce them
when placing fillings/crowns/bridges/partial dentures
Terms : canine guidance, group function, posterior and
anterior disclusion, non-working side interferences – refer
Complete dentures
Prosthetic ‘plates’ with teeth which are easily displaced
during function.
Teeth all linked together via denture base and move as
such
Dependent on a so-called ‘balanced
occlusion/articulation’ for stability during tooth contact
Functional differences between Natural Dentition (ND) and Artificial
Dentition (AD)
- Stability: ND teeth are independent and
firmly attached to bone
AD united and rest on mucosa - Comfort: ND biting force greater (x5) than AD
as pain threshold of mucosa easily
exceeded - Chewing
efficiency: ND > AD, x6 number of chewing strokes
Real teeth don’t move, dentures do!
Not very comfortable
Not very efficient
Occlusion is based upon jaw relationships
The mandible has a three dimensional spatial
relationship with the maxilla and movement is
limited by – teeth, muscles and TMJ anatomy
* Any particular position has an antero-posterior
component, a vertical component, and a lateral
component
We need a start point to examine and assess and design occlusion for
any patient – dentate or edentate…? use what
If the intercuspal position (ICP), or centric occlusion, is deemed
acceptable we use that – the mandibular position that gives maximum
tooth contact
If ICP is deemed unacceptable or is non-existent we use the most
retruded position of the mandible (RCP)
Physiologic rest position or
Habitual position of mandible
The mandibular position assumed when the head is in
an upright unsupported position and the involved
muscles, esp. the elevator and depressor groups, are in
equilibrium in tonic contraction, and the condyles are
in a neutral, unstrained position.
Rest vertical dimension (or rest face height)
The vertical dimension of the lower face with the
mandible in the rest position.
Occlusal vertical dimension
(or occlusal face height)
The vertical dimension of the lower face with the
teeth in centric occlusion.
Interocclusal distance (Free Way Space / IOS)
(RVD – OVD) a range of 2-4mm at the incisors
Retruded arc of closure
The arc described by any point on the mandible during a closing
movement made with the condyles in their most posterior
positions. In this position the mandible rotates about the hinge
axis – an arbitrary line passing through the heads of the condyles
Retruded contact
The position of the mandible on the retruded arc of closure when
tooth (or rim) contact first occurs
Retruded contact position / retruded jaw
relationship / centric jaw relationship
The relation of the mandible to the maxilla with
the mandible in its most retruded position at a
prescribed occlusal vertical dimension
Occlusal scheme can affect:
- retention
- stability
- masticatory function
- occlusal force distribution
- aesthetics
- patient comfort
- general patient satisfaction with dentures
Occlusal scheme options
. Bilateral balanced articulation - the bilateral
simultaneous contact of teeth in RCP and during excursions
* Monoplane (non-anatomical) occlusion - ICP
and RCP correspond but no attempt to achieve contact in excursions
* Lingualised occlusion - where the maxillary palatal
(lingual) cusps articulate with the mandibular occlusal surfaces in RCP
and with the cuspal inclines in excursions (upper buccal cusps never
touch)
Balanced
articulation
teeth angle
advantages
disadvantages
balanced contact and what contacts?
Semi-anatomic
teeth (20-250 cusp
angle)
More efficient
chewing
Natural
appearance of
posteriors
Complex set up
Higher occlusal
forces generated
vertical and
lateral
Balanced contact
in RCP and
excursions
Buccal and lingual
cusps contact in
working side
excursions
Monoplane
teeth angle
advantages
disadvantages
balanced contact and what contacts?
0-degree non-
anatomic cuspless
teeth
Less efficient
Poor appearance
Easy set up
Less force
Balanced contact in
RCP only
Lingualised occlusion
Cusped uppers and
cuspless lower
posteriors
(specifically
manufactured for
purpose)
Some efficiency
Natural appearance
of uppers
Moderate set up
Less lateral force
? Good in resorbed
lowers
Balanced contact in
RCP and excursions
Maxillary palatal cusp only
contacts lower in
working side
excursions
Our occlusal scheme of choice for complete dentures is
a …. occlusal set up
‘bilateral balanced articulation’
In complete dentures …
For every other possible occlusal relationship there must be …
ICP must = RCP
bilateral or
anterior and posterior simultaneous contact
Balanced occlusion
a static relationship
The simultaneous even occlusal contact between maxillary and mandibular
teeth bilaterally or anteriorly-posteriorly
Balanced articulation
a dynamic relationship
The simultaneous bilateral, or anterior and posterior, occlusal contacts
between maxillary and mandibular teeth during the movement from one
balanced occlusion (i.e. during function) to another
Why do we want balanced articulation?
- It increases the efficiency of the dentures by making them more stable and free from tipping on unbalanced contact (retention, stability, masticatory
function, gen. satisfaction) - It distributes the occlusal load over the whole denture bearing area and this reduces the risk of alveolar trauma and resorption (occ. force distribution,
comfort) - It increases the patient’s confidence by making sure that the dentures are re-seated evenly if they become dislodged (stability, comfort, gen. satisfaction)
- Uses posterior teeth with cuspal anatomy (masticatory function, aesthetics)
How is balanced articulation achieved?
- Record the correct RCP relationship of the jaws and
transfer this to an articulator capable of reproducing that patients mandibular movements i.e at registration stage - By setting the teeth up in balanced articulation, using the factors governing balanced articulation, on the prescribed articulator (usually an average value articulator)
- Use and understand those factors (Hanau’s Quintet)
influencing tooth position to achieve a set up in balanced articulation
Contact during lateral movement
Working side, balancing side
Contact on protrusion
At least three widely separated points of occlusion must exist
Why record retruded contact position?
It is reproducible (because it is a border position)
- Patients easily accommodate to it (via
neuromuscular feedback from proprioceptors in TMJ,
muscles of mastication, denture bearing mucosa) - In order to set up a balanced articulation occlusion we
must record the most posterior position achievable as the average value articulator cannot reproduce ‘backwards’ movements
How do we get a balanced
articulation set up for our patients?
- Record RCP with registration rims
- Prescription to technician – “please provide
balanced articulation set up on an average
value articulator for try in” - Technician completes trial set up
- Clinician assesses trial set up on articulator
and in the mouth
Practical steps in obtaining a balanced articulation occlusal scheme
- Record blocks
- Average value articulator
- Factors of balanced articulation (Hanau’s Quintet)
- Factors of balanced articulation (Hanau’s Quintet)
- technician uses these to position teeth for occlusal set up to ensure balanced contacts
- Condylar guidance 300 / 350
- Incisal guidance 100 / 150
- Cuspal angles (height) 200 / 250: so-called semi-anatomic teeth
(00 = flat cusp teeth, 300 / 350 = anatomic teeth) - Plane of occlusion ala-tragal plane orientation +/-
- Compensating curves Spee / Wilson (change effective
cusp height)
- Average value articulator
Articulators are mechanical devices representing the temporo-mandibular joints, mandible and maxilla, to which such casts may be attached and observed in a
static and dynamic relationship. Their facility to duplicate mandibular positions and movements assists in diagnosis and treatments in the management of
patients.
Compensating curves
Posterior plane surfaces separate on protrusion (Christensen’s Phenomenon)
Need to introduce a curve to the occlusal plane antero-
posteriorly (and laterally) to maintain cuspal contact
during excursions
When the correct occlusal result
is achieved
- We have given the patient the best chance
for success (stable, comfortable and
effective dentures) regarding occlusion - This does not guarantee overall patient
satisfaction with dentures (success!)
