
The loss of teeth is the most common cause
of a physiologic occlusion developing into a
non-physiologic occlusion

In a healthy complete dentition, there is a an
equilibrium of forces from lips, cheeks,
tongue, neighboring teeth those help to
maintain a relative stability of individual teeth

The loss of a single tooth may lead to
drifting, tipping, rotation of neighboring
teeth, and extrusion of opposite teeth.

Tipping Rotation of a molar forward (mesially)
or backward (distally) around its body mass
axis called Center of Resistance


All the teeth are held securely in the jawbone.
With no adjacent support the neighboring
teeth begin to drift toward the area of the
missing tooth

Disease, decay or trauma may lead to tooth
loss. If a lost tooth is not immediately
replaced, the surrounding bone begins to
collapse and shrink

The amount of bone loss and the pattern of
drifting will vary depending on the individual
and the location of tooth loss.

The drifting of one tooth may lead to the
drifting of several teeth, resulting in a
significant amount of movement

Periodontal disease may begin to form after
the teeth have drifted and erupted
because
it becomes difficult to properly clean the
gums and reach all the pockets in those
areas. This may lead to tooth decay, receding
gums, and further tooth loss.
Some potential consequences:

1- Loss of mandibular first molar, meisal
tipping of the mandibular second and third
molars and the extrusion of the maxillary first
molar.




2-Loss of occlusal vertical dimension
3-Opening of proximal contacts
4-Uneven adjacent marginal ridges
5- Development of “Plunger” cusps


6-Food impaction
7-Lack of functional cleansing of teeth
These are less predictable because of
individual variations
Example:



Age and time of tooth loss
Periodontal conditions
Inter cuspation of the teeth adjacent to the
lost tooth and their antagonists

An epidemiologic study (Zarb et al ., 1978)
showed that 20% of patients with tooth loss
at an early age had subsequent closure of the
ensuing space.

Occlusal conditions leading to or resulting
from unilateral function represent significant
deviations from the criteria of the “ optimal
occlusion”
Byron : 1969
An optimal occlusion is characterized by –


Chewing performed with equal ease on both
sides
Bilateral stable occlusion contacts on most of
the teeth in the intercuspal position

Bilateral stable occlusal contacts on posterior
teeth in the retrusive range in the retruded
contact position and a small distance
between intercuspal position and retruded
contact position in the mid sagittal plane

Even though the ability to adapt with in the
masticatory system is great, the loss of even
a single tooth may lead to occlusal instability
and interferences with unfavorable
consequences for occlusal function, chewing
habits and oral hygiene

The more teeth are lost, the greater the risk
of tipping, migration, extrusion, and attrition
of remaining teeth and the loss of alveolar
bone and occlusal vertical dimension


The more depleted the periodontal support,
the greater the risk of trauma from occlusion
Teeth with markedly reduced periodontal
support, occlusal trauma will not cause
further destruction of the attachment
apparatus, provided the plaque induced
periodontal disease has been cured

The diverging options about the influence of
a reduced dentition on the masticatory
system prompted to perform a study on the
relationship between shortened dental arches
and oral function

The results showed two patters of change in
oral function.
1. Slow change until four occlusal units are left
and then rapid change
and
2. Progressive change without sudden change

It is probably more accurate to emphasis the
neuromuscular and functional sequelae of
loss of posterior teeth.

In some individuals posterior tooth loss is
well compensated by adaptive processes,
while in others it may contribute to functional
disturbances.
Natural Occlusion
(organic)
•
•
•
Bilateral Posterior
Centric Contact
Anterior Guidance
Mutually Protective
Scheme of Occlusion
Complete Denture
Occlusion
Complete denture
“dentition” also
presents in a variety
of forms, but also
exhibit certain
common
characteristics
Complete Denture
Occlusion
•
•
•
Bilateral centric contacts
Bilateral eccentric contacts
(balance) to provide
stability of the denture
bases during function
Non-balanced monoplane
occlusion
Complete Denture Occlusion
•
Because of compromises
inherent in restoring
the edentulous arch,
complete denture tooth
forms and arrangements
(i.e. occlusion), should
be designed to provide
function and aesthetics
while minimizing
denture base tipping
(lateral) forces
Fundamental differences of natural and
complete denture occlusion
1. Sensory feedback mechanism
2. Derivation of :
• retention
• stability
• support
3. Reaction of supporting structures to
masticatory forces
1. Sensory Feedback
Precision of feedback is significantly
compromised following loss of teeth and
associated structures (periodontal ligament)
2. Derivation of retention, stability and support
for natural occlusion
For natural dentition, retention, stability, and
support are derived through the periodontium
which provides;



Sensory feedback mechanism
Difference in reaction of supporting
structures to masticatory forces
Differences in load transfer mechanism and
physiology
Complete dentures receive their retention, stability, and
support from the soft tissues overlying residual bone
(ridges, buccal shelf, palate, etc.).
Denture Bearing Surface
•
Retention

Resistance to dislodgment forces in a
vertical direction away from the bearing
surface
Denture Bearing Surface
•
Stability
 Resistance to laterally oriented dislodgment forces
Denture Bearing Surface
•
Support

Factors of the Bearing Surface which resist
forces in a vertical direction towards the
bearing surface
3. Reaction of supporting structures
Natural occlusion
Physiologic levels of tension results in
alveolar bone apposition (such as that
transmitted by loading the periodontal
ligament through natural dentition)
Complete denture occlusion
Non-physiologic compression as may occur
under denture bases results in further
residual ridge resorption (RRR
Summary
Denture “Dentition”
Natural Dentition
•
•
•
•
•
•
•
Retained in PDL
Units move independently
Malocclusion effects not
immediate
Non-vertical forces affect
only teeth involved and
usually well tolerated
Incising doesn’t affect
posteriors
Bilateral balance is rare
Tactile sensitivity
•
•
•
•
•
•
•
Mobile bases on mucosa
Teeth move as an unit
Malocclusion affects entire
base immediately
Non-vertical forces affect all
teeth and are traumatic
Incising affects all teeth
attached to base
Bilateral balance is often
desired for base stability
Decreased tactile sense
A study conducted by Al-Shammari et al.,
(Journal of Periodontology 2005; 76(11); 1910 – 1918)
identified 9 major aspects that influence
the condition of tooth loss.
They are –
1.
2.
3.
4.
Age
Male gender
Smoking
Lack of
professional
maintenance.
5. Inadequate oral
hygiene
6. Diabetes Mellitus
7. Hyper tension
8. Rheumatoid
arthritis
9. Anterior tooth
type


Smoking and Tooth Loss:
Another study by M. Ojima et al (BMC Public
Health 2008) provide evidence regarding the
association between smoking and tooth loss
among adults aged 20-39


Smoking rates differed greatly in men (53.3%)
and women (15.5%).
The overall prevalence of tooth loss was
31.4% (31.8% men and 31.1% women).

Tooth loss occurred more frequently among
current smokers (40.6%) than former (23.1%)
and non-smokers (27.9%).
Tooth loss and Social behavior:

The loss of many teeth often reduces the
quality of life; embarrassment and selfconsciousness limit social interaction and
communication.
Tooth Loss and general Health:

Tooth loss is a significant problem related to
general health and the quality of life.

Because of chewing problems and decreased
masticatory function, a limitation in food
selection may occur, resulting in nutritionally
poor diets

Poor nutrition contributes to an increased risk
of several systemic diseases such as
cardiovascular diseases and hypertension.
F. Bodic et al., Joint Bone Spine
2005(72); 215-221

Alveolar bone play a key role in providing
support to the teeth, which are anchored to
the bone by desmodontal fibers.

Alveolar bone in the maxilla and mandible is
subjected to major local loads. This play the
leading role in maintaining local bone mass,
even in patients with osteoporosis.

There is a general agreement that the
presence of systemic bone disease influence
the rate of alveolar bone resorption after
tooth extraction.