Physiologic tooth part 1

The Physiologic Tooth
Form Protecting The
Periodontium
By
Dr/ Rehab Rizk

Factors affecting the protective functional
forms of the tooth crowns

The Periodontium
Is the investing , supporting , attachment
and covering system of teeth.
It consists of:
Two Soft Tissues Two Hard Tissues
1- Gingiva
2- Periodontal Ligament
1- Cementum
2- Alveolar Bone

The protective functional forms of
the tooth crowns includes direct
factors and indirect factors :
The direct factors are:
1. Proximal contact areas.
2. Interproximal spaces.
3. Embrasures ( spillways ).
4. Facial and lingual contours of the crowns
5. Curvatures of the cervical lines.

1- Proximal contact areas:
DEF.
Contact areas :The crests of curvature on the proximal
surfaces of tooth crowns where the tooth touches the
adjacent tooth in the same arch.
Contours : Convexity on facial and lingual surfaces that
affords protection and stimulation of supporting tissues
during mastication.

Each tooth has two contact
areas one mesial and one
distal except third molars
1- Proximal contact
relation*When newly erupted, The teeth have a tight
pointed contact at their proximal maximal contour.
*This pointed contact is transformed into area of
contact by time due to continuous wear of the
proximal maximal contour of adjacent teeth .

To demonstrate the
position of this contact
areas
labiolingually or
buccolingually.
The contact areas must be observed from two
aspects in order to locate them:
The labial or buccal
aspect:
To demonstrate the
relative position of the
contact areas
cervico-incisally or cervico-
occlusally.
The incisal or occlusal
aspect:

The normal locations of the contact areas:
1. Contact areas become more cervically located from
anterior teeth to posterior teeth in each quadrant.

2. On individual tooth the distal contact area has a
more cervical location than the mesial contact area.

3. The relative size of the contact area increases from
anterior teeth to posterior teeth in each dental arch.

The normal locations of the contact
areas are as follow:
4. The anterior teeth have contact areas which are in
general, centered labio-lingually, while that of the
posterior teeth located slightly buccal to the center of
the bucco-lingual distance.

Note.
Diastema
is a space between two adjacent teeth that do not
contact each other.

1- Length &width of crown.
2- Proximal wear.
3- Malocclusion.
4- Developmental
anomalies.
5- Disproportional growth
between teeth and jaw.
6-Extraction, unerupted or
developmental missing
teeth.
Proximal contact relations are greatly influenced
by:

The proper contact between teeth in each arch is
important for:
1. Prevent food impaction between the teeth.
2. Stabilize the dental arches by the combined
anchorage of all the teeth in either arch in positive
contact with each other.
3. Protect the interdental gingiva.
4. Distribute the masticatory forces.
5. Food flow pattern

The absence of proper contact between teeth in
each arch is important for:
1. Food impaction between the teeth with consequent
gingival inflammation which if not treated leads to
destruction of the alveolar bone and loss of the tooth.
2. Separation of the tooth causes a change in teeth
alignment which in turn bring about shifting of the
forces of mastication to an angle that is not designed
for the tooth to withstand.

2- Inter Proximal spaces:
DEF.
• These are triangular spaces
between neighboring teeth which
are normally filled by gingival
tissues (interdental papillae). The
base of the triangle is the alveolar
process, the sides are the
interproximal surfaces of
contacting teeth and the apex of
the triangle is the contact point.
• The form of the interproximal
spaces depends on:
1. Teeth form.
2. Relative position of the contact
areas.

Physiologic role:
1. Create a proper spacing between
the teeth to contain the necessary
gingival tissues that are attached to
the bone and the teeth. This tissue
is a continuation of the gingiva
covering all the alveolar processes
that carries blood vessels and
nerve supply to all the investing
tissue.
2. Help in maintaining good oral
hygiene, where it prevents the
stasis of food about the teeth by its
elasticity, salivary secretion and
smoothness.

Physiologic role:
3. Since the teeth are narrower at the cervix mesiodistally than
at the occlusal surface and at the root outline is tapered toward
the apex, considerable spacing exists between the roots of one
tooth and its neighbors. Thus sufficient alveolar bone exists to
secure attachment of the teeth to the jaw. Also this provides the
vascular and nerve supply to all the investing tissues.

3. Embrasures or spillways:
It is an open space between
the proximal surfaces of
adjacent teeth in the same
dental arch. They diverge
from the contact area…
• Occlusally.
• Incisally.
• Buccally.
• Labially.
• Lingually.
• Cervically.
Note.
Cervical or gingival E.= Inter
proximal space

DEF.
• It is an open space between
the proximal surfaces of
adjacent teeth in the same
dental arch. They diverge
from the contact area…
• Occlusally.
• Incisally.
• Buccally.
• Labially.
• Lingually.
• Cervically.

I. Anterior teeth:
• Incisally:
Although the position of the contact areas in the anterior
teeth almost midway facio-lingually the lingual embrasure is
the bigger one. Why???????

I. Anterior teeth:
• Facially:
The size of the incisal embrasures increase in a distal
direction, while the opposite is with the cervical embrasures.
Why???????

3 -Embrasures or spillways:
II. Posterior teeth:
• Occlusally
•The position of the contact areas in
the posterior teeth are more buccally
SO the lingual embrasure is the
bigger one.

I. Posterior teeth:
• Facially:
The size of the occlusal
embrasures increase in a distal
direction, while the opposite is with
the cervical embrasures.
Why???????

Physiologic role:
1. It makes a spillway for the escape of food during mastication,
thus reduces the forces upon the teeth.
2. Makes the teeth self cleansing because the rounded smooth
surfaces of the crowns are more exposed to the cleansing
action of food, fluids and friction of the tongue, lips and
cheeks.
3. Normal embrasures and contact form protect the gingival
tissue from undue frictional trauma.
4. It allows proper stimulation by permitting the proper degree
of frictional massage during mastication.
5. Reduction of occlusal forces by decreasing the occlusal table.
6. In ant. Teeth it is a factor of esthetics.

2- The size of the incisal
embrasures increase in a distal
direction. ( )

Physiologic tooth part 1

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Physiologic tooth part 1