The Physiologic Tooth Form Protecting The

Periodontium

By

Dr/ Rehab Rizk

ObjectivesFactors affecting the protective functional

forms of the tooth crowns

What is periodontium?????

The PeriodontiumIs 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 areascervico-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.

The normal locations of the contact areas:

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

The normal locations of the contact areas:

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.Diastemais 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.

2- Inter Proximal spaces: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.

2- Inter Proximal spaces:

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

3. Embrasures or spillways: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.

3. Embrasures or spillways: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???????

3. Embrasures or spillways: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.

3. Embrasures or spillways:I. Posterior teeth:

• Facially:

The size of the occlusal embrasures increase in a distal direction, while the opposite is with the cervical embrasures. Why???????

3. Embrasures or spillways: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.

1- Contact areas become more cervically located from posteriorteeth to anterior teeth in each quadrant. ( )

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

Conclusion

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