Anatomy and Physiology In Relation to Complete Denture Construction

→ The knowledge of oral anatomy and physiology will help the operator and provides enough landmarks to act as positive guide during denture construction.

→ This subject can be discussed under:[ I ] Extra-oral landmarks of prosthetic importance.[ II ] Intra-oral landmarks of prosthetic importance:

a) In the maxilla.b) In the mandible.

[ III ] Border structures that limit the periphery of the denture:a) In the maxilla.b) In the mandible.

[ IV ] Anatomy and physiology of the T.M. J. and mandibular movements.

[ I ] Extra-oral Landmarks Of Prosthetic Importance:Landmark Description Significance

1- Inter-pupillary line

- Imaginary line running between the two pupils of the eye when the pt. is looking straight forward.

- Establishing the anterior Occlusal plane of the artificial teeth of the denture.

2- Ala-tragus line (Camper's line)

- Imaginary line running from the Inferior border of the ala of the nose to the superior border of the tragus of the ear.

- Establishing the posterior Occlusal plane of the artificial teeth of the denture.

3- Canthus-tragus line

- Imaginary line running from the outer canthus of the eye to the superior border of the tragus of the ear.

- Locating the position of the condyles.

4- Naso-labial sulcus

- Depression that extends from the ala of the nose in a downward and lateral direction to the corner of the mouth.

- After extraction of teeth it becomes accentuated and should be restored by complete denture.

5- Vermillion border - The transitional epithelium between the mucous membrane of the lip and the skin.

- After extraction disappears in the upper lip and becomes accentuated in the lower& should be restored by a complete denture.

6- Mento-labial sulcus

- Depression runs horizontally between the lower lip and chin.

- It determines the Angle of Classification:1- Angle class [I]: Normal ridge relationship.2- Angle class [II[: Retruded mandibular position.3- Angle class [III]: Protruded maxillo-mandibular relation ship.

Landmark Description Significance

7- Philtrum - Diamond-shaped area between the center of the upper lip and the base of the nose.

- After extraction of teeth it becomes flattened and should be restored by a complete denture.

8- Modiolus - The point of meeting of facial muscle fibers.

- After extraction of teeth it becomes downwards and should be restored by a complete denture.

9- Angle of the mouth (commissure of the lips)

- Point of meeting between the upper and lower lip.

- (Angular Chilitis): Inflammation and ulceration as a result of:1- Prolonged edentulism.2- ↓ vertical dimension of complete denture.3- Vitamin B deficiency.

Fig.1: A, The Philtrum, naso-labial sulcus, commissure of the lips& mento-labial sulcus.B, Modiolus and Orbicularis Oris muscle.

Fig.2: Profile view showing the relation of the upper and lower anterior teeth and the curvature of mento-labial sulcus.

[ II ] Intra-oral landmark of prosthetic importance:

A- In the Maxilla:Landmark Description Significance

1- Residual ridge - The portion of the alveolar process& it's soft tissue covering that remains after extraction.

- It covers by a dense connective tissue fibers so, it can be act as a 1ry stress bearing area.

2- Maxillary tuberosity

- Bony prominence located posterior to the upper 3rd molar.

- Aid in support, retention and stability of the complete denture.- When it is large:1- Relieved.2- Modify the path of insertion. (unilateral enlargement).3- Surgical removal.

3- Median palatine raphe

- The mucoperiostium that covers the median palatine suture.

- When it is prominent it should be relieved.- Lack of relief cause:1- rocking of the denture due to bone resorption.2- Tissue ulceration.3- Mid-line denture fracture.

4- Incisive papilla - Pear-shaped elevation present in the midline behind the 2 centrals.

- After extraction of teeth it migrates to the crest of the ridge.- It should be relieved to avoid the burning sensation of the palate.

5- Palatine rugae - It is irregular elevations radiates from the midline of the anterior part of the palate.

- 2ry stress bearing area.- Prevent forward movement of the denture.- If it is sensitive or prominent it should be relived.

6- Torus palatinus - Bony prominence present at both sides of the midline of the palate.

- It should be:1- Relieved.2- Surgical removal.

7- Fovea palatinae - Two openings of minor salivary glands present in both sides of the midline posterior to junction of hard and soft palate.

- It determines the posterior extension of the upper complete denture to be 2mm posterior to it.

B- In the Mandible:Landmark Description Significance

Fig.3: A, Diagram of the upper arch.B, Diagram of the lateral surface of the maxilla.

1- residual ridge - The portion of the alveolar process& it's soft tissue covering that remains after extraction.

- Don't used as 1ry stress bearing area → Covered by movable fibrous connective tissue.- Don't Provide stability or support.

2- External oblique ridge

- Bony ridge running downward and forward from ramus to reach mental foramen.

- It is a limiting structure to the complete denture and not extend to it.

3- Buccal shelf area - Bony area extends between the external oblique ridge and the residual ridge.

- Used as 1ry stress bearing area:1- Perpendicular to the vertical masticatory force.2- Formed from compact bone.3- provide support.

4- Mental foramen - It's located on the Buccal surface of the mandible between the roots of 1st and 2nd premolar.

- Lack of relief → numbness of the lower lip.

5- Retromolar pad - Pear-shaped area located distal to the lower 3rd molar.

- Shock absorbent.- Gives retention not support.- Determine the level of the Occlusal plane.

6- Torus mandibularis

- Bony prominence located at the inner surface of premolar area.

- It should be: 1- Relieved.2- Surgical removal.

7- Internal oblique ridge (Mylohyoid ridge)

- Irregular bony ridge of median surface of the mandible which the Mylohyoid muscle attached.

- It should be relieved during complete denture construction.

8- Genial tubercle (Mental spine)

- Two bony projections present at the median surface of mandible at midline of each side of symphesis.

- Represent the attachment of geniohyiod and genioglossus muscles.- If it's prominent, it should be relieved.

[ III ] Border Structures That Limits The Periphery Of The Denture:

Fig.4: Diagram showing the mandible:A, Buccal view.B, Lingual view.