Extraoral Landmarks in Dentistry
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Extraoral Landmarks in Dentistry

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Questions and Answers

What is the inter-pupillary line and its significance in denture orientation?

The inter-pupillary line is an imaginary line between the two pupils of the eyes, used to orient the anterior occlusal plane of artificial teeth.

Describe the ala-tragus line and its role in denture construction.

The ala-tragus line is an imaginary line from the ala of the nose to the tragus of the ear, used to orient the posterior occlusal plane of artificial teeth.

What is the canthus-tragus line and how does it assist in dental prosthetics?

The canthus-tragus line runs from the outer canthus of the eye to the tragus of the ear and is used for the arbitrary location of the condyles.

Explain the nasio-labial sulcus and why it becomes more prominent with age.

<p>The nasio-labial sulcus is a depression from the ala of the nose to the corner of the mouth, becoming deeper with age due to tissue changes.</p> Signup and view all the answers

What is the vermillion border and its relationship with the orbicularis oris muscle after tooth loss?

<p>The vermillion border is the transition between the lip mucous membrane and facial skin, which loses support from the orbicularis oris after tooth loss.</p> Signup and view all the answers

Define the labial tubercle and its changes post tooth resorption.

<p>The labial tubercle is a swelling in the center of the upper lip's vermillion border that drops inward due to loss of support after tooth resorption.</p> Signup and view all the answers

Identify two extraoral landmarks used in complete denture orientation.

<p>Two extraoral landmarks are the inter-pupillary line and the ala-tragus line.</p> Signup and view all the answers

Why is the angle of the mouth important in the context of complete dentures?

<p>The angle of the mouth, or commissure, is important for esthetics and function of dentures, as it affects lip closure and facial contour.</p> Signup and view all the answers

What does the curvature of the mento-labial sulcus indicate in relation to maxillo-mandibular relationships?

<p>The curvature indicates the maxillo-mandibular relationship, with a gentle curve representing a normal ridge relationship.</p> Signup and view all the answers

How is Angle Class II characterized in terms of the mento-labial sulcus?

<p>Angle Class II is characterized by a retruded mandibular position, resulting in the mento-labial sulcus forming an acute angle.</p> Signup and view all the answers

What is the philtrum and how can it be affected by dental issues?

<p>The philtrum is a diamond-shaped area at the center of the upper lip that can be distorted by loss of teeth and alveolar bone resorption.</p> Signup and view all the answers

What condition is referred to as angular cheilitis, and what causes it?

<p>Angular cheilitis is inflammation and drooping of saliva from the angle of the mouth, caused by prolonged edentulism or vitamin B12 deficiency.</p> Signup and view all the answers

Define the modiolus and describe its significance in denture construction.

<p>The modiolus is the point where facial muscle fibers meet, and it is significant because its position changes after tooth loss, affecting denture fit.</p> Signup and view all the answers

What is a stress bearing area in the context of intraoral anatomy?

<p>A stress bearing area is a region that can withstand forces from the denture base without causing tissue ulceration or bone resorption.</p> Signup and view all the answers

How does the construction of dentures address issues with the angle of the mouth?

<p>Proper denture construction with correct vertical dimension and positioning of anterior teeth will support the angle of the mouth.</p> Signup and view all the answers

What happens to the modiolus after tooth loss and alveolar bone resorption?

<p>After tooth loss and alveolar bone resorption, the modiolus drops inward, resulting in a characteristic appearance of edentulism.</p> Signup and view all the answers

What are the three criteria of a stress-bearing area in the upper arch?

<p>The criteria are that it must be relatively horizontal, consist of compact bone type, and have thick mucosa.</p> Signup and view all the answers

Define a relief area in the context of dental prosthetics.

<p>A relief area is a sensitive elevated region that cannot withstand pressure, necessitating a space in the denture base to reduce stress.</p> Signup and view all the answers

What role does the residual alveolar ridge play in denture support?

<p>The residual alveolar ridge serves as the primary stress-bearing area in the upper arch, covered with dense fibrous connective tissue that is favorable for support.</p> Signup and view all the answers

What is the significance of the maxillary tuberosity in denture retention?

<p>The maxillary tuberosity is a bony prominence that helps retain and support the maxillary denture.</p> Signup and view all the answers

Explain the importance of the median palatine raphe in denture fitting.

<p>The median palatine raphe is an area of firm mucous membrane that lacks resiliency, and stress should not be applied here to avoid denture rocking.</p> Signup and view all the answers

What happens to the incisive papilla after tooth extraction?

<p>After tooth extraction, the incisive papilla migrates to the crest of the ridge due to alveolar bone resorption.</p> Signup and view all the answers

Why is relief of the incisive papilla necessary during denture construction?

<p>Relief of the incisive papilla is necessary to avoid interference with the blood and nerve supply, which can cause sensations of burning.</p> Signup and view all the answers

What are some supporting structures of the maxillary arch?

<p>Some supporting structures include the residual alveolar ridge, maxillary tuberosity, median palatine raphe, incisive papilla, palatine rugae, torus palatinus, and fovea palatinae.</p> Signup and view all the answers

How does the position of maxillary canines relate to the incisive papilla?

<p>A perpendicular line drawn posterior to the center of the incisive papilla passes through the tip of the maxillary canines.</p> Signup and view all the answers

What is the function of the palatine rugae in relation to speech?

<p>Palatine rugae assist the tongue in forming a seal for linguopalatal sounds, such as the 'S' sound.</p> Signup and view all the answers

What is the significance of the torus palatinus in denture fitting?

<p>The torus palatinus may necessitate relief in the denture base if small or surgical removal if large to prevent irritation.</p> Signup and view all the answers

What are fovea palatinae and their anatomical location?

<p>Fovea palatinae are small pits located just posterior to the junction of the hard and soft palate.</p> Signup and view all the answers

Describe the composition and suitability of the residual alveolar ridge for stress bearing.

<p>The residual alveolar ridge is formed of cancellous bone and is unsuitable for bearing stresses.</p> Signup and view all the answers

What is the anatomical feature referred to as the crest of the ridge?

<p>The crest of the ridge is the highest part of the residual alveolar ridge.</p> Signup and view all the answers

What complications can arise from the presence of a torus palatinus during denture use?

<p>A torus palatinus can cause tissue irritation and ulceration when pressure is applied by a maxillary denture.</p> Signup and view all the answers

Identify two supporting structures of the mandibular arch.

<p>The external oblique ridge and the buccal shelf of bone are two supporting structures of the mandibular arch.</p> Signup and view all the answers

What is the function of the external oblique ridge in denture support?

<p>The external oblique ridge acts to prevent denture displacement by the masseter muscle, as lower dentures should cover but not extend beyond it.</p> Signup and view all the answers

Why is the buccal shelf considered a primary stress-bearing area for dentures?

<p>The buccal shelf is nearly perpendicular to vertical masticatory forces and consists of dense compact bone, making it ideal for support.</p> Signup and view all the answers

Describe the location of the mental foramen and its significance in denture design.

<p>The mental foramen is located on the buccal surface of the mandible between the first and second premolars, and relief is required to avoid lower lip numbness.</p> Signup and view all the answers

What anatomical structures are included in the retromolar pad and how does it support dentures?

<p>The retromolar pad contains mucous glands and muscle fibers, and it provides a shock-absorbent cushion, contributing to denture support and stability.</p> Signup and view all the answers

What is the significance of the pterygomandibular raphe in denture wearers?

<p>The pterygomandibular raphe may cause dislodgement of dentures as it stretches during mouth opening, affecting stability.</p> Signup and view all the answers

How does the presence of a torus mandibularis affect denture fitting?

<p>A torus mandibularis may necessitate relief in the denture base to avoid mucosal impingement if it is covered with thin mucosa.</p> Signup and view all the answers

Explain the role of the retromolar pad in maintaining denture function.

<p>The retromolar pad helps cushion the denture, maintain the occlusal plane, and assists in arranging mandibular posterior teeth.</p> Signup and view all the answers

What could happen if the denture base extends beyond the external oblique ridge?

<p>If the denture base extends beyond the external oblique ridge, it may lead to denture displacement due to the action of the masseter muscle.</p> Signup and view all the answers

Study Notes

Extraoral Landmarks

  • Inter-pupillary Line: An imaginary line between the centers of the pupils when looking straight ahead. It helps to orient the anterior occlusal plane of artificial teeth.
  • Ala-Tragus Line (Camper's Line): An imaginary line from the ala of the nose (side of the nose) to the tragus of the ear. This line is used to orient the posterior occlusal plane of artificial teeth.
  • Canthus-Tragus Line: An imaginary line connecting the outer canthus of the eye (where the upper and lower eyelids meet) to the tragus of the ear. Used to arbitrarily locate the condyles (rotational axis).
  • Nasio-labial Sulcus: A depression running from the ala of the nose laterally and downward to the corner of the mouth. It becomes deeper with age and can be restored through proper positioning of the anterior teeth and contouring of the upper denture flange.
  • Vermillion Border: Transitional epithelium between the mucous membrane of the lip and facial skin. It is usually affected by resorption of the labial alveolar bone, resulting in a diminished appearance. Denture flanges and anterior tooth positioning can restore this.
  • Labial Tubercle: A small bulge in the middle of the upper lip's vermillion border. Similar to the vermillion border, it loses support with age and can be addressed with appropriate denture flanges and anterior teeth positioning.
  • Mento-labial Sulcus: A depression running horizontally between the lower lip and chin. Its curvature gives an indication of the maxillo-mandibular relationship:
    • Angle Class I: Gentle curvature in a normal ridge relationship.
    • Angle Class II: An acute angle in a retruded mandibular position.
    • Angle Class III: An obtuse angle (greater than 180 degrees) in a protruded maxillo-mandibular relationship.
  • Philtrum: A diamond-shaped area at the center of the upper lip, below the base of the nose. It can be distorted by tooth loss and bone resorption, but its original form can be restored with proper tooth arrangement and labial flange contouring.
  • Angle of the Mouth (Commissure): The point where the upper and lower lips meet. Drooping saliva and inflammation are termed angular cheilitis, often due to prolonged edentulism, dentures with reduced vertical dimension, or vitamin B12 deficiency. This can be improved with dentures that have proper vertical dimension and anterior tooth positioning.
  • Modiolus: The point of meeting for facial muscle fibers. It is a depression located below and distal to the angle of the mouth. Resorption causes the modiolus to drop inward, but proper denture construction can help restore the appearance.

Intraoral Landmarks

  • Supporting Structures: Areas that can withstand forces applied by the denture base without tissue ulceration, bone resorption, or denture dislodgement. They have horizontal surfaces, compact bone, and thick mucosa.
  • Limiting Structures: Sensitive elevated areas that cannot withstand pressure and require relief in the denture base to reduce stress.
  • Stress Bearing Areas: Intral oral areas that can withstand forces from the denture base.
    • Maxillary Supporting Structures:
      • Residual Alveolar Ridge: The remaining portion of the alveolar process and its covering soft tissue after tooth extraction. The highest point is the crest of the ridge. It’s the primary stress bearing area in the upper arch, covered with dense fibrous tissue.
      • Maxillary Tuberosity: A rounded bony prominence at the distal end of the maxillary ridge. It should be covered by the denture for retention and support.
      • Median Palatine Raphe: An area of firmly attached mucous membrane to bone with little submucosal tissue. It runs from the incisive papilla to the distal end of the hard palate covering the median palatine suture. It has no resiliency and should not be stressed. Relief of the median palatine raphe is important to prevent rocking, which leads to uneven pressure on the tissues.
      • Incisive Papilla: Pear-shaped soft tissue elevation at the midline, palatal to the upper central incisors covering the incisive foramen (which houses the nasopalatine nerves and vessels). It migrates to the crest of the ridge after tooth loss. Needs relief in dentures to avoid interference with nerves and blood supply. Also acts as a guide for anterior tooth position.
      • Palatine Rugae: Irregular ridges of dense connective tissue radiating from the midline. Assist the tongue with taste and speech functions. They can withstand stresses and serve as a secondary stress bearing area.
      • Torus Palatinus: Bony bulge in the midline of the palate. It needs relief in the denture or surgical removal (for large ones) as it can cause trauma and irritation.
      • Fovea Palatinae: Two small pits located on either side of the midline just behind the hard and soft palate junction. They are openings for minor salivary gland ducts. The posterior border of the maxillary denture should extend 2mm posterior to the fovea palatinae.
  • Mandibular Supporting Structures:
    • Residual Alveolar Ridge: Similar to maxillary, it’s the remaining portion of the alveolar process after tooth extraction. It is formed of cancellous bone and can only bear minimal stress.
    • External Oblique Ridge: A dense bony ridge descending diagonally from the ramus of the mandible towards the mental foramen. The lower denture should cover this ridge, but not extend beyond it to avoid denture displacement by the masseter muscle.
    • Buccal Shelf of Bone (Buccal Plateau): A nearly horizontal bone shelf between the residual ridge crest and the external oblique ridge in the molar region. It is comprised of dense compact bone and should be covered for denture support. It’s considered a primary stress bearing area because it is nearly perpendicular to forces applied by the masseter muscle.
    • Mental Foramen: Located on the buccal surface of the mandible (premolar region), between the roots of the first and second premolars. The mental nerve and vessels pass through this foramen. Relief is necessary to avoid numbness of the lower lip.
    • Retromolar Pad: A pear-shaped soft tissue pad at the distal end of the mandibular ridge. It contains mucous glands, the temporalis tendon, pterygo-mandibular raphe, fibers of the buccinator and superior constrictor muscles. Needs to be covered by the denture for support and acts as a shock absorber due to its spongy nature. Helps maintain the occlusal plane.
      • Anterior 2/3rd: Height of occlusal rims should not cross this area.
      • Posterior 1/3rd: Helps in arranging the mandibular posterior teeth.
  • The Pterygomandibular Raphe: The union of the buccinator and superior constrictor muscles. It extends from the hamular process to the retromolar pad. It stretches during mouth opening and may cause denture dislodgement.
  • Torus Mandibularis: A bony prominence sometimes present on the inner surface of the mandible in the premolar region. It can be unilateral or bilateral and needs relief if covered by thin mucosa.
  • Internal Oblique Ridge (Mylohyoid Ridge): A bony elevation located on the inner surface of the mandible.
  • Genial Tubercles or Mental Spine: Bony projections found on the lingual surface of the mandible. They serve as attachment points for muscles and ligaments.

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Description

This quiz covers important extraoral landmarks used in dentistry, including the Inter-pupillary Line, Ala-Tragus Line, and more. Understanding these landmarks is crucial for properly orienting artificial teeth and improving dental aesthetics. Test your knowledge on these foundational concepts in dental anatomy.

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