Anatomical Landmarks for Denture Design PDF

ANATOMICAL LANDMARKS Dr. Wafaa Ibrahim BDS, MSc, PhD Cairo University Assoc. Prof. of Removable Prosthodontics, Delta University  Extra-oral examination 1. Nasolabial Sulcus A crease that extends laterally and downwards from the ala of the nose to the corners of the mou...

ANATOMICAL LANDMARKS Dr. Wafaa Ibrahim BDS, MSc, PhD Cairo University Assoc. Prof. of Removable Prosthodontics, Delta University  Extra-oral examination 1. Nasolabial Sulcus A crease that extends laterally and downwards from the ala of the nose to the corners of the mouth that becomes more prominent with aging. Can be restored through: – Proper positioning of anterior teeth. – Proper establishment of occlusal vertical dimensions. – Thickness of the denture flange.  Extra-oral examination 2. Mentolabial Sulcus Runs from side to side horizontally between the lower lip and the chin. Its curvature frequently indicates the character of the maxillomandibular relationship.  Extra-oral examination 3- Nasolabial Angle Angle between columella of nose & philtrum of lip Normally, approximately 90 as viewed in profile  Extra-oral examination 4. Philtrum A diamond shaped area at the center of the upper lip and base of the nose. Becomes flattened with loss of teeth and resorption of the labial alveolar bone. Can be restored with  Proper positioning of anterior teeth.  Thickness of the denture flange.  Extra-oral examination 5. Vermillion Border It is the transitional epithelium between the mucous membrane of the lips and the skin. The amount of vermillion border shown on the lips depends on: – The bulk of the orbicularis oris muscle. – The amount of the labial alveolar bone. – The position of teeth. – Thickness of the denture flange.  Extra-oral examination 5. Vermillion Border: With loss of teeth and resorption of labial alveolar bone orbicularis oris loses its support and drops inward (palatally)  diminution of amount of vermillion border showing on the upper lip and relative fullness of the lower lip.  Extra-oral examination 5. Vermillion Border: Proper modification of denture flanges and the position of the anterior teeth can improve the appearance.  Extra-oral examination 6. Angle of the Mouth Denture should support the mouth angle. Lack of proper support of the upper lip and a reduced vertical dimension angular cheilitis that is fissuring and inflammation of the angle of the mouth as a result of a continuous wetting from saliva Helps in determining the width of six anterior teeth  Extra-oral examination 7. Modiolus The modiolus is located at the meeting place of the buccinator and other facial muscles near the angle of the mouth.  Extra-oral examination 7. Modiolus With the loss of teeth, the modiolus is displaced giving the appearance of an edentulous person (sunken cheek). The buccal surface of the premolar region of the lower denture must be thin to avoid the modiolus lifting the denture.  Extra-oral examination 8. Ala-tragus line (Camper’s Line) An imaginary line running from the ala of the nose to the tragus of the ear. Aids in orientation of the posterior occlusal plane of artificial teeth. 8. Ala-tragus line (Camper’s Line) This parallism allow the masticatory force to be directed at right angle to the ridge Ala-tragus Posterior occlusal plane 8. Ala-tragus line (Camper’s Line) This parallism allow the masticatory force to be directed at right angle to the ridge Ala-tragus Poste ri or oc c lusal p lane  Extra-oral examination 9. Interpupillary line An imaginary line running between the two pupils of the eyes when the patient is looking straight forward. Aids in orientation of the anterior occlusal plane of artificial teeth. This parallism allows vertical force transmission to the supporting tissues. Any deviation from this parallism will place non vertical forces which are damaging to the tissues  Extra-oral examination
10- Canthus tragus line Imaginary line running from outer canthus of the eye to the tragus of the ear It is used to arbitrarily to locate the mandibular axis of the condyle  GROUPING OF LANDMARKS Landmarks of edentulous jaws Supporting Limiting structures Relief areas structures  LIMITING STRUCTURES These are the sites that will guide us in having an optimum extension of the denture so as to engage maximum surface area without encroaching upon the muscle actions Encroaching upon these structures dislodgement of the denture and/or soreness of the area While failure to cover the areas up to the limiting structure decreased retention stability and support. Intra oral Anatomical landmarks A- Maxilla I- Border structures (limiting) 2- Denture bearing areas (supporting) B- Mandible I- Border structures (limiting) 2- Denture bearing areas (supporting)  Border structures
(Maxilla) 1. Labial frenum Fold of mucous membrane that may be single or multiple extending from the mucous lining of the lip towards the crest of the ridge on the labial surface. Prosthetic value: Labial notch should be provided in the denture to facilitate functional movement of the frenum and avoid ulceration.  Border structures
(Maxilla) 2. Labial vestibule Extends on both sides from the labial frenum to the buccal frenum. Prosthetic value: The reflection of the mucous membrane superiorly determines the height of the denture flange.  Border structures
3. Buccal frenum (Maxilla) Folds or folds of mucous membrane that vary in size and position, and extends from the buccal mucous membrane reflection area to the crest of the residual ridge. Prosthetic value: Denture borders should be functionally trimmed to avoid dislodgment of the denture during function. Muscles: Levator Anguli inserts beneath the frenum, Orbicularic Oris pulls it forward, Buccinators muscle pulls it backwards, thus it requires more clearance than the labial frenum.  Border structures
(Maxilla) 4. Buccal vestibule The space distal to the buccal frenum. Bounded externally by the cheek and internally by the residual ridge. Buccinator muscle will not displace the denture (horizontal direction of the fibers).  Border structures (Maxilla) 4. Buccal vestibule Thickness of the distal end of the buccal flange must accommodate the coronoid process (displace denture). The size of the buccal vestibule varies with:  contraction of the buccinator muscle  coronoid process of the mandible during opening Maxilla  Border structures
(Maxilla) 5. Hamular notch Notch located between maxillary tuberosity anteriorly and the pterygoid hamulus posteriorly. Prosthetic value: Posterior palatal border of the denture should extend from hamular notch on one side to the hamular notch on the other side passing through vibrating line of soft palate.  Border structures
(Maxilla) 6. Vibrating line of the soft palate Soft palate has two parts; anterior immovable and posterior movable. Vibrating line (Ah line) is an imaginary line lying between the movable and immovable parts of the soft palate. Vibrating line extends from one hamular notch to the other, 2 mm posterior to fovea palatinae following palatal contour. Hard palate Immovabl e movable Soft palate  Border structures
(Maxilla) 6. Vibrating line of the soft palate Posterior palatal seal should be created on the compressible immovable tissues of soft palate. Its width follows soft palate curvature.  I II III  Border structures that limit the denture base periphery (maxillary) 1. Labial frenum. 2. Labial vestibule (labial mucous membrane reflection area). 3. Buccal frenum. 4. Buccal vestibule (buccal mucous membrane reflection area). 5. Hamular (pterygomaxillary) notch. 6. Vibrating line of the soft palate.  Anatomical Landmarks 3 II- Mandible B- Anatomical landmarks of denture bearing area (supporting structures) Anatomical structure Description Prosthetic value 1- Alveolar ridge –It is the portion of the alveolar process and its soft tissue covering that remains after the extraction of teeth. –The highest continuous surface of the ridge is called the crest of the ridge, it is covered with a layer of dense fibrous connective tissue. 2- Retromolar pad – Pear-shaped area found –Used as a guide for locating the on each side of the distal position of the occlusal plane of the end of the residual mandibular denture (must not be mandibular ridge. higher than half of its vertical –Contains loose areolar height). connective tissue, fibers –Must be covered by the denture to from buccinator, superior resist backward movement induced constrictor, and temporalis by pressure from the lower lip. muscles, and limited – Covering the pads with the posteriorly by denture base maximizes the tissue pterygomandibular raphe. coverage helps reduce the rate of alveolar ridge resorption. 3- External oblique ridge Ridge of dense bone Lower denture should cover but not extending from just above extend beyond external oblique the mental foramen ridge to avoid displacement by superiorly and distally, then powerful musculature in this area. becomes continuous with the anterior border of the ramus of the mandible. 4- Buccal shelf area (buccal plateau) – Bounded externally by the external oblique ridge and internally by the slope of the residual ridge. – Composed of very dense cortical bone. – Forces of occlusion can be directed nearly at right angle to buccal shelf than any other area. 5- Mental foramen – Located on the buccal In cases of severe resorption, it is surface of the mandible usually located on the crest of the Dr. Wafaa Ibrahim Page 1  Anatomical Landmarks 3 between the roots of the 1st ridge (relief is required to avoid and 2nd premolars. pain and numbness of the lower lip) – Mental nerves and vessels pass through it. 6- Torus mandibularis – It is a bony projection Surgical removal or relief according sometimes found on the to size and extension. inner surface of the mandible in the premolar region. – It may be bilateral or unilateral. 7- Internal oblique ridge (mylohyoid – Ridge that extends near – Should be covered by the denture. ridge) the inferior border of the – Surgical removal or relief if sharp mandible in the incisal or prominent. region, then becomes progressively higher posteriorly – Gives attachment to mylohyoid muscle. 8- Genial tubercles (mental spines) – 4 small prominences Cannot be palpated unless in cases located in the inner surface of severe resorption where relief is of the mandible, two on required. each side of the symphysis. – Genioglossi muscles are attached to their upper surface and geniohyoid to their lower surface. Dr. Wafaa Ibrahim Page 2 Anatomical Landmarks 3 Denture Support (denture foundation area) A-Primary stress bearing areas: 1- Areas which are able to resist vertical forces of occlusion. 2- They are made of cortical bone 3- Protected by firmly attached mucous membrane.Maxillary arch and palate  Maxillary Crest of the ridge. Flat area of the palate.  Mandibular Buccal shelf of bone. Crest of the ridge (if well formed). B- Secondary stress bearing areas: Areas which by their histological nature and their inclined planes can resist lateral forces of occlusion. Dr. Wafaa Ibrahim Page 3 Anatomical Landmarks 3  Maxillary Lateral slopes of palate. Rugae area. Labial & buccal slopes of the ridge.  Mandibular All ridge slopes. C- Relief areas: Areas which when subjected to occlusal forces, either will cause discomfort to the patient or instability of the denture and eventually resorption of supporting structures. Relief areas in the maxillary arch: 1. Incisive papilla 2. Median palatine raphe 3. Torus palatines 4. Maxillary tuberosity if large in size and not allow for proper placement of the denture 5. Any bony prominences Relief areas in the mandibular arch: 1. Mental Foramen (with flat ridge) 2. Genial tubercles. 3. Sharp mylohyoid ridge. 4. Crest of a knife edge ridge. 5. Mandibular tori. 6. Any bony prominences. Dr. Wafaa Ibrahim Page 4