Anatomical Landmarks (Part III) PDF

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...

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