Applied Anatomy Of The Edentulous Oral Structures PDF

Applied Anatomy Of The Edentulous Oral Structures. (Landmarks Related To The Complete Denture) Dr Mohamed Farouk Abdalla Professor Of Prosthodontics Galala And Cairo University. Anatomy Related To Complete Dentures Are Divided Into : Extraoral landmarks....

Applied Anatomy Of The Edentulous Oral Structures. (Landmarks Related To The Complete Denture) Dr Mohamed Farouk Abdalla Professor Of Prosthodontics Galala And Cairo University. Anatomy Related To Complete Dentures Are Divided Into : Extraoral landmarks. Intraoral landmarks.  Extra-oral Landmarks 1. Inter-pupillary line. 2. Ala-tragus line (Camper’s line) 3. Canthus-tragus line. 4. Nasio-labial sulcus 5. Vermillion border 6. Labial tubercle 7. Mento-labial sulcus 8. Philtrum 9. Angle of the mouth (commissure) 10. Modiolus 1- Inter-pupillary line: It is an imaginary line running between the two pupils of the eyes when the patient is looking straight forward. It helps in orientation of the anterior occlusal plane of the artificial teeth. 2- Ala-tragus line (Camper’s line) It is an imaginary line running from the ala of the nose (side of the nose) to the tragus of the ear. It is used in orientation of the posterior occlusal plane of the artificial teeth. 3- Canthus-tragus Line. It is an imaginary line running from the outer canthus of the eye (meeting between the upper and lower eye lids) to the tragus of the ear. It is used in arbitrary location of the condyles (rotational axis). 4- Nasio-labial sulcus It is a depression (crease) running from the ala of the nose laterally and downward to the corner of the mouth. It becomes deeper and more prominent with aging. It can be approximately restored through proper positioning of the anterior teeth of the denture, proper establishment of occlusal vertical dimension and proper contouring of the upper denture flange. 5- Vermillion Border It is the transitional epithelium between mucous membrane of the lip and the skin of the face. After loss of teeth and resorption of the labial alveolar bone, orbicularis oris muscle loses its support and drops inward, resulting in diminution of the amount of the vermillion border showing with relative fullness of the lower lip. Proper modification of denture flanges and position of the anterior teeth improve such appearance. 6- Labial Tubercle It is a little swelling in the mid of the vermillion border of the upper lip. After loss of teeth and resorption of the labial alveolar bone, it loses its support and drops inward. Proper modification of denture flanges and position of the anterior teeth improve such appearance. 7- Mento-labial sulcus It is a depression running horizontally between the lower lip and the chin. Its curvature indicates the maxillo-mandibular relationship: Angle Classification Angle Class I: Angle Class II: Angle Class III: In normal ridge relationship, In retruded mandibular In protruded maxillo- the mento-labial sulcus shows position, the mento-labial mandibular a gentle curvature. sulcus presents an acute relationship, the angle. mento-labial sulcus forms an obtuse angle (angle of 1800). 8- Philtrum It is a diamond-shaped area at the center of the upper lip under the base of the nose. It is distorted with loss of teeth and alveolar bone resorption. Proper tooth arrangement and proper labial flange contouring would approximately restore the original form of the philtrum. 9- Angle Of The Mouth (Commissure) It is the point of meeting between upper and lower lips. Inflammation and drooping of saliva from the angle of the mouth is termed angular cheilitis. Angular cheilitis may be the result of: a. Prolonged edentulism, b. Denture with reduced vertical dimension and c. Vitamin B12 deficiency. In the first two conditions, construction of the denture with proper vertical dimension and proper positioning of the anterior teeth will support the angle of the mouth and hence improve the case. Inflammation due to vitamin B12 deficiency can be treated by administration of B12.  10- Modiolus It is the point of meeting of facial muscle fibers. It is a depression located below and distal to the angle of mouth. After loss of teeth and alveolar bone resorption, the modiolus drops inward resulting in the characteristic appearance of an edentulism. Proper denture construction would restore the case.  Intra Oral Anatomy (Landmarks)  Intraoral landmarks Maxillary Mandibular Supporting Supporting Limiting Limiting  What Is A Stress Bearing Area? It is an intra oral anatomical region, that is able to withstand the forces applied by the denture base. Without tissue ulceration, bone resorption and denture dislodgement. Criteria of a stress bearing area: Relatively horizontal. Compact bone type. Thich mucosa.  What Is A Relief Area? It is a sensitive elevated area that cannot withstand pressure , so requires a space in the denture base to reduce stress.  Maxillary Supporting Structures: 1. Residual alveolar ridge. 2. Maxillary tuberosity. 3. Median palatine raphe. 4. Incisive papilla. 5. The palatine rugae. 6. Torus palatinus. 7. Fovea palatinae:  1- Residual alveolar ridge:  It is that portion of the alveolar process and its covering soft tissue that remains after extraction of teeth. The highest part of the ridge is called the crest of the ridge.  It is considered the primary stress bearing area in the upper arch as it is covered with a layer of dense fibrous connective tissue that is favorable for supporting the denture. 2- Maxillary tuberosity:  It is a rounded hard bony prominence at the distal most part of the maxillary residual alveolar ridge.  It should be covered by the denture as it plays a role in retention and support of the maxillary denture.  3- Median palatine raphe:  It is an area of firmly adherent mucous membrane to the underlying bone with little submucosal tissue that extends from the incisive papilla to the distal end of the hard palate covering the median palatine suture. Its position in the palate is marked with a raised area of mucous membrane called the median palatine raphe. There is no resiliency in this region and stress cannot be applied in this region.  Lack of relief of the median palatine raphe would result in rocking of the denture due to lack of equilibrium between the resilient and non-resilient tissue supports, with subsequent midline fracture. 4- Incisive papilla:  It is pear-shaped elevation of soft tissue situated at the midline just palatal to the upper centrals. It covers the incisive foramen through which the nasopalatine nerves and vessels pass. After extraction of teeth and alveolar bone resorption, it migrates to the crest of the ridge.  It should be relieved to avoid interference with blood and nerve supply which might cause burning sensation.  It also acts as a guide to the anteroposterior position of the central incisors as the labial surfaces of the upper centrals are usually located 8 to 10mm labial to the middle of the incisive papilla.  It also acts as a guide giving information about location of maxillary canines (a perpendicular line drawn posterior to the center of the incisive papilla to sagittal plane passes through the tip of the canines). A guide to anterior teeth position. 8-10mm 5- The Palatine Rugae:  It is irregular shaped ridges of dense connective tissue radiating from the midline at the anterior one third of the hard plate.  It is associated with the sense of taste and function of speech. They assist the tongue to absorb via its papillae. They also enable the tongue to form a perfect seal when it is pressed against the palate in making the linguopalatal sounds like "S" sound.  These tissues can withstand stresses and serve as secondary stress bearing area unless they are very flabby. 6- Torus Palatinus:  It is a bony bulge sometimes present in the midline of the palate. It varies in size and form.  Because the tissue overlying the ridge is usually very thin, and the torus is very rigid, any pressure caused by a maxillary denture during function will often traumatize the tissue and lead to irritation and ulceration. Additionally it may act as a fulcrum in the middle of the denture.  Therefore, if it is small, the denture base over this area should be relieved and if it is large, it is surgically removed. 7- Fovea Palatinae:  These are two small pits or depressions found on each side of the midline just posterior to the junction of hard and soft palate. They are openings of the ducts of minor salivary glands.  The posterior border of the maxillary denture should extend 2 mm posterior to the fovea palatinae.  Mandibular Supporting Structures: 1- Residual alveolar ridge: 2- External oblique ridge: 3- Buccal shelf of bone (Buccal plataeu): 4- Mental foramen: 5- Retromolar pad: 6- Pterygomandibular raphe. 7- Torus mandibularis: 8- Internal oblique ridge (mylohyoid ridge) 9- Genial tubercles or mental spine.  1- Residual alveolar ridge:  It is that portion of the alveolar process and it's covering soft tissue that remains after extraction of teeth. The highest part of the ridge is called the crest of the ridge.  It is formed of cancellous bone, therefore unsuitable to bear stresses. Sometimes, in severely resorbed ridges, it appears as a cord like soft tissue extending throughout the crest. 2- External oblique ridge:  It is a dense bony ridge descending obliquely from the ramus of the mandible downward and forward till it fades at the mental foramen.  The lower denture should cover but not extend beyond the external oblique ridge to avoid denture displacement by the powerful masseter muscle. 3- Buccal shelf of bone (Buccal plateau):  It is a nearly horizontal shelf of bone that lies between the crest of the residual ridge and the external oblique ridge in the molar area. It is formed from dense compact bone.  It should be covered with the denture to provide support. It is also considered as a primary stress bearing area because:- a. It is nearly perpendicular to the vertical masticatory forces and b. Its nature of bone being compact. 4- Mental foramen:  It is located on the buccal surface of the mandible in the premolar region between the roots of the first and second premolars and through it mental nerves and vessels pass.  Cases of severe ridge resorption, the mental foramen is usually located on the crest of the ridge. Relief of the denture in this area is necessary to avoid numbness of lower lip.  5- Retromolar pad:  It is pear shaped pad of soft tissue present at the distal end of the residual mandibular ridge. It contains mucous glands, temporal tendon, pterygo-mandibular raphe, fibers of buccinator muscle and superior constrictor muscle.  It should be covered by the lower denture to help for denture support. Because of its spongy nature, it acts as a cushion (shock absorbent). It also forms a splendid soft tissue seal.  Helps in maintaining the occlusal plane. Divide the retromolar pad into anterior 2/3rd and posterior 1/3rd Posterior height of occlusal rims should not cross the anterior 2/3rd  Helps in arranging the mandibular posterior teeth. 6- Pterygomandibular raphe:  It is union of buccinator and superior constrictor muscles extending from hamular process to retromolar pad.  It is stretched during mouth opening.  May cause dislodgement of the denture. 7- Torus Mandibularis:  It is a bony prominence sometimes present on the inner surface of the mandible in the premolar region. It varies in size and shape. It is either unilateral or bilateral.  When it is covered with thin mucosa, relief of the denture base in this area could be made to avoid impingement of the mucosa. If the torus mandibularis is large and prevents proper seating of the lower denture, surgical intervention is necessary. 8- Internal oblique ridge and mylohyoid ridge:  It is a bony ridge extending on the medial surface of the mandible from the third molar region to the lower border of the mandible near the midline. It represents the attachment of the mylohyoid muscle to the mandible.  Mylohyoid ridge should be included in the denture bearing area. Thin and sharp mylohyoid ridge should be recontoured to permit better flange placement and border seal. 9- Genial tubercles or mental spine:  These are two small projections located on the medial surface of the mandible, one on each side of the symphysis. They represent the attachment of the genioglossus muscle superiorly and geniohyoid muscle inferiorly.  In extreme alveolar bone resorption, genial tubercles migrate close to the crest of the ridge and become prominent, where they require relief.  Intraoral landmarks Maxillary Mandibular Supporting Supporting Limiting Limiting