dentin™
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NBDE I
PERIKYMATA-tiny valleys on the TOOTH (CROWN) SURFACE created by the termination of the lines of Retzius, and travel circumferentially around the crown. MATURATION OF ENAMEL is characterized by a percentage INCREASE in inorganic content and a percentage DECREASE in water and organic content. COMPARISON OF TOOTH TISSUES
Mineral Content Color Formative cells Embryology Repair Aging Sensitivity Cells in mature tissues
ENAMEL 96% (highest)
DENTIN 70%
CEMENTUM 50%
Translucent yellow Ameloblast Epithelial No replacement, some remineralization Wear, staining, caries
Light yellow Odontoblast Ectomesenchyme Physiological, reparative, secondary dentin Increase in secondary and sclerotic dentin Yes-only as pain Cytoplasmic extensions from odontoblasts
Light yellow Cementoblast Ectomesenchyme New cementum deposition
None None
Increased amount with age (apex) No Cementocytes
PULP 0% (except denticles/pulp stones) Blood red Dental Papilla Ectomesenchyme Can recover if mild inflammation but severe = death Reduced size and may be obliterated. Yes Odontoblasts and other cell types
ORTHODONTIC MOVEMENT OF TEETH: always causes remodeling of alveolar bone proper to accommodate teeth movement. • If a tooth is tilted MESIALLY during orthodontics, the CORONAL HALF of the mesial wall shows resorption due to osteoclastic activity, while the CORONAL HALF of the distal wall shows deposition due to osteoblastic activity. • A similar situation is the alternate loosening and tightening of a deciduous tooth before it is lost caused by the alternate resorption (cementoclasts, osteoclasts) and apposition (cementoblasts, osteoblasts) of cementum and bone. • During active tooth eruption, there is apposition of bone on all alveolar crest surfaces and on all walls of the bony socket. Permanent teeth move OCCLUSALLY & BUCALLY when erupting. • In a newly erupted tooth, the junction between tooth surface and the crevicular epithelium consists of a basal lamina-like structure between enamel and epithelium. Apical abscesses of MANDIBULAR SECOND & THIRD MOLARS have a marked tendency to produce cervical spread of infection MOST RAPIDLY. Attachment of muscles may determine the direction/route that an infection will take, channeling the infection into certain tissue spaces. •
INFECTIONS OF MANDIBULAR TEETH (Especially 2nd & 3rd molars) perforate the bone below the buccinator causing swelling of the lower half of the face. The infection spreads medially from the mandible into the submandibular and masticatory spaces. It pushes the tongue forward and upward. Further spread cervically may involve the visceral space and lead to edema of the vocal cords and airway obstruction.
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