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121 Cards in this Set
- Front
- Back
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hard tissues of teeth |
enamel-ectoderm dentin-mesoderm cementum-mesoderm |
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soft tissues of teeth |
pulp tissue-mesoderm |
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periodontium structures |
gingival sulcus junctional epithelium alveolar bone PDL |
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salivary glands |
serous and mucous |
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tongue |
skeletal muscle with specialized projection papilla |
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beginning of human body initiation |
embryo until the eighth week head develops faster than tail |
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beginning of human body cell division and specialization |
increase number of cells cell mobilization histodifferentiation |
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Embryonic layers in tooth development |
ectoderm and mesoderm
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odontogenisis |
name given to origin and tissue formation of teeth |
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teeth development starts when and where? |
5-6 weeks anterior mandibular region then progresses posterior |
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teeth are derived from |
ectoderm and ectomesenchyme |
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development begins with the formation of the primary |
dental lamina (ectoderm) |
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dental lamina |
narrow band of thickened oral epithelium that extends along the oclussal borders of the mandible and maxilla on line where teeth will later appear grows down into underlying mesenchyme |
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steps of tooth development |
10 knobs of epithelial cells are formed on the dental lamina in each arch knobs grow deeper into underlying mesenchyme knobs become early enamel organs enlarges and acquires the shape of a cap by 8th week cap is seen in enamel organs of deciduous incisor tooth germs the mesenchyme inside the cap undergoes differentiation and becomes the dental papilla connective tissue beneath the dental papilla becomes fibrous and encircles the papilla and part of the enamel organ forming the dental sac cap shaped enamel organ (tooth germ) develops and become bell shaped cuboidal cells of inner enamel epithelium elongate into columnar cells- ameloblasts peripheral cells of dental papilla take on columnar shape- odontoblasts as tooth germs develop they are surrounded by islands of bone that will coalesce to form body of mandible and maxilla |
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tooth germ is composed of three components |
enamel organ- ectoderm dental papilla- mesenchyme dental sac- mesenchyme |
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when enamel organ (tooth germ) is bell shaped. Four layers are distinguishable |
outer enamel epithelium (low cuboidal) stellate reticulum stratum intermedium (flat epithelial) inner enamel epithelium (single cuboidal) |
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inner enamel epithelium |
lines the inside of enamel organ layer is separated from dental papilla by a basement membrane which will become the DEJ |
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growth and development of tooth and bone are ____ |
mutually dependent |
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when ameloblasts and odontoblasts start to differentiate and lingual to the enamel organ... |
permanent tooth germ |
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the dental lamina that connects enamel organs to oral epithelium will... |
eventually dissolve |
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in non succedaneous dentition, the primary dental lamina... |
invaginates form the oral epithelium posterior to primary second molar |
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development of face and oral cavity |
embryo is a tube, encases smaller tube which is the primitive digestive tract or gut closed at both ends bc mouth and anus have not formed |
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face made up of three layers |
ectoderm mesoderm endoderm |
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growth |
increase in weight and spatial dimension of an organism or organ three things must happen for growth to occur: increase in number of cells increase in size of cells increase in product of cells |
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development |
organism or organ moving toward maturity - getting older |
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development of primitive mouth |
cephalic end of embryo evolves in advance of caudal end third week an invagination of ectoderm occurs called stomodeum or primitive mouth deepest part of this, it is in contact with endoderm of the foregut without intervening mesoderm called buccopharyngeal membrane fourth week it ruptures establishing communication between stomodeum and primitive digestive tract |
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buccopharyngeal membrane |
separates stomodeum from foregut stomodeum- ectoderm foregut- endoderm |
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development of anterior lobe of hypophysis |
starts as small evagination of stomodeal ectoderm just in front of buccopharyngeal membrane evaginations deepens and forms pit called Rathke's pouch (anterior lobe of hypophysis or pituitary gland, connection to stomodeum is lost) posterior derived from neural ectoderm-brain outside of head above and below stomodeum opening, face and oral and nasal cavities are forming above stomodeum the recently developed forebrain causes a large bilge called the frontal process ectoderm and mesenchyme make up the surface develops into upper part of face, nasal septum, anterior part of roof of mouth below stomodeum (future neck) 5 paired branchial arches I- mandible and large part of maxilla II, III, IV join arch I in development of tongue |
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Except for base of tongue, all of face and oral and nasal cavities are developed from two primary embryonic structures |
frontal process branchial arch I |
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development of the face |
budding of a round process occurs at both ends of first branchial arch growing upward and medially becoming max process remaining medial part of arch becomes hand process |
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max process develops into: |
upper part of cheeks sides of upper lip most of posterior palate |
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hand process develops into: |
lower part of cheeks lower lip lower jaw part of tongue |
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a pair of depressions appear on lower border of frontal process |
R and L olfactory pits they divide into lower part of frontal process into three parts: center- median nasal process. center and tip of nose lateral- R and L nasal process. sides of nose |
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globular process |
lower border of median nasal process grows into length and produces a pair of bulges globular process grows downward to extend below olfactory pits and lies between the right and left max process forms: philtrum premaxilla |
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in the course of facial development, considerable differential growth occurs |
rate of growth |
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development of the nasal cavity |
during the time that the roof of the mouth is forming the nasal cavity becomes divided into L and R chambers by the nasal septum nasal septum develops as growth into stomodeum from the inside of the median nasal process when the R and L lateral palatine processes fuse with each other at the midline, they also fuse with the inferior border of nasal septum |
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development of tongue |
has body and root root lies behind terminal sulcus tongue begins to develop from anterior wall of primitive throat -develops from region of branchial arches I-IV -protrudes upward and anterior -three lingual swelling from inner surface of mandibular arch will unit and become body |
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terminal sulcus |
v shaped groove on top surface of tongue |
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body of the tongue |
two lateral swelling one medial swelling called tuberculum impair behind three lingual swellings, in the center between branchial arches II-IV and involving the inner ends, is a single swelling that will become base or root of tongue called copula |
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foramen caecum |
tip of v shaped line is small depression marks point of embryonic origin of the thyroid gland |
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development of thyroid gland |
originates as small proliferation and epithelium from middle between first and second branchial arches as it develops, descends to final position in neck remains attached to tongue during migration by narrow thyroglossal duct which eventually disappears |
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amelogenesis |
origin and formation of enamel |
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two stages of amelogenesis |
matrix formation mineralization |
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enamel |
organic and inorganic substances 96% inorganic 4% organic matrix and water hardest tissue of body acellular void of blood vessels and nerves basic structural unit is the enamel rod |
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ameloblasts |
inner enamel epithelial cells of enamel organ produce an organic enamel matrix which start after the beginning of dentin formation ameloblasts -> odontoblasts -> dentin -> ameloblasts -> enamel |
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enamel matrix |
laid down in form of rods, rod sheaths, interrod substance |
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interrod substance |
product of intercellular substance between ameloblasts lattice work of rods, rod sheaths and interred substance is the organic matrix of enamel which is 4% of enamel composition |
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amelogenesis process |
ameloblasts move outward away from DEJ -deposit matrix material in form of droplets -accounts for the segments of the enamel rods after ameloblasts complete matrix formation of enamel rods they change to flattened epithelial cells and become part of enamel organ enamel organ is reduced to a few layers of flattened cells covering newly formed crowns |
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Reduced enamel epithelium
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enamel organ reduced a few years of flattened cells covering newly formed crowns REE produces non mineralized secondary enamel cuticle -surrounds enamel until tooth erupts -once it erupts the remaining cuticle is called junctional epithelium |
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junctional epithelium |
once tooth erupts the remaining cuticle |
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life cycle of ameloblasts |
morphogenic- shape if crown, cusps, DEJ organization- histodifferentation formative- matrix formation maturative- mineralization of matrix protective- by the REE from resorption desmolytic- proteolytic enzymes |
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Teeth microscopic structure |
made up of enamel rods that extend from DEJ toward outer surface of enamel -rods perpendicular to DEJ -each enamel is segmented -each rod encased in rod sheath and held together by interrod substance hydroxyappetite |
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hydroxyapatite |
96% inorganic mineral substance which is in the form of tightly packed crystals that fill the loose organic matrix |
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perikymata |
fine line and ridges seen on enamel |
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mamelons |
on newly emerged incisors usually three prominences along the incisal edge |
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enamel cuticle |
envelops crown of tooth nasmyth membrane primary secondary |
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primary enamel cuticle |
product of ameloblasts mineralizes |
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secondary enamel cuticle |
product of REE minerlizes |
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bands of hunter |
schreger alternating broad and light bands that are perpendicular to DEJ result of curvature of enamel rods |
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lines of retzius |
narrow brownish lines seen in cervical area shallow depression |
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enamel lamallae |
microscopic separations in enamel |
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enamel hypoplasia |
white spots and pits disturbance in matrix formation -systemic -localized -hereditary amelogenesis imperfecta |
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enamel hypocalcification |
disturbance in calcification dentinogenesis imperfecta grey or brown teeth |
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dentinogenesis |
under the influence of ameloblasts the peripheral cells of dental papillae histodifferentiate into odontoblasts |
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phases of dentinogenesis |
predentin formation (matrix formation) mineralization |
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dentin |
mineralized tissue harder than cementum |
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dentin composition |
70% inorganic 20% organic 10% water |
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structure of dentin |
organic matrix: korff's fibers and ground substance consisting of mucopolysaccharides matrix is formed first then minerals in solution are deposited in the cementing substance inorganic: calcium phosphate - hydroxypatite crystals |
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korff's fibers |
collagen fibers |
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dentinal tubules |
perforated holes in dentin. contain cell processes of odontoblasts lie close together and extend from pulp to DEJ outer ends divide into branches a cell process which is the cytoplasm of an odontoblasts occupies each dentinal tubule |
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odontoblasts |
found in pulp next to DEJ -form organic matrix of dentin -nucleus of odontoblasts remain in pulp surrounded by part of cytoplasm -remainder of cytoplasm extends odontoblastic proceses |
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odontoblastic processes |
cytoplasm of odontoblast extend to dentinal tubules |
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enamel spindles |
process that crosse over into the enamel |
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predentin |
dentinoid young teeth have layer of dentin adjacent to pulp that is less mineralized than the rest of dentin |
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interglobular dentin |
spots of unmineralized dentin just inside DEJ |
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Tomes's granular layer |
bands of spots of unmineralized dentin immediately beneath cementum |
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types of dentin |
reparative secondary sclerotic |
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reparative dentin |
older teeth along pulpal wall aging |
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secondary dentin |
produced in response to caries, restorative procedures, or other damaging stimuli |
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sclerotic dentin |
odontoblastic processes have degenerated dentinal tubules have become filled with calcium salts |
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importance of dentin structure |
influences pattern of carious lesion and speed at which it progresses to destroy the tooth structure |
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cariology |
caries penetrates the enamel by demineralizing the enamel by acids that the cariogenic bacteria produce caries producing bacteria bacteria enter tubules and destroy odontoblastic processes processes are being destroyed the dentin continues to demineralized leaves behind soft organic matrix reason caries is soft |
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cementogenesis |
origin and formation of cementum |
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cementum location |
layer of mineralized tissue that makes up surface of root overlies and is attached to root dentin 0.05 thick around cervical area and thicker in apical area |
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arrangements with enamel |
meets enamel lies short of enamel leaving dentin exposed slightly overlaps enamel (common) |
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cementum functions |
provide medium by which other parts of periodontium are attached to tooth without it tooth would not be retained in socket protect underlying dentin -root dentin will resorb if the more resistant cementum is lost mends tissue of root fracture -cementoblasts from PDL will form cementum at fracture compensates for attrition by forming cementum at apical and furcations areas of tooth |
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composition of cementum |
similar to enamel, dentin, bone 50% inorganic mineral material 50% organic matrix may contains cells called cementocytes void of blood vessels and nerves approx same hardness of bone |
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structure of cementum |
organic matrix- fine collagen fibrils held together by ground substance which become calcified produced by cementoblasts -cementoblasts located in PDL next to cementoid layer may contain whole cells (dentin only contains process cells) formed in layers as a result appositional growth lines can be seen -oldest layers next to root dentin and newest is adjacent to PDL |
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cementoid |
newest layer of organic matrix |
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cementocytes |
cementoblasts that become surrounded by organic matrix that they produce |
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cementoblasts are connected to each other by |
projections of their cytoplasm |
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lacuna |
space occupied by body of cementocyte |
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canaliculi |
space occupied by cytoplasmic processes -most are directed toward PDL |
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types of cementum |
cellular acellular |
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cervical cementum is |
thin and has no cementocytes |
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apical cementum is |
thick and contains few cementocytes |
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sharpey's fibers |
visible in cementum ends of fiber bundles of PDL that have become embedded in cementum |
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clinical importance of cementum |
part of mechanism that attaches the tooth to the socket it is continually produced by cementoblasts in PDL cementum at root apex compensates for loss of enamel due to attrition repairs damage to root -replace root that have been resorbed due to injury |
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hypercementosis |
cementum found in excessive amounts |
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cementicles |
small bodies of cementum found in PDL
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pulp |
close physiologic relationship with dentin occupies pulp chamber, root canal, connects with PDL at apical foramen originates from dental papilla (mesenchyme) |
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in pulp the cells of mesenchyme differentiate into |
fibroblasts and odontoblasts fibroblasts forms and maintains intercellular substance of pulp odontoblasts form dentin |
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pulp composition |
only non mineralized tissue made up of cells, intercellular substance, tissue fluid |
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cells in pulp consists of |
mostly fibroblasts specialized cells -histocytes -undifferentiated mesenchymal cells -odontoblasts |
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intercellular substance in pulp consists of |
ground substance fibrous substance |
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components of pulp |
fibroblast histocytes odontoblasts |
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histocytes |
undifferentiated mesenchymal cells are located throughout pulp near the capillaries respond to pulp injury- will differentiate into cells of inflammatory response |
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lymphatic vessels within pulp
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some |
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innervation |
nerve fibers have axons on odontoblasts along odontoblastic processes that extend into tubules |
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zones of pulp |
odontoblastic free rich |
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odontoblastic zone |
functions to form dentin is the first line of defense outer most layer next to predentin layer contains cell bodies of odontoblasts |
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cell free zone |
buffer to allow cells to move in and out without obstruction contains no cells |
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cell rich zone |
considered cell reservoir cells are capable of moving through cell free zone to site of odontoblastic injury differentiate to odontoblasts when they reach the odontoblastic zone will form reparative dentin |
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functions of pulp
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formative sensory nutritive defensive |
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formative function |
odontoblasts whose nucleus lies within pulp are responsible for formative function produce collagen fibrils and ground substance of dentin |
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sensory function |
sensitive to external stimuli mainly pain -unable to differentiate extremes -pressure and touch due to PDL |
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nutritive function |
receives nutrients from blood stream enters dentinal tubules by odontoblastic processes may be from DEJ to DCJ |
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defensive function
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expressed in several ways inflammatory (sclerotic, reparative) pulp damage -inflammatory response -some cells derived from histocytes and undifferentiated mesenchymal cells -some cells carried to pulp through blood of bone marrow and lymph -inflammation controlled, pulp may produce sclerotic/reparative dentin as response to protect pulp |
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sclerotic dentin |
filling of dentinal tubules with calcium salts creating solid mineralized dentin usually beneath caries lesion retards destruction of dentin |
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reparative |
produced by onto blasts as defense reaction stimulated by production of sclerotic dentin |
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age changes to pulp |
non pathologic continued formation of reparative dentin pulp chamber smaller root canals narrow cells decrease fibrous intercellular substance increased due to decreased cells |
