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137 Cards in this Set
- Front
- Back
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During the fifth week of development, which of the following thickens to form the dental lamina?
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Oral epithelium (ectoderm)
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Around the eighth week of development what induces the development of tooth buds at ten locations in the upper and lower dental lamina?
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Mesenchymal neural crest cells
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What happens in the bud stage of development?
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Dental lamina grows into the mesenchyme in the shape of a bud
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What happens during the ninth week of development?
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Tooth bud differentiates into a cap-shaped enamel organ extending from the dental lamina
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What develops in the ninth week to separate the gum from the lip/cheek?
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Development of a vestibular lamina
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What happens during the cap stage of development?
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Unequal growth of epithelial cells grows down to form a concavity around the mesenchyme, forms dental papilla
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When mesenchymal cells encircle the enamel organ what is formed?
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Dental sac
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At the end of the cap stage the tooth germ is complete and consists of what?
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Enamel organ
Dental Sac Dental papilla |
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What is the enamel organ derived from?
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Oral epithelium (ectoderm)
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What are the four layers of the enamel organ?
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1. outer enamel epithelium
2. inner enamel epithelium 3. Stratum intermedium 4. Stellate reticulum |
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What does the enamel organ eventually give rise to?
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Enamel and Hertwig's epithelial root sheath
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Surrounds the developing tooth germ and will give rise to the cementum, PDL, and alveolar bone proper
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Dental Sac
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Gives rise to the dentin and dental pulp
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Dental Papilla
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What do the outer layer of cells of the dental papilla differentiate into?
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Odontoblasts
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What do the dental sac and dental papilla arise from?
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Mesenchymal neural crest
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The oldest enamel or first enamel deposited is located where?
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At the DEJ under the cusp tip
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Hardest tissue in the body, richest in calcium, mineralized and acellular, and of ectodermal origin
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Enamel
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What is the breakdown of enamel components
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96% inorganic minerals
1% organic materials 3% water |
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What does the organic matrix of protein mainly consist of?
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Protein rich in proline
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What is the fundamental morphologic unit of enamel
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Enamel rod or prism
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Each enamel rod is formed in increments by a single enamel forming cell called..
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Ameloblasts
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Where are enamel rods directed and how many of them exist in a given crown?
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Extends from DEJ to outer surface of the crown
5 to 12 million rods in a crown |
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What happens to the size of the diameter of the enamel rods as they flare outward from the DEJ
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Increase in diameter from 4 to 8 microns
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What do the ameloblasts lose once the crown has been completed?
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Functional ability / power of regeneration
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What are the characteristics that enamel lacks?
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Metabolism
A way to fight bacterial invasion A nerve supply |
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What is a good thermal insulator?
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Enamel
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Crystalline calcium phosphate which is the largest mineral constituent (90-95%) of the inorganic matter in enamel
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Hydroxyapatite
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What are minor inorganic constituents of enamel?
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Fluoride and zinc
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The organic matrix and water in the enamel _____ over time.
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Decreases (Inorganic increases)
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Organic potion of enamel does not contain collagen but instead it contains...
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Amelogenins and Enamelins
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What is the role of Amelogenins and enamelins?
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Aid in the development of enamel as a framework support and other mechanisms
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Even though it is brittle what is the amount of pressure enamel can endure?
Why? |
100,000 lbs/in (2)
layers of dentin and periodontium form a cushion |
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What kind of membrane does enamel have which allows water and certain ions to pass?
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Selectively Permeable Membrane
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An elongated odontoblastic process which traverses the DEJ from the dentin into the enamel is known as what?
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Enamel Spindle
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As ameloblasts retreat in incremental steps, they create an artifact in the ena,el known as what?
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Lines of Retzius
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When the lines of retzius terminate at the tooth surface they create tiny valleys on the tooth surface that travel circumferentially around the crown known as what?
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Perikymata
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Most obvious line of retzius that marks the division between enamel formed before birth and that produced after birth. Found in deciduous teeth and cusps of permanent molars
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Neonatal line
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How are enamel rods aligned to the DEJ?
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Traverses through the thickness of the enamel perpendicular to the DEJ
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The alternating light and dark lines seen in dental enamel that begin at the DEJ and end before they reach the enamel surface. represent areas of enamel rods cut in cross section dispressed between areas of rods cut longitudinally
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Hunter-Scheger bands
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Fan-shaped, hypocalcified structures of enamel rods that project from DEJ into enamel proper (function unknown)
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Enamel tufts
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Elongated odontoblastic processes that traverse the DEJ from the underlying odontoblasts. may serve as pain receptors
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Enamel spindles
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Defects in the enamel resembling cracks or fractures which traverse the entire length of the crown from the surface of the DEJ. Contain mostly organic material and may provide an area for decay to enter.
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Enamel Lamellae
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What is the sequence of events in the histogenesis of a tooth?
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1. Elongation of inner enamel cells; causes mesenchymal cells to differentiate into odontoblasts
2. Odontoblastic differentiation 3. Deposition of first layer of Dentin 4. Deposition of first layer of enamel |
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The rope like grouping of fibers in the periphery of the pulp that seem to have something to do with the formation of the dentin matrix
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Forff's Fibers
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The cells of which layer of the enamel organ will differentiate into ameloblasts?
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Inner enamel epithelium
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Outer layer of the enamel organ
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Outer enamel epithelium
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Innermost cellular layer of the enamel organ. Cells will become ameloblasts and produce enamel. layer essential to dentin formation once enamel is produced
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Inner Enamel Epithelium
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Area which lies immediately lateral to the inner enamel epithelium. Layer of cells seems to be essential to enamel formation.
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Stratum Intermedium
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Area that is central to the core and fills the bulk of the enamel organ. Contains a lot of intercellular fluid which is lost just prior to enamel deposition
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Stellate Reticulum
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After enamel is formed the initial four layers fuse to form what?
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Reduced enamel epithelium
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What are some important uses for the Reduced enamel epithelium?
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Important in the formation of Dentogingival junction
Forms initial junctional epithelium |
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Soft tissue component of the tooth. Connective tissue originating from mesenchyme of the dental papilla. formative organ of the dentin and its source of nutrition and maintenance
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Dental pulp
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Located in the pulp chamber and pulp horns (crown portion of tooth)
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Coronal pulp
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Located in the pulp canals (root portion of the tooth)
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Radicular pulp
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Communicates with PDL
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Apical foramen
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Extends from the pulp canal through the root dentin to the PDL
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Accessory Canals
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The pulp proper which contains large nerves and vessels. This area is lined peripherally by a specialized odontogenic area which has 4 zones.
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Central zone
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What are the individual sections of the central zone?
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Pulpal zone
Cell-rich zone Cell free zone/zone of weil Odontoblastic layer |
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What is located within the pulpal and cell-rich zones?
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Fibroblasts
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What resides in the Cell-free zone/
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capillary and nerve plexus
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Contains odontoblasts and lies next to the predentin and mature dentin.
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Odontoblastic layer of the central zone of the dental pulp
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What is always an indication of partial necrosis?
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Cold relieves pain
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The organic component of dentin is primarily what?
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collagen
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Specialized connective tissue making up the bulk of the tooth and extending almost the entire length. Hard, elastic.
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Dentin
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Contains odontoblasts and lies next to the predentin and mature dentin.
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Odontoblastic layer of the central zone of the dental pulp
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What is always an indication of partial necrosis?
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Cold relieves pain
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What are the components of dentin?
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70% inorganic
20% organic 10% water untraceable minerals |
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What is the mineral phase or inorganic component of dentin mostly composed of?
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Calcium hydroxyapatite
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The organic component of dentin is primarily what?
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collagen
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What does dentin have many morphological and chemical characteristics common to?
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Bone although it is more mineralized
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Does dentin have higher tensile or compressive strength?
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Compressive
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Specialized connective tissue making up the bulk of the tooth and extending almost the entire length. Hard, elastic.
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Dentin
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The reason that children are more sensitive to thermal changes than those of an adult is that...
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Newly erupted teeth have larger dental pulps
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What are the components of dentin?
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70% inorganic
20% organic 10% water untraceable minerals |
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What is the mineral phase or inorganic component of dentin mostly composed of?
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Calcium hydroxyapatite
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When does the dental pulp begin to get smaller?
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As root formation is completed
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What does dentin have many morphological and chemical characteristics common to?
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Bone although it is more mineralized
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Does dentin have higher tensile or compressive strength?
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Compressive
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The reason that children are more sensitive to thermal changes than those of an adult is that...
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Newly erupted teeth have larger dental pulps
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When does the dental pulp begin to get smaller?
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As root formation is completed
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Contains odontoblasts and lies next to the predentin and mature dentin.
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Odontoblastic layer of the central zone of the dental pulp
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What is always an indication of partial necrosis?
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Cold relieves pain
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The organic component of dentin is primarily what?
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collagen
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Specialized connective tissue making up the bulk of the tooth and extending almost the entire length. Hard, elastic.
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Dentin
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What are the components of dentin?
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70% inorganic
20% organic 10% water untraceable minerals |
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What is the mineral phase or inorganic component of dentin mostly composed of?
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Calcium hydroxyapatite
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What does dentin have many morphological and chemical characteristics common to?
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Bone although it is more mineralized
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Does dentin have higher tensile or compressive strength?
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Compressive
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The reason that children are more sensitive to thermal changes than those of an adult is that...
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Newly erupted teeth have larger dental pulps
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When does the dental pulp begin to get smaller?
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As root formation is completed
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What is the composition of the pulp?
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Loose connective tissue
Blood vessels, lymph vessels, nerves Cells Ground substance Undifferentiated mesenchymal cells (replaces injured odontoblasts) |
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Stage involves the physiological process of induction. Starts at fifth week. reaction of oral epithelium and mesenchyme to form dental lamina
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Initiation
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Involves process of proliferation. Starts at eighth week. Dental lamina grows into 10 buds per arch. Shape of tooth becomes evident. Formation of enamel organ
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Bud Stage
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Involves proliferation and differentiation by way of morphodifferentiation and histodifferentiation from the ninth week to the tenth week.
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Cap stage
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To change into other shapes
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Morphodifferentiation
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To branch into different tissues
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Histodifferentiation
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What happens at the end of the cap stage?
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Tooth germ is complete and the Enamel organ, the dental papilla and the dental sac are present
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differentiation occurs resulting in four different cell types in the bell-shaped enamel organ. Dental sac increases in collagen fibers?
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Bell Stage
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Cells that were differentiated into specific tissue-forming cells that begin to deposit the specific dental tissues.
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Apositional stage
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mineralization begins at the DEJ and continues until total development is accomplished, taking approx. 2 years to complete
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Maturation stage
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what is the primary function of the pulp?
What cell is responsible for this? |
Form dentin
odontoblasts |
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What is the nutritive component of the pulp?
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Keeps organic components of surrounding mineralized tissue supplied with moisture
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What is the sensory component of the pulp?
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extremes in temp, pressure, and trauma are perceived as pain
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What is the Protective component of the Pulp?
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Formation of reparative or secondary dentin.
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Why is pulp capping more successful in younger teeth?
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Large Apical foramen
Contains more cells Very vascular Fewer fibrous elements More tissue fluid |
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The dental tissue that most closely mimics bone is what?
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Cementum
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Bone-like ridgid connective tissue. Anchors the PDL. Classified into Acellular and Cellular components
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Cementum
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What are the function of the cementum?
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Provides anchorage for sharpey's fibers
Compensate loss of occlusal tooth surface with apical deposition Protects root from resorption Reparative function, allows connective tissue reattachment |
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How does cementum differ from enamel?
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It has collagen and has cellular components
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Peripheral layer of developing cementum that is uncalcified
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Cementoid
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Cementum has more _____ than alveolar bone.
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resistance to resorption
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How is cementum formed?
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cementoblasts from the PDL
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Even though it resembles bone what components does it not have?
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Haversian systems
Blood vessels (avascular) No nerve innervation |
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What is the percentage of components of cementum?
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50% inorganic (hydroxyapatite)
40% organic 10% water |
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Contains no cells; usually predominates on the coronal two-thirds of the root. Thinnest at CEJ
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Acellular cementum
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Contains cementoblasts, inactive cementocytes, fibroblasts from the PDL and cementoclasts. Occurs more frequently on the apical third of the root. usually thickest to compensate for attritional wear of occlusal/incisal surface and passive eruption of the tooth.
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Cellular cementum
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Dentin which is seen as a result of aging or advancing dental caries and calcifies and obliterates dentinal tubules blocking access of irritants to the pulp
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Sclerotic Dentin
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Areas with empty dentinal tubules
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Dead tracts
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When dead tracts become completely filled with mineral they are known as ...
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Blind Tracts
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Deposited locally in response to injury. Forms rapidly (3.5 microns per day). dentinal tubules irregular, and sometimes odontoblastsare trapped producing osteodentin
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Reparative dentin
(Secondary, reactive, tertiary) |
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Dentin formed during development. Forms rapidly and ends when root formation is complete
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Primary Dentin
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Deposited after completion of the tooth. Slower developingand less mineralized. Deposition not associated with stress. Narrows pulp chamber and root canals with age. less permeable.
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Secondary dentin
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What defines the junction between the primary and secondary dentin?
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Sharp change in the direction and density of dentinal tubules
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The most mineralized dentin is seen where?
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Peritubular dentin
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peripheral portion of dentin adjacent to enamel or cementum consisting of Korff's fibers. First layer of dentin deposited
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mantle dentin
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What is the remaining primary dentin after mantle dentin?
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Circumpulpal dentin
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What is the small layer that is sandwhiched between mantle and circumpulpal dentin?
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Globular Dentin
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Lines the dentinal tubules. most mighly mineralized dentin
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Intratubular (peri) dentin
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Surrounds the intratubular dentin, and is less mineralized
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Intertubular Dentin
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imperfectly calcified matrix of dentin situated between the calcified globules near the periphery of the dentin
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Interglobular dentin
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The calcification of a tooth begins at which structure?
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DEJ
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How does the dentinogenesis begin?
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Odontoblasts lay down a collagen matrix moving from DEJ inwards toward the pulp. Most recent is always adjacent to the pulp
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When is the morphology of the DEJ determined?
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Bell stage
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Where is the oldest enamel located?
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At the DEJ underlying a cusp
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The application of excessive heat to a tooth results in pain because ...
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All stimuli to the pulp results in pain sensation
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What is the only type of nerve ending in the pulp?
Where are these located? |
free nerve ending
plexus of Raschkow |
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What type of nerve fibers are within the pulp?
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Myelinated - sensory
Unmyelinated - motor These are afferent and sympathetic |
