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Questions and Answers
What is the primary function of enamel?
What is the primary function of enamel?
At what developmental stage does enamel formation begin?
At what developmental stage does enamel formation begin?
What feature contributes to the hardness of enamel?
What feature contributes to the hardness of enamel?
What is the maximum thickness of enamel over molars?
What is the maximum thickness of enamel over molars?
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What are the major secretory forms of amelogenins identified?
What are the major secretory forms of amelogenins identified?
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What color range does enamel typically exhibit?
What color range does enamel typically exhibit?
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On the Mohs hardness scale, where does tooth enamel rank?
On the Mohs hardness scale, where does tooth enamel rank?
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Which phase of enamel formation occurs after dentinogenesis?
Which phase of enamel formation occurs after dentinogenesis?
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Which protein is categorized as a nonamelogenin?
Which protein is categorized as a nonamelogenin?
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What is the tensile strength of enamel approximately?
What is the tensile strength of enamel approximately?
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What is the primary function of matrix vesicles during the enamel formation process?
What is the primary function of matrix vesicles during the enamel formation process?
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Which area of the tooth usually has the thinnest enamel?
Which area of the tooth usually has the thinnest enamel?
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What characteristic is notable regarding the N-terminal domain of amelogenins?
What characteristic is notable regarding the N-terminal domain of amelogenins?
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What is the specific gravity of enamel in permanent teeth?
What is the specific gravity of enamel in permanent teeth?
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What percentage of enamel's chemical composition is inorganic?
What percentage of enamel's chemical composition is inorganic?
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During which stage of tooth development does amelogenesis begin?
During which stage of tooth development does amelogenesis begin?
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Which of the following is a major inorganic constituent of enamel?
Which of the following is a major inorganic constituent of enamel?
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What is the approximate lipid content in the organic matrix of enamel?
What is the approximate lipid content in the organic matrix of enamel?
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Which molecule surrounds the hydroxyl group in hydroxyapatite?
Which molecule surrounds the hydroxyl group in hydroxyapatite?
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What type of proteins make up the organic matrix of enamel?
What type of proteins make up the organic matrix of enamel?
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What is the primary role of fluoride in enamel composition?
What is the primary role of fluoride in enamel composition?
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What is the primary component that ameloblasts secrete during the secretory phase?
What is the primary component that ameloblasts secrete during the secretory phase?
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During which phase does the enamel crystallite grow rapidly in length?
During which phase does the enamel crystallite grow rapidly in length?
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What happens to the mineral content of enamel during the maturation phase?
What happens to the mineral content of enamel during the maturation phase?
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What type of cells are present in the morphogenic stage of ameloblast life cycle?
What type of cells are present in the morphogenic stage of ameloblast life cycle?
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What is the main function of proteases secreted by ameloblasts?
What is the main function of proteases secreted by ameloblasts?
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Which stage of the ameloblast life cycle is characterized by organizing and inductive functions?
Which stage of the ameloblast life cycle is characterized by organizing and inductive functions?
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What characterizes the cytoplasm of cells in the morphogenic stage?
What characterizes the cytoplasm of cells in the morphogenic stage?
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Which portion of the ameloblast contains the highest concentration of organelles during the organizing stage?
Which portion of the ameloblast contains the highest concentration of organelles during the organizing stage?
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What initiates the process of amelogenesis?
What initiates the process of amelogenesis?
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Which process is characterized by the modulation of 'ruffle ended' and 'smooth ended' ameloblasts?
Which process is characterized by the modulation of 'ruffle ended' and 'smooth ended' ameloblasts?
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What is the function of the Reduced Enamel Epithelium (REE)?
What is the function of the Reduced Enamel Epithelium (REE)?
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In which stage of enamel development do ameloblasts cease to be arranged in a well-defined layer?
In which stage of enamel development do ameloblasts cease to be arranged in a well-defined layer?
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What characterizes the first site of enamel secretion during the secretory stage?
What characterizes the first site of enamel secretion during the secretory stage?
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What happens during the desmolytic stage?
What happens during the desmolytic stage?
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What is the primary outcome of the maturative stage in enamel development?
What is the primary outcome of the maturative stage in enamel development?
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What structure contains secretory granules and small vesicles during enamel development?
What structure contains secretory granules and small vesicles during enamel development?
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Study Notes
Enamel Structure and Properties
- Enamel is a hard, vitreous substance covering the outer regions of the tooth crown.
- It acts as a protective cap for underlying tissues.
- Enamel is the hardest calcified tissue in the human body, due to high mineral content and a crystalline structure.
- It withstands mechanical forces during tooth function.
- Enamel thickness varies; thickest over cusps/incisal edges, thinnest at the neck of the tooth.
- Incisors have 0 to 2 mm thickness, and molars have 2.6 mm thickness.
- Enamel is translucent, with underlying dentin appearing yellow, resulting in tooth colours ranging from yellowish white to greyish white.
- Enamel in the cervical areas reflects the yellow color of the dentin.
- Incisal areas exhibit a bluish tinge, due to the nature of the thin double enamel layer.
- Enamel comprises 96% inorganic material.
- Enamel comprises 4% organic material and water.
- The inorganic material is predominantly calcium phosphate crystals (hydroxyapatite).
- These hydroxyapatite crystals have a hexagonal structure.
- Enamel contains minerals like fluoride, zinc, and trace elements like silver, aluminum, barium, copper, nickel, selenium, titanium, vanadium and lead.
- Enamel proteins are non-collagenous proteins, including amelogenins (90%) and non-amelogenins (10%).
- Amelogenins, in the form of 25kDa and 23kDa forms, are major secretory enamel proteins. These have tyrosine-rich N-terminal domains and leucine-rich central parts.
- Non-amelogenins include proteins like enamelin, amelin (or sheathlin), and tuftelin.
Enamel Formation (Amelogenesis)
- Amelogenesis is the process of enamel formation on teeth, initiating during the advanced bell stage of tooth development, following dentinogenesis.
- Enamel formation occurs in two phases: secretory and maturative phases.
- The secretory phase involves secretion of proteins, forming the base for the mineral structure.
- The maturative phase involves resorption of proteins and water, and simultaneous secretion of mineral ions.
- Matrix vesicles from ameloblasts support the formation of crystal structure within the organic matrix.
- Ameloblasts continue secreting proteins until the entire enamel thickness is formed.
- Enamel crystallites rapidly grow in length within the organic matrix.
- Enamel formation also proceeds via two sites on enamel.
- The first site is adjacent to the proximal parts of ameloblasts .
- The second site is on the surface of Tomes' process, and later fills the pits in the enamel with the matrix .
- The formation of Tomes' process occurs as ameloblasts migrate away from the dentin surface.
Enamel Life Cycle (Ameloblasts)
- The ameloblasts, responsible for enamel formation, have a life cycle divided into six stages—morphogenic, organizing/differential, formative/secretory, maturative, desmolytic, and protective.
- Morphogenic stage—early bell stage with low cuboidal cells on the basement membrane and separated from the dental papilla.
- Organizing/inductive stage—late bell stage with elongated ameloblasts.
- Formative/secretory stage—increased number of ameloblasts and their organelles.
- Maturative stage—ameloblasts are fully matured and form the enamel maturation process.
- Desmolytic stage—the REE (reduced enamel epithelium) proliferates and induces atrophy of CT from oral epithelium.
- Protective stage—the enamel is fully formed, and ameloblasts arrange into a well-defined layer.
Enamel and Ameloblasts
- The reduced enamel epithelium (REE) acts as a protective covering for the mature enamel, separating it from the connective tissues until tooth eruption.
- Connective tissue contacting the enamel may cause enamel resorption or its covering by cementum.
- REE may present premature degeneration, which can prevent tooth eruption.
- During desmolysis, epithelial cells elaborate enzymes to destroy connective tissue fibres.
Additional Information
- The secretory ameloblasts form both prismatic and interprismatic enamel structures.
- Tooth enamel ranks 5 on the Mohs hardness scale.
- Enamel's compressive strength is 50x10^3 psi or 350 MPa.
- The shear strength of enamel is 13x10^3 psi or 90 MPa.
- Tensile strength is 1.5x10^3 psi/10 MPa (low).
- Enamel's modulus of elasticity is high – 19x10^6 psi or 130 GPa.
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Description
Explore the unique properties and structure of tooth enamel, the hardest substance in the human body. This quiz covers its composition, thickness variations, and how it contributes to tooth color. Test your knowledge on this essential dental component!
