Podcast
Questions and Answers
What is the primary function of enamel?
What is the primary function of enamel?
- To aid in the formation of dentin
- To produce the color of the tooth
- To provide sensation to the tooth
- To cover and protect the underlying tissues (correct)
When does the formation of enamel start?
When does the formation of enamel start?
- After the tooth has erupted
- When the embryo is 18 weeks (correct)
- During the second year of birth
- During the first year of birth
What is the hardness of tooth enamel on the Knoop hardness scale?
What is the hardness of tooth enamel on the Knoop hardness scale?
- 350-500 KHN (correct)
- 600-700 KHN
- 500-600 KHN
- 200-300 KHN
What is the origin of enamel?
What is the origin of enamel?
What is the percentage of mineral salts in enamel?
What is the percentage of mineral salts in enamel?
What is the compressive strength of tooth enamel?
What is the compressive strength of tooth enamel?
What is the maximum thickness of enamel over the cusps?
What is the maximum thickness of enamel over the cusps?
What is the tensile strength of tooth enamel?
What is the tensile strength of tooth enamel?
What is the percentage of organic content in tooth enamel?
What is the percentage of organic content in tooth enamel?
What is the reason for the yellowish color of some teeth?
What is the reason for the yellowish color of some teeth?
What is the main inorganic constituent of tooth enamel?
What is the main inorganic constituent of tooth enamel?
What is the characteristic of the cervical area of the tooth in terms of enamel thickness?
What is the characteristic of the cervical area of the tooth in terms of enamel thickness?
What is the shape of the Hydroxyapatite crystals in tooth enamel?
What is the shape of the Hydroxyapatite crystals in tooth enamel?
What is the hardness of enamel compared to other calcified tissues?
What is the hardness of enamel compared to other calcified tissues?
What is the arrangement of ions within each unit cell of crystallite in tooth enamel?
What is the arrangement of ions within each unit cell of crystallite in tooth enamel?
What is the approximate percentage of lipid content in tooth enamel?
What is the approximate percentage of lipid content in tooth enamel?
What is the process of forming enamel on teeth during tooth development?
What is the process of forming enamel on teeth during tooth development?
What is the composition of the organic matrix of enamel?
What is the composition of the organic matrix of enamel?
What percentage of enamel proteins are amelogenins?
What percentage of enamel proteins are amelogenins?
What is the function of amelogenins in enamel formation?
What is the function of amelogenins in enamel formation?
What is the characteristic of the N-terminal domain of amelogenins?
What is the characteristic of the N-terminal domain of amelogenins?
What is the stage of tooth development when amelogenesis begins?
What is the stage of tooth development when amelogenesis begins?
What is the origin of the epithelial enamel organ?
What is the origin of the epithelial enamel organ?
What is the composition of the mineral phase of enamel?
What is the composition of the mineral phase of enamel?
In the organizing/inductive stage, what occurs to the ameloblasts?
In the organizing/inductive stage, what occurs to the ameloblasts?
What happens to the basal lamina supporting the ameloblasts during the secretory stage?
What happens to the basal lamina supporting the ameloblasts during the secretory stage?
What characterizes the maturative stage of amelogenesis?
What characterizes the maturative stage of amelogenesis?
Where do the ameloblasts secrete enamel proteins during the secretory stage?
Where do the ameloblasts secrete enamel proteins during the secretory stage?
What is the function of the Tomes' process?
What is the function of the Tomes' process?
Where does the formation of the enamel matrix start?
Where does the formation of the enamel matrix start?
What happens to the ameloblasts during the secretory stage?
What happens to the ameloblasts during the secretory stage?
What is the function of the proximal terminal web?
What is the function of the proximal terminal web?
What is the characteristic of the ameloblasts during the secretory stage?
What is the characteristic of the ameloblasts during the secretory stage?
What is the fate of the ameloblasts after the formation of the enamel matrix?
What is the fate of the ameloblasts after the formation of the enamel matrix?
What is the process of forming enamel on teeth called?
What is the process of forming enamel on teeth called?
In which stage of enamel formation do matrix proteins continue to be secreted by ameloblasts until the entire thickness of enamel is laid?
In which stage of enamel formation do matrix proteins continue to be secreted by ameloblasts until the entire thickness of enamel is laid?
What is the percentage of mineralized enamel formed at the end of the secretory phase?
What is the percentage of mineralized enamel formed at the end of the secretory phase?
What is the function of proteases secreted by ameloblasts in the maturative phase?
What is the function of proteases secreted by ameloblasts in the maturative phase?
What is the composition of mature enamel?
What is the composition of mature enamel?
How many stages are there in the life cycle of ameloblasts?
How many stages are there in the life cycle of ameloblasts?
What is the shape of cells in the morphogenic stage of ameloblast life cycle?
What is the shape of cells in the morphogenic stage of ameloblast life cycle?
Where are Golgi apparatus and centrioles located in ameloblasts during the morphogenic stage?
Where are Golgi apparatus and centrioles located in ameloblasts during the morphogenic stage?
Study Notes
Introduction to Enamel
- Enamel is the hard, vitreous-like substance that covers the outer regions of the tooth crown, protecting the underlying tissues.
- Enamel starts to form when the embryo is 18 weeks old and has an ectodermal origin.
Physical Properties of Enamel
- Enamel is the hardest calcified tissue in the human body, with a high content of mineral salts and a crystalline arrangement.
- It is extremely hard, enabling it to withstand mechanical forces during tooth functioning.
- Enamel thickness varies, with a maximum thickness of over 2.6 mm on cusps/incisal edges and thinning to a knife edge at the neck of the tooth/pit/groove area.
- Enamel color ranges from yellowish white to greyish white, with underlying dentin being yellow.
- Cervical areas have thin enamel, reflecting the yellow color of dentin, while incisal areas have a bluish tinge due to the thin edge of the double layer of enamel.
Mechanical Properties of Enamel
- Hardness: 350-500 KHN
- Compressive strength: 50 x 10^3 psi/ 350 MPa
- Shear strength: 13 x 10^3 psi/ 90 MPa
- Tensile strength: 1.5 x 10^3 psi/ 10 MPa (low)
- Abrasion resistance: high
- Modulus of elasticity: 19 x 10^6 psi/ 130 GPa
- Specific gravity: 2.95 (deciduous teeth) and 2.97 (permanent teeth)
- Permeability: refractive index 1.655 (in comparison, porcelain is 1.5 and quartz is 1.54)
Chemical Properties of Enamel
- Inorganic content: 96% (calcium hydroxyapatite)
- Organic content: 4% (water, proteins, carbohydrates, and lipids)
- Minor constituents: fluoride, zinc, silver, aluminum, barium, copper, nickel, selenium, titanium, vanadium, and lead.
Enamel Proteins
- Enamel proteins are made up of non-collagenous proteins only.
- Amelogenins (90%): heterogeneous group of low molecular weight proteins.
- Non-amelogenins (10%): enamelin, ameloblastin (amelin or sheathlin), and tuftelin.
- Amelogenins regulate growth and thickness.
Enamel Formation (Amelogenesis)
- Amelogenesis begins during the advanced bell stage of tooth development after dentinogenesis.
- Enamel formation occurs in two phases: secretory and maturative.
- During the secretory phase, ameloblasts secrete enamel proteins and form the organic matrix.
- During the maturative phase, the organic matrix is mineralized, and the enamel crystallite forms and grows in length.
Life Cycle of Ameloblasts
- According to function, the life span of cells of the inner enamel epithelium is divided into six stages: morphogenic, organizing/inductive, formative/secretory, maturative, protective, and desmolytic.
- During the morphogenic stage, the cells are low and cuboidal, resting on the basement membrane.
- During the formative/secretory stage, ameloblasts become elongated, and the Golgi apparatus and centrioles are located in the proximal end of the cell.
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Description
Test your knowledge of enamel, the hard outer layer of tooth crowns, including its physical and chemical properties, formation, and functions. Learn about the structure, thickness, color, hardness, strength, and resistance of enamel.
