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Questions and Answers
What is the width of the 'thread' formed by the coalescence of HA crystallites in enamel prisms?
What is the width of the 'thread' formed by the coalescence of HA crystallites in enamel prisms?
- 10-15μm
- 20-25μm
- 1-2μm
- 5-7μm (correct)
What separates enamel prisms from surrounding interprismatic enamel?
What separates enamel prisms from surrounding interprismatic enamel?
- Cementum
- Prism sheath (correct)
- Dentinal tubules
- Periodontal ligament
What is the primary function of enamel?
What is the primary function of enamel?
- To produce a radiant smile
- To enhance the color of the tooth
- To mitigate tooth wear and protect the underlying dentine (correct)
- To provide a strong foundation for the tooth
How many ameloblasts regulate the growth of each enamel prism?
How many ameloblasts regulate the growth of each enamel prism?
What is the color of healthy enamel?
What is the color of healthy enamel?
Why are ground thin sections needed to study enamel's structure?
Why are ground thin sections needed to study enamel's structure?
What is the term used to describe the clusters of millions of HA crystallites in enamel?
What is the term used to describe the clusters of millions of HA crystallites in enamel?
What type of light microscopy is used to visualize the direction of enamel prisms?
What type of light microscopy is used to visualize the direction of enamel prisms?
What is the chemical formula of hydroxyapatite?
What is the chemical formula of hydroxyapatite?
What is the thickness of enamel over the cusps of permanent teeth?
What is the thickness of enamel over the cusps of permanent teeth?
What is the term used to describe the enamel surrounding the prisms?
What is the term used to describe the enamel surrounding the prisms?
What is the characteristic of mature enamel's organization?
What is the characteristic of mature enamel's organization?
What percentage of mature enamel is composed of inorganic material?
What percentage of mature enamel is composed of inorganic material?
What is the main component of the inorganic material in mature enamel?
What is the main component of the inorganic material in mature enamel?
Who wrote the first English dentistry textbook in which the term 'enamel' was first used?
Who wrote the first English dentistry textbook in which the term 'enamel' was first used?
What is the function of the 'hard periosteum' in enamel, as described by Charles Allen?
What is the function of the 'hard periosteum' in enamel, as described by Charles Allen?
What is the characteristic of mature enamel in terms of cell and blood vessel presence?
What is the characteristic of mature enamel in terms of cell and blood vessel presence?
What is the term used by Charles Allen to describe the natural enamel of the tooth?
What is the term used by Charles Allen to describe the natural enamel of the tooth?
What is the term used to describe the crossing of neighbouring groups of prisms?
What is the term used to describe the crossing of neighbouring groups of prisms?
What are the dark bands formed by prisms cut longitudinally in section called?
What are the dark bands formed by prisms cut longitudinally in section called?
What is the primary function of Hunter-Schreger bands in tooth enamel?
What is the primary function of Hunter-Schreger bands in tooth enamel?
What is the term used to describe the incremental variations in prism thickness that occur from daily variations in enamel production?
What is the term used to describe the incremental variations in prism thickness that occur from daily variations in enamel production?
What is the purpose of radially oriented prisms in tooth enamel?
What is the purpose of radially oriented prisms in tooth enamel?
What is the term used to describe the region where enamel and dentine meet?
What is the term used to describe the region where enamel and dentine meet?
What appears as horizontal lines along the surface of a newly erupted tooth crown?
What appears as horizontal lines along the surface of a newly erupted tooth crown?
What is the result of a subtle change in thickness and direction of enamel prisms that occurs at birth?
What is the result of a subtle change in thickness and direction of enamel prisms that occurs at birth?
What is found within the enamel and dentine of all teeth that were at the appropriate stage of development when a person is born?
What is found within the enamel and dentine of all teeth that were at the appropriate stage of development when a person is born?
What is the forensically important use of neonatal line?
What is the forensically important use of neonatal line?
What is the interface between the enamel and dentine?
What is the interface between the enamel and dentine?
What type of teeth have a neonatal line?
What type of teeth have a neonatal line?
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Study Notes
Enamel Basics
- Enamel is harder than underlying dentine, creating mechanical challenges
- Enamel is more radiopaque (lighter) than dentine and bone due to its high mineral content
- Enamel's primary function is to mitigate tooth wear and protect the underlying dentine
- Healthy enamel is translucent, grey-white to light yellow in colour
- Enamel is 2.5mm thick over cusps of permanent teeth (1.3mm in deciduous teeth), tapering to a thin layer along the cervical edge
Enamel Structure
- Mature enamel is hierarchically organised (multiple levels of crystal groupings)
- Basic building block: hydroxyapatite (HA) crystallites (Ca10(PO4)6(OH)2) which can include Mg, F, CO32-
- HA crystallites are grouped into enamel prisms and interprismatic enamel
- Prisms (or "rods"): clusters of millions of HA crystallites coalesced into a ~5-7μm wide "thread", spanning the entire thickness of enamel
- Prisms are separated from surrounding interprismatic enamel by the prism sheath
Prism Patterns
- The crossing of neighbouring groups of prisms is called prism decussation
- Prism decussation creates Hunter-Schreger bands which mitigate and deflect the paths of expanding cracks
- Radially oriented prisms maximise the strength of each prism relative to occlusal load
Enamel Features
- Enamel contains other distinctive features, including:
- Enamel cross-striations (incremental lines)
- Striae of Retzius
- Perikymata
- Neonatal line (a particular type of stria of Retzius that corresponds to the physiological stress of being born)
- Enamel-Dentine Junction (EDJ)
- Enamel tufts
- Enamel lamellae
- Enamel spindles
- Incremental lines
Other Facts
- Enamel was named by Charles Allen in the first English dentistry textbook (1685-87)
- Mature enamel is acellular and avascular
- Enamel is extremely mineralised: 96% inorganic material (hydroxyapatite), 4% organic material and water
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