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19 Cards in this Set

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  • Back
Question:
What are the physical and chemical characteristics of Mature Enamel?
Answer:
- most higly mineralized biological tissue
- translucent
- semipermeable
- inorganic component made of HYDROXYAPATITE
- organic component made of AMELOGENIN (TRAP) and other proteins
Question:
Describe Enamel Rods.
Answer:
- basic unit of enamel
- consists of HYDROXYAPATITE CRYSTALS
- consists of INTERRODS and ROD SHEATHS
- rod structure is absent immediately adjacent to dentin and enamel surface
- rod diameter increase towards enamel surface
- rods move in undulating (wavy) courses and are perpindicular to dentinal surfaces and bend towards cusp tip
Question:
What is an interrod?
Answer:
- occurs in enamel rods
- the area surounding the rod where crystals are oriented in different directions from those rods
Question:
What is a rod sheath?
Answer:
- occurs in enamel rods
- the interface (or border) between the rod and interrod
- contains highest protein content
Question:
Describe the 2 theories of rod structures.
Answer:
1. KEYHOLE SHAPE
- traditional but INVALID theory
- theory ignores the changing orientation of crystals in the interrod region

2. CYLINDRICAL ENAMEL ROD + INTERROD SUBSTANCE = keyhole shape
Question:
What are the 4 types of incremental lines?
Answer:
1. Striae of Retzius
2. Neonatal line
3. Cross Striations
4. Perikymata
Question:
Describe the Striae of Retzius.
Answer:
- incremental growth lines
- found primarily on permanent teeth
- less evident in decidous teeth
- result of a constriction of Tomes' process coupled with an increased production of interrod enamel
Question:
Describe the Neonatal Line.
Answer:
- an exaggeration of Stria of Retzius
- results from physiological changes that occur at birth
Question:
Describe cross striations.
Answer:
- results from daily changes in secretory activity by AMELOBLASTS
- 4 micrometers of enamel formed per day
Question:
Describe perikymata.
Answer:
- surface irregularities that represent the termination of Striae of Retzius
- they are horizontal bands that encircle the tooth crown but are not found on occlusal surfaces
Question:
Describe Hunter-Schreger bands.
Answer:
- an OPTICAL PHENOMENON created by changes in rod orientation
- appears are alternating light and dark bands
Question:
Describe Gnarled Enamel.
Answer:
- disarrayed ENAMEL RODS present at CUSP TIPS due to crowding and twisting of the rods in a small area
Question:
Describe Enamel Tufts.
Answer:
- small branching defects found at the DEJ that project into the enamel
- contain more enamel protein than surrounding enamel
- no clinical significance
Question:
Describe Enamel Lamellae.
Answer:
- prominent linear enamel defect
- starts at tooth surface and sometimes penetrate DEJ
- contain high enamel protein and material from oral cavity
- no clinical significance
Question:
Describe Enamel Spindles.
Answer:
- short linear enamel defect
- found at the DEJ and extend into enamel
- more prevalent at cusp tips
- formed by entrapment of ODONTOBLASTS PROCESSES between AMELOBLASTS before and during amelogenesis
Question:
What 5 things can occur to enamel through age?
Answer:
1. attrition
2. discoloration
3. reduced permeability
4. changes in surface structure
5. modification of surface layer
Question:
Describe the clinical implications of fluoridation.
Answer:
- fluoride ions are incorporated into hydroxyapatite crystals
- enamel becomes more resitant to acid dissolution
- fluoride facilitates calcium phosphate precipitation
Question:
Describe the clinical implications of acid etching.
Answer:
- a technique used to increase MECHANICAL RETENTION of restorative material

FUNCTIONS
- removes plaque, organic debris, and surface enamel
- increases POROSITY of exposed enamel
Question:
Desrcibe the 3 patterns of etching.
Answer:
- TYPE I: removal of rod core
- TYPE II: removal of rod periphery
- TYPE III: irregular removal of enamel structure (consists of a combination of TYPE I & II)