enamel tissue Flashcards
enamel is ____ % by weight inorganic substance
96%
principal mineral component is ____; enamel crystals, compared to other 3 mineralized tissues, are ___ and consist of more ____
calcium hydroxyapatite; larger; impurities (fluoride, carbonate)
enamel is ___% by weight organic substance
1%
the highest percentage (90%) of the organic substance of enamel is composed of ____, a seed protein for normal mineralization
amelogenin
____ makes up 3% by weight of enamel
water
DEJ configuration is ____ in the coronal area for adaptation to occlusal forces
scalloped
DEJ configuration is ____ in cervical areas (non-load bearing areas)
smooth
ameloblasts are _____ epithelial cells
columnar
the ____ of the tooth germ gives rise to ameloblasts
inner epithelial layer
growth lines of enamel are called _____
growth lines or striae of Retzius
4 mineralized tissues of the body
enamel (the hardest)
dentin
cementum
bone
growth lines of dentin, cementum, and bone
dentin- von Ebner
cementum- lines of Slater
bone- lamellae
____ are numerous small transverse ridges on the exposed surfaces of enamel
perikymata
_____ end on the enamel surface as grooves; _____ are created between the grooves
striae or lines of Retzius; ridges (Perikymata)
each perikymata is thought to take approx ____ to form
8-10 days
perikymata are found on all permanent teeth, but are usually most noticeable on _____
canines
the structures of enamel are due to the ___ and ___ of the apatite crystals in each site
direction; density
structural unit of enamel
enamel rods
an enamel rod has a diameter of ____ and a length of up to ____
5-6 micrometers; 2.5 mm
each rod is formed by ____
one ameloblast
outer surface of the rod
enamel sheath
the highest percentage of organic material in the enamel sheath
amelin
lies between the sheaths of the rods
interrod substance
_____ secrete the interrod substance
two or more ameloblasts
crystal density and direction in enamel rod, sheath and interrod substance
rod: hydroxyapatite crystals are most dense in the center or core of the rod and run parallel to the long axis of the rod
sheath: less dense than core and run in different direction; higher % of organic substance
interrod: more dense than in sheath and run in different directions
each ameloblast secretes ____ and two or more ameloblasts secrete the _____
one rod and its sheath; interrod substance
rest period of an ameloblast is marked by an _____; a rod is segmented because it is secreted in a ____ manner
interrod striation; rhythmic
enamel rods are at ____ to the dentin surface
right angles
extend for varying depths from the surface of enamel and consist of linear, longitudinally oriented defects filled with enamel protein or organic debris from the oral cavity
enamel lamellae (extend toward dentin, may enter dentin and pass to pulp)
clinical significance of enamel lamellae
access by acidophilic microorganisms (caries) stain substances (esthetic considerations)
tufts contain a greater concentration of _____ than the rest of the enamel
enamel protein (tuftelin)
enamel spindles originate from cell processes of _____ that become embedded in newly secreted enamel
odontoblasts
originate at DEJ and pass into enamel
enamel tufts
originate in dentin, pass DEJ into enamel
enamel spindles
enamel tufts and spindles contribute to:
the spread of caries along the DEJ
Alternating dark and light bands (layers) of varying width: Originate at the DEJ border and pass outward ending at some distance from the outer enamel surface
Hunter-Schreager bands
what are Hunter-Schreager bands caused by?
different direction of enamel rods in adjacent layers
change in enamel rod direction is regarded as a _____, minimizing the risk of ____ in the ____ direction under the influence of masticatory forces. clinically significant when performing operative dentistry
functional adpatation; cleavage; apical
ectopic enamel formation is called an _____
enamel pearl
intrinsic stain caused by what antibiotic
tetracycline
what causes mulberry molar?
congenital syphilis
tooth within a tooth
dens in dente
an omnivorous fish native to the Amazon river basin in South America and notable for its uncanny mouth of human-like teeth; the species is a close cousin of the piranha
pacu
