aknight1302's version from 2015-11-17 16:38


Return to Microanatomy Test 4 TOC


Question Answer
Why are Rods "more susceptible" than inter-rods to acid etching?THEY'RE NOT... it all depends on the orientation... (which can be different depending on the location of restoration)
Unlike bone, dentin, and cementum, ENAMEL is a mineralized _____ tissue (tissue origin type)mineralized EPITHELIAL tissue
by-weight composition of enamel96% inorganic, 1% organic, 3% water
what are the two amelogenic proteins found in enamel?Tyrosine-Rich Amelogenic Protein (TRAP) & Lysine-Rich Amelogenin Protein (LRAP)
What non amelogenic proteins are found in enamel?enamelin, amelin, & tuftelin
Incremental Linescan be seen from longitudinal section, often formed during period of sickness, due to sensitivity of ameloblasts
Where would you find APRISMATIC enamel?at the DEJ and at the outer enamel surface of erupted tooth (innermost and outermost, newest and oldest)
Where are ENAMEL SPINDLES found and what are they?Enamel spindles are found at the DEJ, they are remnants of Odontoblastic processes that are trapped in early amelogenesis
Stages of Ameloblast lifecycleMorphogenetic (undifferentiated) (central nuclei in IEE), Histodifferentiation (IEE signals differentiation in preodontoblasts, then wait for initial dentin to move to next phase) (polar nuclei) Secretory (initiated in response to initial dentin, Tomes' Processes do they thing and build enamel of a crown happens) Maturative (enamel hardening, cells alter between smooth bordered and ruffle bordered) Protective ("protect" and involved in tooth eruption, REE fuses into oral mucosa)
What factors are secreted by Preameloblasts to induce differentiation of undifferentiated prodontoblastic cells?TGF-(B1), BMP-2, IGF
What part of the Tomes' Process is "missing" during initial enamel secretion?the Distal portion of Tomes Process (dpTP), hence no rod/interrod of aprismatic, initial enamel
What is the 2nd level of enamel organization?rod-groups criss-crossing (provide added structural support)
What is the 1st level of enamel organization?rod/interrod organization (key hole)
Enamel HARDENING is done by ____ Ameloblasts.... increasing ___ and breaking down and absorbing ____Maturative, Crystal size (mineralization)(through CRYSTAL GROWTH, not new crystals), matrix proteins
True or False: Enamel hardening is achieved through the deposition of new HYAP crystalsFALSE (hardening is achieve through the GROWTH of pre-existing crystals)
Where is the HARDEST enamel found and why is it harder?TOOTH SUFACE (final enamel) is harder because of higher mineral content (more hardening by maturative ameloblasts)
What are the layers of the Reduced Enamel Epithelium?IEE, OEE, Stratum Intermediate, Stratum Reticulum (same as enamel organ)
How many Ameloblasts from a single enamel rod?1 (rod is directional and product of dpTP of an ameloblast)
How many Ameloblasts form interrod enamel around a single rod?4 (inter-rod is a product of the ppTP and neighboring ameloblasts secrete up against each other)
What is the unmineralized matrix protein precursor of enamel?(TRICK QUESTION) There is no unmineralized matrix protein precursor of enamel
What is the most abundant type of enamel protein? (in completed teeth)Amelogenins (90%)
Which enamel proteins prevent crystal fusion?Amelogenins
Which enamel proteins are found more in LATER (forming process) enamel?Amelogenins
Which enamel proteins "stimulate and regulate crystal growth"?Non-amelogenins
Which enamel proteins are found more in EARLY (forming process) enamel?Non-amelogenins
Knockout of which proteins lead to ENAMEL HYPOPLASIA?(formation of enamel, but very weak)AmeloGENins
Knockout of which proteins lead to ENAMEL AGENESIS? (no enamel formation)AmeloBLASTins