1 Fundamentals Flashcards
Enamel:___% inorganic hydroxyapatite mineral by wgt. __% volume
96% by wgt…86% vol
Enamel: Small organic matrix of two types of glycoproteins __________ & __________ in intercrystalline spaces and in a network of micropores opening to the external surface.
amelogenins & enamelins
What defines the COLOR of teeth?
Enamel Thickness and the color of the underlying DENTIN
What is the narrow space around 3/4 of each Enamel Rod and is KEYHOLE shaped?
Rod Sheath
What are the two structural units of Enamel?
1.Cylindrical Enamel Rods and 2.Interrods (both containing hydroxyapatite crystals)
*What are the two types of dentin?
*InterTubular Dentin and Peritubular Dentin
*Which dentin type is the STRUCTURAL component of the hydroxyapatite-embedded collagen matrix and the BULK of the dentin?
*InterTubular Dentin
*Which Dentin is LIMITED to the lining of the tubular walls and has LITTLE organic matrix packed DENSELY with apitie crystals?
*Peritubular Dentin
*Which dentin type increases with age?
*Peritubular dentin
*Which atomic building bond is the strongest AND simplest where atoms SHARE electrons?
*Covalent Bonds
Rank the strength of these individual bonds from Strongest to Weakest: Ionic, Metallic, Covalent
Srongest: Covalent—->Ionic—–>Metalic
What am I? Since ions are surrounded by non-directional electrostatic fields, it is possible for + and – ions to find positional arrangements that are mutually beneficial and lowers the energy. Ions can form a regular, 3-D network.
An IONIC SOLID! Building blocks of Ceramics!
What am I? Similar arrangement to ionic solids except that there is no strong electrostatic attraction between atoms. Held together by the cloud of electrons.
Metallic Solids!
What am I? Some atom of the same elements can join (C, Si, Ge). They have directional bonds that limit the possible arrangement of the atoms. The shared electrons result in filled orbits = stable molecules. Rare occurrences -diamonds.
Covalent Solids!
What did Dr. Cramer consider Van der Waal and hydrogen bonds to be categorized as?
Secondary Bonds
What am I? Some molecules can be solid at room temp. If they are long enough the dipole-dipole inter- actions can bond molecules together. Low bond strength means low melting temps. Eg: WAXES!
Molecular Solids
What are the two possibilities for arrangement of solids?
Crystalline and Amorphous
CERAMICS-what type of bonds and what is the arrangement of solids?
Ionic Bonds….Crystalline and Amorphous
METALS-what type of bonds (DONT get that wrong) and what arrangement of solids?
Metallic bonds….Crystalline
POLYMERS-what type of bonds? How is it like wax?
Covalent and Secondary bonds…like wax because polymers are molecular solids
*What property of materials encompasses toxicity and sensitivity reactions that occur locally or systemically within associated tissues?`
*Biological Property
What is this phenomenon? Atoms or molecules at the surface of liquids or solids differ from those in the bulk creating an inward attraction toward the bulk thus adsorbing ambient atoms or molecules.
Surface Properties
*What is this describing?: A low surface energy liquid will readily spread over a high surface energy substrate.
*Surface energy
*What is this describing?: The measure of the affinity of a liquid for a solid as indicated by the spreading of a drop.
*Wettability
What is perfect wettability?
A contact angle of 0 degrees!
*Which form of sorption occurs when dissimilar substances in intimate contact with the surfaces of a solid = ADHERE?
*Adsorption
*high energy surfaces will _____ molecules more readily than low energy surfaces
*ADsorb
*Which form of sorption is the uptake of a liquid by a bulk solid?
*Absorption
*The substance absorbed _______ into the
solid material
*Diffuses…his example-nasty ass dentures that have absorbed chemicals and food particles and now smell bad
*What is the most important biocompatability test?
*The Usage Test
*_______ _______– material is placed in a situation identical to its intended clinical use. In animals or humans
(clinical trials)
*Usage Tests
What is the Advantage to Usage Tests for Biocompatability?
Relevance to use the material is ASSURED
*What are the 5 disadvantages to usage tests?
*1.Expensive 2.Time 3.Legal/Ethical Issues 4.Control 5.Interpretation
*_________ – materials may not bond with sufficient strength to resist contraction on polymerization, wear, thermal cycling
*MicroLeakage
*_____ between tooth and restoration allows influx of materials that may irritate the pulp.
*Gap
_____ ______ – organic and inorganic debris
forms dentinal plugs in tubules that renders them impermeable. Must be removed for strong bonds.
Smear Layer
*What is the MINIMAL REMAINING DENTINAL THICKNESS (RDT)? How much leakage can you reduce at this thickness? What is the thickness for 100% reduction in leakage?
*0.5mm RDT…reduce 75% of leakage..2.0mm=100%reduction in micoleakage
What about amalgam Seals the bond onto the prep?
Corrosion!
Which material is unable to diffuse through dentin?
Glass Ionomers