Intro Flashcards
What is a rod sheath?
Narrow space around 3/4 of each enamel rod. Keyhole shape.
What two structural units make up enamel?
Enamel rods and interrod enamel (both contain hydroxyapatite crystals)
What is intertubular dentin?
Material that runs in b/w the dentinal tubules - makes up the bulk of the dentin. It is the structural component of the hydroxyapatite-embedded collagen matrix
What is peritubular dentin?
Dentin that surrounds the dentinal tubules.Limited to the lining of the tubular walls - little organic matrix densely packed w/ apatite crystals.
What happens to the peritubular dentin with age?
Increases w/ age and decreases the lumen size of the tubule
What are the three primary bonds?
Covalent, Ionic, and Metallic
Which bond is the strongest and simplest?
Covalent
Ionic bonds are frequent in what materials?
Ceramics
Covalent bonds are commonly seen in what materials?
Polymers
Which bond has electrons that move freely thru the solid?
Metallic bond
Biological properties of materials have what implications?
Toxicity and sensitivity reactions that occur locally or systemically w/in associated tissues
How does a low surface energy liquid spread over a high surface energy substrate?
Spreads readily
What is wettability?
The measure of the affinity of a liquid for a solid as indicated by the spreading of a drop - how a material will flow over the surface of a tooth
What is the main difference w/ high surface energy vs low surface energy?
High surface energy will attract things to it. Low surface energy will not. Ex - dentin or enamel has high surface energy
How does high surface energy surface affect wettability?
Keeps a drop balled up and wettability is low
What is sorption?
It’s what happens on the surface of the tooth - adsorption and absorption
What is adsorption?
dissimilar substances in intimate contact w/ the surfaces of a solid
How do high energy surfaces affect adsorption?
High energy surfaces will adsorb molecules more readily than low energy surfaces
What is the difference b/w adsorption and absorption?
Adsorption is liquid sticking to the surface of a material. While absorption is liquid taken up into the body of a material
What is absorption?
Uptake of a liquid by a bulk solid. The substance absorbed diffuses into the solid material. Acrylics of dentures can absorb liquids
What is a usage test?
material is placed in a situation identical to its intended clinical use. In animals or humans (clinical trials)
Microleakage is a big deal for what kind of materials?
Restorative materials
What is microleakage?
Materials may not bond w/ sufficient strength to resist contraction on polymerization, wear, thermal cycling
What does microleakage cause?
A gap b/w tooth and restorative material
What is the biggest cause of post-operative sensitivity?
Microleakage that causes a gap b/w tooth and restoration and allows influx of materials that may irritate the pulp
What is most important for pulp protection?
.5mm of remaining dentinal thickness (RDT)
