510-9 Flashcards
What is the chemical makeup of enamel?
96% mineral-hydroxyapitie (OH- + Calcium Phosphate) crystals, 3.5% water, and 0.5%organic material(type I collagen)
What is the chemical makeup of dentin?
70%mineral-living tissue, 2nd hardest substance in the body
What is the chemical makeup of cementum?
45-60% mineral. Living, bone like tissue
Where is enamel the thickest and how thick is it at this surface?
The occlusal surface is thickest at 2.5mm
What is the optimal level of fluoride recommended by the US PHS?
0.7 to 1.2 ppm
How do type I collagen fibers help form enamel rods?
The ameloblasts send out the collagen fibers like a scaffolding and then pull them back for optimal room for rod and inter rods.
Is the DEJ smooth?
No, it is “scalloped” or “stair-step like” to help resist shearing forces.
What are the three types of enamel imperfections? Rank the size.
1)Lamellae-HUGE, span the full thickness of the enamel. Filled with organic material 2)Tufts shorter projections from the DEJ, branched. 3)Spindles-odontoblast processes getting caught in ameloblast epithelium. Spindles have a mix of enamel and dentin :)
Where is thicker dentin? DEJ or near pulp?
Thicker as odontoblasts move towards PULP
How are odontoblasts nourished?
By the vessels in the pulp
What are the 5 types of dentin?
1)Predentin-think wet concrete on sidewalk 2)Primary dentin-makes up MOST of the tooth 3)Secondary dentin-develops after ROOT formation is complete. Proceeds slowly and REDUCES the size of the pulp cavity 4)mickey MANTLE dentin-The dentin under the crown 5)Tertiary dentin: made in response to CARIES, attrition, and restorations. Broken down into 2 subcategories Reactionary (existing odontoblasts)and Reparative(NEW odontoblasts)
How do dead tracks in dentin form?
The loss of odontoblasts
What is the nerve plexus of Raschkow?
The pulp/dentin nerve complex “loops” of nerves extending past the odontoblast and into the predentin
What are the three mechanisms of dentin sensitivity?
1) Dentin CONTAINS NERVE ENDINGS that respond to stimuli 2)ODONTOBLASTS serve as pain receptors and are connected to the pulp innervation 3)FLUID movement though the dentin tubules which stimulates pulpal free nerve endings near the odontoblasts
What argues against the dentin containing nerve endings sensitivity issue?
Although there are some nerves in the dentin, Bradykinin and histamine show no effect when applied to the dentin.
What are problems with odontoblasts as receptors dentin sensitivity theory?
Although odontoblasts can polarize and propagate a signal, the membrane potential is rather small. Anesthetics do not work on dentin sensitivity.
Describe why the fluid theory of dentin sensitivity is most logical.
Fluid movement thru the dental tubules can distort nerve endings in the pulp causing pain. Explains anesthetic issue and other common issues with the other two theories.
What are the cells that produce cementum? What are they initially called and what do they develop into?
Cementoblasts, they look like fibroblasts. They then develop into dendritic cementoCYTES-look like osteocytes.
What are the functions of acellular and cellular cementum?
Acellular: Anchorage, Remember you want to grab the shaft towards the middle for stability?? Cellular: Adaptation to tooth wear, movement, and repair.
What is the term for the DCJunction? What is it made out of?
The granular layer of TOMES, collagen and non collagen matrix proteins
What are the three possibilities for the CEJ? What are the percentages associated with it?
An overlap: 60% of the time. A flush abutment: 30% of the time and a gap, exposing the dentin: 10% of the time.
What are the four main cell types of the pulp?
1) odontoblasts 2)fibroblasts 3)undifferentiated ectomesenchymal cells (((PSC’s!!! can diff into odonto’s and fibro’s))) 4)WBCs
What are the four zones of pulp?
1)Odontoblastic Zone-odontoblasts here 2)Cell free zone of WEIL “WHILE”-loosely arranged CT fibers between odontoblasts and fibroblasts 3)Cell Rich Zone-High cell density fibroblasts, WBCs StemCells 4)Pulp Core-blood vessels and nerves in a gelatinous CT matrix.
