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37 Cards in this Set
- Front
- Back
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What is biocompatibility
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30 years ago - just safety was part of it.
Now - efficacy is necessary to consider the biological functions of the material we use. |
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What is one major concern for biocompatibility?
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Toxicity: inherent injurious effect of a chemical or physical agent on a living system.
This is different from hazard - actual contact w/ or entrance into a living system of the toxic agent. Most dental materials are toxic. Fortunately, we can use them in a way to remove the hazardous effects of the toxic materials. |
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What component of dental amalgam may be considered toxic?
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Mercury as liquid and vapor are both hazardous to pt and dentist.
As an inorganic compound in amalgam, it does not have a hazardous effect. Amalgam mercury is toxic prior to being set, but after being set the inherent toxic effects are not released. In general, has no hazardous effect to the pt. |
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What established the mechanical properties for dental amalgams?
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Specifications for Dental amalgam by National Bureau of Standards, 1919.
-first material regulated by the government. |
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What established the biological properties for dental amalgams?
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Medical Device Amendements
US congress, 1976 and, "recommended standard practices for bioloigcal evaluation of dental materials" only for safety, not efficacy. ADA document # 41; 1979 - safety FDI document 1980 - efficacy These are both used today |
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What are the 3 steps of tests that dental materials must undergo?
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biological tests
1) initial tests 2) secondary tests 3) usage tests -test materials done at university level before sending it to industry. FDA only recognizes 3rd part tests and university based research labs. |
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What is an initial test that is done on dental materials?
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Cytotoxicity tests
-cell attachment + growth (take human fibroblasts and test attachment with materials. However, we cannot tell the toxicity here. Just doesn't give a hazardous effect to the cell. Ex. copper doesn't show good attachment to human epithelial cells. copper does give a hazardous effect to the cells. -membrane permeability (Cr relase assay, neutral red release assay) -metabolic activity (DNA synthesis, protein sythesis) -sytemic toxicity test (LD test) |
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What does it imply when there is increase cell membrane permeability?
What assay is used to assess this? |
-indicates lysis of the cell
Cr-release assay: turn the hexavalent Cr to a trivalent Cr (a radioisotope) that is seen in a permeable membrane. you can monitor the radiation to determine the hazardous effects of the material cultured with the cell. |
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Describe the neutral red release assay
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New technique to copy the Cr release assay.
Uses the same mechanism. The test cell is stained with a dye (not radioisotope). The pink cell, a healthy cell, is cultured with the test material. If the material is hazardous to teh cell, permeability is increased , and the cytoskeletal protein is released. The color of the cell changes to clear, if the cell is destroyed. |
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What is the pathway toward which the material can reach the pulp?
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via the dentinal tubules. Diffusion assays are used to test the transfer of the materials toward the pulp.
It uses a few methods: Agar overlay method, Milipore filter method, and Dentin barrier test |
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What is the agar overlay method?
What is a leechable component? What test is used? |
on top of cell, pour a layer of agar gel which is very porous. This is supposed to serve as dentin tissue.
On top of agar is the test material with + control (hazardous effect) and - control (no hazardous effect) . If the test material does not leech or corrode on top of the agar, it is not hazardous. the inherent toxicity does not give any hazardous efect to cell. If the color does change, there is a hazardous effect. Leechable components from the material cause a hazardous effect. |
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Describe the Millipore filter method
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because the agar pores are not controlled for size, this particular test is controlled for size. It shares the same diameter as the dentin.
on top of the filter is placed the test material. The only size that will be passed through is if it has the same size as teh filter. If it does pass trhough, the color changes and we can decide if it is hazardous. There is a layer of agar layer below the cell layer. The agar is placed there to prevent the cell growth and serves as a cushion. |
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What is a dentin barrier test?
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this uses a real dentin tissue, and it must be fresh about 1 mm in thickness. Use a neutral red stained cells, culture it with the medium. On top of the medium is the dentin. On top of dentin is the test material. The leachable components pass through the medium (diffusion stage), and may be hazardous to the neutral red stained cells.
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What is the medium suppose to reflect in the dentin barrier test?
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It will be similar to the tissue fluid that is found in dentin.
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How is metabolic activity tested?
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-DNA synthesis (P-dTTP) - if this is downregulated, it implies that the material is hazardous to the cell. monitor through radioisotope again.
protein synthesis - S methionine; H-leucine. same principles as above. This is for cytotoxicity , not carcinogenic |
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What is the systemic toxicity test?
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LD 50 test: oral, inhalation
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What are 2 mutagenesis tests
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1) Ames' test
2) sytles' test do not want to cause cancer to pt. |
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What is an Ames' test?
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Use mutant S. tymphimurium (hisitidine-dependent) important for cell growth.
this ensure that bacteria cannot make their own His, and will not survive. Add the test material and His -depleted medium to the mutant S. tymphimurium. Results: negative: mutants (not grow) positive: if there is a mutagenic affect from the material, His-independent native S. typhimurium (grow). material causes the mutation such that the bacterial will grow. |
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What is the Styles' cell transformation test?
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aka soft agar test.
anchorage dependent cell growth (solid substrate to which cellular components must attach to grow = 1st requirement of cell growth). Cancer, however, does not need such attachment. it has anchorage-independent cell grwoth. Test: culture human fibroblasts cells with test material, and if its mutagenic, it will go from an anchorage dependent cell growth to an anchorage independent cell growth. usually takes 1 month to see this. biomaterial releated cancers need 10-20 years. so, you get a lot of false negative results. |
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What are some characteristics of secondary tests?
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-longer term
- used in small animals one type is a mucous membrane irritation test. can't use a cell culture to do this test. Test material is a crown, let the crown touch the buccal mucosa. Surgically remove the buccal mucosa, and see whether there is inflmmation. |
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Skin sensitization test?
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Test for hypersensitivity.
use a guinea pig; inject the test material along with a adjuvant. requires a component to activate the antigen (and therefore immune response). For 7 days, let the material interact and produce the antibody by guinea pig. Inject same type of material to submucosa. After 2 days, if there's sweeling or redness, the IgG circulation causes a hypersens. reaction. Dental biomaterials display delayed hypersensitivity Type 4, IgG involvement. |
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What's an implantation test?
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Tests for inflammation tested using an animal body.
Use a polyethylene tube with the test material. The open side contains the test material. Plae the tube in the animal. The opening side shows teh contact area. If tehre's no inflammation, there is no hazardous effect. foreign body reaction - body recognizes any body taht is foreign. This involves multinucleated giant cells and macrophages, lymphocytes. |
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2 stage implantation
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we create a surgical trauma 3 environment to load test materials.
use a teflon block (non toxic, non hazardous) for stage 1. 1 month later, do a surgery to remove the teflon. This will create a space surrounded by soft tissue. In teh 2nd stage, place a test material. After 1 month, remove the surrounding tissue wall. Any inflammation seen in stage 2 will be caused by teh test material, not by surgical trauma. |
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Usage tests: dental pulp irritation test
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has a certain requirement for each type of material.
tests the leachable component once again. Silicate cement has no hazardous effects (positive control) and zinc oxide (negative control). |
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What are 2 other usage tests?
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mucosal and gingival usage tests
implantation tests - gingival reattachment, mobility, radiograph |
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Describe the cell nuclear free zone of teh dentin pulp complex?
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its nuclear free but the odontoblasts have cytoplasmic extensions into the dentinal tube. So there is still cells, but not nuclei.
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Why are dentinal tubules good for transport?
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Because they are numerous (50,000 m2 near pulp)
and due to the diameter (2.5 microns near pulp) |
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Describe the convection and diffusion components of the dentin tubule transport system
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1) Convection : movement of soln depends on hydraulic pressure (high P to low P).
2) Diffusion (based on ions and molecules) based on concentration gradient where it moves from hypertonic to hypotonic. |
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Describe the ionizability of acid and concentration of acid with respect to the dentin buffer system
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Strong acids and bases are well buffered since they dissociate easily.
however, weak acids are not well buffered and are able to penetrate dentin easily. concentration of weak acid > 50% pH at pulp interface is about 3-4 <50% is about 6.5-7 pH over a 1 week period |
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What does acid etching cause?
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Typically use 35% phosphoric acid, and you get a moderal pulp reaction instantly. Over a which the pulp interface as a pH 6.5-7. Over 5 weeks, you want to just see a slight pulp inflammation
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What is a slight pulp inflmmation? What components do you see?
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Its reversible; exists for a short time and you cannot avoid it.
you see a localized cellular infiltration, and there's some obscurity to the cell free zone. dentin tubules have a slight infiltration of inflammatory cells but its localized. |
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What is moderate pulp inflammation?
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you see increased cellularity; disrupted odontoblast, some nuclei displaced into the dentinal tubules.
when inflammation occurs, there's a high hyraulic P > 24 mmHg. this pushes odntoblasts into dentin tubules. if there's damage, it's irreversible (>1 week) |
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Describe severe pulp inflammation
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marked cellularity, odontoblast layer is destroyed and the predentin is missing. this is typically an irreversible change
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Describe the pulp reaction to zinc polyacrylate cements
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zinc polyacrylate cemets have 2 components that are both toxic: low pH, and leaching of zinc. both cause lysis of cell.
Before the cement is set, the material is very toxic and you might get a moderate reaction. however, in a usage test after the material is set, there is only a slight reaction. solid cement will NOT release acid. |
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Describe the pulp reaction to calcium hydroxide
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calcium hydroxide is used in direct or indirect pulp capping. sometimes pulp tissue is exposed in deep cavity, so you need to place a cap.
the ph > 12, so its very toxic. Through a usage test, we can notice that with a 1 mm thickenss, there is necrosis and slight inflammation. Eventually, new mesenchymal cells eventually differentiate to make new odontoblasts (2ndary) to dentin, and creates osteodentin bridge covers the pulp tissue. |
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How can an acrylic denture base cause trauma?
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-can cause mechanical and chemical trauma
-mechanically it can cause fibrous hyperplasia chemically it may cause allergic stomatitis. one test is to have your pts wrapped teh denture around their arm and test to see if there's inflammation after a few days. this indicates that there's incomplete polymerization of the denture due to the monomer. |
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Whats molecular biocompatibility?
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the idea by which new regulation should be implemented based on to test the safety and efficacy of biomaterials.
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