Biomaterials Exam - Amalgam as a Dental Material Flashcards
What are the 3 routes of mercury exposure?
- skin contact
- inhalation of vapor
- airborne droplets
At how many nanograms of mercury per mL blood are symptoms of mercury poisoning observed?
100 ng/mL blood
How should mercury be disposed of in a dental practice?
- use single-use capsules
- use a no-touch technique and clean up any spilled mercury
- store/discard dental amalgam scrap in cool space in capped, unbreakable jar holding water with finely divided sulfur
What does the ADA recommend for operators using mercury in their practices?
- single-use capsules
- no-touch technique to clean any spills
- discard old or damaged mixing capsules
- store any scraps in a cool space in a capped, unbreakable jar holding water with finely divided sulfur
- avoid baseboard heating in operatories where dental amalgam is used
- use face mask and water spray with high vacuum evacuation when finishing new dental amalgam restorations or removing old restorations
- do not use ultrasonic condensers
- check mercury vapor levels frequently
- office personal should have mercury levels monitored periodically through urinalysis
What type of reaction may some patients experience with exposure to dental amalgams?
allergic skin reaction; other options other than amalgam are available for restorations
Is it better to have high-copper or low-copper materials? Why?
high-copper
- greater clinical longevity of restorations
- much lower creep values measured in laboratory
What are the consequences of placing zinc in a material?
- facilitates machining lathe-cut particles (makes it more brittle)
- improves corrosion resistance
- less plastic amalgam mix
What are the consequences of having a zinc-free alloy?
no concerns about moisture contamination during trituration or condensation
If there is a higher mercury-alloy ratio, would the setting time increase or decrease?
setting time would increase (slower setting time)
What is the composition of gamma 1?
Ag2Hg3
What is the composition of gamma 2?
Sn8Hg
In low-copper dental amalgams, what is the setting reaction equation?
alloy (gamma) + Hg –> (gamma)1 + (gamma)2 + unreacted alloy particles
In high-copper dental amalgams, what is the setting reaction equation?
alloy (gamma) + Hg –> (gamma)1 + n’ + unreacted alloy particles
*NOTE: (gamma)2 does not form
What are the three metal elements that are reacted with mercury in high- and low-copper amalgams?
silver (Ag), tin (Sn), and copper (Cu)
What is the composition of n’ that is produced in the high-copper amalgam setting reaction?
Cu6Sn5