Viva voice questions in Amalgam for Dental students
- What is amalgam?
amalgam is an alloy that contains mercury as one of its constituents.
- What is the ADA specification number for Amalgam?
ADA specification number for Amalgam is 1
- What is Amalgamation?
The process of mixing liquid mercury with one or more metals or alloys to form an amalgam
- What is Trituration.
The mixing procedure of amalgam alloy with mercury is technically called as trituration.
- Define condensation?
Special instruments are used to forces the plastic mass into the prepared cavity by a process known as condensation.
- What is Dynamic creep?
Dynamic creep is the deformation of set Amalgam during function. Because of the creep Amalgam restoration extends out of the cavity preparation and increases its susceptibility to marginal breakdown.
What is creep?
Creep is the time dependent plastic deformation which occurs when a metal is subjected to a constant load near its melting point.
Delayed expansion occurs if the amalgam mic contaminated with moisture during trituration or condensation.
The expansion begins 4 or 5 days after condensation and results in hyper occlusion and cracks in tooth. This restoration will cause pressure in pulp all direction will cause intense pain.
What is the working time of Amalgam?y
Working time of Amalgam is 3 to 4 minutes.
Which constituent of Amalgam alloy decreases expansion?
Tin controls the reaction between silver and mercury. Without tin, the reaction would be too fast and the setting expansion would be unacceptable. Tin reduces the rate of reaction and the expansion to optimal values.
What is the cause for mercury intoxication in dental office?
Mercury intoxication in dental office mainly results from Inhalation of mercury vapours
What is advantage of minimal mercury technique?
The advantage of minimal mercury technique is greater plasticity and adapts well to cavity walls.
What is minimal mercury technique or Eames technique?
The most obvious method for reducing the mercury content of the restoration is to reduce the original mercury/alloy ratio.According to Eames technique alloy and mercury ratio should be 1:1. In 1959 this technique was introduced by Eames.
How to control the setting time of Amalgam?
The setting time is best controlled by altering the trituration speed or trituration time or both. Spherical alloys require less amalgamation time than the lathe cut alloys.
What is delayed expansion?
The expansion begins 4 or 5 days after condensation and results in hyper occlusion and cracks in tooth. Delayed expansion occurs if the Amalgam mix is contaminated with moisture during trituration or condensation.
Viva voice questions in Impression materials
What is the composition of silver alloy?
Silver
Tin
Copper
Zinc
Platinum
Palladium
Indium
What are the functions of constituents in the silver alloy powder?
Silver
Major element in the reaction
Whitens the alloy
Decrease the creep
Increase the strength
Increase the expansion on setting
Increase the tarnish resistance in the resulting Amalgam
Tin:
Controls the reaction between silver and mercury
Reduces strength and hardness
Reduces the resistance to tarnish and corrosion
Copper:
Increases hardness and strength
Increases setting expansion
Zinc:
Acts as a scavenger or deoxidiser
It causes delayed expansion
Platinum and palladium improves the hardness. Indium reduces mercury vapour and improves wetting.
What isTarnish?
Tarnish is surface discolouration or slight loss of surface finish or lustre of a metal. The discolouration of Amalgam is due to formation of black silver sulfide.
What is corrosion?
Corrosion s the actual deterioration of the metal by reaction with environment. Tin chlorides and oxidesare the corrosion products of low copper alloys whereas copper oxide is the corrosion of high copper alloys.
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What are the mixing variables of Amalgam?
Undermixing, normal mixing and over mixing are the three mixing variables that result from variations in condition of trituration of the alloy and mercury. The undermixed Amalgam appears dull and is crumbly, the normal mix appears shiny and separates in a single mass from capsule and the overmixed Amalgam appears soupy and tends to stick to the inside of the capsule
What is the necessity of finishing and polishing of amalgam?
Amalgam without finishing and polishing will have a rough surface microscopically and results in concentration cell-type corrosion.
Which one is preferable traditional low copper or high copper amalgam?
Compared to traditional low copper Amalgam, high copper amalgams became the material of choice because high copper Amalgam have
High early strength
Low creep
Good corrosion resistance
Good resistance to marginal fracture
What is the recommended force for the condensation of Amalgam?
The average recommended force is 3-4 pounds r 13 -18 Newtons
The percentage of zinc present in non zinc containing dental amalgam?
Alloys containing less than 0.01% of zinc are classified as nonzinc alloys with more than 0.01 of zinc are classified as zinc containing alloys.
Uses of zinc
Reduces brittleness
It reacts rapidly with oxygen and their impurities and prevents the oxidation of more important elements like silver, copper or to . Thus it acts as deoxidiser or scavenger
Better handling property
If the Amalgam is contaminated with moisture during trituration or condensation,an causes delayed expansion.
What is the cause for delayed expansion?
Delayed expansion is due to pressure exerted by hydrogen gas, which is a corrosion product evolved during the reaction between zinc and moisture. If the Amalgam is contaminated with moisture during trituration or condensation,an causes delayed expansion.
What is the use of cavo surface angle for Amalgam restoration?
Cavosurface angle for Amalgam restoration is 90 degrees and forms a butt end.butt end as it increases compressive and tensile strengths. Resistance to compression forces is the most favourable strength characteristic of Amalgam. Because amalgam is strongest in compression and much weaker in tension and shear, the cavity design should maximise compressive stresses in service and minimise tension or shear stresses.
What are the aims of condensation?
To adapt the mix to the cavity wall
Removes excess mercury
Proper condensation increases the strength and decreases the creep of the Amalgam.
Condensation should be started at the centre and the condenser point is stepped sequentially towards the cavity walls
What is the need of carving and finishing of Amalgam restoration?
Carving and burnishing is done to reproduce the tooth anatomy and to get a smooth surface respectively.
Carving should not be started until the amalgam is hard enough to offer resistance to carving instruments
A scrapping or ringing sound should be heard when it is carved
Polishing also required as it minimises corrosion and prevents adherence of plaque
Final polishing should be delayed at least 24hrsafter condensation
What are the effects of mercury toxicity?
Mercury is absorbed through skin, lungs or GIT, most commonly by lungs and penetration into the tooth from the restoration. Increase in exposure causes toxicity which may associated with symptoms like weakness, fatigue, irritability, dizziness, insomnia, weight loss.
What are the safety measures to avoid mercury toxicity?
Mercury should be kept in an unbreakable container that are tightly sealed.
Spills and leaks should be cleaned up immediately by approved methods
Water spray and a high volume evacuation should be used when removing an old amalgam restoration or finishing a new one
Glasses and disposable face mask should be worn to reduce hazards associated with flying particles and the inhalation of Amalgam dust
Amalgamators that completely enclose the arms and amalgam capsules during trituration should be used
Since Mercury vaporises at room temperature, hospitals should be well ventilated to minimise the mercury level in the air
Use of gloves is must.
How to dispose excess mercury or amalgam?
The potential hazards of mercury can be greatly reduced by attention of a few precautionary measures.
All excess mercury, including waste, disposable capsules, and amalgam removed during condensation should be collected and stored in well sealed containers.
Proper disposal through reputable dental vendors is mandatory to prevent environmental pollution.
Amalgam scrap and materials contaminated with mercury or amalgam should not be incinerated or subjected to heat sterilisation
If mercury is spilled, it must be cleaned as soon as possible. It is extremely difficult to remove mercury from carpeting
Ordinary vacuum cleaners merely disperse the mercury further through the exhaust.
Mercury suppressant powders are helpful, but these should be considered temporary measures
If mercury comes in contact with the skin, the skin should be washed with soap and water.
