Class I Amalgam Restoration

Question 1

What is dental amalgam?

Answer 1

Amalgam is a metal alloy that mixes mercury (Hg) and a powder mixture of silver-tin-and copper metals (Ag-Sn-Cu)

Question 2

When is amalgam generally used?

Answer 2

Typically used in moderate to large class I and II preparations and class V preparations, which are difficult to isolate, in posterior teeth where esthetics are not as large a concern. Also indicated when patient has a moderate to severe risk for caries.

Question 3

Due to its Hg content amalgam is a highly controversial substance and has been highly studied. The FDA, CDC, & WHO have all studied amalgam extensively. What has been their finding?

Answer 3

No evidence of harm directly related to amalgam and that amalgam is a highly effective restorative material that can last a very long time.

Question 4

Amalgam actually presents the most danger to who? What can be done to limit this?

Answer 4

Practitioner and staff. Use of high volume evacuation and rubber dam should be used at all times. Masks should always be worn and proper amalgam handling procedures should always be followed.

Question 5

Besides class I, II, & V restorations, what are two other procedures, for which, amalgam is indicated?

Answer 5

Amalgam is used to overlay cusps and used for core build up restorations (crown is overlayed on top of amalgam core).

Question 6

Give at least 3 advantages & 3 disadvantages of amalgam.

Answer 6

Advantages: 1) Strong & durable material
2) Wears at a rate similar to tooth structure
3) Slight amount of corrosion occurs, resulting in decreased microleakage at cavosurface margin. Decreased risk for recurrent caries.
4) Relatively easy to use & not time consuming to place
5) Low cost
Disadvantages: 1) Not tooth colored
2) Does not bond to tooth structure independently. Thus, requires adhesive component.
3) Expands & shrinks in response to temp changes faster than surrounding tooth material. This can lead to discomfort for ~4 weeks
4) Some people are allergic to amalgam
5) Contains mercury. Not much risk to patient but certain risk to practitioner, due to vapors, and environment, must be disposed of correctly.

Question 7

Name 3 factors that might lead to fracture of an amalgam restoration.

Answer 7

1. Patient didn’t allow 24 hours for restoration to completely set before eating crunchy food.
2. Restoration wasn’t minimum depth of 1.5 mm
3. Undercarved/high contact points or sharp angles

Question 8

While post-operative sensitivity is normal, after what period of time should the practitioner become concerned?

Answer 8

If Post-op pain lasts longer than 6 wks there is a problem

Question 9

What might lead to tooth fracture following an amalgam restoration?

Answer 9

If isthmus is too wide (generally over 1/3 of the width of the occlusal surface) buccal & lingual walls may fracture.

Question 10

Bonded amalgam preparations utilize phosphoric acid to “condition” the cavity preparation before placing the dentin bonding agents. Why?

Answer 10

The phosphoric acid alters the internal surface layer by removing the smear layer (organic & inorganic substances clogging 80% of the newly exposed dentinal tubules), thus allowing the dentin bonding agent to penetrate ALL the dentinal tubules increasing retention and decreasing sensitivity.

Question 11

What 3 things does conditioning w/ an acidic solution remove?

Answer 11

1. Hydroxyapatite from enamel
2. Organic components in dentin
3. Removes the smear layer

Question 12

Adding bonding agent following conditioning w/ an acid increases retention and decreases post-op sensitivity by what two means?

Answer 12

1. Infiltration of resin monomers into demineralized enamel & dentin
2. Replacement of the smear layer

Question 13

What positive long-term effect does the adhesive layer have on the success of amalgam restorations.

Answer 13

The adhesive layer has been shown to significantly reduce marginal microleakage, which will reduce recurrent caries in the future.

Question 14

The bonded amalgam procedure, with the use of an acidic conditioner and a bonding agent, is contraindicated for individuals with sensitivity to what?

Answer 14

Methacrylates

Question 15

What bonding agent and primer have we been using in amalgam restorations in lab?

Answer 15

Prime & Bond NT Dual Cure. Bonds the dentin & enamel to the amalgam bonding accessory kit using self cure activator and prime and bond NT.

Question 16

What amalgam bonding kit was used?

Answer 16

Amalgam bonding accessory kit. Bonds Prime & Bond NT Dual to Amalgam using a catalyst and an amalgam bonding base.

Question 17

After applying phosphoric acid tooth conditioning gel, wait 15 seconds, rinse with water vigorously for 10 seconds, air dry slightly leaving moist, and finally blot dry w/ cotton pellet. Why can’t you completely dry the cavity w/ the air gun?

Answer 17

Enamel tubules will collapse if overdryed.

Question 18

For a class I restoration what is the first place that amalgam should be condensed? Why?

Answer 18

All Buccal and Lingual line angles b/c those are the most retentive parts of the preparation.

Question 19

After placing & condensing the amalgam the preparation should be ____________.

Answer 19

Overfilled

Question 20

What is a 21B instrument?

Answer 20

Acorn burnisher

Question 21

What is the most common mistake made by students while carving?

Answer 21

Undercarving

Question 22

How many times should you burnish? What instrument is called for at each step?

Answer 22

Burnish 3 times:

1. Acorn burnisher. Apply heavy pressure during condensation
2. Acorn burnisher. After initial carving*
3. Tball burnisher, ball burnisher 26/27. After recarving*
   * Be careful not to change contour by burnishing too early

Question 23

For a maxillary molar amalgam restoration, that has a prep extending onto the lingual surface, what must be done to form a retentive wall?

Answer 23

Using a matrix band and toffelmire holder, place green stick compound b/t the matrix circumferential matrix band and a small cut piece of matrix band from your roll.

Question 24

What is the 3rd rule of occlusion?

Answer 24

The functional cusps rest in marginal ridge areas except for the mesiolingual cusps of maxillary teeth and the distobuccal cusps of mandibular teeth.