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Amalgam Restoration


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Types

Low copper: generally inferior

High copper

Compressive strength is similar to tooth

The tensile is lower than tooth

Exhibit no clinically relevant creep or flow

Spherical

Greater leakage

Greater postoperative sensitivity

More easily condensed than admixed: but some prefer admixedhandling type

Admix (lathe-cut)

Introduction


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Linear coefficient of thermal expansion (LCTE) isgreater than tooth.

Brittle and have low edge strength

High thermal conductor

Clinical performance:

Marginal fracture, bulk fracture, secondary caries

Handling: Operator preference regarding using admixor spherical alloys

Properties


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Not esthetic

Conductivity

Tooth preparation moredemanding, lessconservative.

Disadvantages

Wear resistance.

History of use

Less technique-sensitive. Inexpensive

Strong, long longevity

Ease of procedure andisolation needs

Eventual seal of margins

Easy to develop contours,contacts, occlusion

Advantages

Amalgam


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Mercury content, mercury disposal.

Esthetics.

Removal of tooth structure

weakening a tooth

Unless bonded, no bonding benefits: bonding maynot be indicated.

Recurrent caries: reduces life expectancy

Marginal leakage until corrosion: several months

Amalgam Concerns


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Lack of scientific evidence that amalgam poseshealth risks to humans except for rare allergicreactions.

True allergies are rare

Estimate of human uptake of mercury vapor fromamalgam is 5 g/m3

No evidence ensuring that alternative materials

pose a lesser health hazard.

Mercury Controversy


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Nonesthetic cervical lesions. Large Classes 1 and 2 where heavy occlusion exist

Classes I and II when isolation problems exist forbonding.

Temporary/caries control restorations.

Foundations

Patient sensitivity to other materials

Where cost is a factor

Inability to do a good composite

Amalgam Use


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Appropriately indicated clinical situation.

High-copper material.

Tooth preparation.

90-degree cavosurface margins.

Thickness of amalgam (1-2 mm).

Mechanical retention form.

Seal tubules.Good condensation (including lateral condensation).

Appropriate development of contours and contacts.

Factors For A Successful Restoration


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Clinical Technique


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1. Local anesthesia.

2. Isolation of the operating site: rubber dam/cottonrolls, with or without a retraction cord.

3. Other preoperative consideration:1. Placing wedge in the gingival embrasure when restoring a

posterior proximal surface separates adjacent tooth andprotect the rubber dam and the interdental papilla.

2. Make preoperative occlusion assessment before rubberdam

3. For smaller amalgam restorations, the projected facial andlingual extensions of a proximal box should be visualizedbefore preparing the occlusal portion of the tooth, therebyreducing the chance of over preparing the cuspal area whilemaintaining a butt joint form of the facial and/or lingualproximal margins.

Initial Clinical Procedures


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Appropriate tooth preparation is dependent onboth tooth and material:

90-degree or greater amalgam margin (butt joint).

Adequate amalgam thickness: 0.7 - 2 mm for adequatecompressive strength.

Adequate mechanical retention form (undercut form)amalgam has lack of bonding to the tooth, must be

mechanically retained.

Tooth Preparations Requirements


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Initial stage: Provide initial form that retains amalgam Extend preparation into sound tooth structure at the

marginal areas (Mesial-distally).

Extend the depth (pulpally and/or axially) to a prescribed,

uniform dimension. Establish margins that results in a 90-degree amalgam

margin once the amalgam is inserted.

Final stage:

Removes any remaining defect (caries or old restoration) Incorporate any additional preparation features: slots, pins,

steps, or amalgam pins:

To achieve appropriate retention and resistance form.

Principles of Tooth Prep


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All initial prep relate to the DEJ, except in two instances: Occlusal enamel has been significantly worn thinner.

Preparation extends onto the root surface.

Initial depth: 0.2 0.5 mm pulpally the DEJ or 1.5 mm asmeasured from the depth of the central groove 0.2 mm inside when retention locks are not used

0.5 when retention locks are used allows placement withoutundermining enamel margin.

Axial depths on the root should be 0.75 - 1 mm forretention groove or cove while providing for adequatethickness of the amalgam (Fig. 2-21) Depth of the axial wall in smooth surface lesions shouldn't

exceed 0.2 to 0.8mm deep into dentin.

Initial Stage


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Visualized preoperatively to prevent fracture by estimating: Extent of defect, preparation form requirements

Need for adequate access to place the amalgam

Marginal enamel rods should be supported by sound dentin: Preserve the strength of cusps and marginal ridges

Outline form should be extended around cusps and avoid underminingthe dentinal support of the marginal ridge enamel.

Facial and lingual proximal cavosurface margins should be 90:if


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Factors dictating outline form:

Caries, old restorative material,

Inclusion of all the defect, the proximal and/or occlusal

contact relationship,

Need for convenience form.


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Retention form features locks or ability to retain therestorative material in the tooth. Composite: micromechanical bonding provides most

retention

Nonbonded and bonded amalgam: must be mechanicallylocked

Amalgam retention form is provided by: Mechanical locking by surface irregularities of the preparation

Vertical walls (especially facial and lingual walls) that

converge occlusally. Locks, grooves primary retention form

Coves, slots, pins, steps, or amalgam pins that are placedduring the final stage of tooth preparation coves aresecondary retention form

Primary Retention Form


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Resistance form help restoration and tooth resistfracturing from occlusal forces.

Primary Resistance Form

Preventing Tooth Fracture

Conserve tooth structure: preservecusps and marginal ridges.

Prepare pulpal and gingival wallsperpendicular to occlusal forces

Rounded internal preparation angles.

Removing unsupported or weakenedtooth structure.

Placing pins into the tooth as part ofthe final stage of tooth preparation secondary resistance form

Preventing Amalgam Fracture

Adequate thickness of amalgam (.5-2mm in occlusal contact and 0.75 mmin axial areas).

Marginal amalgam of 90 or greater.

Boxlike preparation form, whichprovides uniform amalgam thickness.

Rounded axiopulpal line angles inClass II tooth preparations.

Many of these resistance featurescan be achieved using the No. 245bur, which is an inverted cone designwith rounded corners.


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Used if insufficient retention or resistance forms.

Many features that enhance retention form alsoenhance resistance form:

Placement of grooves, locks, coves, pins, slots, oramalgam pins.

Usually, the larger the tooth preparation, the greater theneed for secondary resistance and retention forms (Figs.

2-23 and 2-24).

Secondary Resistance and Retention


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Restorative

Techniques


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If amalgam is not to be bonded: Place sealer onprepared dentin: either a coating material or apolymerized resin adhesive.

May occur before or after the matrix application.

If amalgam is to be bonded: apply matrix, etch,prime, and bond

Important that bonding adhesive be fluid and unset

when the amalgam condensation occurs.

Some adhesives also achieve chemical adhesion with theamalgam.

Restorative Techniques


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Objectives of a matrix are to: Provide proper contact.

Provide proper contour.

Confine the restorative material.

Reduce the amount of excess material. For a matrix to be effective, it should:

Easy to apply and remove.

Extend below the gingival margin.

Extend above the marginal ridge height.

Resist deformation during material insertion. It should be notedthat when bonding an amalgam restoration, it might be necessaryto coat the internal aspect of the matrix before its placement toprevent the bonded material from sticking to the matrix material(Fig. 2-25).

Matrix Placement


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Mixing (triturating) the amalgam material. Themanufacturer's directions should be followed whenmixing the amalgam material. Both the speed and

time of mix are factors in the setting reaction of thematerial. Alterations in either may cause changes inthe properties of the inserted amalgam.


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Lateral condensation (facially and lingually directed) is veryimportant in the proximal box portions of the preparation toensure confluence of the amalgam with the margins.

Both high and low types are easily inserted

As a general rule, smaller amalgam condensers are used first.Subsequently, larger condensers are used. Allows amalgam to be properly condensed into the internal line

angles and secondary retention features

Very important that amalgam condensation occur before adhesivepolymerizes.

When amalgam is placed to slight excess with condensersshould be precarve burnished with a large, egg-shapedburnisher to finalize the condensation remove excessmercury and initiate the carving process.

Inserting the Amalgam


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Performed after precarve burnishing has been done,the remainder of the accessible restoration must becontoured to achieve proper form and function.

Nonbonded amalgam is relatively easy to carve.

Bonded amalgam is more difficult because theexcess polymerized adhesive resin accumulates atthe margins and is harder to remove.

Be careful not to break off chunks

Carving the Amalgam


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Occlusal areas

Use discoid-cleoid to carve occlusal surface of an amalgamrestoration.

Discoid (rounded) is positioned adjacent to the amalgam margin andpulled parallel to the margin. To smooth out anatomic form.

Use cleoid to form pit and groove anatomy

Carving pits and grooves: to provide pathways for food toescape from the occlusal table.

Carve mesial and distal pits inferior to the marginal ridge height. Carvedefinite but rounded occlusal anatomy.

For large Class II or foundation restorations, the initial carvingof the occlusal surface should be rapid, concentrating primarilyon the marginal ridge height and occlusal embrasure areas. Created embrasure form should be identical to that of the adjacent

tooth, assuming the adjacent tooth has appropriate contour. Height of the amalgam marginal ridge should be same as

adjacent tooth to reduce potential fracture of ridge area ofrestoration.


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Facial/Lingual Areas

Most facial and lingual areas are accessible and can

be carved directly.Hallenbeck carver is useful in carving these areas. The

base of the amalgam knife (scaler 34/35) is alsoappropriate.

Contour should be convex; therefore, care in carvingthis area is necessary.

Develop convexity by using unprepared tooth structureabove and below preparation as guides for initiating thecarving.

The marginal areas are then blended, resulting in thedesired convexity and providing the physiologic contourthat promotes good gingival health.


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Proximal Embrasure Areas

Amalgam knife (or scaler) is an excellent for removingproximal excess and refining proximal contours and

gingival embrasure form. Position knife below gingival margin, and carefully shave

excess by drawing it occlusally.

Knifes sharp tip can be used to develop facial and lingual

embrasure forms. If the amalgam is hardening, a shaving motion must be

used. A cutting motion can chip or break the amalgam

Use visual assessment and floss to evaluate proximal

embrasure area . Be careful when using If dental floss to prevent contact area

from being removed. Wrap the floss and exert force around theadjacent tooth first, then move floss up and down after flosspasses through contact area.


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Articulating paper. After the occlusion is adjusted, use discoid-cleoid to

smooth amalgam.

Can also use a lightly moistened cotton pellet held in the

operative pliers

If the carving and smoothing are done properly, nosubsequent polishing of the restoration is needed good long-term result

Finishing Amalgam Restoration


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If an amalgam restoration fractures during insertion,the defective area must be reprepared as if it were asmall restoration.

Appropriate depth and retention form must begenerated, sometimes entirely within the existingamalgam restoration.

A new mix of amalgam can be condensed directly intothe defect and will adhere to the amalgam already

present if no intermediary material (sealers) has beenplaced in between

If the amalgam has been bonded, carefully conditionand apply adhesive to the exposed tooth structure

Repairing Amalgam Restoration


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Causes include:

Inadequate condensation.

Material pulling away orbreaking from the marginalarea when carving bondedamalgam.

Marginal Void

Causes include:

Lack of adequate

condensation, especiallylateral condensation in theproximal boxes.

Lack of proper dentinalsealing with sealer or

bonding system.

Postoperative Sensitivity

Common Problems


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Causes Careless handling.

Inappropriate collectiontechnique.

Potential solutions include: Careful attention to proper

collection and disposal.

Following the Best

Management Practices forAmalgam Waste aspresented by the AmericanDental Association

Amalgam Scrap and MercuryCollection And Disposal.

Causes Axiopulpal line angle not

rounded in Class II toothpreparations.

Marginal ridge left too high.

Occlusal embrasure formincorrect.

Improper removal of matrix.

Overzealous carving.

Marginal Ridge Fractures


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Controversial Issues


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Amalgam restorations are safe. The U.S. PublicHealth Service (USPHS) has reported the safety ofamalgam restorations. Even recognizing these

assessments, the mercury contained in currentamalgam restorations still causes concerns, bothlegitimate and otherwise. Proper handling ofmercury in mixing the amalgam mass, removal of

old amalgam restorations, and amalgam scrapdisposal are very important, physiologic, andeconomic manner.

Amalgam Restoration Safety.


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Spherical materials have advantages in providinghigher earlier strength and permitting the use ofless pressure.

Admixed materials permit easier proximal contactdevelopment because of higher condensationforces.

Spherical or Admixed Amalgam


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Bonded amalgam are no longer recommended,even though some operators may select them forlarge restorations.

Use of typical secondary retention formpreparation features (e.g., grooves, locks, pins, slots)are still required ifbonding an amalgam

Small-tomoderate amalgam restorations should not

be bonded its actually better to just usecomposite.

Bonded Amalgam Restorations


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Proximal retention locks for large amalgamrestorations may be beneficial, although their usefor smaller restorations is not deemed necessary.

Correct placement of proximal retention locks isdifficult.

Proximal Retention Locks

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