12. General characteristics, Advantages & disadvantages, matrices, retainers

1. General Characteristics,
Advantages & Disadvantages,
Matrices, Retainers, Wedges &
Amalgam Restoration Manipulation
& Insertion into the Cavity &
Polishing of Amalgam
Dr. Intesar S.Toma

2.  Restorative technique for Amalgam restorations:
 Matrix Placement:
• Used when a proximal surface is to be restored.
• Objective of matrix placement:
1. Provide proper contact.
2. Provide proper contour.
3. Confine the restorative material.
4. Reduce the amount of excess material.
• If proximal & contact not properly restored they may cause :
a. Food impaction leading to recurrent caries.
b. Injury to periodontium.
c. Displacement, rotation & migration of teeth
d. Disturbed balanced occlusion & intercuspal relations.
Dental Amalgam (Dental Materials)

3. • Matrix Band:
is a thin sheet or strip that pass through the contact
area (acts as a temporary wall) to provide support
during placement & condensation of restorative material.
Dental Amalgam (Dental Materials)

4. • Requirements of Matrix Band:
1. Rigidity.
2. Versatility.
3. Comfortable to use.
4. Height & contour.
5. Application.
Dental Amalgam (Dental Materials)

5. • Classification:
a. Depending upon their method of
retention.
1. Mechanically retained.
o Ivory matrix retainers no. 1 & 8.
o Universal dental matrix band retainer.
2. Self-retained.
o Copper or stainless steel bands.
b. On the basis of transparency.
1. Transparent matrices.
o Cellophane, celluloid.
2. Non-transparent matrices.
o Stainless steel.
Dental Amalgam (Dental Materials)

6. • Matrix Retainer :
* Mostly the matrix bands are held in position by means
of retainers.
o Ivory matrix retainers no. 1
o Ivory matrix retainers no. 8.
o Universal dental matrix band retainer.
Dental Amalgam (Dental Materials)

7. • Retainerless Matrix Band :
* For tilted & partially erupted teeth & for patient cannot tolerate
retainers.
o Anatomical matrix band.
o Retainerless automatrix band
o T-Shape matrix band.
o S-Shape matrix band.
o Full circle or ring bands.
Dental Amalgam (Dental Materials)

8. • Matrices for Class III direct tooth colored restorations:
o Plastic matrix strips & Mylar strips.
o Matrices for Class IV direct tooth colored restorations:
 Plastic strip.
 Prefabricated matrix form matrices.(e.g Transparent
crown & Aluminum foil).
Dental Amalgam (Dental Materials)

9. • Wedges:
 Used to stabilize matrix band & retainer (wood or plastic,
triangular or round).
 Wedges Functions:
1. Separate the teeth.
2. Depress the interproximal soft tissues thus minimize trauma.
3. Protect the dam & soft tissue from injury.
4. Assure close adaptability & stabilization of matrix band to tooth
5. Produce separation of the teeth to compensate for matrix
thickness.
6. Prevent gingival “overhang” of restoration.
Dental Amalgam (Dental Materials)

12. • Amalgam Trituration:
 Process of mixing of alloy with mercury is called Trituration.
 Alloys are commercially available in Powder, Tablet &
preproportioned form (capsule).
 Most operators prefer disposable capsules for:
1. Consistency of mix because the alloy & mercury are
preweighted.
2. Contribution to mercury hygiene.
Dental Amalgam (Dental Materials)

13.  Trituration can be carried out by hand or by mechanical device.
 Hand trituration is performed in glass mortar & pestle.
 Mechanical trituration is performed with a device Amalgamator.
Dental Amalgam (Dental Materials)

14.  Preproportioned, disposable capsules are available in size ranging
from 400 to 800 mg.
 Some precapsulated brands require activation of capsule before
trituration.
 Trituration should be carried according to manufacture direction.
 Amalgamator generally have a timer & may have speed control.
 Correctly mixed amalgam should not be dry or crumbly, it will have
sufficient “wetness” to aid on achieving a homogenous &
welladapted restoration.
Dental Amalgam (Dental Materials)

15. • Amalgam Insertion & condensation:
 The principal objectives during the insertion of
amalgam are:
 To condense the amalgam to adapt it to the preparation
walls & the matrix (when used).
 Produce a restoration free of voids.
 Helps to reduce marginal leakage.
 Optimal condensation also is necessary to minimize the
mercury content in the restoration to decrease corrosion & to
enhance strength & marginal integrity.
Dental Amalgam (Dental Materials)

16.  The outline of the tooth preparation should be reviewed
before inserting amalgam.
 An amalgam carrier is used to transfer amalgam to the
tooth preparation (small Increments).
Dental Amalgam (Dental Materials)

17.  A flat-faced, circular or elliptic condenser should be used to
condense amalgam over the pulpal floor of the preparation.
 Usually, a smaller condenser is used while filling the
preparation & a larger one for over-packing.
 The condensation pressure required depends on the
amalgam used & the diameter of the condenser nib.
Dental Amalgam (Dental Materials)

18.  The preparation should be over-packed 1 mm or more using
heavy pressure
 Final condensation over cavosurface margins should be done
perpendicular to the external enamel surface adjacent to the
margin.
 The condensation of a mix should be completed within the time
specified by the manufacturer (usually 2.5 to 3.5 minutes).
Dental Amalgam (Dental Materials)

19.  The over-packed amalgam should be burnished immediately
with a large burnisher, using heavy strokes mesiodistally &
faciolingually, which is referred to as precarve burnishing.
 To maximize its effectiveness, the burnisher head should be
large enough that in the final strokes, it contacts the cusp
slopes but not the margins.
Dental Amalgam (Dental Materials)

20. • Contouring & Finishing of the Amalgam:
 Carving may begin immediately after condensation.
 Sharp discoid–cleoid carvers of suitable sizes or
Hollenback carver can be used.
 The larger end of the discoid-cleoid instrument is used first,
followed by the smaller instrument.
Dental Amalgam (Dental Materials)

21.  Carving should be done with the edge of the blade
perpendicular to the margins as the instrument is moved
parallel to the margins.
 Part of the edge of the carving blade should rest on the
unprepared tooth surface adjacent to the preparation margin.
Dental Amalgam (Dental Materials)

22.  Deep occlusal grooves may leave a thin amalgam at the
margins, invite chipping, & weaken the restoration.
 Under-carving leaves thin portions of amalgam (subject to
fracture) on the unprepared tooth surface.
Dental Amalgam (Dental Materials)

23.  Post-carve burnishing is done by lightly rubbing the carved
surface with a burnisher of suitable size & shape.

24. • Occlusion Evaluation:
 The patient is advised not to bite because of the danger
of fracturing the restoration.
 A piece of articulating paper is placed over the
restoration & the patient is instructed to close gently into
occlusion.
 If the effect of anesthesia is still present, it may be difficult
for the patient to tell when the teeth are in contact.
Dental Amalgam (Dental Materials)

25.  Any contact area can be recognized on the amalgam by the
depth of color imparted by the paper, which are then
removed by additional carving.
 The sequence of closure, observation & carving is repeated
until the appropriate surfaces of opposing teeth are
touching.
Dental Amalgam (Dental Materials)

26.  Up to this point, the patient has been instructed to close
vertically into maximum intercuspation.
 After placing the articulating paper over the tooth, the
patient is asked to occlude lightly & to slide the teeth lightly
from side to side.
 Finally, the patient should be cautioned to protect the
restoration from any heavy biting pressure for 24 hours.
 Most amalgams do not require further finishing & polishing.
Dental Amalgam (Dental Materials)

27. • Finishing & Polishing:
 These procedures are occasionally necessary, however, to :
(1) Complete the carving.
(2) Refine the anatomy, contours, & marginal integrity.
(3) Enhance the surface texture of the restoration.
 Additional finishing & polishing procedures are not attempted
within 24 hours of insertion because crystallization is
incomplete.
Dental Amalgam (Dental Materials)

28.  Finishing procedure is initiated by marking the occlusion with
articulating paper & evaluating the margins with an explorer.
 A white alumina stone or a green carborundum stone is used
to correct the discrepancy.
 The stone’s long axis is held at a 90-degree angle to the
margins.
Dental Amalgam (Dental Materials)

29.  The polishing procedure is started by using a coarse, rubber
abrasive point at low speed & air-water spray to produce an
amalgam surface with a smooth, satiny appearance .
 It is important that the rubber points be used at low speed:
1. The danger of the point disintegrating at high speeds.
2. The danger of elevating the temperature of the restoration &
the tooth.
Dental Amalgam (Dental Materials)

30. Failure in Amalgam restoration
Dr. Intesar S. Toma
M.Sc. in Conservative Dentistry

31.  Amalgam Failure:
1. Tooth fracture:
a. Weakened tooth structure.
o Minimal removal of tooth tissue.
o Cavo-surface angles will be close 90˚.
o Use adhesive that allow bonding of amalgam to tooth tissue.
b. Undermined enamel.
o Unsupport enamel will break free & leave a gab, which lead
to recurrent caries.
c. Residual caries.
o Caries will spread & undermine the cusp.
o Leakage of bacterial toxins cause pulp inflammation.
Dental Amalgam (Dental Materials)

32. 2. Recurrent Caries:
a. Contamination.
o Blood or saliva, will result in poor adaptation of restoration
to cavity margins.
b. Poor matrix Techniques.
o Poorly adapted matrix can cause proximal overhangs or
poor contact points with adjacent teeth.
o Over-tightening of matrix band can cause cusps fracture.
c. Poor Condensation.
o Lead to porosity of amalgam & presence of excess mercury
both reduce strength.
o Marginal adaptation poor, marginal leakage, recurrent
caries & corrosion.
Dental Amalgam (Dental Materials)

33. 3. Gross Amalgam fracture:
a. Shallow preparations.
o Have low tensile strength, when placed in thin section they
subjected to bending force & will break.
b. Non-retentive proximal boxes.
o Risk reduced by cutting retention grooves in the lateral
walls & gingival floor of the boxes.
c. Sharp internal line angles.
o Increase the risk of fracture of both tooth & filling
(concentrates stress).
o Rounded internal surface should be the aim.
Dental Amalgam (Dental Materials)

34. 4. Marginal breakdown:
a. Incorrect cavo-surface angles.
o Leading to marginal fracture of enamel or amalgam.
o Should avoid undermined enamel or acute margins in
amalgam.
b. Delayed expansion.
o Zn-containing alloy with saliva cause expansion.
o Bubbles of hydrogen gas are formed within amalgam lead
to increase the pressure & expand the bubbles & cause
expansion.
o Cause pulpal pain & latter marginal breakdown.
Dental Amalgam (Dental Materials)

35. 4. Marginal breakdown:
c. Overfilling, underfilling & overcarving.
o Overfilling lead to ledge formation this will eventually fracture.
o Underfilling or overcarving can result in an acute amalgam
margin angle lead to marginal breakdown.
d. Creep & corrosion of the amalgam.
o Both Cause marginal breakdown.
Dental Amalgam (Dental Materials)

36. Thank you
Thank U
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