Complex posterior restorations are indicated when tooth structure is missing due to cusp fracture, severe caries lesion development,

1. Clinical Technique for
Complex
Amalgam Retoration
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Amir Rajaey
NKUM 2019-2020

2. Indication
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Complex posterior restorations
tooth structure is missing due to cusp:
 Fracture
 severe caries lesion development
 replacement of existing restorative material is necessary.
Complex amalgam preparations
 large amounts of tooth structure are missing
 one or more cusps need to be covered
 increased resistance and retention
 forms are needed
Complex amalgams may be used as
1. definitive (final) restorations
2. foundations,
3. control restorations in teeth that have a questionable pulpal or
periodontal Prognosis
4. control restorations in teeth with acute or severe caries lesions.

3. the factors must be considered
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 Resistance and Retention Forms
 Status and Prognosis of the Tooth
 Role of the Tooth in Overall Treatment Plan
 Occlusion and Economics
 Age and Health of Patient
older and debilitated patients preferred over the
more expensive and time consuming indirect
restoration.

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Resistance and Retention Forms
insufficient remaining tooth structure =>
inadequate conventional retention => the
retention form enhanced => auxiliary features
such as slots and pins (remaining vertical walls are
inadequate).
The type of retention
• amount of tooth structure remaining
• the tooth being restored
As more tooth structure is lost, more auxiliary retention is
required.

5. Status and Prognosis of the Tooth
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control restoration:
• require endodontic therapy
• crown lengthening
• uncertain periodontal prognosis
control restoration helps
1. protect the pulp
2. anatomic contour consistent with gingival health
3. control caries risk
4. Resistance fracture.
the status and prognosis determine:
the size, number, and placement of retention features.
Larger restorations generally require more retention.

6. Role of the Tooth in Overall Treatment
Plan
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• Abutment teeth for fixed prostheses may use a complex
restoration as a foundation

7. Occlusion and Economics
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 When cost of indirect
restorations is a major factor for
the patient
 Indicated as interim restorations
for vertical dimension, occlusal
plane.

8. Contraindication
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 anatomic or functional considerations
(or both) cannot be restored
 esthetic importance

9. Advantage
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 Conservation of Tooth Structure
conservative than the preparation for an indirect
restoration.
 Appointment Time
completed in one appointment.
 Reduced Cost
 Resistance and Retention Forms
cusp coverage increase the fracture
resistance of weakened teeth compared with
amalgam restorations without cusp coverage.

10. Disadvantage
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 Tooth Anatomy
Proper contours and occlusal contacts and anatomy are sometimes
difficult
 Resistance Form
• difficult to develop compared to the preparation of a tooth for a cusp-
covering onlay or a full crown.
• does not protect the tooth from fracture as effectively as a full-coverage
indirect restoration.

11. Tooth Preparation for
Complex
Amalgam Retoration
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Preparation for Cusp Coverage Complex Amalgams
 Extensive caries lesion with resultant loss of dentin
necessary to support occlusally loaded areas of
the tooth
 The facial or lingual extension exceeds two thirds the
distance from a primary fissure toward the cusp tip is
required for resistance form
 coverage reduces the risk of fracture

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resistance form creation
Reduction during the initial tooth preparation
because it improves access and visibility.
(B,C) depth cuts, minimum of 2 mm for
functional cusps and 1.5 mm for
nonfunctional cusps. (orients the bur parallel
to the cuspal incline)
(F,G) If only one of two facial (or lingual)
cusps is to be covered, the cusp reduction
should extend slightly beyond the facial (or
lingual) groove area to create a 90-degree
cavosurface margin. this approach results in
adequate thickness and edge strength of the
amalgam
Any sharp internal corners should be rounded
to reduce stress concentration

14. 14Cusp reduction and coverage reduce the amount of vertical preparation wall
height and increase the need for the use of secondary retention features

15. Mandibular First Premolar
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The lingual cusp may need to be
reduced if the lingual margin of the
occlusal step extends more than two
thirds the distance from the central
fissure to the cuspal eminence.
retention is severely diminished when the
cusp is over reduced resulting in
elimination of the lingual wall of the
occlusal portion.
Depth cuts of 1.5 mm

16. Maxillary First Molar
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 the lingual groove may be extended intentionally to increase the
retention form (B and C).
 Secondary retention when the divergence of proximal walls
limited primary retention.

17. Mandibular First Molar
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 Reducing the distal cusp is an alternative to extending the entire distofacial wall when the occlusal margin crosses the cuspal eminence.
 2 mm reduction.
 Butt joint between the tooth structure and amalgam
 When possible, reducing distal cusp is more desirable than extending the distofacial proximal margin because this conserves tooth structure
of the functional cusp, and the remaining portion of the cusp helps in applying the matrix for the development of proper distofacial
embrasure form.
 Mesiodistally the plane of the reduced cusp should parallel the facial (or lingual) outline of the unreduced cusp and the cuspal incline
emerging from the central groove faciolingually.
B, Entire distal cusp included in preparation
outline form.

18. Tooth Preparation for Slot-Retained
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 A slot is a horizontal retention groove in dentin.
 2 to 4 mm loss of vertical coronal height
(secondary retention).
 with a No. 330 bur
 1 mm wide and 1 mm deep
 Placed in the line-angle areas of the tooth
 2 to 4 mm in length
 0.5 to 1 mm inside the DEJ
 one slot per missing axial line angle should be
used
 may be continuous or segmented (depending on
the amount of missing tooth structure and whether pin retention)
 internal walls be convergent

19. In addition to slot …..
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remaining vertical walls:
• retention grooves
• coves

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21. Tooth Preparation for Pin-Retained
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 parapulpal retention pin, pin-retained amalgam,
pin-amalgam
 loss of 4 mm or more of vertical coronal height
 Resistance and retention forms are not able to be
established with slots, grooves, or undercuts only.
 Pins placed into prepared pinholes or pin channels.
 pins decreases the tensile and horizontal strength
of amalgam
 most frequently used type is the self-threading.

22. Pinhole preparation
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 diameter of pinhole is smaller than the
diameter of the pin
 threads engage dentin as the pin is inserted,
thus retaining the pin.
 elasticity of dentin permits insertion
 depth of the pinhole from 1.3 to 2 mm,
depending on the diameter of the pin used,
Recommended 2 mm
 Thread Mate System (TMS) most widely used
1. Versatility
2. wide range of pin sizes
3. color-coding system
4. greater retentiveness

23. Pin Placement Factors and Techniques
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Pin Size
color-coded drill
Selecting appropriate-
sized pin
1. the amount of dentin
available to safely
receive the pin and
2. the amount of
retention desired.

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Number of Pins
Pin Placement Factors and Techniques
1. the amount of missing tooth structure
2. the amount of dentin available to safely
receive the pins
3. the amount of retention required
4. the size of the pins.
 one pin per missing axial line angle should be used
 excessive number of pins may fracture the tooth

25. Pin Placement Factors and Techniques
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Pinhole Location
1. knowledge of normal pulp anatomy and external
contours
2. a current radiograph of the tooth
3. a periodontal probe,
4. the patient’s age.
 placement where the greatest bulk of amalgam
 Occlusal clearance should be sufficient to provide
2 mm of amalgam over the pin.
 In the cervical third of molars and premolars.
 near the line angles of the tooth
 no closer than 0.5 to 1 mm to the DEJ
 no closer than 1 to 1.5 mm to the external surface
of the tooth
 parallel to the adjacent external surface of the
tooth

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minimum 0.5mm clearance
around the circumference
of the pin for adequate
condensation of amalgam

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 optimal interpin distance depends on the size of pin  Fluted and furcal areas should be avoided

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29. Pinhole Preparation
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1. A pilot hole (dimple) is placed in the
horizontal dentin surface
2. the correct size twist drill (based on
the pin size)

30. Pinhole Preparation
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3. the twist drill is placed in the gingival crevice
beside the location for the pinhole and
positioned such that it lies flat against the
external surface of the tooth
4. without changing the angulation obtained
from the gingival crevice position, the
handpiece is moved occlusally and the drill
placed in the previously prepared pilot hole
5. the drill is then viewed from a 90-degree angle
to the previous viewing position to ascertain
that the drill also is angled correctly in this
plane

31. Pinhole Preparation
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6. with the drill tip in its proper position and with the
handpiece rotating at very low speed (300–500
rpm), pressure is applied to the drill until the
depth-limiting portion of the drill is reached
7. the pinhole is prepared in one or two
movements without allowing the drill to stop
rotating. While still rotating, the drill is
immediately removed from the pinhole

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