all about complex amalgam

1. COMPLEX AMALGAM
RESTORATION

2. CONTENTS
INTRODUCTION
HISTORY
INDICATIONS
CONTRAINDICATIONS
ADVANTAGES
DISADVANTAGES
TYPES OF COMPLEX AMALGAM RESTORATIONS
1. CUSPAL-COVERAGE
2. PIN- RETAINED AMALGAM RESTORATIONS
3. AMALGAPINS

3. 4. SLOT-RETAINED AMALGAM RESTORATION
5. AMALGAM FOUNDATIONS
6. BONDED AMALGAM RESTORATIONS
STEPS IN RESTORATION
1. Matrix & Amalgam placement
2. Finishing the amalgam restoration
DISCUSSION
CONLUSION
REFERENCES

4. INTRODUCTION
Historically, the term Complex Amalgam
Restorations was referred to one that
involved three or two surfaces of a tooth.
The term has been redefined in recent
years.
Complex amalgam restorations are
restorations used to replace missing tooth
structure of teeth that has been fractured
or are severely involved with caries or
existing restorative material. These
restorations usually involve the
replacement of one or more missing cusps

5. HISTORY
1871 a metallic pin was patented that was to be
inserted firmly in the tooth to provide a
connection between tooth and restorative
material.
1872 dental manufacturers advertised screw pins
and drills for taping of holes in dentin
1890 self-shearing pins were available
1897 an article was published concerning when,
where and how to anchor screws.
The threaded iridoplatinum wire cemented into a
pin channel prepared with no 2 round bur is the
forerunner of todays present pin.
GILMORE

6. INDICATIONS
1 As interim restorations for teeth that require
elaborate occlusal alterations ranging from
vertical dimension changes to correcting
occlusal plane discrepancies.
2 Economics
3 Age & Health of patient- In geriatric patients.
CONTRAINDICATIONS
1 Patient with significant occlusal problems
2 If the area is esthetically important for the patient
3 If the tooth cannot be restored because of
anatomic and/ or functional considerations

7. ADVANTAGES
1-Conserves Tooth Structure– preparation
for complex amalgam restoration is more
conservative than for an indirect
restoration.
2-Appointment time – Restoration can be
completed in single appointment.
3-Economics – Inexpensive as compared
to cast restoration.

8. DISADVANTAGES
1-Dentinal micro fractures – Drilling pin holes
and placing pins can cause micro fractures in
dentin and development of internal stresses in
dentin.
2-Micro leakage – This can occur in pin –
restoration interface.
3-Decreased strength of amalgam –
Compressive strength of amalgam is not
affected whereas tensile and transverse strength
are decreased.
4-Perforation – Risk of perforation into pulp or
external tooth surface.

9. TYPES OF COMPLEX AMALGAM
RESTORATION

10. CUSPS CAPPING
When caries is extensive, reduction of one or
more of the cusps for capping may be indicated.
When the facial or lingual extension exceeds two
thirds the distance from a primary groove toward
the cusp tip (or when the facial-lingual extension
of the occlusal preparation exceeds two thirds
the distance between the facial and lingual cusp
tips), reduction of the cusp(s) for amalgam is
indicated

12. TOOTH PREPARATION
If the cusp(s) to be capped is located at the correct occlusal
height from preparation, depth cuts should be made on
the remaining occlusal surface of each cusp to be
capped.
Make depth gauge cuts of 2mm for functional cusps and
1.5mm minimum for nonfunctional cusps on each cusp
to be capped.
Uniform reduction is ensured using the depth gauge cut
as a guide.
Rounden any sharp external corners at the junction of the
cusp-reduced surface to decrease stress concentration
in the capping amalgam and so improving the resistance
to occlusal forces

14. When reducing only one or two facial or lingual
cusps, the cusp reduction should be extended
just past the facial or lingual groove, creating a
vertical wall against the adjacent unreduced cusp.
When possible, opposing vertical walls should be
formed to converge occlusally, to enhance
primary retention form

15. • Pulpal and gingival walls should be flat and
perpendicular to the long axis of the tooth.
• For auxillary resistance and retention pins, slots
or coves can be prepared.
• Coves are prepared in horizontal plane and
locks are prepared in a vertical plane.
• Slots may be prepared along the gingival floor,
axial to the DEJ.

16. PIN-RETAINED AMALGAM
RESTORATION

17. DEFINITION
A Pin retained restoration may be defined as any
restoration requiring the placement of one or more pins
in the dentin to provide adequate retention form.
INDICATIONS
1-For restoration of mutilated and badly broken down
teeth especially in young patients where the gingival
lines are still high, where massive tooth preparations
necessitated by cast restorations are
contraindicated.

19. 2- Badly broken down teeth, prior to endodontic or
orthodontic treatment, pin retained restorations
are placed as a transitional restoration to act as
a build up for rubber dam application or band
attachment.
3- As a foundation for partial or full veneer cast
restoration or metal ceramic restorations,
thereby saving considerable amount of tooth
structure by eliminating the need to remove
undercuts.
4-As a provisional restoration in teeth with
questionable prognosis endodontically or
periodontally, until a definitive prognosis is
established.

20. 5 In preparations where adequate retention form
cannot be established with slots, locks or
undercuts, pins are used as a means of providing
auxiliary retention.
ADVANTAGES
1 Conservation of tooth structure – pin hole
preparation is more conservative than slot
preparation.
2 Appointment time – Restoration can be completed
in single appointment.
3 Economics – Inexpensive as compared to cast
restoration

21. DISADVANTAGES
1 Dentinal micro fractures – Drilling pin holes
and placing pins can cause micro fractures in
dentin and development of internal stresses in
dentin. This is significant when minimal dentin is
present.
2 Micro leakage – This can occur in pin –
restoration interface.
3 Decreased strength of amalgam –
Compressive strength of amalgam is not
affected whereas tensile and transverse strength
are decreased.
4 Perforation – Risk of perforation into pulp or
external tooth surface

22. TYPES OF PIN
Cemented pins:
It was introduced in 1958 by Dr. Miles
Markley. In this type, the pin channel
diameter is 0.025 to 0.05mm larger
than the diameter of the pin.
It comes in two sizes
Pin Channel Diameter Pin
Diameter
0.027 0.025
0.021 0.020

23. • Friction lock pins:
Goldstein in 1966 introduced the friction locked
pin technique. In this type, the pin channel
diameter is 0.025 mm narrower than the pin
diameter. These pins are 2-3 times more
retentive than cemented pins.
It comes in one size Pin Channel Diameter is
0.021 and Pin Diameter is 0.022

24. • Self-threading pins
It was introduced by Going in 1966. The pin
channel diameter is 0.038 to 0.05 mm narrower
than that of the pin. The pin is retained by
threads engaging the dentin as it is inserted.
The elasticity (resiliency) of the dentin allows
insertion of a threaded pin into a hole of smaller
diameter. It is 3-6 times more retentive than
cemented pins. Lateral and apical stresses can
be generated in dentin when a self threading pin
is inserted

25. Friction lock Self-threading Cemented

26. Cemented
Friction lock
Self-threading

28. The Thread Mate System (TMS) is the most
widely used self threading pin because of its
1 Versatility
2 Wide range of pin sizes
3 Color – coding system
4 Greater retentiveness
5 Gold-plated pins, which may eliminate the
possibility of corrosion

29. • The TMS pins are available in four sizes depending
on the diameter of the pin namely
1. Regular – 0.78 mm 3. Minikin – 0.48mm
2. Minim - 0.61 mm 4. Minuta – 0.38 mm

30. Regular - back up for minim
Minim - most situations
Minikin -small anterior teeth
Minuta - rarely used

31. For each of the four sizes, several designs are
available namely
1. Standard design:
These pins are 7 mm in length and should be
shortened after seating in the pin channel.
2.Self-shearing design:
These pins automatically shears off at 4mm from
the dentinal end, when this end comes in contact
with the pin channel floor.

32. 3.Twin stage or Two in one design:
In this type two pins are joined together end to end but
separated by a shear line. The wrench attachment part
is on one end only. After threading the peripheral stage
(peripheral pin), it will separate from the wrench
attachment stage as soon as it contacts the pin channel
floor. Another pin complete with its wrench attachment
will remain, to be used in another pin channel.
4 The Link Series pin is contained in a color coded
plastic sleeve that fits in a latch type contra-angle
hand piece. The pin is somewhat free floating in the
plastic sleeve to allow it to align itself as it is
threaded into the pin hole.

33. When the pin reaches the bottom of the hole, the top
portion of the pin shears off, leaving a length of pin
extending from the dentin. The plastic sleeve is then
discarded.
5 The Link Plus pins are self-shearing and are
available as a single or two in one pin contained in a
color-coded plastic sleeve. This design has a
sharper thread, a shoulder stop at 2 mm and a
tapered tip to more readily fit the bottom of the pin
hole as prepared by the twist drill. It also provides a
2.7mm length of pin to extend out of the dentin

34. FACTORS AFFECTING THE RETENTION OF THE PIN IN
DENTIN AND AMALGAM
1 Type of pin:
In order of retentiveness, self-threading pin is
most retentive, friction lock pin is intermediate
and cemented pin is the least retentive.
2 Surface characteristics:
Retention of the pin in amalgam is influenced
by the number and depth of elevations in the
pin. Therefore, self-threading pins are most
retentive.
3 Orientation of the pins:
Retention of the pins is increased by placing
them in a non-parallel manner.

35. 4 Number of pins:
Within limits, increasing the number of pins increases
the retention in dentin and amalgam.
Pins placed closer than 2 mm in dentin to each other
in one tooth will result in -
a Crazing of dentin and increased potential for
fracture.
b Decrease in the amount of available dentin
between the pins.
c Strength of amalgam restoration decreases.
5 Diameter of the pins:
Within limits, as the diameter of the pin increases the
retention in dentin and amalgam increases.

36. 6 Extension into dentin and amalgam:
Pin extension into dentin and amalgam greater
than 2 mm is unnecessary for pin retention and
contraindicated to preserve the strength the
dentin and amalgam.
7 Bending also weaken the pin and risk fracturing
the dentin. Pins should be bent to provide
adequate amount of amalgam 1mm between the
pin and external surface of finished restoration

37. PIN PLACEMENT FACTORS
Pin size:
Two determining factors for selecting the
appropriate size of the pin are:
1. The amount of dentin available to safely
receive the pin
2. Amount of retention desired.
There is a gradual increase in pin retention to
restorative material with increasing pin diameter
up to 0.035 inch. Any diameter larger than this
will have no significant increase in retention

38. • Number of pins:
Factors to be considered regarding the number of
pins required are :-
1 Amount of missing tooth structure
2 Amount of dentin available to receive pins safely
3 Amount of retention required
4 Size of the pins
5 As a rule one pin per missing axial line angle
should be used.
6 When only 2-3 mm of the occluso-gingival height
of a cusp has been removed, no pin is required
because enough tooth structure remains to
prepare conventional retention

39. Location of pin holes:
Several factors aid in locating pin holes.
1 Knowledge of normal pulp anatomy and external
tooth contours.
2 A current radiograph of the tooth.
3 Periodontal probe
4 Patient’s age
Caputo and Standlee stated Ideal conditions for
pin hole location-
Pin holes should be located half way between
the pulp and the DEJ or external surface of the
tooth root.

40. • There should be at least 1 mm of sound dentin
around the circumference of the pin hole which
assures proper distribution of occlusal forces.
Pin placement allowing at least 1 mm of
remaining dentin thickness elicits minimal pulpal
inflammatory response.
• The pin hole should be positioned no closer than
1 mm to the DEJ and no closer than 1.5 mm to
the external surface of the tooth.
• Pin holes should be located on a flat surface that
is perpendicular to the proposed direction of the
pin hole.

42. Horizontal pins may be used to splint remaining
cusps together to reduce cusp flexture when
there is sufficient remaining dentin in which to
prepare pin hole channel.

43. Whenever three or more pin holes are placed, they
should be located at different levels of the tooth
so that stress resulting from pin placement in the
same transverse plane of the tooth is prevented.
When two or more pins are placed, the inter pin
distance should not be less than 2 mm. Inter pin
distances less than this will cause a definite
reduction in pin retention with the restorative
material

45. Anatomical features that may preclude safe pin
hole placement should be considered. External
perforation may result in pin hole placement
over the-
1 -Prominent mesial concavity of maxillary first
premolar
2 -At the mid-lingual and mid-facial bifurcations
of the mandibular first and second molars.
3 -At the mid-facial, mid-mesial and mid-distal
furcations of maxillary first and second molars

46. PINHOLE PREPARATION
When the pin hole location has been determined, with
a No.1/4 bur, a pilot hole is prepared approximately
one half the diameter of the bur at each location.
• The Kodex drill or twist drill is used for drilling pin
holes.
• Two types of Kodex twist drill --Standard & Depth
limiting.
• It is made of high-speed tool steel that is swaged
into an aluminum shank.
• The aluminum shank acts as a heat absorber.
• It is color coded to easily match with sizes

48. • It is an end cutting , revolving instrument with
two blades, bibevelled in longitudinal section at
precisely the same distance from the tool’s
center.
• The sides of the drill are helix shaped allowing
the escape of debris during end cutting.
• The depth can be measured using a Omni-
Depth Gauge

49. KODEX Drill should be used at low speeds of
300-500RPM.The drill should be sharp. It should
be used in direct cutting acts, with forces applied
to the long axis of the drill .The drill should be
revolving while inside the pin channel. Do not
use pumping strokes, as it will widen the pin
channel.

50. PIN INSERTION
Self Threading Pins
Four instrument for insertion of pin are available-
1 latch-type contra angle hand piece
2 TMS hand wrenches .
3 The Cable Pin setter (Loma Linda)
4 TMS auto clutch drive hand piece

51. Cemented Pin
• After the pin channel is prepared a piece of wire
is cut to the designated length and tried in the
pin channel for proper fitting and protrusion in
the restoration.
• After try in, a groove is established at the
desired length (shear line) and the rest of the
wire is used as a handle to seat the pin.
• The rest of the wire can be separated from the
pin after the cementation by simply bending it.

52. • A standard design pin is removed carefully
placed in the appropriate Wrench and slowly
threaded into the pinhole until a definite
resistance is felt when the pin reaches the
bottom of the hole.
• The pin should be then rotated ¼ or ½ turn
counter clock-wise to reduce dentinal stress
created by the end of the pin pressing the dentin

53. Earlier it was used for extensive class five
restoration for two purposes-
1) Restoration is held snugly against the axial
wall to minimize fluid exchange.
2) Placement of pin in both apical and oclusal
direction the restoration itself tends to reinforce
the tooth.

54. CUTTING OF PINS:
• To cut excess pin, a No.1/4 or ½ size or
No.169L bur at high speed is oriented
perpendicular to the pin.
• If otherwise the rotation of the bur can unwind
and loosen the pin.
• During cutting a steady stream of air is to be
oriented towards the pin.
• The pin should be stabilized with a cotton pliers
or a hemostat

55. BENDING PINS:
• The bending of pin is done to provide adequate
bulk of amalgam between the pin and the
external surface of the final restoration
• A TMS bending tool is used to bend the pin.
• Place the bending tool on the pin where it is to
be bent, and with firm controlled pressure, rotate
the bending tool until the desired amount of bent
is achieved

57. Failure of Pin Retained Restorations- might occour
at five different locations

58. Broken Drills and Pins
• Twist drills may break if it is stressed laterally or allowed
to stop rotating before being removed from the pin hole.
• Standard pin might break if turned more than needed to
reach the bottom of the pin hole.
• Pins may also break if care is not exercised during
bending
Loose Pins
Self-threading pins sometimes do not properly engage the
dentin because the pin hole was inadvertently prepared
A properly placed pin can be loosened while being
shortened with a bur, if the bur is not held
perpendicularly to the pin and stabilized.
Penetration into the pulp and perforation of external tooth
surface.

59. AMALGAPINS
The Amalgapin channel described by Shavell 1980
was prepared with a no 1156 bur and had depth
of 3mm. The margin of the channel entrance
was beveled to decrease stress concentration in
the amalgam.

60. Tooth Preparation for Slot-Retained Amalgam
Restoration-
• A slot is a retention groove in dentin whose
length is in a horizontal plane Slot retention are
used in preparations with vertical walls that allow
retention locks to oppose one another.
• Slots are particularly indicated in short clinical
crowns and in cusps that have been reduced 2
to 3mm for amalgam.
• Slots are less likely to create micro fractures in
the dentin and to perforate the tooth or penetrate
the pulp

61. • Slot length depends on the extent of the tooth
preparation. Slots are usually placed on the facial,
lingual, mesial and distal aspects of the preparation.
• Using a No.331/2 bur a slot is placed in the gingival floor
0.5mm axial of the DEJ.
• The slot is at least 0.5mm in depth and 1mm or more in
in length depending on the distance between the vertical
walls.

62. AMALGAM FOUNDATION
A foundation is an initial restoration of a severely
involved tooth. The tooth is restored so that the
restorative material will serve in lieu of tooth
structure to provide retention and resistance
forms during the development of the subsequent
final cast restoration.

63. Tooth preparation technique depends on the type
of retention needed:-
1. PIN RETENTION
2. SLOT RETENTION
3. CHAMBER RETENTION (In case of
endodontically treated teeth)
PIN RETENTION
Severely broken down with few or no vertical
walls, where an indirect restoration is indicated,
may require a pin-retained foundations.

64. For Foundation-
1.The pin holes must be farther from the external
surface of the tooth (farther internally from DEJ).
2.More bending of pins may be necessary to
allow for adequate axial reduction of the
foundation without exposing the pins during cast
metal tooth preparation.
Location of pin hole from external surface of tooth
foundation depends on-
1. Occlusogingival location of the pin (External
morphology of pin).

65. 2. Type of restoration to be placed (A porcelain-
fused-to-metal or all-ceramic preparation
requires more reduction than a full gold crown).
3. Type of margin to be prepared.
• Preparation with heavily chamfered margins at
a normal occlusogingival location require pin
placement at a greater axial depth

66. SLOT RETENTION
• Slots are placed in the gingival floor of a
preparation with a No.33 ½ bur.
• Foundation slots, as with pins, are placed
slightly more axial (farther inside the DEJ) than
indicated for conventional foundations.
• Number of remaining vertical walls determines
the indication for slots.
• Slots are used to oppose retention locks in
vertical walls or to provide retention where no
vertical walls remain.

67. • Retention locks are placed in remaining vertical
walls with a No.169L or ¼ bur.
• Slots are generally 0.5mm to 1mm in depth and
the width of the No.331/2 bur.
• Length is usually 2 to 4mm, depending on the
distance between the remaining vertical walls.
CHAMBER RETENTION
Nayyar et al has described this technique for
developing foundations in multirooted
endodontically treated teeth. It is recommended
only when-

68. 1. Dimension to the pulp chamber is adequate to
provide retention and bulk of amalgam.
2. Dentin thickness in the region of pulp chamber
is adequate to provide rigidity and strength to
the tooth.
Kane et al demonstrated that the extensions into
the root canal space 2 to 4mm is recommended
when pulp chamber height is 2mm or less.
• Retention form is provided by natural undercuts
in the pulp chamber and divergent canals.

69. • Resistance form is provided by ginigival
extension of crown preparation 2mm beyond the
foundation onto sound tooth structure

70. BONDED AMALGAM RESTORATIONS
• Bonded amalgam restorations are restorations,
which adhere to the underlying tooth structure
through a resin mediated inter locking.
• The use of adhesive resins helps in improving
the retention, resistance, and the marginal seal
of the amalgam restorations.
• The amalgam bonding systems require dual
characteristics to achieve optimal wetting, as
amalgam is strongly hydrophobic, whereas
enamel and dentin are hydrophilic.

71. • So, typical dentin bonding systems have a
wetting agent of which 4-methyloxy ethyl
trimellitic anhyride(4-META) is frequently used.
• Adhesives used for amalgam must be self-curing
or dual-curing one.

72. BONDING INTERFACE:
• The tooth restoration interface is composed of
the tooth, intervening resin and amalgam.
• The tooth resin bond includes tag formation,
formation of micromechanical locking

73. Although there is great promise for future amalgam
bonding materials, dentist should be cautious
about proven resistance and retention features
in favor of amalgam bonding. Until clinical
research data are available to support efficacy of
bonding as sole provider of resistance and
retention, resin bonding agent should be used
only in conjunction with proven mechanical
forms of resistance and retention.
S.Schwartz

74. STEPS IN RESTORATION
Matrix and Amalgam Placement
The primary function of the matrix is to restore
anatomic contours and contact areas.
1 Confine the amalgam so that adequate
condensation forces can be applied.
2 Restrict extrusion of amalgam to avoid overhang.
3 Impart an acceptable surface, especially in the
area of contact that cannot be carved and
burnished.
4 Matrix for the complex amalgam should provide
the shape of the missing cusps that will be formed
by the amalgam

75. Modeling compound supported matrices will
stabilize and maintain the matrix shape. After the
placement of matrix, wedge and contouring the
compound is heated over aflame and softened
compound is compressed against the matrix with
a wet gloved finger. The compound supported
matrix can be shaped into the desired form

76. • Copper-band matrices can be used for
providing contour and shape for achieving the
additional height if required.
• The bands are thick so in the areas that will form
the proximal contacts must be thinned using a
sandpaper disk. due to its thickness they can be
used intact only on teeth in which both mesial
and distal contacts are to be restored

77. AUTOMATRIX
The Automatrix is a retainer less matrix system
designed for any tooth regardless of its
circumference and height. Its band are supplied
in three widths 3/16, ¼, 5/16 inch.
ADVANTAGES
1 Convenience
2 Improved visibility because of absence of
retainer
3 Ability to place autolock loop on facial or lingual
surface of tooth
4 Decreased time for application

78. DISADVANTAGES
1 The band is flat and difficult to burnish and is
sometimes unstable even when wedges are in
place
2 Development of proper proximal contours and
contacts can be difficult.

80. Finishing The Amalgam Restoration
After the amalgam is condensed , the matrix
is removed, the restoration is carved first in
the interproximal areas and then on the
occlusal.
• The shape of the restoration is produced, the
occlusal anatomy is formed and rubber dam
is removed
• The objectives of polishing the amalgam
restoration are:
-- Refinement of the margin
-- Development of the contour
-- Smoothening of the surface

81. The resultant amorphous polished layer will
be less susceptible to corrosion more
esthetic and comfortable, and no more liable
to collection of plaque and debris than the
adjacent tooth surface .
The polishing procedure retards tooth
discoloration, minimizes marginal
breakdown and adds many years of service
to the amalgam restoration.

82. DISCUSSION
Smales et al in 1991 showed an annual failure rate of 6.3%
for spherical alloy.
Osborne et al compared clinical performance of five
gamma 2 alloy after 14 year of clinical service and found
loss rate of 16% for gamma 2 containing group with
8.2% for non-gamma alloy.
Smales and Hawthorne found a survival rate of 66.7% after
10 year and 47.8% after 15 year for large cuspal-
replacement in Australia.
Plasmans et al found that restoration that replaced at least
one cusp, in molar found a retention rate of 88% after 8
years.
Advances in Operative dentistry vol 2

83. CONCLUSION
Complex amalgam restorations are restorations
being less frequently used due to the advent of
other restorative materials and techniques.
Due to the increasing benefits of these materials
and techniques there are different types of
auxiliary retention forms and different variations
of tooth preparations that requires the operator
to be familiarized with the various techniques,
that can be used on a regular basis

84. REFERENCES
• THE ART AND SCIENCE OF OPERATIVE
DENTISTRY– STURDEVANT 4th Edition
• OPERATIVE DENTISTRY— MARZOUK
• OPERATIVE DENTISTRY– SCHWARTZ
• PRINCIPLES AND PRACTICES OF
OPERATIVE DENTISTRY– CHARBENEAU
• SIKRI – 2nd Edition
• OPERATIVE DENTISTRY - GILMORE