About prepration of amalgam cavity

1. COMPLEX AMALGAM
RESTORATIONS
DR DITHYKUMARI K K
𝑰𝒔𝒕
YEAR PG
CONSERVATIVE AND ENDODONTICS

2. INTRODUCTION
• Complex posterior restorations are used to
replace missing tooth structure of teeth that
have fractured or are severely involved with
caries or existing restorative material.
• These restorations usually involve the
replacement of one or more missing cusps.

3. INDICATIONS
• Complex posterior amalgam restorations
should be considered when:
–large amounts of tooth structure are missing
–one or more cusps need capping
–increased resistance and retention forms are
needed

4. INDICATIONS
• Control restorations in teeth that have a
questionable pulpal and/or periodontal
prognosis,
• Control restorations in teeth with acute and
severe caries,
• Definitive final restorations due to economics
or age of the patient
• Foundations

5. CONTRAINDICATIONS
• The complex amalgam restoration may be
contraindicated if :
–the patient has significant occlusal problems
–the tooth cannot be properly restored with a
direct restoration because of anatomic
and/or functional considerations
–the area to be restored is aesthetically
important for the patient

6. TYPES OF COMPLEX AMALGAM
RESTORATIONS
• Pin-Retained Amalgam Restorations
• Slot-Retained Amalgam Restorations
• Amalgam Foundations.

7. ADVANTAGES
• Conservation of tooth structure
• Appointment time
• Resistance and retention form
• Economics

8. DISADVANTAGES
• Dentinal micro fractures
• Lowered fractured resistance
• Strength of amalgam restoration is reduced
• Micro leakage
• Perforations
• Difficulty to achieve proper contours

9. PIN RETAINED RESTORATIONS

10. 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
resistance and retention forms.
• Pins are used whenever adequate resistance and
retention forms cannot be established with slots,
locks, or undercuts only.
• The pin-retained amalgam is an important adjunct
in the restoration of teeth with extensive caries or
fractures.

11. Types of Pins
1. Cemented pins
2. Friction locked pins
3. Self threaded pins

12. CEMENTED PINS
• Developed by Dr. Markley to
retain large amalgam restorations
• Made of Stainless Steel
• They are cemented into pinholes
prepared 0.001 to 0.002 inch
(0.025 to 0.05 mm) larger than
the diameter of the pin.
• They are used to build foundation
after endodontic treatment as
they produce the least amount of
stress
• Offer less resistance than the
other pins

13. FRICTION LOCKED PINS
• Developed by Dr.
Goldstein in 1966
• Made of stainless steel
• More retentive than
cemented pins
• Used in vital teeth with
good access and ease of
tapping the pins
• Cause craze lines or
cracks

14. SELF THREADED PINS
• Developed by Dr. Going
in 1966
• Most popular type among
all the different type of
pins and extensively used
• Made of stainless steel or
titanium pins
• Provide maximum
retention among all types
of pins
• Cause craze lines
• Used in vital teeth

15. CEMENTED PINS FRICTION LOCKED
PINS
SELF THREADED PINS
Stainless steel with
threads or serrations
Stainless steel with
threads
Stainless steel/Titanium
with gold plating
Pin channel [0.020” to
0.32”] larger than pin size
[0.018” to 0.30”]
Pin channel is 0.001”
smaller than pin size
Pin channel is 0.015” to
0.004” smaller than pin
size
Luted with standard luting
agents
Taped into place with
mallet
Placed by hand wrench or
contra angle hand piece
Ease of placement Pin placement is difficult Pin placement is easy

16. CEMENTED PINS FRICTION LOCKED
PINS
SELF THREADED
PINS
Less internal stresses Increased internal stress Increased internal stresses
but less as compared to
friction locked pins
Least retentive 2-3 times more retentive
than cemented pins
5-6 times more retentive
than friction locked pins

17. Factors Affecting the Retention of the Pin
in Dentin and Amalgam
• Type
• Surface characteristics.
– The number and depth of the elevations (serrations or threads)
on the pin.
• Orientation, number, and diameter.
– Placing pins in a nonparallel manner increases their retention
– Bending of pins is not desirable
– Increasing the number of pins increases the retention in dentin
and amalgam
• Extension into dentin and amalgam
– Pin extension into dentin and amalgam greater than 2 mm is
unnecessary for pin retention and is contraindicated to
preserve the strength of the dentin and the amalgam.

18. Thread Mate System (TMS)
• It is the most widely used self-threading pin
because of its:
1. Versatility of design
2. Wide range of pin sizes
3. Colour coding system,
4. Greater retentiveness
5. Gold plated surface finish, which may
eliminate the possibility of corrosion

22. Two types of Kodex twist drills: standard (a) and depth limiting (b).

24. PIN PLACEMENT FACTORS
AND TECHNIQUES

25. Pin size :
• Two determining factors for selecting pin size:
– the amount of dentin available
– the amount of retention desired.
– the pins of choice for severely involved
posterior teeth are the Minikin (0.019 inch
[0.48 mm]) and, occasionally, the Minim
(0.024 inch [0.61 mm]).
• Of the four pin sizes, the Regular pin caused the highest
incidence of dentinal cracking that communicated with the
pulp chamber. (Webb EL, Straka WF, Phillips CL. J Prosthet Dent 61(5):624-628,
1989.)

26. NUMBER OF PINS.
• Several factors must be considered when
deciding how many pins are required:
– the amount of missing tooth structure,
– the amount of dentin available to receive pins
safely,
– the amount of retention required, and
– the size of the pins.
• As a rule, one pin per missing axial line angle
should be used.

28. LOCATION OF PINS
• Factors that aid in determining pinhole
locations:
(1)knowledge of normal pulp anatomy and
external tooth contours,
(2) a current radiograph of the tooth,
(3) a periodontal probe, and
(4) the patient's age

29. LOCATION OF PINS
• Pinholes should be located near the line angles of
the tooth,
• The pinhole should be parallel to the adjacent
external surface of the tooth.
• Pinholes should be located halfway between the
pulp and the DEJ or external surface of the tooth
root
• The pinhole should be positioned no closer than
0.5 to 1 mm to the DEJ or no closer than 1 to 1.5
mm to the external surface of the tooth,
whichever distance is greater

32. The position of a pinhole must not be so close to
a vertical wall of tooth structure that
condensation of amalgam against the pin or
wall is jeopardized. A recess should be
prepared in such case.

33. Pinholes should be prepared on a flat surface that is
perpendicular to the proposed direction of the pinhole.
Whenever three or more pinholes are placed, they
should be located at different vertical levels on the
tooth, if possible

34. Inter-pin distance
• Spacing between pins, or the interpin distance,
must be considered when two or more pinholes
are prepared.
• The optimal interpin distance depends on the size
of pin to be used.
• The minimal interpin distance is 3 mm for the
Minikin (0.019 inch [0.48 mm]) pin and 5 mm for
the Minim (0.024 inch [0.61 mm]) pin.
• Maximal interpin distance results in lower levels
of stress in dentin

36. Pinhole preparation.

37. Pinhole preparation.

38. Pinhole Preparation
• The Kodex drill (a twist drill) should be used
for preparing pinholes-
• A depth-limiting drill should be used to
prepare the hole – to achieve optimal depth of
pin in dentin-2mm
• Prepare a hole on a flat surface that is
perpendicular to the drill- only then the correct
depth will be prepared.

39. Pinhole Preparation
• Place the drill in the gingival crevice beside the
location for the pinhole, position it until it lies flat
against the external surface of the tooth, and then,
• Without changing the angulation obtained from the
crevice position, move the handpiece occlusally and
place the drill in the previously prepared pilot hole
• With the drill tip in its proper position and with the
handpiece rotating at very low speed (300 to 500 rpm)
apply pressure to the drill, and prepare the pinhole in
one or two movements until the depth-limiting portion
of the drill is reached, and remove the drill from the
pinhole

42. Pinhole Preparation
• Certain clinical locations require extra care in
determining pinhole angulation
– Distal of mandibular molars and the lingual of
maxillary molars
– Teeth that are rotated in the arch
– Teeth that are abnormally tilted in the arch- e.g
Mesially tilted mandibular 2nd molars.

43. Pin Insertion.
• Two instruments for insertion of threaded pins are
available:
• Conventional latch-type contra-angle handpiece
– Recommended for the insertion of the Link Series and
the Link Plus pins
• TMS hand wrenches
– Recommended for placement of standard pins.

45. Five designs of TMS pins. A, Standard. B, Self-shearing. C, Two-in-
one. D, Link Series. E, Link Plus

46. Pin Insertion.
• A standard design pin is placed in the appropriate
• wrench and slowly threaded clockwise into the
pinhole until a definite resistance is felt when the
pin reaches the bottom of the hole.
• The pin should then be rotated one-quarter to one-
half turn counterclockwise to reduce the dentinal
stress created.
• Use rubber dam isolation or use a throat shield
and tie a floss to the pin.

48. • Once the pins are placed, evaluate their length
• Any length greater than 2mm should be
removed- with a 1/2, round bur or 169L bur
held perpendicular to pin.
• After placement, the pin should be tight,
immobile, and not easily withdrawn.

49. • Using a mirror, view the preparation from all
directions (particularly from the occlusal) to
determine if any pins need to be bent to
position them within the anticipated contour of
the final restoration and to provide adequate
bulk of amalgam between the pin and the
external surface of the final restoration.

51. Placement of cemented
pins.
A. Prepare pinholes with
appropriately sized twist drill.
B. Cut proper length of pin with
wire-cutting pliers.
C. Slightly round the end of the
pin with rotating
carborundum disc.
D. Place pins in tooth, and
evaluate need for bending.
E. Hold pin with two pairs of
pliers, and bend as necessary.
F. Pins bent.
G. Convey cement into pinholes
with a Lentulo spiral
instrument.
H. Pins cemented.

52. Failure of pin-retained restorations
• The failure of pin-retained restorations might occur
at any of five different locations:
– Within the restoration (restoration fracture)
– at the interface between the pin and the restorative
material (pin-restoration separation)
– within the pin (pin fracture),
– at the interface between the pin and the dentin (pin-dentin
separation)
– Within the dentin (dentin fracture)
• Failure is more likely to occur at the pin-dentin
interface than at the pin-restoration interface

53. Procedural problems encountered
• Broken drills and broken pins.
• Loose pins.
• Penetration into the pulp and perforation of the
external tooth surface.

54. Pulpal Penetration/Perforation
• A pulpal penetration is treated as any other small
mechanical exposure.
• Place a calcium hydroxide liner over the opening
of the pinhole, and prepare another hole 1.5 to 2
mm away.
• Regardless of the method of treatment rendered,
the patient must be informed of the perforation or
pulpal penetration at the completion of the
appointment.

55. Perforation of the external tooth
surface.
• Perforation of the external surface of the tooth can
occur occlusal or apical to the gingival attachment.
• Perforations that occur occlusal to the gingival
attachment:
1) The pin can be cut off flush with the tooth surface and no
further treatment rendered,
2) The pin can be cut off flush with the tooth surface and the
preparation for a cast restoration extended gingivally
beyond the perforation,
3) The pin can be removed, and the external aspect of the
pinhole enlarged slightly and restored with amalgam.

56. Perforation of the external tooth
surface.
• Perforations that occur apical to the gingival
attachment:
1) Reflect the tissue surgically, remove the
necessary bone, enlarge the pinhole slightly, and
restore with amalgam.
2) Perform a crown lengthening procedure, and
place the margin of a cast restoration gingival to
the perforation

58. SLOT-RETAINED AMALGAM
RESTORATIONS.

59. Slot-Retained Amalgam
Restorations.
• Slots are horizontally prapred channels in dentine.
• The slot is at least 0.5 mm in depth and 1 mm or more
in length depending on the distance between the
vertical walls
• Slots are usually placed on the facial, lingual, mesial,
and distal aspects of the preparation
• The slot may be continuous or segmented, depending
on the amount of missing tooth structure.
• Shorter slots provide as much resistance to horizontal
force as do longer slots.
• Slots can be used in combination with pins to generate
additional retention and resistance forms.

61. Slot preparation
• A No. 33'/2 (Inverted cone) bur is used to
place a slot in the gingival floor 0.5 mm axial
of the DEJ.
• An alternative technique is to prepare the slot
initially with a No. 169L bur. Then, ensure its
convergence by refining it with a No. 331/2
bur.

62. AMALGAM FOUNDATIONS

63. Amalgam Foundations
• A foundation is an initial restoration of a severely involved tooth.
The tooth is restored so that the restorative material (amalgam,
composite, or other) will serve in lieu of tooth structure t provide
retention and resistance forms during the development of the
subsequent final cast restoration.
• A foundation is indicated for a tooth that is severely broken down
and lacks the resistance and retention forms needed for an indirect
restoration
• Foundations are placed in preparation for a full crown,
especially in endodontically treated teeth.

64. Amalgam Foundations
• The amalgam foundation restorations mainly
rely on Chamber Retention.
• If the height of available pulp chamber is 4-
6mm adequate retention can be gained by
filling from the orifices.
• If the height of available pulp chamber is 2mm
or less extension into the root canal space 2 to
4 mm is recommended