This document discusses pin-retained amalgam restorations for teeth with extensive caries or fractures. It describes the advantages as conserving tooth structure and providing increased resistance and retention compared to cast restorations. Potential disadvantages include dentinal microfractures, microleakage, and decreased amalgam strength. Factors that affect pin retention such as pin type, size, orientation, and number are examined. Guidelines for cavity preparation and pin placement based on tooth anatomy and pulp location are provided. Common problems and their solutions are also outlined.

1. 26/05/33
MANAGEMENT OF
BADLY BROKEN DOWN
TEETH II
2012
PIN--RETAINED AMALGAM RESTORATION
Defined as any restoration requiring the placement off one or more
pins in the dentin to provide adequate resistance and retention
forms.
Used whenever adequate resistance and retention form cannot be
established with slots, locks, or undercuts only.
1

2. 26/05/33
Indication:
 It is indicated for tooth with extensive caries or fractures.
 Rarely used in anterior teeth(Bonding Technique).
 In class V is rare (horizontal groove in the gingival & occlusal
aspect).
 Can be used with cast restoration
ADVANTAGES:
 Conservation of tooth structure
 Save time vs.. cast restoration
 Economic
 Provide ↑ resistance & retention form
2

3. 26/05/33
DISADVANTAGE:
 Dentinal micro-facture or crazing
 Microleakage around pin
 ↓ strength of amalgam
 Perforation of the pulp or external tooth structure
3

4. 26/05/33
Cavity preparation
 The cavity preparation for mutilated teeth through
excavation of carious dentin and removal of all undermined
enamel. The dentin floor must be sound . The rim of the
preparation in the damaged areas is then squared to resemble
a shoulder finish line.
 The outline of the cavity is extend onto smooth and sound
tooth structure
4

5. 26/05/33
 Every effort should be done to conserve the remaining tooth
structure.
 Addition undercut can be done in the cavity walls .
 The cavity depth is detected to determine the type of base
should be used.
TYPE OF PINS:
1. Cemented(Markley)
• Larger than other pin
• Use Zn Ph cem or Zn Polycarboxylate
cement
2. Friction – locked or tapping pins
• Smaller
• Retained by resilience of dentin
• ↑ retentive than cemented pin
With time dentin relax →loose pin
5

6. 26/05/33
3. Self-threading pin
 . Different size
 • Threads engage dentin
 • Depend on elasticity of dentin
 • Most retentive (3-6 times)
 • No corrosion (gold plated)
 • Create horizontal & vertical stress
 • Cause dentinal craze line (size of pin)
MOST CURRENTLY MARKED PINS HAVE:
Metal thread separated
Wider dentinal thread →retained well in dentin
Shoulder stop (to prevent putting stress at the end of pin
channel)
6

7. 26/05/33
TMS PIN (PIN THREAD MATE SYSTEM):
 Regular 0.031 inch diameter
 Minim 0.024 inch diameter
 Minikin 0.019 inch diameter
 Minuta 0.017 inch diameter
TMS PIN (PIN THREAD MATE SYSTEM) available in:
Double shear (two pins in one)
Gold plated,, stainless steel or titanium alloy
Inserted manually or with low-speed latch-type handpiece
7

8. 26/05/33
FACTORS AFFECTING THE RETENTION OF THE PIN IN
DENTIN AND AMALGAM
1-Type of pin:
Self-threading – most retentive
Friction-locked – intermediate
Cemented – least
2-Surface characteristics:
Number & depth of the elevation on the pin (serration or
thread)
self-threading pin – greatest retention
3-Orientation and number
Non-parallel pin - ↑ retention
Bending of pin – not desirable
• Interfere with condensation of amalgam
• Weaker pin, fractured dentin
↑ no. of pin - ↑ retention
• ↑ crazing & fracture
• ↓ amount of dentin available
• ↓ amalgam strength
8

9. 26/05/33
4-↑ diameter of pin →↑ retention
Danger of perforation on pulp or external tooth surface
Interfere with condensation of amalgam and adaptation to pins
5-Extension into dentin and amalgam
Retention is not increase when depth of the pin
↑ 2mm in dentin →fracture of dentin
↑ 2mm in amalgam→fractured amalgam
PIN PLACEMENT FACTORS AND TECHNIQUES
Pin Size
Depend on the amount of dentin available and amount of retention desired.
TMS – pin of choice is:
Minim (0.024 inch)
Minikin (0.019 inch)
Minikin →↓ risk of--- Dentin crazing
Pulpal penetration
Potential perforation
9

10. 26/05/33
Number of Pins
Several factors must be considered:
Amount of tooth structure
Amount of dentin available to receive pin
safely
Amount of retention required
Size of the pin
Number of Pins
As a rule→one pin/missing axial line angle
should be used
Excessive number of pins
→fracture the tooth
→weaken the amalgam restoration
10

11. 26/05/33
Location
Several factors aid in determining pinhole Location:
1. Knowledge of normal pulp anatomy & external tooth contour
2. Current radiograph of the tooth
3.Patient’s age
SOME CONSIDERATIONS:
 Occlusal clearance should be sufficient to provide 2mmof
amalgam over the pin.
 Pinhole should be located halfway between the pulp and DEJ
(0.5-1 mm inside DEJ)
 At least 1 mm of sound dentin around the circumference of
the pinhole.
11

12. 26/05/33
Such location ensures proper stress
distribution of occlusal force
Pinhole:
Should be located in areas where greater stresses occur
Should be located near the line angles of the tooth,
marginal ridges or cusp tip.
Should be parallel to the adjacent external
surface of the tooth (not closer than 1 - 1.5 mm)
Should be prepared on a flat surface
 If three or more pinholes are placed:
Should be located at different vertical levels on the tooth
 Inter-pin distance depend on the size of the pin to be used
For Minim (0.024 inch) →5 mm
For Minikin (0.019 inch)→3mm
 Maximal inter-pin distance results in
lower level of stress in dentin.
12

13. 26/05/33
EXTERNAL PERFORATIION MAY RESULT FROM PIINHOLE
PLACEMENT
 1. Over the prominent mesial concavity of
the maxillary first premolar.
 2. At the midlingual and midfacial bifurcations
of mandiblular first & second molars.
 3. At the midfacial, midmesial,
mid-distal furcations of maxillary first
and second molars..
PULP PENETRATION MAY RESULT FROM PIN PLACEMENT
 At mesiofacial corner of:
Maxillary first molar

13
Mandibular first molar

14. 26/05/33
PINHOLE PREPARATION:
No.¼bur used to prepare a pilot hole
(dimple) →
To permit more accurate placement
of the twist drill
Prevent the drill from crawling once
it has began to rotate
Optimal depth of the pinhole into the
dentin is 2mm
(Omni-Depth gauge used)
PINHOLE PREPARATION:
 The hole should be prepared on flat
surface and the drill perpendicular to it.
 Place flat thin-bladed hand instrument
into the crevice and against the external surface
of the tooth →To indicate the proper
angulations for the drill
14

15. 26/05/33
PINHOLE PREPARATION:
 Place the drill tip in its proper position
 Hand piece rotating at very low speed
 Prepare pinhole in one or two movement
until the depth-limiting portion is reached
 Remove the drill from pinhole
PINHOLE PREPARATION:
 Using more than one or two
 Movements, tilting the hand piece
→
to large pinhole
 The drill should never stop rotating
→
15
to prevent the drill from
breaking in the pinhole

16. 26/05/33
PINHOLE PREPARATION:
 Dull drill →
↑ Frictional heat
Cracks in the dentin
 To bend the pin →TMS bending tool
INTERNAL STRESS CAUSED BY THE PIN
DECREASED BY:
 1. ↑ space between pins
 2. Channel 2mm deep
 3. Pins parallel to occlusal force
16

17. 26/05/33
The success of all amalgam restoration depend on
→ stability of the matrix
Matrix:
Tofflemire
Double matrix
Copper
Auto matrix
FAILURE OF PIN--RETAINED RESTORATION
Occur at any of five different location:
 a. Restoration fracture (failure within rest)
 b. Pin restoration separation (at the interface
between the pin and restorative material)
 c. Pin fracture (within the pin)
 d. Pin dentin separation (at the interface
between the pin and dentin)
 e. Dentin fracture (within the dentin)
Failure is more likely to occur at the
pin dentin interface
17

18. 26/05/33
PROBLEMS THAT ARISE DURING PINRETAINED
RESTORATION:
 1. Broken drills and pins
Twist drill will break if:
Stressed laterally
Allowed to stop rotating before removing from the pinhole
Dull drill (can be used till 20 holes)
Pin will break:
During pending
Over - screwed in the hole
Solution: Leave it in place.
Do another hole 1.5mm away from broken item
2. Loose pins • Due to:
Loosened while shortened with bur
Pinhole prepared too large
Solution:
• Remove pin , pinhole prepared with next largest
size drill , appropriate pin inserted
• Drill another hole 1.5mm from original pinhole, close the
other one with amalgapins or cement the pin
18

19. 26/05/33
3-Penetration into the pulp and perforation of the
external tooth surface:
• Either penetration is obvious if there is hemorrhage in the
pinhole
• Radiograph can help sometimes.
• solution:
Pulpal penetration treated as a pinpoint exposure
→Ca OH and prepare another hole
• If patient complains of pain after that →endodontic treatment
4-Latteral Perforation:
Solution:
Occlusal to gingival attachment
Pin cut-off flush with the tooth surface.
Pin cut-off and cast restoration extend gingivaly.
Remove pin , enlarge hole and restored with amalgam.
19

20. 26/05/33
Apical to gingival attachment:
Solution:
Surgically remove the bone after reflecting the tissue, enlarge
pinhole, restored with amalgam
Crown lengthening and cast restoration cover the
perforation.
20