pin retained restorations

1. PIN RETAINED
RESTORATIONS
Small wire fit into a
channel drilled in
the dentin, away
from the pulp space.
Also called Dentinal
or Parapulpal pins.

2. History
 1958- Markley cemented serrated
wire in a pin-hole .001-.002” larger
than diameter of pin.
 1966- Goldstein tapped a friction
lock pin in a hole .001” smaller in
diameter.
 1966- Going used a self threaded
pin in hole .001-.004 smaller in dia.

3. Advantages
 Conservation of tooth structure
 Less appointment time
 Significant increase in retention
 Economic

4. Disadvantages
 Dentinal micro fracture.
 Micro leakage.
 Decreased strength of filling.
 Resistance form difficult to develop.
 Perforations.
 Tooth anatomy.

5. Indications &
Contraindications
 Resistance & Retention form.
 Status & Prognosis of the tooth.
 Role of tooth in treatment plan.
 Occlusion, esthetics & economics.
 Age & health of the patient.
 Core for cast restorations.
 Crosslinkage of two parts of
remaining tooth structure.

6. Procedure
 Patient education
 Cavity preparation
 Determination of pin size
 Determination of number of pins
 Determination of location of pinholes

7. Armamentarium
Basic instruments
• Twist drill
A. Standard drill
B. Depth limiting drill
• Round burs to prepare pilot hole
• Depth gauge

10. Use of twist drill
 Ultra low speed (300-500 rpm).
 Forces should be applied parallel to
the long axis of the drill.
 Drill should be continuously rotating,
from entry till withdrawal from
channel.
 Pinhole should be prepared to the
required depth in one stroke.
 Never use the drill in enamel.

11. Anatomical Considerations
 Knowledge of Anatomy.
 Radiographs.
 External surface of tooth.
 Amount of dentin available.
 Tooth alignment.
 Extent of cavity.
 Age of patient.

12. Pinhole Diameter
 Cemented – Larger than pin
 Friction lock - smaller
 Self thread - smaller

13. Thread mate system (TMS)
4 Sizes Drill dia. Pin dia.
colour coded
Regular 0.027” 0.031”
Minimum 0.021” 0.024”
Minikin 0.017” 0.019”
Minuta 0.013” 0.015”

15.  Pin too close to
the vertical wall,
condensation of
amalgam
jeopardized.

16.  Cove preparation allows sufficient
space for condensation of amalgam.

17.  Use of depth limiting drill to prepare
pinhole on a surface that is not
perpendicular to the direction of the
pinhole will result in a pinhole of
inadequate depth

19. Pinholes on posterior teeth
Avoid.
 Mid-mesial surface of max. first
premolar due to prominent mesial
concavity.
 Mesio-facial corner of all first molars
because of prominent mesio-facial
pulp horn.
 Mid-lingual and mid facial surfaces
of mandibular first & second molars,
due to furcation areas.

20. Designs
Standard.
 7mm, flattened head.
 Hand wrench for tactile sense.
 Advantage: Reverse 14 -12 turn
for decreased apical stress.

21. Designs
Self shearing
 Total length according to the
diameter of the pin.
 Flattened head
 Advantage: Shears when it reaches
bottom.

22. Designs
Two in one
 Shorter than standard pin.
 Flattened end.
 Shears exactly half extending into
dentin and the other half in hand
wrench can be used for another pin
hole.

23. Designs
Link series
 Color coded plastic sleeve.
 Latch type for contra angle
handpiece.
 Special design hand wrench.
 Self shearing.
 Self aligning ability.
 Less apical stress.
 Titanium or St. steel plated in Gold.

24. Designs
Link plus
Variations of the Link series:
 Single or two in one.
 Sharper threads.
 Shoulder stop at 2mm.
 Tapered tip.
 Extension out of dentin 2.7mm

26. Retention
 Cemented – depending on cement
used; less retentive
 Friction lock – depending on dentin
resiliency; 2-3 times more retentive
than cemented
 Self thread – threads and resiliency
of dentine; 3-6 times more retentive
than cemented.

27. Micro leakage
Varnish application advised.
 Cemented – Increased chances.
 Friction lock – Chances of voids &
incomplete seal.
 Self thread – with cement & threads,
least chances.

28. Stress
 Cemented – Least.
 Friction lock – More; apical stress
due to tapping.
 Self thread – More; lateral & apical
stress generated.

29. Depth in Dentin
 Cemented – 3-4mm.
 Friction lock – 2-4mm.
 Self thread – 1.5-2mm.

31. Stress
Related to
1. Type of pin.
2. Diameter of pin.
3. Pin depth and dentinal engagement
4. Bulk of dentin.
5. Type of dentin.
6. Inter pin distance.
7. Number of pins in one tooth.

32. Stress
8. Non-coinciding (eccentricity) of pin
& pinhole circumference.
9. Loose pin.
10. Wedge, chisel or irregularly
shaped dentinal end of pin.

33. Retention in Dentin
Related to
1. Type of pin.
2. Depth of pin in dentin.
3. Number of pins.
4. Type of cement.
5. Type of dentin.

34. Retention in Dentin
7. Surface roughness of pin.
8. Ratio of the pin length in dentin to
the length in the cavity.
9. Mode of shortening of pin after
insertion.
10.Bulk of dentin.

35. Micro cracking & Crazing
Due to
1. Type of pin.
2. Proximity of pin to the DEJ.
3. Induced stresses in dentin.
4. Thickness of adjacent enamel.
5. Type of dentin.

36. Strength of Restoration
Compressive & tensile strength
reduced because of
1. Wedge or chisel shaped pin end in
the cavity.
2. Inter pin distance less than 2mm.
3. Pins approximating the surface of
the restoration (less than 1.5mm).
4. Non adaptability of restoration to
pin.

37. Retention to restoration
Related to
1. Type of pin.
2. Pin length in restorative material.
3. Diameter of pin.
4. Inter pin distance.
5. Adaptability of restoration to pin.
6. Surface roughness of pin.

38. Advantages
 Cemented – Ideal for RC treated
tooth; least stress.
 Friction lock – More retention than
cemented.
 Self thread – Versatile, colour
coded, wide range of sizes, more
retentive, noble plating.

39. Disadvantages
 Cemented– Cement-pin-dentin
interface weak (micro leakage,
loosening); least retention;
increased time for handling cement .
 Friction lock– Difficult in posterior
teeth, patient apprehension; less
retention than threaded pins.
 Self thread – Stress; more stress
and lateral stripping of channel while
cutting and bending.

40. Indications- Cemented
 For all pin retained restorations
 The only technique to be used for
endodontically treated teeth.
 The only technique to be used
when the available location for the
pin is very close to the DEJ.
 The only technique to be used for
‘U’ & ‘L’ shaped pins in class IV
restorations.

41. Indications- Cemented
 It is used when the bulk of dentin
to accommodation a pin is limited.
 It is an ideal technique for
sclerosed tertiary, calcific barrier or
dehydrated dentin.
 It is the only technique for cross
linkage of two parts of the same
tooth.

42. Indications- Friction lock
Least used
 Only in vital teeth.
 Bulky dentin should be available
(at least 4mm in 3 directions).
 Pin should be at least 2.5mm from
DEJ.
 Can be used only in accessible
areas of the mouth so that the
seating force is parallel to pin axis.

43. Indications- Threaded
 It is used for vital teeth.
 Dentin around the pin hole should
be properly hydrated.
 Available pin location shd be at
least 1.5mm from D-E-J.
 Minimal number of pins are
required.
 Maximum retention of pin to dentin
and restoration is required.

44. Complications
 Loose pins .
 Broken drills and pins.
 Penetration into pulp .
 Perforation on to the external tooth
surface.

45. Biologic considerations
Irritation to P-D organ by pins.
Factors are:
1) Cracks
2) Vibration
3) Cement
4) Stress concentration
5) Conductivity
6) Irritations from material

46. Failures
A. Fracture of
restoration.
B. Separation of
material from pin.
C. Fracture of pin.
D. Separation of
dentin from pin.
E. Fracture of dentine.

47. Indirect Pins
 Pinhole made.
 Impression taken with or without
pin.
 Casting with pin.
 Precious alloys, Titanium & Cr-Co
alloys give best strength & corrosion
resistance. Stainless Steel and brass
also used.

48. Alternatives
For enhanced retention we can also
use
 Slots
 Locks
 Coves & Grooves
 Amalgapin
 Bonding agents
 Cast restorations.