1. PIN RETAINED RESTORATIONS
Dr Rakesh Kumar Yadav

2. INTRODUCTION
Most of the teeth can be restored with amalgam and composite but if large crown portion lost due to caries or some other reasons, the remaining tooth structure is decrease and difficult to obtained resistance and retention form so prepare dentine lock and slot but when these retention features are insufficient to provide desired retention then pin supported restorations are used.

3. TRETMENT OF BADLY BROKEN TOOTH
First-Evaluate biologically and mechanically
Status of pulp and periodontium should be evaluated.
Involvement of pulp or not
Restorative design planning
if pulp is not involve-pin,inlay,onlay
Pulp involvement- pulpotomy ,pulpectomy, pin,full coverage-
Tooth anterior or posterior

4. HISTORY
In 1958, Dr. Miles Markley introduced a practical instrumentation for the use of a stainless steel cemented pin that resulted in the extensive use of cemented pins in dentistry

5. DEFINITION
Defined as any restoration which requires the placement of one or more pins in dentin to provide to adequate resistance and retention form to the restoration. It has a greater retention than those using boxes or bonding system.

6. INDICATIONS Badly broken down or mutilated teeth.
Questionable prognosis-Controlled restoration in tooth with questionable pulp or periodontal prognosis
As a foundation under fixed restoration(core)
Economics
Age and health of the patient

7. CONTRAINDICATIONS Occlusal problems
Esthetics-Rarelly used in anterior teeth(Bonding Technique).
Access difficulties-In class V horizontal groove in the gingival & occlusal aspect etc.

8. ADVANTAGES Conservation of tooth structure
save time compared with cast restoration.
Greater resistance and retention form
Economics

9. DISADVANTAGES Dentinal micro fractures or crazing
Lowered fractured resistance
Strength of amalgam restoration is reduced
Micro leakage around pin
Perforations of pulp or ext. tooth structure.
Difficulty to achieve proper contours

10. TYPES OF PINS
Cemented pins
Friction locked pins
Self threaded pins

12. 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/locked the pins
Cause craze lines or cracks
Retain by resilience of dentin

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

14. Stainless steel with threads or serrations
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

15. Less internal stresses Increased internal stress
CEMENTED PINS
FRICTION LOCKED PINS
SELF THREADED PINS
Less internal stresses
Increased internal stress
Increased internal stresses
Least retentive
2-3 times more retentive than cemented pins
5-6 times more retentive than friction locked pins

16. SELF THREADED PINS – THREAD MATE SYSTEM

17. SELF THREADED PINS – THREAD MATE SYSTEM

18. Causes maximum dentinal crazing
REGULAR
MINIM
MINIKIN
MINUTA
Largest diameter pins
Causes maximal stress
Causes maximum dentinal crazing
Rarely used
Next smaller diameter pins
Lesser stress are created
Lesser dentinal crazing
Good retention
Diameter is lesser than minim pins
Very less risk of dentinal crazing
MINIM AND MINIKIN ARE COMMONLY USED SIZES OF TMS SYSTEM
SMALLEST SIZE of pins
They are too small to provide adequate retention
Not widely used

19. PIN DESIGNS

20. Standard design
7mm long
They have flattened heads to fit into the hand wrench or handpiece chuck
After placement the pin is reversed 1/4th turn to reduce stresses on dentin
Pin height can be adjusted appropriately
Self shearing design
Available in varying lengths
During pin placement when the pin reaches the bottom of the pin hole, the head automatically shears off, leaving a portion projecting from dentin
Two in one design
It consists of 2 pins connected by means of a joint which serves as a shear line for peripheral pin
Total length is 9mm and 2 pins are about 4mm each
The handpiece need not be reloaded during insertion of more than 1 pin

21. Link series design
They have a plastic sleeve that fits into the latch type contra angle handpiece or a special plastic hand wrench
Self shearing
Pin engages the dentin and the plastic sleeve can be discarded
Can align well into pin channels
Link plus design
Similar to link series design
Available as single or 2 in 1 pins
The major difference in this pin design is that pins have sharper threads and a tapered tip to decrease dentinal stresses while seating

22. ADVANTAGES OF TMS PINS Versatile design Wide range of pin sizes
Color coding allows ease
of use
Gold plating eliminates
corrosion
Good retention

23. FACTORS AFFECTING THE RETENTION OF THE PIN IN DENTIN AND AMALGAM
Orientation, number and diameter
-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

25. PIN PLACEMENT MECHANICAL ASPECTS ANATOMICAL ASPECTS
MECHANO – ANATOMICAL ASPECTS

26. MECHANICAL ASPECTS A] STRESSING CAPABILITIES OF PINS
B] RETENTION OF PINS IN DENTIN
C] MICROCRACKING AND CRAZING

27. MECHANICAL ASPECTS [PINS AND TOOTH STRUCTURE]
A] Stressing capabilities of pins
Type of pins
Diameter of pins
Pin depth and dentinal engagement
Bulk of dentin
Type of dentin

28. Shape of pin channels
Loose pins
Irregularly shaped dentinal end of pins
Ratio of dentinal engagement : pin protrusion [ideal 2:1]
Number of pins in one tooth

29. Drill – its use and function
Stresses induced during shortening pins
Retentive features
Inserting pins in stress concentration area of tooth

30. B] RETENTION OF PINS IN DENTIN
Type of pin
Pin depth and dentinal engagement
Pin channel circumferential shape relative to that of pin
Inter pin distance

31. Type of cement
Ratio of dentinal engagement : pin protrusion [ideal 2:1]
Type of involved dentin
Surface roughness of the pins
Mode of shortening of pins after insertion of pins
Bulk of dentin around the pin

32. C] MICROCRACKING AND CRAZING
Type of pin
Proximity of pin to DEJ
Induced stresses in involved dentin
Type of dentin

33. ANATOMICAL ASPECTS Knowledge of anatomy Radiograph
Outer surface of tooth
Amount of dentin

34. MECHANO ANATOMICAL ASPECTS FOR PIN PLACEMENT
Anatomical features
Tooth alignment
Cavity extent
Effect of age or relative age on the pulp chamber

38. TECHNIQUES FOR INSERTING PINS
Pin channel preparations
Cemented pin technique
Threaded pin technique
Friction grip pin technique

39. PIN CHANNEL PREPARATION
Twist drill-By using twist drill latch type or depth limiting drill at low speed ( ) RPM
No. 1/4 round burs- first make pilote hole with round bur to localize position of the pin the complete the hole in one or two thrust( movement)
Apply intermittent pressure

40. CEMENTED PIN TECHNIQUE
INDICATIONS
Ideal technique
Only technique for endodontically treated tooth
Only technique to be used when avaliable location of the pin is close to DEJ

41. Ideal technique for a sclerotized / tertiary / calcific barrier / highly demineralized / dehydrated dentin
For class IV restorations
When there is limited bulk of dentin

42. PROCEDURE
Preparation of pin channel
Checking the surface irregularities of pins
Slow setting phosphate / polycarboxylate introduced by perio explorer tip or lenticulo spiral at slow speed
Placement of pin using lock in or magnetised tweezer or hemostat

43. Large amalgam plugger is needed to check the complete seating of the pin
In case of class IV restorations, bending of the pins is to be done before cementation of the pin channel

44. THREADED PIN TECHNIQUE
INDICATIONS
Vital teeth
Dentin to engage the pin is either primary or secondary
Minimum avaliable location is 1.5mm from DEJ
If minimum pins are needed for the restoration

45. PROCEDURE
Preparation of pin channel
Pin is engaged to a driving device and pin is continuously threaded into the pin channel until it offer resistance initiated by the pin channel floor
Desired length of the pin can be cut using small bur and high speed handpiece in the direction of threading and with light intermittent touches
Surface irregularities are corrected
No bending should be performed

46. FRICTION GRIP PIN TECHNIQUE
INDICATIONS
For vital teeth
When bulk of dentin is present [min 4mm in all 3 dimensions]
Only in the accessible areas

47. PROCEDURE
Pin channel is prepared
Checking the surface irregularities of pins
Put a colored mark on the pin to indicate the exact depth of the pin channel using a measuring probe
Pin is held in its place at the entrance of the cavity
Concave headed seater is placed on the pin

48. With the hammer light strokes are given until that colored mark
Remove all the holding devices
Check for cracks, chipped pieces or grossed fractures

49. CAVITY PREPARATION Remove all carious and weakened tooth structure
Initial cavity is prepared with dovetails, boxes, grooves etc
Facial and lingual walls are kept parallel wherever possible
Margins are placed supra-gingivally

50. Areas to receive pins should be flat and perpendicular to long axis of the tooth.
There must be enough dentin for pin placement
Weakened cusps should be reduced and occlusal contour should follow the normal contour of the unreduced tooth
PULP PROTECTION

51. CLASS II DESIGN
Pins should be put in apically deepest and most peripheral parts of the cavity
Pin should not be placed below the cusp
Decreasing the stress concentration on the pin
Use of minimum number of pins with less diameter
Placement of the pin should be such that theres enough restorative material around it

53. CLASS V DESIGN
Pins are placed axially parallel to the adjacent proximal surface
Pin protrusion should be minimal
Deep retentive grooves are placed
Pins should be placed midway in the preparation but as close to gingival wall as possible

54. RESTORATION

55. COMPLICATIONS Drill breakage Pin breakage Loose pins Heat generation
Dentinal cracks
Perforation into pulpal space or external tooth surface

57. FAILURES

58. EFFECT OF PINS ON PULP
Generally it responds positively and accepts its presence without any adverse effects
Histologic evaluation reveals inflammatory response, necrotic tissue encapsulation, fibrous tissue regeneration and formation of pre dentin by odontoblasts
Inflammatory reactions have been observed under all kinds of pins

59. CONCLUSION
The prognosis of the involved tooth and its role in overall treatment plan helps to decide the restoration to be placed
If amalgam is selected as the restorative material to be placed, pins placed in dentin improve the retention of the restoration
Pins have been extensively used in the past to restore such badly broken tooth