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PIN RETAINED

RESTORATIONS


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CONTENTS

1. Introduction2. Definition

3. Indications and contraindications

4. Advantages and disadvantages5. Pinstypes and designs

6. Pin placementfactors

7. Techniques for inserting pins8. Cavity preparations

9. Complications and failures


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INTRODUCTION

Most of the teeth can be restored withamalgam and composite but when the

tooth preparation is extensive due to

caries or other reason the remaining toothstructure is very less, it becomes difficult

to achieve optimal resistance and

retention form. In such cases dentin lock and slots are

prepared in dentin


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But when these retention features areinsufficient to provide desired retention

then pin supported restorations are

used In these cases pins support the

restorative materials and resist their

dislodgment in severely damagedtooth


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HISTORY

In 1958, Dr. Miles Markley introduced apractical instrumentation for the use of

a stainless steel cemented pin that

resulted in the extensive use ofcemented pins in dentistry


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DEFINITION

Pin retained restoration is defined asany restoration which requires the

placement of pin/pins in dentin in

order to provide retention and/orresistance form to the restoration


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INDICATIONS

Extensive tooth loss

Questionable prognosis

As a foundation

Economics

Age and health of the patient


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CONTRAINDICATIONS

Occlusal problems

Esthetics

Access difficulties


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ADVANTAGES

Conservation of tooth structure

Appointment time

Resistance and retention form

Economics


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DISADVANTAGES

Dentinal micro fractures

Lowered fractured resistance

Strength of amalgam restoration is

reduced

Micro leakage

Perforations

Difficulty to achieve proper contours


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TYPES OF PINS

1. Cemented pins

2. Friction locked pins

3. Self threaded pins


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CEMENTED PINS

Developed by Dr.Markley to retainlarge amalgamrestorations

Made of StainlessSteel

They are used tobuild foundation after

endodontictreatment as theyproduce the leastamount of stress

Offer less resistancethan the other pins


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FRICTION LOCKED PINS

Developed by Dr.Goldstein in 1966

Made of stainlesssteel

More retentive thancemented pins

Used in vital teethwith good access

and ease of tappingthe pins

Cause craze lines orcracks


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SELF THREADED PINS

Developed by Dr.Going in 1966

Most popular typeamong all thedifferent type of pinsand extensively used

Made of stainlesssteel or titanium pins

Provide maximum

retention among alltypes of pins

Cause craze lines

Used in vital teeth

CEMENTED PINS FRICTION OCKED PINS SE F THREADED PINS


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CEMENTED PINS FRICTION LOCKED PINS SELF THREADED PINS

Stainless steel with

threads or serrations

Stainless steel with

threads

Stainless

steel/Titanium withgold plating

Pin channel [0.020

to 0.32] largerthan

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 contraangle hand piece

Ease of placement Pin placement is

difficult

Pin placement is

easy



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Less internalstresses

Increased internalstress

Increased internalstresses

Least retentive 2-3 times more

retentive than

cemented pins

5-6 times more

retentive than friction

locked pins


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SELF THREADED PINS

THREAD MATE SYSTEM


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SELF THREADED PINS

THREAD MATE SYSTEM

REGULAR MINIM MINIKIN MINUTA


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REGULAR MINIM MINIKIN MINUTA

Largest

diameter pins

Causes

maximal

stressCauses

maximum

dentinal

crazingRarely used

Next smaller

diameter pins

Lesser stress

are created

Lesserdentinal

crazing

Good

retention

Diameter is

lesser than

minim pins

Very less risk

of dentinalcrazing

Good

retention

MINIM ANDMINIKIN ARE

COMMONLY

USED SIZES

OF TMS

SYSTEM

SMALLEST

SIZE of pins

They are too

small to

provideadequate

retention

Not widely

used


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PIN DESIGNS

Standard 7mm long


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Standard

design

7mm long

They have flattened heads to fit into the hand wrench or

handpiece chuck

After placement the pin is reversed 1/4thturn to reduce

stresses on dentin

Pin height can be adjusted appropriately

Self

shearing

design

Avaliable in varying lengths


handpiece chuck

During pin placement when the pin reaches the bottom of the pinhole, 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


handpiece chuck

The handpiece need not be reloaded during insertion of more

than 1 pin

Link series They have a plastic sleeve that fits into the latch type


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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

Self shearing

Avaliable 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 stresseswhile seating


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ADVANTAGES OF TMS PINS

Versatile design

Wide range of

pin sizes

Color codingallows ease of

use

Gold plating

eliminates

corrosion

Good retention


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PIN PLACEMENT

1. MECHANICAL ASPECTS

2. ANATOMICAL ASPECTS

3. MECHANOANATOMICAL

ASPECTS


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MECHANICAL

ASPECTS

[PINS AND TOOTH

STRUCTURE]

A] Stressing capabilitiesof pins

Type of pins


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Diameter of pins

Pin depth and

dentinalengagement

Bulk of dentin

Type of dentin


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Shape of pin

channels

Loose pins

Irregularly shaped

dentinal end of pins

Ratio of dentinalengagement : pin

protrusion [ideal

2:1]

Number of pins inone tooth


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Drillits use and function

Stresses induced during shortening

pins

Retentive features

Inserting pins in stress concentration

area of tooth


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B] RETENTION OFPINS IN DENTIN

Type of pin

Pin depth anddentinal engagement

Pin channelcircumferentialshape relative to that

of pin Inter pin distance


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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


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C] MICROCRACKING AND CRAZING

Type of pin

Proximity of pin to DEJ

Induced stresses in involved dentin

Type of dentin


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MECHANICAL ASPECTS

[PINS AND RESTORATIVE

MATERIALS]

A] Effect of pins on the strength of

amalgam and composite restorations

Compressive strength

Tensile strength


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B] RETENTION OF PINS TORESTORATIVE MATERIALS

Type of pin Pin diameter

Inter pin distance

Pin length in restorative material

Proximity of restorative material with thepin surface

Surface material of pins


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ANATOMICAL ASPECTS

Knowledge of

anatomy

Radiograph Outer surface of

tooth

Amount of dentin


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Anatomical features

Tooth alignment

Cavity extent

Effect of age or relative age on the

pulp chamber


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MECHANO ANATOMICAL

ASPECTS FOR PIN PLACEMENT


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TECHNIQUES FOR INSERTING

PINS

Pin channel preparations

Cemented pin technique

Threaded pin technique

Friction grip pin technique


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PIN CHANNEL PREPARATION

Twist drill

No. 1,2,3 round burs

Measuring probes or depth guage


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CEMENTED PIN TECHNIQUE

INDICATIONS

Ideal technique Only technique for endodontically

treated tooth

Only technique to be used whenavaliable location of the pin is close to

DEJ


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Ideal technique for a sclerotized /tertiary / calcific barrier / highly

demineralized / dehydrated dentin

For class IV restorations When there is limited bulk of dentin


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PROCEDURE Preparation of pin channel

Checking the surface irregularities of

pins Slow setting phosphate /

polycarboxylate introduced by perio

explorer tip or lenticulo spiral at slowspeed

Placement of pin using lock in or

magnetised tweezer or hemostat


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Large amalgam plugger is needed tocheck the complete seating of the pin

In case of class IV restorations,

bending of the pins is to be donebefore cementation of the pin channel

C Q


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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 therestoration


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PROCEDURE

Preparation of pin channel

Pin is engaged to a driving device andpin is continuously threaded into the pinchannel until it offer resistance initiatedby the pin channel floor

Desired length of the pin can be cutusing small bur and high speedhandpiece in the direction of threading

and with light intermittent touches Surface irregularities are corrected

No bending should be performed

FRICTION GRIP PIN TECHNIQUE


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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


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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 pinchannel using a measuring probe

Pin is held in its place at the entrance

of the cavity Concave headed seater is placed on

the pin


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With the hammer light strokes aregiven until that colored mark

Remove all the holding devices

Check for cracks, chipped pieces orgrossed fractures


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CAVITY PREPARATION

Remove all carious and weakenedtooth structure

Initial cavity is prepared with

dovetails, boxes, grooves etc Facial and lingual walls are kept

parallel wherever possible

Margins are placed supragingivally


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Areas to receive pins should be flatand perpendicular to long axis of the

tooth.

There must be enough dentin for pinplacement

Weakened cusps should be reduced

and occlusal contour should follow thenormal contour of the unreduced tooth

PULP PROTECTION


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CLASS II DESIGN

Pins should be put in apically deepestand 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


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CLASS III AND CLASS IV


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CLASS III AND CLASS IV

DESIGN

CLASS III

Pronounced

gingival floor in 2

dimensions mustbe made

One pin per

gingival floor is

sufficient


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CLASS IV

For unilateral

class IV, L

shaped cementedpin is sufficient

For bilateral class

IV, U shaped

cemented pin isused


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CLASS V DESIGN

Pins are placed axiallyparallel to the adjacentproximal surface

Pin protrusion shouldbe minimal

Deep retentive groovesare placed

Pins should be placedmidway in thepreparation but asclose to gingival wall aspossible

RESTORATIO


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RESTORATION


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COMPLICATIONS

Drill breakage Pin breakage

Loose pins

Heat generation

Dentinal cracks

Perforation into pulpal space or

external tooth surface


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FAILURES


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EFFECT OF PINS ON PULP

Generally it responds positively andaccepts its presence without any

adverse effects

Histologic evaluation revealsinflammatory response, necrotic tissue

encapsulation, fibrous tissue

regeneration and formation of predentin by odontoblasts

Inflammatory reactions have been

observed under all kinds of pins


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CONCLUSION

The prognosis of the involved toothand 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 retentionof the restoration

Pins have been extensively used in

the past to restore such badly broken


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REFERENCES

1. Principles and practices of OperativeDentistryGerald T Charbeneau

2. Text book of Operative DentistryNisha

Garg

3. Text book of Operative DentistryVimal K

Sikri

4. Operative DentistryModern theory and

practiceM A Marzouk

5. Sturdevents Art and Science of Operative

Dentistry

6. Clinical Operative Dentistry Principles and


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THANK

YOU

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