Transcript PIN RETAINED RESTORATIONS - King George's Medical University

Dr Rakesh Kumar Yadav
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.
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
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
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.
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
CONTRAINDICATIONS
 Occlusal problems
 Esthetics-Rarelly used in anterior teeth(Bonding
Technique).
 Access difficulties-In class V horizontal groove in the
gingival & occlusal aspect etc.
ADVANTAGES
 Conservation of tooth structure
 save time compared with cast restoration.
 Greater resistance and retention form
 Economics
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
TYPES OF PINS
1. Cemented pins
2. Friction locked pins
3. Self threaded pins
FRICTION LOCKED PINS
 Developed by Dr. Goldstein in
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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
SELF THREADED PINS
 Developed by Dr. Going in
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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
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 Placed by hand
mallet
wrench or contra
angle hand piece
Ease of placement
Pin placement is
difficult
Pin placement is easy
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
SELF THREADED PINS – THREAD
MATE SYSTEM
SELF THREADED PINS – THREAD
MATE SYSTEM
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
•Good retention
•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
PIN DESIGNS
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
•They have flattened heads to fit into the hand wrench or handpiece
chuck
•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
•They have flattened heads to fit into the hand wrench or handpiece
chuck
•The handpiece need not be reloaded during insertion of more than
1 pin
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
•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
ADVANTAGES OF TMS PINS
 Versatile design
 Wide range of pin sizes
 Color coding allows ease
of use
 Gold plating eliminates
corrosion
 Good retention
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
PIN PLACEMENT
MECHANICAL ASPECTS
2. ANATOMICAL ASPECTS
3. MECHANO – ANATOMICAL ASPECTS
1.
MECHANICAL ASPECTS
 A] STRESSING CAPABILITIES OF PINS
 B] RETENTION OF PINS IN DENTIN
 C] MICROCRACKING AND CRAZING
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
 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
 Drill – its use and function
 Stresses induced during shortening pins
 Retentive features
 Inserting pins in stress concentration area of tooth
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
 Type of cement
 Ratio of dentinal engagement : pin protrusion [ideal
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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
C] MICROCRACKING AND CRAZING
 Type of pin
 Proximity of pin to DEJ
 Induced stresses in involved dentin
 Type of dentin
ANATOMICAL ASPECTS
 Knowledge of anatomy
 Radiograph
 Outer surface of tooth
 Amount of dentin
MECHANO ANATOMICAL
ASPECTS FOR PIN PLACEMENT
 Anatomical features
 Tooth alignment
 Cavity extent
 Effect of age or relative age on the pulp chamber
TECHNIQUES FOR INSERTING PINS
 Pin channel preparations
 Cemented pin technique
 Threaded pin technique
 Friction grip pin technique
PIN CHANNEL PREPARATION
 Twist drill-By using twist drill latch type or depth
limiting drill at low speed ( 300-500) 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
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
 Ideal technique for a sclerotized / tertiary / calcific
barrier / highly demineralized / dehydrated dentin
 For class IV restorations
 When there is limited bulk of dentin
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
 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
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
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
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
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
 With the hammer light strokes are given until that
colored mark
 Remove all the holding devices
 Check for cracks, chipped pieces or grossed fractures
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
 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
CLASS II DESIGN
 Pins should be put in apically deepest and most
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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
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
RESTORATION
COMPLICATIONS
 Drill breakage
 Pin breakage
 Loose pins
 Heat generation
 Dentinal cracks
 Perforation into pulpal space or external tooth surface
FAILURES
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
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