Pin Retained Restoration

Pin Retained Restoration

Definition: One or more pins may be required to

supplement inadequate retention in a cavity for retention.

> Extension of cavity into holes or channels

> Channels are placed in dentine , pins are placed in channel.

Hence called dentine's pins

Pin Retained Restorations

Retentive Features of a Cavity Two Types: 1. Primary or Principal means 2. Auxiliary means

1. primary or Principal means: i. Friction : a. Opposing walls b. Parallel walls c. Surface area of opposing walls d. Proximity of restorative materials to wallsii. Dove-tail :iii. Undercuts or inverted cones :iv. Elastic deformation of dentine

Retentive Features of a Cavity

2. Auxiliary means : i. Grooves ii. Internal boxes iii. Etching of enamel iv. Pins v. Posts etc.

IndicationsIndications 1. Mutilated / badly brocken down tooth : > For rubber dam application > For or the -bands-attachment > For restoration of tooth2. Foundation : > For crowns > To conserve tooth-structure 3. Questionable prognosis : > Endodontically > Periododontically4. Cross linkage mode : To connect two bulky parts abnormal tooth removal5. Adjunct retention mode : To resist post rotation6. Economical :Than crowns7. Auxiliary / reciprocal retentive mode for a restoration.

Indication of pinIndication of pini. Grossly carious

teeth

2. Foundation :

> For crowns

> To conserve tooth-structure

Indications of pinIndications of pin

Indications of pinIndications of pin3. Questionable prognosis :

> Endodontically

>

Periododontically


v. Adjunct retentive mode : The presence of pins in case of post retained restoration , help in prevention of rotation of restoration


4. Cross linkage mode :

To connect two bulky parts

-abnormal tooth removal.

6. Economical :

Than crowns

Indications of Indications of pinpin

Advantages of pins

i. Conserve cutting of tooth : offer retention without the need for extensive preparation of tooth structureii. Resistance : may increase resistance form of the preparation to some extent e.g. in case of cross-linkageiii. Less time consuming : need single visitiv. Less expensive : than cast-restorations

Disadvantage of pins

Do not increase the strength of restorative materials Even decrease the strength of restorative materialsi.Induce stresses in dentine may be cause : a. cracks / crazes in tooth b. micro-leakage c. pulpal damage External or pulpal perforation Chance of micro leakage around the pins dentine interface

Pin Retained Restoration

Types of pins:

Four kinds of pin systems are currently available :

1. Cemented pins

2. Friction-locked pins

3. Self-threading pins

4. Cyanoacrylate pins

1. Cemented pins :

Sizes of pins:

a. 0.020''

b. 0.025''

Cemented pin

2. Friction grip / friction lock pins :

Sizes of pin : 0.0021'' or 0.022''

3. Threaded pins:- >Thread made system >Stabilock system Sizes of pins: a. Regular ( 0.031” ) b. Minim ( 0.024” ) c. Minikin ( 0.019” ) d. Minuta ( 0.015” )

Compare sizes of the channels with that of different pins :

Type of pins Pin channel diameter Pin diameter

1. Cemented pins 0.027 “ 0.025 “

0.021 “ 0.020 “

2. Friction grip pins 0.021 " 0.022 "

3. Threaded pins 0.027 “ 0.031 "

0.022 “ 0.024 "

0.017 " 0.019 “

0.013 “ 0.015 “

Pin channel

Compare sizes of the channels with that of different pins :

Successful Pin PlacementThis depends upon following factors :

1. Stresses induced by pins insertion in the dentine

2. Retention of pin in the dentine

3. Effect of pins on restorative materials.

4. Knowledge of tooth anatomy ( External )( Internal )

5. Knowledge of radiographic findings.

6. Proper techniques of placement of pins in dentin in cavity.

Stresses induced by pins in dentin

Factors related to dentine :1. types of dentine : - elasticity of dentin stress tolerance - Decreasing order of tolerance Primary dentin > secondary dent > sclerosed dentine > tertiary dentin > caleific barrier2. bulk of dentin stress toleranceFactors related to pins :Types of pins : diameter surface texture techniqueOther factors : Inter pin distance loose pins pin depth wedge end of pinNo of pin pin handling dentinal depth : protrusi Avoid stress ideal 1:1 bearing areas acceptable 2:1 Using drill correctly

Stresses induced by pins in dentin

Stresses denoted by ~~

stresses (denoted by ~~) induced by friction grip pin in dentin are greater than threaded pins / cement pins stresses by threaded pins > that of cemented pins.

Retention of pins in dentine :

Factors related to dentine ; 1. Types of dentine : - elasticity of dentine retention 2. Bulk of dentin RetentionFactors related to pins : 1. Types of pins : Diameter Surface texture Technique 2. Other factors : pin channel no of pins circumference < ( cutting )( bending )( orientation ) pin depth pin handling inter pin dentinod depth : protrusion distance ideal 2:1 acceptable 1:1Type of cement : decreasing order of retention copper phosphate cement > z p c > p.c.c > Z no E

Pins and restorative material See the effect : strength wise retention wise Pins increase retention of rest material Pins decrease strength of rest material

Following factors retention: Pins factors : i. Types of pins : a. diameter b. surface texture ii. Other factors : a. orientation b. pin length on restorative material c. interpin distance d. no. of pins iii. Proximity of restorative material to pins

Stresses and pins in restorative material : i. Chiesel / wedge end of pin in restorative material ii. Inter pin distances iii. Bulk of restorative material over the cavity end of pin iv. Adaptability of rest material around the pin

Knowledge of tooth anatomy

a. pulp chamber b. tooth morphology [surface contours] c. tooth alignment d. cavity extentsion e. age of patient

Knowledge of normal pulp chamber anatomy and external tooth surface contour

>< Avoid in case of upper molar.

Avoid in case of lower molar

Proper and successful pin placementTwo fields - (i) Factors {Proper & successful pin placement depend (ii) Technique {on the factor and techniquesFactors for proper placement of pins : i. Pin size : Selection of pin size depend on : a. Amount of dentin pin size b. Retention required pin size ii. no. of pins : Depends on: a. Amount of lose tooth structure no. of pins b. Amount of dentine no. of pins c. Retention required no. of pins d. Size of pins no. of pins iii. Depth of pin in dentin : Maximum depth : 2-4mm. iv. Inter pin distance : Optimum distance : 3-5mm. v. length or height of pin in cavity : * Maximum height : 2mm. * 1-5 or 2mm minimum amalgam should be present above the cavity end of pin.

Proper & successful placement of pin

Factors of proper & successful placement of pin : (vi). Location or distribution of pins : a. The pin should always be placed midway between the pulp and tooth surface b. Place at cervical 1-3 rd of molars & premolars. c. Where greatest bulk of amalgam can be placed (minimum 1.5mm) d. As close as possible to the line angles e. Where the greatest bulk of dentin is present f. 0.5mm away from DEJ g. 0.5mm away from axial or vertical wall cavity h. Always on flate surface / even the different levels i. Use one pin her cusp for TMS (regular) Two or more for TMS (minimum), friction lock or cemented pins j. Limited on. Of pins should be used

Proper & successful placement of pinFactors : (vii) direction of pins : a. Pin is placed always midway between pulp chamber and tooth surface. b. Always place the pins at the line angles of the tooth.

( C ) The following areas should be avoided : i. Pulp-chamber {areas of pulp-proximity} ii. Isthmus area iii. Bi and Tri furcation areas iv. Concavities or flutings on the outer surfaces of tooth v. Where amount of dentine is too less yo place pin e.g. Mesiofacial corners of molar teeth vi. Too close enamel or DEJ

Pin Retained Restoration

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