6-Complex Amalgam ( Pin Retained) Restoration

8/13/2019 6-Complex Amalgam ( Pin Retained) Restoration

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Operative dentistry

Dr lobna abo elnasr


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Complex amalgam ( pin retained) restoration

Complex cavity involve more than 2 sufaces + capping of 1

or 2 casps


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Indication:

Controlled restoration in tooth with questionable pulp or periodontal prognosis

Contolled restoration in tooth with acute or sever caries

Definite final restoration

Foundation under fixed restoration

Alternative fo fixed crown and bridges due to high cost

Interim restoration for teeth requie occlusal adjustment

Old age


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Resistance form : box like pepaation + removal of undermined enamel

Retention form: depends on remaining tooth structure pins and slot

more auxillary retention( locks , coves)

What are the goals of contolled restoration

Resistance of tooth against fracture

Protect pulp from oral fluidsControl of caies and plaque

Anatomical contour to protect gingival tissue


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Contraindication:

tooth in esthetic area

patient with occlusal problem

Tooth cannt restoed directly due to anatomical or fuctional consideration

Advantages:

Cheaper than indirect crown

Conservation of time one appointment


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Dis advantages:

dentinal microfracture during pin hole and slot preparation making internal stresses

Microleakage around all types of pins

Decrease strength of amalgam ( tensile strength of amalgam , horizontal stresses of

pins)

Resistance form doesnot protect the tooth from fracture as extracoronal restoration

Penetration and perforation into the pulp and external tooth structure especially with

pinDifficulty in obtaining proper contour especially with lage cavity

NB

Vetical: parallel to long axis

Horizontal : peripendicular to long axis


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Pin etained amalgam estoration:

Definition: any restoration gaining resistance and retention from one or more pins

which cannt be gained from slot , locks, undercuts

Site: large class 2, class 4 on distal surface of upper canine

Tooth preparation:

Initial tooth preparation:

Same as for amalgam when fasciolingual extention of occlusal prepaation exceeds 2

thirds or more of distance between fascial and lingual casp


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Casp capping:

week casp , cavity extend to or more than 2 thirds of distance between casp tip and

central groove

Initially by depth orientation groove 2 mm on

functional casp and 1.5 mm on non

functional casp


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Sharp internal corners rounded decease stress concentration,increase resistance form

resistance form : with flat pulpal and gingival walls

Retention form: slight convergence of fascial and lingual walls fascial and lingual

walls plus fascial and lingual groove

Final tooth preparation:

Removal of caries , old restoration

Calcium hydroxide liner RMGIC liner or base shouldnot extend closer than 1 mm toslot or pin

Coves peripenicular to long axis locks parallel to long axis

Casp reduction decease height of vertical walls so decrease retention


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Pin hole preparation

By using twist drill latch type or depth

limiting drill at low speed ( 300-500) RPM

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


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Drill cant be used for more than 20 holes otherwise it will be dull

dull drill: increase the pressure on handpiece, increase the frictional heat and cracks in

dentin

Location of the pin hole:

How to determine the location of the pinhole:

Knowing the anatomy of tooth and pulp

Radiograph

Piodontal probe

Patient age

Pin should be placed in aeas of greatestbulk of amalgam

pin hole is placed at cevical third or molars

and premolars not closer than 0.5 mm to

DEJ not closer than 1.5 mm from external

surface


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Correct angulation very important to avoid external surface perforation or amalgam

penetration

We can put the drill in gingival cevice and

adjust flat to tooth surface move on occlusal

surface without changing angulation starting

drill parrellel to adjacent external surface


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For better condesation of amalgam , beter clearence we make a recess by depth 0.5

mm in the vetical wall interior to pin by 245 bur for adquate condensation of amalgam


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Ppilote hole is made by ound bur 0.2 mm them complete with the drill to avoid slipping of

the drill ( cawling)

For inadquate depth we use depth limiting

drill on the surface

For retention we can place 2 pins and more

but with rules

pins r placed at different vertical

levels to reduce vertical stresses


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Inter pin distance from 3-5 mm

External perforation occurs in :

ptominent mesial concavity on upper fist molar

midlingual and midfascial of lower first and second molar

midfascial , midmesial and middistal of upper first and second molar

there are critical location ( dont put pin there)

Distal of lower molar

Lingual of ypper molars

Tiltedt teeth

When there is limited interarch space , care must be taken to avoid externalperforation on distal

Rule: one pin for missing axial line angle more pins more retention but pins reduceresistance form so tooth liable more to fracture

For occluso gingival reduction by 2 mm no need for pins


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Disadvantages:

vertical and horizontal stresses formed during insertion leading to dentinal crazing

great danger on pulp

Advantages:

Versatility

Wide range of sizes

Color coding system

Greater retention

Gold plated system so leminate the possibility for corrosion


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Cemented pins:

Depth of the hole 3- 4mm

Pin hole diameter larger than pin diameter

Pins used ae stainless steel may be threaded or serrated

Frictional lock

Diameter of pin hole smaller than pin diameterPins ae tapped in place retained by resiliency of dentin

More retentive than cemented one


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Self threaded pin (TMS)

SELF SHEARING

Titanium o stainless steel

Color coded plastic sleeves

Used in latch type contraangle

Once the pin reach the bottom of the hole shearing is off

STANDARD PIN

Length of the pin is 7 mm

The only pin not applied in the hole by the latch type conta only by hand wrench


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Flattened end to be engaged in hand wrench feeling reaching the

bottom of hole by tactile sense it can be reversed on quater to one half

turn after insertion to full depth to reduce stesses at the apical end of

the pin hole


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Two in one:

2 pins one shorter than the other long one is 9.5 mm

once it each the bottom it shears in half leaving length of the pin extending from dentin

with the other half r emaining in hand wrench


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Contraangle for link series , link plus

hand wrench:

It is moving in clockwise direction and

reversed quarter to half turn in anticlock

wise direction

It is used only for standard


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Adjust ment of length of pin:

Length of the pin in amalgam is 2 mm

Thickness of amalgam from the end of pin is

2 mm

Emoval of excess length of pin by high

speed hand piece

Duing removal of excess tweezethe pin with

TMS bending toolto allow enough thicknessof amalgam occlusogingivallyr stabilize the

pin , high vaccum suction near it to remove

excess

Or by bending


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Size of the pin

color coding systtem, gold larger than silver larger than red larger than pink

Factors affecting selection ofnpin on base of size :

Amount of retention desired

Amount of dentin available to receive pin

For sevely involved posterior tooth use red one to reduce risk of crazing of dentin ,

pilpal penetration, potentional perforation

Silver one used as abackup when pinhole over prepaed for red (wide hole gives silverpin)

Pink pin is too small to give retention


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Silver pin called minim

red pin callen minikin


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How many pins to be used depends on:

Amount of dentin available

Amount of retention required

Amount of lost tooth sttrucure

Size of pin ( silver pin is more retentive

than red one)

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6-Complex Amalgam ( Pin Retained) Restoration

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