pin retained restoration
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Pin Retained Restoration
Retentive PinsDr. Miles Markley(1958)- introduced stainless steel pins to provide retention and resistance form. Pins retain the restoration in the prepared tooth structure together and secondly, reinforce the tooth by cross-splinting of weakened cusp.
Indications:y Grossly mutilated teeth- large restorations may
be fracture of may be lost due to occlusal loadingy Extended preparations-pin placement is
recommended if the large interproximal restoration, restoration of cusp shapes or of cavity extended beyond the lines angles, is to be done.y Cores for full coverage restoration- by pin-
supported amalgam, core can be placed in less time and expense.
Indications:y Extensive Class V restoration- pin placement
tends to reinforce the restoration.y Time period and economic factors- no chance for
second appointment or economic problem regarding cast gold restoration, pin- retained amalgam restoration can be the restoration of choice.
Advantages:y Conservation of tooth material y Number of appointments 1 appointment is
required for pin retainery Resistance and retention form y Economic- inexpensive
Disadvantages:y Pulpectomized and pulpectomized teeth- increase y y y y y
chances of fracture of dentin due to dehydration Dentinal microfractures Microleakage Strength of amalgam Perforation due to misdirection of care Tooth Anatomy- some cases it is not possible to achieve proper contours and occlusal contact with pin retained restoration
Types of Piny Self-threading pins y Cemented pins y Friction-locked pins
Self-Threading Pinsy Most retentive y Pinholes are slightly smaller in
diameter (0.038 to 0.1mm) than the pin diameter y Pin retained due to mechanical grasp y Viscoelastic property of the dentin allows insertion of a threaded pin into a hole of a smaller diameter
Self-Threading PinsAdvantages: y Superior retention y Less depth y No cementing medium Disadvantages: y Maximum pulpal stress- pin is inserted perpendicular to the pulp y Maximum dentin stress
Cemented Pinsy Least retentive y Pinholes should be 0.025 to
0.05mm larger than the diameter of the pin y Depth hole in dentin should be 3 to 4mm
Friction-Locked Pinsy Intermediate retention y Diameter of the pinhole is
0.025mm smaller than the diameter of pinhole pin y Retained due to resiliency of dentin
Number of Pinsy Extensive number of pins should be avoided y One pin must be placed for each missing cusp
and one pin for each missing proximal surface y ** Certain factors may alter this rule, due to esthetic consideration. **
Length of Pin into Dentin and Amalgam
y Pin extension of 2mm into dentin and amalgam
provide maximum required retention y ** Pin extension greater than 2mm is contraindicated. **
Cavity Preparation for Pin Retained Amalgam Restorationsy Cavity preparation y Excavation of carious dentin y Rim-preparation (should finish) y Placement of amalgam matrix y Base/Liner application (after final preparation) y Pinholes are made y Placement of pins y Coves preparation in axial wall y Condensation of amalgam around pins y Polishing after 24 hours
PINHOLE PREPARATION:No.bur used to prepare a pilot hole (dimple) y To permit more accurate placement of the twist drill y Prevent the drill from crawling once it has began to rotate y Optimal depth of the pinhole into the dentin is 2mm
PINHOLE PREPARATION:y The hole should be prepared
on flat surface and the drill perpendicular to it. y Place flat thin-bladed hand instrument into the crevice and against the external surface of the tooth To indicate the proper angulations for the drill
PINHOLE PREPARATION:y Place the drill tip in its proper position y Hand piece rotating at very low speed y Apply pressure to the drill y Prepare pinhole in one or two movement y until the depth-limiting portion is reached y Remove the drill from pinhole
Failure of Pin Retained Restorationy Fracture may occury Improper condensation or improper trituration y Pin retained restoration failure
y Separation at interface of the pin and restorative
material y Broken pins and drills y Enlarge pinholes y Pulpal penetration and periodontal perforation
Pre-operative View
Preparation after Pin Placement
Restoration immediately after Completion
Restoration after 5 years
Referencey Textbook of Operative Dentistry by Chandra y http://www.pdfebooksdownloads.com
Salamat po..
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