L4. Pin Retained Restorations

what are the (3) types of pins used?

1. cemented

2. friction lock

3. self-threading

what is the downside of using pins?

may loose tooth if the pin is place wrong — it may cause internal or external perforation

the (3) types of pins differ in:

• hole diameter

• length of pin in tooth

• retention

why should you drill a hole smaller than the pin when using self-threading pins?

smaller hole + larger pin = friction

which type of pin is the most retentive?

self-threading

self-threading pins require resiliency of ____ for retention

dentin

self-threading pins can cause dentin _____

crazing

self-threading pins are also

self-shearing

self-threading pins are placed with (2):

1. hand wrench

2. latch type contra-angled slow speed

self-threading pins should be place __mm into the tooth and __mm outside of the tooth

• 2mm

• 2mm

(2 × 2 rule)

(T/F)

Pins make the tooth weaker.

True

Pins ___ resistance

worsen

Pins ___ retention

improve

Self-threading pins have a slight ___ on the pin head for retention

undercut

When should you use a hand wrench for pin placement?

limited inter-arch space

should you use low or high speed when placing pins?

low speed

what kind of handpiece head do you use for pin placement?

contra-angled latch type

you should place (1) pin per

missing cusp

can pins be placed at different levels?

YES — just has to be on a flat surface

what is the acceptable interpin distance?

3-5 mm

what is an important factor to consider when placing pins?

tooth size

pins should always be placed in

dentin

pins should be no closer than 1 mm to the

DEJ

pins should be no closer than 1.5 mm to the

external tooth if below the CEJ

what can you also place when using pins for secondary retention?

slots

pins are a ____ of defense

last line

do pins improve resistance or retention?

RETENTION — worsens resistance

why is adequate clearance around the pin necessary for amalgam restoratiosn?

need room for proper amalgam condensation

what is the name of the small, rounded, slot-like retention feature placed around pins?

axial cove

you need around __ mm of clearance around the pin

1mm

pins should NOT be placed ___ occlusal contacts

below

why should you use current radiographs when assessing pin placement?

must compensate for:

1. drifting

2. tilting

3. rotation

(of tooth in question)

what are (2) factors affecting pin locatino?

1. pulp

2. external tooth morphology

you should avoid placing pins on the mesial of the _______ premolar

maxillary first premolar — has mesial furcation

As a general rule, in the cervical third of molars and premolars, pin holes are located near

line angles

pin placement for maxillary teeth

pin placement for mandibular teeth

what are (2) locations to avoid when placing pins?

1. furcations

2. root indentations

which tooth has a mesial furcation?

mesial of maxillary 1st premolar

what must you consider when placing pins on mandibular molars?

1. mid-lingual bifurcation

2. mid-facial bifurcation

what must you consider when placing pins on maxillary molars?

1. mid-facial furcation

2. mid-mesial furcation

3. mid-distal furcation

what are (2) areas to avoid at the risk of perforating the pulp?

1. Mesiofacial corner of maxillary 1st molar

2. Mesiofacial corner of mandibular molar

why shouldn’t you place pins in the distal of mandibular 2nd molars?

tooth angulation

why shouldn’t you place pins in the lingual of maxillary molars?

root angulation

are younger patients more or less likely to have pulp perforations when placing pins?

MORE — higher pulp horns

why are older patients at less risk of pulpal perforations when placing pins?

have lower pulp horns — pulp horns recede with continued trauma

pilot holes are prepared with a ___ burn

½ round bur

why should you use a ½ round bur to prepare a pilot hole?

prevent drill crawling

why is it important that pins do NOT contact the bottom of the pin hole?

if it makes contact with the bottom of the pin hole, it will create stress on the tooth and cause it to fracture

the pin channel is prepared using the _____ attachment

contra-angle latch

you should also use _____ attachment and ____ setting

• torque reduction attachment

• forward setting

why must you create a recessed shoulder when preparing a pin hole?

to prevent stress upon pin placement — creates a small space between the pin and the bottom of the pinhole

describe the process of creating a pin hole

1. drill and then stop before placing a shoulder

2. wait 15 seconds to see if there is blood

3. add shoulder

why should you drill pin holes quickly?

the longer you place the bur inside, the wider the diameter of the pinhole becomes

correct channel drilling and pin placement does what (3) things?

1. creates an occlusal shoulder for adequate seating

2. prevents the pin tip from reaching the bottom of the pin channel

3. minimizes stress in the pin channel

Identify (3) errors with this pin placement

1. No occlusal shoulder

2. Inadequate seating

3. Pulp exposure

(will probably fracture tooth due to high stress or cause a pulpal perforation

why is it difficult to assess pin placement with radiographs?

hard to correctly identify pulpal perforations

• “pulpal perforations” may actually be the result of superimposition of pin onto the pulp chamber

which type of perforation is slightly easier to identify radiographically?

external

are external perforations from pins repairable?

Possibly — if the pin doesn’t go into the bone or pulp chamber

1. Create gingival flap

2. Drill off excess pin

3. Fill with amalgam or composite

what issue can external pin perforations cause?

perio defect