Transcript Single Tooth Indirect

March 9, 2009
STI
Restoration of the Broken Down
Tooth
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Scenario: Restoration of broken teeth where
large amounts of structure missing could be
because of different things—fractured tooth,
fractured restoration, or caries
Solution: Complex posterior amalgam
restorations should be considered when
 Large amounts of tooth structure are missing
 When 1+ cusps need recapping
 When increased resistance and retention forms
are needed
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Pins, potholes and other retentive measures
Complex Amalgam Restorations
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Causes for large amounts of tooth
structure missing: (objective 1)
o Existing caries
o Previously placed restorative material
o Fractured tooth structure
o Remain tooth structure is weak
Indications and Contraindications
for Pin Amalgam
There are a number of factors to consider when
restoring a broken down tooth: (objective 2)
• 1. Age and health of the patient
o Example: If the patient is 6 years old, you do not want
to place a cast on the tooth. Build it up with a pin
retained amalgam. Wait until the patient ages and
tooth erupts to give it more length to place a crown.
o Example: If the patient is older, a cast takes more
time and several appointments. Do a pin retained
restoration of some manner.
•
2. Resistance versus retention: Availability of
resistance and retention form
Indications and Contraindications
•
3. How does the tooth affect the overall treatment
plan?
o Consider the function of the tooth and its relation to
surrounding dentition
o If the patient has significant occlusal problems, then
treatment may be contraindicated
o Class IV are rare because small anterior teeth involved
o Could be used on amalgam Class IV distal insical surface of
canine
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4. What is the prognosis?
5. Economics
o Cast restoration is more expensive because of time and
lab work
•
6. Aesthetics
o Silver fillings are not aesthetic for anterior teeth
Resistance Form
•
Definition: The ability of the tooth and
material to withstand forces—all the forces
coming down—directed along the long axis
of the tooth. (objective 3)
Criteria for amalgam restoration
• Flat pulpal floors
• Cavity walls parallel to the long axis
• Preservation of cusps and marginal ridges
• Rounded internal line angles
• Adequate thickness of restorative material
• Reduction of cusps when indicated
Retention Form
•
Definition: The ability of the tooth to retain the
restoration when tipping or lifting forces are
applied. (objective 4)
Criteria for amalgam restoration
• It is placed to prevent restoration from being
lifted out of the tooth
• Converging occlusal walls
• Grooves, pins, slots, steps, amalgapins
• Occlusal dovetail (keeps it from going distally)
• Adhesive systems that bond amalgam to tooth
structure
Prognosis of the Tooth (objective 5)
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FinCore build-up in anticipation of a cast restoration
(See network presentation Foundations)
Interim restoration
o IRM or temporary crown
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Symptomatic
Caries activity
o If there is extensive caries, then a root canal might be
necessary.
o If there is high caries activity, then you do not want to put a
casting on this tooth.
o Control disease process first.
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Fracture potential of tooth
Tooth structure
Put a temporary restoration to see how the tooth
reacts before placing anything permanent on there.
Treatment Plan Considerations
What is the tooth going to be considered for?
(objective 6)
Do not treat one tooth up in the clinic. Consider
everything!
 Fixed or removable partial denture

o It is an abutment tooth
Final Restoration—is the tooth for final
restoration?
 Provisional restoration: or foundation or build up

o Periodontal treatment
o Orthodontic treatment
o Final restorations are desirable only until all
orthodontic and periodontal treatments are finished
Reasons for Controlling
Restoration

What does a controlled restoration
achieve? When we control a restoration
it:
 Helps to protect the pulp from the oral cavity
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(fluid, pH, thermal insults, changes, bacteria)
Provides an anatomical contour
Healthier gingival tissue
Facilitate control of caries and plaque
Provide resistance against fractures
Rules for Cusp Removal
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If unsupported tooth structure OR caries
extension from primary groove to cusp tip is:
(objective 7)
o ½ the distance: NO removal is indicated
o ½ to 2/3 the distance: Consider cusp removal
o Over 2/3 the distance: Remove the cusp
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Final Amalgam must have 2 mm of thickness
over cusp
Rules for Cusp Removal
(objective 7)
½ the distance: No removal
is indicated
½ to 2/3 the distance:
Consider cusp removal
Over 2/3 the distance:
Remove the cusp
Types of Auxilliary Retention
•
More tooth structure lost = more auxilliary
retention is needed
• Pins
• Pulp Chambers
o You get the most retention form from the pulp chamber.
o If this tooth had a root canal, then putting cast material
or direct material into pulp chamber gives best retention.
• Amalgapins: Prepare a 1 mm deep hole wide enough
for small condenser (see slide 14)
• Slots (see slide 15)
• Grooves: this is what we have been practicing
• Boxes: this is what we have been practicing
•
Pins, slots, and amalgam bonding techniques
can be used to enhance retention form when
there is not enough remaining tooth structure for
conventional retention features
Amalgapin

Amalgapin
o Depth: At least 1 mm
o Width: It should be wide enough to receive
a small condenser
The Slot

The Slot
o #34 inverted cone provides a little bit of an
undercut
o Depth: 0.5 – 0.75 mm deep
o Width: 0.5 – 1.0 mm wide
o Length: At least 1.0 mm in length
o It should be 0.5 mm from DEJ
Slots, Amalgapins, Postholes
Amalgapins
 Slots, Amalgapins, Postholes, etc.
 Threaded Pins
 Slots
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The Pin Retained Amalgam
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Advantages (objective 9)
o Conservation of tooth structure by pin
placement vs. crown placement (indirect
restoration)
o Less chair time
o Cast restoration requires multiple
appointments
o Increase in resistance and retention form
o Economic factors
o Inexpensive restorative procedure
The Pin Retained Amalgam
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Disadvantages (objective 9)
o Possible microfractures of dentin
o Preparation may create small fractures or lines
o Microleakage
o Decrease in strength of amalgam
o More difficult resistance form
o There is at least 2 mm of restorative material over pin to
have enough to resist form—occlusion from above
o Possible perforations to the pulp or external surface
o Final tooth anatomy difficult to achieve with large
complex restorations
Types of Pins
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Cemented Pins – 1958 (objective 10)
 .001 to .002 inch larger hole drilled in dentin
Types of Pins
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Friction Lock Pins – 1966
 Hole is .001 inch smaller than pin diameter
 Tapped to place
Types of Pins
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Self Threading Pins – 1966
 .003 to .004 inch smaller hole
 Screwed to place.
Factors Affecting Retention
(objective 11)
Diameter: greater diameter = more
retention
 Number: more pins = more retention
 Orientation: better if placed in a nonparallel manner
 Threaded v. Non Threaded

o Threaded have more retentive form
Type: from least to greatest retention
 Cemented friction threaded is better
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Factors Affecting Retention
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What should the length of the pin be?
o Over 2mm in dentin
o .024 Minimum pin fractures on removal
o .031 Regular pin – dentin fractures
o Over 2mm in amalgam
o .024 Minimum pin fractures
o .031 Regular pin – dentin fractures

Bottom Line: 2 mm is an ideal length into
dentin and amalgam for strength of the
dentin and retention of the amalgam.
Factors Affecting Retention

How should the pin be angled?
 The pin should be bent to position with the
contour of the final restoration
 It should provide adequate bulk of amalgam
between the pin and the external surface
The Treadmate System: Uses
(objective 12)
Common
 Versatile
 Many pin sizes
 Excellent Retentiveness
 Color coding system
 Corrosion resistant
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The Treadmate System: What
Size Pin? (objective 12)
Posterior Teeth
 Minuta – Worthless
 Minikin – May be helpful
 Minum – Best and most used;
recommended
 Regular – Avoid
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FIG . 19-13 Four sizes of TMS pins.
A, Regular ( 0.031 inch [0.78 mm]). B,
Minim (0.024 inch [0.61 mm]). C, Minikin
(0.019 inch [0.48 mm]). D, Minuta ( 0.015
inch [0.38 mm]).
Where is a pin placed in posterior
teeth? (objective 13)
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Know your pulp anatomy and external
tooth contours
Obtain a current radiograph
Check exterior contour with the periodontal
probe
Patient age (older patient: pulp recession)
Locate the bulk of amalgam
Check occlusion
Pinhole:
• At least 1mm from DEJ
• At least 1.5 mm from external surface
• At least 5mm between pins
Amalgam Bonding Agents
Amalgam does not bond to tooth structure
unless an amalgam bonding agent is used.
The primary advantages for amalgam bonding agents in most
clinical situations are the dentin sealing and improved resistance
form, but the increase in retention form is not significant.
Amalgam Bonding Agent
Indications
 Possible indications for amalgam bonding
procedures
 Large complex restorations
 Foundations
 Preparations lacking ideal retention
**Review typical cusp fracture sequence**
Contraindications
Existing quality mechanical retention (if you don’t
need it, then don’t use it)
Class II Outline Form
Standard Class II MOD outline (objective 14)
 Extend buccally 1.0 mm distal to buccal
groove – Do Not Stop in Groove
 Cervical length: Even with level of
mesial box
 In general, the preparation is larger
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MOD Preparation
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Prepare occlusal amalgam preparation
(objective 15)
Extend to contact areas
 Drop proximal boxes in normal manner
 Occlusal depth: 1.5 – 1.8 mm deep
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Cusp Reduction (objective 16)
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Extend out the buccal groove at the
level of the pulpal floor
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Remove mesio-buccal cusp (#245)
• Establish gingival seat on buccal
continuous with mesial
o mm in width
Gingival Seat
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Establish gingival seat on buccal
continuous with mesial
1.0 mm in width
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Axial walls parallel with long axis
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Open proximal contacts distally and
mesio-lingually (GF 11, GF 12)
Finalizing Preparation
Plane the facial wall, gingival seat, and
axial wall ( #10-11, GF 16)
 Establish S-Curves as necessary
 Smooth and finish all surfaces
 Bevel axio-pulpal line angles and place
retention (169L and ¼ round)
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Pin Placement (objective 18)
Instructor will place a "caries" area
 Place liner on pulpal floor
 Keep away from retentive areas and
walls
 Thin layer – less than 1.0 mm thick
 Indicate placement of pin
 Use ¼ round bur to dimple

Pin Placement Procedure
Flat surface – perpendicular to pin hole
 Prepare notch to receive pin (if
necessary)
 Drill is able to go to depth
 Condensation of amalgam can occur
 Pilot hole with ¼ round bur
 Confirm angulation – better to hit pulp
than to exit tooth
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Pin Placement Procedure
Rotate bur at slow speed (400 rpm) in
latch handpiece (check rotation)
 Enter in one fluid movement
 Exit in one movement
 Drill should NOT stop turning at any time
 Place pin in handpiece
 Place pin in hole and activate handpiece
until pin shears
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Pin Height and Pin Angle
•
If necessary:
o Cut pin to length
• Use a small round bur or 169L cutting
perpendicular to the pin
• Hold base of pin with hemostat
o Bend the pin
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Evaluate pin regarding contour of
restoration
Provide bulk of amalgam around pin
TMS bending tool only
Restoration (objective 19)
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Matrix placement
• Correct wedging from lingual
• Condensation and carving
• Condense around pin
• Cusp contours
• Cusp inclines
• Cusp height
• Cusp tip placement