Transcript Single Tooth Indirect

March 9, 2009
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
 Pins, potholes and other retentive measures


Causes for large amounts of tooth structure
missing:
o Existing caries
o Previously placed restorative material
o Fractured tooth structure
o Remain tooth structure is weak
There are a number of factors to consider:
• 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.
•
Resistance versus retention: Availability of
resistance and retention form
•
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 distalinsical surface of canine
What is the prognosis?
Economics
o Cast restoration is more expensive because of time and lab
•
work
Aesthetics
o Silver fillings are not aesthetic for anterior teeth
•
Definition: The ability of the tooth and
material to withstand forces—all the forces
coming down—directed along the long axis of
the tooth.
•
•
•
•
•
•
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
•
Definition: The ability of the tooth to retain the
restoration when tipping or lifting forces are
applied.
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
•
What is the tooth going to be considered for?
 Fixed or removable partial denture
o Abutment tooth


Final Restoration
Provisional restoration: foundation or build
up
o Periodontal treatment
o Orthodontic treatment
o Final restorations are desirable only until all
orthodontic and periodontal treatments are
finished
FinCore build-up in anticipation of a cast restoration
(See network presentation Foundations)
• Interim restoration
•
•
•
o IRM or temporary crown
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.
Fracture potential of tooth
Tooth structure
Put a temporary restoration to see how the tooth
reacts before placing anything permanent on there.

What does a controlled restoration achieve?
 Helps to protect the pulp from the oral cavity




(fluid, pH, thermal insults, changes, bacteria)
Provides an anatomical contour
Healthier gingival tissue
Facilitate control of caries and plaque
Provide resistance against fractures

If unsupported tooth structure OR caries
extension from primary groove to cusp tip is:
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

Final Amalgam must have 2 mm of thickness
over cusp
•
More tooth structure lost = more auxilliary retention
• 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
• Slots
• Grooves
• Boxes
•
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
o Depth: At least 1 mm
o Width: It should be wide enough to receive a small
condenser

The Slot
o #34 inverted cone provides a little bit of an
undercut
o 0.5 – 0.75 mm deep
o 0.5 – 1.0 mm wide
o At least 1.0 mm in length
o 0.5 mm from DEJ




Amalgapins
Slots, Amalgapins, Postholes, etc.
Threaded Pins
Slots

Advantages
o Conservation of tooth structure by pin placement
versus 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

Disadvantages
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


Cemented Pins – 1958
.001 to .002 inch larger hole drilled in dentin



Friction Lock Pins – 1966
Hole is .001 inch smaller than pin diameter
Tapped to place



Self Threading Pins – 1966
.003 to .004 inch smaller hole
Screwed to place.




Diameter: greater diameter = more retention
Number: more pins = more retention
Orientation: better if placed in a non-parallel
manner
Threaded v. Non Threaded
o Threaded have more retentive form


Type: from least to greatest retention
Cemented friction threaded is better

How long should 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.



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
betwewen the pin and the external surface






Common
Versatile
Many pin sizes
Excellent Retentiveness
Color coding system
Corrosion resistant





Posterior Teeth
Minuta – Worthless
Minikin – May be helpful
Minum – Best and most used; recommended
Regular – Avoid
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]).
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
•
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)




Standard Class II MOD outline
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




Prepare occlusal amalgam preparation
Extend to contact areas
Drop proximal boxes in normal manner
Occlusal depth: 1.5 – 1.8 mm deep
•
•
•
Extend out the buccal groove at the level of
the pulpal floor
Remove mesio-buccal cusp (#245)
Establish gingival seat on buccal continuous
with mesial
o mm in width
•
•
•
•
Establish gingival seat on buccal continuous
with mesial
1.0 mm in width
Axial walls parallel with long axis
Open proximal contacts distally and mesiolingually (GF 11, GF 12)




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)






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






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






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
•
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
•
•
•
Evaluate pin regarding contour of restoration
Provide bulk of amalgam around pin
TMS bending tool only
•
•
•
•
•
•
•
•
Matrix placement
Correct wedging from lingual
Condensation and carving
Condense around pin
Cusp contours
Cusp inclines
Cusp height
Cusp tip placement