March 9, 2009 STI

Restoration of the Broken Down Tooth 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 missingWhen 1+ cusps need recappingWhen increased resistance and retention forms

are needed Pins, potholes and other retentive measures

Complex Amalgam Restorations Causes for large amounts of tooth

structure missing: (objective 1)

o Existing carieso Previously placed restorative material o Fractured tooth structureo Remain tooth structure is weak

Indications and Contraindications for Pin AmalgamThere are a number of factors to consider when

restoring a broken down tooth: (objective 2)

• 1. Age and health of the patiento 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 dentitiono 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

• 4. What is the prognosis?• 5. Economics

o Cast restoration is more expensive because of time and lab work

• 6. Aestheticso 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)

• FinCore build-up in anticipation of a cast restoration (See network presentation Foundations)

• Interim restorationo 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.

Treatment Plan ConsiderationsWhat 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 treatmento Orthodontic treatmento 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

(fluid, pH, thermal insults, changes, bacteria)Provides an anatomical contour Healthier gingival tissueFacilitate control of caries and plaqueProvide resistance against fractures

Rules for Cusp Removal

If unsupported tooth structure OR caries extension from primary groove to cusp tip is: (objective 7)

o ½ the distance: NO removal is indicatedo ½ to 2/3 the distance: Consider cusp removalo Over 2/3 the distance: Remove the cusp

Final Amalgam must have 2 mm of thickness over cusp

Rules for Cusp Removal

½ the distance: No removal is indicated

½ to 2/3 the distance: Consider cusp removal

Over 2/3 the distance: Remove the cusp

(objective 7)

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

Amalgapino Depth: At least 1 mmo 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

undercuto Depth: 0.5 – 0.75 mm deepo Width: 0.5 – 1.0 mm wideo Length: At least 1.0 mm in lengtho It should be 0.5 mm from DEJ

Slots, Amalgapins, Postholes Amalgapins Slots, Amalgapins, Postholes, etc. Threaded Pins Slots

The Pin Retained Amalgam 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

appointmentso Increase in resistance and retention formo Economic factorso Inexpensive restorative procedure

The Pin Retained Amalgam Disadvantages (objective 9)

o Possible microfractures of dentino Preparation may create small fractures or lines

o Microleakageo Decrease in strength of amalgamo 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 surfaceo Final tooth anatomy difficult to achieve with large

complex restorations

Types of Pins

Cemented Pins – 1958 (objective 10).001 to .002 inch larger hole drilled in dentin

Types of Pins

Friction Lock Pins – 1966Hole is .001 inch smaller than pin diameterTapped to place

Types of Pins

Self Threading Pins – 1966.003 to .004 inch smaller holeScrewed to place.

Factors Affecting Retention (objective 11)

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

Factors Affecting Retention What should the length of the pin be?

o Over 2mm in dentino .024 Minimum pin fractures on removalo .031 Regular pin – dentin fractureso Over 2mm in amalgamo .024 Minimum pin fractureso .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

The Treadmate System: What Size Pin? (objective 12)

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]).

Where is a pin placed in posterior teeth? (objective 13)

• 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**

ContraindicationsExisting 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

MOD Preparation

Prepare occlusal amalgam preparation (objective 15)

Extend to contact areas Drop proximal boxes in normal manner Occlusal depth: 1.5 – 1.8 mm deep

Cusp Reduction (objective 16)

• 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

Gingival Seat

• Establish gingival seat on buccal continuous with mesial

• 1.0 mm in width

• Axial walls parallel with long axis • 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)

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

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

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 hemostato Bend the pin

• Evaluate pin regarding contour of restoration

• Provide bulk of amalgam around pin• TMS bending tool only

Restoration (objective 19)

• Matrix placement • Correct wedging from lingual• Condensation and carving• Condense around pin• Cusp contours• Cusp inclines• Cusp height• Cusp tip placement