Class II MODB Pin Amalgam March 9, 2009 STI Class II MODB Pin Amalgam These notes are taken from Dr. Reisfeis STI online presentation and slides. Restoration of Broken-Down Teeth:      Manual 310-318; Sturdevant 809-832 Website Presentations:  Foundations  &  Class II MODB pin amal & Placing the Pin - Movie

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 missing When 1+ cusps need recapping When 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) Existing caries Previously placed restorative material Fractured tooth structure 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 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. 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? Consider the function of the tooth and its relation to surrounding dentition If the patient has significant occlusal problems, then treatment may be contraindicated Class IV are rare because small anterior teeth involved Could be used on amalgam Class IV distal insical surface of canine 4. What is the prognosis? 5. Economics Cast restoration is more expensive because of time and lab work 6. Aesthetics Silver fillings are not aesthetic for anterior teeth They may be used as: control restorations in teeth that have a questionable pulpal and/or periodontal prognosis, control restorations in teeth with acute and severe caries, definitive final restorations, or Foundations In a tooth severely involved with caries or existing restorative material, any tooth structure subject to potential fracture must be removed and restored properly There are designs for amalgam that improve resistance form of a tooth

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 restoration IRM or temporary crown Symptomatic Caries activity If there is extensive caries, then a root canal might be necessary. If there is high caries activity, then you do not want to put a casting on this tooth. 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 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 It is an abutment tooth Final Restoration—is the tooth for final restoration? Provisional restoration: or foundation or build up Periodontal treatment Orthodontic treatment 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 tissue Facilitate control of caries and plaque Provide resistance against fractures

Rules for Cusp Removal If unsupported tooth structure OR caries extension from primary groove to cusp tip is: (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 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 You get the most retention form from the pulp chamber. 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 Depth: At least 1 mm Width: It should be wide enough to receive a small condenser

The Slot The Slot #34 inverted cone provides a little bit of an undercut Depth: 0.5 – 0.75 mm deep Width: 0.5 – 1.0 mm wide Length: At least 1.0 mm in length It should be 0.5 mm from DEJ

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

The Pin Retained Amalgam Advantages (objective 9) Conservation of tooth structure by pin placement vs. crown placement (indirect restoration) Less chair time Cast restoration requires multiple appointments Increase in resistance and retention form Economic factors Inexpensive restorative procedure A pinretained restoration may be defined as any restoration requiring the placement of one or more pins in the dentin to provide adequate resistance and retention forms. Pins are used whenever adequate resistance and retention forms cannot be established with slots, locks, or undercuts only. The pin-retained amalgam is an important adjunct in the restoration of teeth with extensive caries or fractures. 47 Amalgam restorations including pins have significantly greater retention than those using boxes only or those relying solely on bonding systems

The Pin Retained Amalgam Disadvantages (objective 9) Possible microfractures of dentin Preparation may create small fractures or lines Microleakage Decrease in strength of amalgam More difficult resistance form There is at least 2 mm of restorative material over pin to have enough to resist form—occlusion from above Possible perforations to the pulp or external surface 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 – 1966 Hole is .001 inch smaller than pin diameter Tapped to place

Types of Pins 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 non-parallel manner Threaded v. Non Threaded 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? Over 2mm in dentin .024 Minimum pin fractures on removal .031 Regular pin – dentin fractures Over 2mm in amalgam .024 Minimum pin 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. 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

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 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) Objective 17

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: Cut pin to length Use a small round bur or 169L cutting perpendicular to the pin Hold base of pin with hemostat 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