Class II MODB Pin Amalgam

1. March 9, 2009 STI Class II MODB Pin Amalgam

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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.

9. 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

10. 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

11. Rules for Cusp Removal • If unsupported tooth structure OR caries extension from primary groove to cusp tip is: (objective 7) • ½ the distance: NOremoval is indicated • ½ to 2/3 the distance: Considercusp removal • Over 2/3 the distance: Removethe cusp • Final Amalgam must have 2 mm of thickness over cusp

12. 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

13. 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

14. Amalgapin • Amalgapin • Depth: At least 1 mm • Width: It should be wide enough to receive a small condenser

15. 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

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

17. 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

18. 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

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

20. Types of Pins • Friction Lock Pins – 1966 • Hole is .001 inch smaller than pin diameter • Tapped to place

21. Types of Pins • Self Threading Pins – 1966 • .003 to .004 inch smaller hole • Screwed to place.

22. 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

23. 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 • .031 Regular pin – dentin fractures • Bottom Line: 2 mm is an ideallength into dentin and amalgam for strength of the dentin and retention of the amalgam.

24. 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

25. The Treadmate System: Uses (objective 12) • Common • Versatile • Many pin sizes • Excellent Retentiveness • Color coding system • Corrosion resistant

26. 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]).

27. 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

28. 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.

29. 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)

30. 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

31. 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

32. 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

33. 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)

34. 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)

35. 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

36. 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

37. 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

38. 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

39. Restoration (objective 19) • Matrix placement • Correct wedging from lingual • Condensation and carving • Condense around pin • Cusp contours • Cusp inclines • Cusp height • Cusp tip placement