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March 9, 2009.  Scenario: Restoration of broken teeth where large amounts of structure missing could be because of different things—fractured tooth,

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Presentation on theme: "March 9, 2009.  Scenario: Restoration of broken teeth where large amounts of structure missing could be because of different things—fractured tooth,"— Presentation transcript:

1 March 9, 2009

2  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  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

4 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

5 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

6 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

7 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

8 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

9 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.

10  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

11  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

12 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

13  Amalgapin o Depth: At least 1 mm o Width: It should be wide enough to receive a small condenser

14  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

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

16  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

17  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 complex restorations

18  Cemented Pins – 1958 .001 to.002 inch larger hole drilled in dentin

19  Friction Lock Pins – 1966  Hole is.001 inch smaller than pin diameter  Tapped to place

20  Self Threading Pins – 1966 .003 to.004 inch smaller hole  Screwed to place.

21  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

22  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.

23  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

24  Common  Versatile  Many pin sizes  Excellent Retentiveness  Color coding system  Corrosion resistant

25  Posterior Teeth  Minuta – Worthless  Minikin – May be helpful  Minum – Best and most used; recommended  Regular – Avoid FIG Four sizes of TMS pins. A, Regular ( inch [0.78 mm]). B, Minim (0.024 inch [0.61 mm]). C, Minikin (0.019 inch [0.48 mm]). D, Minuta ( inch [0.38 mm]).

26 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 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)

29  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

30  Prepare occlusal amalgam preparation  Extend to contact areas  Drop proximal boxes in normal manner  Occlusal depth: 1.5 – 1.8 mm deep

31 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

32 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)

33  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)

34  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

35  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

36  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

37 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

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

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