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Full Crown Module
 

Full Crown Module

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    Full Crown Module Full Crown Module Document Transcript

    • Learner Level 2 Full Crown Module Preparation of Teeth with previous restoration Restoration / Tooth # Porcelain Fused to Metal / #29 with MOD Amalgam Restoration Estimated Set Up Time: 1 hour Extensions: Estimated Completion Time: 6 hours FGC removal to PFM / #3 FGC / Short Clinical Crown # 20 I. Module Information In level 2 of the Full Crown Module, we are going to prepare a pre-molar tooth with previous amalgam to receive a PFM restoration. We are going to simulate a clinical scenario where the previous restoration has recurrent decay (Fig. 1) that requires treatment (Fig. 2). In the extension part of Level 2, you will learn how to remove an existing crown restoration that developed a recurrent decay along the margins and re-prepare the tooth to receive a new restoration. Additional extension is also designed for you to prepare a short clinical crown that would require additional retentive features due to the decay caused by the previous crown restoration. Fig. 1. Pre-operative photo of tooth #29 Fig. 2. Prepared tooth #29 to receive PFM with failing amalgam restoration and restoration recurrent caries II. Setting up of the Articulated Teeth Since this is a simulated exercise, tooth preparation should be done on a Frasaco ® Model mounted on the simulator. 1. Get tooth #29 with existing class II MOD amalgam restoration. (You may pick a tooth that has been used in your Operative course.) Full Crown Module: Learner Level 2 1 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • 2. With a black fine point Sharpie ® pen, draw a line along the margins of the amalgam restoration. The black line will be the recurrent decay for this exercise (Fig. 3). Fig. 3. Black line along the margins of amalgam restoration. Inset: Sharpie ® pen 3. Screw it on the space provided. 4. Mount the articulator in the simulated patient. 5. Prepare silicone putty matrix of the tooth and the adjacent teeth 6. Prepare your instruments (handpiece, burs and mouth mirrors, etc,) Clinical Relevance One of the indications that would require full crown restorations are teeth with existing large amalgam / composite restorations that have developing caries around the margins. Depending on the extent of the damage, these teeth may be restored back using amalgam, composite, inlays or onlays. However, if the remaining sound tooth structures would not support and retain these types of restorations, full crown can be a treatment of choice. One should make the determination whether an intracoronal or extracoronal restoration best suits the case. III. Preparing Tooth for Full Crown Restoration In restoring tooth with an existing large and failing restoration, there are several steps involve before we can restore it with a full crown restoration. A. Removal of existing restoration The goal of removing the existing amalgam restoration is to make sure that there will be adequate access on the cavity for clinical evaluation. Full Crown Module: Learner Level 2 2 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • 1. With your large round carbide bur, remove the amalgam from the cavity (Fig. 4). 2. Make sure to apply a water coolant in your handpiece while trying to “bur-out” the alloy. 3. Avoid damaging the existing cavity preparation. Fig. 4. Removal of existing amalgam restoration B. Evaluating the remaining tooth structures The goals of evaluating the remaining tooth structures are (1) complete removal of existing caries or decay of the cavity, (2) complete removal of unsupported enamel and (3) provide retentive features for the amalgam / build up material. 4. Once the alloy has been removed, color the cavity with your black sharpie® pen simulating the presence of caries (Fig. 5). Fig. 5. Presence of caries underneath the failing amalgam restoration upon removal of the alloy Full Crown Module: Learner Level 2 3 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • 5. Re-prepare the cavity (Fig. 6): a. Widen the isthmus to remove the caries b. Deepen the pulpal floor c. Deepen and widen the proximal boxes Fig. 6. Re-preparing the cavity 6. Make sure that there are no caries (black ink) present in the cavity. 7. Make sure that there are no unsupported enamel (Fig. 7). 8. Provide retention for your amalgam/ build up material (Fig. 8). Fig. 7. Caries-free cavity Fig. 8. Providing mechanical retention to amalgam / build-up material Full Crown Module: Learner Level 2 4 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • Instructor’s Note Since the cavity will be re-build with amalgam material, you should provide adequate retention for this material. Otherwise, during crown preparation (in succeeding steps), your build up material might break off. Therefore, make sure you have adequate mechanical retention at this point. Clinical Relevance The decision to remove the existing restoration depends primarily in the diagnosis of the clinical condition. Radiographs and clinical examination are just few of the several diagnostic tools that must be used to warrant such decision. If the existing restoration is carious, it must be removed. If it is not, then there is no need to remove it. However, when it doubt especially when you were not the one who restored the existing amalgam, it is always prudent to remove the existing restoration to make sure that there will be no caries left in the tooth when we crown it, Use water coolant from the handpiece when removing the existing amalgam / composite restoration. This prevents generating a lot of heat and preventing trauma or insult to the pulp. Once the restoration is removed, excavate all the caries from the cavity and re-prepare that tooth to receive the amalgam or buildup material. Make sure that there are no caries left and unsupported enamel for these will weaken the tooth. C. Restoring the cavity with build-up material The goal of restoring the cavity with build-up material is to create adequate bulk and form for retention and resistance of tooth prior to preparation for full crown restoration. 9. Place the matrix band (Fig. 9) Fig. 9. Matrix band placement Full Crown Module: Learner Level 2 5 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • 10. Mix amalgam 11. Condense amalgam into the cavity (Fig. 10) Fig. 10. Condense amalgam 12. Burnish 13. Wait for amalgam to set (Fig. 11) Fig. 11. Amalgam as build-up material D. Full crown preparation –PFM The goal of preparing the tooth to receive full crown restoration is to strengthen is the tooth weakened by caries and amalgam/ composite / build-up material. 14. Prepare tooth #29 to receive a PFM restoration. a. Occlusal reduction – 1.5 mm b. Buccal reductions- - 1.3 mm and 3-degree taper - Two-plane reduction required c. Lingual reductions- 1.0 mm and 3-dgree taper Full Crown Module: Learner Level 2 6 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • d. Proximal reductions- no proximal contact, no undercut and sufficient convergence e. Functional cusp bevel- 0.5 mm more on the functional cusp f. Margin preparation- - 1.3 mm shoulder margin on the facial - 0.5 mm chamfer margin on the lingual - 0.5 mm above the margin of gingiva *PROXIMAL MARGIN REDUCTION In establishing your proximal margin, you have to set the margin at the level more cervical to the margin of your amalgam restoration. g. Finishing your preparation – round off sharp angles and provide a smooth finish on the tooth. Clinical Relevance When preparing a tooth to receive a full crown restoration, marginal integrity is an important principle because this seals the full crown restoration from ingress of oral fluids and prevents dissolution of cement. Therefore, margins should be clear and well defined so we can achieve accurate fit. When the tooth has an amalgam, composite or any buildup material, the margins of the full crown should be placed beyond the interface of the aforementioned materials and should be at a sound tooth structure. By doing this, we can avoid microleakage and prevents ingress of oral fluids in the interface. In such situations, never place your margin on amalgam, composite or build up material or never place your margin at the interface. Margins should be at the sound tooth structure and more cervical than the interface. IV. Evaluating the Preparation Check your preparation. Follow the evaluation procedures you learned in the previous level. Use the evaluation criteria. At this level, be sure to answer the question below: Are margins along the proximal surface located more cervical than the amalgam restoration? CONGRATULATIONS! You made it! You have finished Level 2 of the Full Crown Module. You may proceed doing the Extensions. In the extensions, you will prepare a tooth with an existing full crown margin that has marginal decay or recurrent caries along the margins. This will expand your understanding of the principles that were covered in this level and provide you with further practice and develop efficiency. Let’s go! Full Crown Module: Learner Level 2 7 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • Occlusal Reduction • 1.5 mm • Provide Adequate Occlusal Clearance • Occlusal Planar Reduction Functional Cusp Bevel • Additional 0.5 mm reduction Preparation Finish • Located at • Remove sharp area Functional Cusp • Smooth the surfaces Second Plane of Buccal Reduction • Follows the anatomical contour Lingual Reduction • Remove anatomical undercut • 3-degree taper Buccal Reduction • Remove anatomical undercut • 3-degree taper Chamfer Margin (Lingual) • 0.5 mm reduction • 0.5 mm above the margin of the gingiva PFM #29 with MOD amalgam Shoulder Margin (Buccal) Margin Junction (Interproxima) • 1.3 mm reduction • Follows the anatomical • 0.5 mm above the margin contour of the margin of of the gingiva Build-up Material gingiva • Must retain in the tooth • Provide smooth transition • Should provide support to between shoulder and the crown chamfer in the interproximal area • MARGIN SHOULD BE CERVICAL THAN THE AMALGAM RESTORATION General Features of Porcelain Fused to Metal (PFM) Crown Preparation for Posterior Teeth with Build- up Material Full Crown Module: Learner Level 2 8 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • Instructor’s Notes on Module Extensions Level 2 The module extensions in level 2 are designed to further enhance your clinical knowledge and dexterity skills in managing teeth with failing restoration. You will learn how to remove an existing full crown restoration and re-prepare the tooth to remove the caries along the margins and receive a new crown restoration. You will also learn how to prepare a short clinical crown that has been damage significantly by the existing crown restoration. Full Gold Crown Removal to Porcelain Fused to Metal / 3 1. Get tooth #3 with existing FGC preparation (Fig. 1) and its provisional crown (Fig. 2). (You may pick a tooth that has been used in your Fixed course.) Fig. 1. FGC preparation #3 Fig. 2. Provisional crown as FGC in this exercise 2. Cement the provisional crown to the tooth using your provisional cement (Fig. 3). Fig. 3. Cement Full Crown Module: Learner Level 2 9 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • 3. With a black fine point Sharpie ® pen, draw a line along the margins of the crown restoration. The black line will be the recurrent decay for this exercise (Fig. 4). Fig. 4. Black line representing recurrent caries 4. Screw it on the space provided (Fig. 5). Fig. 5. Recurrent Decay along the margin of the FGC crown 5. With your handpiece, use tapered fissure bur to cut the crown (Fig 6). Fig. 6. Cutting the FGC crown for complete removal Full Crown Module: Learner Level 2 10 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • Clinical Relevance Crown removal is a common procedure in fixed prosthodontics. This procedure is necessary to replace the existing crown. If possible, crown should be removed without breaking it off (for possible use as provisional crown). However, because of the very adherent cements, it is cut off most of the times. There are several ways and instruments that you can use to remove the crown. These instruments are called crown removers. There are mechanical and pneumatic types. However, the most typical way is to cut the crown and removing the small pieces at a time without compromising the integrity of the tooth. 6. Remove the crown completely, and clean the tooth. Make sure you remove all the cements (Fig. 7). Fig. 7. Existing prepared tooth after FGC removal and removal of the cements 7. Re-prepare your tooth. Convert the existing FGC preparation to PFM preparation. a. The preparation for full crown on tooth #3 that has caries along the margin requires re-placement of the margin more cervically. This is done to remove caries along the margin area (Fig. 8). Fig. 8. Removal of caries along the margin area Full Crown Module: Learner Level 2 11 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • b. Margin preparation- - 1.3 mm shoulder margin on the facial - 0.5 mm chamfer margin on the lingual - 0.5 mm below the margin of gingiva - Smooth transition of chamfer and shoulder margins along the interproximal area c. Buccal Surface Reduction - Since we are to re-prepare the tooth from FGC to PFM, more buccal reduction is required to accommodate the porcelain veneering material (Fig. 9). Fig. 9. Buccal Surface Reduction. From FGC to PFM d. Lingual Surface Refinement (Fig. 10) Fig. 10. Lingual surface reduction. Full Crown Module: Learner Level 2 12 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • e. Finishing your preparation – round off sharp angles and provide a smooth finish on the tooth (Fig. 11). Fig. 11. Finished Preparation. No sharp areas. All other areas are smooth. 8. Evaluate your preparation Check your preparation. Follow the evaluation procedures you learned in the previous level. Use the evaluation criteria. At this extension, be sure to answer the question below: Are the margins located at a sound (no caries) tooth structure? Clinical Relevance It is not uncommon to see a badly decayed and badly broken down tooth upon removal of a failing full crown restoration. In this situation, the first thing you have to do is to remove all the caries. If the margins have developed caries, which is often the case, you need to re-prepare the tooth and place the margin subgingivally. The new margin therefore, should be placed on sound tooth structure to have a good marginal integrity. Full Crown Module: Learner Level 2 13 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • Full Gold Crown / Short Clinical Crown 20 1. Get typodont tooth #19. Mark a line at 3 mm above the interdental papilla (Fig. 1) Fig. 1. Marking the clinical height of the tooth at 3 mm. 2. Cut the typodont tooth at the mid level cervico-occlusally - Make sure you have 3 mm height of the tooth measured from the tip of the interdental papilla. 3. Let us assume that this is the condition of the tooth after we removed the crown (Fig. 2). Fig. 2. Simulated short clinical crown after crown removal Full Crown Module: Learner Level 2 14 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • 4. Given the short clinical tooth, prepare the tooth to receive a FGC - make the axial walls as parallel as possible and avoiding any taper to increase retention. - Place your margin subgingivally if necessary to increase the height of the axial walls. The minimum height should be at least 4.0 mm (Fig. 3). Fig. 3. Prepared tooth with 4 mm wall height preserved 5. With straight fissure carbide bur, establish your retentive groove at the buccal axial wall to increase retention (Fig. 4). Fig. 4. Placing the retentive groove to increase retention of a short clinical crown Full Crown Module: Learner Level 2 15 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry
    • 6. Finishing your preparation – round off sharp angles and provide a smooth finish on the tooth (Fig. 5). Fig. 5. FGC preparation of a short clinical crown 7. Evaluate your preparation Check your preparation. Follow the evaluation procedures you learned in the previous level. Use the evaluation criteria. Be sure to answer the question below: Do you have adequate retention and resistance to your preparation? Clinical Relevance A tooth with short clinical crown often does not give retention and resistance for your full crown restoration. Given this kind of situation, you need to establish a “good” height of axial wall. Placing the margin subgingivally increases the height of your axial wall. There should be at least 3-4mm of height in order to have adequate retention. Also, by making your axial walls parallel, this will increase the resistance form. Placement of secondary retention features like grooves, boxes and pins are also some options you can choose to increase your resistance and retention further. In summary, your margins should be placed at a sound tooth structure, never at the amalgam, composite, or build up material. Some clinical situations that you need to place your margins subgingivally are (1) if caries are involved and you have to remove it, (2) when you need to increase retention and resistance by increasing the height of your axial wall, and (3) for esthetic reason, especially on the anterior teeth when you don’t want the margins to be seen. Full Crown Module: Learner Level 2 16 Ranier M. Adarve, DMD, MS, MHPE University of Minnesota School of Dentistry