**Complete Cast Crown Preparation** **Full Gold Crown** Dr Matsubara Golden dental crown illustration on blue background # **Complete Cast Crown Preparation** ## **Full Gold Crown** Dr Matsubara **Full Gold Crown** Two dental models showing a full gold crown fitted on a molar, viewed from occlusal and buccal perspectives. **Full Gold Crown** **Advantages** ► Longevity ► Resistance ► Conservative ► Adjustability **Disadvantages** ► Aesthetics Maxillary molar Mandibular molar and premolar ### **Full Gold Crown Overview** > [!note] > A complete cast crown, particularly a full gold crown (FGC), is a durable and conservative indirect restoration. While its aesthetics are a significant drawback in modern dentistry, its mechanical properties and longevity make it an excellent choice in specific clinical situations. #### **Advantages** - Longevity : ==Full metal crowns have one of the greatest longevities of all dental restorations, demonstrating a lower annual failure rate compared to other indirect restorations (like ceramics) and direct restorations (like composites and amalgams).== - Resistance - Conservative : ==They require the least amount of tooth reduction. Gold and other metals are not brittle like porcelain; they wear down slowly over time rather than chipping. This allows for a thinner restoration, preserving more natural tooth structure.== - Adjustability - ==**Ideal for Short Clinical Crowns:** Because less occlusal reduction is needed (1.0-1.5 mm for gold vs. ~2.0 mm for ceramics), a greater amount of vertical wall height is preserved. This is crucial for achieving adequate retention and resistance form on teeth that are already clinically short, especially in the posterior region.== #### **Disadvantages** - Aesthetics : ==The primary disadvantage is the metallic appearance. Many patients prefer tooth-colored restorations and do not want visible gold or metal in their mouths.== #### **Common Applications** - Maxillary molar - Mandibular molar and premolar - ==Restoration of posterior teeth, particularly those with short clinical crowns where maximizing retention is critical.== **Full Gold Crown** **Indication** - Short clinical crowns - Maximum retention and resistance are needed - High displacement forces **Contraindication** - High esthetic need #### **Indications** - Short clinical crowns - Maximum retention and resistance are needed - High displacement forces - ==Situations requiring high strength and durability.== - ==Cases with limited occlusal clearance where more conservative reduction is necessary.== - ==Patients who are heavy bruxers, as gold wears at a rate similar to natural tooth enamel and is less likely to fracture or wear the opposing dentition.== #### **Contraindications** - High esthetic need : ==Teeth within the **Full Gold Crown** **PREPARATION CRITERIA** Two dental preparation images: left shows a tooth with a smooth, rounded preparation; right shows a tooth with a marked margin line and labeled "M" and "V" for mesial and vestibular. **Full Gold Crown** **PREPARATION CRITERIA** ► **Occlusal** - Non-functional cusp: 1.0 mm - Functional cusp: 1.5 mm ► **Axial**: 1.0 mm ► **Margin**: chamfer > 0.5 mm Diagram showing a tooth preparation with labeled dimensions: 1.0 mm, 1.5 mm, 1.0 mm, 0.5 mm, 1.0 mm, 1.5 mm ### **Preparation Criteria** > [!note] > The guidelines for a full metal crown preparation are designed to be conservative while providing adequate space for the material and ensuring the restoration's longevity. - **Occlusal** - Non-functional cusp: 1.0 mm - ==This includes the buccal cusps of maxillary teeth and the lingual cusps of mandibular teeth.== - Functional cusp: 1.5 mm - ==This includes the palatal cusps of maxillary teeth and the buccal cusps of mandibular teeth. These areas bear the most occlusal force and require greater material thickness.== - **Axial**: 1.0 mm - ==**Two planes of reduction** are necessary on the buccal and lingual surfaces to accommodate the tooth's natural contour while maintaining an ideal path of insertion.== - **Margin**: chamfer > 0.5 mm - ==A **chamfer margin** is the standard for all-metal crowns. It is a conservative margin that provides sufficient bulk for the metal without requiring the aggressive reduction of a shoulder margin used for ceramics.== **Full Gold Crown** **PREPARATION ARMAMENTARIUM** **Diamond burs** - Major reduction - Different grits **Carbide burs** - Refinement - Different roughness <table> <thead> <tr> <th>Code</th> <th>Description</th> <th>µ</th> </tr> </thead> <tbody> <tr> <td>SF</td> <td>Super Fine</td> <td>30</td> </tr> <tr> <td>F</td> <td>Fine</td> <td>50</td> </tr> <tr> <td>M</td> <td>Medium</td> <td>107-120</td> </tr> <tr> <td>C</td> <td>Coarse</td> <td>150-180</td> </tr> <tr> <td>SC</td> <td>Super Coarse</td> <td>180-250</td> </tr> </tbody> </table> ### **Preparation Armamentarium** > [!note] > The same basic set of instruments is used for most crown preparations, with variations in bur choice depending on the material and desired reduction. #### **Diamond burs** - Major reduction - Different grits - ==**Tapered and Straight Burs:** Tapered burs are commonly used to establish the correct taper for the preparation. Straight burs can be helpful for clinicians who tend to over-taper their preparations.== - ==**Coarse-Grit Burs (Green or Blue Bands):** Used for initial gross reduction of tooth structure.== - ==**Fine-Grit Burs (Red or Yellow Bands):** Used for finishing and smoothing the preparation before taking an impression.== - ==**Shaped Burs (Round, Football, Tapered Round):** Used for occlusal reduction and for rounding sharp line angles.== #### **Carbide burs** - Refinement - Different roughness - ==Tungsten carbide burs are available but are generally used less frequently for this procedure.== <table> <thead> <tr> <th>Code</th> <th>Description</th> <th>µ</th> </tr> </thead> <tbody> <tr> <td>SF</td> <td>Super Fine</td> <td>30</td> </tr> <tr> <td>F</td> <td>Fine</td> <td>50</td> </tr> <tr> <td>M</td> <td>Medium</td> <td>107-120</td> </tr> <tr> <td>C</td> <td>Coarse</td> <td>150-180</td> </tr> <tr> <td>SC</td> <td>Super Coarse</td> <td>180-250</td> </tr> </tbody> </table> #### **Other Instruments & Materials** - ==**Polishing Systems:** Sof-Lex discs or Enhance burs for final polishing.== - ==**Impression Materials:** Retraction cord, putty base and catalyst for silicone indices.== - ==**Temporary Crown Materials.**== **Full Gold Crown** **PREPARATION STEPS** 1 - Silicone putty index 2 - Occlusal reduction 3 - Buccal & lingual axial reduction 4 - Interproximal reduction 5 - Finishing 6 - Auxiliary retentive features ### **Preparation Steps** > [!note] > The preparation follows a systematic sequence to ensure all criteria are met efficiently and accurately. #### **Pre-Operative Steps** 1. ==**Anesthesia:** Administer local anesthetic. Even for endodontically treated teeth, anesthesia is often required for patient comfort during soft tissue manipulation (e.g., placing retraction cord).== 2. ==**Opposing Arch Impression:** Take an impression of the opposing arch while waiting for the anesthetic to take effect.== 1. Silicone putty index 2. Occlusal reduction 3. Buccal & lingual axial reduction 4. Interproximal reduction 5. Finishing 6. Auxiliary retentive features # Full Gold Crown ## Silicone putty index - Gives a useful guide to the original shape of the tooth once preparation has begun - Not necessary with every case - Mainly when major modifications are required - In conjunction with wax-up ### **1. Silicone Putty Index** - Gives a useful guide to the original shape of the tooth once preparation has begun - Not necessary with every case - Mainly when major modifications are required - In conjunction with wax-up - ==Two indices are recommended: 1. One is kept intact for fabricating the temporary crown. 2. The other is sectioned (e.g., buccolingually) to serve as a reduction guide, allowing for visual verification of occlusal and axial reduction throughout the preparation process.== **Full Gold Crown** **Occlusal reduction** **Ridges and grooves** - Occlusal guiding grooves - Bur: diamond (1mm diam) - Follow anatomy ### **2. Occlusal Reduction** > [!note] > This step creates the necessary space for the restorative material on the chewing surface. #### **Ridges and Grooves** - Occlusal guiding grooves - Bur: diamond (1mm diam) - Follow anatomy - ==Depth grooves are placed at the highest points (**triangular ridges**) and lowest points (**developmental grooves**) of the occlusal surface.== - ==The accuracy of these depth grooves is critical, as they guide the entire occlusal reduction. Incorrect depth or angulation will lead to an improper final reduction.== **Full Gold Crown** **Occlusal reduction** ► **Functional cusp** 1.5 mm • Buccal on mandibular posterior teeth • Lingual on maxillary posterior teeth ► **Non-functional cusp** 1.0 mm • Lingual– mandibular posterior teeth • Buccal– maxillary posterior teeth **Full Gold Crown** **Occlusal reduction** ► **Functional cusp** 1.5 mm • Buccal on mandibular posterior teeth • Lingual on maxillary posterior teeth ► **Non-functional cusp** 1.0 mm • Lingual– mandibular posterior teeth • Buccal– maxillary posterior teeth #### **Reduction Amounts** - **Functional cusp**: 1.5 mm - Buccal on mandibular posterior teeth - Lingual on maxillary posterior teeth - **Non-functional cusp**: 1.0 mm - Lingual– mandibular posterior teeth - Buccal– maxillary posterior teeth - ==It is advisable to prepare to approximately 80% of the final depth (e.g., 0.8 mm for a 1.0 mm reduction) during the gross reduction phase, leaving the final 0.2 mm for the finishing step.== # Full Gold Crown ## Occlusal reduction - Even occlusal surface reduction - Bur (1mm diameter) - Reduce half the occlusal surface - Use the other half as a guide - Check the occlusal reduction (Putty key and antagonist) - Centric and excursive movements #### **Procedure** - Even occlusal surface reduction - Bur (1mm diameter) - Reduce half the occlusal surface - Use the other half as a guide - Check the occlusal reduction (Putty key and antagonist) - Centric and excursive movements > [!example] Alternate Procedure > 1. **Optional Central Fossae Holes:** Place 1.0 mm deep holes in the central, mesial, and distal fossae. This can help guide reduction but may be skipped if it tends to cause over-reduction. > 2. **Place Depth Grooves:** Use a bur to create depth grooves on the triangular ridges and developmental grooves to the required depths (1.5 mm on functional cusps, 1.0 mm on non-functional). > 3. **Connect the Grooves:** Reduce the remaining occlusal surface by connecting the depth grooves, following the natural anatomy of the cusps and fossae. > 4. **Adjust Bur Angulation:** Be mindful that the bur will not sit flat on all inclines. Adjust the handpiece angulation to ensure uniform reduction across the entire surface. **Full Gold Crown** Occlusal reduction Two images of a tooth model showing occlusal reduction with red markings indicating areas to be reduced. **Full Gold Crown** **Occlusal reduction** *Following the occlusal anatomy* Three dental models showing occlusal reduction with red markings indicating preparation lines. *Following the occlusal anatomy* **Full Gold Crown** **Lingual reduction** 2 planes of reduction **Supporting cusp** 1.5 mm **Occlusal third** ### **3. Axial Reduction** > [!warning] Path of Insertion > The path of insertion should be parallel to the long axis of the tooth, not the clinical crown, which may be tilted (e.g., the lingual tilt of mandibular molars). #### **Lingual Reduction (2 Planes of Reduction)** - ==Place depth grooves (the lecturer suggests starting with five for stability, rather than the textbook's three) to guide the reduction.== - ==Connect the grooves, establishing two distinct planes to avoid under-reduction in the occlusal third or over-tapering the preparation.== - **Occlusal Third (Supporting Cusp)** - Reduction: 1.5 mm **Full Gold Crown** **Lingual reduction** - 2 planes of reduction - Gingival 2/3 - Axial reduction 1.0 mm - Margin 0.5 mm - 1.5 mm - 1 mm - Parallel to long axis Diagram showing lingual reduction with labeled measurements: 2 planes of reduction, axial reduction 1.0 mm, margin 0.5 mm, gingival 2/3, 1.5 mm, 1 mm, parallel to long axis. - **Gingival 2/3** - Axial reduction: 1.0 mm - Margin: 0.5 mm - Parallel to long axis **Full Gold Crown** **Lingual reduction** 2 planes of reduction - Even axial surface reductions - Margin placement in the same procedure - **General Principles** - Even axial surface reductions - Margin placement in the same procedure **Full Gold Crown** **Lingual reduction** 2 planes of reduction Diagram showing two views of a tooth preparation for a full gold crown, highlighting 3° angulation on the lingual surface. **Full Gold Crown** **Lingual reduction** 2 planes of reduction Diagram showing two views of a tooth preparation for a full gold crown, illustrating lingual reduction with two planes. **Full Gold Crown** **Lingual reduction** 2 planes of reduction Two images showing a tooth preparation for a full gold crown, highlighting the lingual reduction with red lines indicating the two planes of reduction. **Full Gold Crown** **Buccal reduction** 2 planes of reduction **Occlusal 2/3** **Non supporting cusp** Reduction 1.0 mm #### **Buccal Reduction (2 Planes of Reduction)** > [!info] Purpose of Two Planes > - The **gingival two-thirds** of the axial wall should be prepared nearly parallel to the long axis of the tooth to maximize retention and resistance. > - The **occlusal one-third** is prepared with a second, more angled plane. This follows the natural contour of the tooth, ensuring adequate material thickness without creating an excessive taper that would compromise retention. > [!example] Procedure > 1. Place several vertical depth grooves along the buccal surface. > 2. Connect the grooves, creating the two planes of reduction. - **Occlusal 2/3 (Non-supporting Cusp)** - Reduction: 1.0 mm **Full Gold Crown** **Buccal reduction** 2 planes of reduction Reduction 1.0 mm Gingival 1/3 Parallel to the long axis - **Gingival 1/3** - Reduction: 1.0 mm - Parallel to the long axis **Full Gold Crown** Two images of a dental crown model, one showing the top view and the other a side view with a 3° angle marked on the margin. **Full Gold Crown** **Interproximal reduction** Extra care for the interproximal areas / adjacent tooth - Use narrow tapered bur - Use needle bur - Matrix band protection if needed - Acquired skill ### **4. Interproximal Reduction** - Extra care for the interproximal areas / adjacent tooth - Use narrow tapered bur - Use needle bur - Matrix band protection if needed - Acquired skill #### **Procedure** 1. ==Extend the buccal and lingual axial reductions as far into the interproximal embrasures as possible without touching the adjacent tooth.== 2. ==To safely break contact, it is recommended to **favor occlusal reduction** when cutting through the marginal ridge. This approach increases visibility of the bur tip and the contact area, minimizing the risk of damaging the adjacent tooth.== 3. ==Follow the natural curvature of the tooth interproximally; do not cut a flat slice.== **Full Gold Crown** **Interproximal reduction** Diagram showing interproximal reduction on a dental model with a burr tool. **Full Gold Crown** Four images of a tooth model with a full gold crown, labeled P, M, V, and D, likely indicating different anatomical views (Palatal, Mesial, Vestibular, Distal). **Full Gold Crown** **Finishing** - Smooth preparation - Smooth transition between surfaces - No sharp angles - Fine-grit diamond or carbide bur - Consider low speed hand piece - Assessing criteria with dental explorer or periodontal probe ### **Evaluation of the Preparation** > [!success] Final Check > A final, systematic check is crucial before proceeding to the impression stage. - ==**Occlusal Clearance:** Use the sectioned putty index to verify that adequate clearance (1.0-1.5 mm) has been achieved across the entire occlusal surface.== - ==**Taper and Path of Insertion:**== - ==View the preparation from the buccal and lingual aspects to evaluate the **mesio-distal taper**.== - ==View from the mesial and distal aspects (using a mirror) to evaluate the **bucco-lingual taper**.== - ==**Occlusal View (Concentricity and Undercuts):**== - ==**Undercuts:** When viewing from directly above, all parts of the margin must be visible. If any portion of the margin is hidden by a bulge of tooth structure, an undercut is present.== - ==**Over-tapering:** You should see only a small, uniform amount of the axial wall. If a large amount of the axial wall is visible, the preparation is likely over-tapered.== - ==**Margin Quality:** Use an explorer to confirm the margin is smooth, continuous, and free of ledges.== ### **5. Finishing** > [!note] > The goal is to create a smooth preparation free of sharp angles, which act as points of stress concentration. - Smooth preparation - Smooth transition between surfaces - No sharp angles - Fine-grit diamond or carbide bur - Consider low speed hand piece - Assessing criteria with dental explorer or periodontal probe - ==**Round all line angles**, creating a smooth transition between the occlusal, axial, and interproximal surfaces. The final prep should have no # Full Gold Crown ## Auxiliary Retentive Features - Vertical grooves or boxes - 1 mm deep - 1 mm above the margin - In the middle of the buccal surface - Restricting the path of withdrawal - As parallel to the long axis of the tooth as possible Diagram of a full gold crown showing labeled features: Functional cusp bevel (Structural durability), Seating groove (Retention and resistance), Axial reduction (Retention and resistance). ### **6. Auxiliary Retentive Features** > [!note] > These are features added to the preparation to increase retention and resistance form, typically only when necessary (e.g., on very short clinical crowns). - Vertical grooves or boxes - 1 mm deep - 1 mm above the margin - In the middle of the buccal surface - Restricting the path of withdrawal - As parallel to the long axis of the tooth as possible - ==**Types:** Vertical grooves or boxes.== - ==**Mechanism:** They enhance retention by limiting the path of insertion to a single direction, creating resistance to dislodgement.== - ==**Critical Consideration:** Auxiliary features **must be prepared parallel to the path of insertion** of the crown. If they are divergent, the crown will not seat. The lab would be forced to block out the feature, rendering it useless.== - ==**Modern Relevance:** With the advent of modern adhesive cements and refined preparation techniques, auxiliary features are needed less frequently than in the past but remain a useful tool in challenging cases.== [[F1 Metal Crowns.pdf#page=1|F1 Metal Crowns, p.1]] [[F1 Metal Crowns.pdf#page=2|F1 Metal Crowns, p.2]] [[F1 Metal Crowns.pdf#page=3|F1 Metal Crowns, p.3]] [[F1 Metal Crowns.pdf#page=4|F1 Metal Crowns, p.4]] [[F1 Metal Crowns.pdf#page=5|F1 Metal Crowns, p.5]] [[F1 Metal Crowns.pdf#page=6|F1 Metal Crowns, p.6]] [[F1 Metal Crowns.pdf#page=7|F1 Metal Crowns, p.7]] [[F1 Metal Crowns.pdf#page=8|F1 Metal Crowns, p.8]] [[F1 Metal Crowns.pdf#page=9|F1 Metal Crowns, p.9]] [[F1 Metal Crowns.pdf#page=10|F1 Metal Crowns, p.10]] [[F1 Metal Crowns.pdf#page=11|F1 Metal Crowns, p.11]] [[F1 Metal Crowns.pdf#page=12|F1 Metal Crowns, p.12]] [[F1 Metal Crowns.pdf#page=13|F1 Metal Crowns, p.13]] [[F1 Metal Crowns.pdf#page=14|F1 Metal Crowns, p.14]] [[F1 Metal Crowns.pdf#page=15|F1 Metal Crowns, p.15]] [[F1 Metal Crowns.pdf#page=16|F1 Metal Crowns, p.16]] [[F1 Metal Crowns.pdf#page=17|F1 Metal Crowns, p.17]] [[F1 Metal Crowns.pdf#page=18|F1 Metal Crowns, p.18]] [[F1 Metal Crowns.pdf#page=19|F1 Metal Crowns, p.19]] [[F1 Metal Crowns.pdf#page=20|F1 Metal Crowns, p.20]] [[F1 Metal Crowns.pdf#page=21|F1 Metal Crowns, p.21]] [[F1 Metal Crowns.pdf#page=22|F1 Metal Crowns, p.22]] [[F1 Metal Crowns.pdf#page=23|F1 Metal Crowns, p.23]] [[F1 Metal Crowns.pdf#page=24|F1 Metal Crowns, p.24]] [[F1 Metal Crowns.pdf#page=25|F1 Metal Crowns, p.25]] [[F1 Metal Crowns.pdf#page=26|F1 Metal Crowns, p.26]] [[F1 Metal Crowns.pdf#page=27|F1 Metal Crowns, p.27]] [[F1 Metal Crowns.pdf#page=28|F1 Metal Crowns, p.28]] [[F1 Metal Crowns.pdf#page=29|F1 Metal Crowns, p.29]]