Step-by-Step Guide: Preparing a Tooth for a Zirconia Crown on a Manikin

Ensure sufficient room for the wall thickness to have a minimum of 0.5 mm and ideally between 1 mm and 1.5 mm or 1.5 to 2 mm occlusal reduction.

On a hot summer day of June 2018 I was writing my Assessment Of Clinical Skills ( currently NDECC). We were allowed to use instruments and materials of our choice, as opposed to the current situation. I had a bur that was my favourite to finish my PFM preparation. Unfortunately, I misplaced it somewhere in my kit. My only help was now my friend who was also in the same section of University Of Alberta challenging the same exam.

I requested the invigilator that came through my line of sight, "Doctor, could I please borrow an instrument from my friend?. She is in 6th Operatory down the aisle."

It was as if the invigilator was waiting for this moment, and did not hesitated to ask, "what would you do if this was a real life situation".

I responded with my understanding of 'infection control', and how we need to verify before re-using a diamond bur. If it's intended for single use, it has to be discarded after the procedure. Simply saying, " I could not use it".

After teaching students over the years, how to prepare teeth for different types of crowns, I realized that we don't need a whole lot of equipment to perform this task.

Once the ecstasy of passing ACJ or ADC Written Exam is over, one starts to think about preparing for NDECC or ADC Practical Exam. This is the moment where the importance of minute details draws our attention. Even the fraction of millimetre could make a huge difference to the expected outcome.

Here are some of the general guidelines:

Materials Needed:

1. Dental manikin with teeth

2. Dental handpiece

3. Water spray

4. Air syringe

5. High-speed diamond bur ( Premier 770.8 or similar )

6. Slow-speed diamond bur ( Finishing )

7. Gingival retraction cord (optional)

8. Dental explorer

9. Clearance tab

Step 1: Set up the Manikin

1. Position the dental manikin in an ergonomic working position.

2. Ensure the teeth to be prepared for the zirconia crown are easily accessible.

Step 2: Tooth Evaluation

1. Inspect the tooth to be prepared for any decay, fractures, or existing restorations.

2. Assess the occlusion and determine the appropriate reduction needed for the zirconia crown.

3. Verify the amount of clearance required for the crown, considering the material thickness and esthetic requirements.

Step 3: Anesthetize the Manikin ( not always part of simulation)

1. Apply a topical anesthetic gel or spray on the gums to simulate local anesthesia.

Step 4: Tooth Preparation

1. Begin by using the high-speed diamond bur in a water spray to create initial occlusal reduction. Aim for about 1.5 to 2 mm of reduction.

2. Assess the reduction visually and with an explorer, ensuring that all caries or defective enamel have been removed.

3. Use the high-speed diamond bur to establish axial wall reduction. Aim for 1 to 1.5 mm of circumferential reduction and 1.5 to 2 mm of occlusal reduction.

4. Maintain a slight taper of 4 to 8 degrees to facilitate crown seating and retention.

5. Round the line angles and create smooth margins.

6. Adjust the proximal contacts, if necessary, to allow for proper seating of the crown.

7. Polish the prepared tooth surfaces using a slow-speed diamond bur to achieve a smooth finish.

8. Rinse the tooth and manikin thoroughly to remove debris.

Step 5: Gingival Retraction (Optional)

1. If needed, place a gingival retraction cord gently along the gingival margin to displace the tissue and improve visibility.

2. Ensure that the cord does not interfere with margin placement.

Step 6: Occlusal Adjustment:

1. Use a clearance bite tab to check the occlusion of the prepared tooth with opposing teeth.

2. Adjust the occlusion by selectively reducing high spots on the prepared tooth until proper occlusal harmony is achieved.

Step 7: Final Evaluation

1. Inspect the prepared tooth for any irregularities, undercuts, or over-reduction.

2. Verify occlusion clearance and adjust if necessary.

Note: This guide provides a general overview of the steps involved in preparing a tooth for a zirconia crown on a manikin. The specific techniques and procedures may vary depending on the individual case and dental training.

The above instructions are for educational purposes only and should not replace professional dental training or guidance. It's crucial to consult with a qualified dentist or dental instructor before attempting any dental procedures.