Creating zirconia (ZR) crowns using CAD
(Computer-Aided Design) involves a series of precise steps in a digital
dental laboratory. Here's an overview of the process:
- 1. Patient Preparation and Digital Impressions
- Digital Scanning:
Start with capturing a detailed digital impression of the patient's
teeth using an intraoral/ Exocad scanner. This step replaces traditional
physical impressions with a digital model, providing precise data of the
tooth preparation and adjacent teeth.
- 2. CAD Design
- Design Software:
Import the digital impression into CAD software such as Exocad, The
software allows for detailed design of the crown.
- Tooth Preparation:
Define the margins and contours of the prepared tooth in the software.
This involves outlining the boundaries of the tooth preparation to
ensure the crown will fit precisely.
- Crown Design:
Design the zirconia crown using the software tools. The software enables
adjustments for occlusion, contact points, and aesthetics. Key features
include:
- 1. Occlusion Adjustment: Ensuring the crown fits correctly
with opposing teeth.
- 2. Margin Design: Defining the margins of the crown for a
perfect fit.
- 3. Anatomical Features: Designing cusps, grooves, and other
features for natural appearance and function.
- 3. CAM (Computer-Aided Manufacturing)
- Milling: Once
the design is finalized, it is sent to a milling machine. The CAD file
directs the machine to mill the crown from a solid block of zirconia.
This step involves:
- Block Selection:
Choosing a zirconia block that matches the desired shade and size.
- Milling Process:
The milling machine carves out the crown according to the CAD design.
- 4. Post-Processing
- Sintering: The
milled zirconia crown is then placed in a sintering furnace. Sintering
involves heating the crown to high temperatures to achieve its final
strength and translucency. This process typically takes several hours.
- Staining and
Glazing: After sintering, the crown may be stained and glazed to
match the color of the surrounding teeth and achieve a natural
appearance. This step involves applying ceramic stains and firing the
crown in a furnace to achieve the desired color and luster.
- 5. Quality Check and Adjustment
- Fit Check: The
final crown is checked for fit and occlusion. Any necessary adjustments
are made to ensure that the crown fits perfectly in the patient's mouth.
- Polishing: The
crown is polished to smooth the surface and enhance its appearance.
- 6. Delivery
- Fitting: The
completed zirconia crown is then delivered to the dental practice. The
dentist will place and adjust the crown on the patient's tooth, ensuring
it fits well and functions correctly.
- Key Considerations
- Accuracy: The
precision of digital impressions and CAD design is crucial for a
well-fitting crown. Ensure the scanner and software used are up-to-date
and well-calibrated.
- Material Quality:
High-quality zirconia blocks contribute to the durability and aesthetics
of the final crown.
- Training: Proper
training in CAD software and milling equipment is essential for
producing high-quality crowns.
