CEREC Explained: How Your Dentist Makes a Crown in One Visit

The first time I watched a CEREC crown emerge from the milling unit, I'll admit I was skeptical. How could this machine possibly match the precision of a lab-fabricated crown? Fast forward fifteen years, and I can't imagine practicing without chairside CAD/CAM. But the magic isn't really in the machine—it's in understanding the workflow and executing each step with precision.

If you're considering CEREC or looking to refine your same-day crown technique, let's walk through the complete process. I'll share the real-world details that make the difference between a crown that lasts two years and one that's still solid after fifteen.

The Foundation: Preparation Considerations

Your prep work for CEREC crowns needs to be more deliberate than traditional impressions. The scanner sees everything—and I mean everything. That slight undercut you might get away with in a PVS impression? The scanner captures it perfectly, and your crown won't seat.

I've found success with these preparation guidelines:

• Shoulder or heavy chamfer margins: 1.0-1.2mm minimum, with the shoulder being my preference for posterior teeth
• 6-degree taper: More conservative than traditional preps, but necessary for predictable seating
• Occlusal reduction: 1.5-2.0mm, depending on material choice
• Clean, defined margins: Use a fine diamond for final margin refinement

The key difference from conventional preps is margin clarity. Spend the extra two minutes with your finishing bur. Your scanner—and your crown fit—will thank you.

Digital Impression: Beyond Point-and-Shoot

This is where many practitioners stumble. A digital impression isn't just about waving the scanner around the tooth. The quality of your scan directly impacts everything downstream.

Scanning Sequence That Works

I use this sequence for every crown scan:

1. Opposing arch first: Establishes your occlusal reference
2. Buccal approach on prep tooth: Capture the margin from the facial
3. Occlusal surface: Multiple overlapping passes
4. Lingual approach: Don't rush this—lingual margins are critical
5. Full arch completion: Ensure adequate proximal contact data
6. Bite registration: Light contact, capture the prep area clearly

Common Scanning Pitfalls

After reviewing thousands of scans, these issues pop up repeatedly:

• Inadequate retraction: If you can't see the margin clinically, the scanner can't either
• Moisture control: Saliva pooling creates scan artifacts that translate to poor margins
• Moving too fast: Slow, deliberate passes with 50% overlap
• Insufficient proximal data: Those contact areas matter more than you think

I keep a 10x loupe at my CEREC station. If the scan margin looks questionable under magnification, it probably is. Rescan that area.

Design Phase: Where Art Meets Science

The CEREC software has become remarkably sophisticated, but it's still just following your instructions. The design phase is where your clinical judgment matters most.

Biocopy vs. Biogeneric Design

For intact contralateral teeth, biocopy is fantastic. The software captures the anatomy of the opposite tooth and mirrors it. But here's what I've learned: biocopy works best when the reference tooth has ideal anatomy. If your patient's contralateral molar has a flat, worn occlusal surface, don't copy that.

Biogeneric design gives you more control. I use it for:

• Patients with significant wear patterns
• When the contralateral tooth has large restorations
• Cases where I want to modify the occlusal scheme

Critical Design Parameters

Margin placement: The software's automatic margin detection is good, but not perfect. I manually adjust margins on every case. Look for:

• Continuous, smooth margin lines
• Adequate cement space (80-100 microns)
• No margin gaps or overlaps

Proximal contacts: This is where many chairside crowns fail long-term. Tight contacts prevent food impaction and maintain arch stability. I aim for contacts that require moderate floss pressure—not so tight that floss shreds, but definitely not loose.

Occlusal anatomy: Less is often more. I design crowns with slightly reduced cusp height initially. It's easier to add anatomy than remove it, and you can always adjust after try-in.

Material Selection: Matching Properties to Function

Block selection isn't just about shade matching. Each material has specific indications, and choosing wrong can lead to early failure.

Lithium Disilicate (e.max CAD)

My go-to for single crowns, especially anteriors and premolars. Strengths include excellent esthetics and proven longevity. The crystallization firing step is non-negotiable—skip it and you'll see fractures within months.

Preparation requirements: 1.5mm minimum occlusal reduction, 1.0mm axial

Cementation: Adhesive bonding required for optimal strength

Zirconia

For posterior crowns on heavy bruxers or when crown height is limited. Modern zirconia blocks have improved translucency, but they're still not my first choice for anterior esthetics.

Advantages: High strength, conservative prep requirements

Limitations: More difficult to adjust, requires specific burs

Resin Nanoceramic (Lava Ultimate)

Excellent for conservative restorations and easy adjustability. The machinability is fantastic, and chairside repairs are possible.

Best applications: Moderate stress areas, patients who prefer conservative treatment

Cementation: Conventional or adhesive protocols work

Milling: Precision in Motion

The milling process is largely automated, but understanding the parameters helps troubleshoot issues.

Bur Selection and Maintenance

I replace step burs every 20-25 crowns for lithium disilicate, regardless of appearance. Dull burs create chipping and poor surface finish. For zirconia, bur life extends to 40-50 restorations.

Keep a milling log. Track bur usage, material types, and any quality issues. Patterns emerge quickly.

Quality Control During Milling

Don't walk away during milling. I check progress at the halfway point, looking for:

• Proper block positioning
• Adequate material thickness
• Clean margin definition

If something looks off, stop the mill. It's better to start over than deliver a compromised restoration.

Finishing and Characterization

Fresh from the mill, your crown needs refinement. This step separates good CEREC crowns from great ones.

Surface Finishing Protocol

1. Margin refinement: Fine diamond burs to smooth any milling artifacts
2. Occlusal adjustment: Start conservatively—you can always remove more
3. Proximal contact adjustment: Use thin finishing strips, not burs
4. Surface polishing: Progressive grits from 220 to 1200

Characterization Options

For anterior crowns, surface staining can dramatically improve esthetics. I use a simple stain kit with basic brown and orange shades. Less is more—subtle characterization looks natural.

The firing cycle adds 15 minutes but transforms a monochromatic crown into something that blends seamlessly.

Try-in and Cementation

This final step determines long-term success. Rush it, and you'll see the patient back with problems.

Systematic Try-in Process

1. Dry try-in first: Check seating, margins, and contacts
2. Radiographic verification: Confirm complete seating
3. Occlusal evaluation: Light contacts in centric, smooth excursions
4. Patient approval: Esthetics and comfort

Cementation Protocol

For lithium disilicate crowns, I use adhesive cementation exclusively. The bond strength nearly doubles compared to conventional cement.

Surface preparation:

• Hydrofluoric acid etch (20 seconds for e.max)
• Silane coupling agent application
• Adhesive resin coating

Tooth preparation:

• Phosphoric acid etch (15 seconds)
• Bonding agent application
• Light cure before crown placement

Take your time with cleanup. Excess cement removal is easier when the material is in the gel phase—about 2-3 seconds of light curing, then clean up with floss and instruments.

Troubleshooting Common Issues

Crown Won't Seat

Usually a scanning or design issue. Check for:

• Undercuts in the preparation
• Margin discrepancies
• Excessive cement space settings

Poor Proximal Contacts

Often related to inadequate scan data. Ensure you're capturing enough information about adjacent teeth during scanning.

Occlusal Interference

Design crowns slightly under-contoured initially. It's much easier to add material than remove it chairside.

Frequently Asked Questions

How long does the entire CEREC process take?

From preparation to final cementation, plan on 90-120 minutes for a single crown. This includes scanning (15 minutes), design (10 minutes), milling (15 minutes), and finishing/cementation (30-45 minutes). The remaining time is for preparation and patient management.

Can CEREC crowns match the quality of lab-made restorations?

For single crowns, absolutely. The precision is comparable, and the convenience factor is significant for both patient and practice. However, complex multi-unit cases or highly esthetic anterior work may still benefit from lab collaboration, especially when extensive characterization is needed.

What's the learning curve like for new CEREC users?

Expect 20-30 cases before you feel comfortable with the workflow. The first 10 cases will take longer than traditional impressions, but efficiency improves rapidly. Focus on scanning technique first—everything else builds from a quality digital impression.

How do CEREC crowns hold up long-term?

Clinical studies show 10-year survival rates of 90-95% for CEREC crowns, comparable to conventional restorations. The key factors are proper case selection, adequate preparation, and adhesive cementation when indicated. Material choice also matters—lithium disilicate has the longest track record.

What cases should I still send to the lab?

I still use the lab for complex esthetic cases requiring extensive layering, multi-unit bridges over three units, and cases where the patient prefers multiple try-in appointments. CEREC excels at single crowns and simple bridges, but knowing when to collaborate with your lab technician is part of providing optimal care.

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