Mastering IPS e.max CAD Block Selection: A Dentist's Guide to Shade Matching and Strength Requirements

After milling hundreds of IPS e.max CAD restorations over the years, I've learned that block selection can make or break your final result. It's not just about grabbing the closest shade and hoping for the best—there's a systematic approach that'll give you predictable, beautiful outcomes every time.

Let's dive into the practical aspects of selecting the right IPS e.max CAD block for your CEREC cases, from understanding translucency levels to matching strength requirements.

Understanding IPS e.max CAD Translucency Levels

IPS e.max CAD blocks come in four distinct translucency levels, and choosing the right one is crucial for achieving natural-looking restorations:

HT (High Translucency)

These are your go-to blocks for anterior esthetics. HT blocks offer excellent light transmission, making them ideal for veneers, inlays, and anterior crowns where you want maximum vitality. The high translucency allows underlying tooth structure to show through, creating depth and natural color variation.

Best for: Veneers, anterior crowns, inlays where esthetics are paramount

LT (Low Translucency)

LT blocks provide better masking ability while maintaining good esthetics. They're perfect when you need to hide discolored tooth structure or metal posts. I reach for LT blocks when dealing with darker preparations or when I need more opacity without sacrificing too much translucency.

Best for: Crowns over discolored teeth, cases with metal posts, posterior crowns where some masking is needed

MO (Medium Opacity)

MO blocks offer significant masking power while still allowing some light transmission. These work well for posterior crowns and when you need to block out severely discolored tooth structure. They're also my choice for implant crowns where you need to mask the abutment.

Best for: Implant crowns, severely discolored preparations, posterior restorations requiring masking

MT (Medium Translucency)

MT blocks strike a balance between translucency and opacity. They're versatile options for cases where you need moderate masking with reasonable esthetics. I use these for transitional areas and when I'm unsure whether to go with LT or MO.

Best for: Premolar crowns, cases requiring moderate masking, versatile applications

Shade Selection Strategy

Here's where many dentists get tripped up. The block shade you select doesn't need to perfectly match your final desired shade—it needs to be your starting point for achieving that shade through staining and glazing.

The Foundation Approach

Think of your block selection as choosing a foundation color. Select the block shade that's closest to your target shade, then use the staining and glazing process to fine-tune the final result.

For example, if you're targeting an A2 final shade:

• Select an A2 HT block as your starting point
• Use wash firing to adjust brightness
• Apply stains to modify chroma and hue
• Final glaze to achieve desired surface characteristics

Available Shade Options

IPS e.max CAD blocks are available in:

• Classical shades: A1-A4, B1-B4, C1-C4, D2-D4
• Bleach shades: BL1-BL4 for lighter cases
• Impulse shades: Specialized shades for specific esthetic requirements

Practical Shade Matching Tips

When in doubt, I follow these guidelines:

• For most cases, stay within the A shade family—it's the most versatile
• Use BL shades for younger patients or heavily bleached teeth
• B shades work well for cases requiring more yellow undertones
• C and D shades are useful for specific color matching challenges

Block Size Selection

Choosing the right block size prevents waste and ensures you have enough material for your restoration:

I12 Blocks

Perfect for inlays, onlays, and small restorations. These smaller blocks are cost-effective for conservative restorations and minimize material waste.

C14 and C16 Blocks

Your standard crown blocks. C14 works for most single crowns, while C16 gives you extra material for larger restorations or when you need more flexibility in positioning.

B32 and B40 Blocks

These larger blocks are designed for bridges and multiple-unit restorations. The B40 is particularly useful for longer span bridges or when you need maximum material availability.

A14 and A16 Blocks

Specialized for hybrid abutments and implant restorations. These blocks are designed with specific dimensions for abutment fabrication.

Strength Requirements and Clinical Applications

With a flexural strength of 530 MPa after crystallization, IPS e.max CAD blocks are strong enough for most clinical applications, but understanding the limits is important.

Excellent Applications

• Single crowns (anterior and posterior)
• Inlays and onlays
• Veneers
• Three-unit bridges (anterior to second premolar)
• Implant crowns

Consider Alternatives For

• Long-span posterior bridges
• Bridges involving molars as abutments
• Cases with heavy bruxism (consider zirconia)
• Implant bridges with long cantilevers

Milling and Crystallization Considerations

IPS e.max CAD blocks are milled in their blue, pre-crystallized state, which offers several advantages:

• Minimal tool wear: The softer pre-crystallized state is easier on your burs
• Easy adjustments: You can make modifications before crystallization
• Predictable shrinkage: The CAD software compensates for crystallization shrinkage

Crystallization Protocol

The standard crystallization firing takes about 25 minutes total (including heat-up time) in a Programat furnace. This transforms the blue block into its final strength and translucency.

Clinical Success Rates

The numbers speak for themselves: IPS e.max CAD restorations show a 95.2% survival rate over up to 15 years, with 95% receiving excellent ratings at 5-year recalls. In my experience, these high success rates are achievable when you:

• Select appropriate cases (don't push the material beyond its limits)
• Follow proper preparation guidelines
• Use appropriate cementation protocols
• Ensure proper occlusal adjustment

Common Block Selection Mistakes

Over the years, I've seen several recurring mistakes that can compromise results:

Over-Relying on Staining

Don't select a block that's dramatically different from your target shade and expect staining to bridge the gap. Start as close as possible to your final shade.

Wrong Translucency Level

Using HT blocks when you need masking power, or MO blocks when you want maximum esthetics. Match the translucency to your clinical situation.

Undersized Blocks

Choosing blocks that are too small and running out of material during milling. When in doubt, go up a size.

Ignoring Strength Requirements

Using e.max for applications where zirconia would be more appropriate, particularly in heavy-load situations.

Integration with CEREC Workflow

IPS e.max CAD blocks integrate seamlessly with CEREC systems. The material database includes all the necessary parameters for milling, and the software automatically compensates for crystallization shrinkage.

When setting up your case in CEREC Software:

• Select the correct material type and shade
• Verify the block size matches your selection
• Check that wall thickness meets minimum requirements (0.5mm for veneers, 1.0mm for crowns)
• Review the milling preview to ensure adequate material

Frequently Asked Questions

Can I use HT blocks for posterior crowns?

Yes, but consider the clinical situation. HT blocks work well for posterior crowns when esthetics are important and you don't need significant masking power. For heavily discolored preparations or when maximum strength is needed, LT or MO blocks might be better choices.

How do I choose between C14 and C16 blocks for single crowns?

C14 blocks are sufficient for most single crowns and are more cost-effective. Choose C16 when you're restoring larger teeth, need extra material for complex anatomy, or want more flexibility in block positioning during milling.

What's the difference between BL and A1 shades?

BL (Bleach) shades are designed for lighter, more translucent cases, while A1 has slightly more chroma and body. BL shades work better for younger patients or heavily bleached teeth, while A1 is more versatile for general use.

Can I mill bridges from single crown blocks?

For three-unit anterior bridges, you might get away with a C16 block, but it's not ideal. B32 or B40 blocks are specifically designed for bridges and provide better material utilization and positioning options.

How long can I store milled restorations before crystallization?

Milled IPS e.max CAD restorations in the blue state can be stored indefinitely in a dry environment. However, I recommend crystallizing within a few days to avoid any risk of damage or contamination to the delicate pre-crystallized structure.

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