CEREC Tessera: Mastering Advanced Ceramics for Posterior Restorations

The introduction of CEREC Tessera advanced ceramics has given us a game-changing material for posterior restorations. After working with Tessera for the past two years in my practice, I've developed specific protocols that consistently deliver excellent clinical outcomes. Let me share what I've learned about maximizing this material's potential.

Understanding Tessera's Unique Properties

Tessera isn't just another ceramic block. It's a lithium disilicate-based material with enhanced crystalline structure that provides exceptional strength (500+ MPa flexural strength) while maintaining excellent esthetics. What sets it apart is the fine grain structure that allows for predictable milling of thin sections without chipping.

The key difference I've noticed compared to traditional lithium disilicate is Tessera's improved machinability. You can mill thinner margins and more delicate anatomy without the edge chipping that sometimes plagued earlier materials. This translates to more conservative preparations and better marginal integrity.

Preparation Protocols for Tessera Posteriors

Occlusal Reduction Guidelines

For Tessera posterior crowns, I maintain a minimum 1.5mm occlusal reduction in functional areas and 1.0mm in non-functional cusps. This might seem conservative, but Tessera's strength allows us to work with these dimensions confidently.

The critical factor is creating smooth, flowing reduction patterns. Avoid sharp internal line angles that can create stress concentrations. I use a football-shaped diamond bur for initial reduction, followed by a round-end taper for smoothing transitions.

Margin Design Considerations

Tessera works beautifully with both chamfer and shoulder margins. I prefer a 1.0mm chamfer for most cases, but you can go as thin as 0.8mm in esthetic zones where the margin is supragingival. The material's improved edge strength handles these thinner margins without issues.

One technique tip: keep your margins smooth and avoid any undercuts. Tessera mills cleanly, but any preparation irregularities will be faithfully reproduced in the restoration.

CEREC Software Settings and Design Strategies

Material Selection in CEREC Software

Always select “Tessera” specifically in your material dropdown, not generic lithium disilicate. The software has optimized milling parameters for Tessera that differ from other ceramics. This includes adjusted feed rates and cutting strategies that minimize stress during fabrication.

Design Parameters

When designing Tessera restorations, I typically set minimum thickness parameters to:

• Occlusal surfaces: 1.5mm minimum
• Axial walls: 0.8mm minimum
• Margins: 0.6mm minimum (software will usually go slightly thicker)

The biogeneric design tools work exceptionally well with Tessera. The material's strength allows you to create more anatomically correct occlusal morphology without fear of fracture.

Connector Design for Bridges

For three-unit bridges, maintain connector dimensions of at least 4mm height × 3mm width. Tessera's strength is impressive, but proper connector design remains critical for long-term success. I've had excellent results with three-unit bridges following these guidelines.

Milling Protocols and Quality Control

Block Selection and Orientation

Tessera blocks have consistent properties throughout, so orientation is less critical than with some materials. However, I still orient crowns with the occlusal surface toward the top of the block when possible. This minimizes the number of direction changes during milling.

Always inspect your blocks before milling. Look for any visible cracks or defects. Tessera blocks are remarkably consistent, but quality control starts with proper block inspection.

Milling Parameters

The CEREC system automatically adjusts milling parameters when you select Tessera, but understanding what's happening helps troubleshoot issues:

• Roughing passes use higher feed rates than traditional ceramics
• Finishing passes are slower with smaller step-overs for superior surface quality
• The system uses specific tool paths that minimize stress concentration

If you notice any chipping during milling, check your bur condition first. Tessera is harder than feldspathic ceramics and will dull burs more quickly.

Post-Milling Inspection

After milling, inspect margins under magnification. Tessera typically mills with clean, sharp margins, but any chips or irregularities need addressing before firing. I use a fine diamond bur for any minor adjustments, always working wet to prevent heat damage.

Crystallization and Finishing Protocols

Crystallization Firing

Tessera requires crystallization firing to achieve full strength. The firing cycle is similar to other lithium disilicates but has specific parameters:

• Standby temperature: 403°C
• Closing time: 6 minutes
• Heat rate: 90°C/minute to 840°C
• Hold time: 7 minutes
• Long-term cooling to 700°C

Don't skip the long-term cooling phase. This controlled cooling is essential for optimal crystal formation and final strength development.

Surface Treatments

After crystallization, Tessera has a beautiful natural surface that often requires minimal adjustment. For occlusal adjustments, use fine diamond burs under water cooling, followed by polishing with ceramic polishing systems.

If significant adjustments are needed, consider a glaze firing to restore optimal surface properties. I use this approach when more than minor spot grinding is required.

Bonding Protocols for Optimal Retention

Surface Preparation

Tessera bonds predictably using standard lithium disilicate protocols with some refinements:

1. Hydrofluoric acid etch: 20 seconds with 5% HF (I prefer the 5% concentration for more controlled etching)
2. Thorough water rinse and air dry
3. Silane application: 60 seconds contact time, then air thin
4. Light cure the silane for 10 seconds

The key difference I've found with Tessera is that it etches very uniformly, creating consistent bonding surfaces. This contributes to predictable bond strengths.

Cement Selection

I primarily use light-cured resin cements for single crowns and dual-cure for bridges or cases where light penetration might be limited. Tessera's translucency allows excellent light transmission for polymerization.

For cement shade selection, Tessera's natural translucency means the cement shade has minimal impact on final color in most cases. I typically use universal or light shades unless specific color modification is needed.

Clinical Considerations and Case Selection

Ideal Cases for Tessera

Tessera excels in several clinical scenarios:

• High-stress posterior environments
• Patients with parafunctional habits (with proper occlusal management)
• Cases requiring conservative preparations
• Three-unit posterior bridges
• Situations where esthetics and strength are both priorities

Cases to Consider Alternatives

While Tessera is versatile, it's not always the best choice:

• Severe bruxers might benefit from zirconia
• Very deep subgingival margins can be challenging for bonding
• Cases where maximum translucency is needed (anterior veneers)

Troubleshooting Common Issues

Marginal Chipping

If you experience marginal chipping, check your preparation smoothness first. Sharp internal angles or rough surfaces can create stress concentrations. Also verify your milling burs are sharp and properly seated.

Color Matching Challenges

Tessera's natural translucency usually provides excellent color integration, but in high-translucency situations, consider the underlying tooth color. Heavily discolored preparations might require masking with cement or internal staining.

Bonding Failures

Consistent bonding protocols are critical. The most common issue I see is inadequate isolation during bonding. Tessera's strength means debonded restorations often remain intact, making rebonding possible if the restoration is undamaged.

Long-term Performance Observations

After two years of clinical use, I'm impressed with Tessera's performance. The material shows excellent wear characteristics, maintains its surface polish well, and I haven't experienced any unexpected fractures when proper protocols are followed.

Patient feedback has been consistently positive, particularly regarding comfort and natural feel. The material seems to integrate well with natural tooth structure both functionally and esthetically.

Frequently Asked Questions

Can Tessera be used for implant crowns?

Yes, Tessera works well for implant crowns. The bonding protocols remain the same, but ensure your abutment material is compatible with your chosen cement system. I've had excellent results with both titanium and zirconia abutments.

How does Tessera compare to zirconia for posterior bridges?

For three-unit bridges, Tessera offers better esthetics with adequate strength. Zirconia remains my choice for longer spans or extreme loading situations. The decision often comes down to esthetic requirements and loading conditions.

What's the learning curve for transitioning to Tessera?

If you're already comfortable with lithium disilicate workflows, the transition is straightforward. The main differences are in the improved milling characteristics and slightly modified firing protocols. Most practitioners adapt within a few cases.

Can Tessera restorations be repaired if damaged?

Minor chips can be repaired using composite resin systems designed for ceramic repair. However, significant damage usually requires replacement. The material's strength means minor damage is less common than with traditional ceramics.

Is special equipment needed for Tessera processing?

No special equipment is required beyond standard CEREC systems and ceramic furnaces. The material works with existing workflows, though ensuring your furnace can run the specific Tessera firing cycle is important for optimal results.

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