Zirconia and Modern Dental Materials: What Labs Need to Know

The materials available to dental labs have transformed dramatically over the past decade. Zirconia has risen from a specialty material to the workhorse of many labs, while new ceramics, composites, and hybrid materials continue expanding the options. Understanding these materials—their properties, processing requirements, and ideal applications—is essential for delivering excellent restorations.

The Rise of Zirconia

Zirconia (zirconium dioxide) has become the dominant material for posterior restorations and is increasingly used anteriorly. Its popularity stems from a compelling combination of strength, biocompatibility, and esthetic potential.

Why Zirconia Dominates

Exceptional Strength Zirconia’s flexural strength of 900-1400 MPa far exceeds other ceramics. This makes it ideal for posterior crowns, long-span bridges, and implant restorations where occlusal forces are significant.

Predictable Processing Modern CAD/CAM workflows handle zirconia efficiently. Mills cut the soft “green state” material quickly, and sintering furnaces deliver consistent final properties.

Esthetic Evolution Early zirconia was criticized for opacity. Multi-layered and gradient materials now offer natural translucency gradients that rival lithium disilicate for many applications.

Cost Efficiency Competition among manufacturers has driven prices down, while improved milling efficiency reduces labor costs. Zirconia often offers the best value for full-coverage restorations.

Zirconia Generations

Understanding zirconia types helps in material selection:

Generation	Yttria Content	Translucency	Strength	Best Applications
1st Gen (3Y-TZP)	3%	Low	Very High (1200+ MPa)	Posterior frameworks
2nd Gen (4Y-TZP)	4%	Medium	High (900-1100 MPa)	Posterior crowns
3rd Gen (5Y-TZP)	5%	High	Moderate (700-900 MPa)	Anterior monolithic
Multi-layer	Gradient	Variable	Variable	Full-arch, esthetic posteriors

Higher yttria content increases translucency but reduces strength. Match the material to the clinical situation—don’t use highly translucent zirconia where strength is paramount.

Processing Considerations

Milling Zirconia mills best in its pre-sintered state. Use sharp burs, appropriate speeds, and ensure adequate material thickness in the design phase. Account for approximately 20-25% shrinkage during sintering.

Sintering Follow manufacturer protocols precisely. Temperature curves and hold times affect final properties. Rushed sintering compromises strength and can cause internal stresses.

Coloring and Glazing Apply staining before sintering (with most materials) or use post-sintering glazes. Some labs prefer monolithic shade-matched materials that require minimal coloring.

Bonding Zirconia requires surface treatment for optimal bonding. Options include air abrasion with alumina, tribochemical coating, or primers containing phosphate monomers like MDP.

Material Selection Guide

Beyond zirconia, labs work with a diverse material palette:

Lithium Disilicate

Properties:

• Flexural strength: 400-500 MPa
• Excellent translucency and esthetics
• Can be milled or pressed
• Proven long-term clinical performance

Best for: Anterior crowns, veneers, inlays, onlays where esthetics are priority

Considerations: Less suitable for long-span bridges or heavy bruxism cases

Feldspathic Porcelain

Properties:

• Most natural optical properties
• Layerable for ultimate esthetics
• Requires skilled technician artistry
• Lower strength than glass ceramics

Best for: Veneers, anterior work requiring maximum customization

Considerations: Time-intensive; reserved for cases where the esthetic premium is justified

PMMA (Polymethyl Methacrylate)

Properties:

• Easy to mill and adjust
• Excellent for temporary restorations
• Good shock absorption
• Not suitable for permanent restorations

Best for: Long-term temporaries, implant provisionals, try-in dentures

Considerations: Use only as intended—PMMA is a temporary material

Composite Resins

Properties:

• Good esthetics with simplified workflow
• Less brittle than ceramics
• Can be milled or 3D printed
• Limited long-term data for some applications

Best for: Inlays, onlays, some crown applications

Considerations: Evaluate newer composite products on a case-by-case basis

Metal Alloys

Properties:

• Highest strength available
• Excellent fit and marginal integrity
• Long clinical track record
• Requires porcelain layering for esthetics

Best for: Long-span bridges, implant frameworks, patients with severe bruxism

Considerations: Metal is unfashionable but still clinically superior in some situations

Processing and Handling

Quality Starts with Design

Material performance depends on proper design:

• Minimum thickness: Respect manufacturer guidelines—thin sections fail
• Connector dimensions: Bridges need adequate connector cross-sections
• Margin design: Match design to material and cement type
• Occlusal considerations: Functional contacts on zirconia, not on feldspathic layering

Storage and Handling

Materials are investments—protect them:

• Store in controlled environments (temperature and humidity)
• Rotate stock—use oldest materials first
• Check lot numbers and expiration dates
• Document materials used for traceability

Troubleshooting Common Issues

Chipping or fracture during milling:

• Check bur sharpness and replace worn tooling
• Verify milling parameters match material
• Ensure adequate thickness in design

Post-sintering cracks:

• Review sintering protocol for errors
• Check for contamination before sintering
• Evaluate design for stress concentrations

Poor fit:

• Calibrate scanner and mill regularly
• Account for correct shrinkage factors
• Verify margin capture quality in scan data

Quality Considerations

Consistency Matters

Patients and clinics notice quality variations:

• Standardize processes across technicians
• Document material and technique choices per case
• Regular calibration of equipment
• Quality check points throughout workflow

Certification and Documentation

Materials come with responsibilities:

• Maintain certificates of conformity
• Track lot numbers per case
• Keep material safety data sheets current
• Follow manufacturer instructions for use

When to Reject Work

Not every case should ship:

• Visible defects or damage
• Dimensions outside tolerance
• Color mismatch from prescription
• Material certificates unavailable

Better to catch problems internally than receive remakes.

Emerging Materials

The materials landscape continues evolving:

Gradient and Layered Zirconia

Multi-layer blanks with built-in shade and translucency gradients simplify production of natural-looking monolithic restorations without manual layering.

High-Strength Lithium Disilicate

New formulations push lithium disilicate strength higher while maintaining esthetic properties, expanding its range of applications.

Hybrid Ceramics

Polymer-infiltrated ceramic networks combine properties of both material classes, offering unique combinations of strength, esthetics, and machinability.

3D Printed Ceramics

While not yet mainstream, additive manufacturing of ceramic materials shows promise for complex geometries that are difficult to mill.

Building Material Expertise

Labs that understand materials deeply serve clients better:

• Invest in continuing education for technicians
• Maintain relationships with material suppliers
• Test new materials before production use
• Document outcomes to guide future decisions

Material science in dentistry moves fast. Labs that stay current with material developments deliver better clinical outcomes and differentiate themselves in a competitive market.