How to Prevent Chipping in Pressable Ceramic Restorations？

Pressable ceramics, such as lithium disilicate (e.g., IPS e.max Press), are widely praised for their aesthetics and durability. However, chipping remains a concern, with studies reporting a 5-10% complication rate over 5 years. As a dental materials supplier, we’ve collaborated with leading labs and clinicians to identify actionable strategies to minimize this risk.

1. Optimize Restoration Design

Critical Design Parameters

• Minimum Thickness:

  • Anterior crowns: ≥1.5mm occlusal/incisal thickness.

  • Posterior crowns: ≥2.0mm functional cusp thickness.
    Why it matters: Thin areas (<1.0mm) increase flexural stress by 300% (J Prosthet Dent, 2022).

• Avoid Sharp Angles:

  • Rounded internal line angles (≥0.5mm radius) reduce stress concentration.

  • Use deep chamfer margins instead of featheredge designs for better support.

Pro Tip:
Partner with labs using 3D finite element analysis (FEA) software to simulate stress distribution before pressing.

2. Material Selection: Match Indication to Strength

Pressable Ceramic Grades

Common Pitfall:
Using low-strength ceramics (e.g., leucite-based) for molar crowns leads to premature failure.

3. Cementation Protocol: Bonding vs. Adhesive Luting

Bonded Restorations (Gold Standard)

1. Surface Treatment:

   • Hydrofluoric acid (HF) etching: 20 seconds for lithium disilicate (5% concentration).

   • Silanization: Apply a 2-step silane (e.g., Monobond Plus) for 60 seconds.

2. Resin Cement Selection:

   • Dual-cure cements (e.g., Variolink Esthetic DC) for optimal polymerization in deep cavities.

⚠️ Avoid:

• Self-adhesive cements for thin restorations—insufficient bond strength increases flexural stress.

4. Occlusal Adjustment: The 30μm Rule

Step-by-Step Protocol

1. Pre-cementation Adjustment:

   • Use fine-grit diamond burs (≤50μm grit) under water cooling.

2. Polishing Sequence:

   • Coarse → Medium → Fine polishing rubbers (e.g., Dialite Kit).

   • Finish with diamond-impregnated paste (1μm grit).

Key Data:

• Surface roughness >0.2μm Ra increases fracture risk by 40% (Int J Prosthodont, 2021).

5. Lab Communication: 4 Must-Share Details

Provide labs with:

1. Bite Registration: For proper occlusal scheme replication.

2. Antagonist Material: Natural tooth, ceramic, or metal?

3. Bruxism History: Request 0.5mm overcontouring for grinders.

4. Shade Guide Photos: Minimize multiple firings for staining.

6. Post-Insertion Care: Patient Education

Handout Checklist

• Avoid chewing ice/hard candies for 48 hours post-cementation.

• Nightguards for bruxism patients (recommend soft inner layer + hard outer shell).

• Schedule annual bite force checks with T-Scan® analysis.

When Failure Occurs: Repair vs. Replace