Why IPS e.max for Inlays & Onlays
Material Advantage: Lithium Disilicate Glass-Ceramic
IPS e.max is a brand name for lithium disilicate (Li₂Si₂O₅) glass-ceramic manufactured by Ivoclar. It should not be confused with:
- EMAX (FPV drone motors, industrial products)
- Emax (pharmacological modeling term)
The material itself offers:
- Flexural strength: 530 MPa (CAD crystallized) / 470 MPa (Press) — manufacturer specification
- Metal-free composition: biocompatible, no allergic reactions
- Translucency options: HT (high), MT (medium), LT (low) to match natural enamel
- Color stability: resistant to staining over time
- Adhesive bonding: chemical bond to tooth structure via silane coupling
When to Choose an Inlay/Onlay Over Alternatives
| Restoration | Indication | Tooth Preparation | Longevity |
|---|---|---|---|
| Direct composite | Small to moderate cavities | Minimal | 5–7 years (typical) |
| IPS e.max inlay/onlay | Large cavities, cusp replacement | Moderate (depth ≥1.0 mm) | 10-year survival 91–95% meta-analysis; 95% survival at 16.9 years in a prospective cohort Malament et al. 2021 |
| Full ceramic crown | Extensive damage, >50% loss | Aggressive (1.5–2 mm circumferential) | Similar to onlays at 5 years |
| Gold onlay | High occlusal stress, bruxism | Moderate | High long-term durability — Studer et al. 2000: cast gold inlays/onlays 96.1% / 87.0% / 73.5% survival @ 10 / 20 / 30 years (n=303) |
Clinical Preparation Guidelines
Why This Matters for Lab-Dentist Collaboration
One of the most common reasons for remakes or marginal failures is improper preparation. Unlike full crowns, inlay/onlay preparations have strict thickness and geometry requirements because the restoration relies on adhesive bonding rather than mechanical retention.
If we receive a case that does not meet these criteria, we will contact you before fabrication to avoid a remake.
Official Ivoclar Preparation Protocol
These are not our house rules — they are the manufacturer's published guidelines for IPS e.max inlays and onlays:
| Parameter | Minimum Requirement | Why |
|---|---|---|
| Cavity depth | ≥1.0 mm | Ensures adequate material thickness to resist fracture |
| Isthmus width | ≥1.0 mm | Prevents thin sections prone to chipping |
| Proximal box divergence | 100°–120° | Allows insertion path and prevents undercuts |
| Internal line angles | Rounded | Sharp angles create stress concentrations |
| Margin design | Butt joint or chamfer | Provides thickness at restoration edge |
| Prohibited margins | ❌ Feather edge, ❌ knife-edge, ❌ slice-cut prep | Leads to marginal fractures and debonding |
For onlays (cusp coverage):
- Cusp reduction: ≥1.0 mm in functional areas
- Occlusal clearance: ≥1.5 mm in centric occlusion
Source: Ivoclar Clinical Guide — IPS e.max Inlays & Onlays
What Happens If Preparation Is Inadequate
We perform a digital pre-check on all submitted STL files before fabrication. If we detect:
- Depth <1.0 mm in functional areas
- Sharp internal angles
- Feather-edge margins
- Severe undercuts
We will contact you within 2–3 working days to discuss modification options:
Adjust the digital design (if feasible within material limits)
Request a re-prep before fabrication
Recommend an alternative restoration (e.g., composite, crown)
We do not proceed with fabrication on cases we believe will fail clinically. This protects both your reputation and ours.
Manufacturing Process: CAD vs. Press
We offer two fabrication routes for IPS e.max restorations. Both use authentic Ivoclar material, but differ in workflow and final properties.
CAD-Milled (Recommended for Most Cases)
Process:
Digital design from your STL file
Milling from pre-crystallized e.max CAD blocks
Sintering and crystallization firing (final hardening step)
Characterization staining (if requested)
Glazing
Advantages:
- Faster turnaround: 2–3 working days
- Higher strength: 530 MPa after crystallization
- Better fit: CAD/CAM accuracy typically ±50 μm
- Easier remakes: digital design file stored
When to use: Standard inlays, onlays, veneers, single crowns
Press Technique (For Complex Esthetics)
Process:
Wax-up on die model
Investment and burnout
Heat-press with IPS e.max Press ingots
Divesting and finishing
Layering with effect ceramics (optional)
Staining and glazing
Advantages:
- Better for layered esthetics: allows hand-layered effects
- More forgiving anatomy: can handle complex contours
- 470 MPa flexural strength: still exceeds most alternatives
When to use: Anterior esthetics with complex characterization, cases where die model is preferred
Both workflows include:
- Material batch traceability (lot number recorded per case)
- Post-processing inspection (margins, occlusion, contacts)
- Try-in protocol available upon request
Quality Control & Delivery Standards
What You Receive
Every restoration ships with:
- Delivery slip: patient ID, tooth number, shade, material batch
- Digital design file (CAD cases): STL for your records
- Fitting instructions: adhesive protocol recommendation
Our QC Checkpoints
| Checkpoint | Specification | Rejection Criteria |
|---|---|---|
| Marginal adaptation | Gap <80 μm† | Visible gap, overhang, or open margin |
| Proximal contacts | 20–40 μm† pull resistance | No contact or excessive tightness |
| Occlusal anatomy | Matches opposing arch scan | High spots >50 μm† in centric |
| Internal fit | Seating without rocking | Binding or instability on die |
| Surface finish | No pits, voids, or inclusions | Visible defects >0.5 mm† |
Delivery & Turnaround
- Standard turnaround: 2–3 working days from case receipt
- Rush service: Available at no extra charge for ≤10 cases/month; priority scheduling managed by production lead
- Shipping: DHL, FedEx, or UPS (carrier selected based on destination); tracking number provided on ship date
Contraindications & Honest Material Limits
When We Recommend Against e.max Inlays
We will advise alternative solutions if you submit a case with:
Severe bruxism (grinding/clenching)
- Why: Ceramic is brittle under extreme lateral forces. Multiple studies note bruxism as a risk factor for chipping, though not always an absolute contraindication.
- Alternative: Gold onlay or nightguard + e.max combination. Cast gold restorations show the highest long-term survival of the four material classes compared here (see comparison table above).
- Source: Studer et al. 2000 — cast gold inlays/onlays, 303 restorations. A related r/Dentistry thread on a full-coverage onlay in a symptomatic patient exists in our source notes but was not retrieved in full and is not cited here.
Insufficient tooth structure (<1.0 mm remaining dentin)
- Why: Adhesive bond requires sound enamel/dentin. Thin walls increase crown-root fracture risk.
- Alternative: Post-and-core buildup + full crown
Subgingival margins >1.0 mm
- Why: Moisture control for adhesive cementation becomes unreliable.
- Alternative: Crown with supragingival margins after crown lengthening
Active caries or failed endodontics
- Why: Bonding to infected or unstable substrate leads to restoration failure.
- Alternative: Treat underlying pathology first
Known Failure Modes (What the Research Says)
We believe in evidence-based material selection. Here's what long-term clinical studies report:
| Failure Type | Incidence | Primary Causes |
|---|---|---|
| Fracture | 2.5–4% at 10 years | Insufficient thickness, occlusal overload, bruxism |
| Debonding | 1–3% at 10 years | Contamination during cementation, inadequate adhesive protocol |
| Marginal discoloration | 5–8% at 5 years | Microleakage, poor oral hygiene |
| Secondary caries | Rare (<1%) | Marginal gap, patient hygiene |
Sources:
- Morimoto et al. 2016 meta-analysis — 5,811 restorations, 10-year survival 91%
- Wang et al. 2022 systematic review (PMC9677648) — onlays vs. crowns, no significant difference at 5 years
- Malament et al. 2021 — 16.9-year survival of pressed e.max (J Prosthet Dent)
Adhesive Cementation Protocol
Critical: e.max inlays and onlays must be adhesively bonded. Conventional cementation (zinc phosphate, glass ionomer) will lead to early failure.
Surface Preparation (Your Responsibility)
Tooth preparation:
Isolate with rubber dam (mandatory)
Clean cavity with pumice slurry
Etch enamel + dentin (follow manufacturer's protocol for your adhesive)
Apply adhesive resin (do not light-cure yet)
Restoration preparation (done by you immediately before cementation):
Etch ceramic surface: 5% hydrofluoric acid gel, 20 seconds
Rinse and dry
Silane coupling agent: apply, wait 60 seconds, air-dry
Adhesive resin: thin coat on internal surface
Cementation
- Recommended cements: dual-cure or light-cure resin composites (e.g., Variolink, RelyX Ultimate, Panavia)
- Avoid: self-adhesive cements (weaker bond), conventional cements (will debond)
- Polymerization: light-cure from all accessible angles, 40 seconds per surface
- Excess removal: before full cure (gel phase), use floss and explorer
Post-cementation:
- Verify occlusion in centric and excursive movements
- Polish margins with fine diamonds or polishing discs
- Patient instructions: avoid hard/sticky foods for 24 hours
If the restoration debonds, check:
Was rubber dam used? (saliva contamination is the #1 cause)
Was the ceramic etched and silanated?
Was a resin-based cement used?
Collaboration Workflow
1. Case Submission
What we need from you:
- Digital impression (STL file) — prep, opposing, bite registration OR Physical model — stone die, articulated if occlusion is complex
- Prescription form: patient ID, tooth number, shade (Vita or Ivoclar), margin line marking (if applicable)
- Special requests: staining, high/low translucency, try-in appointment
Upload portal: (Contact your sales manager for portal access details) Alternative: courier pickup available for physical models
2. Design Review (Optional but Recommended)
For first-time collaboration or complex cases, we offer:
- Digital design preview: we send you the pre-milled STL for approval
- Try-in wax-up: physical model of proposed restoration (press cases)
- Turnaround: adds 1–2 working days to standard delivery
Why this matters: Reduces remakes due to anatomy or occlusion disagreements.
3. Fabrication
- Material sourcing: authentic Ivoclar IPS e.max (batch traceability provided)
- Quality checkpoints: margins, contacts, occlusion, surface finish
- Documentation: case photos and measurements retained for 3 months standard (extendable upon written request); compliance audit records retained per applicable regulatory requirements
4. Delivery
- Standard packaging: protective plastic case + delivery slip
- Rush/overnight shipping available (additional charge)
- If you identify a defect upon receipt, contact us before try-in. We will arrange remake or credit.
5. Clinical Try-In & Final Cementation
When to contact us:
- ✅ Before cementation if fit issues arise (we can adjust)
- ❌ After cementation if occlusion is high (this is adjustable chairside and not a remake scenario)
Remake policy: Free remake for fabrication defects identified before cementation. Client-side preparation issues or post-cementation fractures: charged at cost. Rush priority on all remakes (3–5 days standard).
Frequently Asked Questions
Can I use e.max for anterior teeth?
Yes, but only for inlays (Class III restorations). For anterior esthetics requiring full coverage, consider e.max veneers or crowns. The translucency options (HT/MT/LT) and custom staining allow excellent shade matching.
What's the difference between an inlay and an onlay?
- Inlay: fills the space between cusps, does not cover any cusp tips
- Onlay: covers one or more cusps (sometimes called a "partial crown")
- Preparation difference: onlays require ≥1.0 mm cusp reduction in functional areas
Do you offer Cerec same-day blocks for in-office milling?
No. We are a full-service lab, not a materials supplier. If you have in-office CAD/CAM and want to mill your own e.max restorations, purchase blocks directly from Ivoclar or a dental distributor. We fabricate and deliver finished restorations.
How do I know the material is authentic Ivoclar e.max?
Every delivery includes:
- Material batch/lot number on the prescription slip
- Certificate of authenticity available upon request
- Traceability documentation retained per ISO 13485 requirements
Red flag: If a lab offers "e.max-equivalent" or "lithium disilicate" at significantly lower prices, it may not be genuine Ivoclar material. Mechanical properties and clinical performance vary between manufacturers.
What if the patient has a ceramic allergy?
Lithium disilicate is glass-ceramic and generally biocompatible with no known allergic reactions. If you suspect sensitivity, request material safety data sheet (MSDS) or consider gold/zirconia alternatives.
Can e.max inlays be repaired if they chip?
Minor chips (<1 mm) can sometimes be polished smooth chairside. Major fractures require replacement. Unlike composite, you cannot "add" material to ceramic — the restoration is monolithic.
What's the warranty/guarantee?
We guarantee fabrication quality. Free remake if margins, fit, or material defects are identified before cementation. Warranty does not cover clinical failure after bonding, patient damage, or cases where we flagged prep issues in advance.
Important: Our warranty covers fabrication defects (poor margins, fractures during try-in, material defects). It does not cover:
- Fractures after cementation (clinical failure)
- Debonding due to improper cementation technique
- Patient damage (trauma, bruxism without nightguard)
- Preparation issues identified in advance but proceeded by dentist request
Get Started
Ready to submit a case?
📧 Email: (Contact your assigned sales manager)
📞 Phone: (Contact your assigned sales manager)
💻 Upload Portal: (Contact your sales manager for portal access details)
First-time clients: Contact us to set up account and discuss case submission workflow. We offer free design preview on your first case to ensure alignment on expectations.
Want to discuss a complex case first?
We welcome pre-submission consultations. Send us:
- Patient photos (intraoral)
- X-rays (if available)
- Brief clinical notes (chief complaint, treatment plan)
Our lab technicians will provide feedback on whether e.max inlay/onlay is the appropriate restoration, or recommend alternatives.
About Istar Dental Lab
Istar Dental Lab has been manufacturing precision dental restorations since 2012. With production facilities in Shenzhen and Huizhou, China, and a team of 460+ skilled technicians, we serve dentists, clinics, and dental laboratories worldwide.
Our capabilities:
- CAD/CAM digital workflow (5-axis milling)
- Traditional press and layering techniques
- Full-contour zirconia (separate product line)
- Removable prosthetics
Quality standards:
- ISO 13485 certified
- Material traceability and batch control
- Case records retained per regulatory requirements (standard retention 3 months, extendable upon request)
Why dentists choose us:
- Authentic manufacturer-grade materials (Ivoclar, 3M, Dentsply)
- Technical consultation before fabrication (we prevent remakes)
- Transparent pricing with no hidden fees
- English-speaking support team