Bending Strength Standards & Methodologies

break-stick-300wSUMMARY: ISO testing of Crystal Ultra resulted in approximately 155 MPa to 205 MPa in Flexural strength depending on the testing methodology employed.  Our published number of 175 MPa is based upon the 3-point bending testing using the most universally accepted international standards.  All testing methods far exceed both FDA and European standards for dental ceramics.  For a more useful strength comparison, Crystal Ultra recommends analyzing Compressive Strength, which better simulates the chewing stresses found in the mouth.

SCIENCE: DLMS has not been able to confirm the flexural strength results of our competitors products, and so no apples-to-apples comparison of flexural stength has been conducted of the comparable ceramic dental materials.  However, all dental material manufacturers must exceed 100 MPa in flexural strength in order to be registered with the FDA, and they must exceed 50 MPa under European standards, and we believe that all materials meet this basic standard.

Read more ...

Bond Strength Compared to Titanium / Composite

bond-test-tnBond/adhesion testing was conducted on Crystal Ultra using a variety of CFI bonding techniques according to specifications found in ISO 10477.

In general, the CFI’s bond with Crystal Ultra is suitable if not superior to the typical composite to composite or composite to titanium bonds. This bond strength remained excellent even at high temperatures. Sand blasting was determined to be the best surface conditioning method.

In this study, Crystal Ultra was bonded to a nano-composite material and compared to a nano-composite and titanium reference bond.

To download the complete study as a PDF file, click on the link below or the impage to the left.

pdfcrystalultra-bonding-strength-2014.pdf1.3 MB

3-Unit Bridge Five Year Mastication Simulation


A mastication simulation test involving 1.2 million simulated thermocycles at 70 Newtons of force was conducted on Crystal Ultra nanoceramic hybrid dental restorative material in November of 2008.

One of the unique properties of Crystal Ultra is that it is the only hybrid material approved today to be strong enough for use in creating bridges and full‐arch restorations, so we choose to do the simulation with three‐unit bridges in order to test the material in a more demanding stress and wear profile.

Read more ...

Restorations that Flex - Modulus of Elasticity


SOURCE: Manufacturer's published data

SUMMARY: The lower the number, the more the material flexes before it breaks.  At 10,000 MPa (or 10 GPa), Crystal Ultra is by far the most flexible dental ceramic in use today.   This flexibility makes the material ideal for implant dentistry where sensation and cushion afforded by the peridontal ligament is lost, and it allows the material to stand up better to the test of time where chewing forces eventually cause all-ceramics to weaken, chip, and crack. 


SCIENCE: Unlike other hybrids, a unique chemical bond is formed inside the Crystal Ultra material matrix which allows the polymers to flex while not breaking apart from the ceramics.

The photo to the right is a 3mm bar created out of Crystal Ultra and bent.  No other ceramic material used in dentistry can bend like this without breaking. 

Crystal Ultra is the only dental ceramic which is actually more flexible than both dentin and enamel while providing strength characteristics which are significantly superior to both.


Physical Properties of Crystal Ultra

Physical Property Measurement Standard Value
 Vickers Hardness (200 p)  710 MPa ** None specified
 Modulus of Elasticity
(Young Modulus)
 10,000 MPa ** None specified
 Flexural Strength  175 MPa ** ISO 10477 ≥ 50
ISO 6872 ≥ 100
 Compressive Strength  480-500 MPa ** ISO 4049 ADA 27
 Density  1.89 g/cm3 None specified
 Chemical Solubility  1.29 μg/cm3 ISO 6872 ≤ 100
 Water Absorption  16.94 μg/mm3 ISO 10477 ≤ 40
 Water Solubility  0.04 μg/mm3 ISO 10477 ≤ 7.5
 Biocompatibility  Confirmed ISO 10993
 Ceramic Filler  70.02% (wt) None Specified
 Color Stability  Confirmed ISO 10477
 Shade Consistency  Confirmed ISO 10477
 Surface Finish  Smooth ISO 10477
 Bond Strength  27-37 MPa ISO 10477 ≥ 5

1 Mpa = 1 N/mm2 = 0.102 kg/mm2
* = Lot: P 2.61c
** = Measured data ± 10%

Vickers Hardness vs Gentleness



Vickers Hardness is tested by striking specially shaped diamond anvil against the material and measuring the size of the indent created with varying force.

In dentistry, hardness is what creates the clackiness found with most ceramic dentistry, as opposed to the soft and gentle bite characteristics of a Crystal Ultra restoration.

At less than 0.7 GPa (700 MPa), Crystal Ultra is the only esthetic material that is gentler than natural dentin.


Comparative Compressive Strength


Source: Manufacturer's published data

SUMMARY: Crystal Ultra is by far the strongest esthetic ceramic material, higher than 3M Lava Ultimate, and higher than e.max, vita mark II and empress CAD, making Crystal Ultra the toughest dental material in use for cosmetic, minimally invasive and implant dentistry.

SCIENCE: The higher compressive strength of Crystal Ultra is the result of special manufacturing processes used to bond the glass and polymer materials, including the use of a special sylanated glass ceramic which chemically bonds to the polymers, as compared to other hybrid or ceramic materials that form no such chemical bond.

Compressive strength, which best simulates chewing forces in the mouth, is measured by applying both upward and downward pressure on an object until it breaks.  Unlike Flexural Strength, which similates breaking a stick over your knee and is measured many different ways according to different international standards, compressive strength is measured only one way according to one ISO standard.

STANDARDS: Compressive strength is measured according to International Standard ISO 4049 and ADA Specification 27.  Crystal Ultra specimens were tested in a universal testing machine at a crosshead speed of
1mm/min. Data were obtained in KGF and transformed into MPa using the following formula: 

RC = F x 9.807 / A


  • RC = compressive strength (MPa),
  • F = recorded force (kgf) multiplied by the constant 9.807(gravity), and
  • A = base area (7.06 mm2)

Upcoming Trade Shows

Please visit Digital Dental at our booth at one of these trade shows this year.

  • Sep 8, 2018 - LMT East  - Philadelphia, PA
  • Sep 26-29, 2018 - AAID - Dallas, TX
  • Sep 28-29, 2018 - IDT - Phoenix, AZ
  • Oct 11-13, 2018 - DLOAC CAD/CAM Expo - Orange County, CA
  • Oct 31-Nov 3, 2018 - ACP - Baltimore, MD
  • Feb 21-23, 2019 - CDS Midwinter - Chicago, IL
  • Feb 22-23, 2019 - LMT Chicago - Chicago, IL
  • Mar 13-16, 2019 - AO - Washington, DC

Crystal Ultra Specs

Physical Property Measurement
 Vickers Hardness (200 p)  710 MPa **
 Modulus of Elasticity 
(Young Modulus)
 10,000 MPa **
 Flexural Strength  175 MPa **
 Compressive Strength  480-500 MPa **
 Density  1.89 g/cm3
 Chemical Solubility  1.29 μg/cm3
 Water Absorption  16.94 μg/mm3
 Water Solubility  0.04 μg/mm3
 Biocompatibility  Confirmed
 Ceramic Filler  70.02% (wt)
 Color Stability  Confirmed
 Shade Consistency  Confirmed
 Surface Finish  Smooth
 Bond Strength  27-37 MPa