RAW MATERIAL

Three Crystal States Of Zirconium Dioxide

Monoclinic - Until 1170 °C
Tetragonal - From 1170 °C until 2370 °C
Cubic - Above 2370 °C
CERAMICS RAW MATERIAL
  • The zirconia particles must have a tetragonal crystal structure (cubic for jewelry, monoclinic is weak)
  • The tetragonal structure is unstable in the mouth, just the right amount of stabilizing Yttria is needed (3.0 mol%)
  • Blanks must have this structure microscopically everywhere
Yttria concentration: on average 3 mol%
  • Increased aging
  • Breaking
  • Shrinkage problems
Yttria concentration: on average 3 mol% ...and 3 mol% in every particle
  • Slow aging
  • Evenly strong
  • Perfect shrinkage

KEROX 100 year lifetime warranty

Gamma Irridiaton

PRESSING: DIFFERENCE IN TECHNOLOGIES

QUALITY VS. QUANTITY
KEROX MULTI PRESSING

Kerox Dental Zirconia blanks are made Yttria stabilized on every single grain – manufactured by market leader Japanese company.

CHEMICAL PROPERTIES

Ingredients Weight percentage (%)
ZrO2 > 94.10
Y2O3 5.20
Al2O3 0.25
HfO2 < 0.30
SiO2 ≤0.02
Fe2O3 ≤0.01
Na2O ≤0.04

PHYSICAL PROPERTIES

Typical properties of sintered body
Density (g/cm3) 6.05
Bending strength (MPa) 1500
Surface hardness (HV10) 1250
Radioactivity (Bq/g) < 0.01

AXIAL PRESSING ONLY IS INSUFFICIENT
  • Pressure and mold densification are uneven
  • Different density, shrinkage, hardness
COLD ISOSTATIC PRESSING
  • Extreme pressure
  • Even densification & mass
  • Less porosity
  • Less unevenness
  • Homogeneity

KEROX DENTAL MULTI PRESSING

Cold Isostatic pressing is time-consuming but it leaves less material stress and strain, than axial press. In Kerox Dental to the axially pre-pressed blocks an isostatic manufacturing process is applied – that’s Kerox Dental Multi Pressing. The all around, extreme pressure during the isostatic pressing ensures a maximum homogenous density in all Kerox Dental blocks. Optimal blank porosity and density decrease amortization of both the milling machine and the milling heads of the dental laboratory.

2-WAY PRESSING

AXIAL only: quick and dirty way

  • Porosity on edges & top
  • Too hard in the middle
  • Different strength, density
    = different shrinkage

ISOSTATIC PRESSING (cold)

even pressure via liquid

  • Extreme pressure
  • Even density & mass
  • Homogeneity

Perfect shrinkage

Axial press 120 – 150 tons

  • Press-time: 10 sec / blank.
  • 4 axis press:
  • Pre-press > adjustment est. density > re-press.
  • Material resistance
  • Press-data stored for 5 years

High pressure isostatic press

  • 2000-4000 bars
  • US Army Grade (signed to not use it for military purposes)
  • 10-16 blanks per 10 minutes (Pressure up-building; Hold; Release)
  • Drawback: high cost

SINTERING: THE BASICS

DE-BINDING

Ensure no organic contamination and water. Lubricants and additives (that ensure press ability) burned off.

PRE-SINTER

“Neck formation” by diffusion at pre-sinter. Ensure best crystal sizes and machining properties.

FINAL SINTER

Particles melted, density increased, pore sizes decreased at final sinter. Ensure final metastable tetragonal structure.

OPTIMAL
PROCESS

Kerox Dental measures grain size and density, to optimize quality and lessen fatigue (by avoiding over-firing). Suboptimal press and sinter would lead to chipping or breaking during the milling process. Kerox Dental’s documented experience in pressing and sintering provide labs zirconia discs with optimal/required combination of density, strength, millability, and with high bending strength, fatigue features, consistency.

PRE-SINTERING

Products Spend Up To One Week In The Furnace

Strength, Translucency and Easy Millability

  • Crystals have more connection points – higher strength
  • Lower sintering temperature in lab
  • Opaque due to many cavities in the structure where light breaks
  • Larger crystals have fewer connection points – lower strength
  • Higher sintering temperature needed
  • Fewer (and larger) cavities in the crystal cause higher translucency

Easy to adjust after sintering due to small grain sizes

  • Keeping many connection points
  • Reducing cavities in the crystal cause higher translucency
  • KEROX: HIGH STRENGTH AND HIGH TRANSLUCENT AT THE SAME TIME