What Kerox Zircostar zirconia is
Kerox has made precision ceramic parts in Hungary for about four decades, and Zircostar is its line of pre-sintered zirconia blanks for CAD/CAM milling. The company presses the blanks axially and then by cold isostatic pressing before pre-sintering them, and its catalogue states a quality system certified to ISO 9001, ISO 13485 and ISO 14001. The catalogue gives a typical composition for the whole Zircostar family: 90.2–94.3 wt% zirconia and 5.7–9.8 wt% yttria, with alumina below 0.25 wt%. It does not state the yttria content of each type separately.
The range has three monolithic blanks and three multilayer blanks. The strength figures below are the highest values measured by FKG GmbH in Germany, as the catalogue footnote says, not typical or minimum values:
| Zircostar type | Translucency | Flexural strength (maximum measured) |
|---|
| HS (High Strength) | 41% | up to 1,443 MPa |
| HT (High Translucent) | 43% | up to 1,350 MPa |
| UHT (Ultra High Translucent) | 49% | up to 1,175 MPa |
| HTML (High Translucent Multilayer) | 45% | up to 1,389 MPa |
| UTML (Ultra Translucent Multilayer) | 49% | up to 746 MPa |
| 3DML (3D Multilayer, five layers) | 43–49% | up to 820–1,085 MPa by layer |
The catalogue does not give the method used to measure translucency. The product photo above shows the Zircostar 3D Multilayer discs from the Kerox website.
Zircostar HT: strength and translucency
The catalogue classifies HT as Type II, Class 5 under ISO 6872:2015, the same class as HS and UHT. Its top measured flexural strength is 1,350 MPa, against 1,443 MPa for HS and 1,175 MPa for UHT. Because these are best results rather than averages, they show where HT sits in the Kerox range more than what a single restoration will reach; a design with proper wall thickness and connector size matters more than the headline figure.
Translucency is listed at 43%, between the opaque HS (41%) and the UHT (49%). Kerox describes HT as suited to long-span monolithic bridges and to the cut-back technique, where the facial surface is reduced and finished with layered porcelain. For a single anterior crown where translucency comes first, a more translucent zirconia may suit the case better; the comparison links at the end of this page show the other lines we work with.
The catalogue also lists, for the sintered HT body, a bulk density of 6.05 g/cm³ and a coefficient of thermal expansion of 9.9 × 10⁻⁶ /°C. For the background on zirconia generations, see 3Y-TZP vs 5Y-PSZ zirconia.
Indications and design limits
The Kerox instructions for use for HS, HT and UHT (document MF-07-KD-935, version F, 2023) give a processing guide for each type. For HT the guide reads as follows:
- Crowns: copings are recommended for anterior and posterior teeth; full-contour crowns are recommended for posterior teeth and allowed for anterior teeth.
- Bridges: frameworks and full-contour bridges up to six units in the anterior and up to five units in the posterior region; frameworks are recommended in both regions, full contour is recommended in the posterior and allowed in the anterior.
- Full-arch bridges: up to 14 units; recommended as a framework, allowed as full contour.
- Minimum wall and occlusal thickness: 0.4 / 0.5 mm for anterior copings and frames, 0.5 / 0.7 mm for posterior copings and frames; 0.5 mm (anterior) and 0.6 mm (posterior) wall thickness for full-contour work.
- Minimum connector size: 6 mm² (anterior frame), 7 mm² (anterior full contour), 9 mm² (posterior bridges), and 6–12 mm² (framework) or 7–13 mm² (full contour) for full arches.
The same IFU states that Zircostar must not be used for implant superstructures or abutments connected directly to an implant, and that it is not recommended for patients with bruxism. Connectors must not be thinned after sintering. The FDA 510(k) summary K120852 (2012) describes Zircostar blanks for crowns, multi-unit bridges and inlay bridges in the anterior and posterior regions, without naming the HT type. If a scan shows too little room for these minimums, our CAD team raises it at the design stage.
Sintering, shades and blank sizes
Kerox gives two sintering programs for HT, both with a final temperature of 1,530 °C and a 120-minute hold:
- Normal program (all restorations): 10 °C/min to 900 °C, hold 30 minutes, 5 °C/min to 1,530 °C, hold 120 minutes, cool at 10 °C/min to 900 °C and 15 °C/min to 150 °C, or let it cool passively.
- Speed program: faster heating and cooling (30 and 20 °C/min) with the same holds, limited to four units and not for curved restorations.
- Shades: white for coloring with Kerox liquids (16 VITA classical shades), or preshaded A1, A2, A3, B2, D2 and Bleach; our HT discs are preshaded.
- Blank sizes: 98, 95, 71 and 100 mm formats, 10 to 25 mm thick.
Before milling, the shrinkage factor printed for each blank is entered in the CAM software, and the toolpath stays at least 1 mm from the blank edge, as the IFU asks. Any adjustment after sintering is done with water-cooled diamonds, and full-contour occlusal surfaces are polished so that they do not wear the opposing teeth. If the shade you need is better matched by another material, we will tell you before production.
Ordering Zircostar restorations from Khai Nguyen
Zirconia crowns and bridges take 2–4 working days in the lab. Overseas cases then ship by DHL, which usually takes 2–4 days. The Kerox IFU excludes implant superstructures, so implant-supported work calls for another zirconia from the lines linked below; zirconia on implants takes 3–4.5 working days. More on timing in Vietnam dental lab turnaround time and shipping.
With the case, please state:
- The restoration type and tooth numbers.
- Whether you want Zircostar HT, or let us choose the material.
- The VITA shade, the stump shade and shade photos if available.
- Any history of bruxism, which matters for the choice of material.
- Your cementation protocol, so that we can set the cement space.
Restorations are covered by our general warranty (6 months to 15 years depending on the material). To compare with other zirconia, see Luxen, IPS e.max ZirCAD Prime, Ceramill Zolid and DMax Natura, or browse all the zirconia blanks we work with. To discuss a case, please contact Khai Nguyen or follow our ordering process.
Technical values come from the Kerox product catalogue, the Zircostar HS/HT/UHT instructions for use and the FDA 510(k) summary K120852. This page is written for dentists and dental technicians. Khai Nguyen Dental Lab fabricates restorations only on professional prescription and does not sell directly to patients.
