Back to blog

Close-up: Zirconia surfaces

MDT Joachim Maier ran an ad hoc test series to analyse the effects of mechanical processing on sintered zirconia surfaces. The test involved using an atomic force microscope to examine the degree of damage caused to zirconia surfaces by grinding them with various diamond instruments (see image gallery above with the results). In the excerpt from his study published here he also provides hints as to how surfaces can nevertheless remain homogeneous.

Mon. 28 June 2021, 12:00 PM

Close-up: Zirconia surfaces

Zirconia surface after grinding with black diamondPeak-Peak-Hight (Sy): 2273 nm | Mean Roughness (Sq): 292 nm | Largest Peak (Spk): 234 nm | Deepest Valley (Svk): 507 nm

Mechanical processing of zirconia after sintering is an important step for ensuring the restoration remains stable long-term. Excessively thick crown margins after milling or optimisation of occlusal surfaces in monolithic regions necessitate grinding of the sintered surface. This is carried out with water-cooled diamond instruments at high speed and exerting only minimal pressure.

But under everyday circumstances in the laboratory, the pressure can only be measured and controlled subjectively. In-lab tests showed that under practical conditions surfaces are often subjected to more stress than during scientific studies run with programmable, defined and uniformly operating machines. Our practical tests showed that all types of instrument damaged the surface. Not until polished in three stages with diamond-impregnated silicone polishers was the surface quality such that monolithic areas were virtually non-abrasive to the opposing dentition and, with bridgework for veneering, no fractures could be initiated in that region of the framework subjected to tensile strain.

CONCLUSION:

1.  Zirconia must only be grinded where necessary.
2. Grind with water-cooled diamond instruments and exert only minimal pressure.
Red ring diamonds are the most efficient.
 (see third image in the gallery above)
3. Optimising the surface by polishing in 3 stages with diamond-impregnated silicone polishers.
 (see last image in the gallery above)

 

 

Fig. 1 - Zirconia surface after grinding with black diamondPeak-Peak-Hight (Sy): 2273 nm | Mean Roughness (Sq): 292 nm | Largest Peak (Spk): 234 nm | Deepest Valley (Svk): 507 nm Fig. 1 - Zirconia surface after grinding with black diamondPeak-Peak-Hight (Sy): 2273 nm | Mean Roughness (Sq): 292 nm | Largest Peak (Spk): 234 nm | Deepest Valley (Svk): 507 nm
Fig. 2 - Zirconia surface after grinding with blue diamondPeak-Peak-Hight (Sy): 3667 nm | Mean Roughness (Sq): 519 nm | Largest Peak (Spk): 379 nm | Deepest Valley (Svk): 395 nm
Fig. 2 - Zirconia surface after grinding with blue diamondPeak-Peak-Hight (Sy): 3667 nm | Mean Roughness (Sq): 519 nm | Largest Peak (Spk): 379 nm | Deepest Valley (Svk): 395 nm
Fig. 3 - Zirconia surface after grinding with red diamondPeak-Peak-Hight (Sy): 5079 nm | Mean Roughness (Sq): 462 nm | Largest Peak (Spk): 665 nm | Deepest Valley (Svk): 445 nm
Fig. 3 - Zirconia surface after grinding with red diamondPeak-Peak-Hight (Sy): 5079 nm | Mean Roughness (Sq): 462 nm | Largest Peak (Spk): 665 nm | Deepest Valley (Svk): 445 nm
Fig. 4 - Zirconia surface after grinding with yellow diamond
Peak-Peak-Hight (Sy): 2797 nm | Mean Roughness (Sq): 513 nm | Largest Peak (Spk): 455 nm | Deepest Valley (Svk): 496 nm Fig. 4 - Zirconia surface after grinding with yellow diamond Peak-Peak-Hight (Sy): 2797 nm | Mean Roughness (Sq): 513 nm | Largest Peak (Spk): 455 nm | Deepest Valley (Svk): 496 nm
Fig. 5 - Zirconia surface after grinding and subsequent polishing with polishersPeak-Peak-Hight (Sy): 296 nm | Mean Roughness (Sq): 52 nm | Largest Peak (Spk): 30 nm | Deepest Valley (Svk): 53 nm Fig. 5 - Zirconia surface after grinding and subsequent polishing with polishersPeak-Peak-Hight (Sy): 296 nm | Mean Roughness (Sq): 52 nm | Largest Peak (Spk): 30 nm | Deepest Valley (Svk): 53 nm
Related blog posts

Mon. 21 June 2021, 12:00 AM

5 tips for processing zirconia

5 valuable tips for processing restorations with zirconia

Tue. 27 April 2021, 9:00 AM

Zolid Zirconia – Dental dreams are made of this

Zirconia (ZrO2) forms the ideal basis for all-ceramic restorations as this material has outstanding properties that can hardly be matched by any other material. With Zolid, Amann Girrbach provides a comprehensive all-ceramic system for high-quality and esthetic zirconia restorations.

Bogna Stawarczyk
Prof. Dr. Dipl. Ing (FH) Bogna Stawarczyk Ludwig-Maximilians-University Munich

Tue. 27 April 2021, 3:00 PM

The influence of the zirconia sintering temperature on its color shade

The signficance of maintaining the sintering temperature for zirconia is meanwhile suficiently well established with regard to the influence on strength and translucency.

Falko Noack
Falko Noack Amann Girrbach

Follow us!