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Zirconium Oxide Practice Guide
Clinical information and instructions
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Biocompatibility
We confirm that the product has been tested in accordance with the following international
standards: EN ISO 7405: “Dentistry. Preclinical evaluation of biocompatibility of medical
devices used in dentistry. Test methods for dental materials” and EN ISO 10993-1: “Biological
evaluation of medical devices”. The evaluation also included possible risks of cytotoxicity,
sensitisation, irritation and genotoxicity.
Material and indications
Properties
Today’s high-performance ceramics are the results of long process of development from natural stone
through clay and porcelain to current high-tech materials. A process that has taken millennia.
Zirconium dioxide (ZrO2, zirconium oxide for short) is a non-metallic, inorganic substance and belongs
to the oxide ceramics group. Zirconium oxide is non-magnetic and extremely resistant to acids and
alkalis. The substance is highly resistant to chemical, thermal and mechanical influences and in daily
use is not simply equal to metallic substances but superior.
The test of chemical solubility in the test laboratory of Heraeus Kulzer GmbH was conducted
in accordance with EN ISO 6872: “Dentistry – for ceramic materials”. The test showed that
the solubility of the tested ceramic is < 30 μg/cm². This confirms very good chemical solution
stability. In addition, the physical and mechanical material properties were
tested in accordance with EN ISO 13356 and assessed as very good.
The zirconium dioxide was classified as biocompatible (biologically
tolerable) with correct use.
The radiation dose emitted by a five-unit zirconium-oxide bridge is
significantly lower than that of one bottle of mineral water per day or
a glass of milk. According to international definitions zirconium oxide
is not a hazard to health. Scientific testing confirms that zirconium
oxide is safe for use in medical devices.
Exposed zirconium oxide should be polished to a high gloss
or glazed.
Zirconium oxide is extremely robust, has a high bending strength and flexural restistance, is wear and
corrosion resistant and is biocompatible. It is tooth-coloured or can be shaded without loss of quality.
All the above properties make zirconium oxide a high-performance ceramic.
Gingival compatibility
However, successful use of high-performance ceramics requires a complete change of attitude to design
and processing. This applies to industry as much as in medicine and dental technology. Its properties
are quite different from those of metals. This must always be kept in mind in the design and manufacture of ceramic products.
Zirconium oxide frameworks from well-known manufacturers are approved for up to 16 elements for
complex work in many cases. Modern CAD/CAM systems allow dental technicians to customise and
accurately manufacture zirconium oxide products or have them manufactured.
Another clinical advantage of zirconium oxide is its confirmed gingival compatibility and high plaque resistance.
Gingival contact with zirconium oxide is very good. It is
neither irritated or discoloured. Even retracted soft tissue
can regenerate around a zirconium oxide restoration.
The deposition of plaque and bacteria is only minimal on
the smooth zirconium oxide surface.
The following pages give you an overview of this high-quality material.
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cara workﬂow
Application
Service/Production
Software/
Design
• Zirconium: white, B-light, A-intense, translucent
• CoCr: CoCr milled, CoCr SLM
• Acrylic: RM model, PMMA prov./prov. light, PMMA CAO
• DentalDesigner
• DWOS
Finishing
• Ceramic: HeraCeram
• Composite: Signum
Scanning – Lab
• Impression scan:
cara D700/D710/D800/D810
• Model scan:
cara D700/D710/D800/
D810/D500/3series
Perfect
End Result
Scanning – Practice
• Intraoral scan: cara TRIOS
cara workﬂow
“I find the cara system good, because it guarantees my patients top-quality restorations with natural aesthetics at economical prices.
A win-win situation for all, patient, dental technician and dentist!”
Dr. med. dent. M. Sc. Andreas Adamzik
fixed denture: crowns or bridges
with up to 16 elements depending
on the wall or connector thickness.
– a maximum of two pontics in
the posterior and up to four
pontics in the lower anterior
region
Primary components for telescopic
or tapered crowns (only the fixed
primary frameworks)
two-pieces abutments by using a
titanium Interface
The proven cara quality is also available in non-precious metals and
PMMA for temporary restorations and
press-to technique. For more information visit www.heraeus-cara.com
Indication
Material
ZrO2 white/coloured
crowns
bridges
(up to 14 elements)
copings
anatomically reduced
fully anatomical
Yes
Yes
copings
anatomically reduced
fully anatomical
Yes
Yes
Max. 2 pontics
side-by-side
intermediate elements
Exceptions: lower anterior;
bridge from 3 to 3; you can fabricate
4 pontics side-by-side here!
⊘ = 6* – 9 mm2
connectors
depending on the span and
whether anterior or posterior
telescopes
Yes
Single crowns
press-to technique
File splitting
(Yes) CAO
Yes
implant abutments
* 6 mm2 connector cross-section applicable only for mandibular anterior bridges from 3 to 3
The tooth-coloured, slightly translucent and extremely tissuecompatible zirconium oxide gives the restoration optimum
light dynamics and ensures fast deposition of the gingiva.
Even the largest constructions fit without tension due to the
cementation of the two parts and the similar seating of the
screw in titanium. The precision of cara central manufacture
ensures exact fitting accuracy.
Indications
Superstructure
Titanium screw
Zirconium oxide abutment with
emergence profile
Interface
“We have been using cara restorations fabricated by CAD/CAM for many years now.
I am very pleased with the high precision and aesthetics of the cara restorations.
Even single-tooth crowns in the anterior region are not conspicuous and they meet
the highest possible aesthetic demands.”
Dr. med. dent. Andrea Wagner
Implant or laboratory analogue
Implant components
Contraindications
Bruxism and therapy-resistant parafunctions.
“cara offers us top quality, precision and flexibility with prosthetic restorations with a
consistency that would have been unthinkable a short time ago. Even very complex
constructions require virtually no corrections.”
Dr. Dusan Barac
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If the patient is hypersensitive to zirconium oxide and/or one of the other constituents, this medical
device must not be used or may be used only under close supervision by the physician or dentist.
Known cross-reactions or interactions of the substance with other medical devices or materials
already in the mouth must be considered by the dentist when using this substance.
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Preparation and insertion in the
dental practice
Dentist
Dentists must also consider properties specific to the substance
when working with full-ceramic restorations. Safe and reliable
results demand exact compliance with specific parameters
during preparation and insertion of the restoration in the dental
office.
Preparation
Tooth preparation is a particularly important step in the dental
work. Technical innovations now enable extremely accurate
scanning of surface data. Accurate tooth preparation and very
exact impressions in the dental practice are the base of precisely fitted, computer-manufactured
dentures.
The requirements for the preparation of zirconium oxide are only slightly different from conventional
rules for preparation. The dentist can prepare the teeth by the conventional methods. However, the
space required for dimensioning the framework may vary depending on the material. A ceramic restoration of zirconium oxide requires removal of only an insignificant extra amount of substance compared to that required for a conventional metal crown or bridge.
1.5
2.0
Fillet
Substance removal
About 1.5 to 2.0 mm of substance should be removed in the occlusal region to ensure sufficient
space for the ceramic veneering. When preparing crowns the dentist must ensure a sufficient axial
height of the tooth stumps with a taper angle of maximum 5° to 6° to establish adequate retention
surfaces. Oxide-ceramic frameworks, in contrast to metal frameworks, are frictionless; they should
slide onto the tooth stump without friction. Inherent friction in the internal framework may cause
tension and trigger the formation of microcracks.
During crown preparation enough tooth substance should be removed so the subsequent crown
frameworks have a thickness of no less than 0.6 mm. This is particularly important for crowns in
the posterior region and for abutment crowns in a bridge bond. The framework thickness can be
reduced as far as 0.3 mm in the anterior region if required for aesthetic reasons.
The danger, particularly for anterior tooth preparation, is the formation of peaked incisal edges. With
machine manufacture they can result in an unfavourable internal fit of the crowns. This also applies
to pointed cusps in preparation of posterior teeth. These preparation faults must be avoided when
preparing internal crown surfaces with rotary milling or grinding instruments. The instrument shape
forms a specific diameter. It generally has rounded cutting heads, which largely prevent preparation
of sharp preparation margins or pointed cavities. The preparation of unfavourable preparation surfaces involves the danger of milling or grinding unwanted cavities.
Important: If only short clinical tooth stumps remain after preparation you should consider an
alloy based solution in that case, because of lack of retention.
Fillet
rounded cusp!
no sharp
incisor edges!
1.5
2.0
Bridge restoration
0.8
0.8
0.6
0.6
Fig. 1: Preparation guideline for anterior teeth (preparation guideline or hard substance removal in mm).*
Fig. 2: Preparation guideline for posterior teeth (preparation guideline or hard substance removal in mm).*
Suitable preparations
deep chamfer
shoulder preparations
A chamfer about 0.6 mm deep is recommended full ceramic crowns. This type of preparation removes less tooth enamel compared to shoulder preparation and is therefore considered less traumatic.
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For bridge restorations an adequate space is really important. Bridge frameworks must always have
sufficient dimensions. The width of the bridge connectors can often be reduced in the anterior
region in favour of a greater connector height. The question of what spans can be bridged
depends on the selection of the ceramic for the framework.
Contraindicated preparation
flat chamfers
tangential (knife edge) preparation
pointed ends for cusp or incisal edges
bevelling the preparation margin
gutter preparation with outstanding enamel
margins (Fig. 3)
Attention!
Gutter
preparation
Fig. 3*
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Cementation
Building up vital teeth
As a preparative, defects resulting from prior caries or fillings should be filled with an adequate material for building up a stump. This allows to fabricate copings and framework with a similar wall thickness and an even ceramic veneering layer. The dentist should use a filling material with a modulus
of elasticity as close as possible to that of dentine. The filling material does not necessarily has to be
tooth-coloured because of the relative opacity of restorations zirconium oxide. Highly filled composites applied in combination with an appropriate dentine conditioner are most suitable for direct
structuring of vital teeth.
Temporary cementation
Because of their high mechanical strength, zirconium-oxide-based crowns and bridges can be
placed temporarily. In general, temporary restorations should not remain in the mouth longer than
two to three weeks. The dentist should use a cement that does not harden too much. If a cemented
permanent insertion is planned, the temporary cement should also be eugenol-free, such as Prevision Cem from Heraeus.
Building up stumps of endodontically treated teeth
Zirconium oxide has a similar appearance to that of natural tooth substance and it is relatively opaque.
This means that zirconium-oxide-based restorations also can be isnerted on metal root post without
aesthetic problems. Premise that the wall thickness of the framework is not below the recomanded
minimum thickness. Endodontically treated teeth can be restored with prefab metal root post of titanium or individually casted post made out of a non-precious or precious alloy. Alternatively the dentist can use tooth-coloured post, i.e. ceramic root post or even better fibre-glass post. Composite materials are also suitable as filling material for stump build-up.
Final cementation – conventional or adhesiv
Zirconium-oxide-based restorations can be definitively inserted conventionally with zinc-oxidephosphate cements or glasionomer cements and also adhesively with a suitable composite cement.
Because of their high strength, full-ceramic restorations can always be cemented conventionally
without affecting their long-term characteristics.
An essential prerequisite for conventional cementing is an adequate retention and resistance shape
of the ground tooth. Before conventional cementing, the tooth stump must be cleaned as usual and
if necessary parts particularly close to the pulp should covered with a calcium hydroxide preparation
to protect the pulp from the acid constituents of the cement. The internal surfaces of the zirconium
oxide frameworks must be cleaned with grease removers.
Impression
Impression
A wide range of impression materials and impression methods is available for taking an impression of the finished tooth preparation.
A correctly made impression will show the entire region to beyond the
preparation margin in every case.
Fig. 4: Optimum preparation
of a prepared anterior tooth
for impression.*
It is important to represent the preparation margin
correctly in the patient’s mouth before the impression
(Fig. 4). For example, with a subgingival preparation margin, a suitable retraction cord technique
for temporary displacement of the adjacent gingiva
or even electrosurgery is required.
Alternatively, the internal crown surfaces can be
carefully sandblasted with corundum with a small
grain size (50 – 110 µm) at low pressure (1.5 bar)
to increase the surface roughness. However, there
is no general recommendation for this procedure.
Follow the directions of the manufacturer of the
zirconium oxide manufacturer. Cementing with
glasionomer cements is possible for teeth with no
clinically relevant stump discolouration, otherwise
use opaque zinc-oxide-phosphate cements. Adhesive cementation is unavoidable if the stump retention is limited or partial crowns or full-ceramic
adhesive bridges are to be fixed. Unlike porcelain
or feldspar ceramics, etching zirconium-oxide
ceramics does not result in a microretentive surface. However, a suitable cementing composite
forms a secure bond to the prepared stumps.
(Fig. 6, 7).
Fig. 6: Anterior bridge with excess composite inserted
with Panavia F 2.0.*
Fig. 5: Successful impression: the preparation margins
of teeth 44 and 45 are surrounded by a circular
material tab.*
Fig. 7: Anterior bridge after removal of excess
composite in situ.*
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Self-adhesive composites form
a strong bond to zirconium
oxide even without surface conditioning and therefore save
time and are easy to use.
Heraeus recommends the selfadhesive dual-curing composite iCEM Self Adhesive
Opening
1
Rinse
2
Dry
3
Discard 2 – 3 mm
4
5
6
In principle, zirconium-oxideApply cement
Insert restoration
Hold 1 – 2 sec.
based restorations can
also be cemented with any
dual-curing bis-GMA/UDMA
composite. However, this
adhesive technique requires
7
8
9
Remove excess
Light cure 30 sec.
Pressure 2.5 min.
the oxide-ceramic surface to
Fig. 8: Adhesive fixing with iCem Self Adhesive: etching, priming, bonding,
be preconditioned with a suitdesensitisation and cementing in one session.
able silicatisation procedure
to ensure a reliable adhesive
bond. Alternatively, Heraeus recommends conditioning the adhesive surfaces with the zirconiumoxide bonding agent Signum Zirconia Bond. This product with bifunctional adhesion molecules guarantees a secure material bond.
Zirconium-oxide frameworks can be opened without difficulty when the following items are observed:
Preparation of access cavity:
– remove veneer ceramic with a diamond drill
– then perforate the zirconium oxide while maintaining a distance of 0.5 mm to the veneering
ceramic to prevent splitting of the veneering ceramic by overheating
Closing the opening:
– we recommend closing the access cavity adhesively with composite
– for long-term success we recommend using a bonding agent, such as Signum ceramic Bond
Removal
A zirconium-oxide restoration is removed similarly to a veneered-metal crown. Open a gap in the axial
wall from the incisal or occlusal direction with a suitable diamond drill and bend the restoration with
an instrument. This will fracture the restoration and the various parts can be removed. Ensure that
cement residues are removed from the stump in the case of cemented restorations.
Grinding in the mouth
The zirconium framework should be ground as little as possible.
The most suitable procedure depends greatly on the degree of subsequent rework. Wet machining with
a turbine is preferred for major rework (e.g. reduction to the crown margin or reduction of wall thickness). Visual markers are not normally required. Dry machining is the preferred procedure for smaller
and more accurate rework, such as adjustments or grinding at points that require a good view.
Water-cooling must always be used when grinding veneered crowns intraorally to prevent overheating
of the ceramic. Then the surface should always be polished to a high gloss or an additional firing conducted. For exposed zirconium frameworks the surface must always be polished to a high gloss with
suitable zirconium polishers or sealed with a glaze.
Sources
Tinschert, J; Natt, G; Mohrbotter, N; Spiekermann H; Schulze, K A
(2007): Lifetime of alumina- and zirconia ceramics used for crown
and bridge restorations. J Biomed Mater Res B Appl Biomater.
80 (2):317-21
Li, J; Zhang, L; Shen, Q; Hashida, T (2001): Degradation of yttria
stabilized Zirconia at 370K under low applied stress. Master Sci Eng A
297:26-30
Molin MK, Karlsson SL (2008): Five-year clinical prospective evaluation
of zirconia based Denzir 3-unit FPDs. Int J Prosthodont 21:223-227
SSailer I, Féher A, Filse A, Lüthy H, Gauckler LJ, Hämmerle CHF (2007):
Five-year clinical results of zirconia frameworks for posterior fixed partial
dentures. Int J Prosthodont 20:383-388
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Wolfart S, Bohlsen F, Wegner SM, Kern M (2005): A preliminary prospective evaluation of all-ceramic crown-retained and inlay-retained
fixed partial dentures. Int J Prosthodont 18:497-505
Kern M, Wegner SM (1998): Bonding to zirconia ceramic: adhesion
methods and their durability. Dent Mater 14:64-71
Wegner SM, Gerdes W, Kern M (2002): Effect of different artificial aging
conditions on ceramic/composite bond strength. Int J Prosthodont
15:267-272
* Images courtesy of Prof. Dr. J Tinschert, Aachen
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66048548 GB 03.2011 ORT / RHM
In accordance with European Directive 93/42/EEC,
our products bear the CE marking on the basis of their classification.
Contact in Germany
Contact in Scandinavia and
Contact in Australia
Heraeus Kulzer GmbH
in the Baltic States
Heraeus Kulzer Australia Pty. Ltd.
Grüner Weg 11
Heraeus Kulzer Nordic AB
Rydecorp
63450 Hanau
Hammarbacken 4B
Unit 6, 2 Eden Park Drive
cadcam@heraeus.com
SE-191 49 Sollentuna
Macquarie Park NSW 2113
www.heraeus-dental.com
Phone +46 8585.777.55
Phone (02) 8422 6100
Fax +46 8623.14.13
Fax (02) 9888 1460
nordic.dental@heraeus.com
sales@heraeus.com.au
www.heraeus-dental.com
www.heraeus-dental.com
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