MATERIALS
Zirconium | Titanium | Chrom Cobalt | Ceramics
ZIRCONIUM
¿Does your crown have a dark line near the gumline ?
Does your crown look less vibrant in color as compared to your natural teeth ?
That´s because the metal underneath the porcelain is too opaque to emit the natural light waves as your natural teeth in terms of optical translucency.
Dental zirconium is a synthetic diamond based porcelain material that offers the highest bio-compatibility , esthetics and strength of all dental materials.
Patients now have a choice of a material that is esthetic , strong , pure , bio-compatible and capable of being used for single and long span dental bridgework.
Zirconium has the following superior characteristics that make it the most ideal material available :
- Excellent biological compatibility , absolutely bio-inert.
- Outstanding physical and mechanical qualities.
- Hardness ( Vickers ) 1200 HV.
- Compressive strength 2000 MPa
- Bending strength 1000 MPa.
- Modulus of Elasticity 210 GPa.
- Tensile strength 7 Mpavm.
- Absolute corrosion resistance.
- Very small particle size.
- Extremely high density.
- Porosity 0 %
- Purity 99,9 %
- Translucence of the framework material makes excellent cosmetic results possible.
- Zirconium is manufactured and optimized industrially so that the material qualities remain unchanged through the complete production chain.
- Optimal material for crowns and bridges : tasteless , radiopaque , no pulp irritation because there is no need to use adhesive cements and minimal invasive preparation by dentist
Zirconium oxide ceramics primarily stands out due to its high crack resistance. Crack resistance is the resistance with which the material counteracts the spreading of cracks. If a material is stressed, it usually comes to excessively high tension within a defect area ( pores , surface deficiencies , cavities ) or it cracks. While with metals under high tension in the area of cracks , plastic deformation appears and the top of the tension can be reduced by rounding the cracks ; in ceramics due to missing plastic deformation possibility the cracks continue to grow. The unusual feature of zirconium oxide ceramics in comparison with other ceramics is that at the appearance of a high tension area a transformation of the crystal structure can take place. This process is also accompanied by a volume expansion. By this volume increase it builds wedges in the crack and therefore it reduces the continuation of the crack.
In connection with the tensile strength there also stands the characteristic of bending strengths. While conventional glass ceramics show results of 100-200 Mpa and aluminium oxide ceramics lie in the area of 400-600 Mpa , zirconium oxides reaches a bending strength of over 1000 Mpa.
Because of the high tensile strengths exhibited in test results, it is now possible to fabricate posterior bridges with zirconium oxide. Further decisive advantages are its high resistance to corrosion; stability to hydrolysis and its high biocompatibility in comparison with other ceramics makes this material ideal for restorative dentistry.
TITANIUM
Is a chemical element, in the periodic table it has the symbol Ti and atomic number 22. It is a light , strong , lustrous , corrosion resistant transition metal with a white silvery metallic color. Titanium´s properties are chemically and physically similar to zirconium.
Our laboratory boasts a 10 year experience in processing tooth replacements generated from titanium :
- It is the best anti-allergic element. Its qualities supersede those of any gold alloy by 10 times. It is not only its price which is favourable.
- Being a precious metal alloy, it does not trigger allergic responses.
- It is resistant to corrosion.
- It does not leave a taste in the mouth.
- Tissue friendly material.
- It is neutral with already existing tooth replacement in the mouth.
NON PRECIOUS ALLOYS
CHROM-COBALT; the non-precious metal alloy for metal-to-ceramic work free of nickel and beryllium.
- Extremely corrosion resistant through optimal interaction of the essential elements chrome and molybdenum.
- Biocompatibility certified by neutral institute.
- Low thermal conductibility.
- Great strength at any maintainable span.
- Secure bonding with ceramic.
COMPOSITION :
Co 64 %
Co 21 %
W 6 %
Mo 6 %
Si, Mn each 2 %
CERAMICS
The dental ceramic gives you the unique blend of fluorescence , opalescence and chroma, providing superior uniformity that allows you to match shades perfectly regardless of the substructure.
Issues Facing Ceramics as Dental Restorative Materials
The aim of this paper is therefore to review the role of ceramics in dentistry. The first consideration is why use ceramics. The reasons are as follows:
· Biocompatibility
· Aesthetics
· Durability
· Relative ease for customised units.
Biocompatibity
The biocompatibility issue is essential to prevent adverse reactions within the patients. The dental ceramics in use today have relatively low firing temperatures, usually greater than 900°C and are resistant to dissolution in the mouth. Formulations have been developed with firing temperatures as low as 640°C, however, these materials tend to show considerable surface degradation in the oral environment and hence are not useful.
Aesthetics
Ceramic materials have long been admired for their aesthetic qualities. The use of dentally coloured glasses can provide replacement structures that can be made to imitate tooth structure in both colour, translucency and response to different lighting sources.
Durability
Durability is an area that has led to considerable research for ceramic systems that can provide individually constructed restorations, that are small, unique, inexpensive and will be subjected to cyclic loading in wet and sometimes abrasive conditions. The critical problem for all ceramic materials, not the least those used in dentistry is the huge difference in theoretical strength, based on the covalent nature of their structure, and the usual strengths found in general use (7000-70000 MPa versus 7-700 MPa). This was originally determined by Griffith, who reported that the theoretical strength for all solids could generally be regarded as a constant with a value approximating E/10.
The advances in industrial ceramics for such conditions have been remarkable to say the least, in recent decades. However, nobody is going to allow their front teeth to be restored with a ceramic that is dark grey, black or opaque white. The advances in industrial ceramics have included improvements in fracture toughness, wear resistance, machinability, solubility, hardness and flexural strength. With the exception of hardness, these are the same improvements that have been sought in dental ceramics. Another major requirement apart from aesthetics is that the ceramic not be too hard otherwise abrasive wear of the opposing natural tooth will be too severe.
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