​ZIRCONIA CROWN: MAKING YOUR CROWN SELECTION BETTER!

24/11/2022

After teeth extraction or loss of teeth due to trauma, accident, underlying pathology, etc there comes the main role of dentist in guiding the patient better for esthetic correction and appropriate dental crown selection.

The patient satisfaction and the acceptability are the two primary factors which influence the outcome of the dental treatment.

The demand of zirconia crown is increasing due to its excellent properties like hardness, marginal fit and bond strength.

What is the meaning of zirconia and from where does it came?

Zirconium word is derived from Arabic word “Zargon”. This further comes from two Persian words Zar (Gold) and Gun (Color). German chemist Martin Heinrich Klaproth first identified zirconia in the year 1789 after heating some gems. Swedish chemist Jons Jakob Berzelius first isolated it in 1824.

9 Reasons why zirconia crown is the choice among the patients today:

There are number of clinical reasons as to why zirconia crown is the material of choice. Some of the points are listed below:

  • One of the main reasons for choosing zirconia teeth is its low corrosion potential, low thermal conductivity, excellent compatibility with the biological tissues and a good radiographic contrast. Due to these factors, it meets the functional needs as its mechanical properties which is the highest reported ever for any dental ceramic.
  • It satisfies the esthetic needs of the individual.
  • Zirconia has fracture resistance value more than twice higher than alumina as investigated by Yildirim et al 2003.
  • Zirconia tooth crown has improved aesthetics and it has the capability to mask dark substrates with excellence in opacity. This is also due to its grain size which is greater than the light length.
  • Comparing the biocompatibility properties, zirconia is more enhanced than titanium.
  • The bacterial adhesion is low in zirconia constituting, 12.1 % while it is higher for titanium, 19.3%.
  • The inflammatory reactions around the crown placed are the most important considerations while placement. Zirconia teeth causes less inflammation than titanium.
  • Zirconia is a self-regulatory material.
  • Zirconia tooth crown have 4.5% chipping rate after 5 years.
  • The rate of satisfaction is higher in patient with zirconia tooth cap.
  • In zirconia teeth, no caries and adverse soft tissue reactions are observed around the teeth.

Knowing about the structure of zirconium:

Zirconia is a promising base material and has excellent material properties, one of the most important is transformation toughening. This property was first reported in 1975.

Pure zirconia is monoclinic crystal at room temperature and it is transformed to tetragonal on heating to 1170 °C.

Zirconium oxide matrix can be toughened with alumina particles which leads to formation of alumina toughened zirconia (ATZ). This has versatility of applications.

Considering ATZ, 20 wt% alumina, is basically the most optimal composition while considering its use for dental application. In correspondence to toughness properties,maximum fracture toughness is 7.45 MPa m1/2 and Vickers hardness is 16.05 GPa.

 ATZ has superior esthetics as they are naturally white in colour and the surface finish obtained is excellent. It also has highest flexural strength which ranges from 1800 to 2400 MPa at room temperature.

 Properties of zirconium:

  • Zirconium dioxide or zirconia  is a white crystalline oxide of zirconium.
  • pure zirconium oxide does not occur in nature
  • It Has Chemical And Dimensional Stability.
  • It Has Properties Similar To  Stainless Steel Alloys So It Is A Suitable Ceramic Biomaterial.
  • Zro2 Has Three Allotropes, Monoclinic, Tetragonal, And Cubic Phases.
  • Excellent Esthetics.
  • Biocompatible.

Do you know the important Types of Zirconia in Dentistry:

It is important to know that there are many types of zirconia available. But in dentistry there types of zirconia are the most prevalent. They are:

  • Yttrium cation-doped tetragonal zirconia polycrystals (3Y-TZPs). It exhibits better mechanical properties due to its property of transformation toughening.
  • Magnesium Cation-Doped Partially Stabilized Zirconia (Mg-PSZ).
  • Zirconia-Toughened Alumina.

Applications of zirconia crown in dentistry:

  • In The Framework of All Ceramic Crowns And Fixed Partial Dentures, Implants, Abutments, And Brackets.
  • Anterior Teeth Due to Excellent Esthetics.
  • Posterior Teeth Due to Mechanical Properties.

Zirconia crown and brands:

In different types of zirconia crown, Cercon and Lava  are the best quality zirconia crown available.

There is only one commercially available for dental practice, which is In-Ceram zirconia. Is the one commercially available in dental practice.

Denzir-M is commercially available for dentistry is manufactured by fully sintered zirconia block.

If you want to choose crown for single tooth, choose Zirconia. Know the reasons why?

  • Esthetic satisfaction.
  • Success rate is 93 %.
  • Meet  Mechanical Requirements.
  •  Toughness Higher Than 6 Mpa.
  • Strength Is Greater Than 1,000 Mpa.
  • Good Marginal Adaptation
  • The survival rate of zirconia is good and  similar to  metal ceramics.
  • Excellent  biocompatibility and tissue response.
  • Non toxic to gingival fibroblast cells.
  • No adverse reaction in powder form and dense ceramic form.
  • Implant-Supported Y-TZP-Based Crowns Showed Survival Rates Of 95.9% For Tooth-Supported Crowns And 97.1% For Implant-Supported Crowns.
  •  No fracture or failure.
  •  A single porcelain-fused-to-zirconium dioxide has survival rates 92.7 to 100>#/span###
  • Studies have reported no chipping of zirconia single crows.
  • Restorations made from graded glass–zirconia are more resistant to sliding-contact damage than the current porcelain veneered zirconia systems, thereby averting chips and fractures of the porcelain veneer.

Cementation of zirconia:

Cementation of zirconia requires the resin bonding between tooth and restoration. This has important role in retention, marginal adaptation and fracture.

  • No need of pre-treatment is required for cementation of zirconia. This is because zirconia has high flexural strength.
  • Glass ionomer and resinmodified GIC are easy to use and preferred.
  •  zinc phosphate, GIC, resin-modified GIC, and resin cements are the materials of choice.
  •  Commonly used are resin-based composites. The resin bonding between a tooth and the restoration is advocated for improving the retention, marginal adaptation, and fracture

Do you know the applications of ATZ in dentistry?

These are the most promising in orthopaedic implants and posterior FDPs which largely owe to its properties.

3Y-TZP: The advancement in zirconia crown.

3Y-TZP stands for 3 mol % yttria stabilized tetragonal zirconia polycrystal. It is capable of meeting all the key requirements of patient satisfaction as summarised below:

  • Comfort
  • Functionality
  • social aspects
  •  appearance

These are formed from partially sintered blanks as produced by  CeramTec.

What is the main factor that impacts success of zirconia crown?

Marginal adaptation is required for success of dental prosthesis. When inadequate, it causes plaque accumulation and microleakage.

Microleakage is related to infiltration of bacteria, endodontic inflammation and periodontal diseases.

Drawbacks of zirconia crown:

  • Failure rate recorded as 9 %.
  • The graded glass–zirconia approach has drawback of chipping and fracture of the veneering porcelain.

What do market suggest for zirconia?

There is growth of market for dental implants.

There is large proportionality of dental implants made with monolithic zirconia and that is also forecast to grow. For dental implant in US, the total dental implant market made up by zirconia implants will rise to almost double by the year 2024.

Do you know the link between CAD/CAM technology and zirconia teeth?

CAD/CAM stands for Computer-Aided Design/Manufacturing. In this, the tooth restoration model is prepared in software. The technique is very advantageous in impression-making and save time and provides human error free impression.

CAD/CAM technologyimprovesthe marginal adaptation of zirconia crown.

Furthermore, this attribution plays an important role in the dental ceramic fabrication process and increase the reliability for the patient.

Zirconia crown facts: Know these before you choose a crown

  • Zirconia cap have fewer complications than all ceramic crown.
  • Zirconia is inert and has no adverse reaction with the oral environment.
  • The success rate of zirconia tooth crown is good.
  • Single zirconia crown are best for single teeth.

Take away points:

  • The survival rate of zirconia crown is reduced to 74 % as a result of endodontic failure.
  • Type of luting agent affects the retention of zirconia crown.
  • zirconia teeth are a promising alternate to metal crowns.
  • Overall, Zirconia have a good clinical performance and they are more reliable.
  • Good oral hygiene and regular dental follow up increase the outcome of zircoia dental crown.
  • Zirconia can be used in the posterior teeth as it can withstand physiological posterior forces.
  • The mechanical properties of zirconia are superior.
  • Non-veneered zirconia should be avoided due to interaction with the oral environment.
  • Zirconia–porcelain interface should be considered due to potential of crazing and chipping during function.
  • Zirconia has thermoconductivity less than other framework materials.
  • Zirconia esthetically better than metal and may be too white and opaque.
  • the bond strength of colored zirconia is lower than non-colored zirconia.
  •  Ceramic crowns with composition of zirconia, monolithic zirconia crowns, are not used in clinical practice mostly. The main reason is  absence of a sound standard  and there are chances of wear of opposing teeth as the zirconia is hard.

References:

  • Soleimani F, Jalali H, Mostafavi AS, Zeighami S, Memarian M. Retention and Clinical Performance of Zirconia Crowns: A Comprehensive Review. Int J Dent. 2020 Oct 15;2020:8846534. doi: 10.1155/2020/8846534. PMID: 33123199; PMCID: PMC7584951.
  • Daou EE. The zirconia ceramic: strengths and weaknesses. Open Dent J. 2014 Apr 18;8:33-42. doi: 10.2174/1874210601408010033. PMID: 24851138; PMCID: PMC4026739.
  • Alfawaz Y. Zirconia Crown as Single Unit Tooth Restoration: A Literature Review. J Contemp Dent Pract 2016;17(5):418-422.
  • Zirconia in dental prosthetics: A literature review. JonathanGrech et al.
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