inCoris TZI Monolithic Zirconia: From a Laboratory Perspective


Article as Featured in the December 2013 Edition of Australasian Dentist Magazine

During my long career as a ceramist, I have observed the trends of many different dental materials as they progress through their respective product lifecycles.  Few have triggered my interest like inCoris TZI.  I have observed the popularity of this incredibly strong and surprisingly translucent zirconia product grow exponentially, far exceeding my own expectations.

In this article I will attempt to explore the reasons why this material is making such an impact within the crown and bridge market.  I will also endeavour to answer the most common questions concerning the product as I do so.

For decades, PFM crowns have enjoyed their comfortable place in the market, being the restoration of choice for the majority of clinicians.  I found it very interesting to observe the popularity of PFMs freefall suddenly when IPS e.max® was first introduced to Australia.  Now I am noticing a new noteworthy market trend.  Indeed, week-by-week I have observed more and more dentists start to favour inCoris TZI for cases that would ordinarily be reserved for PFM and full gold crown restorations and, less frequently, even IPS e.max®.

So what’s the big deal?  From discussions had with our clients, it seems that what first encouraged them to make the switch is the fact that preparation clearance and marginal thickness have now become of lesser consequence.  Some were also pleased with the fact that they are not required to change their methodology in that conventional cementation techniques can be used.  For others it was simply the fact that this advancement in technology comes with a more agreeable price tag when compared to PFMs, with the added security that the restoration is unlikely to ever fail.

It is important to understand that not all monolithic zirconia products are alike.  Indeed, in some cases, it is like apples and oranges.  It is the flexural strength of a product that sets aside the leaders from the followers.

Some monolithic zirconia products have flexural strengths that fail to exceed 1,100MPa.  This is very good I might add.  By comparison IPS e.max® pressed ceramic, considered to be a very strong all-ceramic material, has a flexural strength of over 400MPa.  inCoris TZI however has a flexural strength of up to 1,465MPa and is considered to be the strongest of its kind; so much so, that it is considered as a metal replacement.

For those of you concerned about what this incredible strength might mean for the opposing dentition, please note that the glaze layer plays an important functional role in preventing damage.  This factor, combined with the technician’s skill to provide for the appropriate occlusal contact, will ensure that the opposing dentition is not placed at risk of fracture from excessive masticatory forces.

Some may better recognise the material’s sister brand, BruxZir® Solid Zirconia, which we first offered before commencing milling in-house.  For the avoidance of confusion, they are the same material made by the same manufacturer in California, Glidewell Industries.  Interestingly, Glidewell Industries conducted a “hammer test” which I have posted on my blog via our website.  The unapologetically frank and somewhat draconian experiment showed BruxZir® Solid Zirconia crown being driven into a piece of timber by a conventional hammer.  The crown remained fully in-tact, whereas its PFM counterpart was mostly reduced to dust.  I for one found the experiment far more entertaining than the agreeable charts and numbers.

As it is ever more important to understand where your restorations are being made these days, you will be pleased to know that an inCoris TZI crown does not leave the laboratory during its manufacture.  The crown is CAD designed, milled and sintered in-house before being stained and glazed as appropriate.  The result is an incredibly strong crown that has a “CAD/CAM” marginal fit, optimal occlusal contact points and very good aesthetics.  Incidentally, it is possible for us to start and finish the entire process of manufacture in a single day.

It is understandable that some clinicians are happy to continue to fit PFMs for reasons of their own, or are just apprehensive to try a new type of restoration.  However, one may want to first consider the following advantages that inCoris TZI has to offer:

  1. Greater freedom in your preparation:  Feather-edge margin types can be prepared should the need arise and minimal clearance can be afforded (as thin as 0.5mm occlusally);
  2. Reduced risk of failure;
  3. No risk of delamination;
  4. Conventional cementation techniques can be used;
  5. Ideal for bruxer patients and bridge cases (up to a full arch);
  6. A safe choice for implant cases; and
  7. Cost effectiveness.

Delamination can affect any crown that is built up with porcelain, such as PFM, conventional zirconia and pressed ceramics that are made by this method.  This is an important consideration for those requesting built up zirconia crowns.  Where the zirconia coping is extremely strong, the porcelain overlay may only typically be between 95-110MPa and hence has a greater chance of fracture or chipping.  This is where monolithic restorations such as inCoris TZI and certain pressed ceramics have an overall structural advantage in that they cannot delaminate.

The strength of inCoris TZI does however provide for a trade-off.  Although when compared with most other products of its kind the material exhibits superior translucency, the fact remains that is still somewhat opaque as one would expect of something so dense.  However, this limitation can easily be accommodated for posterior restorations where translucency is a less significant factor.

Notwithstanding this important consideration, I would like to discuss the successful outcome of the largest monolithic zirconia case that we have had the pleasure of making.   Recently our laboratory constructed a nine unit monolithic maxillary bridge spanning 14 to 25.  The outcome was indeed more than impressive despite the inherent opaqueness of the base structure if compared to IPS e.max®.

I believe that the overall success of the final aesthetic can partly be attributed to there being no direct comparison of translucency with adjacent dentition.  This factor allowed the technician to create a consistent effect over the arch.

Ordinarily, I would recommend IPS e.max® for anterior restorations, however in this instance, a full monolithic structure provided for an excellent outcome.  Furthermore, the patient and dentist are instilled with confidence that the bridge is highly unlikely to fail.

We are continuing to trial other types of monolithic zirconia products at Ceramic Studio for the purposes of ensuring that we are able to offer the latest and greatest for our clients.  I will report on our findings within my blog which can be found at ceramicstudio.com.au for those who are interested.

I hope that this article provided a little food for thought for your next crown preparation or implant case.  I am always happy to have a chat about new technologies or the particulars of any upcoming cases, so please feel free to contact me at the laboratory on (03) 52 44 4545 or visit ceramicstudio.com.au for further information on new crown, bridge and implant related materials.

 

Mike Hussey

Director, Ceramic Studio

 

Note:  The bridge featured was designed at Ceramic Studio and milled by Stoneglass Industries in NSW prior to Ceramic Studio acquiring the equipment to do so in-house.  It was then finished at Ceramic Studio prior to being fitted.  The bridge was milled from BruxZir Solid Zirconia, also known as inCoris TZI as branded by Sirona Dental.