A Survival Guide to CAD/CAM Implants and the Latest Crown and Bridge Materials


Article by Chris Hussey as featured in August 2014 edition of Australasian Dentist magazine
No matter your preferred implant system, whether you have invested in an intra-oral scanner or still opt for conventional PVS impressions, if you place or restore implants you can enjoy the simplicity and savings that a Sirona inLab laboratory can offer thanks to the TiBase system.  In this article, I will attempt to clear the fog surrounding CAD/CAM implants.  In so doing, I will discuss how the sheer simplicity of the CAD/CAM option can provide for a stronger, more beautiful and inimitable product at a lower cost to conventional implants made with modified stock abutments.  Critical to this discussion is the necessity to first provide some clarification about the latest materials now available.

 

Modern Crown, Bridge and Implant Materials

The following groups of materials are now commonplace in modern cosmetic implant dentistry:

  1. Glass ceramics;
  2. Hybrid glass ceramics, either:
    1. Enriched with zirconia; or
    2. Comprising of a dual-network of ceramic and polymer;
  3. Translucent zirconia (either monolithic or partially layered with porcelain);
  4. Porcelain-fused-to-zirconia (PFZ); and
  5. Porcelain-fused-to-metal (PFM).

Before we continue… If you are hoping for a “catch-all, one-stop-shop wonder product” that is suitable for all cases, I will have to disappoint you now.  There isn’t one.  All I can do is to elucidate, as concisely as possible in a short document, key materials to add to your implant dentistry arsenal.

For many years now, glass ceramics, particularly of the monolithic variety, have served as the “bread and butter” option for most cases – and for good reason.  They are invariably stronger than PFMs which comprise of a weaker ceramic component that is prone to delamination or chipping.  The absence of metal also allows light to behave in a similar way to natural teeth.  This is particularly important in the anterior region, especially in our beloved sunny country.  Common brands include IPS e.max®, IPS Empress® and VITA™ Mark II for example.

These battle-hardy, time-tested rulers may however soon be unceremoniously dethroned by the relatively recent arrival of their hybrid counterparts.  As discussed in my recent Australasian Dentist article, the zirconia-enriched lithium silicate, VITA Suprinity® has created a new benchmark for ceramic restorations.  It has opalescent and fluorescent properties, is wonderfully translucent, has a 3-point flexural strength of over 494MPa and greater Weibull modulus and dynamic loading scores when compared to lithium disilicate (VITA R&D, 2014).  It is important to note that these ceramic products can be layered with porcelain for enhanced aesthetics which may be essential for some cases.

Some clinicians prefer the incredible reliability afforded by the dual-network structure of VITA Enamic®.  This material comprises of approximately 86 wt% ceramic and 14 wt% polymer, hence providing it with the ability to flex under pressure and withstand enormous loading.  According to VITA (2012), it has a Weibull modulus of 20 and can be milled to outstanding precision.  Furthermore, VITA Enamic® has a “crack stop” function which means that cracks, should they occur, will not continue to run through the restoration to failure.

VITA Enamic® can be stained and glazed with light-cured polymer-based materials or easily polished.  It is important to bear-in-mind that the shade range is somewhat limited however.  The advantages of this material are obvious considering implants.  What better way to protect the opposing dentition than to restore the implant with an attractive and flexible veneering structure that can be easily removed should the need arise?  As pointed-out by Dirxen et. al. (2013), this material is relatively new on the market and long-term in-vivo studies are still in progress.

We are not surprised to observe the rise and rise of the use of translucent zirconia for implant cases.   Quite the opposite school of thought from VITA Enamic®, translucent zirconia can be considered as a metal replacement option; i.e. what the unyielding Empire State Building is to the swaying Burj Dubai.

There are a number of translucent zirconia products now on the market.  We have observed that the translucency between them is in reality quite negligible at best.  That said, they are amazingly translucent for products that boast such incredible strength.  We at Ceramic Studio have opted for inCoris® TZI (developed by Glidewell Laboratories in California and also sold under the name of BruxZir® Solid Zirconia) as it has a flexural strength of up to 1,465MPa which is approximately 300MPa stronger than most of its rivals.

Translucent zirconia can be wonderfully versatile and allows us to fabricate “hybrid designs”.  For example, you have a 13-16 implant bridge in mind with a wish for it to be both highly aesthetic as well as strong (and why wouldn’t you?).  For the scenario’s sake, let’s say the patient is a heavy bruxer.

To achieve a successful outcome you may request for the 13 to have full porcelain coverage, yet be clear in all excursions and for the remaining 14-16 to be made to the full anatomical contour in translucent zirconia, yet have their respective buccal aspects reduced and overlayed with porcelain.  For cases such as these, we can ensure that the porcelain areas are clear in all excursions.  A perfect meeting of strength and aesthetics.

This brings us to layered zirconia.  There are few aesthetic outcomes that cannot be achieved with these restorations, particularly with VITA’s stunning VM®9 porcelain.  The opacious zirconia serves to block-out the underlying metal implant connector and provide a substructure for the porcelain overlay.  Despite their beauty, it is worth remembering that they are susceptible to delamination and chipping like their PFM cousins.

PFMs are still requested on occasion, yet their popularity seems to be waning as clinicians learn of the benefits attributed to more modern materials.  One such benefit is cost as PFMs are far more labour-intensive than their younger rivals.

 

The TiBase System

Now we have been introduced to the key materials that are widely used, we can discuss the simple part.  Sirona has developed a unified method of manufacturing customised CAD/CAM implants from the latest materials for laboratories.    The TiBase system works with Sirona’s powerful and ever-evolving inLab and CEREC software packages.

It is imperative to understand that one does not need an intra-oral scanner to take advantage of this technology.  The majority of our work still originates from conventional PVS impressions.  The impressions are poured and the models are left as solid/un-sectioned before being articulated, equilibrated and scanned using a 5-axis scanner.

The TiBase system is leading the way with CAD/CAM implants.  Some reasons for the global success of this system include:

  • Improved cost-effectiveness for the clinician and patient
  • Implants are packaged and the pricing simplified – packages include the crown and custom abutment or abutment crown, TiBase connector and prosthetic screw, eliminating an additional bill from the implant manufacturer
  • Custom abutments come as standard
  • Greatly reduced turnaround times
  • Access to the latest and most advanced materials
  • Improved accuracy and fits as one would expect with CAD/CAM restorations
  • Torque is applied metal-to-metal and the ceramic components remain in a passive state on insertion
  • Compatibility with the best implant systems on the market, including Nobel Biocare®, Straumann®, Astra Tech®, Biomet 3i™ and MIS® to name a few

So what’s this TiBasey thing then?  The TiBase is simply a metal connector between the implant and the chosen restoration.  During manufacture, the technician will screw the TiBase into the implant replica on the model and place over it a scan body.  The scan body informs the inLab software the precise position, depth, axis and rotation of the implant when scanned.  Some TiBases are made by Sirona and some are made by the implant company themselves.  It comprises of two parts:

  1. The apical part:  This is the variable part that is specific to the chosen implant system and size; and
  2. The coronal part:  This part is specific to the inLab-compatible milling blocks and will either be small or large (depending on the implant).

The coronal part has an anti-rotational notch on it and can only fit into the applicable milling block one way.  When the technician has designed the restoration, the abutment component/abutment crown is then milled from such a block.

The abutment block will either be lithium disilicate (IPS e.max® CAD) or zirconia.  Titanium abutments can be milled, however they are invariably more expensive.  The fit between the TiBase and the abutment block is machined, hence perfect.  These two parts are later lab-cemented together after the necessary processing steps have been followed (i.e. crystallisation of the glass ceramic or sintering of the zirconia and their respective stain and glaze firings).

Your implant may be cement-on or screw-retained.  Screw-retained implants are becoming increasingly popular for cases that have aesthetically favourable access holes.  These can be referred to as abutment or hybrid crowns.  The most popular choice of all is the IPS e.max® CAD monolithic abutment crown.  This is simply a solid mass of 360MPa lithium disilicate that is designed to the full anatomical contour, stained and glazed accordingly, then lab-cemented onto a TiBase.  The result is a translucent, beautiful restoration that is strong, will not delaminate, is highly unlikely to chip and completely blocks out its metal TiBase host.

If the access hole is less favourable, then you may prefer a cement-on restoration.  The most popular choices for this technique are a monolithic VITA Suprinity® or IPS e.max® CAD crown over a zirconia abutment.  The result is aesthetically outstanding.  This combination is suitable for anterior and posterior cases.

If you are impressed by the strength of VITA Suprinity® yet still hold reservations for your 6’6” patient with an extremely heavy bite and love for the noble art of boxing, then you may err towards opting for a translucent zirconia or VITA Enamic® crown over a zirconia abutment.  Should translucent zirconia be your preference, then you may consider requesting a facial reduction and porcelain overlay as mentioned earlier, particularly for anterior implants.

An additional bonus of a custom zirconia or IPS e.max® abutment for the patient is the fact that we also stain what cannot yet be seen.  Some comfort can be found in the fact that the shade of the abutment is sympathetic to that of the crown should the patient’s gum recede later in life.  There would be nothing worse than having the metal of a stock abutment or the bright white of unstained zirconia on show, adding insult to disease or the inevitability of ageing.

TiBases make implant bars a dream for the clinician.  This area is somewhat beyond the scope of this article, however please feel free to call me should you wish to chat about it.

As with all things crown and bridge, it never hurts to ask the technician’s opinion if you are unsure of what materials to choose.  We technicians have the unfair advantage of dealing with a variety of cases on a daily basis and are afforded the opportunity to learn about how far certain materials can be exploited or otherwise.  Plus we like to chat.

 

Conventional or Digital Impressions?

As explained, this technology is completely open to those who wish to take conventional impressions and send them to an inLab laboratory, however there are many benefits to enjoy by going digital.  It all starts at Sirona’s Apollo DI intraoral scanner (pictured) which costs approximately $25,000.  This is suitable for dentists who do not wish to design and mill their own crowns and implants, but simply wish to send digital impressions to their favourite laboratory for manufacture.  It is as simple to use as an iPad, however Sirona provide full training and support with getting you up and running.  Despite being the world leaders for CAD/CAM within our industry, one of the reasons we chose to invest in Sirona equipment is the fact that we own what we purchase – i.e. there are no ongoing annual licensing fees and you are not charged each time something is sent or received via the Sirona Connect portal.

Intraoral scanners are generally a more cost-effective way of operating.  The cost of acquiring one is, in most cases, offset by impression materials, trays, labour attributed to infection control procedures, impression analogues, implant replicas, postage fees, etc.  They are portable and can be wheeled from room to room.  Intraoral scanner users can enjoy the following benefits, amongst others:

  • Greatly reduced turnaround times;
  • Incredible accuracy;
  • The capacity to achieve the perfect bite registration and vertical dimension;
  • Elimination of impression drags;
  • Elimination of outgoing sterilisation procedures;
  • Improved practice/lab communication with real-time feedback;
  • Reduced model archiving (although your inLab laboratory can have them 3D printed if you wish); and
  • Reduced patient discomfort (gaggers).

Taking a digital impression for an implant is incredibly simple.  A reusable scan post is inserted into the implant, then a scan is taken.  The scan post is removed and a second scan is done to capture gingival tissue information.  The opposing dentition is then scanned, followed by the buccal bite registration.  You now have a perfect impression that eliminates any possible variables attributed to an impression analogue moving or rotating in any way.  Technicians also love the fact that they are provided with the perfect bite registration.

When the patient details and material selections are entered, it is simply sent via the Sirona Connect portal and your technician can review it, then commence working on it immediately.  It is a fantastic communication tool as it enables well-informed dialogue between clinician and technician whilst the patient is still in the chair.  There is also an iPhone app that alerts the technician to a new order as soon as it is placed.  The technician can remotely review the digital impressions in occlusion even if he or she is away from the lab (sorry to all you fellow technician out there!).

Another area which may be overreaching for this document is the capacity to order surgical guides with this technology.  This is somewhat more involved however, again, I am more than happy to chat you about this should you wish.

Positive for Australia

The CAD/CAM revolution is incredibly positive for our local industry.  We realise that there is a strong body of Australian dentists who prefer higher-end work that is made from known materials.  Production line technicians from overseas super labs do not have the ability to sit down with a patient and ensure that the shape and shade of the anterior implant they paid good money for is perfect.  As consumer expectations grow, so does our local economy.

The reason I say that CAD/CAM technology is such a positive force is that it better enables Australian laboratories to provide incredibly accurate work from recognised materials with the added benefit of greatly reduced turnaround times.  For example, we have reduced our turnaround time from 8-10 working days to 3-4, with capacity to do same day crowns if arranged.  Furthermore, we are able to provide marginal fits that can rarely be achieved when pressing ceramics.

As far as cost comparisons are concerned, our research indicates that we are only on average about $150 more expensive than most major overseas laboratories per implant for an entire package.  This is because we are able to pass on savings from the fact that we now mill in house, as well as the fact that TiBases are about half the price of a manufacturer’s stock abutment.  Paradoxically, this is by no means detrimental to the implant manufacturers.  Most have embraced this integrated approach as their clients can enjoy the superior products that it provides for and are more likely to place their implants.

 

Finally…

If this sounds in anyway complicated, do not fear.  All the clinician has to do is send impressions either conventionally or digitally and the technician takes care of the rest.  That said, it is worth knowing how it all works as the end product for CAD/CAM implants is generally far superior to those made from stock abutments, plus there are savings to be enjoyed.

If you wish to find out more please feel free to come and see our fully-fitted demonstration room (pictured) for an obligation-free discussion at your convenience about all things crown, bridge and implants.  We have had very positive feedback about this initiative from dentists who have already attended.  Further reading and YouTube videos can be found at ceramicstudio.com.au.  I hope to see you soon.

 

 

Ceramic Studio is a long-established specialist crown, bridge and implant laboratory in Victoria.  Digital impressions can be sent via the Sirona Connect portal by adding “Ceramic Studio Belmont” as a Favourite Laboratory.  Conventional impressions can be sent to the address below.  Please call the laboratory for a price list and lab tickets.  Allow for a 3-4 day turnaround (free Express return delivery for all cases).

Ceramic Studio is an Australian owned company that does not outsource any work.  All cases are made in-house from quality materials that are approved by the TGA and are returned with an Australian Made Certificate of Authenticity.  For further information, you can search for Ceramic Studio on the Australian Made consumer website at australianmade.com.au.


References

VITA Suprinity:  Technical and Scientific Documentation.  (2014).  VITA Zahnfabrik .  Germany.  Retrieved from www.VITA-zahnfabrik.com on 28/01/2014

VITA Enamic®: The Concept.  (2012).  VITA Zahnfabrik .  Germany.  Retrieved from www.VITA-zahnfabrik.com on 18/12/2012

Dirxen C.,  Blunck U., Preissner S.  2013.  Clinical Performance of a New Biomimetic Double Network Material.  Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3807582/ on 22/07/2014

CEREC Doctors.Com.  (2010).  CEREC Outside the Box.  Retrieved from http://www.cerecdoctors.com/blog/view/id/106/cerec-outside-the-box on 25/07/2014

Helsby P.  (2014).  Inside Dental Technology.  Issue 4, Volume 5, April 2014.  Retrieved from https://www.dentalaegis.com/idt/2014/04/embracing-the-digital-movement on 25/07/2014

Sirona USA.  (2014).  CEREC Chairside Solutions.  Retrieved from http://www.sironausa.com/us/products/digital-dentistry/cerec-chairside-solutions/?tab=936 on 25/07/2014

Images courtesy of Sirona (2014)