By Chris Hussey
Dental Ceramist / Sirona CADCAM Key Opinion Leader Ceramic Studio
There are a plethora of factors that influence the final aesthetic of a crown and bridge restoration, hence your patient’s satisfaction. The unfortunate fact remains that, no matter how brilliant your clinical work is, your patient will usually only care about what they can see at the end of the day. If the central crown they have saved for is too opacious, too stark, too dark or, in some cases, too idealistic when compared to their natural teeth, then today’s discerning consumer is likely to let you know about it.
In this article I will discuss how to achieve the best aesthetic result possible for your patient should shade-taking be conducted in-house. In so doing, it is imperative to discuss key considerations, including:
- Shade guides
- Communicating with your technician
- The preparation, materials and translucency
- The stump shade
- Laboratory shade-taking
- Human limitations
- Shade Guides
Shade guides are obviously your primary reference tool to communicate with your technician. Many clinicians are accustomed to using the VITA Classical A-D shade guide but may be somewhat reluctant to pick up the VITA System 3D-MASTER guide (the 3D system). I am given the impression that this is usually due to lack of familiarity with how it works.
I am certainly not against the A-D system, however it is somewhat limited and can be easily misinterpreted. What I mean by this is that some groups have a wildcard that seemingly has no place amongst its peers. For example, group A’s chromatic scale consistently increases until it reaches A4, which has nothing to do with A1- A3.5. A4 suddenly introduces grey and a significantly deeper value of red. In fact, I would argue that it would be more suited to group D (reddish-greys) than group A.
Furthermore, we are seeing more and more patients with bleached teeth. This revelation is casting the A-D system into yesteryear as the lightest it goes is B1, which is a very yellowish colour, not suited to the glamorous amongst us.
Mastering the 3D system can be highly useful, particularly if you are requesting an anterior restoration. The art of balancing particular hues can lead to the aesthetic success or otherwise of your restoration. In my experience, these are grey, red and yellow. I still find it amazing how a crown may suddenly “disappear” when a particular blend of grey is applied during a follow-up shade consultation with a patient.
The 3D system is a fantastic tool to help you identify such hues in your patient’s natural dentition. VITA have designed the guide so that one first selects the apt group. In the middle of groups 2-4 are “balanced” tabs which are first compared to the subject teeth. On so doing, the question of whether or not the patient shows more red or yellow may start to become more apparent. If you think more red is necessary, go to the tabs to the right. If you think more yellow is necessary, go to the tabs to the left.
Identifying greyness is a little trickier. As a rule, groups four and five are the “grey shades”, however grey comes in to play in certain tabs in the O’s, 1’s, 2’s and 3’s. 1M1 for example is a reddish, greyish, creamy shade. 3M1 is also quite grey. My point being is that when you first look at your patient and believe him or her to have somewhat grey teeth, it may be prudent not to immediately jump to group four but to consider lighter groups if appropriate. Instructions on how to use the 3D system can be found at vident.com.
It is true that as one becomes more familiar with the 3D system, one will start to go immediately to a given shade tab, however it is probably good practice to follow the suggested steps until such time (remember when Neo first stopped the bullets in The Matrix…). A systematic approach will aid in reducing the chance of the incorrect shade being selected due to the mind’s belief overruling the eye’s account. I will discuss this further on. Guides are what they are: guides.
What I mean by this is that your patient’s natural teeth may not correspond to any of the tabs. In fact, this is commonplace. There should however be the closest tab. Once this base reference is identified, there is nothing stopping the clinician from exploring further. For example, one may request a “4M1 but with a little less red”. If you have a want, your technician will likely have their own techniques for providing.
Painting the Picture for Your Technician
It is not an overstatement to compare natural teeth to the works of masters of colour such as Renoir or Turner. The more you look at them, the more you see, not unlike gazing into a polished opal. In filling out a lab ticket for your technician, what you are effectively doing is describing a unique masterpiece to a blind person.
One of the first lessons I was taught when studying fine art ended up being the most important lesson of all; “transpose what you see, not what you believe you see, nor what your prejudice imposes upon you.” This approach will ensure that you do not miss all the perfect imperfections that make a tooth real. First year art students are often instructed to practice sketching whilst only looking at their subject and not their canvas. The same approach can be applied to shade taking: what is it that you really see?
With this philosophy in mind, one still needs a practical approach to recording such information chairside. This can effectively be achieved by dissecting the desired restoration. During an initial shade consultation, I commonly adopt the below systematic approach.
Middle: Obtain a base by selecting the very middle colour without being too heavily influenced by the cervical area.
Cervical: Select the appropriate shade for the cervical area, noting whether it is for the cervical half, third, quarter, fifth, etc. Also taking note whether this is a gradual or sudden blend with the middle shade. If the root is to be exposed, what shade should it be?
Interproximal: This can sometimes be quite important so you may also wish to sketch where it is required and in what shade.
Incisal: Does the incisal edge exhibit a bluish or greyish translucency, or a combination thereof? Does the middle colour run straight to the incisal?
Occlusal: Does the patient have any fissure staining? Is it brownish, yellowish, etc.? If wear facets are applicable, what shade do they exhibit in their centre?
Special characterisations: Is fluorosis present? If so, where? Would incorporating age cracks or striations aid in concealing the restoration? If so, consider where they should run from and to, how many would be ideal and describe their colouration (i.e. yellow, brown, reddish-brown, etc.).
Translucency (discussed further below). With this method it is worth considering taking the time to look away, and/or closing your eyes between each stage for the purposes of “allowing your eyes to adjust”, so to speak. I will explain why later on.
Preparations, Materials and Translucency
Optimal shades are the child of optimal preparations. Insufficient reduction will often provide for a lifeless restoration. I will not go into the age-long debate between clinician and technician regarding reduction, however I am comfortable in affirming that the preparation thicknesses suggested by material manufacturers are critical to the success of the overall aesthetic.
There is no end to a technician’s greediness towards a large healthy shoulder and generous occlusal reduction. This enables us to manufacture a crown with enough ceramic material to allow for an accurate shade, as well as the obvious considerations such as strength and more attractive morphology. Crowns tapering towards a feather-edge margin will start to lose their lustre towards the cervical. That said, I acknowledge that a dentist can only give what they can in some instances. Where sufficient clearance is just not possible, zirconia can sometimes be a saviour. In brief, zirconia products are categorised as layered, translucent monolithic or layered translucent monolithic. Layered zirconia comprises of an opacious coping on which porcelain is applied, much like a PFM. Many, including myself, would argue that these have more “life” than a PFM and can serve to block out a dark preparation quite well (unless the coping is very thin).
Translucent zirconia is very much its namesake. Although the translucency is very impressive for a product of such incredible mass, do not expect the lustre of a glass ceramic. It can be your best friend in the posterior region however. Porcelain can be applied to translucent zirconia to provide for hybrid designs. This way all biting forces can be exerted on monolithic zirconia yet the restoration can be enhanced by facial porcelain layering that remains passive. This is fast becoming the most popular option for bridge cases.
I have found that few clinicians I have spoken with are aware that their favourite glass ceramics, such as IPS e.max® and VITA Suprinity®, are available in high or low/moderate translucencies. This can be quite important in achieving the best result for some cases. Sometimes it is obvious whether your patient’s natural teeth have a high or low opacity, however there are other points to consider as far as translucency goes.
Low translucency might be requested in instances where you are unable to afford your technician the optimal labial reduction, or your patient may have a particularly dark preparation. In instances where this is the case, however it is critical to have a translucent incisal edge, you may consider requesting a cut-back restoration. This is where the majority of the crown is monolithic, yet the incisal third is reduced for porcelain layering.
If you are looking to marry a modern restoration with existing old ones, there is an option. A few of our clients have provided feedback to suggest that a low translucency VITA Suprinity® can blend in very well adjacent to old and tired looking PFMs, yet still look significantly more natural.
High translucency glass ceramics can look very natural indeed. This option will serve you well as a “bread-and-butter” for want of a better phrase. If you want to bring a (positive) tear to your patient’s eye when fitting your next multiple upper anterior case, I would strongly suggest this choice. High translucency crowns provide for a stunning aesthetic, hence that wow factor that will motivate your patient rave about you on social media.
For further information regarding preparation thicknesses for your preferred material, please contact our laboratory so we can mail you a clinical guide. I find the IPS e.max® Clinical Guide to be very comprehensive and provides answers to many of the questions I am asked regarding glass ceramics.
Don’t Forget the Stump
The stump shade can dramatically affect the shade of the fitted crown. Without a stump shade your technician is flying blind when staining your restoration. When you take the patient’s shade, it is done against existing teeth or fitted restorations with their own uniquely coloured substructures. It stands to reason that the case is likely to be more successful with this reference.
Your technician is likely to have a “stump shade kit” of sorts. These kits contain a light-curing composite that the technician uses to manufacture an artificial die from the shade selected by the dentist. Clever isn’t it? We like to use VITA SIMULATE Preparation Material which allows us to create a die from six different 3D system shades.
Laboratory Shade-Taking
Of course if time and geography permits, you may opt for your technician to take the shade. There is merit in having the person who manufactures the restoration gaining an overall appreciation of the natural dentition. Technicians have an unfair advantage in being having to deal with the subtleties of shades and special characterisations on a daily basis.
It is best practice for a patient to attend the lab for two consultations before issue. The initial consultation will allow the technician to take the relevant information to take the restoration to an almost-finished state that is usually unglazed. We have found that some patients tend to communicate more openly about any particular anxieties or desires concerning their work with us as technicians as opposed to their dentist, despite how approachable they may be. We often hear phrases such as, “I didn’t want to bother Dr-so-and-so…” before sharing a wealth of bottled-up thoughts. After all, the very environment of the average practice is not conducive to the shy from opening up. One is generally whisked into a sanitised room and promptly laid horizontal before another’s hands are placed within the mouth. A slower and more vertical experience with a person without an intimidating title may be more conducive to a patient opening up.
A follow-up appointment will afford your technician the opportunity to make all those minor alterations that make a crown disappear if required. It is highly recommended that the patient first attend the practice to have the temporary restoration loosened or removed prior to attending this appointment.
Although it may seem somewhat disruptive to your patient to request that they attend the lab twice, we are often told of how impressed they are that the dentist and technician alike are paying so much interest in their work. The correct result may mean more to them than they let on (yes I am referring to the tough guys out there!).
Furthermore, it is a good opportunity for the technician to explain the advantages of the chosen material. Patients are also often excited to see crowns being computer-designed and milled or porcelain being applied. It can be a great way of adding value to the consumer experience at no extra cost.
Human Limitations
It is true that your beliefs and memories play a significant role in how your brain interprets what is seen. An appreciation of this is very important when taking shades.
When comparing your shade tab against natural teeth, after a while it can be possible for you to actually start to believe that your selection is correct although it may be far too light or yellow, etc. If your eyes have been alternating between the shade tab and the teeth for an extended period of time, taking the time to look away and/or closing your eyes for a few seconds before looking back again can pay dividends.
Beware of chromatic induction. This is a phenomenon whereby the colour appearance of light is altered by introducing a second surrounding field (Shevell and Wei, 2000). It is worth bearing-inmind that grey can appear reddish or greenish when viewed within a green or red surround respectively (DeValois and Webster, 2011).
Yes, you’ve guessed it, what I am on about is lipstick or naturally deep red lips. This could cause one to incorrectly select the tabs to the right of groups two, three and four in some cases. I have created an example of chromatic inception below to show how significant this effect can be. You may be surprised to learn that the circles are all the same shades of grey, yet they appear quite different. Knowledge of any colourblindness is also important. This is undoubtedly the most sensitive topic to discuss. Between 7-10% of males on average are red-green colour blind. It may not be the end of the world if you fall into this category. It may be worth asking your dental assistant to play a more active role in shade taking. The adjacent link is to an Ishihara colour test if you are in doubt.
I realise that some of what was discussed within this article may be old news to some, yet I hope you may have taken away something from it. I am always happy to chat about material selections for your upcoming cases, or anything else should you wish to do so. The tech-savvy can find me on LinkedIn.
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