Boris Kovachev shows what can be done with an affordable ceramic powder that is ideal for these trying times.
The conundrum
Every laboratory, even with a differentiated list of services, needs a reliable and economic porcelain material. This is for both basic and advanced level of porcelain fused to metal (PFM) aesthetics.
In light of the current financial state around the world and this COVID-19 pandemic, this necessity becomes even more pressing. It raises demand for an easily affordable ceramic powder.
It goes without saying that I myself was until recently on the hunt for just such a material. For it to serve my purposes, the ceramic had to meet certain price criteria. It also had to be very reliable and quite forgiving.
After all, the last thing a dental technician wants is to invest more time in correcting defects.
Over the years I’ve worked with a variety of high-end PFM systems. I have consistently provided my clinical clients with a steadily increasing level of natural aesthetic results. Every time I incorporated a lower price crown and bridge service in my assortment, the same problem arose.
We, humans, are creatures of habit! The same dentists that demanded economic price segment, had grown used to the highly aesthetic results I was providing them with. For many a year, I was using the most expensive porcelain systems available.
A rethink is needed
So I had to rethink my entire porcelain layering perceptions in order to be able to successfully solve this conundrum.
What I found eventually changed my entire outlook on ceramics and aesthetic restorations in general. Even when using the most advanced ceramic materials out there. As I already said – we are creatures of habit. Hence one must sometimes return to the essential basics in order to achieve new development and liberation form popular misperceptions.
I started experimenting with a very sturdy feldspathic porcelain material. The thing that attracted me to this material was the fact that it revolved around a highly proven base material – feldspar.
Now, as I said – my dentist customers had grown accustom to the high-vitality and natural aesthetics of my expensive ceramic systems. I had to find a way to provide similar results with the classically-centered material.
When pondering over the quest at hand I noticed that the only difference between the vast variety of porcelain products was the huge amount of money I had previously paid for all the ready to use effect materials, which suggested domination of the chroma over the light-transmittance.
The said effect materials, unless enclosed in a multi-layer material scheme had a very consistent look. This means that under different view angles, the crowns would look exactly the same.
As we all know in nature nothing is solid colour. Not even the intensive areas in the healthy enamel and dentine. Instead when our patients turn their heads, or face different light (both in composition and intensity), the various zones in the intact natural anatomic crowns are manifested in a completely different way every time – nature’s own kaleidoscope.
Early works of fundamental teachers
Light predominantly controls at least two of the main components of the dental colour. Chroma is just one of the four overall components.
I revisited the early works of fundamental teachers in porcelain. I found the source for that misconception rooted decades ago.
The earlier feldspathic ceramics were saturated but lacked on in-depth translucency. This was due to the early stages of evolution at which the material production techniques had been at the time.
Thus back in the day instructors advised us to use different basic shade materials in the separate aesthetic zones of the crown. Also varying enamel/incisal materials on separate parts of the same crown to add illusion of volume and material thickness.
Because of the solid and consistent saturation of the basic materials these advices were quite useful. They can be applied even today with the most advanced or most basic systems.
Relatively early the manufacturers learned how to control material colour by means of metal oxides. That aspect has always been under control. You are free to use these old and proven layering techniques in your everyday work with all porcelains.
That is, where dentine and enamel shades are saturated and reliable enough for such a zone-oriented layering. But it is the reliability of this approach itself that had put us on the path of chroma-oriented material development.
In order to compensate for the lack of in-depth translucency in the older PFM materials, the renowned instructors used to layer the most translucent/transparent material on the surface.
And although this misconception has long since been abandoned, it has laid the foundations for another lasting tendency, one which is even more persistent than chroma-oriented layering: the idea that we always layer from opacious to transparent in a steady gradient – from the metal support to the finished ceramic surface.
Look to the published work
Famous ceramists around the world have published substantial research on the optical aspects of natural dental anatomy, so we now know that the case in nature itself is not as clear-cut as we assumed.
There are deeper areas within the dental tissues that are more translucent than the superficial ones. It’s that transparency of underlying layers that gives the natural dentition its multitude of appearances under different light conditions.
For me these findings were most liberating. They allowed me to experiment with the order in which we layer the different ceramic materials in untypical manner. These experiments provided me with solutions that redefined my entire concept of porcelain work.
Another object of my admiration, has been the production of beautiful all-ceramic representations of full anatomic teeth. This, I observed on the luxurious pages of the books and publications by great names in dental technology.
During the years I’ve attempted to achieve similar results, trying out every technique for making such sculptures of teeth I could get my hands on.
Gradually I modified those masterful techniques to the level of my own abilities and expertise, in a simple yet reliable procedure. This would allow even a novice to make such anatomic reproduction with ease.
The display of the above mentioned technique provides an ideal canvas on which to demonstrate my concepts. At the same time it gives me the opportunity to share this simplified method with you, the reader. Ultimately, it saves younger technicians the time and nerves I wasted experimenting and biting my nails to the core.
The actual work
All I need to fabricate fully anatomic sculptures of teeth, made entirely out of porcelain, is a porcelain brush, something to mix my ceramic materials on, a towel, an artist’s spatula (used normally for large application of oil paints on canvas) and some paper handkerchiefs (Figure 1).
For mixing porcelain even an ordinary piece of glass would do (but the agate plate seen on the picture is a gift by colleagues from Russia, where I have conducted several courses, so I use it a lot) and the said spatula you can buy cheap at any supply shop for arts and crafts.
I use it because it’s very thin, soft and elastic. It is very convenient in the initial stages of the work process.
For all the aesthetics demonstrated in this article I will be using only three bottles of porcelain. These are Dentin A3, Enamel and clear Transparent. This shows that with multiple layers of reversed order we can achieve most of the effects needed in our daily work.
In addition I will be mixing some chroma material for added saturation in the dental root and cervical areas.
We first need a foundation on which to layer our mixed wet porcelain. This foundation needs to be soft and neutral enough as not to pollute our ceramic. It needs to be easily removable prior to firing. An ideal base is a wet paper handkerchief.
But in order not to make a mess on our work bench, as well as to control the moisture and prevent the water from escaping too quickly, we will use the hankie on top of a double folded towel.
This foundation will be partially saturated with water through the paper handkerchief. It will keep it moist for the duration of our work (Figure 2).
Using an oil paint spatula
The use of an oil-paint spatula was shown to me by a very talented and famous German dental technician. I immediately adopted it for this technique.
Previously, it has been a torture to apply the first large portions of the root and dental core only by means of a brush. It is also convenient for mixing large portions of porcelain, which is why for colleagues who do a lot of long-spam implant based bridges, where they have to reproduce huge volumes of pink tissues, such an instrument is the preferred weapon of choice.
For my first build-up I chose a central incisor. I mixed even portions of chroma-dentine and Dentin A3.
I applied this with the spatula directly on the wet paper towel (Figure 3). Some instructors use their bare fingers to model these initial large portions of the tooth, so I have heard. Or, they hold the handkerchief in their hands instead of placing it on a towel, but have personally been too insecure in such a handling of the wet material.
Instead I roughly compact and give the desired shape of the layered material with the wetted spatula itself and then continue to fine-tune the desired core shape by means of a brush (Figure 4).
In this case, I have formed mamelons directly on the dental core. I have also slightly cut out a horizontal groove with a flattened brush.
So far nothing new
Such horizontal grooves we often perform in our daily porcelain layering.
The reason for that is again found in natural optical anatomy, where we’ve discovered that intact natural teeth in their middle third demonstrate de-saturation, neutral appearance and even ‘dullness’ if you will.
The easiest way to achieve that on a PFM crown is to cut a shallow and rounded horizontal groove in the dentine, which has already been layered over the opaque.
Then fill that with transparent material (here died dark-blue for convenience, Figure 5). You can use shaded transparent materials in such instances instead, to achieve shaded in-depth ‘belts’, while the technique of the buildup remains unchanged.
I have filled the vertical grooves between our mamelons with transparent material, when we need these ‘horns’ more pronounced. The transparent, when locked underneath the enamel, will result in illusion of increased depth.
In the same way it will optically de-saturate and soften the middle third of our crown.
We have all been shown this on training courses, or have read it in a fancy book that costs some 200euro+, so we repeat it over and over again, calm with the knowledge that transparent under the enamel provides depth. How often did we stop and think on the mechanics of this optical composition? Did we ever ask ourselves why this illusion occurs, when the oldest studies, going back to the 1960s, on high-end aesthetics teach us to layer the transparent on top (Figure 5)?
It is important to note…
The simple truth of the matter is that every time we layer a more opacious material on top of another, more translucent one (as with the case of our enamel over a transparent groove-filler), we effectively trap light.
This ‘sandwich’ allows direct light through the top layer, while reflecting parts of it. It absorbs and scatters a further percentage of its rays, while making the said porcelain mass look slightly brighter.
After passing through the more opacious superficial material, the light sinks more rapidly inside the more transparent volume. Thus it makes it visible, adding to the illusion of depth and thickness.
In the transmitted light scenario however, light travels more or less in a ‘reverse’ direction, passing through the transparent, before hitting the enamel (in this case) from within. Then the transmitted light rays shine more aggressively, almost undisturbed inside the porcelain, before ‘crashing’ in the more opacious surface material.
Thus a very useful phenomenon occurs. The visible opalescence of that very same less translucent superficial material increases since it gets to scatter more light than its underlying layer.
In that aspect however, the said material (enamel here) gets to shine, on account of all that scattered light within its thickness, and thus starts exhibiting its own shade more visibly – it shines with its own colour.
How does that help us in our daily work?
Opalescence
When we speak of increased opalescence, most of our colleagues will simply reach for the nearest bottle of opal-material and will just layer it on top. And although most companies create such ceramic masses for a good reason, those do not a panacea make.
They should limit their usage, since if we use them to reproduce an enamel edge, for example, that structure will look exactly the same way viewed under different angles and light.
As we already said, due to their complex structure, all components of the human body, especially the intact natural dental crowns, demonstrate different appearance from varying view-angles and under changing light.
Hence it’s better to have a more natural kaleidoscopic opalescent enamel edges and structures. Rather than the uniform look of a ready to use material.
This feature of our porcelains most of us have already discovered by accident. Likely while still learning on the older feldspathic materials from the 1980s. Every time we’d accidentally apply dentine over enamel, we would get bright, almost chalk-like spots. This is because the old porcelains lacked in-depth translucency.
Nowadays all ceramic manufacturers have drastically improved the aesthetic aspects of their products. This includes translucency on all materials.
This is why I widely use the said hard lessons of the pasts in almost all porcelain build-ups. My restorations have substantially benefited from selective reverse layering of the conventional ceramic masses.
In keeping with all said above, I not only covered the incisal third of the tooth with enamel, thinning it out towards the middle, but also generously extended the material to the cervical area over the approximal ridges of the vestibular surface (Figure 5).
Keep coming back to the Dentistry website and we will run part two next week.
This article first appeared in Laboratory magazine. You can read the latest issue here.
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