Be warned that this is a technical description of shade matching within dentistry. If you have any questions from this, feel free to give us a call at Marylebone Smile Clinic.
The colour match of a single front tooth represents one of the more challenging situations in aesthetic treatments. The reasons for this may be related to communicating the colour in all its parameters to the reference tooth, whilst also considering the shade contribution from the underlying abutment, cement, and gum architecture. The aesthetic demand in recreating the optical characteristics of anterior teeth has provoked research and development into all-ceramic systems, as well as novel shade matching techniques.
Let’s start with the available methods and then describe them in turn. Numerous efforts have been developed to improve the predictability of shade analysis. The shade communication and execution methods are summarized below:
- Written shade subgroup (Vita Classical, Vita-Master 3D, Vita Easyshade, Ivoclar Vivadent Chromascop)
- Digital or analogue photographs of shade-tab and/or ceramic-tab (Smartphone camera, Point and shoot compact, Mirrorless compact, Digital single lens reflex, Medium format)
- Physical shade match with the technician
- Custom shade match with the patient present in the laboratory
- Custom shade-tab at preparation
- Multiple aesthetic trials
- Multiple simultaneous fabrications
- Digital photographs with white balance calibration via L*a*b* values
It is our opinion in using the majority of the above methods, that all had the inherent issue of transferring the shade information from the communication medium to the ceramist’s understanding. The interpretation of option
Option 1) is denoted by a shade tab that is often made of an acrylic resin that has little equivalence to the corresponding feldspathic ceramic. Furthermore, the incisal variation and chromatic gradation cannot be communicated with a written shade. Automated digital shade taking devices have anecdotally been reported to have limited use due to inaccuracy, and providing an average shade only.
Option 2) may yield superior results, as the adjacent teeth are transferred, as well as the relation of a reference point (shade tab) to the reference teeth. Ceramic shade tabs take this one step further, as the ceramic tabs are a closer representation of the particular ceramic shade. This method is not without flaws, as the white balance of the clinician’s camera ideally ought to be synchronized with the technician’s reference monitor.
Option 3) is a popular method whereby the technician is able to physically assess the tooth in natural and artificial light. In practice, this method appears to be unreliable, as many technicians are more experienced in viewing photographs that are constantly available. The exceptions that exist are individuals who use physical shade taking as their primary means for shade analysis.
Option 4) allows the technician to view the abutment and restoration in situ with the patient present. This can pose a logistical challenge, however, imparts the flexibility of making immediate shade corrections and re-verifying the result. This would be particularly useful for dark abutments, and in thin, translucent restorations, where cement colour is of greater importance. Technician interpretation nevertheless remains a challenge.
Option 5) involves the ceramist fabricating a custom shade tab at the diagnostic phase to be assessed at subsequent visits. This method is a variation on using multiple trials to optimise the shade integration.
Option 6) Using multiple aesthetic trials allows incremental changes to be made over several appointments, however, this is time-intensive for the patient, clinician and technician, and is still liable to the previously noted issues.
Option 7) Multiple fabrication is a resource-intensive method with an aim to execute the case in a single aesthetic trial. The principle involves creating several restorations that are subtly varied in their value, chroma, anatomy and effects.
Option 8) The final option is an emerging method that removes the subjectivity from shade taking. A white card is photographed through a cross polarizing filter alongside the reference tooth, and used to calibrate the receiving monitor. The L*a*b* (Hunter 1948) values represent the value (L) and chroma-hue (a, b) numerically, such that ceramic combinations may be tested against the L*a*b* values of the reference tooth. The technician is able to digitally assess the proposed restoration, and make modifications as desired. This is time-intensive for the ceramist, but is proven to be more reliable than existing methods.
In conclusion, a take home message is that colour matching is not a simple task, and we advise looking for cosmetic dentists of London that are experienced in shade matching like us at Marylebone Smile Clinic. Before and After examples are a good indication as well as knowledge of colour and ceramic/composite resin systems.
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