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The complexities of colour matching – Mark Allen Coltene

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  Posted by: The Probe      18th March 2019

One of the ever-present issues in restorative dentistry is colour matching. While not functionally necessary, a poor colour match to the natural dentition makes restored teeth stick out noticeably, which is not only aesthetically unpleasing but can affect the patient emotionally. With aesthetic considerations only ever growing in importance among patients, accurate colour matching is a vitally important skill to possess.

There are various systems of colour in use today (the Munsell system, CIELAB, CIECAM02, etc.) but generally speaking colour can be described using the following terms:

  • Hue– the wavelength of the observed light (red, blue, green, etc.).
  • Saturation/Chroma– the strength or intensity of the hue, going from a grey tone (no saturation) to pure colour (high saturation).
  • Luminance/Brightness/Value– the relative darkness of the colour. This is a crucial characteristic for determining the shade of the tooth.

Additionally, natural teeth have several properties that must be considered when attempting to match their appearance:

Translucency

Translucency is the gradient between transparent and opaque. In a restoration, increasing the translucency of a crown effectively lowers its brightness. This is because more light passes the surface and is scattered within the restoration rather than being reflected back.[1]

Fluorescence

Fluorescence is the physical phenomenon whereby a particular chemical compound emits light of a given colour, after being exposed to light of a different colour.[2]

Opalescence

Opalescence is caused by the scattering of light, giving materials a bluish appearance in reflected colour and an orange-brown appearance in transmitted colour due to the shorter wavelengths of light being scattered more than the longer wavelengths. For this reason, tooth enamel – which is naturally colourless – appears bluish.[3]

While we can analyse object colour using the above parameters it is important to remember that, as may be expected from biology, no tooth is a strictly uniform colour. Teeth are made up of a number of hues, with most having shading variations even within the same hue.[4]Researchers report that natural tooth colour distributions are found in various shapes, such as banana and flounder-like patterns.[5]Furthermore, these patterns vary regionally, which may be due to ethnicity, nutrition and various other factors. For this reason, a shade scale based on, for example, a German population sample might not adequately cover a person of Sudanese ancestry.[6]

Unfortunately, commercial shade guides are not always sufficiently comprehensive to cover all naturally occurring tooth colourations present in the population, with around 15% of patients not matching shade tabs and around half having more of a red colour than the tabs are calibrated for. This problem can be further exacerbated by using ageing or deteriorating shade tabs, which gradually move away from their factory appearance.[7]

To further complicate matters, there are a number of factors that can affect your perception of colour, including biological variations (though contrary to popular belief, sex is not a factor), emotions and lighting conditions.

  • Colour blindness. Nearly one in ten men have a colour vision defect of some sort.[8]Due to genetics, red/green colour blindness is much more common in men than women, but both sexes are equally likely to have blue colour blindness.[9]There is some debate over whether prospective dental students should be screened for colour vision discrepancies.[10]
  • Refractive errors. Uncorrected refractive errors in the dentist’s eyes, such as from short-sightedness or astigmatism, can result in difficulty accurately judging colour.[11]Thankfully, if you wear current corrective eyewear this should be mitigated.
  • Emotional state can impair colour perception. It has been established that individuals with depression perceive colour, particularly contrast, in a significantly reduced way.[12]Less drastic psychological and emotional differences are also thought to influence the way we see colour.
  • Ageing. As we age, humans tend to perceive things as less blue and more yellow and brown.[13]
  • Lighting conditions. Time of year, month and day, alongside weather conditions, all affect the colour of sunlight.[14]Colours can appear to match under some lighting conditions but not others, this is known as metamerism. Not only does natural lighting vary over time, human perception of colour changes seasonally. This has a particularly significant effect on how our eyes perceive yellow, which has obvious implications for accurately discerning tooth colour.[15]
  • Medication. Many medications can have an effect on colour perception, these include: digoxin (a cardiac stimulant), sildenafil (Viagra), hydroxychloroquine (anti-malarial drug, sometimes prescribed for rheumatoid arthritis), and tamoxifen. Being on one of these medications will not necessarily alter an individual’s colour perception, but it is a possibility.[16]

If you are looking for a solution that will allow you to offer outstanding aesthetics and excellent colour matching whatever your patient’s natural shade, COLTENE has you covered. COLTENE’s BRILLIANT EverGlow®is a submicron composite that offers universal shades through the Duo Shade System. The system simplifies shade considerations by combining two VITA shades into a single shade, which blend seamlessly with adjacent teeth. For unusually complex cases five additional shades are available, so you can ensure excellent aesthetics with every case.

 

Armed with the right tools and materials and an awareness of potential impediments to accurate colour perception, you will be well equipped to provide perfectly colour matched restorations, no matter what shade your patient’s teeth may be.

 

To find out more visitwww.coltene.com, email info.uk@coltene.comor call  01444 235486

 

 

 

References

[1]Sikri V. Color: implications in dentistry. Journal of Conservative Dentistry. 2010; 13(4): 249-255. Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3010031/Accessed October 2, 2018.

[2]Wouterlood F., Boekel A. Fluorescence microscopy in the neurosciences. Encyclopedia of Neuroscience. 2009: 253-260. DOI:   https://doi.org/10.1016/B978-008045046-9.00666-5Available at https://www.sciencedirect.com/science/article/pii/B9780080450469006665Accessed October 2, 2018.

[3]Lee Y. Opalescence of human teeth and dental esthetic restorative materials. Dental Materials Journal. 2016; 35(6): 845-854. DOI: https://doi.org/10.4012/dmj.2016-091Available at https://www.jstage.jst.go.jp/article/dmj/35/6/35_2016-091/_articleAccessed October 2, 2018.

[4]Winkler, S., Boberick, K. G., Weitz, K. S., Datikashvili, I., & Wood, R. Shade Matching by Dental Students. Journal of Oral Implantology. 2006; 32(5): 256–258. doi: 10.1563/828.1 Available at http://www.joionline.org/doi/full/10.1563/828.1Accessed September 27, 2018.

[5]Yuan J., Brewer J., Monaco E., Davis E. Defining a natural tooth color space based on a 3-dimensional shade system. The Journal of Prosthetic Dentistry. 2007; 98(2): 110-119. DOI: 10.1016/S0022-3913(07)60044-4 Available at https://www.ncbi.nlm.nih.gov/pubmed/17692592Accessed October 2, 2018.

[6]Elamin H., Abubakr N., Ibrahim Y. Identifying the tooth shade in group of patients using Vita Easyshade. European Journal of Dentistry. 2015; 9(2): 213-217. Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4439848/Accessed October 2, 2018.

[7]Rishita A., Nagai S., Karimbux N., Da Silva J. Evaluating tooth color matching ability of dental students. Journal of Dental Education.2010; 79(9): 1002-1010. Available at http://www.jdentaled.org/content/74/9/1002Accessed September 27, 2018.

[8]Khosla A., Maini A., Wangoo A., Singh S., Mehar D. Prevalence of colour vision anomalies amongst dental professionals and its effect on shade matching of teeth. Journal of Clinical and Diagnostic Research. 2017; 11(1): ZC33–ZC36. DOI: 10.7860/JCDR/2017/23707.9178 Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5324491Accessed October 2, 2018.

[9]Colour Blind Awareness. Inherited colour vision deficiency. Colour Blind Awareness.Available at http://www.colourblindawareness.org/colour-blindness/inherited-colour-vision-deficiency/Accessed October 2, 2018.

[10]Mushtaq F., Baraas R., Al-Saud L., Mirghani I., van der Zee C., Yates E., Keeling A., Mon-Williams M., Manogue M. Should prospective dental students be screened for colour vision deficits? British Dental Journal. 2016; 221: 227-228. https://doi.org/10.1038/sj.bdj.2016.633Available at http://eprints.whiterose.ac.uk/102065/1/CVD_Opinion_Article_Revised_220616.pdfAccessed September 27, 2018.

[11]Çapa N., Malkondu O., Kazazoğlu E., Çalikkocaoğlu S. Evaluating factors that affect the shade-matching ability of dentists, dental staff members and laypeople. Journal of the American Dental Association.2010; 141(1): 71-76. Available at https://jada.ada.org/article/S0002-8177(14)62218-2/Accessed September 27, 2018.

[12]Bubl E., Kern E., Ebert D., Bach M., van Elst L. Seeing grey when feeling blue? Depression can be measured in the eye of the diseased. Biological Psychiatry. 2010; 68: 205-208. Available at https://www.ncbi.nlm.nih.gov/pubmed/20359698Accessed September 27, 2018.

[13]Hunjet A., Parac-Osterman D., Vucaj E. Statistic analyses of the color experience according to the age of the observer.Collegium Antropologicum. 2013; 37 (Suppl.1): 83–91. Available at https://www.ncbi.nlm.nih.gov/pubmed/23837226Accessed September 27, 2018.

[14]Sikri V. Color: implications in dentistry. Journal of Conservative Dentistry. 2010; 13(4): 249-255. Available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3010031/Accessed October 2, 2018.

[15]Welbourne L., Morland A., Wade A. Human colour perception changes between seasons. Current Biology. 2015; 25(15): 646-647. DOI: https://doi.org/10.1016/j.cub.2015.06.030Available at https://www.cell.com/current-biology/fulltext/S0960-9822(15)00724-1Accessed October 2, 2018.

[16]Rassi S., Saint-Amour D., Wittich W. Drug-induced deficits in color perception: implications for vision rehabilitation professionals. Journal of visual impairment and blindness. 2016; 110(6): 448-453. Available at https://www.researchgate.net/publication/310651102Accessed October 2, 2018.


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