SHADE SELECTION ASPECTS
Reaching biomimicry in a simple way with composites at the dental office.
Achieving the “perfect shade” in dental clinic is always a challenge for the professional, who needs to rely on the triad: light source, object and observer. Those three factors have critical interaction in the final visual aspect that may determine or not the harmonious look of restorations with composites. Several methods have been developed to achieve clinical success in that aspect, from the most complex to the simplest. The purpose of this article is to discuss, briefly, the aspects involved in the appearance of restorations made with composites and recommend a simple and replicable methodology for daily clinic use.
Triad: light, object and observer
1. Light: light sources emit light waves that interact with an object and, after being reflected, they are perceived by an observer. Some wavelengths are absorbed by the object while others are reflected and, thus, perceived as the shade of the object. Different light sources may give the same object different shade perceptions, due to distinctive light “temperatures” and different light reproduction indexes.
For a good shade selection, it is important for the environment to have lighting fixtures with reproduction and temperature indexes as close as possible to sunlight.
2. Object: besides the light reflection that defines the shade of the object, other factors such as shape and surface texture have a strong influence on the shade aspect of a restoration with composites. In other words, it is not enough to choose the right shade but it is also necessary to reproduce the anatomic shape in as much micro-esthetic details as possible and to consider the effect of the optical properties: fluorescence, translucency, opacity and opalescence.
3. Observer: the observer receives the light reflected or transmitted by an object and interprets the results. Eye responses can vary from individual to individual and depend on wavelengths. Staring for too long at a shade guide next to a tooth, as well as physical and mental exhaustion, may reduce the capacity to discern. That way, one should not do complex shade selections after a long and tiring day of work. There are devices called spectrophotometers, which are intraoral colorimeters that may detect tooth shade with relative precision helping in the process. However, their cost is still high and the result obtained needs verification or has to be used merely as a starting point, because they measure just one region, not always identifying the polychromatism of the tooth .
The three coordinates of SHADE:
According to what Munsell described in his proposal of tri-dimensional shade system, three coordinates were established:
• Hue: referred to as basic color, or rather, the wavelengths of the light reflected by the object and observed (for example: blue, yellow and red).
• Value, Brightness or Luminosity: corresponds to the variation from white to black, going through shades of gray. The higher the value of a tooth, the whiter it will be, the lower the value, more grayish the tooth will be. In odontology, therefore, the value is the most important factor when choosing a shade since teeth show little hue variation from one to another.
Vittra APS (FGM) offers high and medium value shades for small adjustments in restorations that show discrete and undesirable grayish effects.
• Chroma or Saturation: constitutes the measure of the shade intensity or saturation of pigments in it. Normally, we observe a greater saturation in the cervical portion (thinner part of the enamel, with the predominant optical effect of the dentin) which decreases gradually to the incisal portion as the enamel thickness increases and the dentin (more saturated) has its chromatic effect reduced.
Fig. 1 – A thin layer of translucent composite, associated to dentin composite, creating an area for the passage and reflection of light in the incisal third.
Fig. 2 – Final aspect of the case with enamel composite coating (Vittra APS).
So, what steps should one follow to apply the principles of optical properties and achieve the “perfect shade” when working with composites? Read the SHADE SELECTION RECOMMENDATIONS for a simplified step by step to help you achieve successful restorations with composites.
