Digital tooth shade determination (synonym: digital tooth shade measurement) is a procedure for the exact evaluation of the shade-providing components of a tooth surface prior to the fabrication of tooth-colored restorations. The correct determination of tooth color is a very difficult step in the fabrication of tooth-colored restorations, because the color impression of the natural tooth is composed of three different components:
- Brightness (“Value”)
- Color saturation (“Chroma”)
- Hue (“Hue”)
The common tooth shade determination is done by the observer, i.e. dentist or dental technician, with so-called color rings. These contain material samples of the material to be processed, such as composite (plastic) or ceramic in several available shade groups and requires a lot of experience. Differences in brightness, shade and saturation as well as individual peculiarities (cracks, enamel stains, etc.) are recorded in this type of shade determination by means of a sketch of the tooth surface. In this process, the color selection by the observer’s eye is inevitably influenced by variable factors such as:
- The changing light conditions in the dental practice (artificial light, daylight, time of day).
- Different lighting conditions in the dental office and in the laboratory.
- Interactions of tooth color with environmental colors (clothing, skin color, make-up).
- A color vision deficiency of the viewer
- The color adaptation by the eye of the observer. To avoid the adaptation, it is helpful to look at the tooth for only a few seconds and in the meantime direct the gaze to a blue surface.
From these limitations, the advantages of digital tooth shade determination:
- Measurement results are created objectively
- Stored reproducibly and
- Made available to the dental laboratory in seconds.
- A digital photograph of the reference tooth with the peculiarities of its surface structure saves the more inaccurate hand sketch and accompanies the laboratory work steps.
Indications (areas of application)
A digital tooth shade determination is usefully carried out by the dental laboratory prior to the fabrication of tooth-colored restorations such as veneers (veneers) and all-ceramic crowns, especially if the restoration involves a single tooth in the anterior region. It can also be helpful in the restoration of incisors with composite fillings (plastic fillings), if these are produced using complex multicolor and multilayer techniques.
Before digital tooth shade determination
Before digital tooth shade determination, the surface of the tooth to be evaluated should be cleaned without drying it out. This is because if moisture is removed from the tooth substance by previous treatment measures, its shade effect will change. Thus, a tooth shade determination should be performed at the beginning of a treatment session.
The procedure
Digital tooth shade determination can generally be performed using two different techniques: one is a so-called colorimeter, and the other is a spectrometer. While the former is dependent on ambient light and thus a variable that strongly influences the result, the spectrometer works independently of light influences by extrapolating the difference between ambient light and the light reflected by the tooth. Since the natural tooth consists of the substances dentin (tooth bone) and enamel, which are of different colors and transparency and are also present in different layer thicknesses from the tooth neck to the incisal edge, this results in a large number of color nuances in the worst case. The spectrometer takes account of this by means of color mapping, in which it measures the tooth surface several times and creates a differentiated “map” of the surface. The alternative variant is the division into three areas, the three-area measurement, which is limited to the dominant color at the neck of the tooth, the center of the tooth and the incisal edge. Color determination alone does not provide the dental technician with all the necessary information. In addition, the spectrometers (e.g. SpectroShade Micro) offer the option of digital photography, which records individual characteristics such as white spots (white decalcifications), enamel cracks and the transparency of the enamel.If the spectrometer can measure ceramics in addition to natural tooth substance, the result of the dental work can be compared with the specifications of the reference tooth.
