GC EUROPE G-aenial - Manual (Page 9)

9 G-ænial Anterior & Posterior Technical Manual
light is scattered and reflected by internal tooth structures (e.g., enamel crystals, dentine-enamel
junction and dentinal tubules). certain wavelengths are absorbed, whereas the remaining light
possessing information on tooth hue, chroma, value and translucency is diffusively reflected. For
example, enamel mostly consists of apatite crystals and will allow light to pass through without
much scattering while dentin has a more complex structure of hydroxyapatite crystals and collagen
and will scatter the light in all directions.
Measuring the scattering properties of a composite: the goniophotometer
the light scattering property of a material can be evaluated using a goniophotometer. this is
designed to measure the intensity of transmitted light at various angles (-90 to +90 degrees).
Figure 7 shows artificial cavities in a block of composite shade a3 that were filled with 2 different
composites with shade a2. Only one of these is able to mimic the surrounding environment. after
analysing their light diffusing properties with the goniophotometer, it appears that the one which
adapts the best possesses higher scattering properties.
Figure 7: a3 cavity filled with a2 composite
These results suggest that light scattering is
even more important than hue to ensure that
the material is invisible.
What makes a composite restoration become invisible?
the ability of a composite to scatter light and diffusely reflect it similarly to the natural tooth makes
it possible to achieve a perfect match with the surrounding tooth structure. a composite material
becomes invisible only when it has this scattering property and can then be used in a single shade
layer technique.
like the tooth, G-ænial contains different interfaces with different optical properties, resulting in
varied reflection of light. the excellent scattering ability of G-ænial is related to the extremely
diverse structural composition, which results in it mimicking the reflectivity of a natural
tooth.
Block of
composite shade
a3 with cavity
low-scattering
composite
high-scattering
composite
Figure 5: System set-up of the goniophotometer
Figure 6: Observation of light diffusion with different
composites
light source
light source
+90 Degrees
0 Degrees
-90 Degrees
light transmission
composite
sample
composite sample
composite sample
Low light Scattering
High light Scattering
light source
light detector