Whitening and Composite Bonding
It is essential after completion of home whitening treatment to wait for a period of two weeks to allow all the oxygen to be dissipated from the tooth and for the shade to settle to the actual shade.
After tooth whitening, there is maximum saturation of oxygen inside the enamel. This causes a reduction in bond strength of 20%. It is thus essential to wait for two weeks for the enamel bond strength to recover back to the normal levels prior to commencing direct bonding onto the surface of the tooth.
Stratified Layering Technique
With the introduction of multiple component composite systems, it is now possible to create beautiful natural restorations using multiple layers of composite using their different optical and material properties. The Aura composite system is ideal as it contains both enamel and dentine shades (Figure 9).
The enamel shades are a microfill composite, which give the properties of a glass-like appearance of natural enamel (Figure 5). The dentine shades ore a nanohybrid material (Figure 6), which gives extra strength for occlusal build ups and they can be used as a bulk-fill material. There are separate bulk-fill syringes available for this purpose.
Shade Selection of Composite Resin
According to Vonini (1996), it is essential to undertake a detailed evaluation of hue, chroma, opalescence, and fluorescence of the tooth in order to simplify the composite stratification technique.
This is done early in the clinical procedure to ensure that there is no dehydration of the tooth when the tooth is fully isolated (Figure 5).
Once the tooth is fully isolated, it dehydrates and lightens, and this can result in the selection of a shade that is too light. Blends of composite colours are normally used and, after selection of the translucent enamel shade (Dietchi, 2008), the dentine shade is used (Figure 6)
The hue is given by the dentine. The hue remains the same, although the greater thickness of the enamel interferes in its perception, giving it a less saturated aspect. Therefore, the hue of the tooth is given by the dentine and influenced by the enamel. The enamel does not change the hue, but only confers a greater or lesser saturation or chroma according to its thickness (Franco et al, 2007).
This is applied from darkest to lightest to give the restoration a lifelike appearance. Different translucencies may be selected for the mesial corners as, often, these ore more translucent than the distal corners (Figure 7).
Used with an understanding of tooth morphology, restorative material selection, colour options, and the physical properties of light, these layering techniques allow optimally aesthetic restorations to be predictably achieved (Terry, 2003).