Clinical procedures to avoid the 'dark halo' in restorations with direct composite resins (Introducing the concept of destructive interference in restorative dentistry)

The 'dark halo' present in the enamel surrounding anterior composite restorations spoils the appearance of the restoration and is very difficult to control. This article offers an explanation for its causes and proposes clinical solutions. The behaviour of the transmitted light may be handled through the use of an'internal mirror' made with a shade of opaque white composite resin and through the right choice of the enamel shade, seeking sufficient diffusion of the light. Another innovative concept is that of'chroma balance' which may be generally achieved through the use of more or less intensive dentine shades, different from the one which was originally chosen.

From study of the behaviour of light in bodies, and especially in teeth and restorations, it may be possible to find the cause of the 'dark halo'effect, which relates to the optical property called the'destructive interference of the light'