The usefulness of silicone has been demonstrated. No special materials are necessary, as those which are already present in the dental office are adequate. The silicone will not distort over the treatment period and can be repositioned accurately to ensure uniformity of the dose. It is also easily cleaned and stored for daily use. It can be used to improve the plane of the surface tissue and provide "buildup" to fill "dead space," which helps assure accurate assessment of the magnitude and distribution of the desired radiation dose.