The curing pattern of photo-initiated dental composites

In this study the curing of photo-initiated composites was investigated. After irradiation, the material in an experimental cavity could be divided into three zones: zone A which showed physical properties comparable to those of chemical initiated composites, zone B which was markedly softer than the first one, and zone C which showed no signs of curing at all. The location of the zones was dependent on the energy of the u.v. radiation, the exposure time, the storage time, and the storage conditions. The uncured material of zone C showed no tendency to set. The clinical implications of the observations are discussed.