Effect of exposure time on the depth of polymerization of a visible light-cured composite resin

• Published in: Journal of oral rehabilitation Vol. 15; no. 2; p. 167
• Main Authors: Baharav, H, Abraham, D, Cardash, H S, Helft, M
• Format: Journal Article
• Language: English
• Published: England 01.03.1988
• Subjects: Chemical Phenomena; Chemistry, Physical; Composite Resins; Dental Restoration, Permanent - methods; Dental Restoration, Permanent - standards; Hardness; Humans; Light; Surface Properties; Time Factors
• ISSN: 0305-182X; 1365-2842
• DOI: 10.1111/j.1365-2842.1988.tb00766.x

The effect of exposure time of a visible light source on the depth of polymerization and degree of hardness of a sample of Occlusin posterior composite resin was investigated. The border between cured and non-cured composite resin was identified by a change in colour and by applying pressure with a scalpel. Knoop hardness tests were performed perpendicular to the long axis of illumination. The composite resin nearer to the light source underwent more complete polymerization. Increased exposure time resulted in greater depth of cure. The rate of polymerization was greatest in the first 10 s. Maximum hardness measured up to a depth of 1 mm obtained after 80 s of exposure time. At greater depth, a decrease in Knoop hardness was observed. At exposures under 80 s, maximum hardness was not achieved even at a depth of only 1 mm.