Journal of Dental Research, Vol 69, 1659-1663, Copyright © 1990 by International & American Associations for Dental Research Online Journals
Gradual increases in marginal leakage of resin composite restorations with thermal stress
Y. Momoi, H. Iwase, Y. Nakano, A. Kohno, A. Asanuma and K. Yanagisawa
Department of Operative Dentistry, School of Dental Medicine, Tsurumi University, Yokohama, Japan.
The effects of thermal stress on the marginal leakage of resin composite
restorations in bovine teeth were investigated by a method that preserved
the specimens. The changes in marginal leakage of specimens with increasing
numbers of thermal cycles were measured by an electrical conductivity
method. Four brands of posterior resin composites were used to fill
cylindrical cavities (2.0 mm in diameter and 1.5 mm in depth) on the labial
surfaces of bovine incisors, according to the manufacturer's instructions.
Thermal cycling stress was applied to the specimens for up to about seven
weeks (9000 cycles). During this time, the electrical conductance between
the pulp and a drop of physiological saline solution covering the resin
restoration was measured periodically by application of an electrical
potential (60 Hz, 10 Vp-p). Thermal stress increased the marginal leakage
gradually, rather than step-wise. Even before application of any thermal
stress, wide variations of marginal leakage were found among different
specimens restored with the same brand of resin. Specimens with less
initial leakage showed less increase in leakage, and vice versa, throughout
the experimental period.
