Journal of Dental Research, Vol 73, 1470-1477, Copyright © 1994 by International & American Associations for Dental Research Online Journals
Stress analysis of a bulk-filled Class V light-cured composite restoration
T. R. Katona and M. M. Winkler
Orthodontics Division, School of Dentistry, Indiana University-Purdue University, Indianapolis 46202.
Clinical failures are often associated with the polymerization shrinkage of
resin composite restorative materials. These problems include tooth
sensitivity and fracture, marginal leakage, loss of the restoration, and
recurrent decay. Our goal was to examine transient composite distortions
and interface stresses as a bulk-filled light-cured composite polymerized
in a Class V restoration. The analysis was based on a finite element model.
The curing of the restoration was divided into 4 steps: approximately 1/30,
1/4, 1/2, and full depth (1/1) of cure. Since the actual curing pattern is
not known, calculations were performed for three hypothetical (flat,
convex, and concave) polymerization front shapes. The calculations showed
that the assumed shape was a critical factor in determining cured surface
deformations. For example, the initial cure depth (1/30) resulted in a
surface bulge if the polymerization front was presumed convex, while the
concave front resulted in a large intrusion. By the time that about 1/2 the
depth of the restoration was cured, the differences were essentially gone.
The final surface outline was intruded. Interface stresses in the curing
restoration were qualitatively similar regardless of the assumed
polymerization shape. As with surface distortions, the stresses changed
with curing depth. It was concluded that (1) transient events during
polymerization are possible contributors to clinical complications, and (2)
more must be known about the polymerization pattern.
