Journal of Dental Research, Vol 72, 1532-1536, Copyright © 1993 by International & American Associations for Dental Research Online Journals
Interferometric measurements of cusp deformation of teeth restored with composites
A. A. Suliman, D. B. Boyer and R. S. Lakes
Department of Conservative Dentistry, College of Dentistry, University of Mosul, Iraq.
A Michelson interferometry apparatus was used for measurement of the
displacement of the buccal cusps of premolars after restoration of MOD
preparations with composites. The effects of composite type, cavity size,
and hydration conditions were examined. Interferometry permitted real-time
measurement of cusp movement as it occurred. Contraction occurred very
rapidly, about 1/3 of the 60-minute amount within the two-minute period of
exposure to the curing light. Cusp movement was smooth rather than
interrupted, indicating lack of microfracturing at deformations of 11-46
microns. Contraction, 0.94% for Heliomolar and 1.2% for P-50, was similar
to the linear polymerization shrinkage of the resins. Less cusp movement
occurred in small cavities than in large cavities. Hydrated teeth had less
cusp movement than dehydrated teeth.
