In our study, the hardness of the celluloid strip–
finished surface increased with time. Thus, it is
assumed that the oxygen inhibition, which occurs
under the celluloid strip, would be different from the
inhibition that occurs in the composite surface when it
is cured in contact with air. When the composites cure
in air, oxygen diffuses into the composite surface,
whereas it is likely to be entrapped into the composite
when the composites cure under the matrix. Thus, it is
postulated that the radicals, which reacted with oxygen
that was entrapped in the composite under the celluloid
strip, reacted with the unreacted monomer and
polymerized with time. Considering the half-life of
radicals,18 additional polymerization may continue to
occur until a few days after light curing.