The purpose of this study was to investigate marginal microleakage by
examining the resin/dentin interface using a cryo-SEM and a silver ion
penetration method. Class 5 cervical cavities were restored using an
adhesive resin system following treatment with 37% phosphoric acid gel
. The cavity wall adaptation was observed using cryo-SEM to avoid spec
imen damage. This observation showed excellent marginal adaptation of
material to cavity walls and no gap formation. However, silver ions ha
d penetrated beneath the resin-impregnated layer when observed with co
nventional SEM images, which showed the leakage of silver ions between
the resin and decalcified tooth structure without gap formation. This
study suggests that the bonding monomers of Clearfil Photo Bond were
not fully able to penetrate into the demineralized dentin after phosph
oric acid etching, thus leaving a porous zone as a microleakage pathwa
y beneath the resin-impregnated layer.