Statement of problem. The tooth preparation of a bevel is recommended
to improve marginal quality of a composite restoration. However, in sm
all Class II restorations, it is unclear if a bevel also contributed t
o a better marginal tit.Purpose, This study investigated the influence
of tooth preparation design on microleakage of minimal posterior Clas
s II composite restorations. Material and methods. Bos-shaped Class II
tooth preparations for posterior composite restorations in maxillary
premolars were restored with a total etch technique. The tooth prepara
tions were beveled or nonbeveled and the box prepared at a right angle
cervically or additionally excavated. The facial and lingual box marg
ins were also either beveled or unbeveled. The teeth were thermocycled
and immersed in a dye solution. After sectioning specimens, dye penet
ration at the facial and palatal margins was recorded. Results. A beve
l-reduced microleakage both at the cervical and ascending wails. Ename
l cracks were observed along certain unbeveled margins as recorded in
this study. The additional excavation did not contribute to reduction
of microleakage. Conclusions. Tooth preparation of a bevel is recommen
ded for an optimal marginal seal in small box-type Class II composite
restorations.