The influence of interfacial gaps of different sizes on recurrent caries lesion formation next to composite resin restorative material and on plaque acid formation and composition.

Recurrent caries is the disease in which cavity formation occurs next to
existing fillings. It is the most common reason for replacing restorations.
There are many theories which trie to explain how recurrent caries develops.
One of those theories is that when a small gap exists at the restoration-tooth
interface, bacteria can form a biofilm and produce acids which will result into
demineralisation of the tooth and development of a new cavity next to a
restoration. The aim of this study is to closely monitor if recurrent caries
develops in presence of a gap and what size of gap promotes recurrent caries
lesion development.

Aim of this in situ study is to investigate the development of wall lesions in
the presence of different interfacial gap sizes.

It's a mono-center, single-blind in situ study. The volunteers will wear a
removable appliance with 10 samples, made of tooth and filling, during a
period of 8 weeks, 24 hours per day. Once a day the removable appliance will be
removed for cleaning with a fluoride-toothpaste. Four times a day the samples
will be dipped in a sucrose-solution for 5 minutes, then it will be rinsed with
water and reinserted in the mouth.
Lesion depth and mineral loss will measured every two weeks by making a sort of
X-rays of the samples outside the mouth. Also, after 4 and 8 weeks plaque will
be collected from the samples and biofilm and acidogenicity will be
investigated.

Strictly speaking no intervention is carried out with the subjects themselves.
They will wear appliances with tooth samples placed next to restoration
material with different interface characteristics: ideally bonded, non-bonded,
100 µm gap, 200 µm gap, 400 µm gap. The appliances will be dipped in sucrose
solutions 4 times per day, and brushed 1 time per day.

The burden for participating volunteers exists of wearing a removable appliance
in which the tooth samples are placed during a period of 8 weeks, for 24 hours
per day. Every two weeks they must visit our laboratory for measurement of the
samples extra-oral. Swallowing one of the tooth samples is a relative risk.
Mounting the tooth samples in the removable appliance with the help of
composite material in an undercut has proven to minimize this risk in earlier
studies (NL 28303.091.09). No benefit can be expected as no interventions are
done.