Summary The longevity of dental restorations is largely
dependent on the continuity at the interface between the restorative
material and adjacent tooth structure (the restoration margin). Clinical
decisions on restoration repair or replacement are usually based upon
the weakest point along that margin interface. Physical properties of a
restorative material, such as polymerisation shrinkage, water sorption,
solubility, elastic modulus and shear strength, all have an effect on
stress distribution and can significantly affect margin integrity. This
review will focus on two aspects of margin deterioration in the oral
environment: the
in vitro testing of margin seal using emersion
techniques to simulate the oral environment and to predict clinical
margin failure and the relationship between clinically observable
microleakage and secondary caries. The many variables associated with
in vitro
testing of marginal leakage and the interpretation of the data are
presented in detail. The most recent studies of marginal leakage mirror
earlier methodology and lack validity and reliability. The lack of
standardised testing procedures makes it impossible to compare studies
or to predict the clinical performance of adhesive materials. Continual
repeated
in vitro studies contribute little to the science in
this area. Clinical evidence is cited to refute earlier conclusions that
clinical microleakage (penetrating margin discoloration) leads to
caries development and is an indication for restoration replacement.
Margin defects, without visible evidence of soft dentin on the wall or
base of the defect, should be monitored, repaired or resealed, in lieu
of total restoration replacement.
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