These were introduced in 1950 and have gained wide acceptance in North America. In
Europe they have been less popular, being seen by most dentists as too difficult to
use, although in reality they are often easier to place than some intracoronal
restorations (337HFig. 8.4).
All published studies have shown stainless-steel crowns to have a higher success rate
in primary teeth than all other restorative materials. They are certainly the preferred
treatment option for first primary molars with anything other than minimal caries.
Stainless-steel crowns are also advocated for hypoplastic or very carious first
permanent molars, where they act as provisional restorations prior either to strategic
removal at age 9-12 years or later restoration with a cast crown (338HFig. 8.5). Etched
retained castings may now be used for the definitive restoration of permanent
hypoplastic teeth without involvement of the approximal surface; more conservative
provisional restorations than stainless-steel crowns should be considered if this is
intended.
Composite resin
Composite resins came on the market in the early 1970s and have been modified since
then in an attempt to improve their properties. Current materials are still best applied
to anterior teeth and small restorations in posterior teeth. The development of acid
etching at the time that these materials were introduced has ensured that they have
performed reasonably well in terms of marginal seal. They are sensitive to variations
in technique and take longer to place than equivalent amalgam restorations. They
must be placed in a dry field (339HFig. 8.6).
The long-term success of composite resins is jeopardized by their instability in water.
The best materials have maximum inorganic filler levels and low water absorption,
but will deteriorate over time.
Key Point
- All composite resin and glass ionomer restorations must be placed in a dry field.
Glass ionomer
Glass ionomer cements came on to the market in the late 1970s and have also been
modified since then in order to enhance their properties. Current materials are much
improved and have some advantages over composite resins. Being made from glasses
with a high fluoride content they not only provide a sustained release over an
extended period but also act as a rechargeable reservoir of fluoride, which may protect
adjacent surfaces from caries progression.
They adhere to enamel and dentine without the need for acid etching, do not suffer
from polymerization shrinkage, and, once set, are dimensionally stable in conditions
of high humidity such as exist in the mouth (340HFig. 8.7). Similarly to composite resins it
is imperative that they are placed in a dry field.