GLASSIONOMER CEMENT FOR PERMANENT DENTAL RESTORATIONS: A 48-MONTHS,
MULTI-CENTRE, PROSPECTIVE CLINICAL TRIAL
Moreover, it is not easy to apply the dam in
children due to the shape of deciduous dental
elements or elements sometimes only partially
erupted, despite the existence of speciallyshaped hooks. In these situations the use of GICs
may be of particular interest since nowadays
the placement of the dental dam during GICs
restoration procedures is considered at risk of
leading to material over dry and consequently
weaker restorations. Our data do not support any
significant influence of dental dam positioning
on the success or failure of the GICs restorations,
even if it is likely that the limited number of
failures at 48 months affected the significance of
this analysis.
However, it is not fully identified in literature
to date which may be the influence of dental
dam positioning on the placement of GIC
restorations and its role on the long-term survival
of the restorations. Regarding the high-viscosity
glassionomer cements, the formulation chosen
in this study is that of pre-dosed capsules, to be
applied after agitation in a special electric mixer
and through the use of an applicator. The predosed capsules help avoid errors in mixing and
improper calibration of the proportions between
the two components (usually powder and liquid),
to be mixed as in the majority of GICs products.
In fact, incorrect mixing could affect the
mechanical properties of the product, and, for a
clinical trial, it could introduce an important bias
for final evaluation. The light-curable coating
employed is able to infiltrate the surface and
the margins of the restoration, and is therefore
useful in overcoming the limits of resistance
to abrasion and marginal cracks occurrence
of older GIC systems. The aim of the coating
agent is to form a resin layer, with an average
thickness of 35-40 micrometres, which seals
and protects both the areas of restoration
and the adhesive interface between the
restoration and tooth structure.
This is particularly valuable because
a
discrete
frequency
of
dentine
hypersensitivity is normally reported while
using composite resins to replace the
amalgams. The absence of hypersensitivit y
recorded in this study by the patients’
questionnaires
may
be
related
to
fluoride release and to the absence of any
conditioning treatment before the placement
of the glassionomer cement. According to the
manufacturer’s indications and to the protocol
of this study, polyacrylic acid or other kind of
dentin conditioning systems were not applied
on cavity walls before applying the cement. In
this clinical trial, the absence of conditioning
seemed not to affect the adhesion and the
strength of the link of glassionomer cement
with enamel and dentin: even if it is likely
that a conditioning phase may improve the
adhesion of glassionomers to tooth structures,
the adhesion achievable through a control of
STOMA.EDUJ (2015) 2 (1)
cavity preparation, of rinsing procedures and
the use of a modern GIC system may obtain
an adhesive interface with adequate strength
and resistance. The need of using conditioners
with modern high-viscosity glassionomer
cements, however has still to be investigated.
Regarding their use, modern glassionomer
cements can be applied in one step, without
layering technique. The estimated time to
complete the restoration with the tested GIC is
about 3-5 minutes after tooth preparation. Less
recent and some of conventional glassionomer
cements sometimes require more than
5 minutes (1,11,13). If we consider the
mechanical properties of coated glassionomer
cements, infiltration into the surface of
GICs and dispersion of nano-filler particles
contained in resin coating ensure lasting
protection and integrity of margins, increasing
both the strength and wear resistance (27,28).
In fact, they fill the porosities which inevitably
forms on GICs surfaces due to the nature of
the material. The fluid coating agent creates
a regular surface and allows protection of the
margins, equal distribution of mechanical load,
and protection during the phases of complete
maturation of glassionomers: the typical time
for reaching final hardness is 6-7 days. The
final treatment with coating resins managed to
transform the surface of the restoration into a
glossy layer, without further polishing.
In
terms
of
aesthetics, the
modern
glassionomer cements are able to stand
superior optical properties when compared
to conventional glassionomer cements. The
translucency and aesthetic appearance could
in fact be connected with application of
the nanofilled resin coat. Nevertheless, the
questionnaire revealed that especially dentists
were much less satisfied than patients about
the color matching with tooth structures of the
restorations. The low rate of color matching
can depend on dentist’s choice at the time of
restoration, but also on the optical properties
of GICs, still not at the same performance as
resin-based composites. The lower rate of
color matching in the dentists’ questionnaire
probably depends on the higher competence
and criticism level shown by dental
professionals when confronted to patients.
Regarding the restoration evaluation system,
the criteria first described by Frencken et
al. in 1996 were used (14). These criteria
have been especially developed to assess
GIC restorations, taking into account the
material characteristics, as previously
discussed, and the issues these materials
have raised during the past decades.
In this sense, these criteria have been
preferred to the USPHS criteria described
by Ryge in 1973 (29). USPHS criteria ca n
a ssess a d d itiona l information respect to
Frencken’s criteria, however they have been
17