Discussion
The resins presented in this work were Filtek Z350 3M. This was the
first product that used nanotechnology and is the only one on the market
to offer the aesthetics of a microparticulate resin and the resistance
of a hybrid resin, according to the manufacturer. Selection involves
determining the hue, value, and chroma. The selection must be made based
on factors related to the material itself, on clinical factors, on the
professional’s preference.1,2
Natural teeth are polychromatic, and while composite resins are
monochromatic, it is therefore very difficult to achieve aesthetic
excellence with a single color of composite resin, although they do not
always compromise the smile’s aesthetic.3,4 Inadequate
light curing can lead to undesirable consequences such as: decreased
adhesion of adhesives, decreased color stability of the composite resin
due to a partial reaction of the accelerator and absorption of dyes,
decreased wear resistance due to inadequate mechanical property of this
material.4
Thus, direct restorations of the anterior teeth, especially in the
central incisors, symmetry plays an important role. The clinician can
take advantage of silicone indices based on a wax to build palate and
incisal walls; however, when he needs to reproduce symmetrical items on
the side of the chair freehand, such as interproximal emergency
profiles, macro, and micro-surface textures and chromatic
characteristics, the result can often be
unpredictable.11
In this context, a meta-analysis study discussed the effectiveness of
composite resin restorations on anterior teeth, verifying whether
specific material classes, dental conditioning methods, and operational
procedures influence the outcome for Class III and Class IV
restorations. Of the 84 clinical trials, 21 studies met the inclusion
criteria, 14 of them for Class III restorations, 6 for Class IV
restorations, and 1 for diastema closure; the latter was included in the
class IV group. Twelve of the 21 studies started before 1991 and 18
before 2001. The average estimated success rate (without replacement)
after 10 years for Class III composite resin restorations was 95% and
for Class IV restorations 90%. The main reason for replacing Class IV
restorations was mass fractures, which occurred significantly more
frequently with macrofiliated composites than with hybrid and
macrofiliated composites. Caries adjacent to restorations were uncommon
in most studies and represented only 2.5% of all restorations replaced
after 10 years, regardless of cavity class. Class III restorations with
glass ionomer derivatives suffered significantly more anatomically loss
than restorations with other types of material. When the enamel was
etched with acid and no bonding agent was applied, significantly more
restorations showed marginal staining and detectable margins compared to
the enamel attack with enamel bonding or the total etching technique.
The chamfer of the enamel was associated with a significantly reduced
deterioration of the anatomical shape compared to non-chamfering, but
not with less marginal spots or less detectable margins. The type of
isolation (absolute / relative) had a statistically significant
influence on marginal caries, which, however, can be a random
finding.12
A 15-year retrospective study investigated the impact on survival, when
a repair is seen as a failure or not, in composite anterior
restorations. Data were collected from the files of patients at a
private dental clinic, including patients with direct composite
restorations placed on the anterior teeth (Class III, Class IV, or
veneer) between January 1994 and December 2009. The data were analyzed
considering whether or not to repair as a failure. One hundred and
forty-four patient records were included, with 634 restorations. At 15
years of age, Class III / IV restorations showed 69% survival and 2.4%
annual failure rate (AFR) when the repair was not considered a failure
and 64% and 2.9% AFR, respectively when the repair was seen as a
failure. For direct veneers, at 5 and 10 years of follow-up, survival
dropped from 85% to 74% and from 52% to 38%, respectively, when the
repair was considered a failure. In general, restorations placed in the
upper jaw had an increased risk of failure compared to the lower jaw,
and restorations in central incisors had a higher risk of failure
compared to dogs. Therefore, composite repair appears to be a suitable
alternative for class III, class IV and veneer restorations, as it was
able to increase the survival of restorations performed on anterior
teeth.13
Also, a prospective observational cohort study aimed to estimate the
survival of a hybrid compound placed by a clinician up to 8 years of
follow-up. All patients were referred and recruited for a prospective
observational cohort study. A composite was used: Spectrum®
(DentsplyDeTrey). Most restorations were performed on the upper anterior
teeth using a Dahl approach. A total of 1010 direct composites were
placed in 164 patients. The average follow-up time was 33.8 months. 71
of 1010 restorations failed during follow-up. The time to failure was
significantly longer in older individuals and when there was a lack of
posterior support. Bruxism and an increase in the vertical occlusal
dimension were not associated with the failure. The proportion of
failures was higher in patients with a Class 3 or edge-to-edge incisal
relationship than in Class 1 and Class 2 cases, but this was not
statistically significant. There were more failures in the lower arch
(9.6%) compared to the upper arch (6%), with the largest number of
composites being placed on the upper incisors (n =
519).14
In this sense, creating perfect direct composite restorations is a
challenge due to the limitations of many materials that affect the
integration of shadow or surface quality and color stability. Along with
technological disadvantages, a certain complexity and lack of
predictability in the clinical application were inherent to the
technique and made it elitist for a long time. The concepts of shading
and layers have progressively evolved from a simplistic,
known-histologic bilaminar technique to a multi-layer approach (3 to 4
or more layers), following the Vita Classic ™ system. One of the most
achieved concepts is polychromatic stratification, which uses a variable
number of layers (basically VITA ™ opaque dentin or not VITA ™,
chromatic enamel, and translucent/opalescent enamel), driven by the
natural optical composition of the tooth. Also, a simplified non-VITA ™
shading system was developed with a reduced number of layers, with a
layer of dentin and enamel and effect shades, known as the concept of
natural stratification, aiming at the same optimal and natural aesthetic
integration.15