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