Translucency and color stability of resin composite and dental adhesives as modeling liquids – A one-year evaluation

Abstract

The aim of this study is to evaluate the influence of modeling liquids on the translucency and color shade of resin composites (RCs) after one year of storage. RC specimens were prepared using either a conventional insertion technique (control; without modeling liquid) or a restorative dental modeling insertion technique (RDMIT) with dental adhesives as modeling liquids (Scotchbond ™ Multi-Purpose [SBMP; 3M ESPE] or Adper™ Single Bond 2 [SB; 3M ESPE]). The initial colors of the specimens were obtained with a digital spectrophotometer and the CIEL * a * b * color system, after which specimens were stored (37°C) in distilled water or red wine for 12 months. Color measurements were reassessed after 6 and 12 months of storage, and scanning electron microscopy was performed after 12 months. Translucency and color change (ΔE * ) were calculated and analyzed using ANOVA and Tukey's test (α = 5%). RC samples prepared via RDMIT showed a translucency similar to that of control samples. ΔE * was also less intense for RCs containing SBMP than for RCs containing SB. Specimens stored in wine showed a clear pattern of degradation, especially in the control group, and surface degradation seemed to be less intense for specimens prepared with SBMP and SB than for specimens without. Specimens stored in water did not show clear evidence of surface degradation. RDMIT appears to be an interesting approach to reduce ΔE * in RCs over time without negative effects on the translucency of the material. However, the modeling liquid should feature a hydrophobic composition, similar to that used in the SBMP group, the achieve the best results.

Effects of adhesive used as modeling liquid on the stability of the color and opacity of composites

“…Therefore, several studies have evaluated the color stability of composites subjected to staining solutions. In the most of these studies, the specimens have been immersed in coffee, grape juice, wine, and other beverages uninterruptedly for long periods of time (hours or days) . However, the exposure of composite restorations to beverages in vivo occurs through several cycles of a few seconds each.…”

“…However, obtaining satisfactory esthetic restorations depends on both clinicians’ skill and the physical properties of the composite, including its handling characteristics. As the stickiness of several composites can hinder the insertion and sculpting procedures, some clinicians have used low viscosity materials as modeler liquids to facilitate the building up of the restoration by reducing the surface tension of the composite . Moreover, the low viscosity resin might penetrate through any porosity created during the incremental insertion of the composite, helping to reduce the defects on the restoration's body and ultimately improving the mechanical properties and color stability …”

“…The hydrophilic characteristics of these monomers and solvents can make the restoration more prone to absorbing staining pigments and to changing color over time. Therefore, non‐solvated and more hydrophilic resin adhesives (ie, Scotchbond Multipurpose) have been found to be preferable as the modeler liquid and have shown satisfactory results in prior studies . However, more simplified universal adhesives have increased in popularity among clinicians, and there is also a lack of information available on their use as a modeling liquid for composite restorations.…”

“…Another important point is that the beneficial effects of the modeler liquid include reduction of defects present in the composite restoration . Most of the laboratorial studies evaluating color stability have examined composite specimens immersed in staining solutions over a particular period of time . Despite the fact that this protocol does yield color changing in specimens, the use of a constant temperature does not reproduce the dimensional alterations the material undergoes when patients drink hot or cold beverages .…”

“…As the stickiness of several composites can hinder the insertion and sculpting procedures, some clinicians have used low viscosity materials as modeler liquids to facilitate the building up of the restoration by reducing the surface tension of the composite. [3][4][5][6][7] Moreover, the low viscosity resin might penetrate through any porosity created during the incremental insertion of the composite, helping to reduce the defects on the restoration's body and ultimately improving the mechanical properties and color stability. 3,5,7 In fact, some manufacturers have introduced into the market specific liquids for modeling composites; however, the use of resin adhesives has gained popularity for this purpose as it does not require any additional material during the restoration procedure.…”