Bond strength comparison of a fiber-reinforced composite resin: Different dentin conditions and preparation techniques.

This study aimed to compare the bond strength of a fiber-reinforced composite resin with traditional and bulk-fill composite resins under different dentin conditions and preparation techniques. Eighty molar teeth, excluding the mesio-distal half of the occlusal dentin surfaces of each teeth, were isolated with acid-resistant nail varnish and stored in a demineralisation solution (pH 4.5). After mechanical removal of the varnish, the teeth were buried in acrylic resin blocks. In every composite resin group, one-half of the specimens were prepared with a diamond bur and another half with Er: YAG laser. Then, the specimens were divided into four groups of composite resins (Filtek Z250, G-aenial Posterior, SonicFill 2, Ever X Posterior) (n = 10). Shear bond strengths were measured using a universal testing device, and failure types were determined with stereomicroscope images. SEM images were obtained at 1000× magnification. Data were analyzed using a three-way analysis of variance (ANOVA), and Bonferroni correction was used for multiple comparisons (p = .05). Differences in the dentin surface affected the bond strength results (p < .05), whereas there was no significant difference between cavity preparation methods (p > .05). EverX Posterior showed the highest bond strength results. Within the limitations of this study, fiber-reinforced composite resin exhibited successful bond strength results in addition to improved mechanical properties. RESEARCH HIGHLIGHTS: Fiber-reinforced composite had successful bond strength values. Bond strength values of sound dentin groups were higher than those of caries-affected dentin groups. The use of an Er: YAG laser for preparation did not lead to insufficient bond strength results.

The radiopacity of single-shade composite resins: A comparative evaluation.

OBJECTIVE: The aim of this study was to evaluate the radiopacity of single-shade composite resins with group and multi-shade composite resins via a digital image analysis. MATERIALS AND METHODS: Disc-shaped (5 mm in diameter, 2 mm in thickness) specimens were prepared with one multi-shade (Estelite Sigma Quick-ESQ), four single-shade (Omnichroma-OC, Charisma Topaz One-CTO, Vitra Unique-VU, and ZenChroma-ZC), three group-shade (G-aenial Achord-GA, Optishade-OS, and Estelite Asteria-EA), and one posterior composite resin (Estelite Posterior-EP) (n = 3). A radiographic image of all the specimens, an aluminum step-wedge, and a 2 mm thick tooth section were taken. Mean gray values (MGV) of the specimens, enamel, and dentin were calculated by ImageJ software. Composition analysis was performed with EDS, and SEM images (×10,000) were obtained. The data were analyzed with Kruskal-Wallis and Post hoc adjusted Bonferroni analysis (p = 0.05). RESULTS: The mean MGV of CTO, the highest of all test groups, was significantly higher than OC and dentin (p = 0.04 and p = 0.009, relatively). The lowest mean MGV was also observed in a single-shade group, OC. EDS analysis showed that the tested materials comprised various radiopaque elements. CONCLUSIONS: All of the single-shade and group-shade groups exceeded the MGV value of dentin, which is clinically expected from any restorative material. CLINICAL SIGNIFICANCE: The radiopacity properties of various single-shade composite resins which as a category is a rising trend in esthetic dentistry were investigated. It is important for clinicians to be aware of novel materials' physical qualities including radiopacity, a daily clinical criteria for restorative materials.

Effects of dyes used in photodynamic therapy on color stability of composite resins.

PURPOSE: The aim of this study was to evaluate the effect of dyes used in photodynamic therapy (PDT) on color changes of resin-based composites (RBCs). METHODS: A total of 120 composite discs were made of microfilled, nanohybrid, and nanoceramic RBCs, and the CIE Lab system was used to assess initial colors with a spectrophotometer. Photosensitizers were used in accordance with the experimental design, as follows: MB (methylene blue), TB (toluidine blue), ICG (indocyanine green), and control (no dye). The samples were irradiated with a 940-nm diode laser. After irradiation, the photosensitizers were removed with distilled water (∆E1) and sodium hypochlorite (∆E2), and final colors were measured. Data were analyzed by the three-way ANOVA and Bonferroni tests (α = 0.05). RESULTS: There was no statistically significant difference between the ICG and control groups; however, the TB and MB groups exhibited the strongest staining. The nanohybrid RBC exhibited the greatest color change, and there were no significant differences between the microhybrid and nanoceramic RBCs. After NaOCl irrigation, ΔE2 values decreased to clinically acceptable values (ΔE2 < 3.3). CONCLUSION: The intensity of staining of the RBCs differed according to the type of photosensitizer used and the content of the composite resin. The irrigant NaOCl was effective in removing discoloration.

Effects of photodynamic therapy with indocyanine green on Streptococcus mutans biofilm.

BACKGROUND: The current procedures for treating tooth decay are not always guaranteed to successfully remove all microorganisms which cause disease. For elimination of bacteria and prevention of their effects, different methods are recommended, such as antibacterial materials and cavity disinfectants. The aim of this study was to compare the antibacterial activity of photodynamic therapy (PDT) using diode laser with indocyanin green (ICG) on Streptococcus (S.) mutans biofilm with conventional methods. METHODS: Ninety human molars were divided into 9 groups: negative control, positive control, CHX, NaOCl, gaseous ozone, erbium (Er):YAG laser, diode laser, and indocyanin green/ICG, and PDT. Cavities were then cut into the teeth (2 per tooth, 20 cavities per group) and sterilized. For all of the groups, with the exception of the negative control group, 105 CFU/mL of the active S. mutans culture were inoculated into the cavities and then incubated at 37 °C for 72 h. Then, dentin chips (25 ± 5 mg) were collected from cavity walls and spread on Mueller-Hinton agar media after decimal dilution. The colonies were counted after incubation at 37 °C for 24 h. RESULTS: All the treatments significantly reduced the number of S. mutans compared with the positive control group (p < 0.05). The antimicrobial effectiveness of CHX, NaOCl, ozone, PDT, Er:YAG laser, and diode laser groups were similar. The lowest bacterial reduction was observed in the ICGgroup. CONCLUSIONS: This work concludes that PDT using diode laser with ICG may be suggested on the cavity disinfection after caries excavation as an alternative to conventional methods.

Effects of Novel Finishing and Polishing Systems on Surface Roughness and Morphology of Nanocomposites.

OBJECTIVES: The purpose of this in vitro study was to evaluate the effects of different finishing/polishing techniques on the surface roughness of nanocomposites after thermocycling aging. MATERIALS AND METHODS: Five contemporary resin-based composites (Clearfil Majesty ES-2, Filtek Z550, Estelite∑Quick, Zenit, Filtek Z250) were tested. For each resin-based composite, 50 disc-shaped specimens were prepared and groups were divided into five subgroups according to the finishing/polishing methods (n = 10): control, finishing/polishing brush, finishing/polishing disc, and two different finishing/polishing wheels. Before and after aging, the surface roughness of specimens was measured. For each treatment method two samples were analyzed using a scanning electron microscope. Two-way analysis of variance and paired samples t-tests were used to evaluate the data and the means were compared by Bonferroni tests (p ≤ 0.05). RESULTS: Before aging, the Filtek Z250 resin with the Mylar strip group showed the lowest surface roughness (Ra) value (0.13 ± 0.03 µm, p < 0.05) and the Clearfil Majesty ES 2 resin with Occlubrush finishing/polishing system showed the highest (0.7 ± 0.13 µm, p < 0.05). After aging, the Clearfil Majesty ES 2 resin with the Mylar strip group showed the highest surface roughness (Ra) value (0.96 ± 0.4 µm) and the Clearfil Majesty ES 2 resin with the Sof-Lex aluminum oxide disc finishing/polishing system showed the lowest surface roughness (Ra) value (0.25 ± 0.06 µm, p < 0.05). CONCLUSIONS: Composite type and finishing/polishing method significantly affected the surface roughness of composites before and after thermocycling aging. CLINICAL SIGNIFICANCE: There were significant interactions between finishing/polishing methods and composite types for surface roughness. The results give clinicians some flexibility in choosing appropriate finishing/polishing techniques for each resin composite material. (J Esthet Restor Dent 28:247-261, 2016).