Selinsu Öztürk

Background: To evaluate the effects of in-office bleaching treatment on color and surface roughness of nano-hybrid resin composites (NH-RC) and the impact of different repolishing procedures following bleaching. Methods: Sixty disc-shaped (8 × 2 mm, A2) specimens were prepared using 2 different NH-RC (Charisma Topaz One, Kulzer, Germany; Parion, Dentac, Türkiye). Initial finishing and polishing processes were completed with 4-stage discs (OptiDisc, Kerr). Excluding the control groups (n = 10), 40 specimens were subjected to 2 sessions of office bleaching (40% hydrogen peroxide, Opalescence Boost, Ultradent), each consisting of three 20-minute applications at 3-day intervals. After 24 hours, half of the bleached specimens from each composite group were repolished with a 4-step disc system (OptiDisc, Kerr), and the others with diamond-impregnated silicone rubbers (DiaComp Plus Twist, Eve). Surface roughness (Ra) was recorded with a profilometer (SJ-210, Mitutoyo, Japan) and color was analyzed with a spectrophotometer (Easyshade V, VITA, Germany) at baseline, after bleaching, and after repolishing, respectively. Color changes (ΔE) were calculated with the CIEDE2000 formula. The data were evaluated statistically by 2-way ANOVA and Bonferroni test (P < .05). Results: In Parion, bleaching significantly increased surface roughness (P < .05) and ΔE₁-ΔE₂ values (>1.8; P < .001), exceeding the acceptability threshold, whereas the control remained below the 0.8 perceptibility limit. Repolishing reduced roughness (P < .05) and ΔE₃ values (0.8- 1.8) regardless of the repolishing system used, indicating acceptable matches. In Charisma Topaz One , no group showed ΔE₀₀ ≥ 1.8 or significant roughness changes (P > .05). Conclusion: Bleaching affects resin composites differently depending on their composition, but repolishing enhances color and surface properties regardless of the system used.

Aim: This in vitro study aimed to compare the degree of conversion, flexural strength, and microhardness of a recently developed flowable resin composite in clinical use and to evaluate polymerization and mechanical characteristics. Materials & Methods: ZENIFLOW (65% filler ratio by volume) and Dynamic flow (60% filler ratio by volume) composites (President, Germany) were subjected to a three-point bending test (n=10) to determine flexural strength (FS) and flexural modulus (FM); Vickers micro-hardness (VHN) (n=5) and hardness-ratio (HR) were determined with a microhardness tester from bottom/top surfaces after 15-days of storage in distilled water at 37ºC. The degree of conversion (DC) was assessed by using Fourier Transform Infrared Spectroscopy (FTIR) (n=5). All samples were polymerized with a polywave LED curing unit with 1000 mW/cm2 (Valo Cordless, Ultradent) for 20 s. Polishing procedures were performed with 4-step polishing discs (BISCO, USA). The fractured surfaces formed after flexural strength assessment were examined with a stereomicroscope (Leica MZ7.5, Germany) and a Scanning Electron Microscope (SEM) (Zeiss EVO MA10, Germany). Independent samples t-test was used to compare the values according to the groups. The significance level was set at p

Biomimetic restorative protocols aim to preserve natural tooth structure while enhancing restoration longevity. This in vitro study aimed to evaluate the shear bond strength (SBS) in the repair of additively and subtractively manufactured CAD/CAM materials using bulk-fill resin composites and to assess the effect of thermocycling. Forty rectangular specimens (14.5 × 7 × 3 mm) were prepared from Grandio Blocs (GB, VOCO) and VarseoSmile Crown^Plus (VS, BEGO), and thermocycled (5000 cycles, 5–55 °C, 20 s dwell time). All surfaces were roughened with 50 μm Al₂O₃. Samples were repaired using VisCalor (VCB, VOCO) and Charisma Bulk Flow One (CBO, Kulzer) composites (n = 10 per group) with their respective adhesives. Each group was further divided into immediate and post-thermocycling subgroups. All specimens were tested under shear force until failure, and failure types were examined under a stereomicroscope. Representative samples were examined by SEM to evaluate filler morphology. Statistical analysis was performed with SPSS v23 (p < 0.05). No statistically significant differences in SBS were found between groups (p > 0.05). Mean SBS values were highest in VS-CBO and lowest in GB-CBO. Cohesive failures were more frequent in immediate groups, while adhesive failures predominated after thermocycling. Bulk-fill composites did not influence the repair bond strength of indirect materials. Thermocycling affected the failure type, though not the SBS values.

European Journal of Research in Dentistry | Volume: 9 Issue: 1

This in-vitro study aimed to evaluate the degree of conversion (DC) of dual-cured luting cement (Bifix QM, VOCO) and flowable composite (Grandio Flow, VOCO) under lithium disilicate glass-ceramic (IPS e.max CAD, Ivoclar Vivadent) and hybrid ceramic (Grandio Blocs, VOCO; Cerasmart, GC) CAD-CAM blocks with different thicknesses. Contrast ratio (CR), translucency (TPab, TP00), and opalescence (OP) parameters of 30 disc-shaped CAD-CAM blocks (n = 5) prepared with two different thicknesses (1.5 and 2 mm) and 8 mm diameters were calculated using a spectrophotometer (VITA Easyshade V, Zahnfabrik). A total of 36 Bifix QM and Grandio Flow samples were prepared at 100 μm thickness using a specific setup by polymerizing from the top of the blocks. Following immersion in distilled water at 37 °C for 24 h, luting materials were examined by Fourier Transform Infrared Spectroscopy for DC calculation. Data were analyzed using One-way ANOVA, Kruskal Wallis, Mann Whitney U, and Independent Samples t-tests (p < 0.05). It was observed that, as the block thickness increased TPab, TP00, and OP decreased, while CR increased. There was no significant difference between the DC of Bifix QM and Grandio Flow when 1.5 mm blocks were used in all groups (p > 0.05). DC of Grandio Flow was significantly higher than Bifix QM under 2 mm-IPS e.max CAD (p = 0.011). The translucency of the CAD-CAM blocks varies depending on their thickness. However, there was no significant difference in the DC of the luting materials depending on the block thickness. Further studies are needed on the use of flowable resin composites as luting material.

The use of multivitamins has become widespread globally, yet there is a scarcity of studies investigating their impact on resin composite restorations. This study aimed to evaluate the effect of an effervescent multivitamin tablet on micro-hybrid dental resin composites’ surface roughness and color. Fifty disc-shaped samples (8 × 2 mm, shade A2; n = 10) were prepared and polished using five different micro-hybrid resin composites (Pergamon, Dentac, Turkey; Estelite Posterior, Tokuyama, Japan; Geanial Anterior, GC, Japan; Charisma Opal, Kulzer, Germany; Beautifil II, Shofu, USA). Samples were immersed in 200 mL water to one effervescent multivitamin tablet (Redoxon Triple Action, Bayer) at 24 °C for 2 min a day in 24 h intervals for 30 days. All samples’ surface roughness (Ra) and ΔE(L*a*b) measurements were recorded at the beginning and end of the 30 days. The Wald chi-square and a two-way ANOVA were used for statistical analysis (significance level p < 0.05). The resin composite type and exposure to the multivitamin had a statistically significant effect on Ra values (p < 0.05). The resin composite type had a statistically significant effect on ΔE values, likely due to the higher mean value of BII (p = 0.040). The surface roughness and color of resin composites can be affected by multivitamins with a pH value of 3.0. Therefore, it is important to consider the patient’s routine vitamin intake during resin composite selection. Additional research is required to explore the properties of different dental restorative materials.