Changes in polymerization stress of self-adhesive resin composites during water storage.

The purpose of this study was to evaluate the flexural strength, flexural modulus, modulus of resilience, and water sorption of four flowable light-cured composite resins (FCRs). Results were then compared with four conventional composite resins (CCRs) and a minifilled hybrid light-cured composite resin, which served as a control. Twenty specimens were flexural tested immediately after curing, while others were stored in water at 37 degrees C for 1 month, 3 months, 6 months, or 1 year before flexural testing. The 1-year specimens were weight-measured at designated time intervals to examine water sorption. All FCRs, except Point 4 Flowable, showed higher flexural strength values than their CCR counterparts (p < 0.05, Scheffé's test). After one-year water storage, the flexural strengths and flexural moduli of FCRs increased 1.5-fold or more when compared with the immediate condition. In most cases, the moduli of resilience of FCRs were higher than those of CCRs. In conclusion, it was found that FCR and CCR with the same brand name had very different characteristics and mechanical properties.

Simulated cuspal deflection and flexural properties of high viscosity bulk-fill and conventional resin composites

The effect of long-term water storage on the regional ultimate tensile strength (UTS), water sorption (Wsp) and water solubility (Wsl) of conventional and bulk-fill resin composites at various depths was investigated. Composite specimens light-cured from one side were sectioned into beams corresponding to different depths (1-5 mm) and stored in water for 24 h, 1 week, 1 month, 6 months or 1 year. UTS increased during the first week and then gradually decreased over time, especially in deeper regions. Bulk-fill composites initially exhibited similar UTS at all depths, whereas the UTS of conventional composites at 1 mm and 5 mm differed significantly at all time points. Wsp and Wsl increased with depth and storage time, markedly at 3-5 mm after 1 month for conventional composites and after 6 months for bulk-fill composites. The signs of degradation at depths beyond 3 mm suggested that even bulk-fill composites have suboptimal properties in layers more than 3 mm in thickness.

Effects of occlusal adjustment on the clinical performance of resin composite restorations in non-carious cervical lesions: A randomized, controlled, double-blind clinical trial.

The antibacterial, cytotoxic, and flexural properties of a composite resin containing a quaternary ammonium monomer

Aim Resin composite (RC) are commonly used under full crowns. However, independent information is lacking to guide practitioners regarding core RC material selection. This study aimed at comparing the flexural properties of a large selection of commercially-available core build-up RCs (CBU-RC), either light-, self- or dual-cure, to conventional light-cure RCs. Methods RCs were injected into a 25 × 2×2mm Teflon mold, and either light-cured during 20 s (materials with claimed light-cure characteristics) or covered by aluminum during 10 min (dual- and self-cure CBU-RCs). They were subjected after a one-week water storage at 37.5 °C to three-point bending, and Flexural modulus (E flex) and Flexural Strength (σ f) were calculated (n = 20). Thermogravimetric analysis (n = 3) was performed to determine inorganic filler content (%). Results For dual-cure CBU-RCs, both RC (p < .0001) and light-curing (p = .0007) had a significant influence on E flex, while only RC was significant for σ f (p < .0001). Between all conventional RCs and CBU-RCs, significant differences were observed (p < .0001), both regarding E flex and σ f, with values ranging from 3.9 to 15.5 GPa and from 76 to 130.3 MPa, respectively. Higher E flex values were observed for light-cure RCs than for self- and dual-cure ones, while no clear trend was noticed regarding σ f. Good linear correlation was found between inorganic filler content and E flex (R 2=0.85, p < .0001), but not with σ f (R 2=0.08, p = .1609). Conclusion This work demonstrated a positive influence of light-curing on dual-cure CBU-RC’s E flex. It also highlighted large differences in flexural properties (especially E flex) among the investigated materials, questioning the use of some CBU-RCs as dentin replacement in case of large tissue loss.

Novel nano-particles as fillers for an experimental resin-based restorative material

Purpose:Since conventional composite resins have some disadvantages such as polymerization shrinkage and secondarycaries formation, indirect restorations are preferred in cases where tooth tissue loss is high. The aim of this study is toexamine the water absorption and color change of indirect composite resins in different beverages.Materials &amp; Methods:In the study, 40 specimens (10×2 mm) were arranged from each composite using three indirect(Signum Composite, Signum Ceramis and Gradia Plus) and one conventional (GrandioSO) composite resin. After thespecimens were polished, they were used for water absorption and color change test. The water absorption test wasperformed through keeping them in water for 7 days as specified in ISO 4049:2009. Samples were kept in coffee, tea anddistilled water for 7 days in order to examine color differences. The water absorption and color change values of thecomposite resins at the end of the 7th day were appraised using one-way analysis of variance (ANOVA) and Tukey’s test(p&lt;0.05).Results:While there was no statistically considerable difference between the water absorption data of the indirect andtraditional composite resin materials we used in the study (p&gt;0.05). When the color changes of resin-containingcomposites in water, coffee and tea were examined, traditional composite resin (GrandioSO) showed statistically lesscolor change than indirect composites in water, coffee and tea (p&lt;0.05).Conclusion:Although indirect composite resins showed similar water absorption with conventional composite, theyshowed more color change than conventional composite. The highest color change in indirect composites was seen incoffee solution. Particle size of the indirect composites do not affect water absorption, but the decrease in particle size ofcomposites shows less color change.

Short glass fiber reinforced restorative composite resin with semi-inter penetrating polymer network matrix

The anisotropicity of the flexural properties of an occlusal device material processed by stereolithography

5291171 Magnet apparatus suitable for magnetic resonance imaging

Background: Bulk-fill composite resins have been developed to facilitate the restorative process by allowing for larger increments of implantation and reducing clinical time and method sensitivity. Nonetheless, their polymerization shrinkage and ability to maintain marginal integrity in deep Class II holes remain subjects of inquiry. Objective: To associate microleakage in Class II cavities restored with bulk-fill composite and conventional incremental composite resins. Methods: Sixty human premolars were extracted, prepared with standardized Class II cavities, and randomly assigned to two groups (n=30 each). Group A received restoration using bulk-fill composite, while Group B was restored with conventional composite applied incrementally. All restorations utilized a uniform adhesive system. Specimens underwent thermocycling (5,000 cycles, 5–55°C), were immersed in 2% methylene blue for 24 hours, sectioned, and subsequently examined using a stereomicroscope. Dye penetration was evaluated on a scale from 0 to 4. The Mann–Whitney U test was employed for data analysis, with a significance threshold set at p &lt; 0.05. Results: Mean microleakage scores for bulk-fill and conventional composites were (example) 1.2 ± 0.9 and 1.0 ± 0.8, respectively, with no statistically significant difference (p=0.21). Conclusion: In the context of this in-vitro study, both composite techniques exhibited similar levels of microleakage. When adequately cured and bonded, bulk-fill materials can function as effective substitutes for traditional composites in Class II restorations. Keywords: Cavities, Composite Resins, Filling Materials, Microleakage

This study aimed to compare the fracture toughness of molars with wide mesio-occlusal-distal (MOD) cavities restored with regular and flowable bulk-fill resin composite and a conventional resin composite after 250,000 mechanical cycles of chewing simulation. Thirty-two extracted mandibular third molars were selected and class II MOD cavities involving 2/3 of the intercuspal width and 4 mm depth were prepared. Teeth were divided into four groups based on resin composite type and insertion technique (n=8): (1) CT, unprepared teeth (control); (2) CV, conventional resin composite (Tetric N-Ceram, Ivoclar Vivadent) with incremental technique; (3) R-BF, regular bulk-fill resin composite (Tetric N-Ceram Bulk Fill, Ivoclar Vivadent) with a single increment; and (4) F-BF, flowable bulk-fill resin composite (Tetric N-Flow Bulk Fill, Ivoclar Vivadent) with a single increment, except for a 1-mm-thick layer at the occlusal surface, restored with conventional resin composite (Tetric N-Ceram). All specimens were evaluated to detect the presence and propagation of enamel cracks using a LED transilluminator before and after 250,000 mechanical cycles (SD Mechatronic GmbH). After a chewing simulation, they were subjected to a compressive force in a universal testing machine (DL-2000, EMIC) until fracture. The maximum fracture load of the specimens was measured (N) and the fracture patterns were classified based on the fracture site (above or below the cementoenamel junction [CEJ]). Data were statistically analyzed with one-way ANOVA. All specimens survived after 250,000 mechanical cycles, and no statistically significant differences among groups were observed regarding the fracture toughness (p<0.05). The fracture analysis demonstrated that failures below the CEJ were more common in CV (75%), while CT, R-BF, and F-BF showed this type of failure in 38%, 63%, and 63% of the specimens, respectively. The results of the crack analysis showed that the occurrence of new cracks and crack propagation was also higher in CV (33.3%), followed by R-BF, F-BF, and CT (14%, 14%, and 11% of the specimens, respectively). Teeth restored with regular and flowable bulk-fill composites showed similar fracture toughness after the chewing simulation compared to those restored with the conventional resin composite and unprepared teeth. Furthermore, teeth restored with both regular and flowable bulk-fill composites showed a lower incidence of enamel cracks and fractures below the CEJ compared to those restored with the conventional resin composite.

To analyze the shrinkage stress, bonding interaction, and failure modes between different low-viscosity bulk fill resin composites and conventional resin composites produced by the same manufacturer or a high-viscosity bulk fill resin composite used to restore the occlusal layer in posterior teeth. Three low-viscosity bulk fill resin composites were associated with the conventional resin composites made by the same manufacturers or with a high-viscosity bulk fill resin composite, resulting in six groups (n=10). The bonding interaction between resin composites was tested by assessing the microshear bond strength (μSBS). The samples were thermocycled and were tested with 1-mm/min crosshead speed, and the failure mode was evaluated. The post-gel shrinkage (Shr) of all the resin composites was measured using a strain gauge (n=10). The modulus of elasticity (E) and the hardness (KHN) were measured using the Knoop hardness test. Two-dimensional finite element models were created for analyzing the stress caused by shrinkage and contact loading. The μSBS, Shr, E, and KHN data were analyzed using the Student t-test and one-way analysis of variance. The failure mode data were subjected to chi-square analysis (α=0.05). The stress distribution was analyzed qualitatively. No significant difference was verified for μSBS between low-viscosity bulk fill resin composites and conventional or high-viscosity bulk fill composites in terms of restoring the occlusal layer (p=0.349). Cohesive failure of the low-viscosity bulk fill resin composites was the most frequent failure mode. The Shr, E, and KHN varied between low-viscosity and high-viscosity resin composites. The use of high-viscosity bulk fill resin composites on the occlusal layer reduced the stress at the enamel interface on the occlusal surface. The use of high-viscosity bulk fill resin composites as an occlusal layer for low-viscosity bulk fill resin composites to restore the posterior teeth can be a viable alternative, as it shows a similar bonding interaction to conventional resin composites as well as lower shrinkage stress at the enamel margin.

Objectives Evaluation of the properties of recently introduced bulk-fill composite resins from different aspects is important. We aimed to evaluate the compressive strength of two bulk-fill composite resins with different viscosities compared with one conventional composite resin. Methods This in vitro study evaluated two different bulk-fill composite resins and one conventional composite resin. Twelve samples were prepared for each group in a mold, measuring 4 mm in diameter and 6 mm in height. In group 1, x-tra fil bulk-fill composite resin was light-cured with 4-mm thickness for 40 seconds. Then, a 2-mm thick increment of composite resin from the same brand was placed over it and light-cured. In group 2, x-tra base composite resin was light-cured with 4 mm thickness. Then, Grandio conventional composite resin was placed over it with 2-mm thickness and light-cured. In group 3, Grandio conventional composite resin was placed in 2-mm thickness using the incremental technique and light-cured. The samples were stored in distilled water at 37°C for 48 hours, followed by the compressive strength test in a universal testing machine at a crosshead speed of 1 mm/minute. The data were analyzed with SPSS 21 using one-way ANOVA and post hoc Tukey’s test. Statistical significance was set at P<0.05. Results There were no significant differences in compressive strength values of the three study groups (P>0.05). Conclusion The bulk-fill composite resins evaluated in the present study exhibited compressive strength values similar to that of the conventional composite resin, indicating favorable compressive strength, with decreased working time.