Simulated Cuspal Deflection and Flexural Properties of Bulk-Fill and Conventional Flowable Resin Composites

Effect of using different materials and restorative techniques on cuspal deflection and microleakage in endodontically treated teeth

BACKGROUND

This study aimed to evaluate the effects of different restorative techniques and materials on cuspal deflection and microleakage in MOD restorations. Eight groups were tested using incremental and bulk-fill techniques, with or without fiber reinforcement. The restorative materials included Filtek Z250 and Filtek Bulk-fill Posterior, while reinforcement materials such as Interlig glass fiber, EverX Posterior, and Surefill SDR were incorporated to assess their impact.

METHODS

In total, 96 freshly extracted, sound human maxillary first premolars were selected and stored in 0.1% thymol solution at 37 °C. The teeth were randomly assigned into eight groups (n = 12). Standardized MOD cavities were prepared, followed by endodontic treatment and sealing with glass ionomer cement. The groups were as follows: Group 1-Filtek Z250 applied incrementally in 2-mm layers; Group 2-U-shaped Interlig glass fiber followed by incremental Filtek Z250; Group 3-Filtek Bulk-fill Posterior using the bulk technique; Group 4-U-shaped Interlig glass fiber followed by Filtek Bulk-fill Posterior; Group 5-EverX Posterior followed by incremental Filtek Z250; Group 6-EverX Posterior followed by Filtek Bulk-fill Posterior; Group 7-Surefill SDR followed by incremental Filtek Z250; and Group 8-Surefill SDR followed by Filtek Bulk-fill Posterior. Cuspal deflection was measured using a digital micrometer with 0.05 μm precision. Microleakage was assessed using a 0.5% basic fuchsin dye solution at 37 °C for 24 h, followed by sectioning and examination under magnification.

RESULTS

The lowest mean cuspal deflection was observed in Group 2 (15.8 μm), while the highest was in Group 5 (27.2 μm). Statistically significant differences were observed in cuspal deflection across the groups and over time (p < 0.05). Significant differences in microleakage scores were also found among the groups, indicating the impact of restorative materials and techniques on these outcomes (p < 0.05).

CONCLUSION

This study demonstrated that Filtek Z250 and Filtek Bulk-fill Posterior showed different effects on cuspal deflection and microleakage. The use of glass fiber and EverX Posterior improved restoration performance by reducing polymerization effects. Surefill SDR also reduced cuspal deflection due to its low polymerization shrinkage. Clinically, selecting the appropriate restorative materials and techniques based on the extent of tooth structure loss can improve long-term outcomes.

The chemical and optical stability evaluation of injectable restorative materials under wet challenge

OBJECTIVES

To investigate and compare the chemical and optical stability of four restorative composite materials: two injectable resins, one flowable resin and one compomer.

METHODS

Two injectable nano-filled composite resins: G-aenial Universal (GU) and Beautifil Injectable XSL (BI), a flowable composite resin: Filtek Supreme Flowable (FS) and a compomer: Dyract Flow (DF), in A2 shade were tested and compared. Water sorption and solubility were conducted according to ISO4049:2019 standard; ICP-OES and F-ion selective electrode were used to test the elemental release; Degree of conversion (DC) was obtained by using FTIR; water contact angle was obtained by static sessile drop method, and a spectrophotometer was used for optical properties (ΔE⁎, ΔL⁎ and TP). SPSS 28.0 was used for statistical analysis and the significant level was pre-set as α = 0.05.

RESULTS

GU performed the best in water sorption and solubility, FS had the lowest elemental release, the best colour stability, and the highest DCIM and DC24-h. DF, the compomer had the lowest, and GU and BI, the injectable composites had the largest water contact angle, respectively. Correlations were found between water sorption and water solubility.

CONCLUSIONS

The four composite restorative materials showed different chemical and optical behaviours. Overall, composite resins performed better than compomer, while additional laboratory and in vivo tests are necessary to obtain a more comprehensive comparison between injectable and flowable composite resins. Wsp and Wsl are influenced by many common factors, and the values are highly positively related.

CLINICAL SIGNIFICANCE

A comprehensive understanding of materials is crucial before selecting materials for clinical practice. Composite resins rather than compomers are recommended because of their exceptional properties, which make them eligible for a wide range of clinical applications and an elongated lifespan.

Contemporary flowable bulk-fill resin-based composites: a systematic review

Flowable bulk-fill resin-based composites (BF-RBCs) represent a new and interesting alternative for the bulk-fill restorative techniques in the posterior region. However, they comprise a heterogeneous group of materials, with important differences in composition and design. Therefore, the aim of the present systematic review was to compare the main properties of flowable BF-RBCs, including their composition, degree of monomer conversion (DC), polymerization shrinkage and shrinkage stress, as well as flexural strength. The search was conducted following PRISMA guidelines in the Medline (PubMed), Scopus and Web of Science databases. In vitro articles reporting on the DC, polymerization shrinkage/shrinkage stress, and flexural strength of flowable BF-RBCs strength were included. The QUIN risk-of-bias (RoB) tool was used for assessing the study quality. From initially 684 found articles, 53 were included. Values for DC ranged between 19.41 and 93.71%, whereas polymerization shrinkage varied between 1.26 and 10.45%. Polymerization shrinkage stresses reported by most studies ranged between 2 and 3 MPa. Flexural strength was above 80 MPa for most materials. A moderate RoB was observed in most studies. Flowable BF-RBCs meet the requirements to be indicated for bulk fill restoration technique in the posterior region. However, important variations among composition and properties hinder extrapolation of the results to materials different from those reported here. Clinical studies are urgently required to assess their performance under a real working scenario.

[Flexural strength of conventional flowable, bulk fill flowable and highly filled flowable resin composites: in vitro study.]

Objective

To evaluate and compare the flexural strength of conventional flowable, bulk fill flowable and highly filled flowable resins.

Materials and methods

Thirty 2mm x 2mm x 25mm specimens of Tetric N-Flow (TNF), Filtek Bulk Fill Flowable Restorative (FBF) and Beautifil Flow Plus F00 (BFP) flowable resins were made up; they were distributed into three groups according to brand (n=10) and stored in distilled water for 24 hours at 37ºC. The 3-point bending test according to ISO 4049 was performed on a universal testing machine at a speed of 0.5 mm/min until fracture. The results were evaluated with Anova and Tukey tests. P<0.05.

Results

Statistically significant differences were found between the groups with a value of p=0.011. According to the statistical analysis, the groups that showed statistically significant differences were the BFP and TNF groups (p=0.015) and the BFP and FBF groups (p=0.035), while no statistically significant difference was found in the TNF and FBF groups.

Conclusion

The high-filled flowable resin presents better flexural strength compared to the conventional flowable and bulk fill flowable resins, while the conventional and bulk fill flowable resins have no statistically significant difference.

Relationships between Flexural and Bonding Properties, Marginal Adaptation, and Polymerization Shrinkage in Flowable Composite Restorations for Dental Application

To evaluate the flexural and bonding properties, marginal adaptation, and polymerization shrinkage in flowable composite restorations and their relationships, four new generation flowable composites, one conventional, and one bulk-fill flowable composite were used in this study. Flexural properties of the composites and shear bond strength to enamel and dentin for flowable restorations were measured immediately and 24 h after polymerization. Marginal adaptation, polymerization shrinkage, and stress were also investigated immediately after polymerization. The flexural properties, and bond strength of the flowable composites to enamel and dentin were much lower immediately after polymerization than at 24 h, regardless of the type of the composite. Polymerization shrinkage and stress varied depending on the material, and bulk-fill flowable composite showed much lower values than the others. The marginal adaptation and polymerization shrinkage of the composites appeared to have a much stronger correlation with a shear bond strength to dentin than to enamel. The weak mechanical properties and bond strengths of flowable composites in the early stage after polymerization must be taken into account when using them in the clinic. In addition, clinicians should be aware that polymerization shrinkage of flowable composites can still lead to the formation of gaps and failure of adaptation to the cavity regardless of the type of composite.

Bulk Fill Composites Have Similar Performance to Conventional Dental Composites

The aim of the study was to perform comprehensive characterization of two commonly used bulk fill composite materials (SDR Flow (SDR) and Filtek™ Bulk Fill Flowable Restorative (FBF) and one conventional composite material (Tetric EvoCeram; TEC). Eleven parameters were examined: flexural strength (FS), flexural modulus (FM), degree of conversion, depth of cure, polymerisation shrinkage (PS), filler particle morphology, filler mass fraction, Vickers hardness, surface roughness following simulated toothbrush abrasion, monomer elution, and cytotoxic reaction of human gingival fibroblasts, osteoblasts, and cancer cells. The degree of conversion and depth of cure were the highest for SDR, followed by FBF and TEC, but there was no difference in PS between them. FS was higher for bulk fill materials, while their FM and hardness were lower than those of TEC. Surface roughness decreased in the order TEC→SDR→FBF. Bisphenol A-glycidyl methacrylate (BisGMA) and urethane dimethacrylate were found in TEC and FBF eluates, while SDR released BisGMA and triethylene glycol dimethacrylate. Conditioned media accumulated for 24 h from FBF and TEC were cytotoxic to primary human osteoblasts. Compared to the conventional composite, the tested bulk fill materials performed equally or better in most of the tests, except for their hardness, elastic modulus, and biocompatibility with osteoblasts.