Effect of short glass fiber/filler particle proportion on flexural and diametral tensile strength of a novel fiber-reinforced composite

Niobium oxyhydroxide as a bioactive agent and reinforcement to a high-viscosity bulk-fill resin composite

OBJECTIVE

The present in vitro study incorporated niobium oxyhydroxide fillers into an experimental high-viscosity bulk-fill resin composite to improve its mechanical performance and provide it a bioactive potential.

METHODOLOGY

Scanning electron microscopy synthesized and characterized 0.5% niobium oxyhydroxide fillers, demonstrating a homogeneous morphology that represented a reinforcement for the feature. Fillers were weighed, gradually added to the experimental resin composite, and homogenized for one minute, forming three groups: BF (experimental high-viscosity bulk-fill resin composite; control), BF0.5 (experimental high-viscosity bulk-fill resin composite modified with 0.5% niobium oxyhydroxide fillers), and BFC (commercial bulk-fill resin composite Beautifil Bulk U, Shofu; positive control). In total, 10 specimens/groups (8 × 2 × 2 mm) underwent flexural strength (FS) tests in a universal testing machine (Instron) (500N). Resin composites were also assessed for Knoop hardness (KH), depth of cure (DoC), degree of conversion (DC), elastic modulus (E), and degree of color change (ΔE). The bioactive potential of the developed resin composite was evaluated after immersing the specimens into a simulated body fluid in vitro solution and assessing them using a Fourier-transformed infrared spectroscope with an attenuated total reflectance accessory. One-way ANOVA, followed by the Tukey's test (p<0.05), determined FS, DC, KH, and ΔE. For DoC, ANOVA was performed, which demonstrated no significant difference between groups (p<0.05).

CONCLUSIONS

The high-viscosity bulk-fill resin composite with 0.5% niobium oxyhydroxide fillers showed promising outcomes as reinforcement agents and performed well for bioactive potential, although less predictable than the commercial resin composite with Giomer technology.

Biomimetic approach to strengthen the incisal fracture composite build-up: an in vitro study

OBJECTIVE

Incisal composite build-up shows a high failure susceptibility. The incorporation of fiber-reinforced composite (FRC) during composite restoration could improve its strength. Hence the study was planned to compare the effect of various positions of FRC on the strength of composite resin incisal build-ups.

METHODS

In maxillary incisors (n = 90), 3 mm of the incisal edge was cut and teeth were categorized into three groups based on the location and number of fibers used during incisal composite build-up - Group I: composite resin; Group II: composite resin and a single fiber palatally and Group III: composite resin along with two fibers palatally.

RESULTS

The data showed that group II had the maximum load-bearing values followed by group I and group III.

CONCLUSION

Within the confines of our study, it can be concluded that the addition of FRC to the conventional incisal composite build-up increased the overall strength restoration. Such composite restoration reinforced with a single fiber on the palatal side showed the highest load-bearing capacity compared to two fibers reinforced and unreinforced composites. The common mode of failure in group I was in composite resin, in two fibers reinforced at fibers-composite junction, and in one fiber reinforced composite was in the remaining part of the tooth.

Effect of nanofibers as reinforcement on resin-based dental materials: A systematic review of in vitro studies

This systematic review provides an update on the effect of nanofibers as reinforcement on resin-based dental materials. A bibliographic search was conducted in MEDLINEPubMed, Embase, Web of Science, Scopus, BVS (LILACS, BBO e IBECS), Cochrane, LIVIVO, and gray literature (BDTD) to identify relevant articles up to May 2021. In vitro studies that evaluated and compared the mechanical properties of nanofibers resin-based composite materials, were eligible. No publication year or language restriction was applied, and methodological quality was assessed using two methods. In a total of 6100 potentially eligible studies, 81 were selected for full-text analysis and 35 were included for qualitative analysis. Of the 35 included studies, a total of 29 studies evaluated the flexural strength (FS) of the materials. These groups were distinguished according to the resin-based materials tested and nanofiber types. Most of the studies evaluated materials composed of glass fibers and demonstrated higher values of FS when compared to resin-based materials without nanofibers. The incorporation of nanofibers into resin-based dental materials improved the mechanical properties compared to resin-based materials without nanofibers, suggesting better performance of these materials in high-stressbearing application areas. Further clinical studies are required to confirm the efficacy of resin-based materials with nanofibers.

Short fiber-reinforced resin-based composites (SFRCs); Current status and future perspectives

One technique for placing of resin-based composite for large posterior cavities is the use of short fiber-reinforced resin-based composite (SFRC) to replace dentin in a biomimetic approach. As endurance under mastication cycles is a significant consideration in the clinical success of resin-based composite posterior restorations, the use of SFRC as a base material may prevent restorative fracture due to the fibers' effectiveness in stopping cracks. This review article specifies the characteristics of SFRC and describes the major underlying mechanisms of short fiber reinforcement for resin-based composite. Insights are further taken from laboratory studies used to define the short fiber-related properties of resin-based composite and the performance of currently available materials, focusing on aspects that are relevant to the reinforcement of resin-based composite. Finally, future standpoints on the development of SFRCs with nano fibers and different resin monomers, and their role in digital dentistry, are discussed.

Development of a fiber-reinforced material for fiber posts: Evaluation of stress distribution, fracture load, and failure mode of restored roots

STATEMENT OF PROBLEM

The biomechanical behavior of post-restored roots with an experimental fiber-reinforced composite resin is unknown.

PURPOSE

The purpose of this in vitro study was to investigate the biomechanical behavior of an experimental composite resin (3-mm short glass fiber incorporated in methacrylate matrix with filler particles) used to produce the custom post itself or to reline fiber posts.

MATERIAL AND METHODS

Four testing groups (n=10) were created according to the root restoration method: FG, commercially available fiber post; FG+RC, fiber post relined with conventional composite resin; FG+EXP, fiber post relined with the experimental composite resin; and EXP, a custom post made of experimental composite resin. A three-dimensional finite element linear elastic analysis was performed by using geometric representations of groups, and the results were analyzed by von Mises (σ_vM) and maximum principal stress criteria. In sequence, 40 bovine incisors were assigned to these groups and subjected to a fracture load test (Instron 5965; 0.5 mm/min), and the failure mode was determined.

RESULTS

The EXP group showed more homogeneous stress distribution for σ_vM. ANOVA and the Tukey honestly significant difference (HSD) tests showed significant differences (P<.001) in fracture load (mean ±standard deviation; different superscript letters indicate statistical difference): FG+EXP (669.5 ±107.7)^A; FG (620.7 ±59.2)^A; EXP (506.5 ±27.0)^B; FG+RC (452.7 ±81.6)^B. No differences were found for failure mode (P=.595).

CONCLUSIONS

The experimental composite resin significantly increases fracture load when used to reline commercially available fiber posts and, irrespective of its use, presented lower stress concentration.

Effects of pontic span and fiber reinforcement on fracture strength of multi-unit provisional fixed partial dentures

Background/purpose

Clinically, PMMA resin is extensively used for fabricating provisional FPDs. However, fracture often occurs due to the unsatisfactory mechanical strength, especially within connectors of long-span provisional FPDs. The purpose of this study is to evaluate the fracture load of fiber-reinforced provisional FPDs with various pontic span lengths, and to identify the most suitable span length for fiber-reinforced long-span provisional FPDs.

Materials and methods

Fifty-six provisional FPDs with various pontic span lengths were fabricated. Seven samples from each group were reinforced with glass fibers. Unreinforced counterparts served as control. The samples were fixed on the abutments after thermocycling and then received a fatigue test. Subsequently, they were mechanically loaded until fracture, and the initial fracture load and fracture patterns were recorded. Statistical analysis, including two-sample t-test, one-way, two-way ANOVA, Tukey-Kramer HSD post hoc analysis and χ2 test were used to evaluate mechanical performance.

Results

The mean fracture load of FPDs with 14 mm pontic span length is significantly higher than the other lengths. The fracture load of each reinforced group is significantly higher than each counterpart control. There is no interaction between two variables, pontic span and fiber reinforcement. With fiber reinforcement, the fracture patterns were altered from catastrophic fracture to bent or partial fracture. But, the fracture patterns were not affected by pontic span.

Conclusion

The fracture load of acrylic FPDs decreases significantly when pontic span length is greater than 17 mm. Adding glass fibers into long-span provisional FPDs can significantly improve the fracture resistance and fracture patterns.

Effect of interface surface design on the fracture behavior of bilayered composites

This study aimed to evaluate the effect of different interface designs on the load‐bearing capacity of bilayered composite structures (BLS). Cylindrical specimens of BLS were prepared from base composite of 3.5 mm thickness and surface composite of 1.5 mm thickness (n = 80). Two different base composites – flowable bulk‐fill (FBF) [smart dentin replacement (SDR)] and short fiber‐reinforced (FRC) (everX Posterior) – were evaluated, and conventional composite (G‐ænial Posterior) was used as the surface layer. Four different interface designs were used: (i) pyramidal; (ii) mesh; (iii) linear grooves; and (iv) flat surface (control). Three‐dimensional printed molds were fabricated to standardize the interface design between the surface and the base composites. The specimens were then statically loaded with a steel ball until fracture using a universal testing machine. Fracture types were classified into catastrophic, complete, and partial bulk. anova revealed that both the material and the interface design had a statistically significant effect on the load‐bearing capacity. Flowable bulk‐fill showed lower mean load‐bearing capacity than FRC in all the interface designs tested, except for the flat surface design. Fracture analysis showed that FRC demonstrated up to 100% partial bulk fractures with the pyramid interface design, but no incidence of catastrophic bulk fracture. By contrast, FBF demonstrated up to 84.6% and 40% catastrophic bulk fractures with the flat interface design but no incidence of partial bulk fracture. Consequently, the interface designs studied enhanced the fracture behavior of BLS.

Influence of preheating and post-curing on a novel fiber-reinforced composite post material

The aim of this study was to investigate the influence of preheating and post-curing methods on diametral tensile strength (DTS), flexural strength (FS), knoop microhardness (KHN), and degree of conversion (DC) of an experimental fiber-reinforced composite (FRC). Specimens (30 wt% of 3-mm-short E-glass fiber, 22.5 wt% of methacrylated-based resin and 47.5 wt% of filler particles) were subjected to: P - photocuring at 1500 mW/cm2 for 40 s (control); P/M - photocuring and microwave post-curing (540W/5 minutes); P/A - photocuring and autoclave post-curing (120°C/15 minutes); PH-P - preheating (60°C) and photocuring; PH-P/M - preheating, photocuring and microwave post-curing; and PH-P/A - preheating, photocuring and autoclave post-curing. Specimens for DTS (Ø 3 x 6 mm) and FS (25 x 2 x 2 mm) were tested at Instron 5965. KHN employed a 50g load for 30s. DC was measured using FTIR spectroscopy. Statistical analysis employed: factorial analysis, normality test, one-way ANOVA and Tukey's HSD test, independent T-test and the Dunnett test. Interaction between factors was not significant (P>0.05). Preheating promoted significantly higher values of FS and KHN (p = 0.0001). Post-curing promoted significantly higher values for KHN (p = 0.0001). For DTS (p = 0.066) and DC (p= 0.724) no statistical difference was found between groups. SEM images showed that preheating promoted better interaction between glass fibers and resin matrix. Preheating increased FS, KHN and DTS, and post-curing increased KHN. DC was not affected by both methods. Preheating and post-curing methods can be used to improve some mechanical properties of FRCs' but degree of conversion remains unaffected.