Water sorption and solubility of bulk-fill composites polymerized with a third generation LED LCU

Comparative analysis of self-cure and dual cure-dental composites on their physico-mechanical behaviour

BACKGROUND

Clinical practitioners may have become familiar with the rapid transformation of dental composites. However, they may not scientifically understand the factors influencing the mechanical and physical properties. Scientific knowledge of filler-resin interaction can significantly improve clinical understanding of resin composites. Several independent studies have examined the mechanical and physico-mechanical properties of dental resin composites; however, no comprehensive study has examined the influence of fillers and resin materials on the physico-mechanical properties of both self-cure and dual-cure composites.

METHODS

This study performed investigations on the physico-mechanical behaviour of four commercially available dual-cure dental composites (Bioactive, Fill Up!, Surefil One, Cention N) and two commercially available self-cure dental composites (Stela Capsule and Stela Automix). Test specimens for flexural and compressive strength, microhardness, fracture toughness, and hydrolytic behaviour were prepared and tested as per respective standards. The data sets were statistically analysed using one-way ANOVA and Tukey's post-hoc comparison.

RESULTS

There was a substantial variation in flexural strength and modulus values in this study, ranging from 32.0 to 113.4 MPa and 2.36 to 12.07 GPa, respectively. Similarly, there were significant differences in compressive strength between the materials in this study, ranging from 119.3 to 223.5 MPa. The highest fracture toughness value was found to be 1.41 MPa.m0.5, while the lowest value was 0.43 MPa.m0.5. Variations in surface microhardness were significant (24.11-68.0 N/mm2), which correlated with the filler content. Water sorption and solubility demonstrated high variations among materials, with Surefil One exceeding ISO 4049 thresholds significantly.

CONCLUSIONS

A linear correlation can be established between surface microhardness (HV) and flexural and compressive moduli, as well as filler content (wt.%). However, both flexural and compressive strengths are impacted by the resin's constituent monomers and the resin-filler matrix's cross-linking capability. Additionally, factors such as filler size, shape, and the cross-linking ability of the resin-filler matrix play a crucial role in fracture toughness and the propagation of cracks within the restoration. Also, resin monomers and filler particle size affect the hydrolytic degradation characteristics of composites, which can also affect their mechanical properties. © 2023 Australian Dental Association.

The effect of varying monocalcium phosphate and polylysine levels on dental composite properties

OBJECTIVES

The aim was to quantify effects of polylysine (PLS, 2 or 5 wt%) and monocalcium phosphate (MCP, 4 or 8 wt%) on properties of dental composites.

METHODS

Light-activated, lower surface polymerisation kinetics versus sample depth (1-4 mm) of 4 formulations were quantified using ATR-FTIR. Water sorption and solubility (at 1 week) were assessed following ISO/4049. PLS release (over 1 month) and biaxial flexural strength (over 6 months) of fully-cured, water-immersed, 1 mm thick discs were determined. Surface mineral precipitation, following immersion in simulated body fluid (SBF), was assessed by SEM. Z250 was used as a conventional composite comparator.

RESULTS

With 40s light exposure, increasing depth (from 1 to 4 mm) led to enhanced delay before polymerisation (from 3 to 17s) and decreased final conversion (72-66%) irrespective of PLS and MCP level. Increasing PLS and MCP raised solubility (4-13 μg/mm3). Water sorption (between 32 and 55 μg/mm3) and final PLS release (8-13% of disc content) were raised primarily by increasing PLS. Higher PLS also reduced strength. Strength reached minimum values (69-94 MPa) at 3 months. Surface mineral deposition was enhanced by increased MCP. For Z250, polymerisation delays (3-6s) and final conversions (55-54%) at 1-4 mm depth, solubility (0 μg/mm3), water sorption (16 μg/mm3) and strength (180 MPa) were all significantly different.

CONCLUSION

Delay time increased whilst final conversion decreased with thicker samples. Higher PLS enhances its percentage release, but lower level is required to keep water sorption, solubility and mechanical properties within ISO 4049 recommendations. Doubling MCP raises solubility and enhances minerals reprecipitation with minimal mechanical property compromise.

Evaluation of the Color Stability, Water Sorption, and Solubility of Current Resin Composites

This study aims to assess the color stability, water sorption, and solubility of 11 resin composites as commercially available dental products. Twenty samples (10 mm in diameter and 2 mm in thickness) of each material were fabricated using a customized silicone mold, followed by immersion in each of curry, coffee, wine, and distilled water for 28 days (n = 5). Baseline shade and color changes (ΔE) were measured using a reflection spectrophotometer. The CIE L*, a*, b* system was used to evaluate the color changes. Five samples of each resin composite were applied to test water sorption and solubility according to ISO 4049:2009. As a result, the ∆E values were significantly influenced by each of the three factors (composition of material, solution, time) and the interactions between them (p < 0.001). Highest resistance to discoloration was achieved by Ceram.X One Universal (CXU), followed by Magnafill Putty (MP). Generally, microhybrid composites showed fewer color changes than nanohybrid composites and giomers. DX. Universal and Filtek Z350 XT showed the highest ΔE values in all colorants. All materials tested in this study fulfilled the criteria of ISO 4049:2009; CXU and MP had the lowest water sorption and solubility. The Pearson test showed statistically significant positive correlations between water sorption and ΔE and between solubility and ΔE.

Evaluation of color stability and microhardness of contemporary bulk-fill composite resins with different polymerization properties

OBJECTIVES

To determine the color stability and microhardness of three bulk-fill composites with different polymerization characteristics, after immersion in four different solutions.

MATERIALS AND METHODS

Color measurements of three bulk fill (Viscalor (VIS), Tetric PowerFill (TPF), Fill Up! (FUP)) and a microhyrid composite resin (G-aenial posterior [GCP]) were performed after polymerization. The specimens were immersed in coffee, cola, red wine and distilled water. Discolorations were recorded after 24 h (T1), 10 days (T2) and 30 days (T3) of immersion. ΔE (CIEDE2000) values were calculated. Vickers microhardness (VHN) was measured from top and bottom surfaces at T0 and T3. Data was analyzed with Two-way ANOVA, One-way ANOVA and Tukey post hoc tests.

RESULTS

The highest discoloration was seen in wine and the lowest in distilled water and cola. At T3, there was no difference in distilled water groups, while the statistically highest ΔE₀₀ were obtained in TPF and GCP in coffee, cola and wine. VIS groups had the highest VHN values at T0 and T3 in all solutions.

CONCLUSIONS

Samples immersed in coffee and wine showed discoloration beyond clinically acceptable limits. After 30 days, discoloration occurred in all materials immersed in all solutions. At T3, VIS microhardness generally decreased, while TPF did not.

CLINICAL SIGNIFICANCE

After 30 days, all bulk-fill composites immersed in distilled water, coffee and wine showed clinically unacceptable ΔE₀₀ .

Aging-Dependent Changes in Mechanical Properties of the New Generation of Bulk-Fill Composites

This study evaluated the behavior of a new generation of bulk-fill resin composites after prolonged exposure to an aqueous environment and accelerated aging in ethanol. Six bulk-fill materials were tested (Tetric PowerFill, Filtek One Bulk Fill Restorative, Tetric EvoCeram Bulk Fill, Fill-Up!, Tetric PowerFlow, SDR Plus Bulk Fill Flowable) and compared to two conventional reference materials (Tetric EvoCeram and Tetric EvoFlow). Flexural strength, modulus, and Weibull parameters were examined at three time points: 1 day, 30 days, and 30 days followed by ethanol immersion. Degree of conversion after 30 days, water sorption, and solubility up to 90 days were also investigated. Filtek One Bulk Fill had the highest flexural strength and modulus among the tested materials, followed by Tetric PowerFill and SDR plus. Flexural strength and modulus of high-viscosity bulk-fill materials showed higher stability after accelerated aging in ethanol compared to their low-viscosity counterparts and reference materials. After 30 days, the degree of conversion was above 80% for all tested materials. Dual-cure material Fill-Up! was the best-cured material. The water sorption was highest for Fill-Up!, Filtek One Bulk Fill Restorative, and Tetric EvoFlow, while solubility was highest for Tetric EvoCeram. After aging in water and ethanol, new generation high-viscosity bulk-fill materials showed better mechanical properties than low-viscosity bulk-fill and conventional composites under extended light curing conditions.

Effect of extended light activation and increment thickness on physical properties of conventional and bulk-filled resin-based composites

OBJECTIVES

To evaluate the biaxial flexural strength (BFS), flexural modulus (BFM), and Knoop microhardness (KHN) of incremental and bulk-filled resin-based composites (RBCs) using extended curing exposure times.

MATERIALS AND METHODS

Disc specimens (n = 8; 6-mm diameter) were fabricated using three stacked molds (0.5-mm thick for the top and bottom molds, and a 1-mm-thick center mold for the conventional and 3-mm thick for the bulk-fill RBCs). Conventional (Tetric EvoCeram/TCE and Filtek Z250/FIZ) and bulk-fill RBCs (Tetric EvoCeram Bulk Fill/TBF and Filtek One Bulk Fill Restorative/FOB) were evaluated. The stacked RBC-filled molds were light-cured for (1) the manufacturer-recommended exposure (MRE) duration; (2) 50%, and (3) 100% extension of the MRE. The BFS, BFM, and KHN of the top and bottom discs were measured. BFS and BFM were analyzed by three-way ANOVA (material*curing time*depth) and Tukey's post hoc (α = 0.05). KHN was analyzed by two-way ANOVA (curing time*depth) and Tukey's post hoc (α = 0.05).

RESULTS

Extending the exposure duration did not change the BFS and BFM on the top of the RBCs, but the BFS and KHN increased at the bottom of bulk-fill RBCs. For the conventional RBCs, TCE showed the highest increase on BFS at the bottom, going from 53.6 MPa at T1 to 69.9 at T3. Among the bulk-fill RBCs, FOB presented the highest increase on the bottom BFS (T1: 101.0 ± 19.9 MPa, T3: 147.6 ± 12.9 MPa). For all RBCs and exposure times, BFS and KHN were lower at the bottom. Only FIZ and FOB reached a bottom-to-top hardness ratio of 80%, at T3 and T2.

CONCLUSION

A significant increase on the BFS and KHN on the bottom of bulk-fill RBCs can be observed when the time of exposure to the curing light is double the MRE. However, extended exposure does not eliminate differences on the BFS and KHN between the shallow and deep regions of RBCs. TCE and TBF failed to reach an acceptable B/T hardness ratio at all evaluated exposure times.

CLINICAL RELEVANCE

Mechanical properties of RBCs can be affected by insufficient polymerization, specially at deeper regions of the increment. Therefore, clinicians should consider applying twice the MRE to curing-light to polymerize the maximal increment thickness of bulk-fill RBCs.

The effect of functionalized titanium dioxide nanotube reinforcement on the water sorption and water solubility properties of flowable bulk-fill composite resins

The aim of this study was to investigate the effects of titanium dioxide nanotube addition on the water sorption and water solubility values of different composite resins. Titanium dioxide nanotubes were synthesized from titanium dioxide powder in anatase form and in 13 nm diameter by hydrothermal process and then functionalized with methacrylic acid. Characterization of the nanotubes was performed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy. A flowable composite resin (Filtek Ultimate Flowable) and four flowable bulk-fill composite resins (Filtek Bulk Fill Flowable, SDR Bulk Fill Flowable, Venus Bulk Fill, X-tra Base) were tested. Two groups of each composite resin were prepared: groups of the resins without nanotubes; groups of the resins reinforced with 1.0 wt% functionalized titanium dioxide nanotube. Sorption and solubility in water were assessed according to ISO 4049 standards after 1, 7, 14, 21 days immersion periods. Data were analyzed using Mann-Whitney U and Kruskal-Wallis H tests (p  <  0.05). Long cylindrical tubular structures with a diameter of 41.09-72.49 nm were observed in electron microscopy analysis. The band at 1636 cm^- 1 showed the existence of the vinyl (C=C) bond of methacrylic acid coordinated to the nanotubes in Fourier transform infrared spectroscopy analysis. None of the materials tested in this study exceeded the maximum sorption and solubility values established by ISO. Regarding the water solubility, negative values were obtained. TiO₂ nanotube reinforcement decreased the water sorption and solubility values significantly at different evaluation periods in all composite resins except for Venus (p < 0.05).

Water Sorption and Solubility of Flowable Giomers

The objective of this study is the characterization of a novel experimental flowable giomer (G) regarding water sorption, water solubility, and the microstructural characteristics, in comparison to three commercial giomers: Beautifil flow Plus X F00 (B-F00), Beautifil flow F02 (B-F02) and Beautifil flow Plus X F03 (B-F03), Shofu, Kyoto, Japan. Methods: Water sorption/solubility was performed by weighing the specimens before and after water immersion for 1, 2, 3, 14, 21 and 30 days. Data analysis was carried out with the software Origin2019b Graphing & Analysis using the ANOVA test and the Tukey test for post hoc comparison of the groups of materials. The microstructural analyses were done with a scanning electron microscope (SEM) and an atomic force microscope (AFM). The results showed significant differences between the tested materials (p < 0.05). For sorption, the Tukey test indicated differences between all four sample groups, except between B-F02 and B-F03, which exhibited no differences in any of the investigation days. The Tukey test also showed significant differences regarding solubility between all sample groups in the 30-day interval. SEM images and roughness showed that after 30 days of immersion in water, the experimental giomer G had the roughest surface.

The Effects of Food-Simulating Liquids on Surface Roughness, Surface Hardness, and Solubility of Bulk-Fill Composites

Aim:

To investigate the surface roughness, surface hardness, and solubility of bulk-fill composites after exposure to food-simulating liquids (FSLs).

Materials and Methods:

A total of 200 disc-shaped samples (8 mm diameter × 4 mm depth) were prepared using four bulk-fill composites (SonicFillTM, Tetric® EvoCeram Bulk Fill, Beautifil-Bulk Restorative, FiltekTM Bulk Fill Posterior Restorative) and a microhybrid composite (FiltekTM Z250) ( n = 40). Following the measurement of initial weights of the samples ( m1), the surface roughness measurements were gauged using a contact-profilometer. The samples were stored in four different FSLs for 7 days, and then the second surface roughness values were recorded. The samples were stored in a desiccator to reach the constant mass and the values were recorded as m2, then the solubility levels were calculated. The Vickers microhardness values of the samples were determined. A total of 20 specimens were evaluated in terms of surface morphology with a scanning electron microscope (SEM). Data were statistically analyzed with the two-way ANOVA and Bonferroni tests ( P < .05).

Results:

Beautifil-Bulk Restorative was affected at most in terms of surface roughness after storage in FSLs and citric acid caused the highest values in this group ( P < .005). Beautifil-Bulk Restorative and Filtek Z250 showed the highest surface hardness values, while the Tetric EvoCeram group had the lowest. The highest solubility values were found in Beautifil-Bulk Restorative, and citric acid and ethanol yielded the highest solubility values for all of the composites.

Conclusion:

Beautifil-Bulk Restorative is the most affected group in all parameters evaluated and also affected overly by citric acid among the FSLs in consequence of its prereacted glass ionomer fillers.

Color stability of a bulk-fill composite resin light-cured at different distances

The aim of this in vitro study was to evaluate the color stability of a bulk-fill (Filtek One Bulk Fill, 3M ESPE) and a conventional (Filtek Z350 XT, 3M ESPE) composite resin light-cured at different distances, before and after being submitted to staining with a coffee solution. Sixty specimens of each composite resin were prepared and light-cured at distances of 0, 2 and 4 mm, using a LED light-curing unit (Valo, Ultradent). The specimens were separated (n = 10) for immersion in either distilled water or coffee solution (10 minutes a day for 8 days) to stimulate staining. Color evaluations were performed before and after immersion in the solutions, according to CIELab (△Eab), CIEDE2000 (△E00) and the Whiteness Index for Dentistry (△WID). Kruskal Wallis and Dunn tests, Mann-Whitney tests and Wilcoxon test were applied (α = 5 %). The a* value for conventional composite resin showed a significant increase after immersion in coffee and distilled water (p < 0.05). Both composite resins showed greater b* values when immersed in coffee than in distilled water, with no significant difference among the light-activation distances (p > 0.05). There was no significant difference for L* among the light-activation distances; both resins showed significant decrease in L* after immersion in coffee (p < 0.05). Color change (△Eab, △E00) and difference in whiteness (△WID) were higher for conventional resin when immersed in the coffee solution at all the light-activation distances. Conventional composite resin presented a higher staining value than bulk-fill composite resin, regardless of the light-activation distance.

A potential application of materials based on a polymer and CAD/CAM composite resins in prosthetic dentistry

PURPOSE

A bioactive high performance polymer (BioHPP) and computer-aided design/computer-aided manufacturing (CAD/CAM) composite resin materials are a relatively new class of dental biomaterials, that are biocompatible and have good aesthetic features. In this review paper, we will summarize literature and publication data on the characteristics of the mentioned materials, as well as their potential application in the dental prosthetics.

STUDY SELECTION

Available studies and literature reviews from PubMed, SCIndex, Scopus and Google Scholar corresponding to polyetheretherketone (PEEK), high-performance polymers, reinforced composite materials, composite materials, resins, glass-fiber reinforced materials, CAD/CAM materials, dental implants, removable and fixed dental were reviewed.

RESULTS

To avoid many disadvantages of metals and their alloys in dental practice, such as inadequate color, high density, thermal conductivity and possible allergic reactions, materials based on polymers (such as BioHPP), and CAD/CAM composite resins are being developed. These materials have significantly better aesthetics and physical-mechanical properties. They are biocompatible materials that are lightweight, resistant, durable, exhibit high bending and compression resistance.

CONCLUSIONS

The use of CAD/CAM composite resin materials and BioHPP in dentistry has begun recently, so the data about their potential clinical use are limited. Most of their features have been demonstrated through laboratory testing, while clinical studies are relatively scarce, so the need for further clinical trials is emphasized.

Dental Composition Modified with Aryloxyphosphazene Containing Carboxyl Groups

A modifier consisting of the mixture of cyclotriphosphazenes containing 4-allyl-2-methoxyphenoxy and β-carboxyethenylphenoxy moieties was developed for administration with acrylate dental restorative compositions. The synthesized compounds were characterized by ¹H and ¹³C NMR spectroscopy and MALDI-TOF mass spectrometry. The optimal conditions to combine the modifier with the starting dental mixture consisting of bis-GMA and TGM-3 were revealed by differential scanning calorimetry (DSC) method. Properties of the cured modified compositions were evaluated for the compliance with requirements of ISO 4049:2019. It was found that these compositions possess the increased adhesion to dental tissues and cure depth and the decreased water sorption and water solubility. The values of elastic modules, destructive compressive stress and microhardness were also increasing along with the increased content of the modifier in the composition.

Morphochemical characterization, microhardness, water sorption, and solubility of regular viscosity bulk fill and traditional composite resins

OBJECTIVE

To evaluate the morphology of filler particles, chemical composition, microhardness (MH), water sorption (WSp), and solubility (WSl) of a regular viscosity bulk fill and traditional composite resins.

METHODS

Eighty samples (Ø:5 mm; height: 4 mm) were prepared according to the factors "composite" (Aura/SDI, FiltekZ250 XT/3M, Aura Bulk Fill/SDI, and Filtek Bulk Fill/3M) and "filling technique" (incremental and bulk) (n = 10). Vickers MH was measured on the top and bottom surfaces of each samples, and then WSp and WSl were obtained by means of mass gain and loss. Morphology of filler particles and chemical characteristics of composites were evaluated by scanning electron microscopy (SEM) and energy dispersity spectroscopy (EDS) in additional samples (n = 1/group). Data were analyzed using two- and three-way ANOVA and Tukey's tests (p < .05).

RESULTS

No significant difference was found for WSp among the groups. Comparing composites in the incremental technique, Aura bulk fill composite showed lower WSI than the other materials and in the bulk fill technique, Filtek Bulk Fill showed the lowest value. Filtek Bulk Fill showed higher MH than the other composites on the bottom surface when samples were produced by bulk filling.

CONCLUSION

The composites presented good physical properties, but the bulk fill ones showed better results for the bottom microhardness and solubility, although chemical elements and morphology were similar in general.

Hydrolytic and Biological Degradation of Bulk-fill and Self-adhering Resin Composites

OBJECTIVES

This study aimed to evaluate the hydrolytic degradation (in vitro) and biodegradation (in situ) of different resin composites: bulk-fill (XTra Fill, XTF/VOCO; Tetric EvoCeram Bulk Fil, TBF/ Ivoclar Vivadent), self-adhering (Vertise Flow, VTF/ Kerr; Fusio Liquid Dentin, FUS/ Pentron Clinical), and a conventional resin composite (Filtek Z250, Z250/ 3M ESPE), which was used as a control.

METHODS AND MATERIALS

Seventy-five cylindrical specimens (7 × 1 mm) were desiccated and immersed into distilled water (DW), artificial saliva (AS), and 0.1 M lactic acid (LA) (n=5) for 180 days. Specimens were weighed after 180 days, after which they were desiccated again. The sorption (μg/mm³) and solubility (μg/mm³) were calculated based on ISO 4049. For the in situ phase, an intraoral palatal device containing five cylindrical specimens (5 × 1.5 mm) was used by 20 volunteers for seven days. Surface roughness was evaluated before and after this period to analyze the superficial biodegradation. Sorption and solubility data were submitted to Kruskal-Wallis and Mann-Whitney tests. The Wilcoxon signed-rank test was used to compare roughness at different observation times. The statistical significance for all tests was considered α=0.05.

RESULTS

For in vitro, self-adhering resin composites (VTF and FUS) showed, respectively, higher sorption values independent of the solution (62.55 and 50.81 μg/mm³ in DW, 67.26 and 50.46 μg/mm³ in AS, and 64.98 and 59.86 μg/mm³ in LA). Self-adhering VTF also had a greater solubility value in DW (22.18 μg/mm³) and FUS in LA (65.87 μg/mm³). In AS, the bulk-fill resin composite XTF showed higher solubility (22.13 μg/mm³). All resins were biodegraded, but the XTF specimens were more resistant (p=0.278) to chemical attack.

CONCLUSIONS

The self-adhering resin composites showed the highest hydrolytic degradation, and the bulk-fill resin composites exhibited comparable or superior results to the conventional resin composites. Not all resin composites underwent biodegradation in the in situ environment. The storage environment influenced the final characteristics of each material tested.