Mechanical Properties of Nanohybrid Resin Composites Containing Various Mass Fractions of Modified Zirconia Particles

Study on the mechanical and aging properties of an antibacterial composite resin loaded with fluoride-doped nano-zirconia fillers

Preventing the occurrence of secondary caries serves as one of the significant issues in dental clinic, thus make it indispensable to improving the properties of conventional composite resin (CR) by developing a novel CR. In present study, two groups of experimental CRs loaded with different contents of fluoride-doped nano-zirconia fillers (25 wt% and 50 wt%) were fabricated. The surface topography, mechanical performance, fluoride release, antibacterial effect, aging property and cytotoxicity of the experimental CRs were evaluated subsequently. A uniform distribution of the F-zirconia fillers over the whole surface of resin matrix could be observed. The experimental CRs showed continuous fluoride release within 28 days, which was positively correlated with the content of F-zirconia fillers. Moreover, the amount of fluoride release increased in the acidic buffer. Addition of F-zirconia fillers could improve the color stability, wear resistance and microhardness of the experimental CRs, without reducing the flexure strength. Furtherly, the fluoride ions released continuously from the experimental CRs resulted in effective contact and antibacterial properties, while they showed no cytotoxicity. As a consequence, considerations can be made to employ this new kind of composite resin loaded with fluoride-doped nano-zirconia fillers to meet clinical requirements when the antimicrobial benefits are desired.

Influence of Diabetes Mellitus and Universal Adhesive Application Mode on the Bond Strength of Composite Resin to Dentine

Background

The aim of the current study was to evaluate the influence of diabetes mellitus and the mode of applying a universal adhesive on the shear bond strength of composite resin to dentin.

Material and Methods

Forty teeth were extracted from diabetic individuals who had been living with diabetes for a period of 5 to 15 years. These forty teeth were divided into two groups: twenty molars from patients with type 1 diabetes and twenty molars from patients with type 2 diabetes. The remaining twenty sound human molars were collected from non-diabetic patients. The collected teeth were assigned into 3 groups, and each group was further divided into 2 subgroups. Group A (n = 20): non-diabetic (ND) where sub group IA: Universal adhesive applied in the total-etch mode (n = 10) and sub group IIA: Universal adhesive applied in the self-etch mode (n = 10). Group B (n = 20): diabetic type 1 (D1) where sub group IB: Universal adhesive applied in the total-etch mode (n = 10) and sub group IIB: Universal adhesive applied in the self-etch mode (n = 10). Group C (n = 20): diabetic type 2 (D2). Where Sub group IC: Universal adhesive applied in the total-etch mode (n = 10) and sub group IIC: Universal adhesive applied in the self-etch mode (n = 10). A Teflon mold measuring 3mm in diameter was attached to the dentin surface, used to build Filtek Z550 to a height of 3mm. The specimens were fixed to the universal testing to measure shear bond strength.

Results

There was a statistically significant difference of Mean ±SD of shear bond strength among the three tested groups. In group A, the Mean ±SD were (21.710 ± 0.638), it was decreased in group B to (14.626 ± 0.726) and group C to (17.740 ± 0.668). Subgroup I had lower shear bond strength values than subgroup II in all tested groups. The difference between each subgroup in groups A, B, and C was significant.

Conclusions

1. Diabetes mellitus has an adverse effect on the shear bond strength of composite to dentine. 2. Type 1 diabetes mellitus significantly reduces the shear bond strength of composite resin to dentin. 3. Shear bond strength of the universal adhesive was higher when applied to dentin using the self-etch mode, as compared to the total etch mode, in all groups, regardless of whether the participants had diabetes or not. Key words:Diabetes Mellitus, Universal Adhesive, Application Mode, Shear bond Strength, Dentine, Composite.

Color Stability of Bioactive Restorative Material vs Nanohybrid Resin Composite: An In Vitro Study

AIM

This study aimed to assess the color stability of bioactive restorative materials vs nanohybrid resin composites after 3 months of immersion in three frequently consumed beverages.

MATERIALS AND METHODS

Thirty disk-shaped specimens of Giomer dental restorative material (Shofu, Japan) and nanohybrid resin composite (Tokuyama, Japan) were performed using a Teflon mold. Super-Snap system (Shofu, Japan) was utilized to finish and polish the specimens to be preserved for 24 hours in distilled water at 37°C. The samples had been divided into three subgroups (Coffee, tea, Pepsi) (n = 5). The initially displayed color measurements of the samples were performed using a spectrophotometer (VITA Easyshade® V). After 7 days, 30 days, and 90 days, color measurements were repeated, and the E of each sample was estimated. E of each sample was calculated.

RESULTS

The Giomer group showed statistically significant higher E values than the nanohybrid resin composite where the p-value was ≤0.0001. Tea subgroup showed the highest statistically significant E values in both groups where the p-value was ≤ 0.0001. The highest statistically significant color change was recorded at 3 months.

CONCLUSION

The color of bioactive restorative material is less stable if compared with nanohybrid resin composite.

CLINICAL SIGNIFICANCE

As tea and coffee are popular beverages, particularly in Middle Eastern nations, dentists must advise patients about the color change of resin restorations. Patients are advised to brush their teeth immediately after consuming these beverages. How to cite this article: Saber EH, Abielhassan MH, Abed YA, et al. Color Stability of Bioactive Restorative Material vs Nanohybrid Resin Composite: An In Vitro Study. J Contemp Dent Pract 2024;25(3):221-225.

Optical behavior and marginal discoloration of a single shade resin composite with a chameleon effect: a randomized controlled clinical trial

OBJECTIVE/AIM

Evaluating the optical behavior and marginal discoloration of a Single-shade universal resin composite over 12 months. To achieve this, a split-mouth with a double-blinded randomized strategy was employed.

MATERIALS AND METHODS

Twenty adult patients, each presenting with at least two caries lesions in their posterior teeth, were selected and randomly subdivided into two identical groups: Group I received Single-shade universal resin composite (Omnichroma), and Group II received multi-shade nanohybrid resin composite (Tetric®N-Ceram). Color measurements and marginal discoloration were assessed visually by three blinded operators at baseline followed after 1,3,6,9, and 12‑month periods utilizing the Modified United States Public Health Services (USPHS) criteria. Statistical analysis was adopted utilizing the Wilcoxon test with a 0.05 significance level.

RESULTS

The two groups revealed non-statistically significant differences up to 6 months regarding color match and color stability. After 9 and 12 months, the multi-shade group demonstrated a statistically significant higher prevalence of color match (Alpha) scores than the single-shade universal group. Regarding marginal discoloration, all restorations in the two groups had no discoloration (Alpha scores).

DISCUSSION/CONCLUSION

Since the percentage of Alpha and Bravo scores was considered clinical success, both the single-shade universal and the multi-shade nanohybrid resin composites demonstrated satisfactory optical performance and marginal discoloration as posterior restorations after a 12-month follow-up period.

Physicochemical and mechanical properties of preheated composite resins for luting ceramic laminates

This study analyzed and compared the physicochemical and mechanical properties of preheated resin composite with light-cured resin cement for luting indirect restorations. 210 specimens of resin cement/resin composite were prepared according to preheating treatment heated (Htd) or not (NHtd). Light-cured resin cement (Variolink Veneer, Ivoclar), and resin composite (Microhybrid-Z100, 3 M; Nanohybrid-Empress direct, Ivoclar; and Bulk fill-Filtek One, 3 M) were used (n = 10). Resin cement specimens were not preheated. The response variables were (n = 10): film thickness, microhardness, liquid sorption and solubility. Data were analyzed by 2-way ANOVA and Tukey HSD post-test (α = 0.05). Bulk fill NHtd resin had the highest film thickness values (p < 0.001). Microhybrid and nanohybrid Htd resins had the smallest thicknesses and did not differ from the cement (p > 0.05). The highest microhardness values were found for Bulk fill NHtd and Bulk fill Htd resins. The nanohybrid and microhybrid Htd resins showed the lowest microhardness values, with no difference in cement (p > 0.05). For liquid sorption, there was no significant difference between the groups (p = 0.1941). The microhybrid Htd resin showed higher solubility values than the other materials (p = 0.0023), but it did not differ statistically from resin cement (p > 0.05). Preheating composite resins reduced the film thickness. After heating, nanohybrid and Bulk fill resins retained stable microhardness, sorption, and solubility values.

Evaluation of physical/mechanical properties of an experimental dental composite modified with a zirconium-based metal-organic framework (MOF) as an innovative dental filler

OBJECTIVES

This study aimed to modify an experimental dental composite using a synthesized nano-structured methacrylated zirconium-based MOF to enhance physical/mechanical properties.

METHODS

The previously known Uio-66-NH2 MOF was first synthesized and post-modified with Glycidyl Methacrylate (GMA). Fourier Transform Infrared (FTIR) Spectroscopy and CHNS analysis confirmed the post-modification reaction. The prepared filler was investigated by XRD, BET, SEM-EDS, and TEM. The experimental composite was prepared by mixing 60% wt. of resin matrix with 40% wt. of fillers, including silanized silica (SS) or Uio-66-NH-Me (UM). The experimental composites' depth of cure (DPC) was investigated in five groups (G1 =40% SS, G2 =30%SS+10%UM, G3 =20%SS+20%UM, G4 =10%SS+30%UM, G5 =40%UM). Then flexural strength(FS), Elastic Modulus(EM), solubility(S), water sorption(WS), degree of conversion(DC), polymerization shrinkage(PS), and polymerization stress(PSR) of the groups with DPC of more than 1 mm were investigated. Finally, the cytotoxicity of composites was studied.

RESULTS

The groups with more than 20% wt. UM, filler (G4, G5) had lesser than 1 mm DPC. Therefore, we investigated three groups' physical and mechanical properties with lower than 20% UM filler (G1-G3). Within these groups, G3 has a higher FS, EM (P < 0.05), and lower WS and S (P < 0.05). DC dropped in G2 and G3 compared to G1 (p < 0.05), but there was no significant difference between G2 and G3 (P = 0.594).

SIGNIFICANCE

This new filler is an innovative coupling-agent free filler and can be part of dental filler technology itself. It can also introduce a new group of dental fillers based on MOFs, but it still needs a complete investigation to be widely used.

Tribological behavior and wear mechanisms of dental resin composites with different polymeric matrices

The aim of this study was to investigate the effect of different polymeric matrices and their crosslink density on the mechanical and tribological properties of three commercially available dental resin composites, including Filtek Z250XT, Charisma Classic, and Venus Diamond One. The mechanical properties of the composites were investigated by instrumented indentation. The results showed that the polymeric matrix composition has a significant effect on the hardness and elastic modulus of the resins. Wear resistance was investigated by reciprocating ball-on-plane tests in artificial saliva. Results show that the TCD-based resin composite has higher crosslinking density resulting in a more wear-resistant material. There was also a strong correlation between wear resistance and the mechanical properties of the resin composites when comparing similar fillers. These findings suggest that the wear resistance of resin composites can be improved by increasing their crosslinking density and enhancing their mechanical properties. The study provides insights into the design and development of more wear-resistant resin composites for dental applications.

Lignin-derived new hydrogen donors for photoinitiating systems in dental materials

OBJECTIVES

The aim of this study is to develop amine free photo-initiating system (PIs) for the photopolymerization of dental methacrylate resins, using seven new hydrogen donors HDA-HDG derived from β-O-4 lignin model.

METHODS

Seven experimental CQ/HD PIs were formulated with Bis-GMA/TEGDMA (70 w%/30 w%). CQ/EDB system was chosen as the comparison group. FTIR-ATR was used to monitor the polymerization kinetics and double bond conversion. Bleaching property and color stability were evaluated using a spectrophotometer. Molecular orbitals calculations were used to demonstrate C-H bond dissociation energies of the novel HDs. Depth of cure of the HD based systems were compared to the EDB based one. Cytotoxicity was also studied by CCK8 assay using tissue of mouse fibroblasts (L929 cells).

RESULTS

Compared to CQ/EDB system, the new CQ/HD systems show comparable or better photopolymerization performances (1 mm-thick samples). Comparable or even better bleaching properties were also obtained with the new amine-free systems. Comparing to EDB, all HDs exhibited significantly lower C-H bond dissociation energies by molecular orbitals calculations. Groups with new HD showed higher depth of cure. OD and RGR values were similar to that of the CQ/EDB group, ensuring the feasibility of the new HDs in dental materials.

CLINICAL SIGNIFICANCE

The new CQ/HD PI systems could be potentially useful in dental materials, presenting improvements in restorations' esthetic and biocompatibility.

Effect of Different Mouthwashes on the Surface Microhardness and Color Stability of Dental Nanohybrid Resin Composite

BACKGROUND

Surface microhardness and color stability of dental restorative material should be sustained throughout its functional lifetime to maintain the esthetic quality of the restoration. However, the frequent application of mouthwash may affect their surface microhardness and color stability. The aim of this study was to evaluate the effects of different types of mouthwashes with different contents on surface microhardness and color stability of dental nanohybrid resin-based composite.

METHODS

Disc specimens of nanohybrid resin composite (Luna Nano-Hybrid Composite) were prepared according to manufacturing instructions; specimens were incubated for 24 h in three types of mouthwash (Chlorohexidine, Listerine Green Tea, and Colgate Optic White Whitening Mouthwash). Artificial saliva was used as a control group. Surface microhardness was evaluated using Vickers microhardness device. Color stability after and before immersion in the different mouthwashes was evaluated using extra-oral spectrophotometer; the values of color change (ΔE₀₀) were subsequently calculated. Data were analyzed using one-way ANOVA and post hoc test (p ≤ 0.05).

RESULTS

There was no significant difference between microhardness of resin composite immersed in artificial saliva, CHX, and Green Tea mouthwashes (78.5, 78.4, and 73.5, respectively) (p ≥ 0.1), while the bleaching mouthwash led to the lowest microhardness of resin composite, with significant difference compared to the three previous immersion media (p = 0.002). Moreover, there were significant differences in the color changes (ΔE₀₀) of resin composite exposed to the various immersion media (p = 0.0001).

CONCLUSIONS

The bleaching mouthwash led to a significant reduction in nanohybrid resin composite's microhardness compared to the chlorohexidine and Green Tea containing mouthwashes. The resin composite's color change was accepted in bleaching mouthwash but unaccepted in chlorohexidine and Green Tea containing mouthwashes.

Application Effect of New Material after Surface Modification of Zirconia Ceramics and Analysis of Patient Evaluation

Objective

To explore the application effect of new material after surface modification of zirconia ceramics and patient evaluation.

Methods

A total of 60 patients with tooth defect treated in our hospital from April 2020 to April 2021 were selected as the study subjects and randomly divided into the control group and experimental group, with 30 cases each. The patients in the control group were treated with glass-ceramics, and those in the experimental group received LiSi surface treatment, so as to compare the application effect and patients' evaluation between the two groups.

Results

Between the two groups, no obvious differences in surface loss, adhesive strength, and transmittance at 3 months, 6 months, and 1 year were not observed (P > 0.05); and after intervention, the score on dental aesthetics, hardness value, and occlusal force were obviously higher in the experimental group than in the control group (P < 0.001).

Conclusion

The new material enables forming an acid etchable coating on the zirconia surface, increases the adhesive strength, and achieves an aesthetic degree that is welcomed by the patients; meanwhile, after grinding, the edge is defect free and the tightness is higher. Further research will help to establish a better solution for patients.

The influence of inorganic fillers on the light transmission through resin-matrix composites during the light-curing procedure: an integrative review

PURPOSE

The objective of this study was to perform an integrative review on the effect the inorganic fillers on the light transmission through the resin-matrix composites during the light-curing procedure.

METHOD

A bibliographic review was performed on PubMed using the following search terms: "fillers" OR "particle" AND "light curing" OR "polymerization" AND "light transmission" OR "light absorption" OR "light irradiance" OR "light attenuation" OR "light diffusion" AND "resin composite." The search involved articles published in English language in the last 10 years.

RESULTS

Selected studies reported a decrease in biaxial strength and hardness in traditional resin-matrix composites in function of the depth of polymerization. However, there were no significant differences in biaxial strength and hardness recorded along the polymerization depth of Bulk-Fill™ composites. Strength and hardness were enhanced by increasing the size and content of inorganic fillers although some studies revealed a progressive decrease in the degree of conversion on increasing silica particle size. The translucency of glass-ceramic spherical fillers promoted light diffusion mainly in critical situations such as in the case of deep proximal regions of resin-matrix composites.

CONCLUSIONS

The amount of light transmitted through the resin-matrix composites is influenced by the size, content, microstructure, and shape of the inorganic filler particles. The decrease of the degree of conversion affects negatively the physical and mechanical properties of the resin-matrix composites.

CLINICAL RELEVANCE

The type and content of inorganic fillers in the chemical composition of resin-matrix composites do affect their polymerization. As a consequence, the clinical performance of resin-matrix composites can be compromised leading to variable physical properties and degradation. The polymerization mode of resin-matrix composites can be improved according to the type of inorganic fillers in their chemical composition.

Baicalin-liposomes loaded polyvinyl alcohol-chitosan electrospinning nanofibrous films: Characterization, antibacterial properties and preservation effects on mushrooms

To investigate antibacterial properties and application in food preservation of nanofibrous films (NFs), baicalin-liposomes (BCL-LPs) were loaded into polyvinyl alcohol-chitosan (PVA-CS) substrates to form NFs using electrospinning technology. The microstructure and phase identification of the NFs were characterized. The antibacterial properties and cytotoxicity of NFs were determined. The preservation of the NFs to mushrooms was evaluated. The results showed that smooth and uniform NFs were formed through molecular interaction between BCL-LPs and PVA-CS matrix. The NFs exhibited good antibacterial effects on Escherichia coli and Staphylococcus aureus due to the bacterial destruction resulting from the BCL delivery to bacterial cells by liposomes. In addition, the NFs were compatible with L929 fibroblasts. The BCL-LPs/PVA-CS NFs inhibited weight loss, browning, rancidity and bacterial growth as well as maintained the nutrients of mushrooms. The results show BCL-LPs/PVA-CS NFs possessed effective antibacterial properties, non-cytotoxicity and preservation performance, indicating the potential utilization as food-active packing.

Sol-Gel Synthesis and Characterization of YSZ Nanofillers for Dental Cements at Different Temperatures

BACKGROUND

Yttria-stabilized zirconia nanoparticles can be applied as fillers to improve the mechanical and antibacterial properties of luting cement. The aim of this study was to synthesize yttria-stabilized zirconia nanoparticles by the sol-gel method and to investigate their composition, structure, morphology and biological properties.

METHODS

Nanopowders of ZrO₂ 7 wt% Y₂O₃ (nY-ZrO) were synthesized by the sol-gel method and were sintered at three different temperatures: 800, 1000 and 1200 °C, and their composition, size and morphology were investigated. The biocompatibility was investigated with human gingival fibroblasts (hGFs), while reactive oxygen species (ROS) production was evaluated through fluorescence analysis.

RESULTS

All synthesized materials were composed of tetragonal zirconia, while nanopowders sintered at 800 °C and 1000 °C additionally contained 5 and 20 wt% of the cubic phase. By increasing the calcination temperature, the crystalline size of the nanoparticles increased from 12.1 nm for nY-ZrO800 to 47.2 nm for nY-ZrO1200. Nano-sized particles with good dispersion and low agglomeration were received. Cell culture studies with human gingival fibroblasts verified the nanopowders' biocompatibility and their ROS scavenging activity.

CONCLUSIONS

the obtained sol-gel derived nanopowders showed suitable properties to be potentially used as nanofillers for dental luting cement.