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Poly(methyl methacrylate) (PMMA)/nanobarium titanate (NBT) composite has potential application in denture base materials. The denture base materials should be stable in the wet environment and exhibit good mechanical properties. This study aimed to evaluate the effectiveness of titanate coupling agent (TCA) on NBT behavior after soaking in the simulated body fluid (SBF) and to determine the effect of SBF exposure on fracture toughness of the PMMA nanocomposites. Silanated (Si-NBT), titanated (Ti-NBT), and pure NBT (Un-NBT) at 5% concentration (by mass) were incorporated in the PMMA matrix. NBT was sonicated in MMA prior to mixing with PMMA. SBF absorption, solubility, and leaching were measured, and fracture toughness of the PMMA nanocomposites was evaluated after soaking. The results showed that Titanated samples displayed lower SBF absorption capability and solubility values than the silanated ones. Moreover, the leachability of filler elements (Ba and Ti) was substantially reduced by titanation (54% and 61%, respectively), whereas the Si-NBT/PMMA revealed values of 12.3% and 7% respectively. Significant differences in fracture toughness were observed among the tested samples after 6 weeks of aging in SBF (p < 0.05). Although no notable changes in the KIC of pure PMMA and Un-NBT/PMMA samples were detected, KIC was improved by 20% after titanation. In addition, the fracture toughness of the titanated samples was higher than that of the silanated ones by 26%. In conclusion, TCA exhibited better stability in moisture than silane. Degradation resistance to moisture obtained with titanated NBT could lead to the promotion of clinical longevity of the composites. [ABSTRACT FROM AUTHOR]

The aim of the study was to determine the knowledge, attitude, and practice regarding the use of composites for orthodontic purposes among dental students. The questionnaire was designed to evaluate knowledge, attitude, and awareness. Google Forms was used for the distribution of questions. This is a questionnaire survey based on knowledge, attitude, and awareness regarding the use of composites for orthodontic purposes among dental students; 86% of them had awareness regarding the use of composites for orthodontic purposes, wherein the remaining 14% were not aware. Considering the limitations of the study groups, we can conclude that the knowledge, attitude, and awareness regarding the use of composites for orthodontic purposes among dental students were good. However, there is still a lack of knowledge in few perspectives which can be overcome with continuous dental education programs and lectures [ABSTRACT FROM AUTHOR]

Predicting how tooth and dental material bonds perform in the mouth requires a deep understanding of degrading factors. Yet, this understanding is incomplete, leading to significant uncertainties in designing and evaluating new dental adhesives. The durability of dental bonding interfaces in the oral microenvironment is compromised by bacterial acids, salivary enzymes, and masticatory fatigue. These factors degrade the bond between dental resins and tooth surfaces, making the strength of these bonds difficult to predict. Traditionally studied separately, a combined kinetic analysis of these interactions could enhance our understanding and improvement of dental adhesive durability. To address this issue, we developed and validated an original model to evaluate the bond strength of dental restorations using realistic environments that consider the different mechanical, chemical, and biological degradative challenges working simultaneously: bacteria, salivary esterases, and cyclic loading. We herein describe a comprehensive investigation on dissociating the factors that degrade the bond strength of dental restorations. Our results showed that cariogenic bacteria are the number one factor contributing to the degradation of the bonded interface, followed by cyclic loading and salivary esterases. When tested in combinatorial mode, negative and positive synergies towards the degradation of the interface were observed. Masticatory loads (i.e., cycling loading) enhanced the lactic acid bacterial production and the area occupied by the biofilm at the bonding interface, resulting in more damage at the interface and a reduction of 73 % in bond strength compared to no-degraded samples. Salivary enzymes also produced bond degradation caused by changes in the chemical composition of the resin/adhesive. However, the degradation rates are slowed compared to the bacteria and cyclic loading. These results demonstrate that our synergetic model could guide the design of new dental adhesives for biological applications without laborious trial-and-error experimentation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Dental composites, through their structural diversity, represent the biomaterials frequently used in dental reconstructive therapy. The aim of our study was to observe the influence of different beverage environment conditions on seven types of obturation dental materials with different compositions. Our research focused on the surface modification analysis of the materials after the immersion in the different beverages; in this regard, we used the EDAX technique correlated with the energy-dispersive X-ray fluorescence (XRF). The pH of the drinks and that of the simulated saliva solution were determined by the titrimetric method, a sodium hydroxide solution 0.1 mol/dm3 was prepared and used for the titration. An amount of 5 mL of each analyzed solution was added to 15 mL of distilled water to obtain a dilution, to which 3 drops of phenolphthalein (as a color indicator—Phenolphthalein, 3,3-Bis(4-hydroxyphenyl)-1(3H)-isobenzofuranone, C20H14O4 Mw: 318.32, purchased from Merck) were added for each analysis. For each solution, the experiment was repeated three times in order to obtain accurate results. The results of our study materialized into a real plea for modifying the patients’ behavior in terms of diet and preferences for acidic drinks, so that their quality-of-life valence can be improved by keeping the composite materials in a long-term unalterable state on the one hand; on the other hand, systemic damage can be prevented as well.

This study aimed to determine the effect of the testing method configuration on the bi-axial flexural strength (BFS) of three resin-based dental composites (RDCs). A total of 180 disc-shaped samples (12 mm diameter x 1 mm thickness) for each RDC were fabricated using split back nylon mould. The BFS was determined for specimens made in three commercial RDCs; microhybrid (MH), nanofilled paste (NFP) and nanofilled flowable (NFF) using the ring-on-ring (RoR; n = 90 for each RDC specimens) and ball-on-ring (BoR; n = 90 for each RDC specimens) configurations at a cross-head speed of 1 mm/min. RDC specimens of MH and NFP tested in the BoR configuration showed higher mean BFS values compared to those tested in the RoR configuration. (p < 0.001). The effect of test configuration on BFS values was insignificant for the specimens belonging to the NFF group (p = 0.207). Moreover, the Weibull modulus of NFF in the RoR configuration was statistically lower compared to those for NFF in the BoR configuration as the 95% confidence interval of Weibull modulus did not overlap. The specimen support and testing configuration significantly impacted the BFS value of the RDCs. The Weibull statistics appeared to be inappropriate for all kinds of RDCs. [ABSTRACT FROM AUTHOR]

Resin composite mimics tooth tissues both in structure and properties, and thus, they can withstand high biting force and the harsh environmental conditions of the mouth. Various inorganic nano- and micro-fillers are commonly used to enhance these composites’ properties. In this study, we adopted a novel approach by using pre-polymerized bisphenol A-glycidyl methacrylate (BisGMA) ground particles (XL-BisGMA) as fillers in a BisGMA/triethylene glycol dimethacrylate (TEGDMA) resin system in combination with SiO2 nanoparticles. The BisGMA/TEGDMA/SiO2 mixture was filled with various concentrations of XL-BisGMA (0, 2.5, 5, and 10 wt.%). The XL-BisGMA added composites were evaluated for viscosity, degree of conversion (DC), microhardness, and thermal properties. The results demonstrated that the addition of a lower concentration of XL-BisGMA particles (2.5 wt.%) significantly reduced (p ≤ 0.05) the complex viscosity from 374.6 (Pa·s) to 170.84. (Pa·s). Similarly, DC was also increased significantly (p ≤ 0.05) by the addition of 2.5 wt.% XL-BisGMA, with the pristine composite showing a DC of (62.19 ± 3.2%) increased to (69.10 ± 3.4%). Moreover, the decomposition temperature has been increased from 410 °C for the pristine composite (BT-SB0) to 450 °C for the composite with 10 wt.% of XL-BisGMA (BT-SB10). The microhardness has also been significantly reduced (p ≤ 0.05) from 47.44 HV for the pristine composite (BT-SB0) to 29.91 HV for the composite with 2.5 wt.% of XL-BisGMA (BT-SB2.5). These results suggest that a XL-BisGMA could be used to a certain percentage as a promising filler in combination with inorganic fillers to enhance the DC and flow properties of the corresponding resin-based dental composites.

The dental curing unit (DCU) has been reported to emit inhomogeneous light. However, there are no studies on which elements could affect the inhomogeneity of DCUs. This study aimed to analyze the effect of attenuating factors such as the aperture of the lens or neutral density (ND) filters on the DCU's beam profile and evaluate the effect of DCU's inhomogeneous beam profile on the microhardness distribution on composite resin specimens with different thicknesses. Radiant emittance and spectrum of eight DCUs were investigated with and without ND filters using different optical density (OD) values. Beam profiles of eight DCUs were photographed while increasing the OD values of the ND filter. The change in the beam profile while changing the f-number of the aperture and the OD value of the ND filters were recorded. The Vickers microhardness of Filtek Z350XT and SDR cured by Bluephase Style 20i with 1, 2, 3, and 4 mm specimens of nine points on each surface was measured. Irradiance and spectrum of DCUs uniformly decreased after attenuation by the ND filters. The beam profile of the DCUs blurred when the f-number of the aperture was higher. The microhardness of Filtek Z350XT showed differences between the central and peripheral areas, and between the points under violet LED and the center on the bottom surface of the 4 mm specimen. The microhardness of the SDR did not show any differences. The inhomogeneity of the beam profile can be affected by attenuation conditions. DCU's inhomogeneous beam profile may have different effects on the composites depending on the thicknesses and types of composite resin used. • The inhomogeneity of the beam profile can be affected by attenuation conditions. • The attenuation effect on the flatness factor varied depending on the dental curing units. • Effect of inhomogeneous beam on microhardness was evident on heavily attenuated area. [ABSTRACT FROM AUTHOR]

In this present study, the preference selection index method (PSI) was applied to identify the best formulation among ceramic fillers such as glass ionomer cement (GIC), nanosilica and nanoalumina nanofiller in the dental composites. The comparative assessment of the effect of nanofillers (nanoalumina and nanosilica fillers) and glass ionomer cement has been evaluated. Dental composites with 0, 10, and 20 wt% of nanoalumina, nanosilica and glass ionomer cement were fabricated. These composites were analyzed for physico‐mechanical and wear properties. The PSI multi‐criteria decision making technique was used to rank the composites with various filler content. The performance defining attributes for the comparative assessment were set as void content, hardness, compressive strength, flexural strength, diametral tensile strength, and wear properties against load and speed. The PSI of dental composite reinforced with 20 wt% nanosilica (DCSi‐20) was maximum (0.896) followed by dental composite reinforced with 20 wt% glass ionomer (DCGi‐20) (0.889) and hence DCSi‐20 demonstrated as most preferred dental composite material followed by DCGi‐20. DC‐0 showed the least preference dental composite materials on the basis of desirable physical, mechanical, and wear properties. Finally, it can be concluded that despite of more void content and low flexural strength, overall performance of glass ionomer is comparable with nanosilica and more significant with respect to nanoalumina. [ABSTRACT FROM AUTHOR]

The main aim of the current work was to develop the novel self-healing dental composites contained poly(methyl methacrylate) (PMMA) microcapsules. The effects of PMMA microcapsule content in self-healing performance and mechanical properties of dental composites including flexural strength, flexural modulus, and fracture toughness were discussed. The antibacterial activity and non-toxicity properties of optimum self-healing dental composites were also investigated. Novel acrylic microcapsules were prepared using triethylene glycol dimethacrylate (TEGDMA) as healing agent and PMMA as microcapsule shell via solvent evaporation method. The silica nanoparticles with the mean size of 15–20 nm were treated by 3-methacryloxypropyltrimethoxysilane (MPS) to enhance their adhesion and dispersion within the acrylic matrix of composite. Acrylic microcapsules with mass fractions of 0%, 5%, 10%, and 15% were added into a mixture of acrylic resins and MPS-grafted SiO 2 nanoparticles. The strength and elastic modulus of dental composites were measured by the flexural test. The single edge V-notched beam (SEVNB) method was applied to investigate fracture toughness (K IC) and healing efficiency. The results were then statistically analyzed using one-way analysis of variance (ANOVA) at the confidence level of 0.95. Acrylic microcapsules were synthesized with the mean size around 30 µm and the core content of about 15 wt%. The grafting percentage of MPS surface modifier onto SiO 2 nanoparticles was measured 3.2%. The incorporation of PMMA microcapsules into the dental composites had no significant effect on flexural properties. The self-healing dental composites also indicated the high efficient healing performance in the range of 78–121%. The self-healing dental composites also exhibited impressive antibacterial activity against Streptococcus mutans (S. mutans). The MTT assay also revealed that the incorporation of acrylic microcapsules in dental composites has no cytotoxicity effects. In the current study, for the first time, the self-healing dental nanocomposites contained acrylic microcapsules were prepared with excellent healing performance and antibacterial properties. [Display omitted] • Highly responsive self-healing dental composites were prepared via incorporation of the novel acrylic microcapsules. • Incorporation of acrylic microcapsules into the dental composites had no adverse effect on flexural properties. • Self-healing dental composites indicated impressive antibacterial activity against Streptococcus mutans (S. mutans). [ABSTRACT FROM AUTHOR]

Commercial bisphenol A‐glycol methacrylate (BisGMA)/triethyleneglycol‐dimethacrylate (TEGDMA) have been widely used as dental restorative material; however, the poor mechanical and anti‐wear properties greatly limited their applied range. In this study, iron‐containing hydroxyapatite (FeHA) nanoparticles that mimic the chemical composition and microstructure of natural bamboo rat incisor enamel were synthesized and used as reinforcement in BisGMA/TEGDMA resins. The as‐prepared polycrystalline FeHA have a rod like morphology with uniformly dispersed iron. The effects of nanoparticle–resin weight ratios on the mechanical properties, tribological properties, and bioactivity of FeHA‐BisGMA/TEGDMA resins were investigated. In vitro bioactivity of the studied resin composites in artificial saliva showed that a dense and continuous apatite layer was formed on the surface of the resin composite. Findings revealed that doping a suitable content of FeHA nanoparticle, especially at 0.75 wt% FeHA, would significantly improve the tribological and mechanical properties as well as bioactivity of the dental resin composites. [ABSTRACT FROM AUTHOR]

Bisphenol A-glycidyl methacrylate (bis-GMA) and urethane dimethacrylate (UDMA) are usually combined with low-viscosity monomers to obtain more desirable viscosity, handling characteristics and general properties. The present study determined the flexural strength (FS), flexural modulus (FM), diametral tensile strength (DTS), and hardness (HV) of five matrices and composites based on these resins. The polymerization shrinkage stress (PSS) was also studied for the composites. The polymer matrices were formed using bis-GMA and UDMA. TEGDMA, HEMA and HDDMA acted as co-monomers. The composites had 45 wt.% of filler content. The highest FS and FM were obtained from the UDMA/bis-GMA/TEGDMA/HEMA matrix and the composite (matrix + filler). The best DTS values were obtained from the UDMA/bis-GMA/HEMA matrix and the composite. One of the lowest values of FS, FM, and DTS was obtained from the UDMA/bis-GMA/HDDMA matrix and the composite. All the composites demonstrated similar hardness values. The lowest polymerization shrinkage stress was observed for the UDMA/bis-GMA/TEGDMA/HEMA composite, and the highest PSS was observed for the UDMA/bis-GMA/TEGDMA/HDDMA composite. The addition of HEMA had a positive effect on the properties of the tested materials, which may be related to the improved mobility of the bis-GMA and UDMA monomers. [ABSTRACT FROM AUTHOR]

Aim: The purpose of this study was to evaluate the mechanical properties of an experimental self-healing dental composite model (SHDC) composed of SiO2 nanoparticles with varying percentages of triethylene glycol dimethacrylate (TEGDMA) monomer and N,N-dihydroxyethyl-p-toluidine (DHEPT) amine microcapsules. Materials and methods: Microcapsules were prepared by in-situ polymerisation of PUF shells, as explained in our previous work. The model SHDC included bisphenol A glycidyl dimethacrylate (Bis-GMA:TEGDMA) (1:1), 1 wt% phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (BAPO), 0.5 wt% benzoyl peroxide (BPO) catalyst, 20 wt% silanised silica dioxide (SiO2) (15 nm) and (0, 2.5, 5, 7.5, 10 wt%) of microcapsules (120 ± 45 μm). Light transmission, hardness, degree of conversion (DC), flexural strength and elastic modulus of the SHDC model were measured. Results: The degree of conversion of the SHDC ranged from 73 to 76% 24 h after polymerisation. Hardness measurements ranged from 22 to 26 VHN (p > 0.05); however, the flexural strength was adversely affected from 80 to 55 MPa with increasing microcapsules of up to 10 wt% in the composites (p < 0.05). Conclusion: Only flexural strength decreased drastically ~30% with increasing microcapsules (>10 wt%) in the composites. All other measured properties were not significantly affected. Accordingly, we recommend a stronger composite material that could be created by increasing the filler content distribution in order to achieve a hybrid self-healing composite with enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

The purpose of this review was to identify the various factors involved in polymerization shrinkage of dental composites and to discuss possible strategies of overcoming this drawback. The final setting reaction of dental composite material is followed by polymerization shrinkage of the material which leads to shrinkage stress and strain. This shrinkage stress and strain could result in debonding of the material, cuspal flexure, fracture of the tooth, microleakage and poor mechanical properties. PubMed and Google scholar databases were used to search through the past 30 years of literature using selected search criteria “Dental composite*[TW] AND (shrinkage*[TW] OR stress*[TW] OR strain*[TW])” to identify articles/book chapters discussing polymerization shrinkage and possible solutions. In total 46, articles/book chapters met the criteria for inclusion in the literature review. There were multiple factors that were identified to have an impact on polymerization shrinkage and consequently shrinkage stress and strain, which included the composition and viscosity of the material, modulus of elasticity acquired by the material, rate of polymerization, configuration factor and degree of conversion. On the other hand, the methods which could help minimize shrinkage involved alteration to the material including change in particle size, incorporation of inhibitors, and addition of silorane as well as use of various clinical techniques. It can be concluded that various strategies have been implemented to overcome the shrinkage stress and strain related to dental composites, however, further research is required to help in the development of the material. In addition, improvement in the placement techniques of the material needs further exploration to reduce this complication.

Among the newest trends in dental composites is the use of graphene oxide (GO) nanoparticles to assure better cohesion of the composite and superior properties. Our research used GO to enhance several hydroxyapatite (HA) nanofiller distribution and cohesion in three experimental composites CC, GS, GZ exposed to coffee and red wine staining environments. The presence of silane A-174 on the filler surface was evidenced by FT-IR spectroscopy. Experimental composites were characterized through color stability after 30 days of staining in red wine and coffee, sorption and solubility in distilled water and artificial saliva. Surface properties were measured by optical profilometry and scanning electron microscopy, respectively, and antibacterial properties wer e assessed against Staphylococcus aureus and Escherichia coli. A colour stability test revealed the best results for GS, followed by GZ, with less stability for CC. Topographical and morphological aspects revealed a synergism between GZ sample nanofiller components that conducted to the lower surface roughness, with less in the GS sample. However, surface roughness variation due to the stain was affected less than colour stability at the macroscopic level. Antibacterial testing revealed good effect against Staphylococcus aureus and a moderate effect against Escherichia coli.

The innovation of nanocellulose as reinforcement filler in composites has been a topic of interest in the development of new biomaterials. The objective of this study was to investigate the mechanical properties of a nanohybrid dental composite made of rice husk silica and loaded with different percentages of kenaf nanocellulose. Kenaf cellulose nanocrystals (CNC) were isolated and characterized using a transmission electron microscope (TEM) (Libra 120, Carl Zeiss, Germany). The experimental composite was fabricated with fiber loadings of 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 6 wt% silane-treated kenaf CNC, and subjected to a flexural and compressive strength test (n = 7) using an Instron Universal Testing Machine (Shimadzu, Kyoto, Japan), followed by a scanning electron microscopic assessment of the flexural specimen’s fracture surface using a scanning electron microscope (SEM) (FEI Quanta FEG 450, Hillsborough, OR, USA). Commercial composites Filtek Z350XT (3M ESPE, St. Paul, MN, USA), Neofil (Kerr Corporation, Orange, CA, USA) and Ever-X Posterior (GC Corporation, Tokyo, Japan) were used as a comparison. The average diameter of kenaf CNC under TEM was 6 nm. For flexural and compressive strength tests, one-way ANOVA showed a statistically significant difference (p < 0.05) between all groups. Compared to the control group (0 wt%), the incorporation of kenaf CNC (1 wt%) into rice husk silica nanohybrid dental composite showed a slight improvement in mechanical properties and modes of reinforcement, which was reflected in SEM images of the fracture surface. The optimum dental composite reinforcement made of rice husk was 1 wt% kenaf CNC. Excessive fiber loading results in a decline in mechanical properties. CNC derived from natural sources may be a viable alternative as a reinforcement co-filler at low concentrations.

Background and Objective: Dental composites' dependence on pricey imported components often raises price concerns and restricts accessibility in restorative dentistry. In Pakistan, using locally produced materials presents a viable alternative for more affordable and environmentally friendly dental treatments. This study aimed to develop and evaluate dental composites sourced from locally available materials in Pakistan for cost-effectiveness, performance, and durability., Methodology: A study comprising 385 patients, aged 18-65 years, who underwent composite restorations made of novel materials, was carried out at Sardar Begum Dental College, Peshawar, from January 2023 to December 2023. Patient comfort, aesthetic quality, and durability were the three main criteria used to assess clinical performance. The physical characteristics of adhesion strength, wear resistance, and hardness were evaluated in lab settings. Costs for materials, processing, and clinical application were all considered in a thorough cost study. SPSS version 26 (Armonk, NY: IBM Corp.) was used for the statistical analysis, and both descriptive and inferential statistics were used. The novel composites were compared with standard materials using t-tests, and cost differences were assessed. A p-value of less than 0.05 was considered statistically significant., Results: The novel composites exhibited superior performance with a durability of 12.57 ± 1.83 months (n = 385 patients), compared to 11.05 ± 2.38 months for conventional composites (p < 0.05). They also scored higher in aesthetic quality (8.35 ± 1.48 vs. 7.82 ± 1.59) and patient comfort (4.52 ± 0.79 vs. 4.27 ± 0.83) (p < 0.05). Laboratory tests showed greater hardness (48.79 ± 3.22 Vickers), better wear resistance (0.28 ± 0.05 mm³), and higher adhesion strength (22.96 ± 1.68 MPa) (p < 0.05). Cost analysis revealed significant savings, with total costs per patient of PKR 8,980 for novel composites vs. PKR 33,000 for conventional composites (p < 0.05)., Conclusion: Novel dental composites developed from locally sourced materials demonstrate superior performance and significant cost reductions, highlighting their potential to enhance the accessibility and affordability of dental care in Pakistan., Competing Interests: Human subjects: Consent for treatment and open access publication was obtained or waived by all participants in this study. The Ethical Review Committee of Sardar Begum Dental College and the Ethical Committee of Gandhara University issued approval #188/2022. Animal subjects: All authors have confirmed that this study did not involve animal subjects or tissue. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Ejaz et al.)

Objective: The aim of the study was to evaluate the influence of filler content, degradation media and time on the mechanical properties of different dental composites after in vitro aging. Materials and Methods: Specimens (1 mm3) of three commercially available composites (GrandioSO®, Arabesk Top®, Arabesk Flow®) with respect to their filler content were stored in artificial aging media: artificial saliva, ethanol (60%), lactic acid (pH 5) and citric acid (pH 5). Parameters (Vickers microhardness, compressive strength, elastic modulus, water sorption and solubility) were determined in their initial state (control group, n = 3 for microhardness, n = 5 for the other parameters) and after 14, 30, 90 and 180 days (n = 3 for microhardness, n = 5 for the other parameters for each composite group, time point and media). Specimens were also characterized with dynamic-mechanical-thermal analysis (compression tests, F = ± 7 N; f = 0.5 Hz, 1 Hz and 3.3 Hz; t = 0–170 °C). Results: Incorporation of fillers with more than 80 w% leads to significantly better mechanical properties under static and dynamic compression tests and a better water sorption behavior, even after chemical degradation. The influence of degradation media and time is of subordinate importance for chemical degradation. Conclusion: Although the investigated composites have a similar matrix, they showed different degradation behavior. Since dentine and enamel occur only in small layer thickness, a test specimen geometry with very small dimensions is recommended for direct comparison. Moreover, the use of compression tests to determine the mechanical parameters for the development of structure-compatible and functionally adapted composites makes sense as an additional standard. Clinical relevance Preferential use of highly filled composites for occlusal fillings is recommended. [ABSTRACT FROM AUTHOR]

We compare the clinical-technological and physicomechanical properties of hybrid domestic and foreign composites obtained by light polymerization. The specific features of the fracture of materials under the action of local loads applied by the Hertz indentation test with the use of acoustic emission (AE) are investigated. The polymers are ranked according to the degree of water absorption and the value of fracture load. By using the energy criterion for identification of the types of fracture by AE signals, the fraction of brittle fracture is estimated for each material. According to the results of complex analysis of the research data, we make recommendations concerning the proper choice of the composites that can be efficiently used in the dental practice. [ABSTRACT FROM AUTHOR]

In this study, a new generation antimicrobial azole-containing dental composite has been developed and evaluated. Polymerization has been realized by dispersing 1,2,4-Triazole, 3-amino-1,2,4-t-Triazole ve 5-Aminotetrazole functional SiO2 nanoparticles homogeneously into the resin. Azole-containing dental composites were characterized by FTIR spectroscopy to confirm the binding of azole-containing nanoparticles to BisGMA/TEGDMA resin. Scanned electron microscopic analysis results confirmed the homogeneous distribution of azole nanoparticles in the dental composites. X-ray diffraction studies have shown that the amorphous character of the materials is improved by the incorporation of azole nanoparticles into the structure. By thermogravimetric and differential scanning calorimetric analyzes, it has been determined that the thermal stability of azole dental composites greatly increased with the increase of nanoparticle content at low temperatures. The solubility and absorption of dental composites in water have been observed by keeping them in 37ºC distilled water, and their compliance with ISO requirements has been observed. The fact that the azole-containing dental composites show antimicrobial activity is the proof that they can be used in dentistry applications. [ABSTRACT FROM AUTHOR]

Introduction: The durability and longevity of composite restoration are much dependent on the accurate delivery of the energy required to polymerise the material. This study aimed to investigate the extent to which undergraduate dental students acquire and retain light‐curing skills following hands‐on training. Materials and Methods: Hands‐on training comprises faculty tutoring for critical aspects of the light‐curing procedure, such as distance and angulation of the light‐curing tip. Assessments of the students' ability to deliver a specified radiant exposure to class III and I simulated RBCs using a dental simulator (MARC‐PS®) at three different time points after the training. Data were analysed using repeated measure ANOVA. Results: Immediately after the training, students' performance on curing was improved (p <.05). Overall, the radiant exposure increased after training, but the students lost some of the benefits with time. For curing in the anterior section (anterior sensor‐class III), the mean radiant exposure values increased by approximately 20% after the training. After 2 years, the values were 15% greater than baseline values. For curing in the posterior section (posterior sensor‐class I), the mean radiant exposure values increased by approximately 150% after the training. A significant decrease (p <.05) was observed; however, the radiant exposure values were still 82% greater than the baseline after 2 years. Conclusion: A hands‐on training dedicated to light‐curing procedures facilitated acquisition and retention up to a 2‐year follow‐up of skill on how light cure composite inside the mouth. The training was more relevant for curing in posterior areas, where orientation can significantly impact light‐curing. A hands‐on training where the radiant exposure can be measure gave objective measurement metrics to guide the curing performance. This approach is an effective means of teaching practical skills to dental students. [ABSTRACT FROM AUTHOR]

Ceramic/polymer dental composites inspired on the microstructure of human enamel are produced by robocasting combined with polymer infiltration. Robocasting is first used to additively manufacture a network of interconnected hydroxyapatite (HAp) rods aligned perpendicular to the occlusal surface, mimicking the natural material. A co-continuous composite is then obtained by immersing the sintered ceramic skeleton in an epoxy resin bath that is subsequently cured. The mechanical performance of the resulting bioinspired composite was evaluated through biaxial bending and sliding-wear tests. The results obtained are compared with those of two commercial dental composites. Despite being a first prototype, the bioinspired material exhibited mechanical properties very close, both in terms of biaxial strength (63 ± 4 MPa) and wear resistance (specific wear rate (7 ± 2)·10−5 mm3/Nm), to the commercial solutions. The proposed ground-breaking strategy appears, then, as a very promising alternative for the production of innovative dental composites with near-net shape and improved durability. [ABSTRACT FROM AUTHOR]

[Display omitted] The project aims to evaluate whether inhalation of particles released upon grinding of dental composites may pose a health hazard to dentists. The main objective of the study was to characterize the dust from polymer-based dental composites ground with different grain sized burs and investigate particle uptake and the potential cytotoxic effects in human bronchial cells. Polymerized blocks of two dental composites, Filtek™ Z250 and Filtek™ Z500 from 3M™ ESPE, were ground with super coarse (black) and fine (red) burs inside a glass chamber. Ultrafine airborne dust concentration and particle size distribution was measured real-time during grinding with a scanning mobility particle sizer (SMPS). Filter-collected airborne particles were characterized with dynamic light scattering (DLS) and scanning electron microscopy (SEM). Human bronchial epithelial cells (HBEC-3KT) were exposed to the dusts in dose-effect experiments. Toxicity was measured with lactate dehydrogenase (LDH) assay and cell counting kit-8 (CCK8). Cellular uptake was observed with transmission electron microscopy (TEM). Airborne ultrafine particles showed that most particles were in the size range 15−35 nm (SMPS). SEM analysis proved that more than 80% of the particles have a minimum Feret diameter less than 1 μm. In solution (DLS), the particles have larger diameters and tend to agglomerate. Cell toxicity (LDH, CCK8) is shown after 48 h and 72 h exposure times and at the highest doses. TEM showed presence of the particles within the cell cytoplasm. Prolonged and frequent exposure through inhalation may have negative health implications for dentists. [ABSTRACT FROM AUTHOR]

Introduction. Secondary caries is the most important reason for replacement and removal of restorative materials containing composite resins, because caries causes infectious complications and many bacteria, including Streptococcus mutans and lactobacilli, which have been isolated from cariogenic plaques, once known that composites based on resins favour the growth of Streptococcus. Therefore, the use of composite resins with antimicrobial properties for the prevention of secondary decay will be very useful; to this end, we synthesized 4-amino-2H-chromen-2-one as a new antibacterial compound, used it in dental composites, and investigated its physical-mechanical properties. Materials and methods. In this experimental study, 4-amino-2H-chromen-2-one was synthesized by the reaction between 4-hydroxy coumarin and ammonium acetate and the antibacterial activity of flowable dental composites containing 0-5 wt% 4-amino-2H-chromen-2-one, as well as their mechanical and physical properties, influencing flowable dental composites, were investigated. Statistical analysis was performed using one-way ANOVA test (P < 0.001). Results and discussion. The direct contact test demonstrates that, by increasing the 4-amino-2H-chromen-2-one content, bacterial growth is significantly diminished (p<0.001). Average flexural strength results show that, with increasing 4-amino-2H-chromen-2-one until 2% in the composite, no significant difference was observed in flexural strength (p>0.001), while the mean of compressive strength results shows no significant difference between 0-4% groups (p>0.001). Conclusions. Incorporation of 4-amino-2Hchromen-2-one into flowable resin composites in 2% wt can reduce the activity of Streptococcus mutans. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dendritic porous silica (DPS) with controllable size ranging from 75 to 1000 nm were synthesized in the microemulsion. • The plausible mechanism of the structural regulation and size control of these DPS particles was proposed. • Dental composites filled with DPS-500 particles exhibited superior physicochemical properties and cytocompatibility. Porous materials, especially porous silica particles are of great interest in different areas, and have applied in dental composites as inorganic fillers, due to their potential in constructing micromechanical interlocking at the filler-resin matrix interfaces. However, the facile and precise synthesis of hierarchical porous silica with graded sizes is still a great challenge. Here, we synthesized dendritic porous silica (DPS) with center-radial hierarchical pores and controllable size ranging from 75 to 1000 nm by varying simultaneously the amounts of silica precursor and template in the microemulsion. A plausible nucleation-growth mechanism for the structural formation and the size tunability of the DPS particles was further put forward. These DPS particles were then formulated with Bis-GMA/TEGDMA resin. The particle size and morphology influenced the mechanical properties of dental composites. Particularly, DPS-500 particles (average size: 500 nm) exhibited the superior reinforcing effect, giving large improvements of 32.0, 96.7, 51.9, and 225.6% for flexural strength (S F), flexural modulus (E Y), compressive strength (S C), and work of fracture (WOF), respectively, over the DPS-75 filled composite. All DPS filler sized exhibited similar degree of conversions and curing depths. Furthermore, the DPS-500 filled composite presented better cytocompatibility than commercial Z250 XT. The facile synthesis of DPS particles developed here and the understanding of the influence of the filler size and morphology on the composite properties provide a shortcut to design porous silica with precise size control and dental composites with superior performance. These DPS particles could also have promising applications in biomedicine, catalysis, adsorption, and cancer therapy. [ABSTRACT FROM AUTHOR]

Although efforts have been put into the research in polymer-infiltrated ceramic network composites (PICNs), data are needed to understand the relationship between surface roughness and flexural strength. In this work, a novel dental restorative composite was fabricated via infiltrating mixtures of Bis-GMA/TEGDMA and UDMA/TEGDMA into partially sintered porous sodium aluminum silicate blocks and curing. Bars with different surface conditions were produced by sanding with abrasive and polishing. Flexural strength was measured using three-point-bending. Scanning electron microscopy (SEM) was employed to observe the microstructure of surface areas. One-way analysis of variance was applied for statistical calculations, with p < 0.05 being considered significant. Weibull plots were used to evaluate the reliability of flexural strength. The results demonstrated that the flexural strength of the resultant composites was affected by the scratch direction and the value of roughness. The flexural strength increased with decrease of surface roughness. A higher strength value was found for parallel types than for vertical types with nearly the same surface roughness. A large roughness value and a scratch direction perpendicular to tensile stress produced a low Weibull modulus. Of particular importance with this work is that these factors should be taken into consideration when using PICNs as dental restorative composites.

The performance of dental resin composites is crucially influenced by the sizes and distributions of inorganic fillers. Despite the investigation of a variety of functional particles, glass fillers and nanoscale silica are still the predominant types in dental materials. However, achieving an overall improvement in the performance of resin composites through the optimization of their formulations remains a challenge. This work introduced a "dense" microhybrid filler system with 85 wt % filler loading, leading to the preparation of self-developed resin composites (SRCs). Comparative evaluations of these five SRCs against four commercial products were performed, including mechanical property, polymerization conversion, and shrinkage, along with water sorption and solubility and wear resistance. The results showed that among all SRC groups, SRC3 demonstrated superior mechanical performance, high polymerization conversion, reduced shrinkage, low water absorption and solubility, and acceptable wear resistance. In contrast to commercial products, this optimal SRC3 material was comparable to Z350 XT in flexural and diametral tensile strength and better in flexural modulus and surface hardness. The use of a "dense" microhybrid filler system in the development of resin composites provides a balance between physicochemical property and wear resistance, which may be a promising strategy for the development of composite products.

Introduction of thiourethane (TU) oligomer to resin-based dental restorative materials reduces stress and improves fracture toughness without compromising conversion. Localization of TU at the resin-filler interface via silanization procedures may lead to more substantial stress reduction and clinical property enhancements. The objective of this study was to evaluate composite properties as a function of TU-functionalized filler concentration. TU oligomers were synthesized using click-chemistry techniques and subsequently silanized to barium glass filler. Resin-based composites were formulated using varying ratios of TU-functionalized filler and conventional methacrylate-silanized barium filler. Material property testing included thermogravimetric analysis, real-time polymerization kinetics and depth of cure, polymerization stress, stress relaxation and fracture toughness. Clinical property testing included water sorption/solubility, composite paste viscosity, and gloss and surface roughness measured before and after subjecting the samples to 6 h of continuous tooth brushing in a custom-built apparatus using a toothpaste/water mixture. Increasing TU-filler in the composite resulted in as much as a 78% reduction in stress, coupled with an increase in fracture toughness. Conversion was similar for all groups. After simulated tooth brushing, gloss reduction was lower for TU-containing composites and surface roughness was less than or equal to the control.

Poly methyl methacrylate (PMMA) is the dominant acrylic that is widely used to produce partial and complete dentures. Denture fractures are caused by fatigue owing to repetitive masticatory, flexural and impact loads produced by dropping. The mechanical properties of dentures have been developed by reinforcing with various agents like rubbers, fillers and fibers. Progressively, novel dental materials reinforcement tactics have been developed following the advancement in Nano dentistry. Nonetheless, the issue pertaining to the superior mechanical properties of the PMMA still exists albeit it’s biocompatible and aesthetic properties. In recent years, the nanostructure materials have received much attention due to their high surface area to volume ratio that boosts interaction and delivers new biological, physical, and chemical characteristics. Many studies have evaluated the usage of nanotubes and nanofiber in dental composites, however, the data estimating the reinforcement issue of nanotubes and nanofibers in PMMA have been scarce. This article is aimed to review the progress related to the development of mechanical properties of denture base materials in addition to the latest advances and prospective developments for PMMA acrylic resins reinforcement. Poly methyl methacrylate PMMA composites, strengthening of dentures, Nano-fillers surface treatment, biomedical Nano additives for mechanical improvement, Nano-fillers of PMMA, biomedical ceramic Nano-fillers, biomedical metallic materials as Nano-fillers, hybrid reinforcement of PMMA, biocompatibility of polymeric PMMA composite, biomaterial for dental applications.

Objective: The purpose of this study was to investigate the effect of Silver nanoparticle immobilized Halloysite Nanotubes (HNT/Ag) fillers on physicochemical, mechanical, and biological properties of novel experimental dental resin composite in order to compare with the properties of corresponding composites containing conventional glass fillers. Methods: Dental resin (Bis-GMA/TEGDMA with ratio 70/30) composites were prepared by incorporation of varied mass fraction of HNT/Ag. Experimental composites were divided into six groups, one control group and five experimental groups containing mass fraction 1 to 10.0 wt. % of HNT/Ag. Mechanical properties of the dental composites were recorded. Degree of conversion and depth of cure of the dental resin composites were assessed. Antimicrobial properties were assessed using agar diffusion test and evaluation of cytotoxicity were performed on NIH-3T3 cell line. Results: The inclusion of mass fractions (1–5 wt. %) of the HNT/Ag in dental resins composites, significantly improved mechanical properties. While, addition of larger mass fractions (7.5 and 10 wt. %) of the HNT/Ag did not show further improvement in the mechanical properties of dental resins composites. Theses composites also demonstrated satisfactory depth of cure and degree of conversion. A significant antibacterial activity was observed on S. mutans. No significant cytotoxicity was found on NIH-3T3 cell lines. Conclusion: The incorporation of HNT/Ag in Bis-GMA/TEGDMA dental resins composites resulted in enhancement in mechanical as well as biological properties for dental applications. Clinical significance: HNT/Ag containing dental composite is proposed to be highly valuable in the development of restorative dental material for patients with high risk of dental caries.

Poly methyl methacrylate (PMMA) is the dominant acrylic that is widely used to produce partial and complete dentures. Denture fractures are caused by fatigue owing to repetitive masticatory, flexural and impact loads produced by dropping. The mechanical properties of dentures have been developed by reinforcing with various agents like rubbers, fillers and fibers. Progressively, novel dental materials reinforcement tactics have been developed following the advancement in Nano dentistry. Nonetheless, the issue pertaining to the superior mechanical properties of the PMMA still exists albeit it's biocompatible and aesthetic properties. In recent years, the nanostructure materials have received much attention due to their high surface area to volume ratio that boosts interaction and delivers new biological, physical, and chemical characteristics. Many studies have evaluated the usage of nanotubes and nanofiber in dental composites, however, the data estimating the reinforcement issue of nanotubes and nanofibers in PMMA have been scarce. This article is aimed to review the progress related to the development of mechanical properties of denture base materials in addition to the latest advances and prospective developments for PMMA acrylic resins reinforcement. Poly methyl methacrylate PMMA composites, strengthening of dentures, Nano-fillers surface treatment, biomedical Nano additives for mechanical improvement, Nano-fillers of PMMA, biomedical ceramic Nano-fillers, biomedical metallic materials as Nano-fillers, hybrid reinforcement of PMMA, biocompatibility of polymeric PMMA composite, biomaterial for dental applications. [ABSTRACT FROM AUTHOR]

The purpose of this in vitro study is to evaluate the effect of the incorporation of silanized and non-silanized silica nanoparticles (~ 160 nm) in mechanical properties and surface roughness of self-cured acrylic resins. Five groups of samples were produced (with six specimens each), following the ISO 20795-1:2013 specifications. In the control group (Ctrl), no particles were added in the resin composition. Non-silanized silica nanoparticles were added either into the polymer (0.7 wt%, group G1) or into the monomer (0.27 wt%, G2). Two equivalent groups were formed for composite resins with silanized nanoparticles (groups G3 with 0.7 wt% incorporated into the polymer and G4 with 0.27 wt% added into the monomer). Data were submitted to Shapiro-Wilk (α = 0.05) and ANOVA/Tukey (α = 0.05). Nanoparticle-loaded resins showed similar microhardness as the control and a reduced flexural strength (20–27%) which was neither dependent on the amount of filler added nor in the method of nanoparticle incorporation. Surface silanization caused no major improvement in the mechanical behavior of the nanoresins but appears to improve dispersibility, as indicated by a smaller surface roughness. [ABSTRACT FROM AUTHOR]

The purpose of this review was to identify the various factors involved in polymerization shrinkage of dental composites and to discuss possible strategies of overcoming this drawback. The final setting reaction of dental composite material is followed by polymerization shrinkage of the material which leads to shrinkage stress and strain. This shrinkage stress and strain could result in debonding of the material, cuspal flexure, fracture of the tooth, microleakage and poor mechanical properties. PubMed and Google scholar databases were used to search through the past 30 years of literature using selected search criteria "Dental composite*[TW] AND (shrinkage*[TW] OR stress*[TW] OR strain*[TW])" to identify articles/book chapters discussing polymerization shrinkage and possible solutions. In total, articles/book chapters met the criteria for inclusion in the literature review. There were multiple factors that were identified to have an impact on polymerization shrinkage and consequently shrinkage stress and strain, which included the composition and viscosity of the material, modulus of elasticity acquired by the material, rate of polymerization, configuration factor and degree of conversion. On the other hand, the methods which could help minimize shrinkage involved alteration to the material including change in particle size, incorporation of inhibitors, and addition of silorane as well as use of various clinical techniques. It can be concluded that various strategies have been implemented to overcome the shrinkage stress and strain related to dental composites, however, further research is required to help in the development of the material. In addition, improvement in the placement techniques of the material needs further exploration to reduce this complication. [ABSTRACT FROM AUTHOR]

The aim of this study was an in-situ synthesis of hydroxyapatite (HA) on cellulose fibers to be used as a new reinforcing agent for dental restorations. The microwave irradiation method was used for synthesis and the materials were characterized with analytical techniques. The prepared dental resin composites were mechanically tested by a universal testing machine and electrodynamic fatigue testing system. FTIR, XRD, SEM/EDS analysis confirmed the successful synthesis of HA on cellulose fibers. The Alamar blue biocompatibility assay showed more than 90% cell viability for the prepared cellulose/HA. The mechanical properties of resin composites improved with cellulose content from 30 wt.% to 50 wt.% in the polymer matrix. Substantially, increasing the cellulose/HA content from 40% to 50% improved the mechanical properties. The results suggested that HA could be successfully synthesized on cellulose fibers using microwave irradiation and contributed to improving the mechanical properties of dental resin composites. [ABSTRACT FROM AUTHOR]

• CaAl and MgAl LDH dental composites were developed with varying LDH loading. • Fluoride absorption/release cycles were studied (five recharges) in DW and AS. • Water uptake, solubility, cation release, and mechanical properties were studied. • LDH-composites repeatedly absorbed/released fluoride maintaining a sustained release. • Physico-mechanical properties of composites were maintained with LDH-composites. This study aims to incorporate 2:1 MgAl and 2:1 CaAl layered double hydroxides (LDHs) in experimental dental-composites to render them fluoride rechargeable. The effect of LDH on fluoride absorption and release, and their physico-mechanical properties are investigated. 2:1 CaAl and 2:1 MgAl LDH-composite discs prepared with 0, 10 and 30 wt% LDH were charged with fluoride (48 h) and transferred to deionized water (DW)/artificial saliva (AS). Fluoride release/re-release was measured every 24 h (ion-selective electrodes) with DW/AS replaced daily, and samples re-charged (5 min) with fluoride every 2 days. Five absorption-release cycles were conducted over 10 days. CaAl and MgAl LDH rod-shaped specimens (dry and hydrated; 0, 10 and 30 wt%) were studied for flexural strength and modulus. CaAl and MgAl LDH-composite discs (0, 10, 30 and 45 wt% LDH) were prepared to study water uptake (over 7 weeks), water desorption (3 weeks), diffusion coefficients, solubility and cation release (ICP-OES). CaAl LDH and MgAl LDH-composites significantly increased the amount of fluoride released in both media (P < 0.05). In AS, the mean release after every recharge was greater for MgAl LDH-composites compared to CaAl LDH-composites (P < 0.05). After every recharge, the fluoride release was greater than the previous release cycle (P < 0.05) for all LDH-composites. Physico-mechanical properties of the LDH-composites demonstrated similar values to those reported in literature. The solubility and cation release showed a linear increase with LDH loading. LDH-composites repeatedly absorbed/released fluoride and maintained desired physico-mechanical properties. A sustained low-level fluoride release with LDH-composites could lead to a potential breakthrough in preventing early stage carious-lesions. [ABSTRACT FROM AUTHOR]

Bonding of resin composite fillings, for example following root‐canal treatment, is a challenge because remaining gaps grow and lead to failure. Here, phase‐contrast‐enhanced micro‐computed tomography (PCE‐CT) is used to explore methods of non‐destructive quantification of the problem, so that countermeasures can be devised. Five human central incisors with damaged crowns were root‐filled followed by restoration with a dental post. Thereafter, the crowns were rebuilt with a resin composite that was bonded conventionally to the tooth with a dental adhesive system (Futurabond U). Each sample was imaged by PCE‐CT in a synchrotron facility (ID19, European Synchrotron Radiation Facility) with a pixel size of 650 nm. The reconstructed datasets from each sample were segmented and analysed in a semi‐automated manner using ImageJ. PCE‐CT at sub‐micrometre resolution provided images with an impressive increased contrast and detail when compared with laboratory micro‐computed tomography. The interface between the dental adhesive and the tooth was often strongly disrupted by the presence of large debonded gaps (on average 34% ± 15% on all surfaces). The thickness of the gaps spanned 2 µm to 16 µm. There was a large variability in the distribution of gaps within the bonding area in each sample, with some regions around the canal exhibiting up to 100% discontinuity. Although only several micrometres thick, the extensive wide gaps may serve as gateways to biofilm leakage, leading to failure of the restorations. They can also act as stress‐raising 'cracks' that are likely to expand over time in response to cyclic mechanical loading as a consequence of mastication. The observations here show how PCE‐CT can be used as a non‐destructive quantitative tool for understanding and improving the performance of clinically used bonded dental restorations. [ABSTRACT FROM AUTHOR]

Water sorption, high volumetric shrinkage, polymerization stress, and potential estrogenic effects triggered by leached compounds are some of the major concerns related to BisGMA-TEGDMA co-monomer systems used in dental composites. These deficiencies call for the development of alternative organic matrices in order to maximize the clinical lifespan of resin composite dental restorations. This study proposes BisGMA-free systems based on the combination of UDMA and a newly synthesized diurethane dimethacrylate, and evaluates key mechanical and physical properties of the resulting materials. 2EMATE-BDI (2-hydroxy-1-ethyl methacrylate) was synthesized by the reaction between 2-hydroxy-1-ethyl methacrylate with a difunctional isocyanate (1.3-bis (1- isocyanato-1-methylethylbenzene) – BDI). The compound was copolymerized with UDMA (urethane dimethacrylate) at 40 and 60 wt%. UDMA copolymerizations with 40 and 60 wt% TEGDMA (triethylene glycol dimethacrylate) were tested as controls, as well as a formulation based in BisGMA (bisphenol A-glycidyl methacrylate)-TEGDMA 60:40% (BT). The organic matrices were made polymerizable by the addition of DMPA (2.2-dimethoxyphenoxy acetophenone) and DPI-PF6 (diphenyliodonium hexafluorophosphate) at 0.2 and 0.4 wt%, respectively. Formulations were tested as composite with the addition of 70 wt% inorganic content consisting of barium borosilicate glass (0.7 μm) and fumed silica mixed in 95 and 5 wt%, respectively. All photocuring procedures were carried out by a mercury arc lamp filtered to 320–500 nm at 800 mW/cm2. The experimental resin composites were tested for kinetics of polymerization and polymerization stress in real time. Flexural strength, elastic modulus, water sorption, and solubility were assessed according to ISO 4049. Biofilm formation was analyzed after 24 h by luciferase assay. Data were statistically analyzed by one-way ANOVA and Tukey's test (α ≤ 0.05). In general, the addition of 2EMATE-BDI into the formulations decreased the maximum rate of polymerization (RP MAX), the degree of conversion at RP MAX (DC at RP MAX), and the final degree of conversion (final DC). However, these reductions did not compromise mechanical properties, which were comparable to the BT controls, especially after 7-day water incubation. The incorporation of 60 wt% 2EMATE-BDI reduced water sorption of the composite. 2EMATE-BDI containing formulations showed reduction in polymerization stress of 30% and 50% in comparison to BT control and TEGDMA copolymerizations, respectively. Biofilm formation was similar among the tested groups. The use of the newly synthesized diurethane dimethacrylate as co-monomer in dental resin composite formulations seems to be a promising option to develop polymers with low-shrinkage and potentially decreased water degradation. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study was to explore the effect of Chlorhexidine-loaded Halloysite nanotubes (HNT/CHX) fillers (diverse mass fractions from 1 to 10 wt.%) on physicochemical, morphological and biological properties of newly developed experimental dental resin composite, in order to compare with the properties of composites composed of conventional glass fillers. Methods: The dental resin composites were prepared by incorporating various proportions of HNT/CHX. Six different groups of specimens: control group and five groups composed of varied mass fractions of HNT/CHX (e.g., 1.0, 2.5, 5.0, 7.5 and 10 wt.%) as fillers in each group were fabricated. Mechanical properties of the composites were monitored, using UTM. The degree of conversion of dental resin composites and their depth of cure were also evaluated. Antimicrobial properties of dental composites were studied in vitro by applying agar diffusion test on strain Streptococcus mutans and cytotoxicity were studied using NIH-3T3 cell line. Results: The incorporation of varied mass fractions (1.0 to 5.0 wt.%) of HNT/CHX in dental resins composites enhanced mechanical properties considerably with significant antibacterial activity. The slight decrease in curing depth and degree of conversion values of composites indicates its durability. No cytotoxicity was noticed on NIH-3T3 cell lines. Significance: Consistent distribution of HNT/CHX as a filler into dental composites could substantially improve not only mechanical properties but also biological properties of dental composites. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate different aging method effects on color change of bulk-fill resin composite (BFRC) and anterior resin composite (ARC). Sixty disc-shaped samples (8-mm in diameter and 4-mm thick) were prepared (30 samples in each composite). Samples were divided into 3 groups according to different aging procedures which were thermal cycling [TC], autoclave aging [AA] and water aging [WA] (n=10). Color measurements of the samples were recorded before and after aging. Color changes were calculated using the CIEDE2000 (ΔE00) formula. Color measurements of the samples were recorded before aging. After aging, color measurements were repeated and color changes were calculated using the CIEDE2000 (ΔE00) formula. Color differences were analyzed using a two -way analysis of variance and Holm-Sidak comparison. Significant differences were observed among the composite groups and aging methods (p<0.05). All aging methods caused color change in composites. ARC showed less color change than BFRC. WA caused minimal color change and showed significantly difference than other aging methods. However no significat difference in color change were found between TC and AA. The results provide information on the color stability of composite resins ARC and BFRC after different aging methods. In terms of esthetic dentistry, ARC composites should be used in the anterior region, where there is a high risk of caries due to coloration. [ABSTRACT FROM AUTHOR]

This study systematically reviews the literature on self-healing microcapsule technology and evaluates the biocompatibility of self-healing microcapsules and the efficiency of crack repair within resin-based dental composites. An electronic search was carried out using the following databases: MedLine (PubMed) , Embase, the Cochrane Library and Google Scholar. All titles and abstracts of the articles and patents found were analysed and selected according to the eligibility criteria. Only studies published in English were included; the outcomes sought for this review were dental resin composites with self-healing potential. There were no restrictions on the type of self-healing system involved in dental resin composites. The search yielded 10 studies and 2 patents involving self-healing approaches to dental resin composites. According to the current literature on self-healing dental resin composites, when a crack or damage occurs to the composite, microcapsules rupture, releasing the healing agent to repair the crack with a self-healing performance ranging from 25% to 80% of the virgin fracture toughness. Self-healing strategies used with resin composite materials have, to date, been bioinspired. So far, self-healing microcapsule systems within dental composites include poly urea-formaldehyde (PUF) or silica microcapsules. The main healing agents used in PUF microcapsules are DCPD monomer and TEGDMA-DHEPT, with other agents also explored. Silica microcapsules use water/polyacid as a healing agent. All self-healing systems have shown promising results for self-repair and crack inhibition, suggesting a prolonged life of dental composite restorations. More investigations and mechanical enhancements should be directed toward self-healing technologies in dental resin composites. [ABSTRACT FROM AUTHOR]

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Aim: The purpose of this study was to evaluate the mechanical properties of an experimental self-healing dental composite model (SHDC) composed of SiO2 nanoparticles with varying percentages of triethylene glycol dimethacrylate (TEGDMA) monomer and N,N-dihydroxyethyl-p-toluidine (DHEPT) amine microcapsules. Materials and methods: Microcapsules were prepared by in-situ polymerisation of PUF shells, as explained in our previous work. The model SHDC included bisphenol A glycidyl dimethacrylate (Bis-GMA:TEGDMA) (1:1), 1 wt% phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide (BAPO), 0.5 wt% benzoyl peroxide (BPO) catalyst, 20 wt% silanised silica dioxide (SiO2) (15 nm) and (0, 2.5, 5, 7.5, 10 wt%) of microcapsules (120 ± 45 μm). Light transmission, hardness, degree of conversion (DC), flexural strength and elastic modulus of the SHDC model were measured. Results: The degree of conversion of the SHDC ranged from 73 to 76% 24 h after polymerisation. Hardness measurements ranged from 22 to 26 VHN (p > 0.05); however, the flexural strength was adversely affected from 80 to 55 MPa with increasing microcapsules of up to 10 wt% in the composites (p < 0.05). Conclusion: Only flexural strength decreased drastically ~30% with increasing microcapsules (>10 wt%) in the composites. All other measured properties were not significantly affected. Accordingly, we recommend a stronger composite material that could be created by increasing the filler content distribution in order to achieve a hybrid self-healing composite with enhanced mechanical properties.

Introduction Composite materials used in dentistry indicate adverse biological effects in laboratory conditions. One reason for this activity is incomplete conversion of their polymer matrix, favoring chemical instability and release of biologically harmful components to the external environment. Aim The aim of the study was to assess the degree of conversion of restorative materials commonly available on the European market and to examine the cytotoxic effects of their eluates in vitro. Material and Methods Using the Fournier transform infrared spectroscopy (FTIR) technique of analysis, the degree of polymer matrix conversion of 6 restorative materials was examined: Gradia Direct, Arkon, Filtek Z550, Herculite XRV, Tetric Evo Ceram, Charisma, polymerized with LED light. In order to assess the cytotoxicity of eluates of the studied materials obtained after 1 hour , 24 hours and 7 days, the MTT assay was used in cultured 3T3 cells. The results were statistically analyzed at significance level of p=0.05. Results The conversion degree of the assessed polymers ranged from 31.56% for Tetric Evo Ceram to 75.84% for Arcon. The strongest (p=0.05) cytotoxic effect was demonstrated after 7-day observation of Tetric Evo Ceram eluates, reducing the metabolic activity of cells down to 56%. A positive correlation (r(x, y) = 0.62) between the degree of conversion of composite materials and cytotoxic effects of their eluates on cell cultures was confirmed. Conclusions 1. Restorative dental materials are chemically unstable in the conditions of the present study. 2. Polymer-based restorative dental materials available on the European market demonstrate cytotoxic properties constituting a potential threat to the patients’ health.

Background/Objectives Pit and fissure caries constitute a predominant portion, approximately 90% in permanent posterior teeth and 44% in primary teeth among children and adolescents. Among various preventive modalities, pit and fissure sealants play a pivotal role in safeguarding these vulnerable areas. Categorized by materials such as glass ionomer, composites, and polyacid-modified glass ionomers, these sealants offer effective protection. This study aims to evaluate the efficacy of glass ionomer-based pit and fissure sealants in terms of retention rate at 12-month post-procedure period in permanent first molars. Methodology This study was conducted at the Department of Operative Dentistry, Nishtar Institute of Dentistry, Multan, Pakistan. Fifty-six children, aged 7 to 12 years, presenting with pit and fissure caries in permanent first molar teeth were enrolled. Glass ionomer sealant was meticulously applied to the affected pits and fissures. The efficacy was assessed after 12 months based on predefined criteria. Results The age of participants ranged from 7 to 12 years, with a mean age of 9.24 ± 1.38 years. Among the 56 patients, 23 (41.2%) were male and 33 (58.8%) were female. Sealant retention was noted in 31 (55.35%) patients, while 25 (44.65%) experienced sealant loss. In the 7 to 9-year age group, 19 demonstrated complete sealant retention, whereas in the 10 to 12-year age group, 12 exhibited complete retention. Concerning gender distribution, 17 males and 14 females exhibited complete sealant retention. Conclusion Glass ionomer-based sealants demonstrate excellent properties for pit and fissure sealing owing to their low technique sensitivity, cost-effectiveness, and favorable retention rates. Therefore, they represent an optimal choice for this preventive dental procedure., Competing Interests: The authors have declared that no competing interests exist., (Copyright © 2024, Nazir et al.)

The aim of our study is to develop amine-free photoinitiating systems (PISs) for the polymerization of representative dental methacrylate resins under blue light irradiation. PISs based on camphorquinone (CQ)/sulfinate and CQ/sulfonate, eventually in combination with an iodonium salt, are proposed and compared to the well-established CQ/amine system. The polymerization performances of thick (1.4 mm) samples of different methacrylate blends upon exposure to a commercial blue LED centered at 477 nm under air are described. Finally, the performances of the new developed PISs are evaluated for dental composites application. FTIR is used to monitor the photopolymerization profiles. ESR spectroscopy and electrochemical experiments are used to identify the radicals generated. Mechanical properties measurements and color stability measurements are carried out to determine the key properties of the dental composites prepared. The performances of the new proposed PISs for the photopolymerization of thick (1.4 mm) samples of methacrylate upon exposure to a blue dental LED under air are excellent. Similar or better performances and bleaching properties are obtained with the new proposed amine-free systems compared to those reached with the CQ/amine reference system. Dental composites with excellent mechanical properties and exceptional color stability are obtained. The involved chemical mechanisms for the initiation step were also established. [ABSTRACT FROM AUTHOR]

Purpose: To determine the effect of aging methods on the fracture toughness of a conventional Bis-GMA-based resin composite (Filtek Supreme), an ormocer-based resin composite (Admira), and an experimental hydrophobic oxirane/acrylate interpenetrating network resin system (OASys)-based composite. Methods: A 25 × 5 × 2.8-mm stainless-steel mold with 2.5 mm single-edge center notch, following ASTM standards [E399-90], was used to fabricate 135 specimens (n = 15) of the composite materials and randomly distributed into groups. For the baseline group, specimens were fabricated and then tested after 24-h storage in water. For the biofilm challenge, specimens were randomly placed in a six-well tissue culture plate and kept at 37 °C with bacterial growth media (Brain Heart Infusion (BHI); Streptococcus mutans) changed daily for 15 days. For the water storage challenge, specimens were kept in 5 ml of deionized distilled autoclaved water for 30 days at 37 °C. μCT evaluation by scanning the specimens was performed before and after the proposed challenge. Fracture toughness (KIc) testing was carried out following the challenges. Results: μCT surface area and volume analyses showed no significant changes regardless of the materials tested or the challenge. Filtek and Admira fracture toughness was significantly lower after the biofilm and water storage challenges. OASys mean fracture toughness values after water aging were significantly higher than that of baseline. Toughness values for OASys composites after biofilm aging were not statistically different when compared to either water or baseline values. Conclusion: The fracture toughness of Bis-GMA and ormocer-based dental resin composites significantly decreased under water and bacterial biofilm assault. However, such degradation in fracture toughness was not visible in OASys-based composites. Clinical significance: Current commercial dental composites are affected by the oral environment, which might contribute to the long-term performance of these materials. [ABSTRACT FROM AUTHOR]