Determination of fatty acid uptake and desaturase activity in mammalian cells by NMR-based stable isotope tracing.

BACKGROUND: Mammalian cells both import exogenous fatty acids and synthesize them de novo. Palmitate, the end product of fatty acid synthase (FASN) is a substrate for stearoyl-CoA desaturases (Δ-9 desaturases) that introduce a single double bond into fatty acyl-CoA substrates such as palmitoyl-CoA and stearoyl-CoA. This process is particularly upregulated in lipogenic tissues and cancer cells. Tracer methodology is needed to determine uptake versus de novo synthesis of lipids and subsequent chain elongation and desaturation. Here we describe an NMR method to determine the uptake of 13C-palmitate from the medium into HCT116 human colorectal cancer cells, and the subsequent desaturation and incorporation into complex lipids. RESULTS: Exogenous 13C16-palmitate was absorbed from the medium by HCT116 cells and incorporated primarily into complex glycerol lipids. Desaturase activity was determined from the quantification of double bonds in acyl chains, which was greatly reduced by ablation of the major desaturase SCD1. SIGNIFICANCE: The NMR approach requires minimal sample preparation, is non-destructive, and provides direct information about the level of saturation and incorporation of fatty acids into complex lipids.

Synthesis of a novel monomer "DDTU-IDI" for the development of low-shrinkage dental resin composites.

OBJECTIVE: The current dental resin composites often suffer from polymerization shrinkage, which can lead to microleakage and potentially result in recurring tooth decay. This study presents the synthesis of a novel monomer, (3,9-diethyl-1,5,7,11-tetraoxaspiro[5,5]undecane-3,9-diyl)bis(methylene) bis((2-(3-(prop-1-en-2-yl)phenyl)propan-2-yl)carbamate) (DDTU-IDI), and evaluates its effect in the formulation of low-shrinkage dental resin composites. METHODS: DDTU-IDI was synthesized through a two-step reaction route, with the initial synthesis of the required raw material monomer 3,9-diethyl-3,9-dihydroxymethyl-1,5,7,11-tetraoxaspiro-[5,5] undecane (DDTU). The structures were confirmed using Fourier-transform infrared (FT-IR) spectroscopy and hydrogen nuclear magnetic resonance (1HNMR) spectroscopy. Subsequently, DDTU-IDI was incorporated into Bis-GMA-based composites at varying weight percentages (5, 10, 15, and 20 wt%). The polymerization reaction, degree of conversion, polymerization shrinkage, mechanical properties, physicochemical properties and biocompatibility of the low-shrinkage composites were thoroughly evaluated. Furthermore, the mechanical properties were assessed after a thermal cycling test with 10,000 cycles to determine the stability. RESULTS: The addition of DDTU-IDI at 10, 15, and 20 wt% significantly reduced the polymerization volumetric shrinkage of the experimental resin composites, without compromising the degree of conversion, mechanical and physicochemical properties. Remarkably, at a monomer content of 20 wt%, the polymerization shrinkage was reduced to 1.83 ± 0.53%. Composites containing 10, 15, and 20 wt% DDTU-IDI exhibited lower water sorption and higher contact angle. Following thermal cycling, the composites exhibited no significant decrease in mechanical properties, except for the flexural properties. SIGNIFICANCE: DDTU-IDI has favorable potential as a component which could produce volume expansion and increase rigidity in the development of low-shrinkage dental resin composites. The development of low-shrinkage composites containing DDTU-IDI appears to be a promising strategy for reducing polymerization shrinkage, thereby potentially enhancing the longevity of dental restorations.

Effect of silver diamine fluoride on the longevity of the bonding properties to caries-affected dentine.

OBJECTIVES: This study aimed to evaluate the adhesive properties in dentine after the application of silver diamine fluoride (SDF) on carious dentine lesions immediately and after 2 years of water storage. METHODS: 96 human molars used were subjected to artificial dentine caries production, and then randomly divided into 12 experimental groups according to 1. application of an SDF solution (carious dentine lesion without SDF treatment [control], with 12 % silver diamine fluoride [SDF 12 %] or 38 % silver diamine fluoride [SDF 38 %]); 2. Universal adhesives (Clearfil Universal Bond Quick [CUQ] and Single Bond Universal [SBU]); 3. adhesive strategy (etch-and-rinse [ER] and self-etch [SE]). After restoration, the specimens were sectioned and submitted to the microtensile bond strength test (µTBS) and energy-dispersive X-ray spectrometry analysis (SEM/EDX). All tests were performed immediately and after 2 years of water storage. Data from the µTBS were analyzed using four-way ANOVA and Tukey's test (α = 0.05). RESULTS: Only the interaction of factors 'SDF' vs 'time' was significant (p = 0.03). After 2 years of storage, the groups where SDF was applied showed higher µTBS values compared to the control group. No significant decrease in µTBS values was observed for SBU when comparing immediate and 2-year results, but a significant reduction in µTBS values was observed after 2 years for CUQ. CONCLUSION: Independent of the adhesive strategy, the use of SDF may be a promising alternative to maintain the bonding of universal adhesives to carious dentinal lesions. CLINICAL SIGNIFICANCE: This study may clarify and support clinicians regarding the longevity of resin-based restoration in caries-affected dentine treated with silver diamine fluoride.

Residual Monomer Release after the Polymerization of Different-Colored Flowable Compomer.

BACKGROUND: Compomers are restorative materials commonly used in pediatric dentistry. It is important to investigate the monomer release of materials used especially in pediatric patients. The aim of this study was to evaluate the residual monomer released from different-colored flowable compomers at five polymerization times. MATERIALS AND METHODS: Three experimental groups were formed: Group 1: pink flowable compomer (Twinky Star, VOCO, Germany), Group 2: blue flowable compomer (Twinky Star, VOCO), Group 3: white flowable compomer, A2 color of Dyract XP (Dentslpy DeTrey, Konstanz, Germany). For each group, samples were prepared using standard cylindrical Teflon molds (n = 10), and the compomers were cured using a light-emitting diode (LED) source in accordance with the manufacturer's recommendations. During each time period, the number of residual monomers: bisphenol-A glycidyl methacrylate (bis-GMA), urethane dimethacrylate (UDMA), hydroxyethyl methacrylate (HEMA), and triethylene glycol dimethacrylate (TEGDMA) were determined with high-performance liquid chromatography (HPLC). All data were analyzed statistically. RESULTS: In all groups, the amount of residual monomers increased after 1-h release periods (P < 0.05). For 2 weeks, the total residual monomers released were determined at most in Group 3 and at least in Group 1. However, there was no significant difference between the groups in terms of released amounts of monomers (P > 0.05). CONCLUSIONS: According to the study, when the total amount of residual monomer released from all groups was compared, no difference was found and it was observed that none of them exceeded the toxic dose. Flowable colored compomers can be used as safely as white compomers in pediatric dentistry.

Bond Strength, Microleakage, Microgaps, and Marginal Adaptation of Self-adhesive Resin Composites to Tooth Substrates with and without Preconditioning with Universal Adhesives.

PURPOSE: This study investigated and compared the bond strengths, microleakage, microgaps, and marginal adaptation of self-adhesive resin composites (SAC) to dentin with or without universal adhesives. MATERIALS AND METHODS: Dentin surfaces of 75 molars were prepared for shear and microtensile bond strength testing (SBS and µTBS). Silicon molds were used to build up direct restorations using the following materials to form 5 groups: 1. Surefil One; 2. Prime&Bond active Universal Adhesive + Surefil One; 3. Vertise Flow; 4. OptiBond Universal + Vertise Flow; 5. Scotchbond Universal + Filtek Z500 (control group). Bonded specimens were thermocycled 10,000x before being tested either for SBS or µTBS using a universal testing machine at a crosshead speed of 0.5 mm/min. Direct mesial and distal class-II cavities were created on 100 sound premolars, with the gingival margin of distal cavities placed below CEJ and restored according to the five groups. After thermocycling, microleakage scores were assessed following immersion of restored premolars in 2% methylene blue dye for 24 h, while marginal gaps and adaptation percentages were investigated on epoxy resin replicas under SEM at magnifications of 2000X and 200X, respectively. Results were statistically analyzed with parametric and non-parametric tests as applicable, with a level of significance set at α = 0.05. RESULTS: Bond strengths, microleakage scores, microgaps, and percent marginal adaptation of Surefil One and Vertise Flow were significantly (p < 0.001) inferior to the control group. Dentin preconditioning with universal adhesives significantly increased the study parameter outcomes of Surefil One and Vertise Flow, yet they were still significantly below the performance of the control group. CONCLUSION: Conventional resin composite outperformed the SAC whether applied solely or in conjunction with their corresponding universal adhesives.

Evaluation of the amount of residual monomer released from different flowable composite resins.

Today, resin materials are used in the restoration of permanent and deciduous teeth or as fissure sealants. The materials can contain different types of monomers (Bis-GMA, UDMA, TEGDMA). These monomers can be released into the oral cavity after polymerization. Residual monomers released from resin-containing restorative materials after polymerization have been reported to have negative effects on mechanical properties. The aim of our study is to evaluate the amount of residual monomers released after polymerization of different flowable composite resin materials using two different modes of LED light source. Composite disc samples (8 mm diameter/2 mm depth) prepared for each material group were polymerized using two different modes of the LED light device (Standard mode and extra power mode). HPLC (High Performance Liquid Chromatography) device was used to measure the amount of residual monomer release at 1 h, 1 day, 3 days and 7 days periods. Pairwise comparison of the differences between the materials was performed by Post-hoc test. For each residual monomer, the Kruskal Wallis test was used to analyze the difference between the materials in standard mode and the difference between the materials in extra power mode. According to the results of the study; Grandio flow flowable composite showed the highest release of TEGDMA and Bis-GMA while SDR® Flow flowable composite showed the lowest release of TEGDMA, Bis-GMA and UDMA. For all materials, the extra power mode resulted in more residual monomer release. TEGDMA and Bis-GMA release was detected in all tested flowable composites at all time periods.

Repair bond strength of a new self-adhesive composite resin to three different resin-matrix ceramic CAD-CAM materials.

This study aimed to evaluate the shear bond strength of two flowable composite resins to resin-matrix ceramic CAD-CAM materials.Fifty-four plates obtained from Lava Ultimate (LU), Cerasmart (CS), and Vita Enamic (VE) CAD-CAM blocks were assigned to nine groups: N0: Nova Compo SF (NCSF), N1: Silane/Single Bond Universal (SBU)/NCSF, N2: SBU/NCSF, N3: Silane/G-Premio Bond (GPB)/NCSF, N4: GPB/NCSF, G1: Silane/SBU/G-aenial Universal Injectable Composite (GUIC), G2: SBU/GUIC, G3: Silane/GPB/GUIC, G4: GPB/GUIC. After the repair procedures, shear bond strength values were analyzed. Silane pre-application decreased bond strength in most LU and CS groups but increased it in VE. NCSF performed better than GUIC in all CAD-CAM's with similar adhesive protocols. SBU in combination with NSCF had the highest bond strength among all repair procedures in LU and CS. Silane-containing universal adhesives in combination with self-adhesive resin composites should be used to repair resin-matrix ceramic materials.

Cytotoxicity evaluation, antibacterial effect, and degree of conversion of QAM-containing adhesives.

The aim of this study was to evaluate the influence of adding quaternary ammonium methacrylates (QAMs) to experimental adhesives by assessing the degree of conversion (DC), cytotoxicity against keratinocytes and fibroblasts, and antibacterial activity against biofilm formation. Two QAMs were added to an experimental adhesive: dimethylaminododecyl methacrylate bromododecane (DMADDM) or dimethylaminododecyl methacrylate bromohexadecane (DMAHDM) at three concentrations each: 1, 2.5, and 5 wt.%. Experimental adhesive without QAMs (control group) and commercially available Transbond XT Primer (3M Unitek, Monrovia, California, USA) were used for comparisons. The adhesives were tested for DC, cytotoxicity against keratinocytes and fibroblasts, and antibacterial activity against biofilm formation. DC, cytotoxicity against fibroblasts, and antibacterial activity were analyzed using one-way ANOVA and Tukey's multiple comparisons. Cytotoxicity against keratinocytes was evaluated using the Kruskal Wallis and Dunn's post-hoc (α = 5%) tests. Transbond showed lower DC as compared to 5% DMAHDM, 1% DMADDM, and 5% DMADDM (p < 0.05). However, all groups presented proper DC when compared to commercial adhesives in the literature. In the evaluation of cytotoxicity against keratinocytes, Transbond induced higher viability than 2.5 wt.% groups (p < 0.05). Against fibroblasts, Transbond induced higher viability as compared to 5 wt.% groups (p < 0.05). DMAHDM at 5 wt.% reduced biofilm formation when compared to all the other groups (p < 0.05). Despite their cytotoxic effect against keratinocytes, gingival fibroblasts showed higher viability. DMAHDM at 5 wt.% decreased Streptococcus mutans viability. The incorporation of DMAHDM at 5 wt.% may be a strategy for reducing the development of white spot lesions.

Monomer release, cell adhesion, and cell viability of indirect restorative materials manufactured with additive, subtractive, and conventional methods.

PURPOSE: The aim of this study was to measure residual monomer, cell adhesion, and cell viability of 3-dimensional printable permanent resin (PR), hybrid ceramic block (HCB), and indirect composite (IC) produced with additive, subtractive, and conventional techniques. METHODS: Five 8 × 8 × 2 mm3 samples of each material were prepared for each experiment. In a 24-h period, monomer release was analyzed with high-performance liquid chromatography, and cell viability and adhesion were evaluated with the water-soluble tetrazolium salt test. Data were analyzed with IBM SPSS Statistics 26.0 statistical software, and results were regarded as significant at α = 0.05. RESULTS: Monomer release (triethylene glycol dimethacrylate, urethane dimethacrylate, and Bisphenol A glycerolate dimethacrylate) was significantly higher in the IC group. Mean cell viability was significantly lower in the HCB group than in the IC group. CONCLUSION: All monomers in the tested materials were released at rates that were below clinical significance. Cell adhesion rates in the groups were similar. Cytotoxic response was classified as minor in the HCB and PR groups and non-cytotoxic in the IC group.

Antimicrobial dental composites with K18-methyl methacrylate and K18-filler.

OBJECTIVE: To determine the effects of using K18-methyl methacrylate (K18-MMA) and K18-Filler on composite cure, esthetic, mechanical, polymerization shrinkage, and antimicrobial properties. METHODS: K18-MMA (0-20% w/w) was used to replace TEGDMA in a 70:30 Bis-GMA:TEGDMA composite filled to 70% w/w with barium glass or K18-Filler. Composite degree of cure (Rockwell15T hardness and near Infrared FTIR), hydrophilicity (contact angle measurements), translucency (transparency parameter measurements, TP), mechanical (3-point bend test), polymerization shrinkage (volumetric shrinkage and shrinkage stress), and antimicrobial properties (colony counting assay) against Streptococcus mutans, Streptococcus sanguinis, and Candida albicans were determined. RESULTS: All experimental groups had comparable degrees of cure (near Infrared FTIR and Rockwell15T Hardness), TP, moduli, polymerization volumetric shrinkages and shrinkage stresses to those of controls (Bonferroni corrected p > 0.0018). Only one group (15% K18-MMA+K18-Filler) had significantly different (lower) contact angles as compared to that of controls (Bonferroni corrected p < 0.0018). Most of the K18-Filler-containing composites had significantly lower ultimate transverse strengths (UTS) than controls (Bonferroni corrected p < 0.0018). Controls had significantly greater S mutans colony counts than 15% and 20% w/w K18-MMA+K18-Filler groups, and greater S sanguinis and C albicans colony counts than K18-containing groups. Of the composites with that provided significant antimicrobial properties against S. mutans, S. sanguinis, and C. albicans, only the 20% K18-MMA+K18-Filler group had significantly lower UTS than controls. SIGNIFICANCE: Composites with K18-MMA and K18-Filler with comparable physical properties to control composites and significant antimicrobial properties have been developed. K18-MMA and K18-Filler seem to be suitable for incorporation into commercial dental resins.

Optical effects of graphene addition on adhesives for orthodontic lingual retainers.

The objective of this study was to determine the effects on the colour of adding increasing concentrations of graphene to orthodontic fixed retainer adhesives and to evaluate changes in optical transmission during light curing and the resultant degree of conversion. Two different types of adhesives commonly used for fixed retainers were investigated: A packable composite (Transbond) and a flowable composite (Transbond Supreme). Graphene was added to the adhesives in three different concentrations (0.01, 0.05, and 0.1 wt%). Adhesives without graphene addition were set as control groups. A Minolta colourimeter was used to measure the colour and translucency parameters. Irradiance transmitted during curing was quantified using MARC Light Collector. Fourier-transform infrared spectroscopy was used to record degree of conversion. Data were statistically analysed with the Student's t-test and one-way ANOVA with Tukey's tests (α = 0.05). The findings showed that incorporating graphene darkened the adhesive colour significantly and reduced translucency. As the graphene concentration reached 0.1 wt%, samples became opaque; yet, no adverse effect on degree of conversion was observed. The addition of graphene reduces optical transmission of lingual retainer adhesives; the effect increases with graphene concentration.

Properties of model E-glass fiber composites with varying matrix monomer ratios.

OBJECTIVE: To evaluate properties of fiber-reinforced-composites (FRC) containing Bis-EMA/UDMA monomers but identical dispersed phase (60% wt BaSi glass power +10% wt E-glass fibre). METHODS: A control (Group A), monomer mixture comprising 60% Bis-GMA, 30% TEGDMA, and 10% PMMA (typical FRC monomers) was used. The following monomer mass fractions were mixed: 50% bis-GMA plus 50% of different ratios of Bis-EMA+UDMA to produce consistent formulations (Groups B-E) of workable viscosities was also studied. Flexural strength (FS), fracture toughness (KIC), water sorption (SP), solubility (SL) and hygroscopic expansion (HE) were measured. FS and KIC specimens were stored for 1, 7 d, and 30 d in water at 37 °C. SP/SL specimens were water-immersed for 168d, weighed at intervals, then dried for 84 d at 37 °C. To analyze differences in FS, and KIC, a two-way ANOVA and Tukey post-hoc tests (α = 0.05) were conducted. For SP/SL, and HE, one-way ANOVA with subsequent Tukey post-hoc tests (α = 0.05) were utilized. RESULTS: FS and KIC for groups A, D, E decreased progressively after 1 d. Groups B and C (highest amounts of Bis-EMA) did not decrease significantly. The modified matrix composites performed significantly better than the control group for SP and HE. The control group outperformed the experimental composites only for SL with up to 250% higher SL for group E (6.9 µg/mm) but still below the maximum permissible threshold of 7.5 µg/mm. SIGNIFICANCE: EXPERIMENTAL: composites with highest amounts of Bis-EMA showed improved hydrolytic stability and overall enhancement in several clinically-relevant properties. This makes them potential candidates for alternative matrices to a semi-interpenetrating network in fiber-reinforced composites.

Effect of repair and surface treatments on the strength of digitally fabricated resin-based dental prostheses: A systematic review of in vitro studies.

OBJECTIVE: This review investigated the current literature pertaining to the repairability of computer-aided design-computer-aided manufacturing (CAD-CAM) milled and three-dimensional (3D) printed resin-based dental prostheses (RBDPs) as well as the appropriate surface treatment for each repair material that will produce adequate repair bond strength. DATA/SOURCES: PubMed, Web of Science, and Scopus databases were searched for published articles involving repair of CAD-CAM RBDPs between January 2010 and June 2023. Data were collected and analyzed to reveal the surface treatment effects, suggested repair materials, and strength of repaired RBDPs. STUDY SELECTION: Out of 164 retrieved titles, 11 studies were included, of which five investigated the repair of 3D-printed RBDPs, three investigated the repair of CAD-CAM milled resins, and three investigated both materials. Additionally, of the included studies, seven investigated denture base resins, three studied provisional restoration resins, and one evaluated 3D-printed intraoral splints. Various surface treatments were suggested, with air-abrasive methods being the most commonly used. Different materials for resin repair were proposed and used, including auto-polymerized, reline, and composite resins. For 3D-printed resins, repair with Bis-acrylic/Bis-GMA composites improved repair strength. CONCLUSION: Surface treatments positively affected the repair strength of conventional and milled RBDPs. However, challenges remain relevant to the repair of 3D-printed resins owing to composition mismatches and fabrication techniques. Therefore, further investigation is required to develop new 3D-printed resins. CLINICAL SIGNIFICANCE: CAD-CAM milled resins have satisfactory repair strength, which increases with surface treatment. The repair of 3D-printed resins has proven challenging even with surface treatments. However, composite resins are the materials of choice.

Green, pH-Sensitive, Highly Stretchable, and Hydrogen Bond-Dominated Ionogel for Wound Healing Activity.

Traditional hydrogel dressings generally have poor mechanical properties and stability when subjected to external stress due to the undesirable chain entanglement structure of their single valence bond compositions. Therefore, it is particularly important to develop a type of gel dressing with good mechanical strength, stability, and environment-friendly monitoring. In this work, a transparent, pH-sensitive, highly stretchable, and biocompatible anthocyanidin ionogel dressing was prepared, realizing green and accurate detection. Attributed to the antibacterial activity of the ionic liquid, the biocompatibility of the pectin, and the ability to scavenge free radicals of the anthocyanidin, the ionogel dressing exhibited excellent re-epithelialization in the 14 day wound healing process. Besides, changes in pH values monitoring of the ionogel over 3 days coincided with normal wound exudate. The obtained ionogel also showed good water retention, swelling properties, mechanical stretchability, and 5 week stability, illustrating great potential in wound dressings.

The impact of chitosan in experimental resin with different photoinitiator systems.

OBJECTIVE: to investigate the effect of different concentrations of chitosan added to experimental resins containing either BAPO or camphorquinone (CQ) as photoinitiators, regarding degree of conversion (DC), flexural strength (FS), flexural elastic modulus (E), Knoop microhardness (KHN), cytotoxicity, genotoxicity and antimicrobial activity. METHODS: Experimental resins with polymeric matrix of BisGMA and TEGDMA was added either 0.5 wt% BAPO or 0.5 wt% camphorquinone/0.2% amine along with and chitosan concentrations of 0.5%; 1.0% or 2.0%. Degree of conversion was measured using Fourier transformed infrared spectroscopy. Flexural strength and elastic modulus were obtained through three-point bending test and Knoop microhardness was measured in a microidenter. Direct cytotoxicity was performed in human keratinocytes and genotoxicity test was done in murine macrophages cells. Antimicrobial activity was acessed against Staphylococcus aureus and Streptococcus mutans through the inhibition halo. Data were analyzed using two-way ANOVA and Tukey teste (α = 0.05). RESULTS: The materials containing photoinitiator BAPO showed higher values of DC, FS, E, and KHN compared to resins with CQ. The addition of chitosan did not affect the properties of these materials. However, in resins containing CQ, the addition of chitosan improve these properties compared to control group. For the groups containing BAPO the chitosan reduced cytotoxicity and genotoxicity compared to materials with camphorquinone. The materials with 1.0% and 2.0% chitosan showed increased antibacterial activity in the materials containing BAPO as photoinitiator for both bacteria. SIGNIFICANCE: The alternative photoinitiator BAPO and chitosan can improve physical and biological properties of photoactivated resins when compared with the materials with photoinitiator camphorquinone.

The impact of Bis-GMA free and Bis-GMA containing resin composite as posterior restoration on marginal integrity: a randomized controlled clinical trial.

BACKGROUND: There have been concerns surrounding the utilization of Bis-GMA, a type of bisphenol A (BPA) derivative, within the dental industry. The aim of this study was to compare the performance of bulk fill Bis-GMA-free resin composite class II restorations in respect of its marginal integrity in comparison to bulk fill Bis-GMA-containing resin composite class II restorations over a 12-month period in a parallel clinical trial utilizing a split-mouth, double-blind, randomized strategy. METHODS: 20 patients participated in this study. Each patient has received one pair of class II posterior restorations, Bis-GMA-free (Admira fusion x-tra), and Bis-GMA containing (x-tra fil) on each side of the mouth (split-mouth strategy), (n = 40). The restorations' marginal integrity was evaluated based on Ryge's criteria (modified USPHS) at baseline (after 1 week), as well as 1 month, 3 months, 6 months, 9 months, and after 12 months of follow-up by two calibrated examiners. The statistical analyses utilizing the Friedman and Wilcoxon tests, the significance level was adjusted to 0.05. RESULTS: Following the 12-month period, all patients attended the recall visits to evaluate the restorations. The Wilcoxon signed-rank and Friedman tests, revealed that both types of bulk fill had 100% of Alpha (A) scores at baseline and after 1 month with no significant statistical differences. After 3, 6, 9, and 12 months, both tested bulk fill restorations showed Bravo (B) score with Bis-GMA free 10% and 5% for Bis-GMA containing with no statistically significant difference (p ≤ 0.05) for clinical marginal integrity parameter in USPHS criteria. CONCLUSIONS: Bis-GMA-free resin composites demonstrated satisfactory, marginal integrity compared with Bis-GMA-containing resin composites within 12 months. TRIAL REGISTRATION: The protocol of the current study was registered at www. CLINICALTRIALS: gov , with the identification number NCT05480852 on 29/07/2022. All procedures involving human participants were performed in accordance with the ethical standards of the Research Ethics Committee of the Faculty of Dentistry, Minia University, Egypt, under the approval number 419 on 27/06/2020.

Effect of elastomeric urethane monomer on physicochemical properties and shrinkage stress of resin composites.

This study aimed to evaluate the effect of an elastomeric urethane monomer (Exothane-24) in different concentrations on physicochemical properties, gap formation, and polymerization shrinkage stress of experimental resin composites. All experimental composites were prepared with 50 wt.% of Bis-GMA and 50 wt.% of TEGDMA, to which 0 wt.% (control), 10 wt.%, 20 wt.%, 30 wt.%, and 40 wt.% of Exothane-24 were added. Filler particles (65 wt.%) were then added to these resin matrixes. Ultimate tensile strength (UTS: n = 10), flexural strength (FS: n = 10), flexural modulus (FM: n = 10), hardness (H: n = 10), hardness reduction (HR: n = 10), degree of conversion (DC: n = 5), gap width (GW: n = 10), and polymerization shrinkage stress in Class I (SS-I: n = 10) and Class II (SS-II: n = 10) simulated configuration. All test data were analyzed using one-way ANOVA and Tukey's test (α = 0.05;  = 0.2). Exothane-24 in all concentrations decreased the H, HR, DC, GW, SS-I, and SS-II (p < 0.05) without affecting the UTS, and FS (p > 0.05). Reduction in FM was observed only in the Exothane 40% and 30% groups compared to the control (p < 0.05). Exothane-24 at concentrations 20% and 30% seems suitable since it reduced GW and polymerization SS without affecting the properties of the composite resins tested, except for H.

Degree of conversion and physicomechanical properties of newly developed flowable composite derived from rice husk using urethane dimethacrylate monomer.

This study evaluated the use of urethane dimethacrylate (UDMA) as a base monomer to prepare the newly developed flowable composite (FC) using nanohybrid silica derived from rice husk in comparison to bisphenol A-glycidyl methacrylate (Bis-GMA) on the degree of conversion and physicomechanical properties. The different loadings of base monomer to diluent monomer were used at the ratio of 40:60, 50:50, and 60:40. The bonding analysis confirmed the presence of nanohybrid silica in the newly developed FC. Independent t-test revealed a statistically significant increase in the degree of conversion, depth of cure and Vickers hardness of the UDMA-based FC, while surface roughness showed comparable results between the two base monomers. In conclusion, UDMA-based FC demonstrated superior performance with 60%-65% conversions, a significantly higher depth of cure exceeding 1 mm which complies with the Internal Standard of Organization 4049 (ISO 4049), and a substantial increase in Vickers hardness numbers compared to Bis-GMA-based FC, making UDMA a suitable alternative to Bis-GMA as a base monomer in the formulation of this newly developed FC derived from rice husk.

Transdentinal cytotoxicity of resin luting cements using the bovine and human dentin barrier.

STATEMENT OF PROBLEM: Based upon ethical questions and because of the difficulty of obtaining intact human teeth, researchers have used bovine teeth to assess the physical and mechanical properties of different dental materials. However, data from transdentinal cytotoxicity tests showing that the bovine dentin barrier is similar to the human dentin barrier is lacking. PURPOSE: The purpose of this in vitro study was to evaluate whether the bovine dentin barrier produces similar results to those obtained when the human dentin barrier is used to assess the transdentinal cytotoxicity of resin luting cements. MATERIAL AND METHODS: The number and diameter of dentinal tubules present in the human dentin barrier and bovine dentin barrier were evaluated and assessed with a t test (α=.05). After inserting the standardized dentin barriers into artificial pulp chambers, murine dental papilla-derived cells (MDPC-23) were seeded on the pulpal surface of the specimens, and the luting cements were applied to their occlusal surfaces. Then, the following groups were established for both human and bovine dentin barriers: no treatment (negative control); Single Bond Universal; RelyX Luting 2; RelyX U200; and RelyX Ultimate. After 24 hours, the viability (alamarBlue) and morphology (scanning electron microscopy) of the cells were evaluated with a 2-way analysis of variance and the Tukey honest significance test (α=.05). RESULTS: Dentinal tubules with larger diameters were observed in bovine dentin (P<.05), but the number of tubules was similar (P>.05). A reduction in viability and notable changes in the morphology of MDPC-23 cells occurred in the Single Bond Universal and RelyX Luting 2 groups in comparison with the negative control (P<.05). The RelyX U200 and RelyX Ultimate groups were statistically similar to the negative control (P>.05). No difference was found in cytotoxicity when the same luting cement was applied on human or bovine dentin barriers (P>.05). CONCLUSIONS: For transdentinal cytotoxicity tests of resin luting cements, the bovine dentin barrier proved similar results to the human dentin barrier.

Shear Bond Strength and Microleakage of Fissure Sealant to Contaminated and Non-Contaminated Enamel: A Systematic Review and Meta-Analysis of In Vitro Studies.

Purpose: The purpose of this study was to review the in vitro literature on shear bond strength (SBS) and microleakage of pit and fissure sealant materials in contaminated (water, human, or artificial saliva) and non-contaminated conditions. Methods: PubMed®, Web of Science™, Scopus®, Embase™, and Cochrane Library databases were used as data sources. Of the 974 studies identified, 56 were considered eligible for full-text screening and 32 were selected for data extraction. Results: The meta-analysis demonstrated that contaminated conditions decreased the SBS of the sealants by 4.33 MPa. In the contaminated subgroup analysis, both unfilled (Clinpro™, 3M™) and filled (FluroShield®, Dentsply) resin-based sealants achieved a similar SBS (P=0.82). Regarding the outcome measurements, extensive methodological heterogeneity was found among the studies for SBS measurements (I 2 equals greater than or equal to 84 percent; P<0.001), whereas homogeneity was found for microleakage (I 2 equals 84 percent; P=0.85). When evaluating resin-based sealants, the level of microleakage in the contaminated and non- contaminated groups was not significantly different (P=0.1). Conclusion: Surface contamination decreases the bond strength between contaminated enamel and both unfilled and filled resin-based sealants, which affects the clinical effectiveness of sealants.