Search Results (35)

Occlusal splints are a type of intraoral appliance that are widely used for the management of temporomandibular disorders and bruxism, yet limited evidence exists regarding the comparative effects of combined aging on conventional and digitally manufactured materials. This in vitro study evaluated the influence of thermal and mechanical aging on the flexural properties of three materials commonly used for the manufacturing of occlusal devices: self-curing poly(methyl methacrylate) (PMMA, control), light-cured urethane dimethacrylate (UDMA)-based resin, and stereolithography (SLA)-printed photopolymer. Seventy-two standardized specimens (n = 24 per material; 64 × 10 × 3.3 mm) were fabricated, then randomly allocated to three groups (n = 8): control, thermocycling (10,000 cycles, 5 °C/55 °C), and combined thermocycling with mechanical loading (1000 cycles). Flexural strength and modulus were determined by three-point bending tests and analyzed using a two-way analysis of variance (ANOVA) with Tukey’s post hoc test (α = 0.05). Thermocycling significantly reduced flexural strength in PMMA (65.19 ± 6.68 to 57.94 ± 7.15 MPa) and SLA (67.67 ± 1.54 to 59.37 ± 8.80 MPa) groups (p < 0.05), while UDMA group (45.489 ± 3.905 to 43.123 ± 4.367 MPa) demonstrated no significant changes (p ≥ 0.05). UDMA exhibited substantially and significantly lower flexural properties compared to PMMA and SLA across all conditions (p < 0.0001). Thermal aging slightly compromises the mechanical properties of PMMA and SLA-printed materials, whereas UDMA-based resins exhibit good aging resistance but considerably lower initial values. While UDMA-based resin showed superior aging resistance, its lower baseline mechanical properties may limit its application in high-stress clinical scenarios compared to PMMA and SLA-printed materials. Material selection should consider both initial properties and long-term environmental changes. Full article

Background: Clear aligners have become a common alternative to fixed appliances for tooth movement, and thermoplastic retainers hold the outcome. The prolonged intraoral contact of these devices has made the materials a focus of biocompatibility research. Objectives: This paper aims to summarize laboratory evidence on the biocompatibility of clear aligners and thermoplastic retainers. Materials included thermoformed polyethylene terephthalate glycol-modified (PETG), multilayer polyurethane, and directly printed resins. Primary outcomes were cytotoxicity, endocrine activity, and chemical or particle release. Methods: We systematically searched PubMed, the Cochrane Library, and Google Scholar through 31 May 2025, and we followed the PRISMA 2020 statement (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). We applied predefined eligibility criteria. Two reviewers screened records and extracted data in duplicate, including study design, extraction conditions, surface-area-to-volume ratio (SA/V), cell models, endpoints, and analytical sensitivity as the limit of detection (LOD) and limit of quantification (LOQ). We assessed the risk of bias across seven domains and graded certainty by outcome. We did not register a protocol prospectively. Results: Seventeen studies met the inclusion criteria. Materials spanned multilayer polyurethanes (SmartTrack, Clarity), PETG sheets (Essix ACE, Duran), and directly printed resins (Graphy TC-85DAC); a subset tested zinc-oxide (ZnO) nanoparticle coatings. Typical extractions immersed 0.1–1 g of material in cell-culture medium or artificial saliva at 37 °C for 24 h to 30 days. Cell viability usually remained ≥80%. Mild cytotoxicity (about 60–70% viability) appeared with harsher extractions, extended soaks, or an inadequate post-curing of printed parts. The estrogen-sensitive proliferation assay (E-Screen) returned negative results. In saliva-like media, bisphenol A (BPA) and related leachables were undetectable or in the low ng/mL range. In printed resins, urethane dimethacrylate (UDMA) sometimes appeared in water extracts, and amounts varied with curing quality. Evidence for chemical leaching and endocrine outcomes is sparse. We found no eligible in vitro study that quantified particle or microplastic release while also measuring a biological endpoint; we discuss particle findings from mechanical wear simulations only as the external context. Limitations: The evidence base is limited to in vitro studies. Many reports incompletely described extraction ratios and processing parameters. Risk of bias and certainty: Most studies used appropriate cell models and controls, but the reporting of surface-area-to-volume ratios, LOD/LOQ, and detailed post-processing parameters was often incomplete. Sample sizes were small, and dynamic wear or enzymatic conditions were uncommon. The overall risk of bias was moderate, and the certainty of evidence was low to moderate due to heterogeneity and in vitro indirectness. Conclusions: Under standard laboratory conditions, clear aligners and thermoplastic retainers show a favorable biocompatibility profile. For printed resins, outcomes depend mainly on processing quality, especially thorough washing and appropriate light-curing parameters. To improve comparability and support clinical translation, we recommend harmonized test protocols, transparent reporting, interlaboratory ring trials, and targeted clinical biomonitoring. Full article

This study aimed to assess how different resin matrix formulations affect the fatigue resistance of resin dental composites. Model dental composites were formulated using six distinct monomer mixtures: two Bis-GMA (bisphenol A-glycidyl methacrylate):TEGDMA (triethylene glycol dimethacrylate) (60:40 and 80:20 mole%), two UDMA (urethane dimethacrylate):TEGDMA (60:40 and 80:20 mole%), one Bis-GMA:UDMA:TEGDMA (35:35:30 mole%), and one Fit852:UDMA:TEGDMA (35:35:30 mole%). Cyclic fatigue resistance (CFR) of the resin composites was measured in a biaxial test mode using staircase analysis. Additional evaluations included biaxial flexural strength (BFS), degree of conversion (DC), water sorption (WS), and viscoelastic properties of the unfilled resins, such as the storage modulus (E′), loss modulus (E″), tan δ (E″/E′), and stiffness (k′). Data were subjected to one-way ANOVA with Tukey post hoc analyses. Pearson correlation and stepwise regression analyses were conducted to examine the relationships among variables. The UT6040 model composite exhibited the highest CFR (82.61 ± 8.83 MPa), significantly outperforming other formulations. Tan δ of the resin matrix showed the strongest correlation with CFR (r = 0.974), and was also shown to be the most influential predictor for the CFR of the particulate composites. The composition of the resin matrix has a significant impact on the CFR of dental composites. Among the properties evaluated, the viscoelastic parameter tan δ emerged as a strong and reliable predictor of CFR, emphasizing the importance of targeting viscoelastic behavior in the design of dental composite formulations. Full article

Tooth root caries account for 10.1% of all dental caries in the USA. This study developed a multifunctional resin coating with calcium (Ca) and phosphate (P) ion release and antibacterial properties to combat root caries. The effects of nano-sized amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM) on mechanical, physical, and antibacterial properties against Streptococcus mutans, and cytotoxicity on dental pulp stem cells and gingival fibroblasts were evaluated. A coating resin combining urethane dimethacrylate (UDMA), triethylene glycol divinylbenzyl ether (TEGDVBE), DMAHDM, and NACP was synthesized and compared with Seal&Protect and Vanish XT. Experimental groups (UV + 5% DMAHDM + 10%, 15%, and 20% NACP) showed flexural strength (70.9 ± 8.0 to 81.1 ± 6.0) MPa, significantly higher than Seal&Protect (48.2 ± 7.2) MPa (p < 0.05) and comparable to Vanish XT (70.2 ± 13.6) MPa, (p > 0.05). Elastic modulus (2.2 to 3.3) GPa was lower than Vanish XT (9.4 ± 1.1) GPa (p < 0.05). Experimental groups showed an 8 log CFU reduction, 96% reduction in metabolic activity and 87% in lactic acid production, and increased Ca (1.25 ± 0.03) mmol/L and P (0.8 ± 0.001) mmol/L release over 35 days. Cytotoxicity for experimental groups against dental pulp stem cells and human gingival fibroblast was low and matched those of commercial controls already used in clinic. The resin demonstrated potent antibacterial properties, high ion release, low cytotoxicity, and maintained physical and mechanical integrity, offering potential to prevent root caries formation and progression. Full article

This study was conducted to evaluate the material properties of polymer-infiltrated zinc oxide networks (PICN) and the effect of using a phosphate monomer-containing primer applied before polymer infiltration. A total of 148 ZnO-network (zinc oxide) specimens were produced: n = 74 were treated with a primer before polymer infiltration and light curing, while the remaining specimens were untreated. Each group was divided into two subgroups (n = 37) based on the infiltrating polymer: UDMA (aliphatic urethane-dimethacrylates)-TEGDMA (triethylene glycol-dimethacrylate) or BisGMA (bisphenol A-glycidyl-methacrylate)-TEGDMA. Additionally, n = 7 specimens of each polymer type were prepared for comparison. Then, biaxial flexural strength was measured before and after 150 days of water storage at 37 °C, including 37,500 thermal cycles (5 °C to 55 °C). The Vickers hardness, surface roughness, and water absorption at 37 °C were also tested. The initial biaxial flexural strength was reduced in the ZnO network specimens compared to in the pure polymers. Primer application improved the flexural strength, though the strength of BisGMA-TEGDMA significantly decreased after water storage. The ZnO network increased hardness, and the polymer-infiltrated networks showed higher roughness post-grinding and absorbed less water than the pure polymer groups. The ZnO networks did not improve the flexural strength over that of the pure polymers. However, the primer’s positive impact and the network’s long-term stability suggest potential if the network structure can be modified to contain thicker, more stable branches. Full article

Dental caries are treated using dental composite restorative materials (DCRM). However, commercial DCRMs lack antibacterial activity. This research aimed to analyze the in vitro antibacterial activity of a series of copolymers consisting of a urethane–dimethacrylate monomer (UDMA), bisphenol A glycerolate dimethacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA) and urethane–dimethacrylate monomer with two quaternary ammonium groups and a 1,3-bis(1-isocyanate-1-methylethyl)benzene core (QAn+TMXDI, where n = 8, 10, or 12 is the number of carbon atoms in the N-alkyl substituent). QAn+TMXDI contents in copolymers were 20 and 40 wt.%. The results of the Staphylococcus aureus and Escherichia coli adhesion test demonstrated that the logCFU/mL decreased as the length of the N-alkyl chain decreased and QAn+TMXDI content increased. The copolymers of QA8+TMXDI 40 wt.%, Bis-GMA 40 wt.%, and TEGDMA 20 wt.% showed the highest antibacterial activity, with a logCFU/mL of 2.39 for S. aureus and no viable E. coli cells. Full article

Repairing or reconstructing significant bone defects is typically challenging. In the present study, two composite cements were used as scaffolds in a sub-critical femoral defect in rats. A control group and two experimental batches were used to compare the outcomes. This research aimed to investigate the osteogenic potential and toxicological tolerance of the bioproducts through histopathology and computed tomography imaging analysis at 14, 28, 56, and 90 days post-implantation. The biomaterials used in the investigation consisted of a 65% bioactive salinized inorganic filler and a 25% weight organic matrix. The organic part of the biomaterial was composed of Bis-GMA (bisphenol A-glycidyl methacrylate), UDMA (urethane dimethacrylate), HEMA (2-Hydroxyethyl methacrylate), and TEGDMA (triethylene glycol dimethacrylate), while the inorganic filler was composed of silica, barium glass, hydroxyapatite, and fluor aluminosilicate glass. The first findings of this research are encouraging, revealing that there is a slight difference between the groups treated with biomaterials, but it might be an effective approach for managing bone abnormalities. Material C1 exhibited a faster bone defect healing time compared to material C2, where bone fractures occurred in some individuals. It is unclear if the fractures were caused by the presence of the biomaterial C2 or whether additional variables were to blame. By the end of the research, the mice appeared to tolerate the biomaterials without exhibiting any inflammatory or rejection responses. Full article

Root caries caused by cariogenic bacteria are a burden on a large number of individuals worldwide, especially the elderly. Applying a protective coating to exposed root surfaces has the potential to inhibit the development of caries, thus preserving natural teeth. This study aimed to develop a novel antibacterial coating to combat root caries and evaluate its effectiveness using the antibacterial monomer dimethylaminohexadecyl methacrylate (DMAHDM). DMAHDM was synthesized and incorporated into a resin consisting of 55.8% urethane dimethacrylate (UDMA) and 44.2% TEG-DVBE (UV) at a 10% mass fraction of glass filler. Multiple concentrations of DMAHDM were tested for their impact on the resin’s mechanical and physical properties. S. mutans biofilms grown on resin disks were analyzed for antibacterial efficacy. Cytotoxicity was assessed against human gingival fibroblasts (HGFs). The results showed an 8-log reduction in colony-forming units (CFUs) against S. mutans biofilm (mean ± sd; n = 6) (p < 0.05) when 5% DMAHDM was incorporated into the UV resin. There was a 90% reduction in metabolic activity and lactic acid production. A low level of cytotoxicity against HGF was observed without compromising the physical and mechanical properties of the resin. This coating material demonstrated promising physical properties, potent antibacterial effects, and low toxicity, suggesting its potential to protect exposed roots from caries in various dental procedures and among elderly individuals with gingival recession. Full article

In this study, two novel quaternary ammonium urethane-dimethacrylates (QAUDMAs) were designed for potential use as comonomers in antibacterial dental composite restorative materials. QAUDMAs were synthesized via the reaction of 1,3-bis(1-isocyanato-1-methylethyl)benzene with 2-(methacryloyloxy)ethyl-2-decylhydroxyethylmethylammonium bromide (QA10+TMXDI) and 2-(methacryloyloxy)ethyl-2-dodecylhydroxyethylmethylammonium bromide (QA12+TMXDI). Their compositions with common dental dimethacrylates comprising QAUDMA 20 wt.%, urethane-dimethacrylate monomer (UDMA) 20 wt.%, bisphenol A glycerolate dimethacrylate (Bis-GMA) 40 wt.%, and triethylene glycol dimethacrylate (TEGDMA) 20 wt.%, were photocured. The achieved copolymers were characterized for their physicochemical and mechanical properties, including their degree of conversion (DC), glass transition temperature (T_g), polymerization shrinkage (S), water contact angle (WCA), flexural modulus (E), flexural strength (FS), hardness (HB), water sorption (WS), and water leachability (WL). The antibacterial activity of the copolymers was characterized by the minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) against Staphylococcus aureus and Escherichia coli. The achieved results were compared to the properties of a typical dental copolymer comprising UDMA 40 wt.%, Bis-GMA 40 wt.%, and TEGDMA 20 wt.%. The introduction of QAUDMAs did not deteriorate physicochemical and mechanical properties. The WS and WL increased; however, they were still satisfactory. The copolymer comprising QA10+TMXDI showed a higher antibacterial effect than that comprising QA12+TMXDI and that of the reference copolymer. Full article

A low ratio of polymerization is a major problem in resin-based composites. In this paper, the plasmonic effect of gold-covered silica nanoparticles on the physicochemical and mechanical properties of bisphenol A diglycidyl dimethacrylate (Bis-GMA), triethylene glycol dimethacrylate (TEGDMA) and urethane dimethacrylate (UDMA) green light-photopolymerizable dental resin was investigated at an intensity of 1.4 mW/cm² for 40 s. Transmission electron microscopy (TEM) showed silica of about 350 nm covered with 12–15 nm gold nanoparticles (Au NPs) at 100% nominal coverage. Five different concentrations of bare and patchy silica particles were used; in the latter composite, the calculated Au wt% were 0.0052 wt%, 0.0104 wt%, 0.0208 wt%, 0.04160 wt%, and 0.0823 wt%. The plasmon peak of patchy silica-filled nanocomposite overlapped with the absorption of Irgacure 784 photoinitiator and green LED light emission peak. The effect of plasmon-enhanced polymerization achieved with green light illumination was analyzed using diametral tensile strength (DTS), differential scanning calorimetry (DSC), surface plasmon resonance imaging (SPRi), and degree of conversion (DC) based on Raman spectroscopy. The values of the Au NP with 0.0208 wt% was found to be maximum in all the measured data. Based on our result, it can be concluded that the application of patchy silica particles in dental resin can improve the polymerization ratio and the mechanical parameters of the composite. Full article

This study analyse the type of release kinetic of specific monomers from dental resin composites containing various fluoride-doped calcium phosphates. The release behavior of urethane dimethacrylate (UDMA), ethoxylated bisphenol-A dimethacrylate (bis-EMA) and 1.6-hexanediol ethoxylate diacrylate (HEDA) was evaluated over a period of 35 days. Two tailored calcium phosphates doped with different concentrations of fluoride salts (VS10% and VS20%) were prepared and incorporated in the dimethacrylate matrix at various concentrations to generate a range of experimental composites. The release kinetics were characterized using mathematical models such as zero-order, first-order, Peppas and Higuchi models. The results showed that the first-order model best described the release kinetics. UDMA and HEDA exhibited significant differences in release compared to bis-EMA from day 1, while no significant differences were observed between UDMA and HEDA, except on day 35, when UDMA exhibited a higher release rate than HEDA. When comparing the release of each monomer, VS20-R20% had the highest total release percentage, with 3.10 ± 0.25%, whereas the composite VS10-R5% showed the lowest release percentage, with a total of 1.66 ± 0.08%. The release kinetics were influenced by the composition of the resin composites and the presence of calcium fluoride and sodium fluoride in the calcium phosphate played a role in the maximum amounts of monomer released. In conclusion, the release of monomers from the tested resin composites followed a first-order kinetic behaviour, with an initial rapid release that decreased over time. The composition of the resin monomers and the presence of fluoride salts influenced the release kinetics. The VS10-R5% and VS10-R10% resin composites exhibited the lowest total monomer release, suggesting its potential favourable composition with reduced monomer elution. These findings contribute to understanding the release behavior of dental resin composites and provide insights for the development of resin-based bioactive dental materials. Full article

Three-dimensional (3D) printing polymers such as urethane dimethacrylate (UDMA) and ethoxylated bisphenol A dimethacrylate (Bis-EMA) are typically used in definitive prosthesis and require surface treatments before bonding. However, surface treatment and adhesion conditions often affect long-term use. Herein, polymers were divided into Groups 1 and 2 for the UDMA and Bis-EMA components, respectively. The shear bond strength (SBS) between two types of 3D printing resins and resin cements was measured using Rely X Ultimate Cement and Rely X U200, according to adhesion conditions such as single bond universal (SBU) and airborne-particle abrasion (APA) treatments. Thermocycling was performed to evaluate the long-term stability. Sample surface changes were observed using a scanning electron microscope and surface roughness measuring instrument. The effect of interaction between the resin material and adhesion conditions on the SBS was analyzed via a two-way analysis of variance. The optimal adhesion condition for Group 1 was achieved when U200 was used after APA and SBU, whereas Group 2 was not significantly affected by the adhesion conditions. After thermocycling, the SBS significantly decreased in Group 1 without APA treatment and in the entire Group 2. Additionally, porosity, along with increased roughness, was observed on both material surfaces after APA. Full article

Due to the questionable durability of dental restorations, there is a need to increase the lifetime of composite restoration. The present study used diethylene glycol monomethacrylate/4,4′-methylenebis(cyclohexyl isocyanate) (DEGMMA/CHMDI), diethylene glycol monomethacrylate/isophorone diisocyanate (DEGMMA/IPDI) monomers, and bis(2,6-diisopropylphenyl)carbodiimide (CHINOX SA-1) as modifiers of a polymer matrix (40 wt% urethane dimethacrylate (UDMA), 40 wt% bisphenol A ethoxylateddimethacrylate (bis-EMA), and 20 wt% triethyleneglycol dimethacrylate (TEGDMA)). Flexural strength (FS), diametral tensile strength (DTS), hardness (HV), sorption, and solubility were determined. To assess hydrolytic stability, the materials were tested before and after two aging methods (I-7500 cycles, 5 °C and 55 °C, water and 7 days, 60 °C, 0.1 M NaOH; II-5 days, 55 °C, water and 7 days, 60 °C, 0.1 M NaOH). The aging protocol resulted in no noticeable change (median values were the same as or higher than the control value) or a decrease in the DTS value from 4 to 28%, and a decrease in the FS value by 2 to 14%. The hardness values after aging were more than 60% lower than those of the controls. The used additives did not improve the initial (control) properties of the composite material. The addition of CHINOX SA-1 improved the hydrolytic stability of composites based on UDMA/bis-EMA/TEGDMA monomers, which could potentially extend the service life of the modified material. Extended studies are needed to confirm the possible use of CHINOX SA-1 as an antihydrolysis agent in dental composites. Full article

An accurate and dimensionally stable trial denture base is required for a successful denture. The aim of this in vitro study was to assess the dimensional stability of a light-activated urethane dimethacrylate (UDMA) visible light cure (VLC) denture base with three fabrication techniques and different curing cycles. Forty-five VLC denture base samples were divided evenly into three groups. Group A used a conventional fabrication technique with a curing cycle of 5 min. Group B used a modified fabrication technique with two 4-min curing cycles. Group C used a multi-step fabrication technique with three curing cycles (4 min, plus 4 min, plus 2 min). The samples were sectioned and observed under a stereomicroscope to measure the discrepancy between the sample and the master cast. The mean dimensional discrepancy (mm) at the molar region at mid-palate, after 24 h in Group A, B and C was 0.790 mm, 0.741 mm and 0.379 mm, respectively; at the right ridge crest, it was 0.567, 0.408 and 0.185, while at the left ridge crest it was 0.475, 0.331 and 0.125, respectively. Statistical analysis showed significantly different dimensional discrepancies among the groups at all three sites; right ridge crest (F = 93.54, p < 0.001), left ridge crest (F = 105.96, p < 0.001) and mid-palate (F = 125.53, p < 0.001). Within the limitations of this laboratory study, it can be concluded that the denture base using a multi-step fabrication technique with three curing cycles provides better adaptation than the conventional technique. The significance of the study is that clinicians should consider performing denture base fabrication using a multi-step technique to enhance adaptation and hence the stability of the dentures for patients. Full article

This study aimed to elucidate the physicochemical properties of copolymers comprising 40 wt.% bisphenol A glycerolate dimethacrylate (Bis-GMA), 40 wt.% quaternary ammonium urethane-dimethacrylate analogues (QAUDMA-m, where m corresponds to the number of carbon atoms in the N-alkyl substituent), and 20 wt.% triethylene glycol dimethacrylate (TEGDMA) copolymers (BG:QAm:TEGs). The BG:QAm:TEG liquid monomer compositions and reference compositions (40 wt.% Bis-GMA, 40 wt.% urethane-dimethacrylate (UDMA), 20 wt.% TEGDMA (BG:UD:TEG) and 60 wt.% Bis-GMA, 40 wt.% TEGDMA (BG:TEG)) were characterized in terms of their refractive index (RI) and monomer glass transition temperature (Tg_m) and then photocured. The resulting copolymers were characterized in terms of the polymer glass transition temperature (Tg_p), experimental polymerization shrinkage (S_e), water contact angle (WCA), water sorption (WS), and water solubility (SL). The prepared BG:QAm:TEG liquid monomer compositions had RI in the range 1.4997–1.5129, and Tg_m in the range −52.22 to −42.12 °C. The BG:QAm:TEG copolymers had Tg_p ranging from 42.21 to 50.81 °C, S_e ranging from 5.08 to 6.40%, WCA ranging from 81.41 to 99.53°, WS ranging from 25.94 to 68.27 µg/mm³, and SL ranging from 5.15 to 5.58 µg/mm³. Almost all of the developed BG:QAm:TEGs fulfilled the requirements for dental materials (except BG:QA8:TEG and BG:QA10:TEG, whose WS values exceeded the 40 µg/mm³ limit). Full article