Strength Of Resin Research Articles

Flexural Strength, Fatigue Behavior, and Microhardness of Three-Dimensional (3D)-Printed Resin Material for Indirect Restorations: A Systematic Review

The purpose of this systematic review was to evaluate three mechanical properties of 3D-printed resins for indirect restorations according to published scientific evidence. This systematic review was conducted according to the PRISMA statement (preferred reporting elements for systematic reviews and meta-analyses). The search was performed by two investigators, (DD) and (VB), and a third (AC) resolved disagreements. Articles were searched in four digital databases: PubMed, EBSCO, Lilacs, and Science Direct, starting on 18 February 2024. As 3D-printing technology has shown significant advances in the last 5 years, the review was conducted with a publication year range between 2019 and 2024, in English language and included in vitro articles on the mechanical properties of flexural strength, fatigue behavior, and microhardness of 3D-printed materials for temporary or definitive restorations. MeSH terms and free terms were used for the titles and abstracts of each article. Finally, the QUIN tool was used to assess the risk of bias. In the main search, 227 articles were found, of which 20 duplicates were excluded, leaving 207 articles; of these, titles and abstracts were read, and 181 that did not meet the eligibility criteria were eliminated; of the remaining 26 articles, 1 article was eliminated for not presenting quantitative results. Regarding publication bias, 6 of the 25 articles had a low risk of bias, 18 had a medium risk of bias, and 1 had a high risk of bias. It may be concluded that 3D-printed resins have lower flexural strength, fatigue behavior, and microhardness than other resin types used for the fabrication of temporary and permanent restorations. The type of 3D printer and polymerization time could be factors that significantly affect the flexural strength, fatigue behavior and microhardness of 3D-printed resins. Based on existing evidence, it should be considered that additive technology has promising future prospects for temporary and permanent dental restorations.

The role of aging and various surface preparation methods in the repair of nanohybrid composites

BackgroundRepairing composite resins is a less invasive alternative to complete restoration replacement. To achieve a successful bond between the existing and newly applied composite materials, various surface preparation methods, such as sandblasting and acid etching, have been explored. The aim of the study was to evaluate the effect of different surface treatments on the repair bond strength of a universal nanohybrid composite resin restorative material before and after thermal aging, by utilizing a micro-shear bond strength (µSBS) test.MethodsFor the micro-shear bond strength test, a total of 120 cylindrical (3mmX2mm) nanohybrid resin based composite specimens were prepared. The prepared specimens were divided into three groups (n = 40/per group) based on surface treatment methods: a non-aged group, 10,000 thermal cycle aging and 50,000 thermal cycle aging. The aged and non-aged specimens were further divided into four groups according to adhesive application modes and surface pretreatment methods: 1.universal adhesive/self-etch mode, 2.aluminum oxide sandblasting + universal adhesive/self-etch mode, 3.universal adhesive/etch-and-rinse mode, 4.aluminum oxide sandblasting + universal adhesive/etch-and-rinse mode. Subsequently, 0.8mmX2mm disc shape light cure resin based composite specimens were applied with a direct placement technique on the treated surfaces of all samples for repair. µSBS test was performed using a universal testing machine at a crosshead speed of 1 mm/min. Kruskal-Wallis and Mann-Whitney tests were performed for statistical analysis.ResultsThe µSBS values of the non-aged group were higher than those of the 10,000 and 50,000 thermal cycle groups, with no significant differences within the non-aged subgroup (p > 0.05). In the aged groups, significant differences were observed between adhesive application modes and surface treatments. Specifically, the etch-and-rinse mode showed higher bond strengths than the self-etch mode after 50,000 thermal cycles (p < 0.05). Sandblasting combined with universal adhesive (self-etch mode) improved bond strength, especially in the 10,000 thermal cycle group (p < 0.05).ConclusionAging reduced the bond strength of composite resin repairs, with the etch-and-rinse mode outperforming the self-etch mode in aged specimens. Sandblasting alone did not enhance bond strength. These findings highlight the importance of considering aging and adhesive strategies to optimize repair outcomes, with further research needed on long-term durability.

Zr-doped mesoporous silica (Zr-MSS) for improved mechanical stability and biocompatibility of dental composite resins.

Mesoporous silica particles are of great interest in the field of dental composites as functional inorganic fillers due to their unique interconnected pores which can form micromechanical interlocking at the filler-resin interfaces. However, the degradation of mesoporous silica is fast in wet environments, leading to the poor mechanical stability of dental composites. Here, we synthesized Zr-doped mesoporous silica spheres (Zr-MSS) to increase the chemical stability of the particles. The particles were formulated with dental resins (Bisphenol A glycerolate dimethacrylate/triethylene glycol dimethacrylate, 50/50, wt%) to evaluate the performance of dental composites. Dental composites filled with different amount of Zr-MSS (15, 20, 25 and 30wt%) and their bimodal fillers with nonporous silica spheres (NSS) at a total filler loading of 60wt% (mass ratios of Zr-MSS: NSS=10:50) were prepared. Neat resin matrix and samples filled with mesoporous silica spheres (MSS) were used as control. The results showed that the decrease percentage of flexural strength of dental resins with Zr-MSS was the lowest, which was between 3.4 and 6.8%. It was between 20.8 and 35.5% for those with MSS. Further studies revealed that the incorporation of Zr into mesoporous fillers did not affect their light curing ability of dental composites. Not only that, cell proliferation on the dental composites with Zr-MSS was promoted, suggesting improved biocompatibility of the restorations. These indicated that the prepared Zr-MSS would be promising functional fillers for dental composite resins.

Curing modes affects micro-tensile bond strength and durability of dual curing resin cements to dentin

BackgroundTo evaluate the effects of curing modes on the micro-tensile bond strength and durability of 6 different dual curing resin cements to dentin.Methods84 human molars were divided into 7 groups (n = 12), and were further distributed into two subgroups according to the two curing modes: light-curing (L) and self-curing (D) (n = 6). The 6 dual-cured resin cements were: DU (Duolink, Bisco), TC (TheraCem, Bisco), MS (Multilink Speed, Ivoclar), N3 (Nexus 3 Universal, Kerr), R2 (RelyX U200, 3M) and RU (RelyX Ultimate, 3M). The universal adhesives were: All Bond Universal (Bisco); Adhesive Universal Vivapen (Ivoclar); Optibond Versa Adhesive (Kerr); Scotch Bond Universal Adhesive (3M). RU was placed directly on processed adhesive layer without light-curing, set as group 7. Micro-tensile bond strength test was carried out after 37°C water storage for 24 h, 3 months and 6 months, respectively. Three-way ANOVA and Games-Howell test were performed by SPSS 19.0 (α = 0.05).ResultsThe Three-way ANOVA indicated that bonding performance was significantly affected by curing mode (p = 0.000, F = 1,237.510), resin cement (p = 0.000, F = 59.507) and storage time (p = 0.000, F = 97.888). The interaction of these three factors was significant (p = 0.017, F = 2.071).ConclusionThe bonding strength and durability of dual curing resin cements were significantly improved by light-curing process. In addition, the bonding strength of resin cements with different experimental condition was material depended. Among all tested resin cements, N3 exhibits the most favorable outcomes.Clinical RelevanceA dual curing procedure is recommended in clinical application. Among all tested resin cements, N3 exhibits the most favorable outcomes.

Nonconventional phosphorus-based tertiary amine curing agent enabling the high fire safety, outstanding tensile strength and high glass transition temperature of epoxy resin

Nonconventional phosphorus-based tertiary amine curing agent enabling the high fire safety, outstanding tensile strength and high glass transition temperature of epoxy resin

Evaluation of mechanical properties and ion-releasing of 3D printing resins containing S-PRG filler: A preliminary study.

This study aimed to evaluate ionic release, flexural strength and water absorption of UDMA resins containing 0-30 wt% surface pre-reacted glass-ionomer (S-PRG) filler fabricated by a DLP 3D printer. Release of Al, B, Na, Sr and F ions were measured by inductively coupled plasma (ICP) and an ion meter. Flexural strength test and water absorption measurements were performed according to the International Organization for Standardization (ISO) 4049 standard and ISO 1567 standard, respectively. Sr ions were released the most, followed by F, B, Na and Al ions. The highest flexural strength was recorded with the S-PRG filler amount 0 wt%, followed by the S-PRG filler amounts 30, 20 and 10 wt%. Water absorption after one week was below the 32 µg/mm3 mark specified by ISO 1567. The release of ions was confirmed using UDMA-based photopolymerized resin containing S-PRG filler. Furthermore, the results suggest that this resin could be used for provisional restoration.

Mechanical Properties and Degree of Conversion of a Novel 3D-Printing Model Resin.

The aim of this study was to evaluate the mechanical properties and degree of conversion of a novel 3D-printing model resin and compare it to eight commercially available model resins. An experimental resin formulated by our proprietary resin technology along with DentaModel, NextDent 2, KeyModel Ultra, Rodin Model, Die and Model 2, DMR III, LCD Grey, and Grey Resin were used in this study. Parallelepiped specimens (2 × 2 × 25 mm, n = 5) were printed and measured for their flexural strength (FS), flexural modulus (FM), and modulus of resilience (MR) in accordance with ISO-4049. Dumbbell-shaped specimens (Type V, n = 5) were printed to test tensile strength (TS) and elongation according to ASTM-D638. Barcol hardness (BH) was measured based on ASTM D2583 using broken tensile strength specimens. Izod-type test specimens (3.2 × 12.7 × 63.5 mm, n = 10) were printed, notched, and determined for impact strength according to ASTM D256-10. The degree of conversion was measured using FTIR (n = 5). Data were analyzed using one-way ANOVA and post hoc Tukey tests (p ≤ 0.05). The experimental resin exhibited a similar or significantly greater flexural strength (88.8 MPa), modulus of resilience (2.13 MPa), tensile strength (54.4 MPa), and hardness (82.9) than most model resins (FS 62.6-90.1 MPa, MR 1.37-2.0 MPa, TS 36.3-54.6 MPa, BH 66.1-83.7). The elongation (6.2%) and impact strength (14.2 J/m) of the experimental resin are statistically the same as those of most resins (3.0-7.5%, 13.8-16.4 J/m). However, the experimental resin has a significantly lower flexural modulus (1.97 GPa) than most resins (2.18-3.03 GPa). The experimental resin exhibited a significantly higher degree of conversion (66.58%) than most resins (1.11-62.34%) for 40 s of light curing; however, a similar or higher value (84.87%) than most resins (72.27-82.51%) was obtained for 3D-printed objects. The newly formulated 3D-printing model resin exhibited adequate mechanical properties and degree of conversion, which is comparable to the commercially available 3D-printing model resin materials. The new 3D-printing model resin can be used for modeling applications in restoration, orthodontics, implants, and other cases.

Comparative evaluation of flexural strength of conventional heat polymerized denture base resin reinforced with non-silanized and silanized aluminum oxide powder- An in vitro study

Although denture base acrylic resins have been used since many decades, the problem of facture of denture base still remains. Many researchers have tried to reinforce the denture base by addition of metallic oxide nanoparticles. Silanization of such nanoparticles is recommended as it improves the bond between fillers and added nanoparticles. To evaluate and compare the flexural strength (FS) of heat polymerized acrylic resin denture base material reinforced with 2.5 wt % of non-silanized and silanized aluminum oxide powder (AlO). : Seventy-five specimens of heat polymerized acrylic resin were fabricated. The specimens were divided into three groups (n = 75) coded as Group N (non-silanized AlO), Group S (silanized AlO) and Group C (Control). The specimens of the remaining two groups were reinforced with 2.5 wt % of non-silanized and silanized AlO. The flexural strength of the specimens was measured using 3-point bending test in a Universal Testing Machine. Data analyses using analysis of variance and Tukey’s post-hoc test showed that adding 2.5 wt% of silanized AlO; GroupS significantly increased the flexural strength compared to Group C and GroupN (p&amp;#60;0.0001). Within the limitation of this study, AlO fillers are potential reinforcers in denture bases which increased flexural strength.

Ecodesign Enhancement of Polymeric Resins: Reinforcing with Synthetic and Natural Fibers Using Theory of Inventive Problem Solving-Algorithm of Inventive Problem Solving for Sustainable Composite Design.

This study examines the enhancement of the mechanical strength of polymer resins through reinforcement with synthetic (glass) and natural (hemp, jute) fibers, using the TRIZ-ARIZ methodology to optimize composite design for improved mechanical properties, sustainability, and economic efficiency. Mechanical testing, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were conducted to evaluate the properties of the composite materials. Regarding tensile strength testing, the results showed the following: jute fiber achieved the best results, with a maximum tensile values of 43.75 MPa (partial reinforcement) and 43.53 MPa (complete reinforcement); glass fiber recorded maximum tensile values of 34.55 MPa (partial reinforcement) and 34.52 MPa (complete reinforcement); and hemp fiber yielded maximum tensile values of 24.98 MPa (partial reinforcement) and 24.86 MPa (complete reinforcement). The mechanical performance of partial reinforcements (in the area of maximum stress) was similar to that of complete reinforcements, enabling a reduction in material usage by up to 60%. The thermal analysis (TGA) results demonstrated that glass fiber-reinforced composites exhibit high thermal stability, with mass loss starting at 320 °C and a residual mass of 8.02%; for other composite materials, thermal degradation begins at 305 °C, with a residual mass of 3.69%; in jute fiber-reinforced composites, thermal degradation starts at 300 °C, with a residual mass of 3.71%. SEM analysis generally revealed good fiber-matrix adhesion, while defects such as voids or detached fibers contributed to reduced mechanical strength. These results demonstrate that natural fiber-reinforced composite materials, particularly those reinforced with jute, can be used in sustainable engineering applications. They also show that localized reinforcement provides high performance with minimal resource consumption.

An in vitro Survey on the Effect of Six Commercial Brands of Phosphoric Acid on the Micro-shear Bond Strength of Composite Resin to Enamel.

One of the most important factors in the clinical longevity of composite resin restorations is proper adhesion, which is achieved using phosphoric acid. Different phosphoric acid products might affect the micro-shear bond strength of composite resin to enamel. The present study aimed to evaluate the micro-shear bond strength of composite resin to sound enamel using six different brands of acid-etch agents. The present in vitro study was carried out on 72 extracted sound human (mandibular and maxillary) first premolar teeth. The teeth crowns were divided into two equal parts with a mesiodistal cut and randomly assigned to six groups in terms of the acid etchant brand: Ultra-etch, SDI, Morvabon, FGM, Nik Darman, and Experimental. The bonding procedure was carried out using the Margin Bond enamel adhesive. Tygon tubes (1×0.7 mm) containing composite resin were bonded to each enamel surface. After 24 hours of storage in distilled water, each sample underwent a shearing force with a crosshead speed of 0.5 mm/min. The morphologic changes were evaluated using scanning electron microscopy. The data were analyzed with SPSS using one-way ANOVA and Tukey test (p< 0.05). One-way ANOVA showed that micro-shear bond strength in different etchant agents have significant differences (p< 0.001). The highest and lowest composite resin micro-shear bond strengths belonged to Ultradent and SDI brands, respectively. The enamel surfaces in the SDI group revealed residual debris after dissolution. Preparation of the enamel surface with different phosphoric acid products might affect the micro-shear bond strength and enamel surface morphology differently. Further clinical studies are suggested to evaluate the effect of different types and concentrations of acid etching agents on the enamel and dentin bonds.

Construction of epoxy composites with double alternating “rigid-flexible” structures: Curing kinetics and thermal/mechanical properties

The curing rate, post-curing modulus, and strength of epoxy resin are key performance indicators for epoxy resin-based composites. Optimizing these factors is essential for improving production processes and expanding practical applications. Functionalized rigid-flexible bilayer transition interfaces between nano-ZnO and epoxy resins were developed using chitosan (CS) and 1,2,3-Tris(glycidyloxy)propane (GTE). Their impact on the curing characteristics, rheology, and mechanical properties of the composites was investigated. The activation energies of pure EP and systems containing ZnO, ZnO-CS, and ZnO-CS-GTE were studied using non-isothermal calorimetry, obtaining 53.604 KJ/mol, 52.548 KJ/mol, 56.66 KJ/mol, and 51.482 KJ/mol, respectively. ZnO-CS-GTE showed a notably stronger promotional effect. Nano-ZnO inhibited gelation due to filler aggregation at 80 °C for 4 min, while ZnO-CS-GTE promoted gelation in just 2.6 min owing to its functional groups, achieving a modulus near 1 GPa after curing. Mechanical studies revealed that the tensile, flexural, and compressive strengths of the ZnO-CS-GTE system increased by 48.52 %, 32.67 %, and 45.01 %, respectively, with flexural and compressive moduli rising by 15.14 % and 15.76 %. The rigid-flexible interface enhanced the dispersion of epoxy resin and strengthened interfacial adhesion.

Improving impact strength and fracture toughness of epoxy resin through oligoester—A byproduct derived from the unsaturated polyester resin manufacturing process

Improving impact strength and fracture toughness of epoxy resin through oligoester—A byproduct derived from the unsaturated polyester resin manufacturing process

A comparative study of strength and surface properties of permanent 3D-printed resins with CAD-CAM milled fixed dental prostheses.

To compare the strength, surface roughness, and hardness of newly introduced permanent three-dimensional (3D)-printed resin in comparison with computer-aided design and computer-aided manufacturing (CAD-CAM) milled materials. Three 3D-printed resins (NextDent C&B, Formlabs Permanent Crown, and VarseoSmile Crownplus) and two CAD-CAM milled (IPS e.max ZirCAD LT and VITA Enamic) resins were used to fabricate discs specimens. A total of 200 disc specimens were fabricated according to manufacturer recommendations. Within each group, half of the specimens were subjected to thermal cycling (5°C-55°C, the 30s, 5000 cycles). Aged and nonaged specimens were evaluated for biaxial flexural strength (BFS), surface roughness, and hardness. Results were statistically analyzed using analysis of variance (ANOVA) and t-tests (α=0.05). Significant differences (p<0.05) were observed in the BFS, surface roughness, and hardness between the 3D-printed and milled groups, before and after thermal aging. Overall, the CAD-CAM milled ceramic group had superior strength, surface roughness, and hardness when compared to all other groups (p<0.001), except for surface roughness after thermal aging, which was similar in all groups (p=0.063). Within each group, there was no significant difference (p>0.05) in surface roughness after thermal aging. BFS values of 3D-printed materials were statistically similar. In terms of surface roughness, Formlabs specimens displayed the highest value before and after thermal cycling, when compared to other 3D-printed materials. Regarding hardness, the VarseoSmile Crown plus group demonstrated the highest values compared to other 3D-printed materials, before and after thermal cycling. Permanent 3D-printed resins have lower strength than CAD-CAM milled materials. 3D-printed permanent resin materials exhibited high roughness and comparable hardness to CAD-CAM materials. Thermal aging negatively affected the properties of 3D-printed permanent crowns. Owing to the low strength of 3D-printed permanent resins, they may not be recommended for clinical practice until further improvements in flexural strength are made to meet clinical standards.

Impact of radiation therapy regimen on the dislodgement resistance of endodontic sealers: A micro push-out test

PurposeThis study aimed to assess the impact of the radiation therapy regimen on the dislodgement resistance of endodontic sealers of different bases through a micro push-out test. Materials and methodsDentin slices were obtained from the cervical and middle root thirds of bovine incisors and distributed into three groups, according to the radiation therapy regimen (n = 30): non-irradiated; 50 Gy; and 70 Gy. Three 1.0 mm diameter root canal-like cavities were made in each dentin slice. Each cavity was filled with the following sealers: AH Plus Jet (epoxy resin), BioRoot RCS (bioceramic) and Endofill (zinc oxide). After 7 days, a micro push-out test was performed in a Universal Testing Machine. Failures were analyzed using a stereomicroscope. Statistical analysis included the application of Three-Way Analysis of Variance (ANOVA) followed by Bonferroni's post-hoc test (α = 5 %). ResultsNon-irradiated specimens filled with AH Plus Jet and BioRoot RCS had higher bond strength than the irradiated ones, regardless of the radiation therapy regimen (p < 0.001). There were no differences between specimens irradiated with 50 Gy and 70 Gy for AH Plus Jet and BioRoot RCS (p > 0.05). There were no differences among non-irradiated and irradiated specimens for Endofill at the cervical third (p = 0.406). Cohesive failure was the most frequent before irradiation. After irradiation, mixed failure was the most frequent. ConclusionRadiation therapy reduced the bond strength of both epoxy resin and bioceramic sealers. The zinc oxide-based sealer exhibited the lowest dislodgement resistance, making it a less suitable option for patients undergoing radiotherapy.

Evaluation of flexural strength of additively manufactured resin materials compared to auto-polymerized provisional resin with and without hydrothermal aging

PurposeAdditive manufacturing (AM) technologies are used to fabricate 3D-printed provisional dental restorations. The purpose of this study was to investigate the flexural strength of 3D-printed resins and compare their mechanical performance with those of conventional resins indicated for provisional restorations. Materials and methodsThis study included six different 3D-printed resin materials, namely (Nextdent (ND); Temp PRINT (TP); Optiprint temp (OT); 3Delta Etemp (DE); Saremco print | CROWNTEC (SA); MED690 (ST)), and one conventional (Protemp (PT)) (Control) provisional resin material. Specimens (N = 168) were prepared (25x2x2 mm3) following ISO 10477:2018 guidelines for temporary materials using a printer (Asiga MAX 3D). Post-processing was accomplished following each manufacturer's recommendation. While half of the specimens were tested after 24 H without aging, the other half was subjected to thermomechanical aging in a custom-made chewing simulator (1.200.000 cycles, 5 °C and 55 °C). Flexural strength of the specimens was determined using a Universal Testing Machine. Data were analyzed using two-way ANOVA followed by Tukey's post-hoc test (α = 0.05). Weibull modulus for each group was calculated based on parametric distribution analysis of censored data for maximum fracture load. ResultsNo significant difference was observed in mean flexural strength (MPa) when non-aged and aged conditions were compared in the OT and PT groups (p>0.05). Groups ND, SA, TP, DE, and ST presented significant differences ranging between 12.67 and 57.39 MPa (p<0.05). All groups presented lower shape and scale values in aged groups compared to their non-aged counterparts. While OT and PT maintained their flexural strength after aging, ND exhibited the highest decrease (30%), followed by DE (23.8%), SA (16.2%), TP (12%), and ST (8.6%) in descending order. Weibull modulus decreased as a function of aging except in group ST. ConclusionSignificant effect of themomechanical aging especially on ND and DE materials should be considered with caution when such materials are indicated as interim or long-term interim provisional restorations. SA and TP exceeded the expectations from a provisional material compared to that of the conventional control material PT.

Effects of laser treatment on bond strength of epoxy resin and calcium silicate-based sealers: a systematic review and meta-analysis of in vitro studies.

This study aimed to systematically review the effect of laser treatment on the bond strength of epoxy resin-based and calcium silicate-based endodontic sealers to root dentine. The search encompassed four databases: PubMed/MEDLINE, EMBASE, Scopus, and ISI Web of Science. Inclusion criteria were limited to in vitro studies conducted on extracted human teeth evaluating bond strength in megapascals (MPa) of either epoxy resin-based or calcium silicate-based sealers, using the push-out test. Two independent reviewers appraised the methodological quality of the selected studies to assess the risk of bias. Meta-analysis was performed for different laser types, endodontic sealers, and control groups. Standard Mean Difference and 95% Confidence Interval values were calculated. 17 studies met the inclusion criteria for qualitative synthesis, and 15 for quantitative analysis. Meta-analyses revealed that certain lasers (Er,Cr:YSGG, Er:YAG) significantly increased bond strength for epoxy resin-based sealers when compared to negative controls (inert solutions), but did not show a significant advantage over EDTA agent. For calcium silicate-based sealers, laser treatment did not show significant enhancement in bond strength compared to either inert solutions or EDTA. The subgroup analysis suggested that erbium lasers, especially in the PIPS mode, potentially increase the bond strength of epoxy resin-based sealers. Laser treatment enhances the bond strength of epoxy resin-based sealers compared to inert solutions, but not more than EDTA. For calcium silicate-based sealers, laser treatment does not significantly improve bond strength over inert solutions or EDTA. Laser treatment increases the bond strength of epoxy resin-based sealers.

Zinc zeolite nanoparticle-modified adhesive resin: Influence on dentin matrix degradation and bond strength to dentin

PurposeEndogenous dentin enzymes degrade collagen fibrils in the restoration-dentin interface. Zinc has been identified as a potential enhancer of adhesive interface stability of adhesive interface by inhibiting enzymatic activity. The present study aimed to investigate the degradation resistance of adhesive interfaces created by a resin adhesive containing zinc zeolite nanoparticles. Materials and methodsDentin beams (1 mm x 2 mm x 6 mm), completely demineralized in 0.5 M EDTA and treated with 10 % phosphoric acid for 15 min (control), were immersed in experimental resin (40 % bis-GMA, 30 % TCDM, 28.75 % TEGDMA, and 1 % EDMAB) modified with 0, 2, 5 and 10 wt% zinc zeolite nanoparticles for 2 h. Each beam was then incubated in artificial saliva medium for 1, 3, 7, 14 and 30 days, with dry mass loss measured at each time-point. Hydroxyproline and CTX contents were analyzed in the incubation medium. Zinc release from zinc zeolite-containing resin disks was measured with atomic emission spectroscopy. The microtensile bond strength (μTBS) of zinc zeolite-modified adhesive resin (All Bond Universal, Bisco Inc.) to dentin was also tested. The data were analyzed using repeated measures of ANOVA, and ANOVA and post-hoc Tukey HSD tests at p = 0.05. ResultsZinc zeolite at 10 wt% showed higher mass loss at all time-points, except on the 1-day (p < 0.05). No significant difference was found in hydroxyproline contents of the incubation medium (p > 0.05), however, the CTX quantity was higher in the zinc zeolite 10 % group (p < 0.05). Zinc release was confirmed for zeolite groups, reaching the maximum level at the 7 days of incubation. Zinc zeolite at 10 wt% resulted in significantly lower μTBS (p < 0.05). ConclusionsZeolite nanoparticles incorporated in dentin adhesives may serve as ion reservoirs. However, zinc content of zeolite particles should be adjusted according to the optimum levels for the inhibition of dentin enzymes.

Effect of low velocity impact at different temperatures on hybrid adhesives in aluminium-composite single lap joints

This study aims to investigate the effect of a small stone impact on aluminum composite adhesive joints used in aircraft after exposure to various temperature conditions. In this context, single lap adhesive joints were prepared using 2024-T3 aluminium alloy sheets and 8-layer carbon fiber-reinforced epoxy hybrid composite sheets, with epoxy adhesive applied to the bonding surfaces. In addition, different types of hybrid adhesives were developed by reinforcing pure epoxy adhesive with various ratios (1%, 3% and 5% by weight) of graphene doped and undoped Nylon 6.6 (N6.6) nanofibers produced by electrospinning method to reduce brittleness. Low-velocity impact tests of 1.04 m/s under five different temperatures (−50, −20, 0, 23 and 50°C) were applied to all single lap adhesion joints produced and tensile tests were applied to the non-failed specimens to examine the loading conditions after low-speed impact. It was determined that approximately 1.5 J of the 3 J energy given by the low- velocity impact was absorbed in common in all samples, while the remaining part was returned and some separation occurred within the adhesion area due to the effect of this impact. While the low- velocity post-impact tensile strength of pure epoxy resin was measured as 2230.3 N at 23°C and 585.15 N at −50°C, the highest values were obtained in N6.6 reinforced epoxy adhesive with 1%GNP additive, which was measured as 3206.39 N at 23°C and 641.82 N at −50°C, and increased by 43.7% and 9.6% for 23°C and −50°C, respectively. In addition, the rupture surfaces of the specimens destroyed by the tensile test were examined by scanning electron microscopy (SEM) for damage analysis.

Effect of glutathione on bond strength of composite resin to enamel following extracoronal bleaching.

Bleaching is a conservative treatment option to deliver esthetic smile makeover for discoloured tooth. Various concentration of bleaching agents can influence the bonding of the restoration to the tooth. The aim of the study was to determine the effect of glutathione on bond strength of composite resin to enamel following extra coronal bleaching at two different time intervals. Forty molars were randomly assigned into four groups of ten each. Group A: Bleaching followed by immediate composite build up and no antioxidant application. Group B: bleaching followed by application of 20% Glutathione and immediate composite built-up was done. Group C: Bleaching followed by composite restoration after one week. Group D: Bleaching followed by application of 20% Glutathione before composite build up after one week. Shear bond strength was tested using a universal testing machine and fracture analysis was done using scanning electron microscope (SEM). Data were analyzed by one-way ANOVA and Post Hoc test with 95% level of significance (p<0.05). Group D, which was treated with glutathione and restored after one week, revealed the highest shear bond strength compared to group B which was immediately restored following treatment with glutathione. Addition of 20% Glutathione as an antioxidant increased the shear bond strength of composite resin to enamel following extra-coronal bleaching using 40% hydrogen peroxide.

Flexural strength and surface hardness of nanocomposite denture base resins

PurposeHigher bending forces during chewing and occlusal loading can lead to the deformation of denture bases. Roughness and microbial adhesion can be the result of improper care of the denture. Many attempts have been made to improve the properties of denture bases through the addition of different materials. The present study aimed to evaluate the surface hardness and flexural strength (FS) of newly formulated nanocomposite denture base resin made by adding zinc oxide (ZnO) and titanium dioxide (TiO2) nanoparticles in heat polymerized polymethyl methacrylate resin in concentrations of 1 % and 2 %. MethodsRectangular metal master dies of dimension 65mm × 10mm × 3.3 mm for flexural strength and 30mm × 10mm × 3 mm for surface hardness were made. These dies were duplicated in 120 acrylic resin samples. These samples were divided into five groups in which group I is control group samples in conventional resin and group II,III, IV &V contained 1 % and 2 % concentrations of ZnO & TiO2 nanoparticles in heat cure acrylic resin. The processing and finishing of the models were done. Flexural strength was measured using a universal testing machine and surface hardness using a Rockwell hardness testing machine. ResultsThe minimum SH reported was 101.7 HRM while FS was 81.1 MPa and maximum was 118.7 HRM and 131.8 MPa respectively. The results showed that group IV containing 1 % TiO2 nanoparticles showed the highest surface hardness values whereas the flexural strength was highest in group II containing 1 % ZnO nanoparticles. The analysis of variance showed a p value of <0.001 which was statistically highly significant. ConclusionNanocomposite denture base resins modified with ZnO & TiO2 nanoparticles have more flexural strength and surface hardness than conventional denture base resin. Clinical implicationThe hardness of a denture base material can be increased by adding these nanoparticles for long term use in oral cavity and in cases prone to denture fracture.