Effect of polymerization mode on shrinkage kinetics and degree of conversion of dual-curing bulk-fill resin composites.

OBJECTIVES: To assess the behavior of dual-cure and conventional bulk-fill composite materials on real-time linear shrinkage, shrinkage stress, and degree of conversion. MATERIALS AND METHODS: Two dual-cure bulk-fill materials (Cention, Ivoclar Vivadent (with ion-releasing properties) and Fill-Up!, Coltene) and two conventional bulk-fill composites (Tetric PowerFill, Ivoclar Vivadent; SDR flow + , Dentsply Sirona) were compared to conventional reference materials (Ceram.x Spectra ST (HV), Dentsply Sirona; X-flow; Dentsply Sirona). Light curing was performed for 20 s, or specimens were left to self-cure only. Linear shrinkage, shrinkage stress, and degree of conversion were measured in real time for 4 h (n = 8 per group), and kinetic parameters were determined for shrinkage stress and degree of conversion. Data were statistically analyzed by ANOVA followed by post hoc tests (α = 0.05). Pearson's analysis was used for correlating linear shrinkage and shrinkage force. RESULTS: Significantly higher linear shrinkage and shrinkage stress were found for the low-viscosity materials compared to the high-viscosity materials. No significant difference in degree of conversion was revealed between the polymerization modes of the dual-cure bulk-fill composite Fill-Up!, but the time to achieve maximum polymerization rate was significantly longer for the self-cure mode. Significant differences in degree of conversion were however found between the polymerization modes of the ion-releasing bulk-fill material Cention, which also exhibited the significantly slowest polymerization rate of all materials when chemically cured. CONCLUSIONS: While some of the parameters tested were found to be consistent across all materials studied, heterogeneity increased for others. CLINICAL RELEVANCE: With the introduction of new classes of composite materials, predicting the effects of individual parameters on final clinically relevant properties becomes more difficult.

Zirconia Nanoparticles as Reinforcing Agents for Contemporary Dental Luting Cements: Physicochemical Properties and Shear Bond Strength to Monolithic Zirconia.

Nanofillers in resin materials can improve their mechanical and physicochemical properties. The present work investigated the effects of zirconia nanoparticles (NPs) as fillers in commercial dental luting cements. Two dual-cured self-adhesive composites and one resin modified glass ionomer (RMGI) luting cement were employed. Film thickness (FT), flexural strength (FS), water sorption (Wsp), and shear bond strength (SBS) to monolithic zirconia were evaluated according to ISO 16506:2017 and ISO 9917-2:2017, whereas polymerization progress was evaluated with FTIR. Photopolymerization resulted in double the values of DC%. The addition of 1% wt NPs does not significantly influence polymerization, however, greater amounts do not promote crosslinking. The sorption behavior and the mechanical performance of the composites were not affected, while the film thickness increased in all luting agents, within the acceptable limits. Thermocycling (TC) resulted in a deteriorating effect on all composites. The addition of NPs significantly improved the mechanical properties of the RMGI cement only, without negatively affecting the other cements. Adhesive primer increased the initial SBS significantly, however after TC, its application was only beneficial for RMGI. The MDP containing luting cement showed higher SBS compared to the RMGI and 4-META luting agents. Future commercial adhesives containing zirconia nanoparticles could provide cements with improved mechanical properties.

An injectable sequential dual-crosslinking catechol-functionalized hyaluronic acid hydrogel for enhanced regeneration of full-thickness burn injury.

Severe burn injuries with massive dermal loss are often underestimated despite their significant impact on morbidity and mortality. Resembling the natural extracellular matrix (ECM), hyaluronic acid (HA)-based dressings have been extensively explored as suitable candidates for burn wound treatment. However, native HA hydrogel's limitations, such as low mechanical strength, rapid degradation, and uncontrollable drug delivery, hinder its efficacy, especially for full-thickness burns requiring injectable hydrogels with robust antibacterial and angiogenic capabilities. Herein, we present a novel multifunctional sequential dual-curing hydrogel system, combining hyperbranched poly(DMA-DMAPMA-PEGDA) (DDP) polymer with thiolated hyaluronic acid (HA-SH). The DDP copolymer, featuring multi-vinyls and catechol functionalities, facilitates two curing reactions taking place sequentially with HA-SH under physiological conditions, balancing convenient injection with the mechanical strength essential for effective wound management. Furthermore, the resulting DDP/HA hydrogels demonstrate enhanced therapeutic attributes, including intrinsic angiogenic and antimicrobial effects, setting them as promising dressing options for deep burn wound therapy.

Thermo-Responsive Shape-Memory Dual-Cured Polymers Based on Vegetable Oils.

The development of thermo-responsive shape-memory polymers has attracted attention due to their ability to undergo reversible deformations based on temperature changes. Vegetable oils are confirmed to be an excellent biorenewable source of starting materials for the synthesis of polymers. Therefore, the objective of this research was to synthesize thermo-responsive shape-memory polymers based on vegetable oils by using the dual-curing technique and obtaining polymers with tailorable properties. Acrylated epoxidized soybean oil and two epoxidized vegetable oils, linseed oil and camelina oil, were chosen for dual curing with m-xylylenediamine. Rheological tests were used to analyze the curing kinetics of systems undergoing radical photopolymerization, thermal cationic polymerization, and dual-curing processes. The rheological, mechanical, and thermal characteristics of the polymers were enhanced by the second curing stage. Dual-cured vegetable oil-based polymers had shape-memory properties with a recovery ratio of 100%, making them suitable for a variety of applications, including electronics, biomedical devices, and robotics.

Could light-curing time, post-space region and cyclic fatigue affect the nanomechanical behavior of a dual-curing cement for fiber post luting?

OBJECTIVE: To evaluate the effects of curing time, post-space region and cyclic fatigue on the micromechanical properties of a fiber-post luting cement. The null hypotheses were that (1) curing time, (2) fatigue and (3) post-space region does not affect the nanoindentation modulus and hardness of the dual-curing cement. MATERIALS AND METHODS: 48 premolars were endodontically treated and a class I cavity and 8 mm deep post space was prepared. Fiber posts were luted with a universal, dualized adhesive system and a dual-curing cement following manufacturer's instructions. Specimens were divided into three groups (16 specimens for each group) according to light-curing time (no light-curing, 20 s light-curing and 120 s light-curing), which was performed with a LED lamp at 1000 mW/cm 2. The coronal part of the cavity was restored using a nano-filled resin composite. After 24 h, 8 specimens for each group were randomly extract in order to undergo to fatigue test in wet condition through a chewing simulator, while the other specimens were kept in distilled water as benchmark. All the restored teeth were then sectioned in 1 mm thick slices perpendicularly to the fiber post axis. Specimen slices were classified in coronal and apical to be tested through a nanoindenter. Data were analyzed through Kruskal-Wallis test with a significance level of 1%, in order to evaluate the influence of treatments (i.e., curing time and cyclic loading) on the micromechanical properties of the tested luting cement. RESULTS: Both fatigue and curing time significantly influenced nanoindentation modulus and hardness of dual-curing cement (p < 0.01). No significant differences were reported for post space region. A significant interaction was found among the analyzed factors (p < 0.01). SIGNIFICANCE: 120 s light-curing time is recommended in order to achieve optimal mechanical proprieties, independently from post space region and cyclic fatigue. As matter of fact, 120 s light-curing allowed to prevent strain hardening induced by the fatigue simulation.

Thermo-Responsive Shape Memory Vanillin-Based Photopolymers for Microtransfer Molding.

Novel thermo-responsive shape-memory vanillin-based photopolymers have been developed for microtransfer molding. Different mixtures of vanillin dimethacrylate with tridecyl methacrylate and 1,3-benzenedithiol have been tested as photocurable resins. The combination of the different reaction mechanisms, thiol-acrylate photopolymerization, and acrylate homopolymerization, that were tuned by changing the ratio of monomers, resulted in a wide range of the thermal and mechanical properties of the photopolymers obtained. All polymers demonstrated great shape-memory properties and were able to return to their primary shape after the temperature programming and maintain their temporary shape. The selected compositions weretested by the microtransfer molding technique and showed promising results. The developed thermo-responsive shape-memory bio-based photopolymers have great potential for forming microtransfered structures and devices applicable on non-flat surfaces.

Comparative Evaluation of Compressive Strength and Flexural Strength of Self-cured Cention N with Dual-cured Cention N: An In Vitro Study.

Aim and objective: This study aimed to investigate and compare compressive strength and flexural strength of self-cured Cention N with dual-cured Cention N. Materials and methods: Cention N is mixed according to the proportions, as mentioned by the manufacturer. Dual cured samples are cured using a diode that emits blue light. Cylindrical plexiglass split mold of dimension 6 mm height, and 4 mm diameter used to fabricate samples for compressive strength. Compressive strength tested using Instron universal testing machine. Rectangular plexiglass split mold of dimension 25 mm length, 2 mm height, and 2 mm width were used to fabricate samples for flexural strength. Flexural strength tested using Instron universal testing machine. To compare the mean values independent t-test was used and the significance of the study was measured by calculating a p-value. Result: There is no statistically significant difference between compressive strength and flexural strength of self-cured Cention N with dual-cured Cention N. Conclusion: The type of polymerization does not affect flexural strength and compressive strength of Cention N. Clinical Significance: Self-curing polymerization alone is sufficient for Cention N to achieve adequate compressive strength and flexural strength. So it can be inserted as a single layer on a prepared cavity and to fasten curing additional light curing can be used. How to cite this article: Fousiya Ks, Balagopal VR, Suresh KJ, et al. Comparative Evaluation of Compressive Strength and Flexural Strength of Self-cured Cention N with Dual-cured Cention N: An In Vitro Study. Int J Clin Pediatr Dent 2022;15(2):210-214.

Functionalized Soybean Oil- and Vanillin-Based Dual Cure Photopolymerizable System for Light-Based 3D Structuring.

A novel dual cure photopolymerizable system was developed by combining two plant-derived acrylic monomers, acrylated epoxidized soybean oil and vanillin dimethacrylate, as well as the thiol monomer pentaerythritol tetrakis (3-mercaptopropionate). Carefully selected resin composition allowed the researchers to overcome earlier stability/premature polymerization problems and to obtain stable (up to six months at 4 °C) and selectively-polymerizable resin. The resin demonstrated rapid photocuring without an induction period and reached a rigidity of 317.66 MPa, which was more than 20 times higher than that of the other vanillin-based polymers. Improved mechanical properties and thermal stability of the resulting cross-linked photopolymer were obtained compared to similar homo- and copolymers: Young's modulus reached 4753 MPa, the compression modulus reached 1634 MPa, and the temperature of 10% weight loss was 373 °C. The developed photocurable system was successfully applied in stereolithography and characterized with femtosecond pulsed two-beam initiation threshold measurement for the first time. The polymerization threshold of the investigated polymer was determined to be controlled by the sample temperature, making the footprint of the workstations cheaper, faster, and more reliable.

Post-Cure Development of the Degree of Conversion and Mechanical Properties of Dual-Curing Resin Cements.

This study investigated the effect of different curing conditions on the degree of conversion and mechanical properties of contemporary dual-curing resin cements. The material specimens were either light-cured directly, light-cured through a 1-mm lithium disilicate glass-ceramic layer, or self-cured. The degree of conversion was measured in 0.1-mm films using Fourier-transform infrared spectroscopy 1 day, 7 days, and 28 days post-cure. Specimens used to study the flexural strength and modulus were prepared according to the ISO 4049 protocol, stored for 28 days post-cure, and subjected to accelerated aging by absolute ethanol immersion. The degree of conversion values ranged between 44.3-77.8%. Flexural strength varied between 11.4-111.1 MPa, while flexural modulus amounted to 0.7-5.5 GPa. The degree of conversion was significantly affected by material type, curing conditions, and post-cure time; however, variations in curing conditions were the least influential factor. A statistically significant effect of curing conditions on the degree of conversion was identified for only one of the five materials tested, whereas the flexural strength and modulus of all tested materials were significantly reduced in the experimental groups that were light-cured through a ceramic layer or self-cured. The effect size analysis showed that mechanical properties were most affected by the material type, while the differences in curing conditions were less influential. A comparison of the degree of conversion and mechanical properties indicated that different curing conditions may lead to significantly different flexural strength and modulus, which are not necessarily accompanied by identifiable variations in the degree of conversion.

Cost-Effectively 3D-Printed Rigid and Versatile Interpenetrating Polymer Networks.

Versatile acrylate-epoxy hybrid formulations are becoming widespread in photo/thermal dual-processing scenarios, especially in 3D printing applications. Usually, parts are printed in a stereolithography or digital light processing (DLP) 3D printer, after which a thermal treatment would bestow the final material with superior mechanical properties. We report the successful formulation of such a hybrid system, consisting of a commercial 3D printing acrylate resin modified by an epoxy-anhydride mixture. In the final polymeric network, we observed segregation of an epoxy-rich phase as nano-domains, similar to what was observed in a previous work. However, in the current work, we show the effectiveness of a coupling agent added to the formulation to mitigate this segregation for when such phase separation is undesired. The hybrid materials showed significant improvement of Young's modulus over the neat acrylate. Once the flexible, partially-cured material was printed with a minimal number of layers, it could be molded into a complex form and thermally cured. Temporary shapes were readily programmable on this final material, with easy shape recovery under mild temperatures. Inspired by repairable 3D printed materials described recently, we manufactured a large object by printing its two halves, and then joined them covalently at the thermal cure stage with an apparently seamless union.

Vegetable Oil-Based Thiol-Ene/Thiol-Epoxy Resins for Laser Direct Writing 3D Micro-/Nano-Lithography.

The use of renewable sources for optical 3D printing instead of petroleum-based materials is increasingly growing. Combinations of photo- and thermal polymerization in dual curing processes can enhance the thermal and mechanical properties of the synthesized thermosets. Consequently, thiol-ene/thiol-epoxy polymers were obtained by combining UV and thermal curing of acrylated epoxidized soybean oil and epoxidized linseed oil with thiols, benzene-1,3-dithiol and pentaerythritol tetra(3-mercaptopropionate). Thiol-epoxy reaction was studied by calorimetry. The changes of rheological properties were examined during UV, thermal and dual curing to select the most suitable formulations for laser direct writing (LDW). The obtained polymers were characterized by dynamic-mechanical thermal analysis, thermogravimetry, and mechanical testing. The selected dual curable mixture was tested in LDW 3D lithography for validating its potential in optical micro- and nano-additive manufacturing. The obtained results demonstrated the suitability of epoxidized linseed oil as a biobased alternative to bisphenol A diglycidyl ether in thiol-epoxy thermal curing reactions. Dual cured thermosets showed higher rigidity, tensile strength, and Young's modulus values compared with UV-cured thiol-ene polymers and the highest thermal stability from all prepared polymers. LDW results proved their suitability for high resolution 3D printing-individual features reaching an unprecedented 100 nm for plant-based materials. Finally, the biobased resin was tested for thermal post-treatment and 50% feature downscaling was achieved.

Enhancement of 3D-Printable Materials by Dual-Curing Procedures.

Dual-curing thermosetting systems are recently being developed as an alternative to conventional curing systems due to their processing flexibility and the possibility of enhancing the properties of cured parts in single- or multi-stage processing scenarios. Most dual-curing systems currently employed in three-dimensional (3D) printing technologies are aimed at improving the quality and properties of the printed parts. However, further benefit can be obtained from control in the curing sequence, making it possible to obtain partially reacted 3D-printed parts with tailored structure and properties, and to complete the reaction by activation of a second polymerization reaction in a subsequent processing stage. This paves the way for a range of novel applications based on the controlled reactivity and functionality of this intermediate material and the final consolidation of the 3D-printed part after this second processing stage. In this review, different strategies and the latest developments based on the concept of dual-curing are analyzed, with a focus on the enhanced functionality and emerging applications of the processed materials.

Acetoacetate Based Thermosets Prepared by Dual-Michael Addition Reactions.

A novel set of dual-curable multiacetoacetate-multiacrylate-divinyl sulfone ternary materials with versatile and manipulable properties are presented. In contrast to common dual-curing systems, the first stage polymer herein consists of a densely crosslinked, high Tg network as a result of base-catalyzed multiacetoacetate-divinyl sulfone Michael addition. A more flexible secondary network forms after base-catalyzed Michael addition of remaining multiacetoacetate to multiacrylate. Curing is truly sequential as the rates of the two Michael additions are significantly different. Curing kinetics were analyzed using differential scanning calorimetry (DSC) and Fourier-transform infrared (FTIR). The materials at each curing stage were characterized using dynamic mechanical analysis (DMA) and SEM. Although some phase separation was observed in certain formulations, the incompatibilities were minimized when the molar percentage of the acetoacetate-divinyl sulfone polymer network was above 75%. Furthermore, the environmental scanning electron microscopy (ESEM) images of these materials show that the more flexible acetoacetate-acrylate phase is dispersed in the form of polymeric spheres within the rigid acetoacetate-divinyl sulfone matrix. This unique dual microstructure can potentially render these materials highly resilient in applications requiring densely crosslinked polymer architectures with enhanced toughness.

A New Way of Toughening of Thermoset by Dual-Cured Thermoplastic/Thermosetting Blend.

The work aims at establishing the optimum conditions for dual thermal and electron beam curing of thermosetting systems modified by styrene/butadiene (SB)-based triblock copolymers in order to develop transparent and toughened materials. The work also investigates the effects of curing procedures on the ultimate phase morphology and mechanical properties of these thermoset⁻SB copolymer blends. It was found that at least 46 mol% of the epoxidation degree of the SB copolymer was needed to enable the miscibility of the modified block copolymer into the epoxy resin. Hence, an electron beam curing dose of ~50 kGy was needed to ensure the formation of micro- and nanostructured transparent blends. The micro- and nanophase-separated thermosets obtained were analyzed by optical as well as scanning and transmission electron microscopy. The mechanical properties of the blends were enhanced as shown by their impact strengths, indentation, hardness, and fracture toughness analyses, whereby the toughness values were found to mainly depend on the dose. Thus, we have developed a new route for designing dual-cured toughened micro- and nanostructured transparent epoxy thermosets with enhanced fracture toughness.

Rheological and Mechanical Characterization of Dual-Curing Thiol-Acrylate-Epoxy Thermosets for Advanced Applications.

Mechanical and rheological properties of novel dual-curing system based on sequential thiol-acrylate and thiol-epoxy reactions are studied with the aim of addressing the obtained materials to suitable advanced applications. The crosslinking process is studied by rheological analysis in order to determine conversion at gelation and the critical ratio. These parameters are used to discuss the intermediate material structure for each acrylate proportion and their possible application in the context of dual-curing and multi-step processing scenarios. Results from dynamo-mechanical analysis and mechanical testing demonstrate the high versatility materials under investigation and revealed a wide range of achievable final properties by simply varying the proportion between acrylate and thiol group. The intermediate stability between curing stages has been analysed in terms of their thermal and mechanical properties, showing that these materials can be stored at different temperatures for a relevant amount of time without experiencing significant effects on the processability. Experimental tests were made to visually demonstrate the versatility of these materials. Qualitative tests on the obtained materials confirm the possibility of obtaining complex shaped samples and highlight interesting shape-memory and adhesive properties.

State of the Art in Dual-Curing Acrylate Systems.

Acrylate chemistry has found widespread use in dual-curing systems over the years. Acrylates are cheap, easily handled and versatile monomers that can undergo facile chain-wise or step-wise polymerization reactions that are mostly of the "click" nature. Their dual-curing processes yield two distinct and temporally stable sets of material properties at each curing stage, thereby allowing process flexibility. The review begins with an introduction to acrylate-based click chemistries behind dual-curing systems and relevant reaction mechanisms. It then provides an overview of reaction combinations that can be encountered in these systems. It finishes with a survey of recent and breakthrough research in acrylate dual-curing materials for shape memory polymers, optical materials, photolithography, protective coatings, structured surface topologies, and holographic materials.

Influence of polymerization time on properties of dual-curing cements in combination with high translucency monolithic zirconia.

PURPOSE: The aim of this in vitro study was to assess conversion degree (DC), micro-hardness (MH) and bond strength of two dual-curing resin cements employed under translucent monolithic zirconia irradiated with different time protocols. METHODS: 84 square shaped samples of 1mm thickness were prepared from high translucency zirconia blocks and divided into two groups (n=24) according to the cement employed: (1) Rely-X Ultimate; (2) Panavia SA. Each group was further divided into 3 subgroups (n=8) according to the irradiation time: (a) no light; (b) 20s; (c) 120s. Light curing was performed 60s after the sample was placed on the diamond support of a FT-IR spectrophotometer with a high power multiLED lamp. Final DC% were calculated after 10min. After 24h, Vickers Test on the cement layer was performed. The same protocol was used to lute composite cylinders in order to evaluate microshear bond-strength test. ANOVA and Bonferroni tests were performed to find differences between MH and bond-strength to zirconia, while for DC% the Scheirer-Ray-Hare two-way test was used. RESULTS: The two cements reached higher DC% in subgroup (b) and (c). As concern MH, statistics showed an increase in curing time was able to improve MH significantly. Bond-strength was not affected by irradiation time only for Panavia SA. CONCLUSIONS: The first null hypothesis has to be rejected since DC% and MH of the dual-cements tested were influenced by the curing time. The second null hypothesis is partially rejected since the bond strength was influenced by the curing time only for Rely-X Ultimate.

Effect of an acidic sodium salt on the polymerization behavior of self-adhesive resin cements formulated with different adhesive monomers.

OBJECTIVE: To determine the influence of benzenesulfinic acid sodium salt 98% (BAS) and the activation mode on the polymerization behavior of experimental self-adhesive resin cements (SARCs) formulated with distinct self-etch methacrylates. MATERIALS AND METHODS: Three catalyst-pastes using different self-etch methacrylates (2MP - bis 2-(methacryloyloxy) ethyl phosphate; 4META - 4-methacryloxyethyl trimellitic acid anhydride; and GDMAP - 1,3-glycerol dimethacrylate phosphate) and four base-pastes were formulated from the incorporation of different amounts of BAS associated to N-N-dihydroxyethyl-p-toluidine (DHPT). BAS/DHPT ratios were blended respectively based on the following final weight (wt%): control (0.0;2.0%), BP1 (0.5;1.5%), BP2 (0.8;1.2%) and BP3 (1.0;1.0%). Real-time polymerization kinetics (KP) was assessed for 10min by FTIR spectroscopy. Maximum rate of polymerization (Rpmax) was obtained from the first derivative of the curve conversion versus time. Degree of conversion (DC) was determined over 10min and after 24h. SARCs were tested in self and dual activation modes. Data of Rpmax and DC 24h were respectively analyzed by two-way ANOVA followed by Tukey's method (α=0.05). RESULTS: All factors and their interactions were statistically significant (p<0.01). BAS caused an increase in DC in the first minutes of the KP analysis, especially in self-activated groups. After 24h, all groups showed higher DC than those observed in the first 10min. In general, the addition of BAS increased the Rpmax. The GDMAP-based materials group showed the highest Rpmax values when exposed to light but self-activated formulations with GDMAP or 2MP showed the lowest Rpmax. SIGNIFICANCE: The addition of BAS increased the degree of conversion of SARCs in the first minutes and 24h after the polymerization reaction. This finding showed the importance of adding this type of salt during resin cement production to achieve better polymerization in the first minutes of the luting procedure specially when light exposure is not possible.

Epoxy-Based Shape-Memory Actuators Obtained via Dual-Curing of Off-Stoichiometric "Thiol⁻Epoxy" Mixtures.

In this work, epoxy-based shape-memory actuators have been developed by taking advantage of the sequential dual-curing of off-stoichiometric "thiol⁻epoxy" systems. Bent-shaped designs for flexural actuation were obtained thanks to the easy processing of these materials in the intermediate stage (after the first curing process), and successfully fixed through the second curing process. The samples were programmed into a flat temporary-shape and the recovery-process was analyzed in unconstrained, partially-constrained and fully-constrained conditions using a dynamic mechanical analyzer (DMA). Different "thiol⁻epoxy" systems and off-stoichiometric ratios were used to analyze the effect of the network structure on the actuation performance. The results evidenced the possibility to take advantage of the flexural recovery as a potential actuator, the operation of which can be modulated by changing the network structure and properties of the material. Under unconstrained-recovery conditions, faster and narrower recovery-processes (an average speed up to 80%/min) are attained by using materials with homogeneous network structure, while in partially- or fully-constrained conditions, a higher crosslinking density and the presence of crosslinks of higher functionality lead to a higher amount of energy released during the recovery-process, thus, increasing the work or the force released. Finally, an easy approach for the prediction of the work released by the shape-memory actuator has been proposed.

Correlation between flexural and indirect tensile strength of resin composite cements.

BACKGROUND: To evaluate a potential correlation between flexural strength and indirect tensile strength in assessing the mechanical strength of resin composite cements. METHODS: Flexural strength (n = 5) and indirect tensile strength (n = 5) of 7 resin composite cements (RelyX Unicem 2 Automix [RXU], Panavia SA [PSA], Clearfil SA [CSA], Panavia F2.0 [PF2], Multilink Implant [MLI], DuoCem [DCM], Panavia 21 [P21]) were determined. Specimens were either auto-polymerized or dual-cured (except P21) and stored in water at 37 °C for 1 day prior to measurement. Flexural and indirect tensile strength of 4 cements (RXU, PSA, PF2, MLI) was additionally measured directly after curing and after 96 h water storage at 37 °C. RESULTS: Except for PF2, dual-cured specimens achieved higher flexural strength than auto-polymerized specimens. In the indirect tensile strength test differences in auto-polymerized and dual-cured specimens were only detected for RXU and DCM. A general non-linear correlation was found between flexural and indirect tensile strength values. However, strength values of auto-polymerized and dual-cured specimens did not generally correlate. CONCLUSIONS: Flexural strength and indirect tensile strength of resin composite cements are correlated. At high strength values the indirect tensile test is less sensitive than the flexural test. The results suggest that the indirect tensile test may only be recommended as a screening test especially for low or medium strength resin composite cements.