3D-printed Resin Research Articles

3D printed structures with a tailored refraction index fabricated with an acrylate resin modified by a conjugated polymer

Resins for 3D printing usually do not present suitable photoluminescence for application in optoelectronic devices. Herein, a conjugated polymer (PFeBSe) with luminescent and high refraction index properties was synthesized and used to modify an acrylate-based resin. This PFeBSe copolymer presents an ester-based side group that enhances the compatibility with the acrylate resin, resulting in a homogeneous polymeric blend. Further, the modified resin was employed with the 3D digital light processing (DLP) technique to produce luminescent guiding structures with a tailored refraction index. To maintain the processing parameters of the acrylate resin, the blending with the conjugated polymer was kept at a low concentration in the range of 5% to 15% (v/v). The blending changed the refraction index of the pristine acrylate from 1.49 to 1.51 (5% v/v) and 1.56 (15% v/v), respectively. Moreover, the resulting structures present a low extinction coefficient at the wavelength region above 600 nm. These characteristics enable the fabrication of structures with controllable forms and dimensions that can be used in the design of advanced sensors and optoelectronic devices.

Flexural Properties of Three Novel 3D-Printed Dental Resins Compared to Other Resin-Based Restorative Materials

To evaluate the flexural strength and flexural modulus of three recently introduced 3D-Printed resins and compare them with the flexural properties of other well known, already commercialized, and extensively used resin based dental materials. Three 3D-printed dental resins, a fiber-reinforced epoxy resin, a heat-cured bis-acrylate-based composite resin, two conventional CAD/CAM PMMA, and a graphene-reinforced CAD/CAM PMMA, were selected for this study. Ten prismatic-shaped specimens (2 × 2 × 25 mm) were fabricated for each material (n = 10). All specimens underwent a three-point bending test using a universal testing machine and were loaded until fracture. Flexural strength (MPa) and flexural modulus (MPa) mean values were calculated and compared using the on ranks One-Way ANOVA test. Scanning electron microscope analysis of the 3D-printed resins was performed. Significantly different flexural properties were recorded among the tested materials. The fiber-reinforced epoxy resin exhibited the highest flexural strength (418.0 MPa) while, among the 3D-printed resins, the best flexural strength was achieved by Irix-Max (135.0 MPa). Irix-Plus and Temporis led to the lowest mean flexural strength values (103.9 MPa and 101.3 MPa, respectively) of all the CAD/CAM milled materials, except for the conventional PMMA by Sintodent (88.9 MPa). The fiber-reinforced epoxy resin also showed the highest flexural modulus (14,672.2 MPa), followed by the heat-cured bis-acrylate composite (10,010.1 MPa). All 3D-printed resins had a higher flexural modulus than the conventional PMMA materials. CAD/CAM fiber-reinforced epoxy resin excels in flexural strength, with Irix-Max showing promising flexural properties, which could encourage its use for permanent restorations. Caution is needed with Irix-Plus and Temporis due to their lower flexural strength compared to other traditional materials.

Force system of 3D-printed orthodontic aligners made of shape memory polymers: an in vitro study

ABSTRACT This study aimed to report forces and moments delivered by 3D-printed aligners. Tera Harz TC-85 resin and Zendura FLX (ZF) thermoformed sheets (0.76 mm) were used. Rectangular strip specimens (50 × 10 × 0.6 mm) were produced for a three-point bending test (3PB) at different temperatures. Full anatomical aligners were produced for 3D force measurements on different teeth and directions at 37 °C, using a custom-made device. ZF exhibited flexural forces between 1.7 and 2.3 N, while TC-85 from 0.3 N to 2.7 N, with temperature affecting TC-85 more significantly. At lower temperatures, TC-85 was stiffer than ZF, but at higher temperatures, it became less rigid. The 3D-force measurements indicated comparable values for both materials. Force ranged from 0.3–1.7 N and moment from 4.8–9.4 Nmm. The study concluded that TC-85 3D-printed aligners deliver biologically compatible forces for orthodontic movement and offer better control over thickness. Highlights The 3D-printed Tera Harz TC-85 resin revolutionises aligner production. Tera Harz TC-85 aligners generate forces within the orthodontic accepted range. Shape recovery of TC-85 can enable adaptability and larger incremental step size. The 3D printing offers greater control over aligner design and thickness.

Beyond the surface: A comparative study of intraoral scanners in subgingival configuration scanning

ObjectivesThis study conducted a comprehensive comparative analysis of three intraoral scanners (CEREC Primescan, TRIOS, CEREC Omnicam) and a lab scanner (inEosX5) assessing their precision in simulating subgingival tooth preparations. MethodsUtilizing a dental simulation mannequin with a 3D-printed resin structure, 100 structures with depths ranging from 0.5 to 4.0 mm were created within a square mimicking a rectangular tank surface. Four scanner groups (A-D) and five subgroups were established. Two digitization methods, a customized parallelometer and an intraoral simulation, were applied, ensuring a standardized scanning sequence. Trueness was evaluated by comparing CAD-calculated surface areas with actual dimensions, and qualitative trueness analysis was conducted using MeshLab. Surface areas were computed using the formula SA = 2lw + 2lh + 2wh. Statistical analyses, including Pearson’s correlation coefficient, Kolmogorov–Smirnoff and Levene’s tests, three-way ANOVA, and paired sample t-tests, elucidated relationships and differences (a=0.05). ResultsA robust correlation (r = 0.850, p < 0.001) between intraoral scanner choice and scanned area depth was found. Inverse correlations were noted for experimental methods. Three-way ANOVA demonstrated significant scanner-depth interaction (F(12,760) = 760.801, p < 0.001). SignificanceEmphasizing high-resolution sensors and advanced technologies, the study underscores the optimal choice for subgingival digitization, acknowledging variations among scanners.

3D-printed resin composite posterior fixed dental prosthesis: a prospective clinical trial up to 1 year

ObjectivesThis clinical trial evaluated the clinical behavior of 3D-printed posterior resin composite fixed dental prostheses (FDPs).Materials and methodsBetween 10 October 2020 and 5 August 2022, 49 patients aged 19–60 years (16 men, 33 women) received 68 3D-printed resin composite 3-unit posterior FDPs (ELS Even Stronger, Saremco, Switzerland). FDPs were followed up 2 weeks after placement (baseline), 6 months after placement, and 1 year after placement by two independent calibrated observers using modified FDI criteria for anatomical form, secondary caries, marginal adaptation, surface roughness, color match, fracture of material, staining surface, staining margin, approximate anatomical form, retention, gingival health, and patient's view. Survival analyses were performed using Kaplan–Meier analyses.ResultsA total of 59 restorations were evaluated and the mean observation period was 8.63 months. Failure types were categorized as mechanical and biological. Failures were observed in 14 FDPs. Nine FDPs showed mechanical failure and five FDPs showed biological failure. Mechanical failures were mostly experienced as connector fractures. Eight FDPs showed cohesive fractures (seven in a single connector at either at the mesial or distal and one in the pontic itself). Biological failures, including root canal treatment and gingival tissue reactions, were observed within the first 6 months. Based on mechanical failures, the survival rate was 86.7% including the biological complications; this corresponded to 71.6% (Kaplan–Meier). After 1 year, two FDPs showed surface luster loss (score 4), two-color mismatches (score 4), and two-surface staining (score 4).Conclusion3D-printed resin composite FDPs were observed acceptable after 1 year of clinical follow-up, providing that the experienced failure types were mainly associated with fractures in the connector region, which requires revision of design parameters.Clinical Trial RegistrationClinical Trials.Gov, NCT04600297.

Effect of Dietary Simulating Solvents on the CAD-CAM Provisional Restorative Materials' Microhardness and Color Stability Properties: An in vitro Study.

This in vitro study investigated the effects of dietary solvents on the microhardness and color stability of CAD/CAM provisional restorations compared to conventional materials. Disc-shaped specimens (n=200) were fabricated from self-cured acrylic resin, two 3D-printing resins (FormLabs, NextDent), and a milled material (TelioCAD). Randomization assigned specimens (n=10/group) to immersion solutions: artificial saliva, citric acid, heptane, coffee, and tea. Microhardness and color stability were evaluated. One-way and three-way ANOVA with Tukey's post hoc test analyzed the data. Dietary solvents significantly reduced the surface microhardness of all tested materials (p<0.05). Unpolished surfaces exhibited greater color changes compared to polished ones (p<0.05) across all materials. Coffee and tea induced the most substantial reductions in hardness and the most significant color alterations (p<0.05), whereas saliva and citric acid had minimal effects. Milled provisional restorations exhibited superior hardness and color stability. Dietary solvents significantly affected material properties over time, highlighting the importance of material selection for clinical applications.

Developing a sustainable resin for 3D printing in coral restoration

Coral reefs boast one of the planet&amp;rsquo;s most diversified ecosystems, serving as an essential source of food and revenue for millions of people while providing shelter to a wide variety of marine creatures. However, overfishing, pollution, climate change, and other factors collectively pose an escalating danger to coral reefs. Therefore, coral reef restoration efforts are urgently needed to save corals. In this study, we exploited 3D printing technology based on vat polymerization to fabricate artificial coral plugs, expediting the reef restoration process while minimizing labor costs. We have developed a scalable model through the photoinitiated polymerization of an eco-friendly resin composed of modified soybean oil and calcium carbonate which has the potential to significantly enhance global restoration efforts. Material characterization demonstrated that the printed scaffold was highly cross-linked. Based on cytotoxicity analysis, the printed scaffold exhibited excellent cell adhesion and proliferation characteristics. The coral microfragmentation experiment showed initial signs of coral settlement on the printed coral plugs. This work demonstrates that plant-based material and vat-polymerization-based 3D printing techniques hold promise for coral restoration.

Assessing the suitability of fused deposition modeling to produce acrylic removable denture bases.

To study the feasibility of using poly methyl methacrylate(PMMA) filament and fused deposition modeling (FDM) to manufacture denture bases via the development of a study that considers both conventional and additive-based manufacturing techniques. Five sample groups were compared: heat and cold cured acrylic resins, CAD/CAM milled PMMA, 3D-printed PMMA (via FDM), and 3D-printed methacrylate resin (via stereolithography, SLA). All groups were subjected to mechanical testing (flexural strength, impact strength, and hardness), water sorption and solubility tests, a tooth bonding test, microbiological assessment, and accuracy of fit measurements. The performance of sample groups wasreferred to ISO 20795-1 and ISO/TS 19736. The data was analyzed using one-way ANOVA. Samples manufactured using FDM performed within ISO specifications for mechanical testing, water sorption, and solubility tests. However, the FDM group failed to achieve the ISO requirements for the tooth bonding test. FDM samples presented a rough surface finish which could ultimately encourage an undesirable high level of microbial adhesion. For accuracy of fit, FDM samples showed a lower degree of accuracy than existing materials. Although FDM samples were a cost-effective option and were able to be quickly manufactured in a reproducible manner, the results demonstrated that current recommended testing regimes for conventionally manufactured denture-based polymers are not directly applicable to additive-manufactured denture base polymers. Therefore, new standards should be developed to ensure the correct implementation of additive manufacturing techniques within denture-based fabrication workflow.

Effect of layer thickness and polishing on wear resistance of additively manufactured occlusal splints

ObjectiveTo evaluate the effect of polishing and layering thickness on the wear resistance of 3D-printed occlusal splint materials. MethodsSpecimens with 3 different layer thicknesses (50, 75, 100 µm) were produced in the form of a disc 3 mm thick using V-Print splint resin on a 3D-printer with digital light processing technology. (n = 16 for each thickness) All specimens were washed and cured according to the manufacturer's instructions. Half of the specimens of each layer thickness were polished with silicon carbide papers. All specimens were subjected to 120.000 cycles of a chewing simulator for 2-body wear tests. Before and after the wear test, the specimens were scanned with a laser scanner, and the images were overlaid using a 3D analysis program and the volume loss was calculated. The wear patterns of the specimens were examined under a scanning electron microscope. Statistical evaluation was performed using a Shapiro-Wilk test, 2-way ANOVA, 1-way ANOVA, and Tukey post hoc test (α = 0.05). ResultsWhile polishing had a significant effect (p = 0.003) on the wear volume of the occlusal splints, layer thickness (p = 0.105) and their interaction between polishing and layer thickness (p = 0.620) did not significantly affect the wear volume. Regardless of the polishing, the lowest mean wear was observed for D50 (0.064 mm3), followed by D75 (0.078 mm3), and D100 (0.096 mm3). However, a significant difference was observed only between polished D50 and unpolished D100. ConclusionThe polished 3D-printed occlusal splint resin showed higher wear resistance than the unpolished one, regardless of the layer thickness. Clinical significanceSince different layer thicknesses of 50 µm and greater had no effect on the wear resistance of the material, a layer thickness of 100 µm may be preferred for faster printing. However, polishing occlusal splints may reduce the amount of wear and improve clinical performance.

Comparison of shock absorption capacities of three types of mouthguards: A comparative invitro study.

3D printing processes can be used to manufacture custom-made mouthguards for sports activities. Few studies have compared the impact performance of industrial-created mouthguards with that of custom-made mouthguards manufactured by thermoforming or 3D printing. The objective of this invitro study was to compare the shock absorption capacities of custom-made mouthguards manufactured by 3D printing with industrial mouthguards and thermoformed ethylene vinyl acetate (EVA) mouthguards. For each type of mouthguard, eight samples were produced. 3D-printed mouthguards were manufactured using digital light processing technology. Each mouthguard was subjected to an impact performance test defined by the standard AFNOR XP S72-427, which evaluate maximum deceleration and force transmitted during impact. The thickness of each mouthguard before and after a series of five impacts was measured at the impacted inter-incisal area. The mean maximum decelerations during impact ranged from 129 to 189 g for industrial mouthguards, 287 to 425 g for thermoformed EVA mouthguards, and 277 to 302 g for 3D-printed mouthguards. The mean reduction in mouthguard thickness at the impact zone after five tests was 1.2 mm for industrial mouthguards, 0.6 mm for 3D-printed mouthguards, and 2.2 mm for thermoformed EVA mouthguards. Custom-made 3D printed mouthguards showed slightly better shock absorption ability than thermoformed mouthguards with respect to the indicator proposed in XP S72-427. They seemed to combine the practical advantages of thermoformed mouthguards in sports with better shock absorption capacity and lower cost. Furthermore, they had the least thickness variation during the test, and their shock absorption capacity was the least affected by repeated mechanical tests. Other types of 3D-printing resin materials that will become available must continue to be tested for shock absorption to provide the best protection to users at low cost.

Solmers: Versatile hybrid resins for nanometric 3D printing of silica-based photonic components

Owning to their intrinsic properties, silica-based glasses are widely used in various technological fields, especially in photonics. However, high degree of flexibility is yet challenging in realization of next-generation miniaturized optical components. In this work, we develop an approach based on ‶Solmers″ hybrid resins allowing versatile two-photon polymerization 3D printing of silica glasses with 23 nm resolution, doping with Germanium and/or rare-earths elements. Other dopants such as gold nanoparticles were also incorporated for localized metallization. After 3D printing and sintering (1100–1300 °C), high optical quality glasses with low surface roughness (<0.2 nm) were obtained. Structural analyses confirmed the amorphous structure of silica glasses. Various mono- or multi-materials microstructures were successfully fabricated on fused silica substrates. Besides, this approach was extended to the functionalization of optical fibers for optical sensing applications in harsh environment (1000 °C). Compared to organic or organic-inorganic materials, these dense silica-based glasses with enhanced optical and structural properties will open new avenues for the development of emerging advanced optical components.

Influence of occlusal thickness on the fracture resistance of chairside milled lithium disilicate posterior full-coverage single-unit prostheses containing virgilite: A comparative in vitro study.

To evaluate the fracture resistance of chairside computer-aided design and computer-aided manufacturing (CAD-CAM) lithium disilicate mandibular posterior crowns with virgilite of different occlusal thicknesses and compare them to traditional lithium disilicate crowns. Seventy-five chairside CAD-CAM crowns were fabricated for mandibular right first molars, 60 from novel lithium disilicate with virgilite (CEREC Tessera, Dentsply Sirona), and 15 from traditional lithium disilicate (e.max CAD, Ivoclar Vivadent). These crowns were distributed across five groups based on occlusal thickness and material: Group 1 featured CEREC Tessera crowns with 0.8mm thickness, Group 2 had 1.0mm thickness, Group 3 had 1.2mm thickness, Group 4 with 1.5mm thickness, and Group 5 included e.max CAD crowns with 1.0mm thickness. These crowns were luted onto 3D-printed resin dies using Multilink Automix resin cement (Ivoclar Vivadent). Subsequently, they underwent cyclic loading (2,000,000 cycles at 1Hz with a 275 N force) and loading until fracture. Scanning electron microscopy (SEM) assessed the fractured specimens. Statistical analysis involved one-way ANOVA and the Kruskal-Wallis Test (α = 0.05). Fracture resistance varied significantly (<0.001) across mandibular molar crowns fabricated from chairside CAD-CAM lithium disilicate containing virgilite, particularly between crowns with 0.8mm and those with 1.2 and 1.5mm occlusal thickness. However, no significant differences were found when comparing crowns with 1, 1.2, and 1.5mm thicknesses. CEREC Tessera crowns with 1.5mm thickness exhibited the highest resistance (2119N/mm2), followed by those with 1.2mm (1982N/mm2), 1.0mm (1763N/mm2), and 0.8mm (1144N/mm2) thickness, whereas e.max CAD crowns with 1.0mm occlusal thickness displayed the lowest resistance (814N/mm2). The relationship between thickness and fracture resistance in the virgilite lithium disilicate full-coverage crowns was directly proportional, indicating that increased thickness corresponded to higher fracture resistance. No significant differences were noted among crowns with thicknesses ranging from 1 to 1.5mm. This novel ceramic exhibited superior fracture resistance compared to traditional lithium disilicate.

"Dissolve-on-Demand" 3D Printed Materials: Polymerizable Eutectics for Generating High Modulus, Thermoresponsive and Photoswitchable Eutectogels.

Solvent-free photopolymerization of vinyl monomers to produce high modulus materials with applications in 3D printing and photoswitchable materials is demonstrated. Polymerizable eutectic (PE) mixtures are prepared by simply heating and stirring various molar ratios of N-isopropylacrylamide (NIPAM), acrylamide (AAm) and 2-hydroxyethyl methacrylate (HEMA). The structural and thermal properties of the resulting mixtures are evaluated by 1D and 2D NMR spectroscopy as well as differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). UV photocuring kinetics of the PE mixtures is evaluated via in situ photo-DSC and photorheology measurements. The PE mixtures cure rapidly and display storage moduli that are orders of magnitude greater than equivalent copolymers cured in an aqueous medium. The versatility of these PE systems is demonstrated through the addition of a photoswitchable spiropyran acrylate monomer, as well as applying the PE formulation as a stereolithography (SLA)-based 3D printing resin. Due to the hydrogen-bonding network in PE systems, 3D printing of the eutectic resin is possible in the absence of crosslinkers. The addition of a RAFT agent to reduce average polymer chain length enables 3D printing of materials which retain their shape and can be dissolved on demand in appropriate solvents.

Nanoparticle-Modified 3D-Printed Denture Base Resins: Influence of Denture Cleansers on the Color Stability and Surface Roughness In Vitro.

This study aimed to evaluate the influence of denture cleansers on the color, stability, and surface roughness of three-dimensional (3D)-printed denture base resins modified with zirconium dioxide nanoparticles (nano-ZrO2). A total of 440 specimens were fabricated using one heat-polymerized resin, and two 3D-printed resins (NextDent and ASIGA). According to the nano-ZrO2 content, the specimens for each resin were divided into five groups (0%, 0.5%wt, 1%wt, 3%wt, and 5%wt). Each concentration was divided into four subgroups (n = 10) based on the immersion solution (distilled water, sodium hypochlorite, Corega, and Fittydent) and immersion duration (360 and 720 days). The color changes (∆E00) and surface roughness (Ra, µm) of each specimen were measured at different time intervals (base line, 360 days, 720 days) using a spectrophotometer and a non-contact profilometer, respectively. The results were statistically analyzed using ANOVA and a post hoc Tukey's test (α = 0.05). Sodium hypochlorite showed the highest significant color change of all the denture base resins (p < 0.001). The average value of ΔE00 for sodium hypochlorite was significantly higher than the values for the other solutions (Fittydent, Corega, and water) (p < 0.001). Color stability was significantly affected by immersion time for all types of solutions except Corega (p < 0.001). All of the tested immersion solutions (distilled water, sodium hypochlorite, Corega, and Fittydent) showed a significant increase in the surface roughness of all the denture base resins (p < 0.05). Surface roughness was substantially increased by immersion time for all types of solution except Fittydent (p < 0.001). Denture cleansers can result in substantial color change and affect the surface roughness of unmodified and nanoparticle-modified denture base resins. Therefore, the selection of denture cleanser and appropriate types of material is critical for denture longevity.

Effects of post-curing duration on the mechanical properties of complex 3D printed geometrical parts

This study aims to assess the efficacy of post-curing guidance supplied by 3D printing resin manufacturers. Current guidance applies generically to all geometries with the caveat that post-curing should be extended for ‘large’ or ‘complex’ geometries but specific guidance is not provided.Two vat-polymerisation 3D printers (Form3B, Figure 4 Standalone) were used to print test models in 6 biocompatible resins (Pro Black, Med White, Med Amber, Biomed Black, Biomed White, Biomed Amber). The test model is of a complex geometry whilst also housing ISO 527 test specimens in concentric layers. Two separate intervals of curing were applied (100%, 500% stated guidance) creating different curing treatments of the specimens throughout the model. Post processed test models were disassembled and pull testing performed on each of the specimens to assess the mechanical properties.The analysis showed that extending the curing duration had significant effects on the mechanical properties of some materials but not all. The layers of the model had a significant effect except for elongation at break for the Med Amber material.This research demonstrates that generic post-curing guidance regarding UV exposures is not sufficient to achieve homogenous material strength properties for complex geometries. Large variations in mechanical properties throughout the models suggest some material was not fully-cured. This raises a query if such materials as originally marketed as biocompatible are fully cured and therefore safe to use for medical applications involving complex geometries.

Accuracy of soy-based resins for dental 3D printing.

To verify the accuracy of soy-based resins for dental three-dimensional (3D) printing. After conducting a power analysis, models of 10 consecutively treated patients were produced from four different resins using a dental 3D printer. Two of these resins were soy based and therefore biodegradable. These 20 models were measured manually with a caliper as well as digitally by software and compared based on measurement parameters in all three spatial axes. No statistically significant differences were found between the four different resins or between the manual and digital measurements. Soy-based resin seems to be a suitable material for orthodontic 3D printing and is a more environmentally friendly alternative to conventional dental resins. Digital model analysis seems to produce comparable results to manual measurement.

Effect of Postrinsing Times and Methods on Surface Roughness, Hardness, and Polymerization of 3D-Printed Photopolymer Resin.

This in vitro study investigated the effects of different postrinsing times and methods on the surface roughness, surface hardness, and degree of polymerization of materials manufactured via stereolithography (SLA). A total of 288 disk-shaped specimens were manufactured using an SLA three-dimensional (3D) printer. The specimens were randomly divided into nine groups (n = 32) based on rinsing times and methods. The groups were categorized into three rinsing methods: automated, ultrasonic, and hand washing, with rinsing times of 5, 10, and 15 minutes using a 99% isopropanol alcohol as a solvent. Linear roughness (Ra) and area roughness (Sa) were measured using a 3D confocal laser microscopy; the roughness morphology was evaluated by using scanning electron microscopy. Vickers hardness (VHN) tests were performed using a Vickers microhardness tester. Fourier-transform infrared spectrometry was used to determine the degree of conversion of treated specimens. Data were statistically analyzed using two-way analysis of variance. The post hoc Tukey tests were conducted to compare the differences between groups (p < 0.05). The choice of the rinsing time and method affected the surface properties of the SLA photopolymer resin. The 15 minutes of ultrasonic method exhibited the highest Ra scores (0.86 ± 0.1 µm), while the 15 minutes of automated method presented the highest Sa scores (1.77 ± 0.35 µm). For the VHN test, the 15 minutes of ultrasonic method displayed the highest VHN score (18.26 ± 1.03 kgf/mm2). For the degree of polymerization, the 15 minutes of automated method was initially identified as the most effective (87.22 ± 6.80). To facilitate the overall surface roughness, surface hardness, and degree of polymerization, the optimal choice of postprocessing rinsing time and method for achieving a clear photopolymer resin was determined to be the ultrasonic method with a rinsing time of 15 minutes.

Influence of different printing orientations and post-polymerization time on the translucency of three-dimensional (3D) printed denture base resins.

To evaluate the effect of different printing orientations and post-polymerization time with thermal cycling on the translucency of 3D-printed denture base resins. Heat-polymerized (HP) acrylic resin specimens were fabricated and 3D-printed denture base materials (NextDent, ASIGA, FormLabs) were printed with different printing orientations (0, 45, 90 degrees) and subjected to different post-polymerization times (15-, 30-, 60-, and 90-min). All specimens were polished and immersed in distilled water for 1day at 37°C. CIEDE2000 was used to measure the translucency parameters (TP00) before and after thermal cycling (5000 cycles) recording the color parameters (L*, a*, b*) against a black and white background using a spectrophotometer. k-factors ANOVA followed by post hoc Tukey's test (α=.05) was performed for statistical analysis. The k-factors ANOVA test showed a significant effect of resin material, post-polymerization time, and printing orientation on translucency (p<0.001). In comparison to HP, all 3D-printed resins showed lower translucency with all post-polymerization times and printing orientation (p<0.001) except FormLabs resin (p>0.05). For all 3D-printed resins, the translucency increased, with increasing the post-polymerization time (p<0.001) and 60- and 90-min showed the highest translucency. For printing orientation, 90 and 45 degrees significantly showed high translucency in comparison to 0 degrees (p<0.001). FormLabs showed significantly higher translucency when compared with NextDent and ASIGA per respective printing orientation and post-polymerization time. The translucency significantly decreased after thermal cycling for all tested resins (p<0.001). The findings of this study demonstrated that the translucency of 3D-printed resins is influenced by the printing orientation, post-polymerization time, and resin type. As a result, choosing a resin type, and printing orientation, with a longer post-polymerization time should be considered since it may improve the esthetic appearance of the 3D-printed resins.

Effect of polymerisation protocols on water sorption, solubility and hygroscopic expansion of fast-cure bulk-fill composite

ObjectiveThis study examines the effect of two light-curing protocols from a LED polywave light curing unit (LCU) on water sorption, solubility, and hygroscopic expansion of fast and conventional bulk-fill resin-based composites (RBCs) aged in distilled water for 120 d. MethodsThree bulk-fill RBCs materials were studied: Tetric PowerFill® (fast photo-polymerised composite) (TPF), Tetric EvoCeram bulk-fill (EVO), and GrandioSo x-tra bulk-fill (GSO) (conventional photo-polymerised composites). Specimens were prepared within a 3D-printed resin mold (8-mm diameter x 4-mm height) and light-cured from one side only with 2 modes of polywave LCU (Bluephase® PowerCure): 3 s mode and for 20 s in “Standard” mode. Water sorption and solubility were measured at fixed time intervals for 120 d of distilled water storage, then reconditioned to dry to measure desorption for 75 d, all at 37 ± 1 °C. Hygroscopic (volumetric) expansion was recorded at the same time intervals up to 120 d. Data were analysed through SPSS using Two-way ANOVA, One-way ANOVA, independent t-tests, and Tukey’s post-hoc correction tests (p < 0.05). ResultsTPF, when irradiated for 3 s demonstrated minimal water sorption (0.83%), solubility (1.01 μg/mm3), and least volumetric expansion (1.64%) compared to EVO and GSO. While EVO showed the highest water sorption (1.03%) and solubility (1.95 μg/mm3) at 3 s. GSO had the lowest sorption (0.67%) and (0.56%) in 3 s and 20 s protocols, respectively. Nevertheless, all the sorption and solubility data were within the ISO 4049 limits. SignificanceFor TPF, fast (3 s) polymerisation did not increase either water sorption or solubility, compared with 20 s irradiation. However, with the two comparative bulk-fill composites, fast cure increased water sorption by 15–25% and more than doubled solubility. These findings were consistent with the lesser volumetric expansions observed for Tetric PowerFill at both the fast and standard protocols, indicating its relative stability across polymerisation protocols.

Fracture load of chairside CAD-CAM veneers fabricated with pre-and fully crystalized lithium disilicate ceramics.

To evaluate the fracture load of chairside computer-aided design and computer-aided manufacturing (CAD-CAM) veneers fabricated with two conventional pre-crystallized and two fully crystallized lithium disilicate ceramic materials. Seventy-five chairside CAD-CAM veneers (15 specimens/group) for maxillary right central incisors were fabricated with different lithium disilicate brands: (1) IPS e.max CAD; (2) Amber Mill; (3) Cerec Tessera; (4) n!ce Straumann; and (5) GC Initial LiSi Block. Restorations were cemented with resin luting cement (Variolink Esthetic, Ivoclar) to 3D-printed resin dies. Bonded restorations received 5000 thermal cycles and then were loaded until fracture. Statistical analysis included One-Way ANOVA. Conventional pre-crystallized e.max CAD displayed the highest fracture load value (640 N), followed by fully-crystallized n!ce Straumann (547 N), pre-crystallized Cerec Tessera (503 N), pre-crystallized Amber Mill (476 N), respectively; fully-crystallized GC Initial LiSi Block (431 N) displayed the lowest values. When comparing the fracture load of recent lithium disilicate ceramic material to the e.max group, which acted as the control, significant differences were noted. The LiSi Block GC group, in particular, had considerably higher mean difference values (208.867, p < 0.001, 95% CI [89.63, 328.10]), as did the Amber Mill group (164.200, p = 0.002, 95% CI [44.96, 283.44]) and CEREC Tessera group (137.533, p = 0.016, 95% CI [18.30, 256.77]). The e.max and n!ce Straumann groups had no statistically significant differences in mean scores (92.933, p = 0.198, 95% CI [-26.30, 212.17]). These findings imply that the clinical performance of recent lithium disilicate veneers varies when compared to the e.max CAD group. The fracture load of chairside CAD-CAM lithium disilicate veneers for maxillary central incisors varies according to the type of ceramic brands. Conventional pre-crystallized e.max CAD displayed higher fracture load than the recent pre- and fully-crystallized lithium disilicate materials, emphasizing the significance of choosing the right product based on the desired clinical outcome.