Do the printing orientation angle and layer thickness influence the radiopacity of 3D-printed dental resins?

Aims: The purpose of this study was to evaluate the tensile strength of the soft-liner (Molloplast-B®) between the denture foundation made of 3D printed resin and traditional acrylic (PMMA). Materials and Methods: In this experiment, 60 acrylic specimens in the shape of reverse dumbbells were employed. The first group consisted of 24 specimens made from traditional acrylic polymethyl methacrylate (PMMA) (Vertex, Veracril, and Duradent) while the second group consisted of 24 specimens made from 3D printed resin (Dentona). The third group consisted of 12 samples that were packed at the dough stage of acrylic and soft liner at the same time. After that, the samples from the first and second groups were split in two, with one half receiving no surface treatment and the other half undergoing sandblasting. Every sample is separated into two halves with precise measurements. The thickest and thinnest sections were 80 mm in length (10 mm x 25 mm) and 8 mm x 15 mm, respectively, and were joined in the middle by the soft-liner material. The experiment's tensile strength was examined in two separate directions to ascertain the soft-liner material's strength of adhesion to the sample's chosen materials. Results: The data analysis of the tensile strength test revealed a statistically significant difference in the soft-liner adhesion strength between the 3D-printed acrylic resin with sandblast treatment (0.2133 ± 0.03939 kN/mm²) and the 3D-printed acrylic resin without surface treatment (0.1567 ± 0.04677 kN/mm²). Similar results were observed for conventional acrylic PMMA, where the sandblasted acrylic PMMA (0.0950 ± 0.03606 kN/mm²) exhibited significantly better bond strength compared to the untreated acrylic PMMA (0.0875 ± 0.02491 kN/mm²). Dough stage samples had better values complared to traditional acrylic (0.1483± 0.03689 kN/mm²). Conclusion: The results demonstrate that sandblast treatment significantly improves the soft-liner adhesion strength of both 3D-printed acrylic resin and conventional acrylic PMMA. Surface treatment enhances bond strength compared to untreated materials. These findings suggest that sandblasting is an effective method for improving adhesion in acrylic-based materials.

BackgroundThree-dimensional (3D) printing is increasingly used to fabricate dental restorations due to its enhanced precision, consistency and time and cost-saving advantages. The properties of 3D-printed resin materials can be influenced by the chosen printing orientation which can impact the mechanical characteristics of the final products. PurposeThe objective of this study was to evaluate the influence of printing orientation and artificial ageing on the Martens hardness (HM) and indentation modulus (EIT) of 3D-printed definitive and temporary dental restorative resins. MethodsDisk specimens (20 mm diameter × 2 mm height) were additively manufactured in three printing orientations (0°, 45°, 90°) using five 3D-printable resins: VarseoSmile Crownplus (VCP), Crowntec (CT), Nextdent C&B MFH (ND), Dima C&B temp (DT), and GC temp print (GC). The specimens were printed using a DLP 3D-printer (ASIGA MAX UV), while LavaTM Ultimate (LU) and Telio CAD (TC) served as milled control materials. Martens hardness (HM) and indentation modulus (EIT) were tested both before and after storage in distilled water and artificial saliva for 1, 30, and 90 days at 37 °C. Results90° printed specimens exhibited higher HM than the other orientations at certain time points, but no significant differences were observed in HM and EIT between orientations for all 3D-printed materials after 90 days of ageing in both aging media. LU milled control material exhibited the highest HM and EIT among the tested materials, while TC, the other milled control, showed similar values to the 3D printed resins. CT and VCP (definitive resins) and ND displayed higher Martens parameters compared to DT and GC (temporary resins). The hardness of the 3D-printed materials was significantly impacted by artificial ageing compared to the controls, with ND having the least hardness reduction percentage amongst all 3D-printed materials. The hardness reduction percentage in distilled water and artificial saliva was similar for all materials except for TC, where higher reduction was noted in artificial saliva. SignificanceThe used 3D printed resins cannot yet be considered viable alternatives to milled materials intended for definitive restorations but are preferable for use as temporary restorations.

Comparative Analysis of Monomer Elution, Polymerization Efficiency, Mechanical Properties and Biocompatibility of 3D-Printed Provisional and Permanent Dental Resins.

ObjectiveTo compare the physico-mechanical properties (microhardness, surface roughness, and flexural strength) of permanent 3D-printed dental resins with those of a resin nanoceramic computer-aided design and computer-aided manufacturing (CAD/CAM) block and a composite resin.MethodsFour groups were tested: composite resin (Clearfil Majesty Esthetic), resin nanoceramic CAD/CAM block (Cerasmart), and two 3D-printed resins (Saremco Crowntec, VarseoSmile Crown Plus). Disk- and bar-shaped specimens were prepared according to ISO standards. Microhardness (Vickers test), surface roughness (profilometer), and flexural strength (three-point bending test) were evaluated. Data were analyzed using analysis of variance and Tukey post hoc tests (p < 0.05).ResultsCerasmart showed the highest microhardness (85.53 ± 3.97) and flexural strength (184.45 ± 9.42), while Saremco Crowntec exhibited the lowest microhardness (38.63 ± 2.14). Clearfil Majesty had the highest surface roughness (1.24 ± 0.35). Although the measured flexural strength values of 3D-printed resins exceeded the ISO 4049 minimum threshold, several samples were close to or below the limit.ConclusionsWithin the limitations of this in vitro study, 3D-printed permanent resins exhibited mechanical properties comparable to conventional restorative materials in certain parameters, although inferior hardness values were observed compared to CAD/CAM blocks. Nevertheless, the present findings should be interpreted with caution, and further long-term clinical investigations are necessary before translating these results into clinical practice.

This study aimed to comparatively characterize the chemical composition of four commercial 3D-printed resin composites and quantify residual monomer elution profiles relevant to provisional and permanent fixed restorations. Two provisional resins (Temporary CB, Formlabs and NextDent C&B MFH) and two permanent 3D-printed resins (Saremco print CrownTec and VarseoSmile Crown plus) were analyzed. Unpolymerized resins underwent untargeted liquid chromatography-mass spectrometry (LC-MS) for compositional screening. Polymerized specimens were immersed in artificial saliva (37 °C, 72 h), followed by targeted quantitative LC-MS to quantify eluted residual monomers using certified standards calibration curves for HEMA, TEGDMA, UDMA, and Bis-EMA. Untargeted analysis detected 4125 chemical features, refined to 39 high-confidence resin-derived compounds across four 3D-printed resin composites. These were mainly monomers and derivatives, with some photoinitiators and additives. Compound diversity varied by material, with permanent Saremco and VarseoSmile showing the greatest variety. Bis-EMA predominated in Temporary CB, Saremco, and VarseoSmile, while UDMA was most abundant in NextDent, Saremco, and VarseoSmile. Quantitative analysis of monomer elution revealed that Temporary CB and VarseoSmile released the highest levels of Bis-EMA, NextDent showed the greatest elution of HEMA and UDMA, and VarseoSmile had the highest TEGDMA release. Saremco generally exhibited the lowest concentrations of all monitored monomers. These results demonstrate substantial variability in both composition and monomer elution profiles among commercial 3D-printed dental resins. Chemical composition and monomer elution in 3D-printed dental resins are highly material-specific. The marked variability, especially among permanent crown resins, underscores the need for material-specific biocompatibility testing to ensure long-term clinical safety. Material-specific differences in monomer elutions from 3D-printed dental resins may affect patient safety and restoration durability, underscoring the need for careful material selection and targeted biocompatibility testing in clinical practice.

This study aimed to evaluate the water sorption, solubility, and translucency of 3D-printed denture base resins (NextDent, FormLabs, and Asiga), compare them to heat-polymerized acrylic denture base resins, and assess their performance under the effects of thermal cycling. A total of 80 acrylic disc specimens were used in the current study, categorized into four groups (n = 10); in one group, the samples were fabricated conventionally with a heat-polymerizing process (control), while the other three groups were fabricated digitally from different 3D-printed reins (NextDent, FormLabs, and Asiga). Specimens were fabricated according to the manufacturers’ recommendations and immersed in distilled water for 48 h at 37 °C. Data on water sorption, solubility, and translucency measurements (T1) were obtained. All the specimens were subjected to 5000 thermal cycles, and then the measures were repeated using the same method (T2). Data analysis was attained via ANOVA and the post hoc Tukey test (α = 0.05). The type of resin significantly affected the values of water sorption, solubility, and translucency (p < 0.001). The water sorption of 3D-printed resins was increased significantly in comparison to control with or without a thermal cycling effect. In terms of solubility, a significant increase in 3D-printed resins before thermocycling was observed; however, after thermocycling, Asiga had a significantly low value compared to the other groups (p < 0.001). Thermal cycling increased the water sorption and solubility of all tested materials. In comparison to control, the translucency of the 3D-printed resins was significantly decreased (p < 0.001). The translucency was significantly decreased per material in terms of the thermal cycling effect (before and after). NextDent showed significantly low translucency values (p < 0.001) compared to the other groups. All 3D-printed resin groups had higher water sorption and solubility and lower translucency values in comparison to the heat-polymerized resin group. Regardless of resin types, thermal cycling adversely affected all tested properties.

Advances in additive manufacturing have enabled the fabrication of denture bases using three-dimensional (3D) printing technology; however, the mechanical properties of the resulting materials, particularly impact strength, are highly influenced by post-processing parameters such as curing time. This experimental laboratory study aimed to evaluate the effect of different curing time variations on the impact strength of 3D-printed denture base resin and to compare its performance with that of heat-polymerized acrylic resin (HPAR). A post-test only control group design was employed, in which specimens were divided into four groups consisting of 3D-printed resin with curing times of 4.5, 5.0, and 5.5 seconds, and a control group fabricated from HPAR. The results demonstrated that the 3D-printed resin cured for 5.0 seconds exhibited the highest mean impact strength (1.56 ± 0.14 kJ/m²), followed by the 4.5-second group (1.47 ± 0.09 kJ/m²), while the lowest value was observed in the 5.5-second curing group (1.28 ± 0.23 kJ/m²). In contrast, the HPAR group showed substantially higher impact strength than all 3D-printed resin groups, with a mean value of 2.99 ± 0.97 kJ/m². These findings indicate that curing time optimization significantly affects the impact strength of 3D-printed denture base resin; nevertheless, heat-polymerized acrylic resin remains superior in terms of mechanical toughness for denture base applications

3D printing is increasingly used in dentistry, with biocompatible resins playing a key role. This study compared the radioprotective properties of a commonly used 3D-printed resin (Formlabs surgical guide resin) with traditional heat-cured resin and examined the relationship between material thickness and radiation attenuation. The specimens consisted of 3D-printed and heat-cured resin specimens, each measuring 45 × 45 mm2, with five different thicknesses (6, 8, 10, 12, and 14 mm), totaling 100 samples. Both types of resin specimens underwent testing with 150 MU external beam radiation therapy (EBRT) and 400 cGy brachytherapy. Radiation experiments indicated that under EBRT conditions, there were no significant differences in radiation attenuation between the 3D-printed and heat-cured resins across all thickness groups. In brachytherapy, the attenuation of the 3D-printed resin was significantly lower than the heat-cured resin in the 6 mm and 8 mm groups. Specifically, attenuation rates were 48.0 ± 0.7 (3D-printed) vs. 45.2 ± 1.9 (heat-cured) in the 6 mm group, and 39.6 ± 1.3 vs. 37.5 ± 1.1 in the 8 mm group. Both resins showed significant positive linear correlations between thickness and attenuation (p < 0.001) within 6-14 mm. Thus, 3D-printed resin shows promising radioprotective properties and is a viable alternative to traditional heat-cured resin.

The purpose is to evaluate the effect of adding Halloysite Nanotubes (HNTs) on the flexural strength (FS), elastic modulus, and hardness of 3D-printed denture base resins (DBRs). A total of 160bar- and disk-shaped specimens were fabricated from 3D-printed resins (DentaBASE-ASIGA and Denture 3D+-NextDent), incorporating three concentrations of HNTs (0.3%-, 0.6%-, and 0.9%) in addition to one control group without HNTs addition. Specimens were designed to the required dimensions and printed according to the manufacturer's recommendations. The printed specimens were finished, polished, and then subjected to thermal cycling (5000 cycles). Flexural properties were measured using the 3-point bending fixture with a universal testing machine, and a Vickers hardness tester was used to assess the hardness. A scanning electron microscope (SEM) was used for fracture surface analysis and HNTs distribution. ANOVA and post hoc Tukey's test were used for data analysis (α=0.05). Adding HNTs to 3D-printed DBRs increased FS compared to the control group (p<0.001). Between HNTs-modified groups, 0.6% and 0.9% groups showed a significant increase in FS compared with the 0.3% group, while no significant difference was observed between 0.6% and 0.9% HNTs (p>0.05). The elastic modulus significantly increased by adding HNTs compared to the control group (p<0.001), while no significant differences in the elastic modulus were observed between HNTs-modified groups (p>0.05). SEM analysis revealed a ductile fracture mode for HNTs-modified groups. Compared to the control group, the hardness of 3D-printed resin increased with HNTs addition (p<0.001). Up to 0.6% HNTs, a significant increase in hardness was reported, while 0.9% significantly decreased the hardness compared with 0.6% HNTs (p<0.001). No significant differences were found between materials per concentration (p>0.05) when comparing materials. The FS, elastic modulus, and hardness of 3D-printed resins increased with the addition of HNTs. Regarding HNTs concentrations, 0.3% and 0.6% positively impacted the tested properties and could be recommended as an alternative to pure 3D-printed resins after testing other properties and evaluating the performance of HNTs-3D-printed nanocomposites.

Newly developed 3D-printed polymer materials are used for denture base fabrication. The aim of the present study was to evaluate the color stability of two new 3D-printed resins, a hard PPMA-based and a soft Urethane-based resin, in relation to a traditional heat-polymerized PMMA resin, which was used for comparison purposes. Specimens of the materials were immersed in five solutions (distilled water, red wine, black tea, coffee, and Coke®) for definite periods of time (one day, one week, and one month). The color measurements were carried out utilizing a spectrometer supported by a microscope and using special software. Color changes between immersion periods were calculated and statistically compared. The results showed that all types of resins were influenced during immersion periods. The heat-polymerized resin was influenced less than the others but with no significant difference to the 3D-printed hard PMMA resin. In respect to the materials compared, the discoloration effect for the 1 month immersion time was significantly more intense for the soft 3D-printed resin. In respect to the solutions’ staining effects, black tea and red wine significantly discolored all materials regardless of immersion periods. The new 3D-printed materials need further improvements for dental use.

Recent advances in three-dimensional (3D) printing have introduced new materials that can be utilized for dental restorations. Nonetheless, there are limited studies on the color stability of restorations using 3D-printed crowns and bridge resins. Herein, the color stability of conventional computer-aided design/computer-aided manufacturing (CAD/CAM) blocks and 3D-printing resins was evaluated and assessed for their degrees of discoloration based on material type, colorant types (grape juice, coffee, curry, and distilled water (control group)), and storage duration (2, 7, and 30 days) in the colorants. Water sorption, solubility, and scanning electron microscope (SEM) analyses were conducted. A three-way ANOVA analysis showed that all three factors significantly affected the color change of the materials. Notably, the discoloration (ΔE00) was significantly higher in all 3D printing resins (4.74–22.85 over the 30 days) than in CAD/CAM blocks (0.64–4.12 over the 30 days) following immersion in all colorants. 3D-printing resins showed color differences above the clinical limit (2.25) following storage for 7 days or longer in all experimental groups. Curry was the most prominent colorant, and discoloration increased in almost all groups as the storage duration increased. This study suggests that discoloration must be considered when using 3D printing resins for restorations.

The aim of this study was to evaluate the bond strength between two types of artificial teeth with a 3D-printed denture base resin using different bonding agents. Two types of artificial teeth were evaluated: 3D-printed (Cosmos TEMP) and prefabricated polymethylmethacrylate (Biotone) bonded to cylinders (2.5 mm in height and 5 mm in diameter) of 3D-printed denture bases (Cosmos Denture designing by Meshmixer and printed by Flashforge Hunter DLP Resin 3D Printer). Two combinations between denture base and artificial teeth were eveluated: Cosmos Denture - Biotone, n = 30, and Cosmos Denture - Cosmos TEMP, n = 30. For each combination, the specimens were randomly distributed according to the bonding agent: (1) autopolymerized acrylic resin-Duralay, n = 10; (2) 3D-printed resin Cosmos TEMP, n = 10; and (3) methylmethacrylate monomer (MMA) + 3D-printed resin Cosmos TEMP, n = 10, totaling 60 specimens. The application of MMA was done conditioning the tooth surface for 180 seconds; the other agents were applied on the same surface. The virtual design of the 3D-printed resin teeth was obtained by scanning the first maxillary molar of the prefabricated teeth as the same protocol of cylinders. The control group (n = 10) was a conventional heat-polymerized denture base resin (Lucitone 550) bonded to the prefabricated resin teeth (Biotone). The shear bond tests were performed by applying a perpendicular force to the artificial tooth - denture base resin, through a chisel at 1 mm/min until failure. Two-way ANOVA and Bonferroni post hoc tests (α = 0.05) were used for multiple comparisons. For the Biotone tooth, the bond strength was significantly higher using MMA + Cosmos TEMP (10.04 MPa), and similar to the control (11.84 MPa, p = 0.484). For the 3D-printed tooth (Cosmos TEMP), the bond strength using the agents Cosmos TEMP (9.57 MPa) and MMA + Cosmos TEMP (12.72 MPa) were similar to the control (11.84 MPa, p = 0.169 and p = 1, respectively), but different from each other (p = 0.016). From the results, it is recommended to use: MMA + Cosmos TEMP bonding agent for the Biotone tooth; and Cosmos TEMP or MMA + Cosmos TEMP bonding agents for the Cosmos TEMP tooth, both attached to the 3D-printed denture resin Cosmos Denture.

Effects of washing solution temperature on the biocompatibility and mechanical properties of 3D-Printed dental resin material

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.

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.