3D-printed Resin Research Articles

Effect of Material Selection and Different Fabrication Techniques on Marginal and Internal Fit of Metal Ceramic and All Ceramic Crowns (In vivo and In vitro study)

Purpose: Assess the effect of material selection as well as different fabrication techniques of metal ceramic (MC) and all ceramic crowns on their clinical outcomes, marginal and internal fit. Materials and methods: In vivo study(I); twenty- eight patients were provided with twenty-eight crowns restoring mandibular first molar tooth. Patients were distributed into 2 groups and 2 subgroups according to different materials and fabrication techniques: fourteen patients received MC crowns, group (I); seven patients received crowns with conventional casting of Co-Cr copings, subgroup (A) and seven patients received crowns with direct milling of Co-Cr copings, subgroup (B). Fourteen patients received IPS e.max press crowns, group (II); seven patients received crowns with conventional wax pattern, subgroup (A) and seven patients received crowns with 3D printing resin pattern, subgroup (B). The survival rate of these crowns was evaluated and statistically analyzed. In vitro study(II); one machined die was prepared to simulate crown preparation of mandibular first molar tooth. 60 crowns were constructed on die and divided into 2 groups (30 samples each) and 2 subgroups (15 samples each) according to different materials and fabrication techniques similar to in vivo study. Replica technique obtained to measure marginal and internal fit using Digital microscope. Results: The survival rate of MC and press crowns was 98% and 60% respectively. Press crowns and digital technique showed superior marginal and internal fit than MC crowns and conventional technique respectively. Conclusions: Material type and fabrication technique of MC and all ceramic crowns influence their clinical outcome, marginal and internal fit.

Chemical and Mechanical Tunability of 3D-Printed Dynamic Covalent Networks Based on Boronate Esters.

As the scope of additive manufacturing broadens, interest has developed in 3D-printed objects that are derived from recyclable resins with chemical and mechanical tunability. Dynamic covalent bonds have the potential to not only increase the sustainability of 3D-printed objects, but also serve as reactive sites for postprinting derivatization. In this study, we use boronate esters as a key building block for the development of catalyst-free, 3D-printing resins with the ability to undergo room-temperature exchange at the cross-linking sites. The orthogonality of boronate esters is exploited in fast-curing, oxygen-tolerant thiol-ene resins in which the dynamic character of 3D-printed objects can be modulated by the addition of a static, covalent cross-linker with no room-temperature bond exchange. This allows the mechanical properties of printed parts to be varied between those of a traditional thermoset and a vitrimer. Objects printed with a hybrid dynamic/static resin exhibit a balance of structural stability (residual stress = 18%) and rapid exchange (characteristic relaxation time = 7 s), allowing for interfacial welding and postprinting functionalization. Modulation of the cross-linking density postprinting is enabled by selective hydrolysis of the boronate esters to generate networks with swelling capacities tunable from 1.3 to 3.3.

Effect of Acrylic and Epoxy Hybrid Crosslinker on the Mechanical Strength of Photocurable Resin for 3D Printing

Effect of Acrylic and Epoxy Hybrid Crosslinker on the Mechanical Strength of Photocurable Resin for 3D Printing

Surgical Repositioning of an Inverted Developing Incisor Assisted by 3D Technology

Permanent central incisor impaction is very rare, and causes of impaction include adjacent supernumerary teeth, odontoma, and trauma. Surgical repositioning is a treatment option for teeth with ectopic eruption pathways. In this case report, an inverted developing maxillary central incisor was surgically repositioned at the initial stage of root development. Three dimensional (3D) virtual images were acquired using computed tomography, and a replica was produced by LCD-based masked stereolithography 3D printing. A resin for 3D printing was approved as a medical device and used as a 3D printing replica. Further, 3D technology has been found to be useful for successful tooth repositioning surgery.

Comparison of shrinkage according to thickness of photopolymerization resin for 3D printing

Comparison of shrinkage according to thickness of photopolymerization resin for 3D printing

Evaluation of flexural properties and reliability with photo-curing 3D printing resin according to the printing orientations

Evaluation of flexural properties and reliability with photo-curing 3D printing resin according to the printing orientations

3D Printed Polyurethane Reinforced Graphene Nanoplatelets

3D printing allows industries to scale the development from rapid prototyping to mass production in an easier manner. However, a typical photopolymers resin for stereolithography 3D printing possesses lower mechanical properties which incapable to meet certain industrial requirements for high impact applications. Hence, 0.1 to 2.0 wt.% of graphene nanoplatelets (GnP) were incorporated into photo-curable polyurethane (PU) based resin through digital light processing (DLP) 3D printing to evaluate its reinforcement effect. FTIR spectrum proves that significant characteristics of PU were still dominant upon the addition of GnP, indicating there was no chemical interaction between PU and GnP. The interfacial adhesion and the homogeneity of GnP in PU matrix were investigated through morphological analysis and the strength and stiffness of the 3D-printed composites. Results shows, tensile strength and Young’s Modulus of the PU/1%GnP composite had an increment of 21% and 24%, respectively when compared to neat PU resin. However, further increment of GnP reduced the mechanical properties because of interruption in UV curing during printing, hence leading to interfacial voids and defects on the printed specimens.

Reconfigurable Polymer Networks for Digital Light Processing 3D Printing.

To realize a wide range of applications using three-dimensional (3D) printing, it is urgent to develop 3D printing resins with different functions. However, the design freedom of the resin formulation is greatly limited to guarantee fast gelation during 3D printing. Herein, we report a reconfigurable polymer network that is compatible with digital light processing (DLP) 3D printing. The properties of the printed objects can be remanipulated by post-thermal treatment, during which the polymer network undergoes significant changes through the amidation of ester. The Young's modulus could be significantly reduced by 50 times. Specifically, a well-printed rigid part can be completely turned into a low-viscosity liquid. This strategy decouples the printing process and the final material properties, providing an efficient approach to print various functional objects.

Dimensional Accuracy of Dental Models for Three-Unit Prostheses Fabricated by Various 3D Printing Technologies.

Previous studies on accuracy of three-dimensional (3D) printed model focused on full arch measurements at few points. The aim of this study was to examine the dimensional accuracy of 3D-printed models which were teeth-prepped for three-unit fixed prostheses, especially at margin and proximal contact areas. The prepped dental model was scanned with a desktop scanner. Using this reference file, test models were fabricated by digital light processing (DLP), Multi-Jet printing (MJP), and stereo-lithography apparatus (SLA) techniques. We calculated the accuracy (trueness and precision) of 3D-printed models on 3D planes, and deviations of each measured points at buccolingual and mesiodistal planes. We also analyzed the surface roughness of resin printed models. For overall 3D analysis, MJP showed significantly higher accuracy (trueness) than DLP and SLA techniques; however, there was not any statistically significant difference on precision. For deviations on margins of molar tooth and distance to proximal contact, MJP showed significantly accurate results; however, for a premolar tooth, there was no significant difference between the groups. 3D color maps of printed models showed contraction buccolingually, and surface roughness of the models fabricated by MJP technique was observed as the lowest. The accuracy of the 3D-printed resin models by DLP, MJP, and SLA techniques showed a clinically acceptable range to use as a working model for manufacturing dental prostheses

Colour stability of 3D-printed resin orthodontic brackets.

To evaluate the colour stability of polymeric resins that could be used to 3D-print orthodontic brackets. In vitro, laboratory study. Disc-shaped specimens were fabricated via 3D printing using three resins: Dental LT; Dental SG; and Clear. Five conditions were evaluated for each resin (n = 10 per treatment per resin) to assess its corresponding effect on colour and translucency: immersion in (1) red wine, (2) coffee, (3) tea and (4) distilled water (control), and (5) exposure to accelerated aging. Colour and translucency measurements were made before and after exposure using a spectrophotometer. Mean colour differences (ΔE00) and changes in translucency parameter (ΔTP00) were calculated for each sample using the CIEDE2000 colour difference formula. Statistically significant effects of the resin material, the treatment condition and interactions effects of material and condition were observed for ΔE00 and ΔTP00 (P < 0.001). The most pronounced changes in colour (ΔE00) were a result of the staining effects of wine on all three resins, ranging from 14.5 ± 0.6 to 20.8 ± 1.2. Dental LT, Dental SG and Clear resins all showed changes in colour when exposed to certain staining agents. Dental SG and Clear resins exhibited changes in colour with aging, while the colour of Dental LT resin remained stable with aging. The colour changes of the resins investigated does not support their use in 3D-printed aesthetic bracket applications.

Mechanical Properties and Biocompatibility of Urethane Acrylate-Based 3D-Printed Denture Base Resin.

In this study, five urethane acrylates (UAs), namely aliphatic urethane hexa-acrylate (87A), aromatic urethane hexa-acrylate (88A), aliphatic UA (588), aliphatic urethane triacrylate diluted in 15% HDD (594), and high-functional aliphatic UA (5812), were selected to formulate five UA-based photopolymer resins for digital light processing (DLP)-based 3D printing. Each UA (40 wt%) was added and blended homogenously with ethoxylated pentaerythritol tetraacrylate (40 wt%), isobornyl acrylate (12 wt%), diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (3 wt%), and a pink acrylic (5 wt%). Each UA-based resin specimen was designed using CAD software and fabricated using a DLP 3D printer to specific dimensions. Characteristics, mechanical properties, and cytotoxicity levels of these designed UA-based resins were investigated and compared with a commercial 3D printing denture base acrylic resin (BB base) control group at different UV exposure times. Shore hardness-measurement data and MTT assays were analyzed using a one-way analysis of variance with Bonferroni’s post hoc test, whereas viscosity, maximum strength, and modulus were analyzed using the Kruskal–Wallis test (α = 0.05). UA-based photopolymer resins with tunable mechanical properties were successfully prepared by replacing the UA materials and the UV exposure times. After 15 min of UV exposure, the 5812 and 594 groups exhibited higher viscosities, whereas the 88A and 87A groups exhibited lower viscosities compared with the BB base group. Maximum flexural strength, flexural modulus, and Shore hardness values also revealed significant differences among materials (p < 0.001). Based on MTT assay results, the UA-based photopolymer resins were nontoxic. In the present study, mechanical properties of the designed photopolymer resins could be adjusted by changing the UA or UV exposure time, suggesting that aliphatic urethane acrylate has good potential for use in the design of printable resins for DLP-type 3D printing in dental applications.

Impact strength of 3D printed and conventional heat-cured and cold-cured denture base acrylics.

To evaluate and compare the impact strength of 3D-printed resin to conventionally fabricated denture bases of heat-cured and cold-cured acrylic resin. Denture base materials were evenly divided into three groups (n = 25 each; N = 75): (1) 3Dprinted material (Denture Base LP, Formlabs); (2) Heat-cured acrylic resin (Lucitone 199, Dentsply Sirona); and (3) cold-cured acrylic resin (Lucitone HIPA, Dentsply Sirona). The 3Dprinted specimens were designed through computer-aided design (CAD) software (Autodesk Meshmixer) with the dimensions 64 mm long, 12.7 mm wide, and 3.2 mm thick, then printed with a desktop stereolithography printer (Form 2, Formlabs). Heat-cured and cold-cured acrylic resin specimens were fabricated through conventional (compression and pouring) methods. The impact energy was read directly from the impact tester in joules, and the cross-sectional area of each specimen was used to calculate the impact strength in kJ/m2. Analysis of variance, Tukey multiple comparisons test, and a likelihood ratio α = .05 were conducted. The average mean impact strength was 8.9 kJ/m2 for heat-cured acrylic resin, 11.2 kJ/m2 for 3D-printed resin, and 14.9 kJ/m2 for cold-cured acrylic resin. Tukey multiple comparisons test showed that the impact strength for the cold-cured group was significantly greater than the 3D-printed resin and heat-cured acrylic resin groups. Within the limitations of this study, the cold-cured acrylic (Lucitone HIPA) showed the greatest impact strength, followed by 3D-printed resin (Denture Base LP) and conventional heat-cured denture base materials (Lucitone 199), respectively.

Mode of bond failure between 3D-printed denture teeth and printed resin base material: effect of fabrication technique and dynamic loading. An in-vitro study.

To evaluate the failure load of 3D-printed denture resin material and teeth before and after dynamic loading. A total of 40 specimens were fabricated following ISO/TS 19736 and were divided into two equal groups. In the test group, the cylindrical base and denture teeth were 3D printed separately and then luted together. In the control group, the specimens were fabricated from conventional heat-cured polymethyl methacrylate (PMMA) and commercially available denture teeth using the compression-molding technique. Ten specimens from each group were subjected to dynamic load of 50 N for 250,000 cycles in a chewing simulator. All specimens were subjected to static load of 50 N using Instron machine with a crosshead speed of 1 mm/minute until fracture. The fractured surfaces were analyzed using field emission scanning electron microscopy. The failure loads were calculated and compared using analysis of variance (P < .05). All specimens survived the loading, undergoing 250,000 cycles without fracture. The mean failure load was influenced by fabrication technique and was significantly higher for the 3D-printed test group (P = .028). 3D-printed teeth showed a mixed mode of fracture, whereas in the control group, the specimens showed cohesive fracture within the teeth. The fabrication technique has an influence on the mode of failure between acrylic teeth and resin base material. Cohesive failure in teeth was predominant in the conventional group, suggesting possibly higher bond strength between the teeth and resin base in this group. The observed failure modes reveal that both fabrication techniques exhibited satisfactory bond strength. Chewing simulation did not significantly influence the bond strength of any of the tested groups.

Influence of 3D-printing method, resin material, and sterilization on the accuracy of virtually designed surgical implant guides

Statement of problemThree-dimensional printing has introduced new manufacturing methods. However, information on the influence of the specific printing technology, material, sterilization, and the comparison between printing and milling on the accuracy of surgical guides is lacking. PurposeThe purpose of this in vitro study was to evaluate the influence of the manufacturing method (printing and milling), printing technology stereolithography (SLA) and digital light processing (DLP), material, and sterilization on the accuracy of digitally designed surgical implant guides. Material and methodsResin patient replicas with a single edentulous space were used to place 132 implants with digitally designed surgical guides. The accuracy of postoperative implant position was analyzed for the manufacturing method (printing and milling), resin materials, and preoperative autoclaving. To determine 3D accuracy, angular displacement, mean horizontal crestal, apical displacement, and the linear vertical displacement at the apex were calculated separately for each group (n=12). In addition, the surgical guides were qualitatively analyzed by using field emission scanning electron micrograph. ResultsThe postoperative angular deviation ranged from 0.76 ±0.52 degrees (Rapidshape D20II with NextDent SG) to 2.43 ±0.64 degrees (Form2 with NextDent SG) (P<.001). Linear horizontal displacement at the crest was smallest for Rapidshape D20II with 3Delta Guide (0.27 ±0.08 mm) and highest for Form2 with NextDent SG (0.54 ±0.10 mm) (P<.001). Linear horizontal displacement at the apex ranged from 0.36 ±0.10 mm (SolFlex 350 with V-Print SG) to 0.89 ±0.32 mm (Form2 with NextDent SG) (P<.001). Considering the vertical position displacement was no more than 0.43 ±0.07 mm (Form2 with NextDent SG) short of the apex, none of the implant tips were displaced apically. Preoperative autoclaving differentially impaired the accuracy of surgical guides. ConclusionsThe specific manufacturing technique, the 3D printing device, the resin material, and the application of preoperative sterilization all affected the accuracy of the postoperative implant position. Irrespective of the manufacturing method, all implants were placed within the commonly accepted safety distance.

Clinical Performance of Two Types of Primary Molar Indirect Crowns Fabricated by 3D Printer and CAD/CAM for Rehabilitation of Large Carious Primary Molars.

Objectives This randomized clinical trial aimed to evaluate clinical outcomes of two types of esthetic crowns fabricated using a three-dimensional (3D) dental printer and computer-aided design and manufacturing (CAD/CAM) system as an alternative full-coronal restoration for extensively carious pulp-treated primary molars. Materials and Methods Randomization was done for 50 lower primary molars in 50 child patients, split into two groups based on the fabrication method used: Group A: CAD/CAM crowns using polymethyl methacrylate (PMMA) blocks and Group B: 3D dental printed crowns using GC photopolymer resin. All crowns were evaluated at baseline and at 3rd, 6th, and 12th months using the U.S. Public Health Service criteria for gingival health, retention, and marginal integrity for both groups. Statistical Analysis The survival rate of 3D-printable crowns was 84% compared with 80% survival rate using CAD/CAM fabricated crowns at the end of the 12th-month follow-up. No statistically significant differences were noted in restoration failure. In the evaluation of gingival health between the two groups’ follow-up times, no statistically significant differences were noted at the 3rd- and 6th-month follow-ups, yet at the 12th month, statistically significant differences were noted ( p = 0.022) when comparing gingival health. No statistically significant differences were noted between the two groups when comparing marginal integrity scores in all the follow-up periods. Conclusion Resin crowns fabricated via 3D dental printer and PMMA crowns fabricated using CAD/CAM are acceptable esthetic choices in restoring pulp-treated primary molars with great marginal integrity and crowns retention. 3D-printed resin crowns showed less cementing failure and performed better regarding gingival response compared with PMMA crowns.

Conductive MXene/melamine sponge combined with 3D printing resin base prepared as an electromagnetic interferences shielding switch

With the rapid development of wireless communication and electronic devices, current electromagnetic interference (EMI) shielding materials cannot meet the demands of smart EMI shielding in the next generation of electronic equipment. Herein, we developed an intelligent EMI shielding switch to realize microwave shielding and transmitting functions for one material simultaneously. The EMI shielding switch is composed of MXene/melamine sponge, and 3D printed resin base. The EMI shielding switch can smartly regulate its absorption-dominant EMI SE from ~0 dB to ~43.1 dB in S-band through simply operation, to fully realize microwave transmitting and shielding functions simultaneously. The EMI shielding switch provides a novel way to fabricate efficient EMI shielding materials for actual wireless communication demands.

Influence of Vanillin Acrylate-Based Resin Composition on Resin Photocuring Kinetics and Antimicrobial Properties of the Resulting Polymers.

The investigation of the influence of vanillin acrylate-based resin composition on photocuring kinetics and antimicrobial properties of the resulting polymers was performed in order to find efficient photocurable systems for optical 3D printing of bio-based polymers with tunable rigidity, as well as with antibacterial and antifungal activity. Two vanillin derivatives, vanillin diacrylate and vanillin dimethacrylate, were tested in photocurable systems using phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide as a photoinitiator. The influence of vanillin acrylate monomer, amount of photoinitiator, presence and amount of dithiol, and presence of solvent on photocuring kinetics was investigated by real-time photoreometry. Polymers of different rigidity were obtained by changing the photocurable resin composition. The photocuring kinetics of the selected vanillin acrylate-based resins was comparable with that of commercial petroleum-based acrylate resins for optical 3D printing. Polymers based on both vanillin acrylates showed a significant antibacterial activity against Escherichia coli and Staphylococcus aureus. Vanillin diacrylate-based polymer films also demonstrated an antifungal activity in direct contact with Aspergillus niger and Aspergillus terreus. Vanillin diacrylate-based dual curing systems were selected as the most promising for optical 3D printing of bio-based polymers with antibacterial and antifungal activity.

Effect of Post-Curing Time on the Color Stability and Related Properties of a Tooth-Colored 3D-Printed Resin Material

Objective: This study investigated the effect of post-curing time on the color stability and related properties, such as degree of conversion (DC), surface roughness, water contact angle, water sorption (W sp ), and water solubility (W sl ) of 3D-printed resin for dental restorations. Materials and methods: The 3D-printed specimens were divided into four groups according to the post-curing time (0, 5, 10, and 20 min). Color changes (ΔE) of the specimens immersed in aging media were measured using a spectrophotometer at different aging times. The DC of the resin was measured using a FTIR. The surface roughness (Ra) of the resin immersed in coffee was measured at different aging times. Water contact angle was evaluated using the sessile drop method, and W sp and W sl were tested according to the ISO 4049:2019. Results: The ∆E values of the specimens immersed in coffee and red wine decreased with increasing post-curing time. As the post-curing time increased up to 10 min, the DC increased and water contact angle decreased. The Ra value of the group without post-curing (0 min) increased gradually for 30 days, except between 7 and 15 days. However, when the post-curing time increased to greater than 10 min, no apparent change in Ra value was detected. The W sp and W sl of the group without post-curing were significantly lower and larger than that of the other groups, respectively. Conclusions: The longer the post-curing time of the tooth-colored 3D-printed resin, the better the color stability. The post-curing time of the 3D-printed resin affected the DC, surface roughness after aging in the staining media, water contact angle, water sorption, and water solubility.

Color stability of 3D-printed denture resins: effect of aging, mechanical brushing and immersion in staining medium

PURPOSEThis in-vitro study evaluated and compared the color stability of 3D-printed and conventional heat-polymerized acrylic resins following aging, mechanical brushing, and immersion in staining medium.MATERIALS AND METHODSForty disc-shaped specimens (10 mm in diameter and 3 mm thick) were prepared from two 3D-printed [DentaBASE (DB) and Denture 3D+ (D3D)] and one conventional polymethylmethacrylate (PMMA) denture materials. The specimens were thermo-cycled, subjected to mechanical brushing, and were immersed in either coffee, lemon juice, coke, or artificial saliva (AS) to simulate one and two years of oral use. Color measurements of the specimens were recorded by a spectrophotometer at baseline (T0), and after one (T1) and two years (T2) of simulation. The color changes (∆E) were determined and also quantified according to the National Bureau of Standards (NBS) units. Descriptive statistics, followed by factorial ANOVA and Bonferroni post-hoc test (α=.05), were applied for data analysis.RESULTSThe independent factors, namely material, staining medium, and immersion time, and interaction among these factors significantly influenced ∆E (P<.009). Irrespective of the materials, treatments, and time, the highest and the lowest mean ∆Es were observed for PMMA in lemon juice (4.58 ± 1.30) and DB in AS (0.41 ± 0.18), respectively. Regarding the material type, PMMA demonstrated the highest mean ∆E (2.31 ± 1.37), followed by D3D (1.67 ± 0.66), and DB (0.85 ± 0.52), and the difference in ∆E between the materials were statistically significant (P<.001). All the specimens demonstrated a decreased color changes at T2 compared to T1, and this difference in mean ∆E was statistically significant (P<.001).CONCLUSIONThe color changes of 3D-printed denture resins were low compared to conventional heat polymerized PMMA. All the tested materials, irrespective of the staining medium used, demonstrated a significant decrease in ∆E values over time.

Additive manufacturing of intricate and inherently photocatalytic flow reactor components

Abstract A 2,1,3-benzothiadiazole-based photosensitiser has been successfully incorporated into a commercially available 3D printing resin and utilised to fabricate inherently photocatalytic flow reactor components. The freedom of design provided by additive manufacturing enabled the production of photoactive monolith structures with intricate architectures, imparting functionality for heterogeneous photocatalysis and interesting manipulation of fluid dynamics within a fixed bed reactor column. The resultant monoliths were applied and validated in the photosensitisation of singlet oxygen in aqueous media, under continuous flow conditions and visible light irradiation (420 nm). The photo-generated singlet oxygen cleanly converted furoic acid to the γ-lactone, 5-hydroxy-2(5H)-furanone, with a peak space-time yield of 2.34 mmol m−2 h−1 achieved using the Voronoi monolith.