3D printing restorative materials using a stereolithographic technique: a systematic review

The Effect of Stacking on the Accuracy of 3D-Printed Full-Arch Dental Models

The objective of this study was to assess the effect of stacking on the dimensional and full-arch accuracy of 3D-printed models, utilising a standardised assessment methodology. A previously validated methodology involving a standard tessellation language image (STL) reference model, comprising seven spheres on a horseshoe base resembling a dental arch, was used. Six 3D-designed STL models were prepared, optimised, and stacked horizontally using 3D Sprint software. The stacking file was transferred to the NextDent 5100 printer to build the physical models. To assess accuracy, a coordinate measuring machine (CMM) measured the diameter of the spheres n=210, and twenty-one vectors extended between the centres of each of the seven spheres (n = 630). When compared to the reference model, significant differences were observed for dimensional (p = 0.006) and full-arch accuracy (p = 0.006) for all stacked models. Additionally, significant differences were observed between the stacked models for the dimensional accuracy between the posterior (p = 0.015), left posterior (p = 0.005) and anteroposterior (p = 0.002). The maximum contraction was observed in the fourth stacked model, which demonstrated the highest median deviation and least precision within the full-arch (MD = 666 μm, IQR = 55 μm), left posterior (MD = 136 μm, IQR = 12 μm), posterior (MD = 177 μm, IQR = 14 μm) and anteroposterior (MD = 179 μm, IQR = 16 μm) arch segments. In general, the anterior and left posterior arch segments recorded the highest contractions with a median deviation of 34 μm and 29 μm, and precision of 32 μm and 22 μm, respectively. Statistically significant differences were observed between the stacked models in terms of dimensional accuracy that were within clinically acceptable thresholds. The greatest contraction was noted in the fourth model, displaying the least full-arch accuracy compared to the other models. Stacked, additively manufactured, full arch models are a viable alternative for diagnostic, orthodontic, and single-unit prosthodontic applications. In contrast, caution should be exercised when utilising stacked models for full arch high accuracy prosthodontic applications. Further research is needed to assess the impact of additional variables including different printers and resins.

Obturator Manufacturing for Oronasal Fistula after Cleft Palate Repair: A Review from Handicraft to the Application of Digital Techniques

An oronasal fistula (ONF) is an abnormal structure between the oral and nasal cavities, which is a common complication of cleft palate repair due to the failure of wound healing. When some patients with ONF are unsuitable for secondary surgical repair, the obturator treatment becomes a potential method. The objectives of the obturator treatment should be summarized as filling the ONF comfortably and cosmetically restoring the dentition with partial function. The anatomy of patients with cleft palate is complex, which may lead to a more complex structure of the ONF. Thus, the manufacturing process of the obturator for these patients is more difficult. For performing the design and fabrication process rapidly and precisely, digital techniques can help, but limitations still exist. In this review, literature searches were conducted through Medline via PubMed, Wiley Online Library, Science Direct, and Web of Science, and 122 articles were selected. The purpose of this review was to introduce the development of the obturator for treating patients with ONF after cleft palate repair, from the initial achievement of the obstruction of the ONF to later problems such as fixation, velopharyngeal insufficiency, and infection, as well as the application of digital technologies in obturator manufacturing.

Assessing the physical and mechanical properties of 3D printed acrylic material for denture base application

OBJECTIVE

Three-dimensional (3D) printing is increasingly being utilised in the dental field because of its time-saving potential and cost effectiveness. It enables dental practitioners to eliminate several fabrication steps, achieve higher precision, and attain consistency in complex prosthetic models. The properties of 3D-printed resin materials can be affected by many factors, including the printing orientation (PO) and insufficient post-curing time (CT). This study aimed to investigate the effect of PO and CT on the mechanical and physical properties of a 3D-printed denture base resin (NextDent).

METHODS

3D-printed specimens were fabricated in 0°, 45°, and 90° POs, followed by three CTs (20, 30, and 50 min). The microhardness was tested using a Vickers hardness test, while the flexural property was evaluated using a three-point bending test. Sorption and solubility were measured after the specimens had been stored in an artificial saliva for 42 days, and the degree of conversion during polymerisation was analysed using Fourier Transform Infra-red (FTIR) spectroscopy.

RESULTS

The flexural strength of the material significantly increased (p < 0.05) when the printing orientation was changed from 0° to 90°. A similar increase was observed in the hardness, degree of conversion, and water sorption results. In general, no significant difference (p > 0.05) in any of the tested properties was found when the post-curing times were increased from 20 to 50 min.

SIGNIFICANCE

The highest physical and mechanical properties of the 3D-printed denture base resin can be obtained by printing vertically (90° angle to the platform base). The minimal post-curing time to achieve ideal results is 30 min, as further curing will have no significant effect on the properties of the material.

Clinical Application of Digital 3D Reconstruction and 3D Printing Technology in Endometrial Cancer (EC) Surgery

Aims

We use CTA and magnetic resonance data to use digital three-dimensional reconstruction and 3D printing technology to reproduce the solid replication of the uterus and surrounding tissues in vitro, fully evaluate the adjacency of tumor tissues with surrounding important organs, blood vessels, and lymph nodes, and reduce the impact. The normal organ structure and function of the surgeon can shorten the operation time, reduce the bleeding during the operation, and reduce the perioperative complications of the patient to improve the prognosis of the patient.

Materials and Methods

Select 40 EC patients and divide them into group A (3D reconstruction data is transmitted to 3D printing equipment according to the results of CTA and MRI examination, and a 3D model is printed out according to the ratio of 1 : 1 for evaluation and judgment before surgery) and group B (according to MRI imaging examination, there were 20 cases each). Different surgical conditions, quality of life, adverse reactions, and clinical efficacy were evaluated in each group.

Results

The operation time, the time of the first anus exhaust, the hospitalization time after the operation, and the blood loss of the operation in group A were significantly lower than those in group B. Statistics showed that the difference was significant (P < 0.05). The quality of life scores of emotion, cognition, society, and overall health of group A were significantly higher than those of group B, while physical score, fatigue, nausea, vomiting, and pain were lower than those of group B, which were statistically significant (P < 0.05). Both groups of patients had complications after the operation, and they were asked to be followed up at the outpatient clinic 3 months after the operation. All patients recovered well. There were 19 and 18 patients in groups A and B, respectively, complaining of improvement in clinical symptoms, and the difference was not statistically significant (P < 0.05).

Conclusion

With the support of digital three-dimensional reconstruction and 3D printing technology, complex operations can be accurately performed, improving the efficacy and safety of patients after EC surgery, improving patient outcomes and quality of life, improving EC positioning accuracy, and reducing tumor residue.

Color and optical properties of 3D printing restorative polymer-based materials: A scoping review

OBJECTIVE

Color and optical properties are particularly crucial to mimic natural tooth. This scoping review aimed to present an overview of the literature published on color and optical properties of 3D printing restorative polymer-based materials. The literature search was performed in MED-LINE/Pubmed, Scopus and Web of Science.

MATERIALS AND METHODS

The literature search was conducted in the three databases based on the question: "Are the optical properties and color adequately reported on polymer-based 3D printing dental restorative materials studies?" with no restriction on year of publication. Data were reported and synthesized following PRISMA-ScR statement.

RESULTS

Nine studies fit the inclusion criteria. Five studies focused on evaluating only color stability; three articles assessed the color stability along with mechanical and morphological properties and only one study compared color parameters of 3D printed to conventional polymers. Two studies evaluated translucency parameter and no study was found evaluating scattering, absorption, and transmittance.

CONCLUSIONS

Color and optical properties of 3D printed polymers that can be used in restorative dentistry are not adequately evaluated and characterized. Future studies on the influence of experimental printing conditions should include these physical properties to assist on improving esthetics.

CLINICAL SIGNIFICANCE

This review shows the scarce literature existing on color and optical properties of 3D printing restorative polymer-based materials. These properties and their study are of outmost importance to create materials that mimic natural tooth to allow clinicians to obtain esthetically pleasant restorations.

The accuracy comparison of 3D-printed post and core using castable resin and castable wax resin

PURPOSE

The purpose of this research was to compare the accuracy of three dimensionally (3D) printed post and core fabricated with two different materials: reinforced wax and castable resin.

METHODS AND METHODS

Fifteen extracted single root central incisors were selected. Root canal treatment and tooth preparation for crown were performed on all teeth. Eleven millimeters post space was created with standardized prefabricated fiber post drill. Polyvinylsiloxane impression material was used for root canal impressions. Each impression was then 3D scanned using an extraoral scanner and cast posts and cores were designed using 3Shape software. The digitally designed post and cores were 3D printed with two different materials: castable wax resin and resin. The castable resin patterns were scanned before and after complete polymerization. The wax patterns were also scanned. Digital volumetric measurement using Geomagic® Control X࣪ software was performed to determine accuracy.

RESULTS

The printed post and core had reduced volume (16.09 ±3.839 mm³ ) compared to the digital design (17.828 ±3.904, p<0.05). Before complete polymerization, the accuracy of 3D printed resin pattern (16.464 ±3.017) was found to be superior to post and core printed with wax (16.193 ±3.018, p<0.05). However, no volume difference was found between completely polymerized resin (16.09 ±3.839) and wax (16.044±3.834, p = 1).

CONCLUSION

3D printed post and core showed significant volume shrinkage from the digital files used to create them. However, different materials have no effect on the accuracy of 3D printed post and core. This article is protected by copyright. All rights reserved.

New Materials and Their Applications: Perspectives in Restorative Dentistry and Endodontics

"New Materials and Their Application: Perspectives in Restorative Dentistry and Endodontics" is a new open Special Issue of Materials, which aims to publish original and review articles on novel scientific research that closely relates to new dental materials and their synthesis, function, characteristics, and applications [...].

Prospect and retrospect of 3D bio-printing

3D bioprinting has become a popular medical technique in recent years. The most compelling rationale for the development of 3D bioprinting is the paucity of biological structures required for the rehabilitation of missing organs and tissues. They're useful in a multitude of domains, including disease modelling, regenerative medicine, tissue engineering, drug discovery with testing, personalised medicine, organ development, toxicity studies, and implants. Bioprinting requires a range of bioprinting technologies and bioinks to finish their procedure, that Inkjet-based bioprinting, extrusion-based bioprinting, laser-assisted bioprinting, stereolithography-based bioprinting, and in situ bioprinting are some of the technologies listed here. Bioink is a 3D printing material that is used to construct engineered artificial living tissue. It can be constructed solely for cells, but it usually includes a carrier substance that envelops the cells, then there's Agarose-based bioinks, alginate-based bioinks, collagen-based bioinks, and hyaluronic acid-based bioinks, to name a few. Here we presented about the different bioprinting methods with the use of bioinks in it and then Prospected over various applications in different fields.

Guide for starting or optimizing a 3D printing clinical service

Three-dimensional (3D) printing has applications in many fields and has gained substantial traction in medicine as a modality to transform two-dimensional scans into three-dimensional renderings. Patient-specific 3D printed models have direct patient care uses in surgical and procedural specialties, allowing for increased precision and accuracy in developing treatment plans and guiding surgeries. Medical applications include surgical planning, surgical guides, patient and trainee education, and implant fabrication. 3D printing workflow for a laboratory or clinical service that produces anatomic models and guides includes optimizing imaging acquisition and post-processing, segmenting the imaging, and printing the model. Quality assurance considerations include supervising medical imaging expert radiologists' guidance and self-implementing in-house quality control programs. The purpose of this review is to provide a workflow and guide for starting or optimizing laboratories and clinical services that 3D-print anatomic models or guides for clinical use.

Investigation of the marginal fit of a 3D-printed three-unit resin prosthesis with different build orientations and layer thicknesses

PURPOSE

The purpose of this study was to analyze the marginal fit of three-unit resin prostheses printed with the stereolithography (SLA) method in two build orientations (45°, 60°) and two layer thicknesses (50 µm, 100 µm).

MATERIALS AND METHODS

A master model for a three-unit resin prosthesis was designed with two implant abutments. Forty specimens were printed using an SLA 3D printer. The specimens were printed with two build orientations (45°, 60°), and each orientation was printed with two layer thicknesses (50 µm, 100 µm). The marginal fit was measured as the marginal gap (MG) and absolute marginal discrepancy (AMD), and MG and AMD measurements were performed at 8 points per abutment, for 16 points per specimen. All statistical analyses were performed using SPSS software. Two-way analysis of variance (ANOVA) was separately performed on the MG and AMD values of the build orientations and layer thicknesses. Moreover, one-way ANOVA was performed for each point within each group.

RESULTS

The margins of the area adjacent to the pontic showed significantly high values, and the values were smaller when the build orientation was 45° than when it was 60°. However, the margin did not differ significantly according to the layer thicknesses.

CONCLUSION

The marginal fit of the three-unit resin prosthesis fabricated by the SLA 3D method was affected by the pontic. Moreover, the marginal fit was affected by the build orientation. The 45° build orientation is recommended.

Color alterations, flexural strength, and microhardness of 3D printed resins for fixed provisional restoration using different post-curing times

OBJECTIVES

To evaluate the effect of post-curing times on the color change, flexural strength (FS), modulus (FM) and microhardness at different depths of four 3D printed resins.

MATERIALS AND METHODS

A characterization of the light emitted by 3D-resin post-curing unit (Wash and Cure 2.0, Anycubic) was performed. The tested 3D printed resins were Cosmos Temp3D (COS), SmartPrint BioTemp (SM) Resilab3D Temp (RES) and Prizma3D BioProv (PRI) were evaluated under five different post-curing conditions (no post-curing or 5-, 10-, 15, and 20 min of post-curing). For color change analysis, 10 mm diameter x 1 mm thick discs (n = 7) were printed, and the luminosity, color and translucency were measured before post-curing as control, and repeatedly after 5 min cycles of post-curing until a total of 20 min was reached for ΔE₀₀ [CIED2000 (1:1:1)] calculation. For FS and FM, 25 × 2×2 mm (n = 10, for each post-curing time) 3D printed bars were subjected to a 3-point being test. Knoop microhardness (KHN) was measured transversally on 5 × 5×5 mm blocks (n = 10, for each post-curing time). Color results were analyzed by one-way repeated measures ANOVA (factor: color change). FS and FM were analyzed by two-way ANOVA (factors: Material*Post-Curing Time). KHN was analyzed individually for each material by two-way ANOVA (factors: Depth*Post-Curing Time).

RESULTS

The post-curing time significantly influenced the ΔE_00, FS, FM and KHN of all the evaluated materials. COS and SMA presented ΔE₀₀ values above the acceptability threshold after 5 and 10 min of post-curing, respectively. The FS of RES reached a plateau after 5 min of post-curing, and for PRI and SMA, the FS stabilized after 10 min of post-curing. The post-curing process improved the KHN of the tested materials, and longer exposure periods were associated to higher KHN values at all the evaluated depths.

SIGNIFICANCE

A fine adjustment of the post-curing time is crucial to produce adequate mechanical properties in 3D-printed restorative resins, while minimizing the color alterations on the restorations. For the evaluated resins, 5-10 min of post-curing will result in adequate mechanical properties, without affecting the acceptability in the color of the material. However, the results are material-dependent, and evaluation of each specific resin is advised.

Recent Trends in Advanced Photoinitiators for Vat Photopolymerization 3D Printing

3D printing has revolutionized the way of manufacturing with a huge impact on various fields, in particular biomedicine. Vat photopolymerization-based 3D printing techniques such as stereolithography (SLA) and digital light processing (DLP) attracted considerable attention owing to their superior print resolution, relatively high speed, low cost and flexibility in resin material design. As one key element of the SLA/DLP resin, photoinitiators or photoinitiating systems have experienced significant development in recent years, in parallel with the exploration of 3D printing (macro)monomers. The design of new photoinitiating systems can not only offer faster 3D printing speed and enable low-energy visible light fabrication, but also can bring new functions to the 3D printed products and even generate new printing methods in combination with advanced optics. This review evaluates recent trends in the development and application of advanced photoinitiators and photoinitiating systems for vat photopolymerization 3D printing, with a wide range of small molecules, polymers and nanoassemblies involved. Personal perspectives on the current limitations and future directions are eventually provided. This article is protected by copyright. All rights reserved.

Compressive and Flexural Strength of 3D-Printed and Conventional Resins Designated for Interim Fixed Dental Prostheses: An In Vitro Comparison

A provisionalization sequence is essential for obtaining a predictable final prosthetic outcome. An assessment of the mechanical behavior of interim prosthetic materials could orient clinicians towards selecting an appropriate material for each clinical case. The aim of this study was to comparatively evaluate the mechanical behavior—with compressive and three-point flexural tests—of certain 3D-printed and conventional resins used to obtain interim fixed dental prostheses. Four interim resin materials were investigated: two 3D-printed resins and two conventional resins (an auto-polymerized resin and a pressure/heat-cured acrylic resin). Cylindrically shaped samples (25 × 25 mm/diameter × height) were obtained for the compression tests and bar-shaped samples (80 × 20 × 5 mm/length × width × thickness) were produced for the flexural tests, observing the producers’ recommendations. The resulting 40 resin samples were subjected to mechanical tests using a universal testing machine. Additionally, a fractographic analysis of failed samples in bending was performed. The results showed that the additive manufactured samples exhibited higher elastic moduli (2.4 ± 0.02 GPa and 2.6 ± 0.18 GPa) than the conventional samples (1.3 ± 0.19 GPa and 1.3 ± 0.38 GPa), as well as a higher average bending strength (141 ± 17 MPa and 143 ± 15 MPa) when compared to the conventional samples (88 ± 10 MPa and 76 ± 7 MPa); the results also suggested that the materials were more homogenous when produced via additive manufacturing.

Partial Biodegradable Blend with High Stability against Biodegradation for Fused Deposition Modeling

This research presents a partial biodegradable polymeric blend aimed for large-scale fused deposition modeling (FDM). The literature reports partial biodegradable blends with high contents of fossil fuel-based polymers (>20%) that make them unfriendly to the ecosystem. Furthermore, the reported polymer systems neither present good mechanical strength nor have been investigated in vulnerable environments that results in biodegradation. This research, as a continuity of previous work, presents the stability against biodegradability of a partial biodegradable blend prepared with polylactic acid (PLA) and polypropylene (PP). The blend is designed with intended excess physical interlocking and sufficient chemical grafting, which has only been investigated for thermal and hydrolytic degradation before by the same authors. The research presents, for the first time, ANOVA analysis for the statistical evaluation of endurance against biodegradability. The statistical results are complemented with thermochemical and visual analysis. Fourier transform infrared spectroscopy (FTIR) determines the signs of intermolecular interactions that are further confirmed by differential scanning calorimetry (DSC). The thermochemical interactions observed in FTIR and DSC are validated with thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) is also used as a visual technique to affirm the physical interlocking. It is concluded that the blend exhibits high stability against soil biodegradation in terms of high mechanical strength and high mass retention percentage.

Application of the Digital Workflow in Orofacial Orthopedics and Orthodontics: Printed Appliances with Skeletal Anchorage

As digital workflows are gaining popularity, novel treatment options have also arisen in orthodontics. By using selective laser melting (SLM), highly customized 3D-printed appliances can be manufactured and combined with preformed components. When combined with temporary anchorage devices (TADs), the advantages of the two approaches can be merged, which might improve treatment efficacy, versatility, and patient comfort. This article summarizes state-of-the-art technologies and digital workflows to design and install 3D-printed skeletally anchored orthodontic appliances. The advantages and disadvantages of digital workflows are critically discussed, and examples for the clinical application of mini-implant and mini-plate borne appliances are demonstrated.

Surface Roughness and Bond Strength of Resin Composite to Additively Manufactured Zirconia with Different Porosities

PURPOSE

To investigate the bond strength of resin cement to additively manufactured (AM) zirconia with different porosities when compared to milled zirconia.

MATERIALS AND METHODS

A 12 × 5 mm disk virtual design file was used to fabricate a total of 48 disks divided into 4 groups: 3 groups were AM with different porosities including 0%-porosity (AMZ0 group), 20%-porosity (AMZ20 group), and 40%-porosity (AMZ40 group), and 1 milled zirconia (control or CNCZ group). The dimensions of all specimens were measured using a digital caliper. A 3D- confocal laser scanner was used to analyze surface morphology and measure the surface roughness (Sa), followed by SEM analysis. Tensile bond strength of composite resin cement to specimens was measured before and after aging procedures using a universal testing machine (n = 10). Failure modes were evaluated under a light microscope. Volumetric change data was analyzed using one-way ANOVA, and two-way ANOVA was used to compare bond strength values (α = 0.05).

RESULTS

There was a significant difference in volumetric changes among the groups. The CNCZ group showed the least changes in diameter 0.027 ± 0.029 mm and thickness 0.030 ± 0.012 mm and AM zirconia with 40% porosity showed the most volumetric changes in diameter 5.237 ± 0.023 mm. ANOVA test indicated an overall significant difference in surface roughness across all groups (F = 242.6, p < 0.001). The CNCZ group showed the highest mean Sa of 1.649 ± 0.240 µm, followed by AMZ40 group with Sa of 0.830 ± 0.063 µm, AMZ20 group with Sa of 0.780 ± 0.070 µm, and the AMZ0 group with Sa of 0.612 ± 0.063 µm. Two-way ANOVA showed significant difference in bond strength between the CNCZ group 12.109 ± 3.223 MPa and the AMZ0 group 8.629 ± 0.914 MPa, with significant pretest failures in specimens with porosities. Thermal cycling methods reduced the bond strength non-significantly in CNCZ group with no effect in the AMZ0 group.

CONCLUSION

Milled zirconia had a higher surface roughness and bond strength to composite resin cement than AM zirconia, and porosities in AM zirconia decreased the bond strength with significant pretest failures.

Effect of denture cleansers on the surface properties and color stability of 3D Printed denture base materials

OBJECTIVES

To evaluate the effect of denture cleansers on surface roughness, hardness and color stability of 3D-printed resins compared to heat-polymerized resins.

METHODS

Acrylic specimens (N=160) were prepared using one heat-polymerized (HP) and three 3D-printed denture base resins. Specimens per material were randomly divided into four groups (n = 10) according to immersion solutions as follows: distilled water (DW), sodium hypochlorite (NaOCl), effervescent tablet 1 or effervescent tablet 2. Color changes (∆E) were measured using a spectrophotometer. Surface roughness (Ra, µm) and microhardness were evaluated. The results were analyzed using one- and three-way ANOVA with Tukey's post hoc test (α = 0.05).

RESULTS

After 360 days of cleaning protocols, we observed a significant increase in the surface roughness of tested materials (P<0.001). Hardness values significantly decreased in all groups (P<0.001), except HP and ND specimens, cleaned with effervescent tablet 1 (P>0.05) and AS specimens with effervescent tablet 2 (P=0.051). According to the National Bureau of Standards (NBS) score, all denture base specimens had 'perceivable' to 'extremely marked' color change after immersion in NaOCl, while immersion in effervescent tablets 1 and 2 resulted in a 'slight' to 'marked' color change.

CONCLUSION

3D-printed denture bases exhibited changes in surface roughness, hardness and color of 3D-printed dentures similar to HP denture base material. The use of denture cleansers resulted in a time-dependent increase in surface roughness and a decrease in hardness. The color change was significant with NaOCl, while effervescent denture cleansers produced a minimal color difference.

CLINICAL SIGNIFICANCE

Denture cleansers seem to influence surface properties over time. The degree of impact is mainly dependent on the type of cleanser selected, regardless of the type of denture base material.

A new trend of using poly(vinyl alcohol) in 3D and 4D printing technologies: Process and applications

Recently, 3D/4D printing technologies have been the researchers' interest, and they are getting improved more important. They are applicable in various fields like medical fields, pharmaceutics, construction, tissue engineering, dentistry, water treatment, etc. These technologies overcame the difficulty of the conventional methods in producing complicated structures. They can be fed by different materials such as nanomaterials, smart polymers, responsive polymers, metamaterials, synthetic polymers, natural polymers, and so forth. One of the smart and stimuli-responsive polymers is poly(vinyl alcohol) (PVA). In addition to numerous applications of PVA like medicine, environmental fields, etc., researchers are showing a tendency to use PVA in 3D/4D printing technologies. The main reasons for PVA's increased interest in 3D/4D printing technologies are suitable flowability, stimuli-responsivity, extrudability, biocompatibility, biodegradability, cost-effectiveness, and other features. This review aims to introduce the 3D/4D printing technologies' knowledge and then the applications of PVA as a feed in these novel technologies.

Cytotoxicity, Colour Stability and Dimensional Accuracy of 3D Printing Resin with Three Different Photoinitiators

Biocompatibility is important for the 3D printing of resins used in medical devices and can be affected by photoinitiators, one of the key additives used in the 3D printing process. The choice of ingredients must be considered, as the toxicity varies depending on the photoinitiator, and unreacted photoinitiator may leach out of the polymerized resin. In this study, the use of ethyl (2,4,6-trimethylbenzoyl) phenylphosphinate (TPO-L) as a photoinitiator for the 3D printing of resin was considered for application in medical device production, where the cytotoxicity, colour stability, dimensional accuracy, degree of conversion, and mechanical/physical properties were evaluated. Along with TPO-L, two conventional photoinitiators, phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide (BAPO) and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO), were considered. A total of 0.1 mol% of each photoinitiator was mixed with the resin matrix to prepare a resin mixture for 3D printing. The specimens were printed using a direct light processing (DLP) type 3D printer. The 3D-printed specimens were postprocessed and evaluated for cytotoxicity, colour stability, dimensional accuracy, degree of conversion, and mechanical properties in accordance with international standards and the methods described in previous studies. The TPO-L photoinitiator showed excellent biocompatibility and colour stability and possessed with an acceptable dimensional accuracy for use in the 3D printing of resins. Therefore, the TPO-L photoinitiator can be sufficiently used as a photoinitiator for dental 3D-printed resin.

The Influence of Microstructure on the Flexural Properties of 3D Printed Zirconia Part via Digital Light Processing Technology

In recent years, additive manufacturing of ceramics is becoming of increasing interest due to the possibility of the fabrication of complex shaped parts. However, the fabrication of a fully dense bulk ceramic part without cracks and defects is still challenging. In the presented work, the digital light processing method was introduced for fabricating zirconia parts. The flexural properties of the printed zirconia were systematically investigated via a three-point bending test with the digital image correlation method, scanning electron microscopy observation and fractography analysis. Due to the anisotropy of the sample, the bending deformation behaviors of the zirconia samples in the parallel and vertical printing directions were significantly different. The flexural strength and the related elastic modulus of the samples under vertical loading were higher than that of the parallel loading, as the in-plane strength is higher than that of the interlayer strength. The maximum horizontal strain always appeared at the bottom center before the failure for the parallel loading case; while the maximum horizontal strain for the vertical loading moved upward from the bottom center to the top center. There was a clear dividing line between the minimum perpendicular strain and the maximum perpendicular strain of the samples under parallel loading; however, under vertical loading, the perpendicular strain declined from the bottom to the top along the crack path. The surrounding dense part of the sintered sample (a few hundred microns) was mainly composed of large and straight cracks between printing layers, whereas the interior contained numerous small winding cracks. The intense cracks inside the sample led to a low flexural property compared to other well-prepared zirconia samples, which the inadequate additive formulations would be the main reason for the generation of cracks. A better understanding of the additive formulation (particularly the dispersant) and the debinding-sintering process are necessary for future improvement.

User Experience and Sustainability of 3D Printing in Dentistry

BACKGROUND

3D printing is a rapidly developing technology in the healthcare industry and in dentistry. Its application clearly shows that this area of digital dentistry has potential for everyday usage across all fields, including prosthodontics, orthodontics, maxillofacial surgery, and oral implantology. However, despite gaining ground, there is a lack of information about how specialists (dentists and dental technicians) use additive technology. Our research group aimed to investigate the impact of social media on additive manufacturing technology among dental specialists and their everyday usage of 3D printing.

METHODS

This paper investigated specialists' everyday usage of 3D printers via an online survey (Google Forms). The survey questions aimed to discover the number of 3D printers used, the accessibility of the devices, the annual cost, and the design programs. Since specialists tend to build online communities on social media, we circulated our study questionnaire using our profiles on LinkedIn, Facebook, and Instagram platforms during our research.

RESULTS

A total of 120 responses were received from 20 countries, with the most significant numbers being from Hungary 23.7% (n = 27), the United States 18.4% (n = 21), and the United Kingdom 7.9% (n = 9). Most of the participants were dentists (n = 68) or dental technicians (n = 29), but some CAD/CAM specialists (n = 23) also completed our survey. The participants had an average of 3.8 years (±0.7) of experience in the 3D printing field, and owned a total of 405 printing devices (3.6 on average/person).

CONCLUSIONS

The impact of social media on this research field is growing increasingly. Hence, we support specialists in joining virtual communities on professional platforms. This article intended to provide a practical overview, feedback, and direction for dentists interested in 3D printing technology. From our survey, we can conclude that additive technology is broadening dental applications and the services that we can provide for our patients.

Engineered implantable vaccine platform for continuous antigen-specific immunomodulation

Cancer vaccines harness the host immune system to generate antigen-specific antitumor immunity for long-term tumor elimination with durable immunomodulation. Commonly investigated strategies reintroduce ex vivo autologous dendritic cells (DCs) but have limited clinical adoption due to difficulty in manufacturing, delivery and low clinical efficacy. To combat this, we designed the "NanoLymph", an implantable subcutaneous device for antigen-specific antitumor immunomodulation. The NanoLymph consists of a dual-reservoir platform for sustained release of immune stimulants via a nanoporous membrane and hydrogel-encapsulated antigens for local immune cell recruitment and activation, respectively. Here, we present the development and characterization of the NanoLymph as well as efficacy validation for immunomodulation in an immunocompetent murine model. Specifically, we established the NanoLymph biocompatibility and mechanical stability. Further, we demonstrated minimally invasive transcutaneous refilling of the drug reservoir in vivo for prolonging drug release duration. Importantly, our study demonstrated that local elution of two drugs (GMCSF and Resiquimod) generates an immune stimulatory microenvironment capable of local DC recruitment and activation and generation of antigen-specific T lymphocytes within 14 days. In summary, the NanoLymph approach can achieve in situ immunomodulation, presenting a viable strategy for therapeutic cancer vaccines.

Biochemical Interaction between Materials Used for Interim Prosthetic Restorations and Saliva

The purpose of this study was to analyze the oxidative stress level and inflammatory status of saliva in the presence of certain materials used for obtaining interim prosthetic restorations. Four types of interim resin materials were investigated: a pressure/heat-cured acrylic resin (Superpont C+B, SpofaDental a.s Czech Republic, /KaVo Kerr Group), a milled resin (Telio CAD polymethyl methacrylate, Ivoclar Vivadent AG, Liechtenstein), a 3D printed resin (NextDent C&B MFH, NextDent by 3D Systems, the Netherlands), and a pressure/heat-cured micro-filled indirect composite resin (SR Chromasit, Ivoclar Vivadent AG, Liechtenstein). The disk-shaped resin samples (30 mm diameter, 2 mm high) were obtained in line with the producers' recommendations. The resulting resin specimens were incubated with saliva samples collected from twenty healthy volunteers. In order to analyze the antioxidant activity of the tested materials, certain salivary parameters were evaluated before and after incubation: uric acid, gamma glutamyl transferase (GGT), oxidative stress responsive kinase-1 (OXSR-1), and total antioxidant capacity (TAC); the salivary levels of tumor necrosis factor (TNFα) and interleukin-6 (IL-6) (inflammatory markers) were measured as well. The obtained results are overall favorable, showing that the tested materials did not cause significant changes in the salivary oxidative stress level and did not influence the inflammatory salivary status.

Strategies toward development of antimicrobial biomaterials for dental healthcare applications

Several approaches for elimination of oral pathogens are being explored at the present time since oral diseases remain prevalent affecting approximately 3.5 billion people worldwide. Need for antimicrobial biomaterials in dental healthcare include but is not restricted to designing resin composites and adhesives for prevention of dental caries. Constant efforts are also being made to develop antimicrobial strategies for clearance of endodontic space prior root canal treatment and for treatment of periimplantitis and periodontitis. This article discusses various conventional and nanotechnology-based strategies to achieve antimicrobial efficacy in dental biomaterials. Recent developments in the design and synthesis of antimicrobial peptides and antifouling zwitterionic polymers to effectively lessen the risks of antimicrobial drug resistance are also outlined in this review. Further, the role of contemporary strategies such as use of smart biomaterials, ionic solvent-based biomaterials and quorum quenchers incorporated biomaterials in the elimination of dental pathogens are described in detail. Lastly, we mentioned the approach of using polymers to print custom-made three-dimensional antibacterial dental products via additive manufacturing technologies. This review provides a critical perspective on the chemical, biomimetic, and engineering strategies intended for developing antimicrobial biomaterials that have the potential to substantially improve the dental health.

Elements of 3D Bioprinting in Periodontal Regeneration: Frontiers and Prospects

Periodontitis is a chronic infectious disease worldwide, caused by the accumulation of bacterial plaque, which can lead to the destruction of periodontal supporting tissue and eventually tooth loss. The goal of periodontal treatment is to remove pathogenic factors and control the periodontal inflammation. However, the complete regeneration of periodontal supporting tissue is still a major challenge according to current technology. Tissue engineering recovers the injured tissue through seed cells, bio-capable scaffold and bioactive factors. Three-D-bioprinting is an emerging technology in regeneration medicine/tissue engineering, because of its high accuracy and high efficiency, providing a new strategy for periodontal regeneration. This article represents the materials of 3D bioprinting in periodontal regeneration from three aspects: oral seed cell, bio-scaffold and bio-active factors.

Additive Manufacturing of Zirconia Ceramic and Its Application in Clinical Dentistry: A Review

Additive manufacturing (AM) has many advantages and became a valid manufacturing technique for polymers and metals in dentistry. However, its application for dental ceramics is still in process. Among dental ceramics, zirconia is becoming popular and widely used in dentistry mainly due to its outstanding properties. Although subtractive technology or milling is the state of art for manufacturing zirconia restorations but still has shortcomings. Utilizing AM in fabricating ceramics restorations is a new topic for many researchers and companies across the globe and a good understanding of AM of zirconia is essential for dental professional. Therefore, the aim of this narrative review is to illustrate different AM technologies available for processing zirconia and discus their advantages and future potential. A comprehensive literature review was completed to summarize different AM technologies that are available to fabricate zirconia and their clinical application is reported. The results show a promising outcome for utilizing AM of zirconia in restorative, implant and regenerative dentistry. However further improvements and validation is necessary to approve its clinical application.

Influence of the Printing Angle and Load Direction on Flexure Strength in 3D Printed Materials for Provisional Dental Restorations

The CAD/CAM techniques, especially additive manufacturing such as 3D printing, constitute an ever-growing part of obtaining different dental appliances and restorations. Of these, provisional restorations are of frequent use in daily dental practice and are the object of this study. Masticatory and parafunctional forces determine flexure on these prostheses. This study investigates the influence of the printing angle and loading direction of the applied force on the flexure strength of two commercially available printable resins—Detax Freeprint Temp and Nextdent MFH Vertex dental. Ten rectangular beam specimens printed at the angle of 0, 45 and 90 degrees were fabricated of each of these materials, with an addition of 10 at 0 degrees for the investigation of the load direction. Three-point bending tests were performed in a universal testing machine. Flexure strength, strain at break and Young’s modulus were determined and a statistical analysis was performed on the obtained data. According to the statistical analysis, the flexural strength has a significance dependence with respect to degrees of orientation, for both investigated materials.

Scientometric Analysis and Systematic Review of Multi-Material Additive Manufacturing of Polymers

Multi-material additive manufacturing of polymers has experienced a remarkable increase in interest over the last 20 years. This technology can rapidly design and directly fabricate three-dimensional (3D) parts with multiple materials without complicating manufacturing processes. This research aims to obtain a comprehensive and in-depth understanding of the current state of research and reveal challenges and opportunities for future research in the area. To achieve the goal, this study conducts a scientometric analysis and a systematic review of the global research published from 2000 to 2021 on multi-material additive manufacturing of polymers. In the scientometric analysis, a total of 2512 journal papers from the Scopus database were analyzed by evaluating the number of publications, literature coupling, keyword co-occurrence, authorship, and countries/regions activities. By doing so, the main research frame, articles, and topics of this research field were quantitatively determined. Subsequently, an in-depth systematic review is proposed to provide insight into recent advances in multi-material additive manufacturing of polymers in the aspect of technologies and applications, respectively. From the scientometric analysis, a heavy bias was found towards studying materials in this field but also a lack of focus on developing technologies. The future trend is proposed by the systematic review and is discussed in the directions of interfacial bonding strength, printing efficiency, and microscale/nanoscale multi-material 3D printing. This study contributes by providing knowledge for practitioners and researchers to understand the state of the art of multi-material additive manufacturing of polymers and expose its research needs, which can serve both academia and industry.

3D Modeling of Epithelial Tumors-The Synergy between Materials Engineering, 3D Bioprinting, High-Content Imaging, and Nanotechnology

The current statistics on cancer show that 90% of all human cancers originate from epithelial cells. Breast and prostate cancer are examples of common tumors of epithelial origin that would benefit from improved drug treatment strategies. About 90% of preclinically approved drugs fail in clinical trials, partially due to the use of too simplified in vitro models and a lack of mimicking the tumor microenvironment in drug efficacy testing. This review focuses on the origin and mechanism of epithelial cancers, followed by experimental models designed to recapitulate the epithelial cancer structure and microenvironment, such as 2D and 3D cell culture models and animal models. A specific focus is put on novel technologies for cell culture of spheroids, organoids, and 3D-printed tissue-like models utilizing biomaterials of natural or synthetic origins. Further emphasis is laid on high-content imaging technologies that are used in the field to visualize in vitro models and their morphology. The associated technological advancements and challenges are also discussed. Finally, the review gives an insight into the potential of exploiting nanotechnological approaches in epithelial cancer research both as tools in tumor modeling and how they can be utilized for the development of nanotherapeutics.

Selected Spectroscopic Techniques for Surface Analysis of Dental Materials: A Narrative Review

The presented work focuses on the application of spectroscopic methods, such as Infrared Spectroscopy (IR), Fourier Transform Infrared Spectroscopy (FT-IR), Raman spectroscopy, Ultraviolet and Visible Spectroscopy (UV-Vis), X-ray spectroscopy, and Mass Spectrometry (MS), which are widely employed in the investigation of the surface properties of dental materials. Examples of the research of materials used as tooth fillings, surface preparation in dental prosthetics, cavity preparation methods and fractographic studies of dental implants are also presented. The cited studies show that the above techniques can be valuable tools as they are expanding the research capabilities of materials used in dentistry.