Current and Emerging Applications of 3D Printing in Restorative Dentistry

The influence of filler load in 3D printing resin-based composites

OBJECTIVE

To evaluate the influence of the barium glass (BG) filler in 3D printing resin-based composites for restorative structures.

METHODS

Experimental 3D printing resin-based composites were formulated with UDMA 70%wt, Bis-EMA 20%wt, and TEGDMA 10%wt. Photoinitiators TPO and DFI (2%wt) were used. BG was incorporated at 40%wt and 50%wt. 0%wt BG was used as negative control and the VarseoSmile Crownplus (Bego) was used as a commercial control. Specimens were printed using a 3D printer. Subsequently, specimens were washed and submitted to post-curing with 405 nm at 60ºC for 2 × 20 min at FormCure (FormLabs). 3D printing resin-based composites were evaluated by flexural strength, degree of conversion, softening in solvent, radiopacity, and cytotoxicity against gingival fibroblasts. Data were statistically analyzed using one-way ANOVA (α = 0.05).

RESULTS

No significant differences in flexural strength were showed between BG40% (90.5 ± 5,4 MPa), BG50% (102.0 ± 11.7 MPa) and VA (105.2 ± 11.7 MPa). Addition of 40% and 50% of BG showed no influence in the degree of conversion compared to VA (p > 0.05). All groups showed softening in solvent after immersion in ethanol (p < 0.05). All groups showed more than 1mmAl of radiopacity. BG50% showed significantly higher radiopacity (2.8 ± 0.3 mmAl) than other groups (p < 0,05). Cytotoxicity evaluation showed gingival cell viability higher than 80% for all groups.

SIGNIFICANCE

Addition of up to 50%wt of barium glass in experimental 3D printing resin-based composites showed promising results for long-term restorative structures.

Evaluation of masticatory performance and patient satisfaction for conventional and 3D-printed implant overdentures: a randomized crossover study

BACKGROUND

This crossover clinical study aimed to evaluate and compare masticatory performance and patient satisfaction for patients rehabilitated with conventional heat-cured acrylic resin and 3D-printed mandibular implant overdentures retained with bar attachment.

MATERIALS AND METHODS

Sixteen completely edentulous healthy participants received new conventional dentures. In the mandible, four interforaminal implants were inserted. Following the stage of osseointegration, the bar was constructed in a trapezoidal configuration. Each patient randomly received the following overdentures using a crossover design: (1) conventional heat-cured acrylic resin overdenture and (2) 3D-printed overdenture (developed by scanning of mandibular conventional overdenture). The masticatory performance was assessed by conducting a two-colour mixing ability test at 5, 10, 20, 30, and 50 masticatory cycles. Moreover, the McGill Denture Satisfaction Questionnaire (MDSQ) was employed to assess patient satisfaction. Evaluation was performed after 3 months of using each overdenture. Paired sample t tests were used to compare the masticatory performance and MDSQ scores of patients for both prostheses.

RESULTS

No significant difference in masticatory performance was reported between the two types of overdentures. Regarding patient satisfaction, only the esthetic aspect was significantly better for conventionally processed overdentures than for printed overdentures. Insignificant differences were observed regarding other MDSQ items between the two overdentures.

CONCLUSION

Within this clinical study, 3D-printed implant overdentures showed promising results in terms of chewing efficiency and patient satisfaction compared to conventionally fabricated implant overdentures.

TRIAL REGISTRATION

Retrospectively registered at www.

CLINICALTRIALS

gov : NCT06148727.(28/11/2023).

Antimicrobial activity of cleanser tablets against S. mutans and C. Albicans on different denture base materials

BACKGROUND

In this study, the antimicrobial activity of three different cleanser tablets on S. mutans and C. albicans adhesion to PMMA, polyamide and 3D printed resin was investigated.

METHODS

40 samples were prepared for PMMA (SR Triplex Hot), polyamide (Deflex) and 3D printed resin (PowerResins Denture) materials and divided into four subgroups for cleansers (Aktident™, Protefix™, Corega™ tablets and distilled water) (n = 5). After the surface preparations were completed, the samples were immersed separately in tubes containing the prepared microorganism suspension and incubated at 37˚C for 24 h. After the incubation, the samples were kept in the cleanser solutions. The samples were then transferred to sterile saline tubes. All the tubes were vortexed and 10 µl was taken from each of them. Sheep blood agar was inoculated for colony counting. The inoculated plates were incubated for 48 h for S. mutans and 24 h for C. albicans. After incubation, colonies observed on all plates were counted. Statistical analyses were done with three-way ANOVA and Tukey's multiple comparison test.

RESULTS

Polyamide material registered the highest colony count of S. mutans, whereas PMMA registered the lowest. Significant differences in S. mutans adherence (p = 0.002) were found between the three denture base materials, but no such difference in C. albicans adherence (p = 0.221) was identified between the specimens. All three cleanser tablets eliminated 98% of S. mutans from all the material groups. In all these groups, as well, the antifungal effect of Corega™ on C. albicans was significantly higher than those of the other two cleanser tablets.

CONCLUSIONS

According to the study's results, it may be better to pay attention to surface smoothness when using polyamide material to prevent microorganism retention. Cleanser tablets are clinically recommended to help maintain hygiene in removable denture users, especially Corega tablets that are more effective on C. albicans.

Three-dimensional printing of the human lung pleural cavity model for PDT malignant mesothelioma

OBJECTIVE

The primary aim was to investigate emerging 3D printing and optical acquisition technologies to refine and enhance photodynamic therapy (PDT) dosimetry in the management of malignant pleural mesothelioma (MPM).

MATERIALS AND METHODS

A rigorous digital reconstruction of the pleural lung cavity was conducted utilizing 3D printing and optical scanning methodologies. These reconstructions were systematically assessed against CT-derived data to ascertain their accuracy in representing critical anatomic features and post-resection topographical variations.

RESULTS

The resulting reconstructions excelled in their anatomical precision, proving instrumental translation for precise dosimetry calculations for PDT. Validation against CT data confirmed the utility of these models not only for enhancing therapeutic planning but also as critical tools for educational and calibration purposes.

CONCLUSION

The research outlined a successful protocol for the precise calculation of light distribution within the complex environment of the pleural cavity, marking a substantive advance in the application of PDT for MPM. This work holds significant promise for individualizing patient care, minimizing collateral radiation exposure, and improving the overall efficiency of MPM treatments.

Evaluation of photopolymer resins for dental prosthetics fabricated via the stereolithography process at different polymerization temperatures-Part I: Conversion rate and mechanical properties

STATEMENT OF PROBLEM

Improvement in the mechanical properties of 3-dimensional (3D) printed dental prostheses is necessary to prevent wear caused by an antagonist or fracture. However, how different printing temperatures affect their mechanical properties is unclear.

PURPOSE

The purpose of this in vitro study was to evaluate the mechanical properties of 3D printed parts fabricated at different printing temperatures.

MATERIAL AND METHODS

Photopolymer specimens were fabricated at 3 different temperatures (room temperature, 50 °C, and 70 °C) using a stereolithography 3D printer. After rinsing to remove the residual monomer, the specimens were divided into 2 groups: with or without postprocessing. The viscosity of the photopolymerization resin was measured while the temperature was increased. Furthermore, the double-bond conversion (DBC) of the printed part was evaluated (n=3). Mechanical properties were investigated via dynamic mechanical analysis (n=1) and tensile testing (n=5). Statistical comparisons were performed via 1-way analysis of variance, followed by the Tukey honestly significant difference test (α=.05).

RESULTS

The DBC rates of the green condition group increased from 66.67% to 86.33% with increasing temperature. In addition, these specimens exhibited improved mechanical properties and reduced residual monomer levels.

CONCLUSIONS

Specimens fabricated at a temperature of 70 °C exhibited mechanical properties suitable for clinical application.

Fabrication of facially guided CAD-CAM complete dentures: A dental technique

An alternative protocol is presented to design computer-aided design and computer-aided manufacturing (CAD-CAM) complete dentures and overdentures using a facially guided digital design. The facially guided design protocol with CAD-CAM facilitated communication between the clinician and dental laboratory technician. A monolithic denture and overdenture were fabricated guided by preliminary dentures with 3-dimensionally (3D) printed denture bases and milled wax teeth.

Anti-adhesive activity of some secondary metabolites against Staphylococcus aureus on 3D printing medical materials

Recent improvements in 3D printing technology have increased the usage of 3D printed materials in several areas. An exciting and emerging area of applying these next-generation manufacturing strategies is the development of devices for biomedical applications. The main aim of this work was to investigate the effect of tannic acid, gallic acid, and epicatechin gallate on the physicochemical characteristics of acrylonitrile butadiene-styrene (ABS) and Nylon 3D printing materials using the contact angle method. The adhesion of Staphylococcus aureus on untreated and treated materials was evaluated by scanning electron microscopy (SEM) analysis and the images were treated by MATLAB software. The results of the contact angle measurements showed a significant change in the physicochemical properties of both surfaces, indicated an increase in the electron donor character of 3D printing materials following treatment. Thus, the ABS surfaces treated with tannic acid, gallic acid, and epicatechin gallate have become more electron donating. Furthermore, our results proved the ability of S. aureus to adhere on all materials with a percentage of 77.86% for ABS and 91.62% for nylon. The SEM has shown that all actives molecules were sufficient to obtain better inhibition of bacterial adhesion, which tannic acid has shown a total inhibition of S. aureus on ABS. From these results, our treatment presents a high potential for utilization as an active coating to prevent bacterial attachment and the eventual biofilm development in medical field.

Degree of conversion and residual monomer elution of 3D-printed, milled and self-cured resin-based composite materials for temporary dental crowns and bridges

The aim of this work was to investigate the elution of residual monomers as a function of the manufacturing process, which are CAD/CAM manufacturing, self-curing and 3D printing. The experimental materials used consisted of the base monomers TEGDMA, Bis-GMA and Bis-EMA and 50 wt.% fillers. Additionally, a 3D printing resin without fillers was tested. The elution of the base monomers into the different media (water, ethanol and ethanol/water (75/25 vol. %)) at 37 °C over a period of up to 120 d as well as the degree of conversion (DC) by FTIR were investigated. No monomer elution could be detected in water. Most residual monomers in both other media were released from the self-curing material whereas the 3D printing composite released relatively little. The CAD/CAM blanks released hardly any quantitatively detectable amounts of monomers. Relative to the base composition, TEGDMA eluted less than Bis-GMA and Bis-EMA. DC did not correlate with residual monomer release; thus, leaching was determined not only by the amount of residual monomers present but by further factors as possibly network density and structure. The CAD/CAM blanks and the 3D printing composite showed similar high DC but lower residual monomer release from the CAD/CAM blank, likewise the self-curing composite and the 3D printing resin exhibited similar DC but different monomer elution. In terms of residual monomer elution and DC, the 3D printing composite seems promising as a new material class for the use as temporary dental crowns and bridges.

The Clinical Potential of 3D-Printed Crowns Reinforced with Zirconia and Glass Silica Microfillers

The development of 3D-printed crown resin materials with improved mechanical and physical properties is an area of growing interest in dentistry. This study aimed to develop a 3D-printed crown resin material modified with zirconia glass (ZG) and glass silica (GS) microfillers to enhance overall mechanical and physical properties. A total of 125 specimens were created and divided into five groups: control unmodified resin, 5% either ZG or GS reinforced 3D-printed resin, and 10% either ZG or GS reinforced 3D-printed resin. The fracture resistance, surface roughness, and translucency parameter were measured, and fractured crowns were studied under a scanning electron microscope. The results showed that 3D-printed parts that were strengthened with ZG and GS microfillers demonstrated comparable mechanical performance to unmodified crown resin but resulted in greater surface roughness, and only the group that contained 5% ZG showed an increase in translucency. However, it should be noted that increased surface roughness may impact the aesthetics of the crowns, and further optimisation of microfillers concentrations may be necessary. These findings suggest that the newly developed dental-based resins that incorporate microfillers could be suitable for clinical applications, but further studies are necessary to optimise the nanoparticle concentrations and investigate their long-term clinical outcomes.

The theoretical adhesion of Staphylococcus aureus and Pseudomonas aeruginosa as nosocomial pathogens on 3D printing filament materials

Microbial infections and nosocomial diseases associated with biomaterial have become a major problem of public health and largely lead to revision surgery, which is painful and quite expensive for patients. These infections are caused by formation of biofilm, which present a difficulty of treatment with conventional antibiotics. The aim of our study is to investigate the theoretical adhesion of Staphylococcus aureus and Pseudomonas aeruginosa on four 3-dimensional printing filament materials used in the manufacture of medical equipment. Thus, the physicochemical properties of these microorganisms and all filament materials were determined using the contact angle measurements. Our results indicated that bacterial surfaces were hydrophilic, strongly electron donating and weakly electron accepting. In contrast, nylon, acrylonitrile butadiene-styrene, polyethylene terephthalate, and polylactic acid surfaces were hydrophobic and more electron-donor than electron-acceptor. In addition, according to the values of total free interaction energy ΔG^Total, Staphylococcus aureus was found unable to adhere to the filament materials except polyethylene terephthalate surface. However, Pseudomonas aeruginosa showed adhesion capacity only for acrylonitrile butadiene-styrene and polyethylene terephthalate surfaces. These findings imply that the usage of these 3D printed materials in the medical area necessitates more research into enhancing their resistance to bacterial adherence.

Recent Advances in the Applications of Additive Manufacturing (3D Printing) in Drug Delivery: A Comprehensive Review

There has been a tremendous increase in the investigations of three-dimensional (3D) printing for biomedical and pharmaceutical applications, and drug delivery in particular, ever since the US FDA approved the first 3D printed medicine, SPRITAM® (levetiracetam) in 2015. Three-dimensional printing, also known as additive manufacturing, involves various manufacturing techniques like fused-deposition modeling, 3D inkjet, stereolithography, direct powder extrusion, and selective laser sintering, among other 3D printing techniques, which are based on the digitally controlled layer-by-layer deposition of materials to form various geometries of printlets. In contrast to conventional manufacturing methods, 3D printing technologies provide the unique and important opportunity for the fabrication of personalized dosage forms, which is an important aspect in addressing diverse patient medical needs. There is however the need to speed up the use of 3D printing in the biopharmaceutical industry and clinical settings, and this can be made possible through the integration of modern technologies like artificial intelligence, machine learning, and Internet of Things, into additive manufacturing. This will lead to less human involvement and expertise, independent, streamlined, and intelligent production of personalized medicines. Four-dimensional (4D) printing is another important additive manufacturing technique similar to 3D printing, but adds a 4th dimension defined as time, to the printing. This paper aims to give a detailed review of the applications and principles of operation of various 3D printing technologies in drug delivery, and the materials used in 3D printing, and highlight the challenges and opportunities of additive manufacturing, while introducing the concept of 4D printing and its pharmaceutical applications.

Antibiofilm Activity of 3D-Printed Nanocomposite Resin: Impact of ZrO2 Nanoparticles

Poly(methyl methacrylate) (PMMA) is a commonly used material, as it is biocompatible and relatively cheap. However, its mechanical properties and weak antibiofilm activity are major concerns. With the development of new technology, 3D-printed resins are emerging as replacements for PMMA. Few studies have investigated the antibiofilm activity of 3D-printed resins. Therefore, this study aimed to investigate the antibiofilm activity and surface roughness of a 3D-printed denture base resin modified with different concentrations of zirconium dioxide nanoparticles (ZrO₂ NPs). A total of 60 resin disc specimens (15 × 2 mm) were fabricated and divided into six groups (n = 10). The groups comprised a heat-polymerized resin (PMMA) group, an unmodified 3D-printed resin (NextDent) group, and four 3D-printed resin groups that were modified with ZrO₂ NPs at various concentrations (0.5 wt%, 1 wt%, 3 wt%, and 5 wt%). All specimens were polished using a conventional method and then placed in a thermocycler machine for 5000 cycles. Surface roughness (Ra, µm) was measured using a non-contact profilometer. The adhesion of Candida albicans (C. albicans) was measured using a fungal adhesion assay that consisted of a colony forming unit assay and a cell proliferation assay. The data were analyzed using Shapiro-Wilk and Kruskal-Wallis tests. A Mann-Whitney U test was used for pairwise comparison, and p-values of less than 0.05 were considered statistically significant. The lowest Ra value (0.88 ± 0.087 µm) was recorded for the PMMA group. In comparison to the PMMA group, the 3% ZrO₂ NPs 3D-printed group showed a significant increase in Ra (p < 0.025). For the 3D-printed resins, significant differences were found between the groups with 0% vs. 3% ZrO₂ NPs and 3% vs. 5% ZrO₂ NPs (p < 0.025). The highest Ra value (0.96 ± 0.06 µm) was recorded for the 3% ZrO₂ NPs group, and the lowest Ra values (0.91 ± 0.03 µm) were recorded for the 0.5% and 5% ZrO₂ NPs groups. In terms of antifungal activity, the cell proliferation assay showed a significant decrease in the C. albicans count for the 0.5% ZrO₂ NPs group when compared with PMMA and all other groups of 3D-printed resins. The group with the lowest concentration of ZrO₂ NPs (0.5%) showed the lowest level of C. albicans adhesion of all the tested groups and showed the lowest Candida count (0.29 ± 0.03). The addition of ZrO₂ NPs in low concentrations did not affect the surface roughness of the 3D-printed resins. These 3D-printed resins with low concentrations of nanocomposites could be used as possible materials for the prevention and treatment of denture stomatitis, due to their antibiofilm activities.

Additive manufacturing technologies in the oral implant clinic: A review of current applications and progress

Additive manufacturing (AM) technologies can enable the direct fabrication of customized physical objects with complex shapes, based on computer-aided design models. This technology is changing the digital manufacturing industry and has become a subject of considerable interest in digital implant dentistry. Personalized dentistry implant treatments for individual patients can be achieved through Additive manufacturing. Herein, we review the applications of Additive manufacturing technologies in oral implantology, including implant surgery, and implant and restoration products, such as surgical guides for implantation, custom titanium meshes for bone augmentation, personalized or non-personalized dental implants, custom trays, implant casts, and implant-support frameworks, among others. In addition, this review also focuses on Additive manufacturing technologies commonly used in oral implantology. Stereolithography, digital light processing, and fused deposition modeling are often used to construct surgical guides and implant casts, whereas direct metal laser sintering, selective laser melting, and electron beam melting can be applied to fabricate dental implants, personalized titanium meshes, and denture frameworks. Moreover, it is sometimes required to combine Additive manufacturing technology with milling and other cutting and finishing techniques to ensure that the product is suitable for its final application.

Novel 3D Printed Resin Crowns for Primary Molars: In Vitro Study of Fracture Resistance, Biaxial Flexural Strength, and Dynamic Mechanical Analysis

This study evaluated the fracture resistance, biaxial flexural strength (BFS), and dynamic mechanical analysis (DMA) of three-dimensional (3D) printing resins for the esthetic restoration of primary molars. Two 3D printing resins, Graphy (GP) and NextDent (NXT), and a prefabricated zirconia crown, NuSmile (NS), were tested. GP and NXT samples were 3D printed using the workflow recommended by each manufacturer. Data were collected and statistically analyzed. As a result of the fracture resistance test of 0.7-mm-thick 3D printed resin crowns with a thickness similar to that of the NS crown, there was no statistically significant difference among GP (1491.6 ± 394.6 N), NXT (1634.4 ± 289.3 N), and NS (1622.8 ± 323.9 N). The BFS of GP was higher for all thicknesses than that of NXT. Both resins showed high survival probabilities (more than 90%) when subjected to 50 and 150 MPa. Through DMA, the glass transition temperatures of GP and NXT were above 120 °C and the rheological behavior of GP and NXT according to temperature and frequency were analyzed. In conclusion, GP and NXT showed optimum strength to withstand bite forces in children, and 3D printed resin crowns could be an acceptable option for fixed prostheses of primary teeth.

In Vitro Analysis of Shear Stress: CAD Milled vs Printed Denture Base Resins with Bonded Denture Tooth

PURPOSE

As the fabrication of computer-aided design (CAD) milled and 3D printed denture base resins with bonded denture teeth increase in popularity, there is a need for research comparing the shear bond stress of milled and printed denture base resins with bonded denture teeth to that of a conventional heat processed denture base.

MATERIALS AND METHODS

Denture base resin specimens (n = 9) were fabricated according to manufacturers' instructions using a novel test design. Two milled (Ivobase CAD PMMA, Ivoclar Vivadent and Polident PMMA, Polident Dental) and two 3D printed (Denture Base LP Resin, Formlabs and Lucitone Digital Print, Dentsply Sirona) materials were used. Conventional heat processed polymethylmethacrylate was used as the control (Lucitone 199, Dentsply Sirona). Denture teeth (VITA Vitapan XL T44, #8, VITA Zahnfabrik) were bonded to their respective bases using denture tooth bonding agent (Ivobase CAD bonding system, Ivoclar). Specimens were aged in water for 600 hours at 37°C and loaded until failure in a Universal testing machine. Shear bond stress was calculated. All specimens were evaluated for mode of failure and select specimens under scanning electron microscope and vertical scanning interferometry. Data were analyzed with one-way ANOVA followed by Tukey test (IBM SPSS) and fracture analysis performed.

RESULTS

Shear stress was highest for the heat processed control (mean = 180 N ±26.76) and Polident test groups (mean = 180 N ± 34.90). Milled specimens were not significantly different from the control (p = 0.076 for IvoBase CAD and 1.00 for Polident), while the printed groups were significantly different from the control (p = 0.012 for Formlabs Denture Base Resin and p = 0.00 for Carbon Lucitone Digital Print). Milled denture base resins performed similarly to heat processed denture base resin and better than 3D printed denture bases.

CONCLUSION

For complete denture wearers, all resin materials used in this study may be clinically acceptable, as the sheer stress for all groups was higher than the reported maximum biting force of complete denture patients. However, for implant retained prostheses, the incorporation of additional retentive features should be considered when bonding denture teeth to printed bases. More research is needed to evaluate methods to increase the bond strength of denture teeth to printed denture base resins.

The Effect of Two Different Light-Curing Units and Curing Times on Bulk-Fill Restorative Materials

This study aimed to evaluate the effect of two different light-curing units and curing times on the surface microhardness (SMH), compressive strength (CS), and volumetric shrinkage (VS) of four restorative materials (FiltekTM Z250, FiltekTM Bulk Fill Posterior, Beautifil® Bulk Restorative, ACTIVATM BioACTIVE). For all tests, each material was divided into two groups depending on the curing unit (Woodpecker LED-E and CarboLED), and each curing unit group was further divided into two subgroups according to curing time (10 s and 20 s). SMH was evaluated using a Vickers hardness tester, CS was tested using a universal testing machine, and VS was measured using video imaging. In all the restorative materials cured with Woodpecker LED-E, the 20 s subgroup demonstrated significantly higher SMH values than the 10 s subgroup. In both light-curing time subgroups, the CarboLED group showed significantly higher CS values than the Woodpecker LED-E group for all restorative materials except FiltekTM Bulk Fill Posterior cured for 20 s. ACTIVATM BioACTIVE showed significantly greater volumetric change than the other restorative materials. A higher curing light intensity and longer curing time had a positive effect on the SMH and CS of the restorative materials tested in this study. On the other hand, curing unit and time did not show a significant effect on the VS values of restorative materials.

3D Printing and Virtual Surgical Planning in Oral and Maxillofacial Surgery

Compared to traditional manufacturing methods, additive manufacturing and 3D printing stand out in their ability to rapidly fabricate complex structures and precise geometries. The growing need for products with different designs, purposes and materials led to the development of 3D printing, serving as a driving force for the 4th industrial revolution and digitization of manufacturing. 3D printing has had a global impact on healthcare, with patient-customized implants now replacing generic implantable medical devices. This revolution has had a particularly significant impact on oral and maxillofacial surgery, where surgeons rely on precision medicine in everyday practice. Trauma, orthognathic surgery and total joint replacement therapy represent several examples of treatments improved by 3D technologies. The widespread and rapid implementation of 3D technologies in clinical settings has led to the development of point-of-care treatment facilities with in-house infrastructure, enabling surgical teams to participate in the 3D design and manufacturing of devices. 3D technologies have had a tremendous impact on clinical outcomes and on the way clinicians approach treatment planning. The current review offers our perspective on the implementation of 3D-based technologies in the field of oral and maxillofacial surgery, while indicating major clinical applications. Moreover, the current report outlines the 3D printing point-of-care concept in the field of oral and maxillofacial surgery.

Accuracy of Dental and Industrial 3D Printers

PURPOSE

This in vitro study evaluated the dimensional accuracy of three 3D printers and one milling machine with their respective polymeric materials using a simplified geometrical model.

MATERIALS AND METHODS

A simplified computer-aided design (CAD) model was created. The test samples were fabricated with three 3D printers: a dental desktop stereolithography (SLA) printer, an industrial SLA printer, and an industrial fused deposition modeling (FDM) printer, as well as a 5-axis milling machine. One polymer material was used per industrial printer and milling machine while two materials were used with the dental printer for a total of five study groups. Test specimens were then digitized using a laboratory scanner. The virtual outer caliper method was used to measure the linear dimensions of the digitized 3D printed and milled specimens in x-, y-, and z-axes, and compare them to the known values of the CAD model. Data were analyzed with Kruskal-Wallis one-way ANOVA on Ranks followed by the Tukey's test.

RESULTS

Milled specimens were not significantly different from the CAD model in any dimension (p > 0.05). All 3D printed specimens were significantly different from the CAD model in all dimensions (p = 0.01), except the dental SLA 3D printer with one of the polymers tested (Bis-GMA) which was not significantly different in two (x and z) dimensions (p = 0.4 and p = 0.12).

CONCLUSIONS

The milling technology tested provided greater dimensional accuracy than the selected 3D printing. Printer, printing technology, and material selection affected the accuracy of the printed model.

Surface Properties of Polymer Resins Fabricated with Subtractive and Additive Manufacturing Techniques

This study aimed to compare the surface roughness, hardness, and flexure strength of interim indirect resin restorations fabricated with CAD-CAM (CC), 3D printing (3D), and conventional techniques (CV). Twenty disk (3 mm × Ø10 mm) and ten bar specimens (25 × 2 × 2 mm) were fabricated for the CC, 3D, and CV groups, to be used for surface roughness, micro-hardness, and flexural strength testing using standardized protocol. Three indentations for Vickers micro-hardness (VHN) were performed on each disk and an average was identified for each specimen. Surface micro-roughness (Ra) was calculated in micrometers (μm) using a 3D optical non-contact surface microscope. A three-point bending test with a universal testing machine was utilized for assessing flexural strength. The load was applied at a crosshead speed of 3 mm/min over a distance of 25 mm until fracture. Means and standard deviations were compared using ANOVA and post hoc Tukey-Kramer tests, and a p-value of ≤0.05 was considered statistically significant. Ra was significantly different among the study groups (p < 0.05). Surface roughness among the CC and CV groups was statistically comparable (p > 0.05). However, 3D showed significantly higher Ra compared to CC and CV samples (p < 0.05). Micro-hardness was significantly higher in 3D samples (p < 0.05) compared to CC and CV specimens. In addition, CC and CV showed comparable micro-hardness (p > 0.05). A significant difference in flexural strength was observed among the study groups (p < 0.05). CC and 3D showed comparable strength outcomes (p > 0.05), although CV specimens showed significantly lower (p < 0.05) strength compared to CC and 3D samples. The 3D-printed provisional restorative resins showed flexural strength and micro-hardness comparable to CAD-CAM fabricated specimens, and surface micro-roughness for printed specimens was considerably higher compared to CAD-CAM and conventional fabrication techniques.

3D and 4D printing in dentistry and maxillofacial surgery: Printing techniques, materials, and applications

3D and 4D printing are cutting-edge technologies for precise and expedited manufacturing of objects ranging from plastic to metal. Recent advances in 3D and 4D printing technologies in dentistry and maxillofacial surgery enable dentists to custom design and print surgical drill guides, temporary and permanent crowns and bridges, orthodontic appliances and orthotics, implants, mouthguards for drug delivery. In the present review, different 3D printing technologies available for use in dentistry are highlighted together with a critique on the materials available for printing. Recent reports of the application of these printed platformed are highlighted to enable readers appreciate the progress in 3D/4D printing in dentistry.

3D printed complete removable dental prostheses: a narrative review

Background

The purpose of this paper is to review the available literature on three-dimensionally printed complete dentures in terms of novel biomaterials, fabrication techniques and workflow, clinical performance and patient satisfaction.

Methods

The methodology included applying a search strategy, defining inclusion and exclusion criteria, selecting studies and forming tables to summarize the results. Searches of PubMed, Scopus, and Embase databases were performed independently by two reviewers to gather literature published between 2010 and 2020.

Results

A total of 126 titles were obtained from the electronic database, and the application of exclusion criteria resulted in the identification of 21 articles pertaining to printed technology for complete dentures. Current innovations and developments in digital dentistry have successfully led to the fabrication of removable dental prostheses using CAD/CAM technologies. Milled dentures have been studied more than 3D printed ones in the currently available literature. The limited number of clinical studies, mainly case reports, suggest current indications of 3D printing in denture fabrication process to be custom tray, record bases, trial, interim or immediate dentures but not definitive prostheses fabrication. Limitations include poor esthetics and retention, inability to balance occlusion and low printer resolution.

Conclusions

Initial studies on digital dentures have shown promising short-term clinical performance, positive patient-related results and reasonable cost-effectiveness. 3D printing has potential to modernize and streamline the denture fabrication techniques, materials and workflows. However, more research is required on the existing and developing materials and printers to allow for advancement and increase its application in removable prosthodontics.

Improving the Mechanical Strength of Dental Applications and Lattice Structures SLM Processed

To manufacture custom medical parts or scaffolds with reduced defects and high mechanical characteristics, new research on optimizing the selective laser melting (SLM) parameters are needed. In this work, a biocompatible powder, 316L stainless steel, is characterized to understand the particle size, distribution, shape and flowability. Examination revealed that the 316L particles are smooth, nearly spherical, their mean diameter is 39.09 μm and just 10% of them hold a diameter less than 21.18 μm. SLM parameters under consideration include laser power up to 200 W, 250-1500 mm/s scanning speed, 80 μm hatch spacing, 35 μm layer thickness and a preheated platform. The effect of these on processability is evaluated. More than 100 samples are SLM-manufactured with different process parameters. The tensile results show that is possible to raise the ultimate tensile strength up to 840 MPa, adapting the SLM parameters for a stable processability, avoiding the technological defects caused by residual stress. Correlating with other recent studies on SLM technology, the tensile strength is 20% improved. To validate the SLM parameters and conditions established, complex bioengineering applications such as dental bridges and macro-porous grafts are SLM-processed, demonstrating the potential to manufacture medical products with increased mechanical resistance made of 316L.

Current status and applications of additive manufacturing in dentistry: A literature-based review

Objective

To study the current status and applications of additive manufacturing (AM) in dentistry along with various technologies, benefits and future scope.

Methods

A significant number of relevant research papers on the additive manufacturing application in dentistry are identified through Scopus and studied using bibliometric analysis that shows an increasing trend of research in this field. This paper briefly describes various types of AM technologies with their accuracy, pros and cons along with different dental materials. Paper also discusses various benefits of AM in dentistry and steps used to create 3D printed dental model using this technology. Further, ten major AM applications in dentistry are identified along with primary references and objectives.

Results

Additive manufacturing is an innovative technique moving towards the customised production of dental implants and other dental tools using computer-aided design (CAD) data. This technology is used to manufacture elaborate dental crowns, bridges, orthodontic braces and can also various other models, devices and instruments with lesser time and cost. With the help of this disruptive innovation, dental implants are fabricated accurately as per patient data captured by the dental 3D scanner. The application of this technology is also being explored for the precise manufacturing of removal prosthetics, aligners, surgical templates for implants and produce models that for the planning of treatment and preoperative positioning of the jaws.