Optical behavior of 3D-printed dental restorative resins: Influence of thickness and printing angle

Trueness of multichromatic versus monochromatic veneers printed using tilted stereolithography technology at different build angles? An in vitro study

OBJECTIVES

To evaluate the influence of shade (monochromatic vs multichromatic) and build angle on the trueness of veneers printed using tilted stereolithography technology (TSLA).

METHODS

A maxillary central incisor typodont tooth model was prepared to receive a butt-joint full veneer with 0.3 mm labial and 2 mm incisal reduction. The preparation was digitized using laboratory scanner (T310; Medit) to design the veneer restoration. Sixty veneers were fabricated using Tilting Stereolithography (TSLA) 3D-printing technique (Dfab; DWS). Thirty veneers were printed in monochromatic shade (N = 30) (IrixMax monochromatic A2; DWS) and thirty veneers in multichromatic shade (N = 30) (A1-A3.5) using hybrid resin-ceramic material (IrixMax Photoshade A1-A3.5; DWS). In each group, three subgroups were defined based on the build angle (N = 10): 90°, 75° and 45° angles. Trueness was evaluated quantitatively and qualitatively using metrology software (Geomagic Control v2020; 3DSystems). Two-way Analysis of Variance (ANOVA) test with Tukey post hoc test for multiple comparisons were used to detect the differences in root mean square estimate (RMSE) between the test groups (α =0.05).

RESULTS

Two-way ANOVA revealed a statistically significant interaction between different build angles and material shade on RMSE in butt-joint veneer preparation design (P = .001). Multichromatic shade showed significantly higher RMSE values when printed at 45° (P=.010) compared to monochromatic one.

CONCLUSIONS

Build angle and material shade have an influence on the trueness of veneers printed using TSLA technique. 45° build angle with multichromatic shade material resulted in the highest RMSE deviation values. Therefore, clinicians should be cautious with the selected print angle when printing a multichromatic resin-based veneers.

STATEMENT OF CLINICAL RELEVANCE

Advances in material science and 3D-printers resulted in the introduction of a chairside TSLA 3D-printer that can be used for the fabrication of multichromatic, resin-based veneer restorations. Both build angle and material shade influence the dimensional accuracy of TSLA printed veneer restorations. To print highly accurate multichromatic restorations and increase the number of printed parts per print cycle, 45° build angle should be avoided.

Edge strength of definitive 3D-printed restorative resin materials

STATEMENT OF THE PROBLEM

With the advent of digital technology in dentistry, manual methods for creating dental restorations are being replaced by digital CAD/CAM processes involving three-dimensional (3D) printing and milling. Marginal degradation and chipping are common issues, yet the literature on the edge strength of 3D-printed restorative materials remains limited. Uncertainties remain regarding the impact of print orientation on edge strength, necessitating further investigation to ensure clinical efficacy.

PURPOSE

The purpose of this study was to evaluate the influence of print orientation on the edge strength of 3D-printed dental restorative resins indicated for definitive and interim use and compare them with milled materials.

MATERIALS AND METHODS

Specimens (14 ×14 ×2 mm) were additively manufactured in three orientations (0, 45, and 90 degrees) using five 3D printed resins: VarseoSmile Crownplus (VCP), Crowntec (CT), Nextdent C&B MFH (ND), Dima C&B temp (DT), and GC temp print (GC). A DLP 3D printer (ASIGA MAX UV) was used, with post-processing parameters set according to manufacturer recommendations. Edge strength was measured at 0.5 mm and 1 mm distance from the edge using a CK 10 testing machine. Specimens were tested in dry conditions (0.5 mm) and after 48 hours of storage in artificial saliva at 37°C (0.5 mm and 1 mm). Failure modes were analysed visually and using optical and scanning electron microscopy. Filler content was assessed using the Ash method, and statistical analysis was conducted using ANOVA. Pearson correlation was used to assess the relationship between filler weight and edge strength.

RESULTS

Due to severe deformation before chipping under load at both distances, data for the 3D-printed and milled interim materials were excluded. The 90-degree printing orientation of definitive materials demonstrated significantly higher edge strength after 48 hours in artificial saliva compared to the 0- and 45-degree orientations (P < 0.001). Significant differences were observed between the 3D printed and milled materials at 0.5 (P < 0.001) mm but not at 1 mm (P ≥ 0.804). Failure modes were predominantly surface indentation without visible cracking (58 %), followed by surface indentation with visible cracking (17 %), edge chipping (0.2 %), and specimen fracture (13 %). A non-significant negative correlation was observed between filler weight and edge strength (r = 0.161, P < 0.680).

CONCLUSIONS

Based on the current findings, 3D printing definitive resin materials at a 90-degree orientation provided increased edge strength. 3D-printed materials can better resist crack propagation compared to milled composites.

CLINICAL IMPLICATIONS

Optimizing the print orientation to 90-degree can improve the edge strength of definitive 3D printed materials.

Effect of aging on optical behavior and color of 3D printing resin-based dental restorative materials

OBJECTIVES

To evaluate the influence of aging on color and optical properties of 3D printing resin-based dental restorative materials.

METHODS

Four 3D printing resin-based dental restorative materials (DFT- Detax Freeprint Temp; FT- Formlabs Temporary CB; FP- Formlabs Permanent Crown; and GCT- GC TempPrint) were evaluated. The structures were printed using digital light processing (DLP) (DFT and GCT groups) and stereolithography (SLA) (FT and FP groups) technologies. Samples (10 × 10 × 1 mm; n = 3) were printed in light (L) and medium (M) shades and at 0° and 90° and then polished to a thickness of 1.00 ± 0.01 mm with silicon carbide (SiC) sandpapers under water cooling. Artificial aging followed the ISO 4892-2 standard. 1) Color differences were evaluated using CIEDE2000 and perceptibility and acceptability thresholds (PT00 and AT00), 2) spectral reflectance (R%) and transmittance (T%) were measured and scattering (S) and absorption (K) coefficients, light reflectivity (RI), infinite optical thickness (X∞) pre- and post-aging were calculated using Kubelka-Munk method and Root Mean Square Error (RMSE) and Goodness of Fit (GFC) were used as performance optical behavior.

RESULTS

1) All 3D-printed dental resins evaluated, irrespectively of the printed angles, showed mean ΔE00 values above AT00 (.ΔE00>1.8), and FT-M and FP-M showed the least color changes among the evaluated materials, 2) GFC<0.999 and RMSE >2 % values were found between pre and post aging for R%, T%, S, K, RI and X∞ properties.

CONCLUSIONS

This study showed poor spectral match and comparative spectral values of R%, T%, S, K, RI and X∞ between after and before aging, resulting in unacceptable color changes. Printing orientation does not influence the change of the optical behavior of the evaluated materials after aging.

CLINICAL SIGNIFICANCE

Aging causes significant changes on the spectral optical behavior for the 3D-printed resin-based restorative materials studied, resulting in clinically unacceptable color changes.

Properties and Behavior of Additively Manufactured Provisional Fixed Dental Prostheses: A Systematic Review on 3D Printing Orientations Relative to Applied Materials and Postprocessing

OBJECTIVES

This systematic review aimed to assess the influence of printing orientations alone and with other parameters, such as applied material and postprocessing, on the physical-mechanical properties and mechanical behavior of provisional fixed dental prostheses (FDPs).

MATERIALS AND METHODS

A comprehensive search of websites such as PubMed, Scopus, Web of Science, and Cochrane was conducted in July 2024. Adhering to PRISMA 2020 guidelines, the studies that investigated the impact of printing orientations on the physical and mechanical properties were included in this review. The modified CONSORT statement was utilized for the risk of bias assessment. A total of 24 records were included; the main build-up angles were horizontal, oblique, and vertical (0°, 45°, and 90°), and other angles such as 30° and 150° were also reported. The data focused on the impact of orientation on 3D-printed products from different materials, applying various postcuring times and artificial aging. Horizontally printed specimens exhibited significantly superior mechanical properties and behavior compared with other angles, while vertically printed specimens displayed the lowest results. Additionally, the material type, amount, and type of fillers and postcuring had the most substantial impacts; zirconia fillers showed more enhanced strength compared to silica fillers, and the mechanical behavior was enhanced with postcuring time of up to 120 min. Optical properties were more related to the materials and technology applied than to printing directions. Polishing of the products enhances surface quality and removes differences from various orientations. Resin specimens exhibited a high susceptibility to staining, irrespective of printing orientation. Furthermore, aging significantly influenced the mechanical properties, gloss, and surface quality of the specimens.

CONCLUSIONS

To achieve high-quality provisional FDPs, it is essential to select a horizontal orientation. Careful selection of materials is necessary, as well as adherence to optimal printing parameters. 3D-printed resin may not yet be suitable for permanent rehabilitation; however, it is appropriate for short- and long-term temporization.

CLINICAL SIGNIFICANCE

The production of dental parts is shifting to additive manufacturing; it is crucial to understand the impact of various parameters on the physical and mechanical behavior of dental parts, particularly provisional restorations, to ensure their durable clinical service.

Dimensional accuracy of additive and subtractive manufactured ceramic-reinforced hybrid composite inlays: a CBCT-based in vitro study

The dimensional accuracy of digitally processed inlays is often questioned because of inherent manufacturing inconsistencies associated with computer-aided design and manufacturing (CAD/CAM). This study aimed to compare the absolute marginal discrepancy (AMD), marginal gap (MG), internal gap (IG), and overall discrepancy (OD) of three-dimensional (3D) printed, milled and conventional inlays. Forty resin dies were 3D-printed from a class II mesiococclusodistal preparation on a typodont and randomly distributed into four groups of 10 each. Optical impressions were taken for three groups to fabricate CAD/CAM inlays: Group PVC, 3D printed VarseoSmile Crownplus; Group PVT, 3D printed VarseoSmile TriniQ; and Group MVE, milled using Vita Enamic. For Group CGP (control), CGP was conventionally fabricated using Gradia Plus. These inlays were stabilized on dies and subjected to cone‒beam computed tomography to measure discrepancies in mesiodistal and buccolingual sectional images. All the discrepancies differed significantly among the groups (one-way ANOVA, P > 0.05). The mean OD was significantly greater in the MVE than in the PVT and CGP; the mean AMD and MG were significantly greater in the PVC than in the PVT (Tukey test, P > 0.05). Compared with the other groups, the 3D-printed inlays, especially the VarseoSmile TriniQ, presented a closer marginal and internal fit.

Three-Dimensional-Printed Photopolymer Resin Materials: A Narrative Review on Their Production Techniques and Applications in Dentistry

Additive manufacturing (3D printing) has transformed dentistry by providing solutions with high precision and accuracy achieved through digital workflows, which facilitate the creation of intricate and personalized structures. Additionally, 3D printing promotes cost efficiency by reducing material waste and errors while enabling on-demand production, minimizing the need for extensive inventories. Recent advancements in 3D-printed resin materials have enhanced their clinical applications by improving mechanical strength, biocompatibility, esthetics, and durability. These innovations have facilitated the fabrication of complex and patient-specific structures, such as dental prostheses, surgical guides, and orthodontic appliances, while significantly reducing production time and material waste. Ongoing research and innovation are expected to strengthen resin properties, including strength, translucency, and durability, broadening their clinical applications. The ongoing evolution of 3D printing technology is poised to play a critical role in driving personalized treatments, streamlining clinical workflows, and shaping the future of dental care. This narrative review comprehensively examines the production techniques and clinical applications of 3D-printed photopolymer resins across various dental specialties, including prosthodontics, orthodontics, pediatric dentistry, maxillofacial surgery, periodontology, endodontics, and conservative dentistry. Additionally, the review provides insight into the transformative impact of these technologies on patient care, highlights existing challenges, and suggests future directions for advancing resin properties and their integration into routine dental practice.

Surface characteristics, cytotoxicity, and microbial adhesion of 3D-printed hybrid resin-ceramic materials for definitive restoration

OBJECTIVE

This study investigated the surface properties, cytotoxicity, and microbial adhesion of 3D-printed specimens made from hybrid resin-ceramic materials intended for use in definitive crowns.

METHODS

Disc-shaped specimens were 3D-printed using six different hybrid resin-ceramic materials recommended for definitive restorations: Crowntec (CT), VarseoSmile Crown Plus (VS), Tera Harz TC-80DP Graphy (TH), C&B Permanent ODS (CB), Formlabs Permanent Crown (FP), and HeyGears (HG). Surface topography, surface roughness, and water contact angle values were measured for each material (n = 6). Cytotoxicity was assessed using direct contact and extract tests on human gingival fibroblasts (n = 4). Additionally, the adhesion of mixed oral bacteria to the surfaces of the specimens was evaluated by counting colony-forming units (CFUs) after a 2-hour incubation period (n = 6).

RESULTS

The TH group exhibited significantly lower surface roughness (Ra: 0.28 ± 0.13 μm) compared to the other materials (CT: 1.87 ± 0.34 μm; VS: 1.13 ± 0.09 μm; CB: 2.91 ± 0.27 μm; FP: 2.50 ± 0.08 μm; HG: 1.50 ± 0.55 μm). The VS group had the highest water contact angle (129.5 ± 1.1°), indicating greater hydrophobicity, in contrast to the other groups (CT: 72.6 ± 2.1°; TH: 75.0 ± 0.3°; CB: 69.1 ± 0.2°; FP: 93.0 ± 1.6°; HG: 77.7 ± 0.3°). Cytotoxicity testing showed no harmful effects, as relative cell viability exceeded 70 %, and lactate dehydrogenase (LDH) release remained below 30 % for all materials. The TH specimens also demonstrated the lowest bacterial adhesion.

CONCLUSIONS

The surface characteristics of the tested resin-ceramic materials varied significantly, with TH showing the smoothest surface and the least bacterial adhesion. All materials were found to be non-toxic. Therefore, TH material has the potential to provide definitive restorations with less microbial adhesion.

CLINICAL SIGNIFICANCE

The type of resin-ceramic material significantly affects the surface properties of 3D-printed specimens. These findings are crucial for selecting the appropriate resin-ceramic material for definitive restorations.

Evaluating the effect of printing parameters on the performance of resin occlusal splints for a sustainable dentistry

Bruxism affects millions worldwide, leading to dental damage like worn teeth and tooth loss. Resin 3D printing presents a promising method for creating intricate, comfortable, and durable occlusal splints. This study examines how printing parameters-layer thickness, orientation angle, and curing time-affect the mechanical (compressive strength, wear rate, impact strength) and physical (water sorption, surface roughness, dimensional accuracy) properties of occlusal splints made from a methacrylate-based resin. A total of 120 specimens were produced according to American Society for Testing and Materials (ASTM) standards using different parametric combinations. The response surface methodology (RSM) was applied to optimize key parameters. The optimum printing parameters for compressive strength include a layer height of 16.5 mm, curing time of 93.6 min, an orientation angle of 12.8º, yielding a compressive strength of 9.05 MPa, wear rate of 159 mm3/min, and impact strength of 71.58 J/m. Similarly, the optimum results for minimum surface roughness (8.013 microns), maximum dimensional accuracy (97.67 and minimum water sorption (0.386%) are achieved at a layer thickness of 16 mm, curing time of 93 min, and orientation angle of 12º. Results show that optimizing resin 3D printing parameters for occlusal splints significantly reduces production costs, particularly in regions with limited access to dental care, while promoting sustainable dental solutions by minimizing the environmental impact of traditional manufacturing methods and enhancing the efficiency of splint production.

Three-Dimensionally-Printed Polymer and Composite Materials for Dental Applications with Focus on Orthodontics

Three-dimensional printing has transformed dentistry by enabling the production of customized dental restorations, aligners, surgical guides, and implants. A variety of polymers and composites are used, each with distinct properties. This review explores materials used in 3D printing for dental applications, focusing on trends identified through a literature search in PubMed, Scopus, and the Web of Science. The most studied areas include 3D-printed crowns, bridges, removable prostheses, surgical guides, and aligners. The development of new materials is still ongoing and also holds great promise in terms of environmentally friendly technologies. Modern manufacturing technologies have a promising future in all areas of dentistry: prosthetics, periodontology, dental and oral surgery, implantology, orthodontics, and regenerative dentistry. However, further studies are needed to safely introduce the latest materials, such as nanodiamond-reinforced PMMA, PLA reinforced with nanohydroxyapatite or magnesium, PLGA composites with tricalcium phosphate and magnesium, and PEEK reinforced with hydroxyapatite or titanium into clinical practice.

The colour stability of 3D-printed, non-invasive restorations after 24 months in vivo - esthetically pleasing or not?

OBJECTIVES

The aim of the present prospective study was to evaluate the colour stability of 3D-printed non-invasive restorations after 24 months in vivo.

METHODS

The study included 29 patients, who received 3D-printed restorations made of a computer-aided design (CAD) / computer aided-manufacturing (CAM) hybrid material (n = 354). Restoration colour of 190 restorations was measured using a spectrophotometer. By applying the CIELAB system, *L (lightness), a* (red-green) and b* (blue-yellow) values were recorded. An evaluation of the colour differences (ΔE) after 6, 12 and 24 months was conducted.

RESULTS

Analysis of colour differences of 3D-printed restorations showed continuous discolouration of the restorations. After one year 34 % and after two years 18 % of the restorations were rated alpha or bravo, indicating no or hardly visible colour change. After two years, 54 % of the evaluated restorations yielded a colour difference with ΔE > 6.8 (delta). More than 82 % of the evaluated restorations showed values between ΔE 3.8 - 6.8 (charlie) and ΔE ˃ 6.8 (delta) after two years.

CONCLUSIONS

3D-printed non-invasive restorations showed an overall reduced colour stability after 24 months in vivo.

CLINICAL SIGNIFICANCE

The present study provides first clinical data regarding 3D-printed restorations. These restorations are recommended for a wearing time of about 6 months.

Evaluation of the clinical application of personalized 3D printing and CAD/CAM resin crowns to replace stainless steel crowns in paediatric dentistry

BACKGROUND

Children with dental caries are treated with stainless steel metal crowns (SSC), but the aesthetics and precision still need to be improved. Currently, both 3D-printed resin crowns (PRC) and computer-aided design/computer-aided manufacture (CAD/CAM) resin crowns (CRC) meet the clinical requirements for crown applications in terms of strength, production time, cost, and aesthetics.

AIM

This study replaced SSC with customized resin crowns by 3D printing and CAD/CAM.

DESIGN

In this study, PRC, CRC, and SSC were used for incisor and molar restorations, and 60 crowns were made with 10 for each group. The fabrication efficiency, surface characteristics, marginal fit, and stability of the two different crowns were evaluated.

RESULTS

PRC and CRC show superior color and surface characteristics, though production times are longer (5.3-12.4 times and 3.3-9.1 times, respectively) than for SSC (p < .05). They, however, can be completed within 80 min. Edge gaps for PRC and CRC are significantly lower (13.0-19.2 times and 13.0-13.7 times) than for SSC (p < .05). All materials exhibit good stability.

CONCLUSION

The 3D-PRCs and CAD/CAM resin crowns may replace SSCs as a potential choice for clinical child caries.

Exploring the optical behavior and relative translucency parameter of CAD-CAM resin-based composites, polymer-infiltrated ceramic network, and feldspar porcelain

OBJECTIVES

To evaluate and compare the optical properties and relative translucency parameter of CAD-CAM restorative materials.

METHODS

Four CAD-CAM materials were evaluated: Lava Ultimate (LU), Grandio Blocs (GB), VITA Enamic (VE), and VITA Mark II (VM). Disk-shaped samples in shade A2-HT were prepared (n = 10) and polished to 1.00 ± 0.01 mm of thickness. Scattering (S), absorption (K), albedo (a) coefficient, transmittance (T%), light reflectivity (RI), infinite optical thickness (X∞), and radiative transfer coefficients (μa, and μ'S) were calculated using Kubelka-Munk method and Thennadil's semi-empirical approach. Root Mean Square Error (RMSE) and Goodness of Fit (GFC) were used as performance optical behavior. Translucency differences were evaluated using the relative translucency parameter (RTP00) and 50:50 % translucency perceptibility and acceptability thresholds (TPT00 and TAT00).

RESULTS

The spectral distribution of S, K, T%, RI, and X∞ was wavelength-dependent. GFC and RMSE values indicated good spectral behavior matches and good comparative spectral values for RI in LU-GB, LU-VE, and GB-VE, and for K in VE-VM. VM displayed the highest scattering values across the wavelengths, while VE and VM showed lower absorption at shorter wavelengths. LU and GB had the highest transmittance. The X∞ values indicated that all 1.0 mm thick materials could be influenced by the background. No good spectral match and no good comparative spectral values were found between CAD-CAM materials and anterior bovine maxillary specimens. VM had the lowest RTP00 values with perceptible and unacceptable differences compared to CAD-CAM materials evaluated.

SIGNIFICANCE

Understanding the optical behavior of different CAD-CAM materials was essential for guiding clinicians in material selection and optimizing their clinical performance. The findings confirm that the different compositions and microstructure impact the optical properties and translucency of CAD-CAM restorative materials.

Composition control of additively manufactured color-graded temporary veneer

OBJECTIVE

The aim of this study was to design and assess composite resin composition for patient-specific esthetic color-graded temporary veneer.

METHODS

Various compositions of composite structures (assorted by Ba2SiO4 filler, TiO2 pigment, and photoinitiator) were prepared via additive manufacturing with 3 s UV exposure (405 nm, 10 W/cm2) per 50 µm thick layer followed by 20 min post-curing treatment after fabrication. The effect of each component on the generated color shades was observed and compared to the commonly used VITA shade guide. The coloration was explored by staining aging treatment under dry, wet, artificial saliva environments, coffee, and cola. The mechanical properties were also evaluated. Color measurement and comparison were done using a colorimeter (lightness (L*), green-red color (a*), and blue-yellow color (b*)), and the changes were calculated by CIEDE2000 (ΔE00), translucency parameter (TP) and whiteness index (WID). The composition color analysis results were then applied to produce a color-graded temporary veneer for mimicking a natural look.

RESULT

Mechanically, all composition result in adequate bending strength with maximum achievable strength of 111.64 MPa. At the same time, the composite color was affected by each constituent differently. The L* value, which indicates the color lightness of the composite, was considerably tuned by the TiO2 pigment, whereas Ba2SiO4 filler only triggered minor changes. Photoinitiator concentration significantly affected the yellowness, indicated by the increased b* value. Similar tendency also observed toward the calculated TP and WID as well. Based on these evaluations, color-graded temporary veneer successfully generated, matching the VITA A3, A2, and B1 shades gradation. However, the stability of the composite color decreased at high amounts of Ba2SiO4 and photoinitiator.

SIGNIFICANCE

The study presents a composition guide for fabricating temporary patient-specific color-graded veneer. It provides insights on the effect of the constituent material on dental esthetics.

Influence of impression method and shoulder design on the marginal adaptation of CAD/CAM nanoceramic resin onlay restorations

Objective

This in-vitro study investigates the influence of two different impression techniques and two shoulder designs on the marginal adaptation of computer-aided design/computer-aided manufacturing restorations.

Methods

Forty mandibular first premolars were cast into dental arch models for this in vitro study. Fragile cusps and concavities on the mesial-buccal-occlusal surfaces were treated, with 2 mm of the occlusal surface removed. Teeth were categorised into two groups based on shoulder preparation. Digital scanning using a 3Shape 3D scanner identified them further for allocation into conventional and digital impression subgroups. The restorations were created from nanoceramic resin blocks using prescribed guidelines. Microscopic evaluation assessed the restoration's marginal adaptation, with data analysed using SPSS 27.0. The level of significance was set at p ≤ 0.05.

Results

Digital intraoral scanning consistently demonstrated smaller marginal gaps than the traditional impression method, regardless of shoulder preparation, with the differences being statistically significant (p < 0.05). Furthermore, shoulder preparation significantly reduced the marginal gaps in both the digital and traditional impression groups (p < 0.05).

Conclusions

The onlay preparation design with a shoulder led to restorations with improved marginal adaptation compared with the design with no shoulder. Direct digital impression techniques produced restorations within a better marginal discrepancy than traditional impressions.

Mechanical properties, cytotoxicity, and protein adsorption of three-dimensionally printable hybrid resin containing zwitterionic polymer and silicate-based composites for dental restorations

OBJECTIVE

To evaluate the mechanical and biological properties of three-dimensionally (3D) printable resins filled with 2-methacryloyloxyethyl phosphorylcholine (MPC) and silicate-based composites and compare with those of a commercially available 3D-printable resin for definitive restorations.

METHODS

A group of 3D-printable hybrid resins (HRs) filled with 6 wt% MPC and three different compositions of silicate-based composites (barium silicate to zirconium silicate ratios: 1.50:1 for HR1, 0.67:1 for HR2, and 0.25:1 for HR3) were prepared. The HR groups were compared with the commercially available unfilled 3D-printable resin (CR) marketed for definitive restorations in terms of flexural strength and modulus, fracture toughness, surface roughness, Vickers hardness, light transmittance (all, n = 15), cytotoxicity, and protein adsorption (both, n = 3). All data were analyzed by using non-parametric Kruskal-Wallis and Dunn's tests (α=0.05).

RESULTS

The HR groups had significantly higher flexural strength, modulus, fracture toughness, and hardness values than the CR (P < 0.001). HR3 had the highest surface roughness and light transmittance among the groups (P ≤ 0.006). None of tested resins showed cytotoxicity. Both HR2 and HR3 showed significantly lower protein adsorption than the CR, with a difference of approximately 60% (P ≤ 0.026).

CONCLUSION

Both HR2 and HR3 exhibited superior mechanical properties (flexural strength, flexural modulus, fracture toughness, and Vickers hardness), light transmittance, and protein-repellent activity than the CR, with no impact on cytotoxicity.

CLINICAL SIGNIFICANCE

The MPC/silicate-based composite-filled resins may be a suitable alternative for definitive restorations, given their higher mechanical properties and promising biological properties to prevent microbial adhesion and subsequent biofilm formation, as well as their non-cytotoxic properties.

Effects of Printing Angle and Post-Curing Time on the Color and Translucency of 3D-Printed Temporary Restoration

In resins produced with a 3D printer, the printing parameters affect the properties of the restoration produced. This study examined the effect of the printing angle and post-curing time on the optical properties of temporary restorations. A total of 135 disk-shaped Formlabs temporary resins (10 × 2 mm) were produced at three different printing angles (0, 45, and 90 degrees) and post-cured for three different times (20, 40, and 60 min) (n = 15). Color and translucency measurements were taken for each group with a spectrophotometer (VITA Easyshade V). The ΔE values between printing angles and curing times influence each other. The highest color change was observed in the groups produced with a 90° printing angle. Considering the post-curing times, the highest color change was observed in the groups cured for 40 min. Increasing the curing time from 20 to 40 min decreases the translucency, whereas further increasing the curing time does not significantly affect the translucency. In terms of the impact on the translucency caused by the printing angles, 0° exhibited a lower translucency compared to other printing angles. During the 3D printing of temporary prostheses, both printing angles and post-curing times can affect their optical properties.

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.

Visual Versus Digital Color Determination of 3D-Printed Teeth as an Exercise in Dental Students' Education

Visual color determination is part of the daily routine in dental practice. However, it is not a part of dental education so far. The aim of this study was to evaluate whether visual or digital tooth color determination of 3D-printed teeth is a reliable tool for inexperienced dentistry students. Preclinical dental students evaluated eleven 3D-printed, tooth-shaped samples (VarseoSmile Crown plus, BEGO, Bremen, Germany) of different color shades. Visual shade determination using a reference scale (3D-Master Toothguide (3DM_TG), VITA Zahnfabrik, Bad Säckingen, Germany), followed by a digital color determination using a spectrophotometer (VITA Easyshade V, (ES_V), VITA Zahnfabrik), was performed. Color deviation was calculated in the Lab* color space (ΔE00) and converted into CIELAB 2000. The results were evaluated using the Mann-Whitney U test and the Wilcoxon Rank Sum test (α = 0.05). Significant differences between visual and digital color determination were proven (p < 0.001). Visual color determination (3DM_TG) showed a mean deviation (ΔE00 ± 95%CI) of 6.49 ± 0.47. Digital color determination (ES_V) showed significantly lower mean deviations of ΔE00 of 1.44 ± 0.58. Digital tooth color measurement using a spectrophotometer was a more reliable tool for the color determination of 3D-printed teeth for inexperienced dentistry students.

The Influence of Dental Virtualization, Restoration Types, and Placement Angles on the Trueness and Contact Space in 3D-Printed Crowns: A Comprehensive Exploration

The current digital dentistry workflow has streamlined dental restoration production, but the effectiveness of digital virtual design and 3D printing for restorations still needs evaluation. This study explores the impact of model-free digital design and 3D-printing placement angles on restorations, including single crowns and long bridges produced with and without casts. The restorations are 3D printed using resin at placement angles of 0°, 60°, and 90°. Each group of samples was replicated ten times, resulting in a total of 120 restorations. The Root Mean Square Error (RMSE) value was used to evaluate the surface integrity of the restoration. In addition, the contact space, edge gap, and occlusal space of restorations produced by different processes were recorded. The results indicate that there was no significant difference in the RMSE value of the crown group (p > 0.05). Changing the bridge restoration angle from 0° to 90° resulted in RMSE values increasing by 2.02 times (without casts) and 2.39 times (with casts). Furthermore, the marginal gaps in the crown group were all less than 60 μm, indicating good adaptation. In contrast, the bridge group showed a significant increase in marginal gaps at higher placement angles (p > 0.05). Based on the findings, virtual fabrication without casts does not compromise the accuracy of dental restorations. When the position of the long bridge exceeds 60 degrees, the error will increase. Therefore, designs without casts and parallel placement result in higher accuracy for dental restorations.