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 litera- ture 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 proper- ties and their study are of outmost importance to create materials that mimic natural tooth to allow clinicians to obtain esthetically pleasant restorations.i + D + I Government of Andalusia 2020, Spain (P20-00200)University of Granada, Spain (A.TEP.280. UGR18)Spanish Ministry of Science, Innovation and Universities (PGC2018-101904-A-100)State of Rio Grande do Sul, FAPERGS (grant#19/2551-0001721-9)

Effect of thickness on color and translucency of a multi-color polymer-infiltrated ceramic-network material

Objectives: To evaluate the effect of thickness on color and translucency of a multi-color polymer-infiltrated ceramic-network (PICN) material. Methods: Specimens of 0.5, 1.0, 1.5 mm thicknesses were obtained by sectioning VITA ENAMIC® multiColor (E-MC) High Translucent CAD-CAM blocks (1M1-HT, 1M2-HT, 2M2-HT, 3M2-HT, and 4M2-HT). Spectral reflectance and color coordinates were measured on white and black backgrounds using a spectroradiometer, CIE D65 illuminant and CIE 45 /0 geometry. CIEDE2000 color and translucency differences (ΔE00 and ΔTP00) between thicknesses and adjacent layers were evaluated using their respective 50:50% perceptibility and acceptability thresholds (PT00 and AT00). Results: In general, ΔE00 between thicknesses for all shades and layers were above AT00 in general. Chroma decreased from cervical to incisal layers with statistically significant differences (p < 0.05), and ΔE00 between sequential layers were above PT00, for all shades and thicknesses. TP00 decreased from 0.5 to 1.5 mm and increased from cervical to incisal layers for all shades with statically significant translucency differ- ences (p < 0.05). In general, for all thicknesses, TPT00 < ΔTP00 < TAT00 for sequential layers. Conclusions: The gradient in color and translucency of E-MC PICN material was influenced by the thickness of the CAD-CAM block. In addition, color and TP transi- tion values between the layers depends on the thickness and shade. Clinical significance: The effect of thickness must be taken into account by dental technicians and dentists when CAD-CAM multicolor PICN materials are used.University of Granada, Grant/Award Number: A.TEP.280.UGR18Spanish Ministry of Science, Innovation and Universities, Grant/ Award Number: PGC2018-101904-A-I00Government of Andalusia, Spain, Grant/Award Number: P20-0020

The influence of printing angle on color and translucency of 3D printed resins for dental restorations

Objectives: To evaluate the influence of printing orientation on color and translucency of 3D printing restorative resins. Methods: Four 3D printing resin systems in the available shades (DFT-Detax Freeprint Temp- A1, A2,A3; FPFormlabs Permanent Crown- A2,A3,B1,C2; FT- Formlabs Temporary CB- A2,A3,B1,C2; GCT-GC TemporaryLight, Medium) were evaluated. Three samples (10x10x1.2 mm) from each material were printed at two different printing orientations (0 degrees and 90 degrees) and polished to 1.00 +/- 0,01 mm of thickness. Spectral reflectance was measured against black background using a calibrated spectroradiometer, CIE D65 standard illuminant and the 45 degrees/0 degrees geometry. Color and translucency differences were evaluated using CIEDE2000 metric (AE00) and 50:50% perceptibility (PT00 and TPT00) and acceptability (AT00 and TAT00) thresholds. Results: In general, color changes due to printing orientation at (0 degrees and 90 degrees) were mainly produced by AL* or AC* . AE00 were above PT00 for all DFT shades, FP-B1, FP-C2, FT-A2 and FT-B1. Only for DFT-1, AE00 was above AT00. ARTP00 values were above TPT00 for DFT-A1, DFT-A3, FP-B1 and FT-B1, but lower than TAT00. The direction of the changes in translucency (ARTP00) depends on the material and shade. Significance: The selection of building orientation (0 degrees and 90 degrees) for the 3D printed resins influence the visual color and translucency and therefore their esthetic appearance. These aspects should be considered when printing dental restorations using the evaluated materials.FEDER/Government of Andalusia P20-00200Spanish Government PGC2018-101904-A-100State of Rio Grande do Sul, FAPERGS 19/2551-0001721-9Universidad de Granada/CBU

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

The authors also acknowledge Detax GmbH, Formlabs Inc. and GC Corporation for providing the polymer-based 3D printing restorative resins used in this study.Objectives To evaluate the influence of thickness and printing angle on the optical properties of 3D-printed dental restorative resins. Methods Four 3D printing resin systems were evaluated: DFT-Detax Freeprint Temp; FP- Formlabs Permanent Crown; FP- Formlabs Temporary CB; and GCT- GC Temporary-. Samples from each material were printed at 0° and 90°, and polished up to 0.5, 1.0, 1.5 and 2.0 mm thickness. Scattering (S), absorption (K) and albedo (a) coefficients, transmittance (T%), light reflectivity (RI) and infinite optical thickness ( ) were calculated using Kubelka-Munk’s model. Data were statistically analyzed using Kruskal–Wallis¸ Mann-Whitney tests, and VAF coefficient. Results The spectral distribution on S, K, T%, RI, were wavelength dependent. Although the spectral behaviors were similar for all the specimens evaluated, the values of S, K, T% and presented significant differences between specimen thicknesses for all the materials used and for both printing orientations. Values for S and K increased, and T% and decreased. Significant differences between 0° and 90° were found for RI values at 0.5 and 1.0 mm thick samples, for S and K at 2.0 mm, for at 0.5 and 1.0 mm for DFT, and at 0.5 mm for FT. Conclusions Optical properties of 3D-printed restorative resins vary between thicknesses, and could be affected by the building orientation. Therefore, these factors should be considered in order to improve the biomimetic potential of 3D-printed dental restorative resins. Clinical significance Understanding the optical behavior of the 3D-printed restorative resins is essential to optimize their clinical performance.FEDER/ Government of Andalusia P20-00200support from the FEDER/ Government of Andalusia P20-00200 and State of Rio Grande do Sul, FAPERGS (grant #19/2551-0001721-9)Funding for open access charge: Universidad de Granada / CBU

Optical and colorimetric evaluation of a multi-color polymer-infiltrated ceramic-network material

Objective To evaluate color, translucency parameter and optical properties (scattering (S), absorption (K) and transmittance (T)) of a multi-color polymer-infiltrated ceramic-network (PICN) material. Methods Samples of shades 1M1-HT, 1M2-HT, 2M2-HT, 3M2-HT, and 4M2-HT from VITA ENAMIC® multiColor (E-MC) High Translucent were fabricated (n = 3). CAD-CAM blocks were cut and polished to 1.00 ± 0.01 mm of thickness. Diffuse reflectance and color coordinates were measured against white and black backgrounds, using a calibrated spectroradiometer, CIE D65 illuminant and the CIE 45°/0° geometry. Color and translucency differences were evaluated using 50:50% perceptibility (PT and TPT) and 50:50% acceptability (AT and TAT) thresholds. S and K coefficients and T were calculated using Kubelka–Munk’s equations. Data was statistically analyzed using Kruskal–Wallis, Mann–Whitney tests, and VAF coefficient. Result Mean C* and b* values increased from incisal to cervical layers with statistically significant differences (p < 0.05). In general, ΔE00 between sequential layers were above PT for all shades. In addition, translucency parameter (TP) increased from cervical to incisal and ΔTP00 values were greater than TPT00 and lower than TAT00 between all sequential layers. Layers from all shades showed similar spectral behavior for S (97.4% ≤ VAF), K (85.0% ≤ VAF) coefficients and T (95.3% ≤ VAF). However, these values presented significant differences (p < 0.05) from cervical to incisal layers. Significance The gradient in color and translucency of this novel CAD-CAM multi-color PICN material can assist dental technicians and dentists to reach greater esthetics than the pre-existing CAD-CAM monolithicmaterials.Project JA TEP-1136 from “Junta de Andalucía”, SpainMAT2013-43946R from the Spanish Ministry of Economy and CompetitivenessCNPq Brazil grant #302587/2017-

Optical and mechanical characterization of 3D-printing polymer-based resin materials for fixed dental restorations: influence of building orientation

El color y las propiedades ópticas de los materiales juegan un papel muy importante cuando se intenta emular la apariencia natural de la dentición. Un amplio conocimiento a cerca de las características del color basadas en la percepción visual y del aspecto estético de las resinas dentales, adquirido a partir de sus propiedades ópticas, podría ayudar a los clínicos en la selección del material y el shade adecuados, facilitando así la obtención de restauraciones dentales con apariencia natural. Las resinas de impresión 3D son utilizadas habitualmente para la fabricación de restauraciones parciales fijas provisionales, que deben satisfacer adecuadamente las demandas estéticas tanto de los pacientes como de los clínicos. Sin embargo, apenas existen estudios en la bibliografía científica actual a cerca de las propiedades ópticas y características colorimétricas de los materiales dentales restauradores de impresión 3D. Diversos factores, tales como los parámetros de impresión, el espesor de capa y la impresora específica que se utilice, influyen en las características finales del material. El ángulo de impresión, orientación de impresión o dirección de construcción, haciendo referencia a la orientación de construcción de las capas, es un parámetro de gran relevancia en las etapas iniciales de los procesos de fabricación aditiva, que podría permitir modular la anisotropía y las vulnerabilidades físicas inherentes a los materiales impresos, derivadas de las técnicas de fabricación por capas. Se ha demostrado que la orientación de impresión influye tanto en las propiedades mecánicas como en la precisión de impresión de las resinas restauradoras de impresión 3D. En este sentido, la caracterización del comportamiento mecánico de los materiales dentales poliméricos comprende tanto la evaluación de la resistencia la flexión (σf), como del módulo de elasticidad (E). Además, el comportamiento colorimétrico y las propiedades ópticas de estas resinas también podrían verse afectados por la orientación de impresión de las estructuras de resina. Hasta ahora carecemos de información suficiente en relación a cómo la orientación de impresión y el espesor estructural influyen en el color, la translucidez y otras propiedades ópticas (tales como la dispersión, la absorción, la reflectancia y la transmitancia de la luz) de las resinas de impresión 3D, lo cual justifica la necesidad de realizar futuros estudios al respecto. Esta información resulta esencial para manejar adecuadamente estos materiales, satisfaciendo las expectativas estéticas, cada vez más elevadas, de los pacientes. En este contexto, la presente Tesis Doctoral está integrada por varios estudios diseñados y llevados a cabo para abordar y resolver las cuestiones mencionadas anteriormente.Color and optical properties of materials hold special significance in emulating the natural appearance of teeth. A comprehensive understanding of the characteristics of color based on visual perception and the aesthetic appearance of dental resins, derived from their optical properties, can assist dental practitioners in the selection of suitable materials and shades, facilitating the attainment of a lifelike appearance in dental restorations. 3D printing resins are frequently used for the manufacture of temporary fixed partial restorations, which should fullfil adequately the esthetic demands of patients and clinicians. However, studies addressing questions concerning color characteristics and optical properties of 3D printed restorative dental materials are scarce in the current literature. Diverse factors, including printing parameters, layer thickness, and the specific printer employed, exert influence over the final material characteristics. The printing angle, printing orientation, or build direction, which refers to the orientation of layer construction, stands as a crucial parameter during the initial stages of additive manufacturing (AM) processes, capable of aiding in modulating the anisotropy and physical vulnerabilities inherent in printed materials produced through layering fabrication techniques. It has been demonstrated that the printing orientation has an influence on both the mechanical properties and the printing accuracy of 3D-printed restorative resins. In this sense, mechanical behavior characterization of polymeric dental materials involves the assessment of both flexural strength (σf) and elastic or Young's modulus (E). Furthermore, the colorimetric behavior and optical properties of these resins could also be affected by the printing orientation of the resin structures. To date, there is a lack of information regarding how printing orientation and structural thickness affects the color, translucency and other optical properties (including scattering, absorption, light reflectance and transmittance) of 3D printed resins, justifying the need for further studies. This information is crucial for an effective management of these materials, and to meet the growing esthetic expectations of patients. In this context, the present Doctoral Thesis involves several studies designed and carried out to address and resolve the mentioned issues.Tesis Univ. Granada. ; P20-00200 (i + D + I Government of Andalusia 2020, Spain); A-TEP-280- 2020-2021 (Feder- Junta de Andalucía, 2020-2021) ; CNPq ARC #2019 L2 (CNP Brasil, 2019-2021