Influence of Polymerization Postprocessing Procedures on the Accuracy of Additively Manufactured Dental Model Material.

PURPOSE: To measure the influence of postpolymerization condition (dry and water-submerged) and time (2, 10, 20, and 40 minutes) on the accuracy of additively manufactured model material. MATERIALS AND METHODS: A bar standard tessellation language (STL) file was used to manufacture all the resin specimens using a 3D printer. Two groups (n = 80 each) were created based on postpolymerization condition: dry (D group) and water-submerged (W group). Each group was then divided into four subgroups (D1 to D4 and W1 to W4; n = 20 each), which were each assigned a postpolymerizing time (2, 10, 20, and 40 minutes). The specimens' dimensions were measured using a low-force digital caliper. The volume was calculated as follows: V = l × w × h. Shapiro-Wilk test revealed that the data were not normally distributed. Data were analyzed using Kruskal-Wallis and pairwise Mann-Whitney U tests (α = .05). RESULTS: Significant differences in length, width, height, and volume were found among the subgroups (P < .0018). In all groups, the width dimension (x-axis) presented less accuracy compared to height (z-axis) and length (y-axis) (P < .0018). The D2 and D4 subgroups obtained the closest dimensions to the virtual design, and there were no significant differences between these subgroups (P < .0018). The dry condition showed higher manufacturing accuracy than the water-submerged condition. In the water-submerged subgroups, the highest accuracy was obtained in the W2 and W4 subgroups (P < .0018). CONCLUSIONS: Postpolymerization condition and time influenced the accuracy of the material tested. The dry postpolymerization condition with times of 10 and 40 minutes obtained the highest accuracy.

Biaxial flexural strength and Weibull characteristics of a resin ceramic material after thermal-cycling.

PURPOSE: The purpose of this in vitro study was to compare the flexural strength and Weibull characteristics of 3 different resin-ceramic materials with a zirconia-reinforced lithium silicate material after thermal-cycling. MATERIAL AND METHODS: Four different computer-aided design and computer-aided manufacturing restorative materials (Vita Enamic, Lava Ultimate, Crystal Ultra, and Vita Suprinity) were tested. A total of 40 Ø12×1.2-mm disks were prepared and divided into 4 groups (n = 10). Their flexural strength was evaluated after 5000 thermal-cycles with a 4-point biaxial flexure test using a universal testing machine. The Weibull modulus and probability of failure were also determined from the biaxial flexural strength data. Data were analyzed with one-way ANOVA and the Tukey pairwise comparison test (α = 0.05). RESULTS: Significant differences were found among the materials in terms of biaxial flexural strength (p < 0.05). Vita Suprinity had the highest mean ±standard deviation flexural strength (289.1 ± 15.1 MPa), and Vita Enamic had the lowest (100.0 ± 3.2 MPa). The highest Weibull modulus was calculated for Crystal Ultra, followed by Vita Enamic, Lava Ultimate, and Vita Suprinity. CONCLUSION: Vita Suprinity had the highest flexural strength when compared with the other materials tested. Crystal Ultra had the highest flexural strength among the resin-ceramic materials. The highest Weibull modulus was calculated for Crystal Ultra and the lowest for Vita Suprinity.

Manufacturing accuracy and volumetric changes of stereolithography additively manufactured zirconia with different porosities.

STATEMENT OF PROBLEM: When compared with subtractive fabricating methods, additive manufacturing (AM) technologies are capable of fabricating complex geometries with different material porosities. However, the manufacturing accuracy and shrinkage of the stereolithography (SLA) AM zirconia with different porosities are unclear. PURPOSE: The purpose of this in vitro study was to measure the manufacturing accuracy and volumetric changes of AM zirconia specimens with porosities of 0%, 20%, and 40%. MATERIAL AND METHODS: A digital design of a bar (25×4×3 mm) was obtained by using an open-source software program (Blender, version 2.77a; The Blender Foundation). The standard tessellation language (STL) file was exported. Three groups were created based on the material porosity: 0% porosity (0% group), 20% porosity (20% group), and 40% porosity (40% group). The STL was used to manufacture all the specimens by using an SLA ceramic printer (CeraMaker 900; 3DCeram Co) and zirconia material (3DMix ZrO2 paste; 3DCeram Co) (n=20). After manufacturing, the specimens were cleaned of the green parts by using a semiautomated cleaning station. Subsequently, debinding procedures was completed in a furnace at 600 °C. The sintering procedures varied among the groups to achieve different porosities. For the 0% group, the ZrO2 was sintered in a furnace at 1450 °C, and for the 20% and 40% groups, the sintering temperature varied between 1450 °C and 1225 °C. The specimen dimensions (length, width, and height) were measured 3 times with digital calipers, and the mean value was determined. The manufacturing volume shrinkage (%) was calculated by using the digital design of the bar and the achieved AM dimensions of the specimens. The Shapiro-Wilk test revealed that the data were not normally distributed. Therefore, the data were analyzed by using the Kruskal-Wallis followed by pairwise Mann-Whitney U tests (α=.05). RESULTS: The Kruskal-Wallis test demonstrated significant differences among the groups in length, width, and height (P<.001). The Mann-Whitney U test indicated significant differences in pairwise comparisons of length, width, and height among the 3 groups (P<.001). The 0% group obtained a median ±interquartile range values of 20.92 ±0.14 mm in length, 3.43 ±0.07 mm in width, and 2.39 ±0.03 mm in height; the 20% group obtained 22.81 ±0.29 mm in length, 3.74 ±0.07 mm in width, and 2.62 ±0.05 mm in height; and the 40% group presented 25.11 ±0.13 mm in length, 4.14 ±0.08 mm in width, and 2.96 ±0.02 mm in height. Significant differences in manufacturing volumetric changes were encountered among the 3 groups (P<.001). In all groups, volumetric changes in the length, width, and height were not uniform, being higher in the z-axis direction compared with the x- and y-axis. The manufacturing volumetric changes varied from -20.33 ±1.00% to +3.5 ±2.00%. CONCLUSIONS: The 40%-porosity group obtained the highest manufacturing accuracy and the lowest manufacturing volume change, followed by the 20%-porosity and the 0%-porosity groups. An uneven manufacturing volume change in the x-, y-, and z-axis was observed. However, none of the groups tested were able to perfectly match the virtual design of the specimens.

Fabricating a dual-material, vat-polymerized, additively manufactured static implant surgical guide: A dental technique.

Protocols with static computer-aided implant placement provide more tangible clinical advantages than conventional implant placement methods. A technique to manufacture a dual-material implant surgical guide by using a vat-polymerization printer is described. The implant surgical guide combined a resilient intaglio and hard exterior surface. The technique should minimize the clinical adjustments needed to ensure fit and improve patient comfort.

Additively manufactured scan body for transferring a virtual 3-dimensional representation to a digital articulator for completely edentulous patients.

A technique is described for obtaining a virtual 3-dimensional representation of completely edentulous patients with the virtual definitive casts mounted on the virtual articulator. An additively manufactured intraoral scan body was developed to record the definitive maxillary and mandibular casts and gothic arch interocclusal registration. The intraoral scan body guided the integration of the digital definitive casts and facial scans to obtain the virtual 3-dimensional patient's representation and facilitated the transfer of the definitive casts to the virtual articulator.

Additively Manufactured Ingot for Interim Dental Restorations Fabrication Using a Chairside Milling Machine.

This manuscript describes a technique to fabricate additively manufactured ingots for producing tooth- and implant-supported interim dental restorations using a chairside milling machine. The technique aimed to ease the additively manufactured interim restoration's manufacturing by using a chairside milling machine, optimize the manufacturing workflow time, and eliminate the surface roughness of additively manufactured restorations.

Influence of the Rinsing Postprocessing Procedures on the Manufacturing Accuracy of Vat-Polymerized Dental Model Material.

PURPOSE: To evaluate the influence of rinsing solvents, namely isopropyl alcohol (IPA) and tripropylene glycol monomethyl ether (TPM), and rinsing times (5-, 7-, 9-, and 11-minutes) for the postprocessing procedures on the manufacturing accuracy of an additively manufactured dental model resin material. MATERIAL AND METHODS: The standard tessellation language (STL file) of the digital design of a bar (15 mm × 4 mm × 3 mm) was obtained. A resin dental material (E-Model Light; Envisiontec, Dearborn, MI) and a 3D printer (VIDA HD; Envisiontec) was selected to manufacture all the specimens using the STL file following the recommended printing parameters at a room temperature of 23 °C. Two groups were generated based on the rinsing solvent used on the postprocessing procedures, namely isopropyl alcohol (IPA-group) and tripropylene glycol monomethyl ether (TPM-group). Each group was further divided into 4 subgroups (IPA-1 to IPA-4 and TPM-1 to TPM-4) depending on the rinsing time performed (5-, 7-, 9-, and 11-minutes). Twenty specimens per subgroup were fabricated. The dimensions (length, width, and height) of all the specimens were measured using a low force digital caliper (Absolute Low Force Caliper Series 573; Mitutoyo, Takatsu-ku, Kawasaki, Kanagawa). Each measurement was performed 3 times and the mean value determined. The volume of each specimen was calculated using the formula V = l × w × h. Shapiro-Wilk test revealed that the data were not normally distributed. Data were analyzed using Kruskal-Wallis (α = 0.05), followed by pairwise Mann-Whitney U tests (α = 0.0018). RESULTS: The IPA groups obtained significantly lower trueness and precision values compared with TPM groups (p < 0.0018). Among the IPA groups, IPA-1 subgroup obtained the highest trueness and precision values compared to the rest of the IPA subgroups. The TPM-1 and TPM-2 subgroups obtained the highest trueness and prevision values among the TPM group and among all the groups tested. No significant difference was found between the TMP-1 and TPM-2 subgroups (p > 0.0018). CONCLUSIONS: None of the manufacturing workflows tested were able to manufacture a perfect match of the bar virtual design dimensions. TPM solvent group obtained higher trueness and precision values compared to the IPA solvent group. The IPA-1 subgroup that replicated the manufacturer´s recommendations obtained the highest manufacturing accuracy among the IPA subgroup. TPM solvent used in a rinsing ultrasonic bath between 3 and 4 minutes followed by a second ultrasonic clean bath between 2 and 3 minutes of the just printed vat polymerized dental model specimens obtained the highest manufacturing accuracy values.