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    Additive or subtractive manufacturing of crown patterns used for pressing or casting: A trueness analysis
    (Elsevier Science, 2022) Çakmak, Gülce; Dönmez, Mustafa Borga; Cuellar, Alfonso Rodrigues; Kahveci, Çiğdem; Schimmel, Martin; Yılmaz, Burak
    Objectives: To investigate the effect of subtractive and additive manufacturing techniques on the trueness of crown patterns used for pressing or casting. Material and Methods: A complete-coverage mandibular right first molar crown was designed in standard tessellation language (STL) format. This STL served as the control (C- STL) and was used to fabricate 30 crown patterns in 3D-printed resin (PR, ProArt Print Wax), millable wax suitable for casting (BW, ProArt CAD Wax Blue), and millable wax suitable for pressing (YW, ProArt CAD Wax Yellow) (n=10). Subtractively manufactured patterns were fabricated by using a 5-axis milling unit (PrograMill PM7), while 3D-printed patterns were fabricated by using a digital light processing-based 3D printer (PrograPrint PR5; Ivoclar Vivadent, Schaan, Liechtenstein). All fabricated patterns were digitized by using an intraoral scanner (CEREC Primescan SW 5.2) to generate test-STLs. C-STL and test-STLs were transferred into a 3D analysis software (Medit Link v 2.4.4). Trueness evaluation was performed at 4 different surfaces (external, intaglio with margin, marginal, and intaglio without margin) and for complete scan meshes (overall) by using the root mean square (RMS) method. Data were analyzed with Kruskal-Wallis and Mann-Whitney U tests (?=.05). Results: RMS values varied significantly at all surfaces (P<.001), except for marginal surface (P=.151). PR had the highest RMS values at external surface (P?.007), intaglio surfaces (with (P?.003) and without margin (P?.005)), and overall (P?.01). No significant differences were observed between YW and BW (P?.223). Conclusion: Patterns fabricated by using subtractive manufacturing exhibited high trueness. The deviation values, in general, were small, particularly at intaglio and marginal surfaces; thus, clinical difference in crown-fit may be negligible using additive or subtractive technique. Clinical Significance The fit of definitive crowns may be similar when tested crown patterns are additively or subtractively manufactured. However, crowns fabricated by using tested 3D-printed resin patterns may require more chairside adjustments compared with those fabricated by using subtractively manufactured wax patterns.
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    Effect of printing layer thickness on the trueness and fit of additively manufactured removable dies
    (Elsevier, 2022) Yılmaz, Burak; Dönmez, Mustafa Borga; Kahveci, Çiğdem; Cuellar, Alfonso Rodrigues; de Paula, Marcella Silva; Schimmel, Martin; Abou-Ayash, Samirl; Çakmak, Gülce
    Statement of problem: Additive manufacturing is commonly used for the fabrication of definitive casts with removable dies. However, how the trueness and fit of removable dies are affected by printing layer thickness is lacking. Purpose: The purpose of this in vitro study was to investigate the trueness and fit of additively manufactured removable dies printed in different layer thicknesses. Material and methods: A mandibular cast with a prepared right first molar tooth was digitized (CEREC Primescan), and its standard tessellation language (STL) file was imported into a software program (DentalCAD 3.0). A removable die (D-STL) and a hollow cast with (M-STL) or without the die (SM-STL) were designed. D-STL and SM-STL were imported into a nesting software program (Composer), and 45 removable dies in 3 layer thicknesses (100 ?m, 50 ?m, and 50 to 100 ?m) (n=15) and 1 cast (100-?m) were additively manufactured. Each removable die (TD-STLs), the cast with each die (TM-STLs), and the cast without the die (TSM-STL) were digitized by using the same scanner. All STL files were imported into a software program (Medit Link v 2.4.4), and TD-STLs were superimposed over D-STL. The root mean square (RMS) method was used to analyze the trueness of the dies at 2 different areas (crown and root portion) and as a complete unit (overall). Overall RMS values of the cast with and without the die were also calculated after superimposing TM-STLs over M-STL. The fit of the dies in the cast was evaluated by using a triple-scan protocol to measure deviations at 5 different points (point M: most mesial point of the margin; point TM: tip of the mesial cusp; point O: deepest point of the occlusal fossa; point TD: tip of the distal cusp; point D: most distal point of the margin) on the crown portion. One-way ANOVA and Tukey honestly significant difference tests were used to evaluate data (?=.05). Results: The RMS values of removable dies showed significant differences at each area (P?.002). The 50- to 100-?m group had higher overall RMS values than the 100-?m group (P=.017). The 100-?m group had the highest RMS values for the crown portion (P?.019), while the 50-?m group had the highest RMS values for the root portion (P<.001). The 50-?m group had the lowest RMS values for the crown portion when the die was in the cast (P<.001). Except for point TM (P=.228), significant differences were observed among the test groups at all points (P<.001). The 50-?m group had the lowest distance deviations at points M, TD, and D (P?.005), while the 100-?m group had the highest distance deviations at points O and D (P?.010). Conclusions: Removable dies fabricated by using a 100-?m or 50- to 100-?m combined layer thickness had trueness that was either similar to or better than that of dies fabricated with a 50-?m layer thickness. When the die was on the cast, the 50-?m layer thickness resulted in the best crown portion trueness. However, because the deviation differences among groups were clinically small, the 100-?m layer thickness can be considered for the efficient fabrication of removable dies when the tested printer and resin are used. © 2022 Editorial Council for the Journal of Prosthetic Dentistry
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    Trueness of crowns fabricated by using additively and subtractively manufactured resin-based CAD-CAM materials
    (Elsevier, 2022) Çakmak, Gülce; Rusa, Ana Maria; Dönmez, Mustafa Borga; Akay, Canan; Kahveci, Çiğdem; Yılmaz, Burak
    Statement of problem: Advancements in digital dental technologies have enabled the use of different resin-based materials that can be fabricated either additively or subtractively. However, knowledge on the fabrication trueness of these materials is scarce. Purpose: The purpose of this in vitro study was to investigate the trueness of crowns fabricated by using different resin-based computer-aided design and computer-aided manufacturing (CAD-CAM) materials. Material and methods: A complete crown for a mandibular right first molar with a 30-?m cement space was designed in standard tessellation language (STL) format. This master STL (MC-STL) was used to fabricate 40 complete crowns with 4 different resin-based CAD-CAM materials and either additive (Crowntec [MS]) or subtractive techniques (Brilliant Crios [BC], breCAM.monoCOM [PMMA], and G-CAM [GR]; n=10). All crowns were digitized with an intraoral scanner (CEREC Primescan SW 5.2) to generate their STL files (TC-STLs). MC-STL and TC-STLs were transferred into a 3-dimensional analysis software program (Medit Link v2.4.4), and a trueness (overall, external, occlusal, intaglio occlusal, and marginal) analysis was performed by using the root mean square (RMS) method. The Kruskal-Wallis and Dunn tests were performed to analyze data (?=.05). Results: The test groups had significantly different deviations on all surfaces (P?.001). MS crowns had higher overall (P?.007) and external surface (P?.001) deviations than GR and PMMA crowns, while the differences between GR and PMMA crowns were not significant (P?.441). BC crowns had higher external surface deviations than GR crowns (P=.005), higher occlusal deviations than GR and MS crowns (P?.007), and higher intaglio occlusal deviations than GR and MS crowns (P?.009). However, BC crowns had lower marginal deviations than MS and GR crowns (P?.018). Conclusions: The brand of resin-based CAD-CAM materials affected the trueness of crowns. Additively manufactured crowns (MS) mostly had lower overall and external surface trueness than the other groups. Nevertheless, the deviation values of occlusal, intaglio occlusal, and marginal trueness were generally small; thus, the effect of the tested materials on clinical crown fit may be negligible. © 2022 Editorial Council for the Journal of Prosthetic Dentistry