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    Effect of number of supports and build angle on the fabrication and internal fit accuracy of additively manufactured definitive resin-ceramic hybrid crowns
    (Elsevier Sci Ltd, 2023) Cakmak, Gulce; Agovic, Dino; Donmez, Mustafa Borga; Kahveci, Cigdem; de Paula, Marcella Silva; Schimmel, Martin; Yilmaz, Burak
    Objectives: To evaluate the effect of number of supports and build angle on the fabrication and internal fit ac-curacy (trueness and precision) of additively manufactured resin-ceramic hybrid crowns. Methods: A mandibular first molar crown was designed and nested on the build platform of a printer either with a 30 degrees angle between the occlusal surface and the build platform (BLS (less support) and BMS (more support)) or its occlusal surface parallel to the build platform (VLS (less support) and VMS (more support)) to fabricate addi-tively manufactured resin-ceramic hybrid crowns (n = 14). After fabrication, supports were removed by a blinded operator and all crowns were digitized with an intraoral scanner. Fabrication accuracy (overall, external, intaglio occlusal, occlusal, and marginal) was evaluated by using root mean square (RMS) method, while internal fit was evaluated with triple scan method. RMS, average gap, and precision of these data were analyzed (alpha= 0.05).esults: VLS had higher overall deviations than BLS and VMS (P <=.039). VMS had higher occlusal deviations than BLS (P=.033). While BMS and BLS had higher marginal deviations than VLS (P <=.006), BMS also had higher values than VMS (P=.012). BLS led to higher precision than VMS (intaglio occlusal and occlusal surfaces) and VLS (occlusal surface) (P <=.008). VLS led to higher precision than BMS (marginal surface) (P=.027). Average gap values were similar (P=.723); however, BLS resulted in higher precision than VLS (P=.018).Conclusions: Considering their high marginal and occlusal surface trueness, and similar internal occlusal de-viations and average gaps (trueness), clinical fit of resin-ceramic hybrid crowns fabricated with tested parameters may be similar. Reduced number of supports and angled orientation may lead to higher precision of fit. Clinical Significance: Tested resin-ceramic hybrid-printer pair may be used to fabricate crowns with reduced number of supports to maintain occlusal surface integrity without compromising the fabrication accuracy and fit.
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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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    Stainability and translucency of potassium aluminum sulfate applied computer-aided design and computer-aided manufacturing materials after coffee thermocycling
    (Wiley, 2024) Sasany, Rafat; Donmez, Mustafa Borga; de Paula, Marcella Silva; Kahveci, Cigdem; Ceylan, Gozlem; Yilmaz, Burak; Cakmak, Guelce
    Objective: The purpose of this in vitro study was to evaluate the effect of potassium aluminum sulfate (alum) application on the stainability and translucency of computer aided design and computer-aided manufacturing (CAD-CAM) materials after coffee thermocycling (CTC). Materials and Methods: Disk-shaped specimens (& Oslash;10 x 1 mm; N = 200) were fabricated by using additively (Crowntec [CT] and Varseo Smile Crown Plus [VS]) and subtractively manufactured (Brilliant Crios [RCR], CEREC Block [FC], and Vita Enamic [VE]) CAD-CAM materials and polished. All specimens were randomly divided into two groups as alum applied and control (n = 10). All specimens were then subjected to CTC (10,000 cycles at 5-55 degrees C) and color coordinates were measured at each time interval. Color differences (Delta E-00) and relative translucency parameters (RTPs) were calculated and the data were statistically analyzed (a = 0.05). Results: Among tested time intervals, alum applied specimens had their lowest Delta E-00 after alum application (p <= 0.006), except for FC (p = 0.177). In addition, alum applied RCR had lower Delta E-00 values than its control specimens (p = 0.029). Alum applied specimens had their lowest RTP after CTC (p < 0.001) and alum application decreased the RTP of CT (p = 0.010). CTC reduced the RTP of all materials in control groups (p < 0.001). Alum applied CT had higher RTP than its control specimens (p = 0.049). Conclusions: Alum application's effect on color change varied depending on the material and alum mostly resulted in clinically acceptable changes in translucency. CTC led to unacceptable color and translucency changes based on previously reported threshold values.Clinical Significance: Optical properties of CAD-CAM materials and the sustainability of these properties over time is critical for longevity. Alum may improve the color stability of reinforced composite resin when subjected to long-term coffee consumption.
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    Surface roughness, optical properties, and microhardness of additively and subtractively manufactured CAD-CAM materials after brushing and coffee thermal cycling
    (Wiley, 2023) Cakmak, Gulce; Donmez, Mustafa Borga; de Paula, Marcella Silva; Akay, Canan; Fonseca, Manrique; Kahveci, Cigdem; Abou-Ayash, Samir
    Purpose: To evaluate the surface roughness, optical properties, and microhardness of additively or subtractively manufactured CAD-CAM materials after simulated brushing and coffee thermal cycling.Material and methods: Two additively manufactured resins (Crowntec, CT and VarseoSmile Crown Plus, VS) and 3 subtractively manufactured materials (a reinforced composite (Brilliant Crios, BC), a polymer-infiltrated ceramic network (Enamic, VE), and a feldspathic ceramic (Mark II, VM)) were used to fabricate disk-shaped specimens (& Oslash;10x1-mm) (n = 10). Surface roughness, Vickers microhardness, and color coordinates were measured after polishing, while surface roughness was also measured before polishing. Specimens were then subjected to 25000 cycles of brushing and 10000 cycles of coffee thermal cycling, and measurements were repeated after each time interval. Color difference (Delta E-00) and relative translucency parameter (RTP) were calculated. Robust analysis of variance test was used to evaluate surface roughness, Delta E-00, and RTP data, while generalized linear model analysis was used for microhardness data (alpha = 0.05).Results: Material type and time interval interaction affected tested parameters (p <= 0.002). In addition, material type affected all parameters (p < 0.001) other than surface roughness (p = 0.051), and time interval affected surface roughness and microhardness values (p < 0.001). Tested materials mostly had their highest surface roughness before polishing (p <= 0.026); however, there was no clear trend regarding the roughness of materials within different time intervals along with Delta E00 and RTP values within materials or time intervals. VS and CT had the lowest microhardness regardless of the time interval, while the remaining materials were listed as VM, VE, and BC in decreasing order (p < 0.001). Coffee thermal cycling only reduced the microhardness of VM (p < 0.001).Conclusions: Tested additively manufactured resins can be considered more susceptible to simulated brushing and coffee thermal cycling than the other materials, given the fact that their surface roughness and Delta E00 values were higher than previously reported acceptability thresholds and because they had the lowest microhardness after all procedures were complete.