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    Effect of coffee thermal cycling on the surface properties and stainability of additively manufactured denture base resins in different layer thicknesses
    (Wiley, 2023) Cakmak, Guelce; Asadolahi, Nura Watson; Schimmel, Martin; Molinero-Mourelle, Pedro; Akay, Canan; Donmez, Mustafa Borga; Yilmaz, Burak
    Purpose: To compare the effect of coffee thermal cycling on surface roughness (Ra), Vickers microhardness (MH), and stainability of denture base resins additively manufactured in different layer thicknesses with those of subtractively manufactured denture base materials.Materials and methods: Eighty disk-shaped specimens (& Oslash;10x2 mm) were fabricated from two subtractively (Merz M-PM [SM-M] and G-CAM [SM-G]) and three additively (NextDent 3D+ [50 mu m, AM-N-50; 100 mu m, AM-N-100], FREEPRINT Denture [50 mu m, AM-F-50; 100 mu m, AM-F-100], and Denturetec [50 mu m, AM-S-50; 100 mu m, AM-S-100]) manufactured denture base materials (n = 10). Ra measurements were performed before and after polishing by using a non-contact optical profilometer, while MH values and color coordinates were measured after polishing. Specimens were then subjected to 5000 cycles of coffee thermal cycling, all measurements were repeated, and color differences (Delta E00) were calculated. A linear mixed effect model was used to analyze Ra and MH data, while one-way analysis of variance was used to analyze Delta E00 data (alpha = 0.05). Ra values were further evaluated according to a clinically acceptable threshold of 0.2 mu m, while Delta E00 values were evaluated according to perceptibility (1.72 units) and acceptability (4.08 units) thresholds. The interaction between the material type and the time interval affected both Ra and MH (p <= 0.001). Tested materials had their highest Ra before polishing (p <= 0.029). Before polishing, AM-F-100 had the highest, and SM-M and SM-G had the lowest Ra (p < 0.001). After polishing and after coffee thermal cycling, SM-G mostly had lower Ra than those of other materials (p <= 0.036). SM-G mostly had higher MH than that of other materials before and after coffee thermal cycling (p <= 0.025). Coffee thermal cycling reduced the MH of SM-M and increased that of AM-S-100 (p <= 0.024). AM-N-100 had higher Delta E00 than AM-F, AM-S-100, and SM-G (p <= 0.009), while AM-F and SM-G had lower Delta E00 than AM-S-50 and AM-N-50 (p <= 0.024).Conclusions: Polishing reduced the surface roughness of all materials, whereas the effect of coffee thermal cycling was nonsignificant. Most of the tested materials had acceptable surface roughness after polishing and after coffee thermal cycling according to the reported threshold. Layer thickness only affected the microhardness of tested additively manufactured resins, which was material-dependent. Subtractively manufactured specimens mostly had high microhardness and that of nonreinforced subtractively manufactured resin decreased after coffee thermal cycling. When reported color thresholds are considered, all materials had acceptable color stability.
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    Effect of internal connection type and screw channel angle on the screw stability of anterior implant-supported zirconia crowns
    (Wiley, 2023) Cakmak, Guelce; Guven, Mehmet Esad; Donmez, Mustafa Borga; Kahveci, Cigdem; Schimmel, Martin; Abou-Ayash, Samir; Yilmaz, Burak
    ObjectivesTo investigate the effect of implant-abutment connection and screw channel angle on screw stability by comparing a newly introduced and an established connection, before and after cyclic loading.Materials and MethodsImplants (N = 44) with Torcfit (TF) or Crossfit (CF) connection were divided to be restored with a straight (CFS and TFS) or an angled screw access channel (CFA and TFA) titanium-base abutment (n = 11). CFA and TFA received screw-retained crowns, whereas CFS and TFS received hybrid zirconia abutments and cement-retained crowns. The initial torque value (ITV) of each complex (ITVI) and removal torque value (RTV) after 24 h (RTVI) were measured. Screws were replaced with new ones, ITVs were recorded again (ITVF), and crowns were cyclically loaded (2.4 million cycles, 98 N) to measure RTVs again (RTVF). Percentage torque loss was calculated. Data were analyzed (a = 0.05).ResultsITVs were similar among groups (p = .089). CF led to higher RTVs (p = .002), while CFS had higher RTVI than CFA (p = .023). After 24 h, CFS had lower percentage torque loss than TF, while CFA had lower percentage torque loss than TFA (p = .011). After cyclic loading, CF led to lower percentage torque (p < .001).ConclusionThe implant-abutment connection affected the removal torque values. However, no screw loosening occurred during cyclic loading, which indicated a stable connection for all groups. Screw access channel angle did not affect screw stability after cyclic loading.
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    Effect of polishing and denture cleansers on the surface roughness of new-generation denture base materials and their color change after cleansing
    (Wiley, 2023) Cakmak, Guelce; Hess, Julia Anouk; Donmez, Mustafa Borga; Yilmaz, Deniz; Alhotan, Abdulaziz; Schimmel, Martin; Peutzfeldt, Anne
    Purpose: To evaluate the effect of polishing and denture cleansers on the surface roughness (Ra) of new-generation denture basematerials that are additively, subtractively, and conventionally fabricated, while also assessing their color change after cleansing. Material and Methods: One hundred and fifty disk-shaped specimens (O10 x 2 mm) were prepared from five denture base materials (one subtractively manufactured nanographene-reinforced prepolymerized polymethylmethacrylate (PMMA) (SM-GC), one subtractively manufactured prepolymerized PMMA (SM-PM), two additively manufactured denture base resins (AM-DT and AM-ND), and one heat-polymerized PMMA (CV) (n = 30). The R-a of the specimens was measured before and after conventional laboratory polishing, while color coordinates were measured after polishing. Specimens were then divided into three subgroups based on the denture cleanser: distilled water, 1% sodium hypochlorite (NaOCl), and effervescent tablet (n = 10). The R-a and color coordinates were remeasured after nine cleansing cycles over a period of 20 days. The CIEDE2000 formula was used to calculate the color differences (Delta E-00). Two-way analysis of variance (ANOVA) was used to analyze the R-a values before (n = 30) and after (n = 10) cleansing, while repeated measures ANOVA was used to analyze the R-a of material-time point pairs within each denture cleanser (n = 10). Delta E-00 data after denture cleansing was also analyzed by using two-way ANOVA (n = 10) (a = 0.05). Results: Before polishing, Ra varied significantly among the materials. SM-GC and SM-PM had the lowest and AM-ND the highest Ra values (P < 0.001). Polishing significantly reduced R-a of all materials (P < 0.001), and after polishing, Ra differences among materials were nonsignificant (P >= 0.072). Regardless of the denture cleanser, the R-a of AM-DT, AM-ND, and CV was the highest before polishing when different time points were considered (P < 0.001). After cleansing, AM-ND had the highest R-a of all the materials, regardless of the cleanser (P <= 0.017). AM-DT had higher R-a than SM-PM when distilled water (P = 0.040) and higher R-a than SM-GC, SM-PM, and CV when NaOCl was used (P < 0.001). The type of cleanser significantly influenced the R-a of AM-DT, AM-ND, and CV. For AM-DT, NaOCl led to the highest R-a and the tablet led to the lowest R-a (P <= 0.042), while for AM-ND, distilled water led to the lowest R-a (P <= 0.024). For CV, the tablet led to lower R-a than distilled water (P = 0.009). Color change varied among the materials. When distilled water was used, SM-GC had higher Delta E-00 than SM-PM and AM-DT (P <= 0.034). When NaOCl was used, AM-ND had higher Delta E-00 than SM-GC, SM-PM, and AM-DT, while CV and SM-GC had higher Delta E-00 than SM-PM and AM-DT (P = 0.039). Finally, when the tablet was used, AM-ND and CV had the highest Delta E-00, while AM-DT had lower Delta E-00 than SM-GC (P = 0.015). Conclusions: The tested materials had unacceptable surface roughness (>0.2 mu m) before polishing. Roughness decreased significantly after polishing (<0.2 mu m). Denture cleansers did not significantly affect the surface roughness of the materials, and roughness remained clinically acceptable after cleansing (<0.2 mu m). Considering previously reported color thresholds, AM-ND and CV had unacceptable color change regardless of the denture cleanser, and the effervescent tablet led to perceptible, but acceptable color change for SM-GC, SM-PM, and AM-DT.
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    Influence of implant scan body design (height, diameter, geometry, material, and retention system) on intraoral scanning accuracy: A systematic review
    (Wiley, 2023) Gomez-Polo, Miguel; Donmez, Mustafa Borga; Cakmak, Guelce; Yilmaz, Burak; Revilla-Leon, Marta
    PurposeTo evaluate the influence of implant scan body (ISB) design (height, diameter, geometry, material, and retention system) on the accuracy of digital implant scans.Material and MethodsA literature search was completed in five databases: PubMed/Medline, Scopus, Embase, World of Science, and Cochrane. A manual search was also conducted. Studies reporting the evaluation of ISB design on the accuracy of digital scans obtained by using IOSs were included. Two investigators evaluated the studies independently by applying the Joanna Briggs Institute critical appraisal. A third examiner was consulted to resolve any lack of consensus. Articles were classified based on the ISB features of height, geometry, material, and retention system.ResultsTwenty articles were included. Among the reviewed studies, 11 investigations analyzed the influence of different ISB geometries, 1 study assessed the impact of ISB diameter, 4 studies investigated the effect of ISB splinting, 2 articles evaluated ISB height, and 2 studies focused on the effect of ISB material on scan accuracy. In addition, 8 studies involved ISBs fabricated with different materials (1- and 2-piece polyetheretherketone and 1-piece titanium ISBs), and all of the reviewed articles tested screw-retained ISBs, except for 3 in vitro studies.ConclusionsThe findings did not enable concrete conclusions regarding the optimal ISB design, whether there is a relationship between IOS technology and a specific ISB design, or the clinical condition that maximizes intraoral scanning accuracy. Research efforts are needed to identify the optimal ISB design and its possible relationship with the IOS selected for acquiring intraoral digital implant scans.
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    Influence of intraoral scanner and finish line location on the fabrication trueness and margin quality of additively manufactured laminate veneers fabricated with a completely digital workflow
    (Mosby-Elsevier, 2024) Cakmak, Guelce; Chebaro, Jad; Donmez, Mustafa Borga; Yilmaz, Deniz; Yoon, Hyung-In; Kahveci, Cigdem; Schimmel, Martin
    Statement of problem. Knowledge of the fabrication trueness and margin quality of additively manufactured (AM) laminate veneers (LVs) when different intraoral scanners (IOSs) and finish line locations are used is limited. Purpose. The purpose of this in vitro study was to evaluate the fabrication trueness and margin quality of AM LVs with different finish line locations digitized by using different IOSs. Material and methods. An LV preparation with a subgingival (sub), equigingival (equi), or supragingival (supra) finish line was performed on 3 identical maxillary right central incisor typodont teeth. Each preparation was digitized by using 2 IOSs, (CEREC Primescan [PS] and TRIOS 3 [TS]), and a reference LV for each finish line-IOS pair (n=6) was designed. A total of 90 LVs were fabricated by using these files and urethane acrylate-based definitive resin (Tera Harz TC-80DP) (n=15). Each LV was then digitized by using PS to evaluate fabrication trueness (overall, external, intaglio, and marginal surfaces). Each LV was also qualitatively evaluated under a stereomicroscope (x60), and the cervical and incisal margin quality was graded. Fabrication trueness and cervical margin quality were evaluated by using 2 -way analysis of variance, while Kruskal-Wallis and Mann Whitney -U tests were used to evaluate incisal margin quality (alpha=.05). Results. The interaction between the IOS type and the finish line location affected measured deviations at each surface (P <=.020). PS -sub and TS -supra had higher overall trueness than their counterparts. and the subgingival finish line resulted in the lowest trueness (P <=.005). PS and the subgingival finish line led to the lowest trueness of the external surface (P <=.001). TS -sub had the lowest intaglio surface trueness among the TS subgroups, and PS -sub had higher trueness than TS -sub (P<.001). PS -sub and PS -supra had higher marginal surface trueness than their TS counterparts (P<.001). TS resulted in higher cervical margin quality (P=.001). Conclusions. Regardless of the IOS tested, subgingival finish lines resulted in the lowest trueness. The effect of IOS on the measured deviations varied according to the surface evaluated and finish line location. The cervical margin quality of AM LVs was higher when TS was used. (J Prosthet Dent 2024;131:313.e1 -e9)
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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.