EditorialDOI: 10.3290/j.ijcd.b4440063, PubMed ID (PMID): 37751297Pages 195-196, Language: English, GermanBeuer, Florian
ScienceDOI: 10.3290/j.ijcd.b3774253, PubMed ID (PMID): 36625373Pages 201-210, Language: English, GermanNguyen, Nhat Dinh-Minh / Tran, Nguyen Chi / Tran, Trang Thi-Ngoc / Huynh, Nam Cong-Nhat / Nguyen, Khoa Dang / Hoang, Hung Trong / Wang, Ding-Han / Hsu, Ming-Lun
Aim: The accuracy of 3D images produced by an intraoral scanner (IOS) is affected by the optical characteristics of restorative materials such as metal, ceramic, and composite resin. The present in vitro study aimed to investigate the impact of core buildup composite resin translucency on IOS accuracy.
Materials and methods: A core buildup procedure was performed on a proprietary 3D-printed model using injectable composite resins in four groups with different levels of translucency (highest to lowest: AE, A3, AO3, and EX). Ten experimental scans per group were performed using a Medit i700 IOS on a phantom head-mounted model. Reference scans were obtained using an industrial scanner (Solutionix C500). Values of accuracy (trueness and precision) for the respective groups were evaluated using mean deviation values following 3D superimposition.
Results: Composite resin translucency caused the scale reduction of the optical impressions. Values of trueness showed the highest scale reduction in AE, significantly, followed by A3, AO3, and EX. Considering 50 μm as the cut-off value of deviations for clinical acceptability, the analysis showed most deviations in AE and A3. Similar results were found with precision, where AE showed the highest deviation value statistically, followed by A3, AO3, and EX.
Conclusions: Composite resin translucency affects the accuracy of optical impressions, causing a fitting error of CAD/CAM prostheses. The more translucent the composite resin, the less accurate the optical impression. This suggests the need for proper compensation during prosthesis designing for an optimal clinical result. In addition, practitioners should indicate in the digital workflow the proper restorative materials regarding not only the mechanical properties and esthetics, but also the optical characteristics.
Keywords: accuracy, trueness, precision, composite resin, digital dentistry, intraoral scanner, CAD/CAM
ScienceDOI: 10.3290/j.ijcd.b3774277, PubMed ID (PMID): 36625371Pages 211-216, Language: English, GermanBiadsee, Ameer / Dolev, Eran / Perlis, Vladimer / Rosner, Ofir / Masarwa, Shchada / Ormianer, Zeev
Aim: To evaluate CAD/CAM milling vibrations related to zirconia disk design, framework, and location of digital crown nesting during zirconia soft milling.
Materials and methods: In the present in vitro study, 25 round zirconia disks of 98 mm (R group) and 15 D-shaped zirconia disks of 71 mm (D group) were placed in a 5-axis CAD/CAM milling unit. The R group had 3 crown milling sites (n = 75) and the D group had 2 crown milling sites (n = 30). In the R group, site A was located 57 mm, site B was 92 mm, and site C was 123 mm from the machine holder attachment. In the D group, site A was 57 mm and site C was 123 mm from the machine holder attachment. A vibration meter (VB-8200; Lutron) was connected to the disk holder, and data (mm/second) were collected during the milling process at the different nesting locations. One-way ANOVA with post-hoc tests and Bonferroni correction for multiple tests were used to compare the groups (α = 0.05).
Results: In the R group, site C exhibited the highest mean vibration values compared with site A (P = 0.001). The first and second cutting tools (2.5 and 1 mm) exhibited statistically significant differences between the D and R groups at milling sites A and C (P < 0.001 and P = 0.003, respectively).
Conclusions: Milling vibration increased as the distance between the machine holder arm and a digitally nested site increased. Round zirconia disks induced higher vibration values compared with D-shaped disks.
Keywords: CAD/CAM, milling vibration, digital nesting, zirconia
ScienceDOI: 10.3290/j.ijcd.b3774115, PubMed ID (PMID): 36625374Pages 217-226, Language: English, GermanLe, Vinzenz / Keßler, Andreas / Folwaczny, Matthias
Ziel: Ziel dieser In-vitro-Studie war es, den Einfluss unterschiedlicher Drucktechnologien auf die Genauigkeit von Implantatbohrschablonen für eine Freiendsituation zu evaluieren. Verglichen wurden verschiedene 3-D-Drucker (ein SLA- und zwei DLP-Drucker) und eine Fräsmaschine als Kontrollgruppe.
Material und Methode: Die Bohrschablonen wurden mit drei verschiedenen 3-D-Druckern hergestellt, einem SLA (Form 2, Formlabs) und zwei DLP-Druckern (D20II, Rapidshape; Solflex 350, W2P Engineering). Als Kontrolle dienten chirurgische Schablonen, die im subtraktiven Verfahren hergestellt wurden (MCX5, Dentsply-Sirona). Insgesamt wurden 48 Schablonen hergestellt und auf ihre Genauigkeit geprüft. Die Bohrschablonen wurden für die Insertion von Implantaten in Regio 37 verwendet. Die postoperative Implantatposition wurde anschließend gescannt und zum metrischen Vergleich mit der präoperativ geplanten Implantatposition digital überlagert.
Ergebnisse: Es wurden signifikante Unterschiede in den Implantatpositionen zwischen den SLA- und den DLP-gedruckten Schienen festgestellt. Dabei zeigte sich, dass die SLA-Schablonen im Vergleich zu den DLP-Schablonen eine signifikant geringere Genauigkeit bei den Parametern mittlere krestale Abweichung (p = 0,032) und der Winkelabweichung (p = 0,049) aufwies. Die DLP-gedruckten Schienen zeigten vergleichbare Werte wie die gefräste Kontrollgruppe. Die Ergebnisse lagen in einem akzeptablen klinischen Bereich.
Schlussfolgerung: Die DLP-Technologie scheint der konventionellen SLA-Technologie in Bezug auf die Genauigkeit von 3-D-gedruckten Bohrschablonen bei der Insertion von Implantaten in Freiendsituationen überlegen zu sein.
Keywords: geführte Chirurgie, Genauigkeit, 3-D-Druck, Fräsen, Dentalmaterialien, Freiendsituation, orale Implantologie
ScienceDOI: 10.3290/j.ijcd.b3774269, PubMed ID (PMID): 36625372Pages 227-236, Language: English, GermanSeckin, Özge / Akin, Ceyda / Özcan, Mutlu
Aim: The aim of the present study was to compare the load bearing capacity of monolithic or bilayered single crowns with zirconia or polyetherketoneketone frameworks designed and fabricated using CAD/CAM systems.
Materials and methods: Cr-Co–based metal dies (n = 60) were duplicated from an extracted and prepared premolar and then restored with different CAD/CAM materials. The specimens were divided into five groups (n = 12) according to the type of materials: group S: monolithic zirconia-reinforced lithium disilicate; group ZI: bilayered zirconia framework with lithium disilicate; group ZE: bilayered zirconia framework with resin-infiltrated hybrid ceramic; group PI: bilayered polyetherketoneketone (PEKK) framework with lithium disilicate; group PE: bilayered PEKK framework with resin-infiltrated hybrid ceramic. The crown specimens were cemented on Cr-Co metal dies with a resin cement (Multilink N). The specimens were subjected to cyclic mechanical loading followed by load bearing testing. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests (α = 0.05).
Results: The monolithic crowns in group S (1930 ± 452.18 N) presented significantly higher load bearing capacity than those of the other groups (P < 0.05). This was followed by group ZI (1165.41 ± 264.04 N). The remaining groups demonstrated comparable results. Failure types were more frequent in all zirconia specimens that included veneering ceramic.
Conclusions: Monolithic zirconia-reinforced lithium disilicate CAD/CAM ceramics showed superior load bearing capacity compared with all other bilayered counterparts. All CAD/CAM materials tested remarkably exceeded the average occlusal force in the posterior region.
Keywords: bilayered all-ceramics, CAD/CAM, dental materials, load bearing capacity, monolithic, PEKK, zirconia, prosthodontics
ScienceDOI: 10.3290/j.ijcd.b3781703, PubMed ID (PMID): 36632986Pages 237-245, Language: English, GermanGil, Alfonso / Eliades, George / Özcan, Mutlu / Jung, Ronald E. / Hämmerle, Christoph H. F. / Ioannidis, Alexis
Aim: To evaluate the fracture load and type of failure of two different monolithic restorative materials bonded to standardized titanium bases and fabricated by two different procedures regarding the bonding interface.
Materials and methods: All screw-retained implant crown specimens (n = 40), subjected to fatigue by thermomechanical loading, differed in the restorative material (lithium disilicate [LDS] or polymer-infiltrated ceramic network [PICN], referred to as ‘hybrid ceramic’ [HYC]) and the interface type between the restorative material and the titanium base abutment (prefabricated ex-factory or produced during a CAM-milling procedure). This resulted in the following groups (n = 10/group): 1) LDS-M: lithium disilicate crown with a CAM-milled interface; 2) LDS-P: lithium disilicate crown with a prefabricated interface; 3) HYC-M: PICN crown with a CAM-milled interface; and 4) HYC-P: PICN crown with a prefabricated interface. Aged specimens underwent static fracture load testing. The load (N) at which the initial crack occurred was denoted as Finitial, and the maximal load (N) at which the restorations fractured as Fmax. All specimens were examined under a stereomicroscope to determine the failure mode.
Results: The median Finitial values were 180 N for LDS-M, 343 N for LDS-P, 340 N for HYC-M, and 190 N for HYC-P. The median Fmax values were 1822 N for LDS-M, 2039 N for LDS-P, 1454 N for HYC-M, and 1581 N for HYC-P. The intergroup differences were significant for Finitial (KW: P = 0.0042) and for Fmax (KW: P = 0.0010). The failure types also showed differences between the restorative groups.
Conclusions: The choice of restorative material had a stronger influence on the fracture load than the abutment interface workflow. Lithium disilicate showed the highest load for initial crack appearance (Finitial) and for complete fracture of the restoration (Fmax).
Keywords: lithium disilicate, dental materials, polymer-infiltrated ceramic network, thermomechanical aging, fracture load, failure mode, prosthetic dentistry, restorative material, abutment interface
ScienceDOI: 10.3290/j.ijcd.b3796761, PubMed ID (PMID): 36632987Pages 247-255, Language: English, GermanPrause, Elisabeth / Hey, Jeremias / Sterzenbach, Guido / Beuer, Florian / Adali, Ufuk
A 10-year follow-up studyAim: The aim of the present study was to evaluate the long-term clinical survival and success rate of veneered zirconia crowns with a modified anatomical framework design after 10 years in function.
Materials and methods: In total, 36 zirconia crowns were fabricated for 28 patients. An anatomically modified framework design was developed. Crowns were inserted between 2008 and 2009. A follow-up of 19 patients with 28 crowns was conducted in 2020 to document mechanical and biologic parameters. Additionally, a modified version of the pink esthetic score (PES) was documented. Patient satisfaction was assessed using United States Public Health Service (USPHS) criteria. The success and survival rates were calculated using the Kaplan-Meier analysis.
Results: After more than 10 years of clinical service, the survival rate of the zirconia crowns was 92.9%. Biologic complications occurred in 12% of the examined crowns, whereas technical complications occurred in 54%. Mostly, chippings (50%) and insufficient marginal gaps (50%) were observed. Most crowns were positively evaluated for more than one technical complication. Periodontal conditions with probing depths of up to 3 mm were comparable with measured values before crown delivery (73% to 75%). Most of the crowns had modified PES values of 10 or higher. Patient satisfaction was high.
Conclusions: The modified framework design led to a high survival rate of the crowns but a relatively low success rate. High patient satisfaction and inconspicuous periodontal conditions were demonstrated. Biologic complications occurred far less frequently than technical complications.
Keywords: all-ceramic crown, framework design, clinical study, chipping, complications
ApplicationDOI: 10.3290/j.ijcd.b3836703, PubMed ID (PMID): 36695627Pages 257-264, Language: English, GermanYazigi, Christine / Busch, Reinhard / Kern, Matthias
Aim: The aim of the present article is to describe a new method to reduce the undesirable loss of material thickness that results from overmilling due to the tool diameter compensation correction of common CAD/CAM software.
Materials and methods: Today’s CAD/CAM software (eg, 3Shape or Exocad) specifies the same tool diameter compensation for different ceramics. In the case of zirconia ceramics milled in the raw state, this leads to excessive milling of the inner surfaces of crowns, which results in unnecessarily large cementation gaps and a restoration that is thinned out from the inside. By manually reducing the preset correction in the digital design process by the volumetric sintering shrinkage factor specified by the manufacturer, excessive thinning of the zirconia can be avoided.
Results: The inner geometry of the restorations changes only slightly after manually reducing the preset tool diameter compensation correction. Consequently, a design of the restoration with the required minimum interocclusal thickness yet with accurate passive seating and marginal fit is possible without any further interventions.
Conclusions: Understanding the specifics of the subtractive fabrication process as well as the properties of the restorative materials is a key factor in achieving optimal clinical outcomes with all-ceramic restorations fabricated with CAD/CAM technology. The use of monolithic zirconia combined with a calculated reduction in the preset tool diameter compensation correction might be beneficial in cases with thin or uneven geometry.
Keywords: all-ceramic restorations, CAD/CAM, tool diameter compensation, monolithic zirconia, minimum thickness, subtractive manufacturing