Effect of decontamination and cleaning on the shear bond strength of high translucency zirconia

(1) Background: This study evaluated the bonding performance of high translucency zirconia after diverse surficial decontamination and cleaning procedures. (2) Methods: High translucency zirconia (LavaTM Esthetic) specimens (2.0 mm × 20 mm × 10 mm) were exposed to different surface treatments prior to bonding to CoCr cylinders (d = 5 mm, height = 3 mm). All surfaces were sandblasted (40 µm aluminum oxide, 2 bar) and treated with alcohol (al), saliva (s), saliva + water (sw), or saliva + NaOCl + water (sn) before bonding was performed with the following adhesive luting systems: RelyXTM Unicem 2 (RX), ScotchbondTM Universal (SBU) + RelyXTM Ultimate (RU) or Monobond Plus (MP) + Multilink® Automix (ML). After 24 h, thermocycling (TC:12,000 × 5 °C/55 °C) and 90 days of storage at 37 °C in distilled water, the shear bond strength (SBS) was evaluated according to ISO/TS 11,405:2015. Failure modes along bonding areas were characterized. Means and standard deviations (n = 10 per group) were determined and statistically analyzed with one-way ANOVA/Bonferroni (α = 0.05). (3) Results: The SBS after 24 h varied between 3.5 (sRX) and 69.4 MPa (snMP + ML). Values from 0 (sRX) to 70.3 MPa (swRX) were found after TC. Data after 90 days of storage showed the lowest values for sRX (0 MPa) and the highest values for alSBU + RU (75.5 MPa). Adhesive failure was noted at all aging conditions. (4) Conclusions: SBU + RU or RX and MP + ML including saliva decontamination of the ceramic surface with water or NaOCl + water allow efficient bonding to LavaTM Esthetic

Surface properties of monolithic zirconia after dental adjustment treats and in vitro wear simulation

Objectives To investigate the surface properties (roughness, composition, phase transformation) of monolithic zirconia specimens after dental adjustment procedures (grinding, polishing) and wear simulation. Methods Zirconia specimens (Cercon base, Cercon ht, DeguDent, G; n = 10/material) were successively sintered, ground, and polished with an intraoral polishing kit in a three-step procedure. Sintered zirconia specimens with high surface roughness served as a reference. For each treatment step, wear simulations with steatite plates (d = 10 mm) as antagonists were conducted as well as surface roughness tests (Ra), EDX analysis, and X-ray diffraction (XRD) measurements. SEM pictures were taken, and data were statistically analyzed (one-way ANOVA, post hoc Bonferroni, α = 0.05). Results Grinding significantly (p = 0.000) increased the roughness of sintered zirconia up to values of 1.36 ± 0.11 μm (Ra). Polishing significantly (p = 0.000) reduced Ra. The lowest roughness value after the final polishing step was 0.20 ± 0.03 μm. Wear testing resulted in a further slight decrease of Ra. After the grinding procedure, SEM pictures showed deep grooves that were progressively smoothed by polishing. The EDX spectra showed that magnesium was transferred from steatite antagonists to zirconia by wear. In the XRD-patterns, monoclinic (m) peaks were observed after grinding and polishing. The maximum intensity ratio between the m (1 1 −1) peak and the tetragonal t (1 1 1) peak decreased after the completion of all polishing steps. Wear did not induce phase transformation. Conclusions Adequate polishing reduced the roughness of ground zirconia. Wear had little influence on roughness and no influence on phase transformation. Clinical significance Careful polishing is recommended to keep surface roughness and phase transformation low

Patterns of urinary cortisol levels during ontogeny appear population specific rather than species specific in wild chimpanzees and bonobos

Compared with most mammals, postnatal development in great apes is protracted, presenting both an extended period of phenotypic plasticity to environmental conditions and the potential for sustained mother-offspring and/or sibling conflict over resources. Comparisons of cortisol levels during ontogeny can reveal physiological plasticity to species or population specific socioecological factors and in turn how these factors might ameliorate or exaggerate mother-offspring and sibling conflict. Here, we examine developmental patterns of cortisol levels in two wild chimpanzee populations (Budongo and Taï), with two and three communities each, and one wild bonobo population (LuiKotale), with two communities. Both species have similar juvenile life histories. Nonetheless, we predicted that key differences in socioecological factors, such as feeding competition, would lead to interspecific variation in mother-offspring and sibling conflict and thus variation in ontogenetic cortisol patterns. We measured urinary cortisol levels in 1394 samples collected from 37 bonobos and 100 chimpanzees aged up to 12 years. The significant differences in age-related variation in cortisol levels appeared population specific rather than species specific. Both bonobos and Taï chimpanzees had comparatively stable and gradually increasing cortisol levels throughout development; Budongo chimpanzees experienced declining cortisol levels before increases in later ontogeny. These age-related population differences in cortisol patterns were not explained by mother-offspring or sibling conflict specifically; instead, the comparatively stable cortisol patterns of bonobos and Taï chimpanzees likely reflect a consistency in experience of competition and the social environment compared with Budongo chimpanzees, where mothers may adopt more variable strategies related to infanticide risk and resource availability. The clear population-level differences within chimpanzees highlight potential intraspecific flexibility in developmental processes in apes, suggesting the flexibility and diversity in rearing strategies seen in humans may have a deep evolutionary history.Publisher PDFPeer reviewe

In-vitro-Untersuchungen zum Zwei-Körper-Verschleiß von Gerüst- und Verblendkeramiken gegenüber Steatit und humanem Zahnschmelz

Ziel dieser In-vitro-Studie war es, den Zwei-Körper-Verschleiß von verschiedenen Gerüst- und Verblendkeramiken gegenüber Steatit und humanem Zahnschmelz unter besonderer Berücksichtigung der Oberflächenbehandlung und Oberflächenrauigkeit zu untersuchen. Von 13 Silikatkeramiken (Feldspatkeramiken, Fluorapatit- und Lithiumdisilikat-Glaskeramiken), 11 Oxidkeramiken (Zirkoniumdioxid- und glasinfiltrierte Aluminiumoxidkeramiken), 2 Nichtedelmetall-Legierungen (NEM) und Zahnschmelz als Referenzmaterial wurden Prüfkörper gefertigt. Die Glaskeramiken wurden glasiert und anschließend poliert, wohingegen die Oxidkeramiken nur poliert wurden. Eine Zirkoniumdioxidkeramik wurde mit einer Glasurschicht getestet, die nach einer Oberflächenvorbehandlung in Form von Politur bzw. Sandstrahlung aufgetragen wurde. NEM-Legierungen wurden entweder poliert oder sandgestrahlt. Die so vorbereiteten 30 Serien (16 Prüfkörper je Serie) wurden einer Pin-on-block-Verschleißsimulation im Regensburger Kausimulator unter thermomechanischer Wechselbelastung für 120000 Kauzyklen (1,6 Hz; 50N; Lateralbewegung: 1 mm; Mundöffnung: 2 mm) und 600 Thermozyklen (5°C/55°C; 2min/Zyklus) unterzogen. Als Antagonisten für jeweils 8 Prüfkörper pro Serie fungierten Steatitkugeln bzw. humane Zahnhöcker. Vor der Verschleißprüfung wurde die Oberflächenrauigkeit (Ra, Rz) mit einem Oberflächenprofilometer (Perthometer) erfasst. Mittels dreidimensionaler optischer Oberflächenprofilometrie (Lasercan 3D) und Lichtmikroskopie wurden Verschleißtiefe sowie Verschleißvolumen der Prüfkörper und die Verschleißfläche der Steatitantagonisten berechnet. Die statistische Datenanalyse erfolgte mithilfe One-way-ANOVA und dem post-hoc Bonferroni-Test auf einem Signifikanzniveau von 5%. Die Verschleißphänomene auf den Prüfkörpern und ihren Antagonisten wurden im Rasterelektronenmikroskop beurteilt. Silikatkeramiken wiesen signifikant größere Verschleißraten als polierte Oxidkeramiken und NEM-Legierungen auf, bei denen kein Materialverlust gemessen werden konnte. In der Gruppe der Glaskeramiken konnten zum größten Teil keine signifikanten Unterschiede zwischen Feldspatkeramiken, Fluorapatit- und Lithiumdisilikat-Glaskeramiken beobachtet werden. Ihre Verschleißraten waren mit denen der Schmelzreferenzserie vergleichbar oder sogar niedriger. Der Verschleiß der glasierten Zirkoniumdioxidkeramik beschränkte sich auf die Glasurschicht. Höhere Verschleißraten der Probekörper spiegelten sich in größeren Verschleißflächen der Antagonisten wider. Der antagonistische Verschleiß gegenüber Oxidkeramiken war niedriger als gegenüber Silikatkeramiken. Die initialen Oberflächenrauigkeiten unterschiedlicher Keramiktypen bewegten sich nach der Politur durchweg in einem Wertebereich, der mit einem klinischen Polierset erreicht werden kann, wobei keine signifikanten Unterschiede zur Rauigkeit der Glasuroberfläche bestanden. Oberflächenzerrüttung und Oberflächenschäden (Riefen, Risse, Ausbrüche) durch den Verschleiß waren bei den Silikatkeramiken und ihren Antagonisten stärker ausgeprägt als bei den Oxidkeramiken und NEM-Legierungen. Das Auftreten von konusförmigen Rissen wurde ausschließlich bei Silikatkeramiken beobachtet. Die Einschränkungen einer In-vitro-Verschleißuntersuchung bedenkend, kann zusammenfassend festgestellt werden, dass der Verschleiß der Probekörper und ihrer Antagonisten stark materialabhängig war. Verblendfreie Oxidkeramiken scheinen grundsätzlich für den klinischen Einsatz geeignet, da sie sowohl selbst sehr verschleißresistent sind, als sich auch verschleißfreundlich gegenüber den Antagonisten verhalten

In Vitro Fatigue and Fracture Testing of Implant-Supported Anterior Ceramic Crowns

Purpose: To evaluate the fatigue and fracture resistance of anterior implant-supported and tooth-supported crowns made of different monolithic ceramics. Materials and Methods: Anterior crowns were fabricated of lithium disilicate or one of two zirconia ceramics and were tested as tooth-supported (reference) or as implant-supported crowns with chairside or labside (screw channel) procedures. After thermocycling and mechanical loading (TCML), crowns were loaded to fracture. Results: ASS crowns survived TCML. Implant-supported crowns (chairside and labside) showed higher fracture values than tooth-supported crowns. Fracture resistance was comparable or higher for zirconia than for lithium disilicate crowns. Conclusion: Implant-supported ceramic crowns may withstand clinical anterior loading forces

In Vitro Fatigue and Fracture Testing of Implant-Supported Anterior Ceramic Crowns

Purpose: To evaluate the fatigue and fracture resistance of anterior implant-supported and tooth-supported crowns made of different monolithic ceramics. Materials and Methods: Anterior crowns were fabricated of lithium disilicate or one of two zirconia ceramics and were tested as tooth-supported (reference) or as implant-supported crowns with chairside or labside (screw channel) procedures. After thermocycling and mechanical loading (TCML), crowns were loaded to fracture. Results: ASS crowns survived TCML. Implant-supported crowns (chairside and labside) showed higher fracture values than tooth-supported crowns. Fracture resistance was comparable or higher for zirconia than for lithium disilicate crowns. Conclusion: Implant-supported ceramic crowns may withstand clinical anterior loading forces

Fatigue and wear behaviour of zirconia materials

Objectives: Comparison of in-vitro fatigue and wear performance of 3Y-, 4Y-, 5Y-TZP and lithiumdisilicate ceramic, multilayer/monolayer 4Y-TZP and variation of wall thickness at 5Y-TZP. Method and materials: Crowns (n = 96; 6 groups a 16) were made of 3Y-TZP-LA, 4Y-TZP (multilayer and monolayer), 5Y-TZP (0,5mm/1 mm wall thickness) and lithiumdisilicate. 8 per group were stored in water (24hrs), 8 underwent TCML (1.200.000 x 50N; 2x3000x5 degrees/55 degrees C; H2O, 2min cycle). Fracture force was determined by static loading (v = 1 mm/min, steel sphere with tin foil, diameter = 12 mm). Pin-on-block wear test was performed (steatite antagonist d = 3 mm; 50N, 120,000 cycles, 1.2Hz, lateral motion: 1 mm, antagonist lift: 1 mm, n = 8). Roughness, wear depth [pm] and antagonist wear were determined (3-D-laser-microscope, KJ3D, Keyence, J). Statistics: one-way-ANOVA; Bonferroni-post-hoc-test; alpha = 0.05. Results: Fracture forces varied between 1211N (5Y,TCML) and 3952N (4Y-Mult,TCML). Individual significant differences (p = 0.442) increase of fracture force. 4Y and 4Y-multilayer zirconia showed no significantly different (p >= 0.073) fracture forces. Zirconia mean wear (3Y:10.0 +/- 3.9 pm, 4Y:19.8 +/- 3.8 pm, 5Y:10.9 +/- 6.8 pm) was not significantly (p = 1.000) different. Lithiumdisilicate ceramic (149.3 +/- 45.4 pm) and human enamel (434.2 +/- 131.3 pm) provided significantly (p <= 0.002) higher wear. Antagonistic wear against lithiumdisilicate (17.5 +/- 3.9%) and human enamel (6.7 +/- 3.0%) was significantly (p <= 0.007) lower than against zirconia (4Y:31.9 +/- 8.0% 5Y:27.6 +/- 5.8%). Conclusion: Fracture force of 5Y-TZP differs from 4- or 3-Y-TZP. Mechanical characteristics and dimensional requirement of 5Y-TZP are comparable to lithiumdisilicate. Monoor multilayer 4Y-TZP provided comparable fracture forces. Wear was comparable between zirconia systems and lower in comparison to lithiumdisilicate or enamel

Comparison of flowable bulk-fill and flowable resin-based composites: an in vitro analysis

Flowable bulk-fill resin bonded composites (RBCs) are supposed to show improved abrasion resistance and fracture toughness in comparison to flowable conventional RBCs. Specimens of eight flowable RBCs (5x flowable conventional, 3x flowable bulk-fill) were fabricated for testing relative fracture toughness (SENB), relative three-body wear, the Vickers hardness, glass transition Tg (differential scanning calorimetry; DSC) and filler mass fraction (thermal gravimetric analysis; TGA). A laboratory veneering composite was used as a reference. Fracture toughness and wear values were related to this reference. Scanning electron microscope images were evaluated for fraktographical and microstructural investigations. Statistical analyses were performed using one-way Anova, the Bonferroni post hoc test and the Pearson correlation test (alpha =0.05). Relative fracture toughness varied between 0.64 and 1.34 (1.00 = 1.69 MPamA1/2) and relative wear rates between 1.24 and 0.55 (1.00 = 134 mu m). The Vickers hardness ranged between 14.4 and 57.2 HV. TGA showed filler fractions between 55 and 77 wt.%. Tg values varied between -67.8 and -40.9 A degrees C. None of the tests identified clear differences between flowable bulk-fills or conventional flowable RBCs. The Pearson correlation coefficient (cc) showed significant correlations (cc > 0.583; p 0.702; p < 0.001). For all filler sizes breakdown was found, where clusters and pre-polymerized particles were partly disintegrated. Flowable bulk-fill RBCs showed no improved abrasion resistance and fracture toughness in comparison to flowable conventional RBCs. Differences in the properties were higher between the individual materials than between the material groups. Therefore the appropriate material selection may be essential for a clinical success

In-vitro performance of CAD/CAM crowns with insufficient preparation design

Purpose: To compare the debonding and fracture force of different CAD/CAM composite crowns with respect to the influence of water storage (Od vs. 90d/37 degrees C) and types of cementation (adhesive vs. self-adhesive). Methods: Extracted human molars were prepared with a worst-case preparation scenario providing a non retentive design (height similar to 4 mm; angle similar to 15 degrees) and reduced fitting (250 gm). After digitalization, 72 crowns (n = 8 per group; circular wall thickness 1.5 mm/occlusal thickness similar to 2.5 mm) were milled from the composites (CS, LU), one experimental composite (EX), a resin-infiltrated ceramic (VE), and a feldspar ceramic reference (VM). The crowns were adhesively bonded (Scotchbond Universal + Rely X Ultimate, 3M), and two groups (EX, VE) were additionally cemented with a self-adhesive cement (RelyX Unicem, 3M). After 90-d water storage, thermal cycling and mechanical loading (TCML) were performed. Restorations, which failed during storage or TCML, were analyzed using scanning electron microscopy, and surviving restorations were loaded to fracture. To evaluate storage effects, two materials (EX, LU) were investigated without water storage. Results: CS (7 x) and LU (2 x) exhibited debonding during 90-d storage. LU (5 x) debonded during TCML. Cement remained on the inner sides of the crowns in all cases. EX and VE survived storage and TCML without failure or debonding. Two specimens of VM exhibited cracks after TCML. Fracture forces varied between 720 N and 2155 N. Solely the results between VE and VM were not significantly different (p = 0.204). Debonding effects due to water storage were material dependent. Fracture forces in tendency (p > 0.117) were higher for self-adhesive cementation. Conclusions: Debonding and stability of CAD/CAM crowns were material dependent. Water storage affected debonding, and cementation marginally influenced performance and fracture force

Multilayer zirconia: Influence of positioning within blank and sintering conditions on the in vitro performance of 3-unit fixed partial dentures

Statement of problem. Multilayer zirconia blanks comprise material layers with different optical and mechanical properties. Whether positioning within the blank, as well as variation in the sintering procedure, will lead to restorations with different properties is unclear. Purpose. The purpose of this in vitro study was to test the influence of sintering procedures and positioning in a multilayer blank on the in vitro performance of 3-unit zirconia fixed partial dentures. Materials and methods. Human molars were embedded in acrylic resin and prepared for 3-unit fixed partial dentures. Anatomic contour prostheses were milled from zirconia blanks (ZirCAD Prime 16 mm) in 3 different positions: above (cusp-top at the top of the blank), central (center of the prosthesis in the center of the blank), and bottom (margins at the lower edge of the blank). Sintering time (2:26, 4:25, 9:50 hours:minutes) was varied for the central and bottom prostheses. All prostheses were glazed and adhesively bonded. Thermocycling and mechanical loading was performed at 2x3000x5 degrees C/55 degrees C in distilled water for 1.2x10(6) cycles at a 50-N load. Then, fracture force was determined with a universal testing device by using central loading, a empty set12-mm steel ball, a 1-mm tin foil, and a rate of 1 mm/min. Failure was defined as 10% force drop or acoustic signal (crack). Statistical analysis was performed with 1-way ANOVA and Bonferroni correction (alpha.=.05). Results. All fixed partial dentures survived thermocycling and mechanical loading. Fracture forces varied between 1002 +/- 446 N (above; 9:50 hours) and 1760 +/- 607 N (central; 9:50 hours). The 1-way ANOVA revealed no statistically significant differences (P=.059) among the groups. Individual significant differences (P=.048) were found between prostheses from positions above, 9:50 hours, and central, 9:50 hours. For normal and long sintering times, fracture forces were highest in the central position. Conclusions. The sintering process and positioning of restorations within a multilayer zirconia blank have little effect on the mechanical properties of the prostheses