Albert Trottmann

Impact of thermal misfit on shear strength of veneering ceramic/zirconia composites

OBJECTIVES Thermal misfit is discussed as one reason for chipping of veneered zirconia restorations. The aim of the investigation was to assess the effect of thermal misfit on the shear strength of zirconia/veneering ceramic composites. METHODS Shear strengths of 12 different veneering ceramic/zirconia composites were measured (n=10). The veneering ceramics were fired onto polished Y-TZP. In order to create a strong thermal mismatch, one of the veneering ceramics was intended for use on alumina and one for the metal-ceramic technique. The glass transition temperatures of the veneering ceramics and the coefficients of thermal expansion of all ceramics were measured (n=6). Statistical analysis was performed with one-way ANOVA and a post hoc Bonferroni test (p<0.05). RESULTS Shear strength ranged from 21.9+/-6.2 to 31.0+/-7.1 MPa. The ceramic for the metal-ceramic technique showed spontaneous debonding. The differences in the coefficients of thermal expansion of core and veneer (Delta alpha) were calculated. In addition the differences between glass transition temperatures of the veneering ceramics and room temperature (Delta T) as the effective temperature range for stress formation were calculated. Highest shear strength was observed when Delta alpha Delta T approximately 1000 x 10(-6). CONCLUSIONS Thermal expansion and glass transition temperature of the veneering ceramic have an impact on the shear strength of veneer/zirconia composites.

Two-body wear of monolithic, veneered and glazed zirconia and their corresponding enamel antagonists

OBJECTIVE This study tested whether the two-body wear of monolithic zirconia and their corresponding enamel antagonists was higher compared to monolithic alloy and veneered zirconia. MATERIALS AND METHODS Cylindrical specimens (N = 36, n = 6) were prepared out of (A) veneered zirconia (VZ), (B) glazed zirconia using a glaze ceramic (GZC), (C) glazed zirconia using a glaze spray (GZS), (D) manually polished monolithic zirconia (MAZ), (E) mechanically polished monolithic zirconia (MEZ) and (F) monolithic base alloy (control group, MA). Wear tests were performed in a chewing simulator (49 N, 1.7 Hz, 5°C/50°C) with enamel antagonists. The wear analysis was performed using a 3D profilometer before and after 120,000, 240,000, 640,000 and 1,200,000 masticatory cycles. SEM images were used for evaluating wear qualitatively. The longitudinal results were analysed using linear mixed models (α = 0.05). RESULTS Materials (p < 0.001) and number of masticatory cycles (p < 0.001) had a significant effect on the wear level. The least enamel antagonist wear was observed for MAZ and MEZ (27.3 ± 15.2, 28 ± 11.1 μm, respectively). GZC (118 ± 30.9 μm) showed the highest wear of enamel antagonists. The highest wear rate in the material was observed in GZS (91.3 ± 38.6 μm). While in the groups of MA, VZ, GZC and GZS 50% of the specimens developed cracks in enamel, it was 100% in MAZ and MEZ groups. CONCLUSION Polished monolithic zirconia showed lower wear rate on enamel antagonists as well as within the material itself but developed higher rates of enamel cracks.

Impact of thermal properties of veneering ceramics on the fracture load of layered Ce-TZP/A nanocomposite frameworks

OBJECTIVES The aim of this in vitro study was to assess the influence of thermal properties of veneering ceramics on the fracture load of layered ceria stabilized zirconia/alumina nanocomposite (Ce-TZP/A) single crowns. METHODS Ce-TZP/A single crown frameworks (nanoZr) were veneered with 5 different veneering ceramics for zirconia (Cerabien ZR, IPS e.max, Triceram, Vintage ZR, VM9). In addition, veneering ceramics for alumina (Allux) and for the metal-ceramic technique (Reflex) were included in order to cover a wide range of coefficients of thermal expansion. Fracture load of the crowns was assessed in a shear test (n=10). Glass transition temperatures (T(g)) of the ceramics as well as the coefficients of thermal expansion of the ceramics (alpha(veneer)) and Ce-TZP/A (alpha(core)) between 25 and 500 degrees C were determined (n=6). RESULTS Fracture load ranged from 574.0+/-97.1N (IPS e.max) to 1009.6+/-150.0N (VM9). Deltaalpha=alpha(core)-alpha(veneer) and DeltaT=T(g)-25 degrees C (DeltaT in K) were calculated. The fracture load was strongly correlated to Deltaalpha DeltaT with a maximum at Deltaalpha DeltaT approximately 580 x 10(-6). SIGNIFICANCE The overall fracture load of veneered Ce-TZP/A crowns is correlated to the thermal properties of the respective veneering ceramic.

Two-body wear rate of CAD/CAM resin blocks and their enamel antagonists.

STATEMENT OF PROBLEM Computer-aided design and computer-aided manufacturing (CAD/CAM) resins exhibit good mechanical properties and can be used as long-term restorations. The wear rate of such resins and their enamel antagonists is unknown. PURPOSE The purpose of this study was to test and compare the 2-body wear rate of CAD/CAM resin blocks. MATERIAL AND METHODS Wear specimens (N=42, n=6) were made from 5 CAD/CAM resins: ZENO PMMA (ZP), artBloc Temp (AT), Telio CAD (TC), Blanc High-class (HC), CAD-Temp (CT); 1 manually polymerized resin: Integral esthetic press (negative control group, IEP); and 1 glass-ceramic: VITA Mark II (positive control group, VM2). The specimens for the wear resistance were aged in a thermomechanical loading machine (49 N, 1.67 Hz, 5/50°C) with human enamel antagonists. The material loss of all specimens before, during, and after aging was evaluated with a 3DS profilometer. The measured material loss data of all tested groups were statistically evaluated with linear mixed model analysis (a=.05). RESULTS Manually polymerized resin showed significantly higher material wear (P<.001) than all other tested groups. Glass-ceramic showed significantly lower wear values (P<.001) than CAD/CAM resins ZP, AT, HC, CT, and IES. CAD/CAM resin TC was not significantly different from the positive control group. Glass-ceramic showed the highest enamel wear values (P<.001) of all tested resins. No differences were found in the enamel wear among all resins. The glass-ceramic group showed damage in the form of cracks on the worn enamel surface in 50% of specimens. CONCLUSIONS CAD/CAM resins showed lower wear rates than those conventionally polymerized. Only one CAD/CAM resin, TC, presented material wear values comparable with glass-ceramic. The tested glass-ceramic developed cracks in the enamel antagonist and showed the highest enamel wear values of all other tested groups.

Load-bearing capacity and failure types of anterior zirconia crowns veneered with overpressing and layering techniques.

OBJECTIVES The aim of this study was to test whether the load bearing capacity of anterior zirconia crowns veneered with overpressed or layered, is similar and to evaluate the failure types. METHODS Standardized zirconia frameworks were fabricated and randomly divided into 8 groups (N=120, n=15 per test group). Four groups were veneered with one of the layered veneering porcelains: Zirox, GC Initial ZR, VITA VM9 or IPS e.max Ceram and the other four groups were veneered with overpressed veneering porcelains: PressX Zr, GC Initial LF, VITA PM9 or IPS e.max ZirPress. The crowns were cemented on their corresponding CoCr abutment and the specimens were loaded at an angle of 45° in a Universal Testing Machine to determine the fracture load. Data were analyzed using one-way and two-way ANOVA, followed by a post hoc Scheffé test, t-test and Weibull analysis (alpha=0.05). RESULTS Within three manufacturers of veneering porcelain, fracture load values were not statistically significant between overpressed and layered porcelain systems. Within one manufacturer of veneering porcelain, the overpressed crowns (IPS e.max ZirPress: 1519 ± 334 N) demonstrated significantly higher (p<0.05) fracture load than that of the layered one (IPS e.max Ceram: 894 ± 160 N). Except with IPS e.max ZirPress, where exclusively only chipping of the veneering porcelain was observed, all other porcelain systems showed predominantly framework fractures together with fracture of the veneering porcelain. CONCLUSION Overpressed veneering porcelains for zirconia frameworks exhibited similar or better fracture load compared with layered ones.

Adhesion of veneering resins to polymethylmethacrylate-based CAD/CAM polymers after various surface conditioning methods

Abstract Objectives. The aims of this study were to test whether the bond strength of a hybrid composite and a PMMA-based veneer to CAD/CAM polymers would improve after pre-treatment and to evaluate the failure types after debonding. Materials and methods. Three types of PMMA-based (CAD-Temp, artBloc Temp and TelioCAD) CAD/CAM blocks were obtained (N = 360, n = 15 per test group). They were divided into four groups to be conditioned with the following methods: (a) no-treatment, (b) air-abrasion (50 μm Al2O3), (c) air-abrasion (50 μm Al2O3) + MPS-Silane (Monobond S) + Adhesive resin (StickResin) (for Gradia)/MMA (for Integral Esthetic Press) application, (d) Silica coating and silanization (CoJet-System). The conditioned surfaces were veneered with a hybrid composite (Gradia) or a PMMA-based resin (Integral esthetic press). After water storage (1 week, 37°C), the bond strength was measured. Data were analyzed using 3-way ANOVA and post-hoc Scheffé test (α = 0.05). Results. Surface-conditioning method, veneer type and CAD/CAM polymers significantly affected the results. Hybrid composite did not bond to non-conditioned CAD/CAM polymers. Regardless of the conditioning method, PMMA-based resin showed significantly higher bond strength to all CAD/CAM polymers compared to hybrid composite. Air-abrasion increased the bond strength in all tested groups. Additional silane application after air-abrasion did not significantly increase the bond strength of hybrid composite. While exclusively adhesive failures were observed between the hybrid composite and the CAD/CAM polymers, PMMA veneer demonstrated cohesive failures in the CAD/CAM polymers. Conclusion. CAD/CAM polymers could be veneered with only a PMMA-based veneer with and without air-abrasion.

Impact of air‐abrasion on fracture load and failure type of veneered anterior Y‐TZP crowns before and after chewing simulation

The purpose of this study was to determine the fracture load and failure types of veneered zirconia crowns that were air-abraded on either the veneering or cementation surface. Fracture loads were determined before and after chewing simulation. Standardized Y-TZP frameworks (n = 360) for canines were fabricated and divided into one control group (n = 72) and 12 test groups (n = 24). The test groups were air-abraded using alumina powder (10 s, 2 bar, distance: 10 mm) with particle size of 50 μm resp. 110 μm and veneered with one of the veneering ceramics: Triceram, Zirox, or VITA VM9. The crowns were cemented on their corresponding CoCr abutment. The initial fracture load was measured in one half of each group (n = 12), and the other half (n = 12) was subjected to chewing cycling. The data were analyzed using three-way and one-way ANOVA, a post-hoc Scheffé test, two sample Students t-test, and Weibull statistics (p < 0.05). Thus, nonaged, air-abraded groups of two veneering ceramics (Triceram, VITA VM9) showed higher mean fracture load compared to control groups. After chewing simulation, air-abraded groups showed lower mean fracture load compared to control groups. Aging decreased the Weibull modulus of all tested groups, and air-abraded groups showed lower Weibull moduli compared to control groups.

Für den Erfolg entscheidend: metallfreie zirkoniumdioxidbasierte Rekonstruktionen - Bearbeitungsschritte zum Erfolg

Metallfreie Rekonstruktionen setzten sich aufgrund der guten Asthetik, Biokompatibilitat und der guten mechanischen Eigenschaften immer starker durch. Zirkoniumdioxid als Gerustmaterial wird mittlerweile fast in jedem Labor bearbeitet. Leider wird immer haufiger festgestellt, dass dieses Material eine „Sonderbearbeitung“ benotigt und sich nicht wie die herkommlichen VMK-Rekonstruktionen lasst. In dem vorliegenden Beitrag werden die mechanischen Eigenschaften und die Verarbeitungsarten von Zirkoniumdioxidrekonstruktionen mit VMK-Versorgung gegenubergestellt und diskutiert.

Einfluss der künstlichen Alterung auf die Bruchlast konventionell oder mittels CAD/CAM hergestellter Brücken-Provisorien

Die CAD/CAM-Technologie bietet die Moglichkeit zur Konstruktion einer Restauration am Computer und die Fertigung der Restauration auf prazise gesteuerten vollautomatischen Fras- /Schleifmaschinen. Die Technologie hat sich bei Keramiken mittlerweile durchgesetzt. Nun kommen Kunststoffe auf den Markt, die mit geringerem Zeit- und Kostenaufwand mit dieser Technologie verarbeitet werden konnen. In einer vergleichenden Untersuchung wurde der Einfluss einer kunstlichen Alterung auf die Bruchlast von maschinell hergestellten provisorischen Kunststoff-Bruckengerusten derjenigen von formidentischen Eierschalenprovisorien und Direktprovisorien gegenubergestellt.