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with 2 different techniques, heat pressed IPS e.max Press 1 ingots and CAD/CAM milled IPS e.max CAD 1 blocks. Materials and methods: Two crown systems were selected for this study, a lost wax and heat pressure technique, IPS e.max Press, and a milled out of prefabricated blanks system using CAD/CAM technology, IPS e.max CAD.The study participants were 38. Preparations were performed by two operators. Abutments were prepared with smooth angles, and a chamfer finishing line was preferred. In Group 1 the crowns were fabricated using the heat pressed technique, while in Group 2 crowns were fabricated with CAD/CAM technology using prefabricated blocks milled with a CEREC 3 2 unit. The same luting strategy was employed for both groups. Modified USPHS Cements Curing time Contraction stress measured at criteria for evaluation of indirect restorations were used. A one-year survival rate analysis of the restorations was conducted according to the Kaplan–Meier method. Results: For the period of 12 months all the patients could be observed and all the parameters evaluated scored Alfa. No recurrent caries was reported at crown margins and all crowns showed marginal integrity, all the crowns were in place and in service, change of proximal contacts was not detected after the use of dental floss to test the resistance of the contact points. Conclusions: Within the limitation of this short time recall, clinically satisfactory performances were achieved in a 12month period of observation with both IPS e.max Press and IPS e.max CAD fabricated crowns. doi:10.1016/j.dental.2010.08.115 108 Contraction stress of two self-adhesive cements A. Frassetto, G. Marchesi, B. Codan, R. Di Lenarda, L. Breschi, M. Cadenaro University of Trieste, Trieste, Italy Objectives: Polymerization stress is an important side effect potentially leading to failure of the bonded interface. The aim of the study was to evaluate the contraction stress of two self-adhesive cements at different intervals after polymerization initiation. Materials and methods: Materials tested were: MaxCem Elite (Kerr, Orange, CA, USA) and Clearfil SA Cement (Kuraray, 1 Ivoclar Vivadent. 2 Sirona Dental Systems. dental materials 26S (2010) e1–e84 e51 Tokyo, Japan). Cements were dispensed between two stainless steel cylinders (h = 2 mm) fixed to a universal testing machine (Sun 500, Galdabini) then exposed to a LED-curing unit (Bluephase, Ivoclar Vivadent, 1200 mW/cm 2 ) for 20 or 40 s. The contraction force (N) generated during polymerization was continuously recorded for 6 h. Contraction stress (MPa) was calculated at 10 and 30 min, 1, 2, 5 and 6 h. Data were statistically analyzed by two-way ANOVA and Tukey’s post-hoc test (˛ = 0.05). Results: Means and standard deviations of contraction stress (expressed in MPa) at different time intervals for each of the two tested material. 10min 30min 1h 2h 5h 6h MaxCem Elite 20 s 1.8 ± 0.3 e 2.6 ± 0.1 f 3.1 ± 0.2 f,g,h 3.7 ± 0.3 i,j,k 4.0 ± 0.4 j,k 4.1 ± 0.4 j,k MaxCem Elite 40 s 2.7 ± 0.4 f,g 3.2 ± 0.4 g,h,i 3.6 ± 0.4 h,i,j 4.3 ± 0.3 k,l 4.8 ± 0.3 l 4.8 ± 0.3 l Clearfil SA Cement 20 s 0.5 ± 0.1 a 0.7 ± 0.1 a,b 0.8 ± 0.1 a,b,c 1.0 ± 0.1 a,b,c,d 1.2 ± 0.1 c,d 1.2 ± 0.1 b,c,d Clearfil SA Cement 40 s 1.0 ± 0.1 a,b,c,d 1.1 ± 0.0 b,c,d 1.2 ± 0.0 b,c,d 1.3 ± 0.1 c,d,e 1.3 ± 0.1 d,e 1.4 ± 0.1 d,e Means followed by the same superscript letters indicate no statistical difference at the 95% level of significance (p < 0.05). Conclusions: Clearfil SA Cement showed lower stress values than MaxCem Elite at each time interval. Irrespective from exposure time. Additional in vivo studies are needed to clarify the role of polymerization stress in the clinical performance of the self-adhesives cements. doi:10.1016/j.dental.2010.08.116 109 Influence of surface finishing on flexural strength of veneered zirconia J. Geis-Gerstorfer, C. Goldammer, C. Schille ∗ University Hospital Tuebingen, Germany Objectives: For all ceramic Y-TZP restorations, different veneering ceramics adjusted to the zirconia framework are available. The aim of this study was to compare the flexural strength of zirconia with three different veneering ceramics depending on the surface finishing conditions. Materials and methods: Y-TZP specimens (Zenotec Zr, 25 mm × 4mm× 1 mm, sandblasted with 110 �m Al2O3, 1 bar) were veneered with the veneering ceramics Zirox, Cercon Ceram Kiss and Vintage Zr according to manufacturer’s information (total sample thickness 2.5 mm). A liner firing, dentin firing (2×) and glaze firing were made. For each veneering ceramic four surface finishings were tested: (1) as fired, (2) grinding with a 46 �m diamond instrument, (3) polishing the grinded part, and (4) glazing again after grinding and polishing. From each surface and veneering ceramic 8 samples were tested. 3-point-bending tests according to ISO 6872 were performed using a universal testing machine (Z010, Zwick, Ulm) with a crosshead speed of 0.5 mm/min. During each measurement the acoustic signal of a microphone was recorded to get additional information about crack initiation. The statistical significance of the results was evaluated using t-test (p < 0.05).
e52 dental materials 26S (2010) e1–e84 Results: The results of the flexural strength values [MPa] for each veneering ceramic and surface condition (sandwich sample) can be seen in the table: Kind of surface finishing Zirox Cercon Ceram Kiss Vintage Zr As fired 141 ± 19 128 ± 28 92 ± 18 Grinded 91 ± 13 91 ± 8 83 ± 7 Grinded + polished 86 ± 10 98 ± 13 93 ± 8 Glazed after grinding + polishing 152 ± 18 158 ± 28 88 ± 8 With the exception of Vintage Zr the specimen with the glazed surface showed the highest flexural strength, even after grinding and glazing. The lowest strength was obtained by the grinded and polished surface, due to early fracture of the veneering. Conclusions: Polishing of grinded surfaces is not effective enough to eliminate surface defects and to regain sufficient strength. After grinding initial strength can only be achieved by an additional glazing process. Support: This study was supported by “Wieland Dental + Technik”, Pforzheim, Germany. doi:10.1016/j.dental.2010.08.117 110 Comparison of Elastomeric Impression Materials’ Thixotropic Behavior P. Gerasimou ∗ , K. Tolidis, C. Boutsiouki, D. Tortopidis Aristotle University of Thessaloniki, GR Objectives: The most common impression materials currently used in restorative dentistry are the vinylpolysiloxanes and polyethers. The purpose of this study was to compare the thixotropic behavior of seven elastomeric impression materials using a shark fin test, under applied low pressure. Materials and Methods: Five commercially available lowviscosity, automixed vinylipolysiloxanes (VPS), one polyether and a hybrid VPS-polyether were subjected to shark fin test under a load of 150gr, 30 s after mixing. The shark fin device was used to determine the fin height and the thixotropic behavior of each impression material. Five samples were made for each material. The data were analyzed using the ANOVA method. Means were compared with Tukey-Cramer test. Results: Comparison between shark fin height of Virtual and Affinis exhibited no significant difference (p > 0.05), as well as comparison between Honigum and Panasil (p > 0.05). Identium exhibited no significant differences when compared with Panasil or Honigum (p > 0.05) and Permadyne also exhibited no significant differences when compared to Virtual and Affinis (p > 0.05). Extremely significant differences were noted when Panasil was compared with Affinis or Permadyne, and when Affinis was compared with Identium (p < 0.001). Chromaclone showed significant differences in comparison with every other material (p < 0.001) exhibiting lower values, except for Panasil (p < 0.05). The material with the highest shark fin value was Affinis, followed by Permadyne, Virtual, Honigum, Identium, Panasil and Chromaclone. Panasil Virtual Chromaclone Affinis Honigum Identium Permadyne Mean (mm) 19.57 22.16 17.53 22.91 20.32 20.05 22.47 SD 0.86 1.55 0.35 0.98 0.62 0.59 0.93 Conclusions: The hybrid material’s thixotropic properties seem to be between VPS and PE thixotropicity values. Polyether shows high shark fin values as expected. The thixotropic behavior of the majority of VPS materials tested is acceptable. doi:10.1016/j.dental.2010.08.118 111 Resin bond strength to alumina coated dental oxide ceramics M. Golobič 1 , A. Kocjan 2 , T. Kosmač 2 , P. Jevnikar 1 1 University of Ljubljana, Ljubljana, Slovenia 2 Jozef Stefan Institute, Ljubljana, Slovenia Objectives: Surface functionalization of Y-TZP ceramics with a nano-structured alumina coating improves resin bond strength (Jevnikar et al. Dental Mater 2010;26:688). The aim of this study was to evaluate the shear-bond strength of the self-adhesive resin cement containing 4-META to as-prepared, sandblasted and alumina coated surfaces of yttria partially stabilized tetragonal zirconia (Y-TZP), alumina (Al2O3) and In-Ceram Zirconia (InZ) ceramics. Materials and methods: A total of 3 × 80 specimens were prepared. Densely sintered disc-shaped specimens (diameter 15 mm × height 2.5 mm) were produced from TZ-3YSB-E zirconia powder (Tosoh, Japan) and Reactive Alumina CT 3000 SDP powder (Almatis, Germany). InZ specimens (14 mm × 15 mm × 2 mm) were prepared from VITA In-Ceram ZIRCONIA for inLab ® (Vita, Germany) and infiltrated with Zirconia glass powder Z21N as recommended by the manufacturer. Specimens of each of the materials were randomly divided into two groups of 40 with different surface treatments: AS – as-prepared and APA – airborne-particle abraded (110 �m Al2O3, 4 bar, 15 s). Half of the specimens in each group received an alumina coating that was fabricated by exploiting the hydrolysis of aluminium nitride powder (groups AS-C, APA-C). The composite cylinders (diameter 4 mm × height 4 mm) were bonded to the ceramic specimens with G-Cem (GC, Japan). Shear-bond strength was then tested (Instron Corp., USA) for the coated and uncoated surfaces of the as-sintered and airborne-particle abraded specimens before and after thermocycling (5–55 ◦ C, 12,000×, 15 s). The adhesive surfaces were characterized using scanning electron microscopy (SEM). The data were analyzed by two-way ANOVA and the Tuckey post hoc test (SPSS). Results: The SEM analysis showed that the nano-structured alumina coating was successfully applied to as-prepared and sandblasted surfaces of Y-TZP, Al2O3 and InZ ceramics and a highly retentive surface for resin penetration was created. The shear-bond strength to the coated groups AS-C and APA-C of
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