Delaminacija i chipping obloţne keramike najĉešći su uzroci neuspjeha terapije cirkonij-oksidnim nadomjescima. Cilj je ovog istraţivanja provjeriti utjecaj raznih naĉina obrade površine cirkonij-oksidne keramike na veznu ĉvrstoću s obloţnom keramikom. U istraţivanju su korišteni blokovi Y-TZP IPS e.max ZirCAD (Ivoclar Vivadent AG, Schaan, Liechtenstein), koji su sinteriranjem dostigli dimenzije 10x10x10 mm koje su odgovarale istraţivanju. Ukupno dvadeset i ĉetiri bloka podijeljeno je u ĉetiri skupine koje su bile podvrgnute razliĉitim naĉinima obrade. Svi uzorci su nakon sinteriranja polirani dijamantnim brusnim sredstvima te oĉišćeni etanolom i vodenom parom. Druga skupina uzoraka dodatno je pjeskarena ĉesticama Al2O3. Na uzorke treće skupine, nakon pjeskarenja, napeĉeno je vezno sredstvo Zir liner (Ivoclar Vivadent). Uzorcima ĉetvrte skupine dodano je regeneracijsko peĉenje. Površine uzoraka snimljene su SEM-om. Hrapavost površine uzoraka izmjerena je profilometrom. Nakon obrade površine na uzorke je napeĉena obloţna keramika za slojevanje IPS e.max Ceram (Ivoclar Vivadent) dimenzija 10 x 5 x 2 mm. Vezna ĉvrstoća testirana je kidalicom. Dobiveni rezultati su obraĊeni slijedećim statistiĉkim analizama: deskriptivna statistiĉka analiza, one-way ANOVA te post-hoc testovi po Sheffeu u programu SPSS. Najveće vrijednosti vezne ĉvrstoće zabiljeţene su kod uzoraka 2. skupine, a najmanje prosjeĉne vrijednosti vezne ĉvrstoće zabiljeţene su kod uzoraka 4. skupine. Najveće srednje vrijednosti srednje hrapavosti površine (Ra) i najveće Z vrijednosti zabiljeţene su kod uzoraka 3. skupine. Veća hrapavost površine pospješuje veznu ĉvrstoću, dok ju primjena veznog sredstva oslabljuje.
Objectives: Delamination and chipping of veneering porcelain in zirconia FPDs are described as the most frequent failure reasons. The aim of the study was to assess the effect of different surface treatments on shear bond strength (SBS) of veneering ceramics to zirconia core. Materials and methods: Presintered Y-TZP IPS e.max ZirCAD blocks (Ivoclar Vivadent AG, Schaan, Lichtenstein) were used for this study. While sintering to full density in the Programat S1 furnace (Ivoclar Vivadent AG, Schaan, Lichtenstein) during 6 hours at the temperature of 1500C, the blocks gained dimensions of 10x10x10 mm needed for the study, so CAD/CAM grinding was not necessary. Total number of 24 zirconia core-veneer samples were divided in four groups and prepared according to the following procedures. All samples were ground under water spray cooling with a 90 m grit diamond bur in handpiece (Komet, Salzburg, Austria). Surface grinding was performed at maximum revolutions/min (200,000 rpm) and with minimal pressure to ensure a consistent grinding speed. The cubes were cleaned with 70% ethanol using cotton and pellets, and then they were steam cleaned during 10 seconds and air dried. The samples from the second group were ground and sandblasted (Renfert duo pro, GmbH, Hilzingen, Germany) with 110 m Al2O3 particles (Cobra; Renfert, GmbH, Hilzingen, Germany) at 2.5 bar pressure for a period of 5 seconds, steam-cleaned and air-dried. The third group samples were ground, sandblasted and a liner was additionally applied. Samples from the fourth group were ground, sandblasted, surface treated with the liner and regeneration fired (15 min/1000 C). All samples were submitted to SEM analysis (TESCAN VEGA TS. 5136LS, Tescan, Brno, Czech Republic). Measurement of surface roughness was performed using the Stylus instrument Perthometer S8P (Perthen, Mahr, Göttingen, Germany). After surface treatments the samples were veneered with e.max Ceram (Ivoclar Vivadent, Schaan, Liechtenstein) in dimensions of 10x5x2 mm. After the veneer porcelain was sintered to zirconia cubes, each sample was embedded in the customized polytetrafluoroethylene (PTFE) moulds using the PMMA resin AcryFix (Struers Co, Ballerup, Denmark) to allow shear bond testing. The samples were inserted in the holder of the universal testing machine (model LRX, Lloyd Instruments, Fareham, Great Britain) which had the same diameter as the above mentioned moulds, with the core-veneer interface positioned at the level of the jig. Shear force was applied as close as possible to the veneer-core interface at a crosshead speed of 1 mm/min until fracture occurred. Load deflection curves and ultimate load to failure were recorded automatically and displayed by the computer software of the testing machine (Nexygen, Lloyd Instruments, Fareham, Great Britain). Statistical analysis was performed using SPSS statistical package (version 17.0, SPSS Inc., Chicago, IL, USA). Results were analysed using one-way ANOVA and Scheffe`s post-hoc tests. Results: The highest shear bond strength values were recorded in the second group (ground and sandblasted samples) and the lowest in the fourth group (ground, sandblasted, treated with liner and regeneration fired samples). Highest mean roughnes (Ra) and Z values (the distance from the highest to the lowest point of measurement along the observed line) were recorded in the third group of samples which were ground, sandblasted and treated with liner. Conclusion: Surface roughness enhances the bond strenght between zirconia core and veneering ceramics while it is decreased by application of liner.